U.S. patent application number 14/883777 was filed with the patent office on 2016-02-04 for processes for treating fly ashes.
The applicant listed for this patent is ORBITE TECHNOLOGIES INC.. Invention is credited to Richard BOUDREAULT, Joel FOURNIER, Denis PRIMEAU.
Application Number | 20160032421 14/883777 |
Document ID | / |
Family ID | 49257993 |
Filed Date | 2016-02-04 |
United States Patent
Application |
20160032421 |
Kind Code |
A1 |
BOUDREAULT; Richard ; et
al. |
February 4, 2016 |
PROCESSES FOR TREATING FLY ASHES
Abstract
There are provided processes for treating fly ash. For example,
the processes can comprise leaching fly ash with HCl so as to
obtain a leachate comprising aluminum ions and a solid, and
separating the solid from the leachate; reacting the leachate with
HCl so as to obtain a liquid and a precipitate comprising the
aluminum ions in the form of AlCl.sub.3, and separating the
precipitate from the liquid; and heating the precipitate under
conditions effective for converting AlCl.sub.3 into Al.sub.2O.sub.3
and optionally recovering gaseous HCl so-produced.
Inventors: |
BOUDREAULT; Richard;
(St-Laurent, CA) ; FOURNIER; Joel; (Carignan,
CA) ; PRIMEAU; Denis; (Ste-Julie, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ORBITE TECHNOLOGIES INC. |
St-Laurent |
|
CA |
|
|
Family ID: |
49257993 |
Appl. No.: |
14/883777 |
Filed: |
October 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14388285 |
Sep 26, 2014 |
9181603 |
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PCT/CA2013/000218 |
Mar 11, 2013 |
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14883777 |
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61617422 |
Mar 29, 2012 |
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61706028 |
Sep 26, 2012 |
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Current U.S.
Class: |
423/21.1 ;
423/126; 423/140; 423/163; 423/197 |
Current CPC
Class: |
C22B 59/00 20130101;
Y02C 20/20 20130101; Y02P 10/212 20151101; A62D 2101/08 20130101;
C22B 21/0023 20130101; A62D 2203/02 20130101; C22B 26/10 20130101;
A62D 3/40 20130101; Y02W 30/50 20150501; Y02P 10/146 20151101; A62D
3/36 20130101; C01F 5/30 20130101; C22B 21/0007 20130101; Y02P
20/129 20151101; C01B 33/126 20130101; C01F 7/56 20130101; C22B
3/10 20130101; C01F 7/306 20130101; C22B 26/22 20130101; C01F 7/22
20130101; C01F 5/10 20130101; C01G 49/10 20130101; C01G 49/06
20130101; C01D 1/04 20130101; C22B 7/02 20130101; C01F 17/206
20200101; Y02P 10/20 20151101 |
International
Class: |
C22B 21/00 20060101
C22B021/00; C22B 26/10 20060101 C22B026/10; C22B 59/00 20060101
C22B059/00; C22B 3/10 20060101 C22B003/10; C22B 26/22 20060101
C22B026/22 |
Claims
1. A process for treating raw fly ash, said process comprising:
optionally a pre-leaching treatment that consists of reducing the
particle size of said raw fly ash; leaching said raw fly ash with
HCl under conditions effective to obtain a leachate comprising
aluminum ions and iron ions and a solid, and separating said solid
from said leachate; reacting said leachate with HCl so as to
increase concentration of HCl in said leachate under conditions
effective to decrease solubility of AlCl.sub.3 and to substantially
selectively precipitate aluminum ions, thereby obtaining a liquid
comprising iron ions and a precipitate comprising said aluminum
ions in the form of AlCl.sub.3, and separating said precipitate
from said liquid; and heating said precipitate under conditions
effective for converting AlCl.sub.3 into Al.sub.2O.sub.3 and
optionally recovering gaseous HCl so-produced.
2. The process of claim 1, wherein said fly ash is leached with HCl
having a concentration of about 25 to about 45 weight %.
3. The process of claim 1, wherein said fly ash is leached with HCl
having a concentration of about 25 to about 45 weight % at a
temperature of about 125 to about 225.degree. C.
4. The process of claim 1, wherein said fly ash is leached with HCl
having a concentration of about 25 to about 45 weight % at a
temperature of about 160 to about 190.degree. C.
5. The process of claim 1, wherein said liquid comprises at least
one iron chloride.
6. The process of claim 5, wherein said at least one iron chloride
is FeCl.sub.3.
7. The process of claim 6, wherein said liquid is concentrated to a
concentrated liquid having a concentration of said at least one
iron chloride of at least 30% by weight; and then hydrolyzed at a
temperature of about 155 to about 350.degree. C.
8. The process of claim 1, wherein said process comprises reacting
said leachate with gaseous HCl so as to obtain said liquid and said
precipitate comprising said aluminum ions, said precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
9. The process of claim 1, wherein said process comprises reacting
said leachate with dry gaseous HCl so as to obtain said liquid and
said precipitate comprising said aluminum ions, said precipitate
being formed by crystallization of AlCl.sub.3.6H.sub.2O.
10. The process of claim 1, wherein said process comprises reacting
said leachate with HCl recovered during said process and having a
concentration of at least 30% as to obtain said liquid and said
precipitate comprising said aluminum ions, said precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
11. The process of claim 1, wherein said process comprises
saturating said leachate with gaseous HCl having a concentration of
at least 85% by weight so as to obtain said liquid and said
precipitate comprising said aluminum ions, said precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
12. The process of claim 1, wherein said process comprises
saturating said leachate with dry gaseous HCl so as to obtain said
liquid and said precipitate comprising said aluminum ions, said
precipitate being formed by crystallization of
AlCl.sub.3.6H.sub.2O.
13. The process of claim 1, wherein said process comprises reacting
said leachate with HCl in a reactor so as to increase concentration
of free HCl in said reactor and to obtain said liquid and said
precipitate comprising said aluminum ions, said precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
14. The process of claim 13, wherein said process comprises
increasing concentration of free HCl in said reactor with gaseous
HCl.
15. The process of claim 14, wherein said gaseous HCl has a HCl
concentration of at least 85% by weight.
16. The process of claim 1, wherein said process comprises
converting AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying
out a calcination of AlCl.sub.3.6H.sub.2O.
17. The process of claim 1, wherein said process comprises
converting AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying
out a calcination of AlCl.sub.3.6H.sub.2O, said calcination
comprising steam injection.
18. A process for treating fly ash, said process comprising:
carrying out a pre-leaching removal of fluorine optionally
contained in said fly ash; leaching fly ash with HCl so as to
obtain a leachate comprising aluminum ions and iron ions and a
solid, and separating said solid from said leachate; reacting said
leachate with HCl so as to obtain a liquid comprising said iron
ions and a precipitate comprising said aluminum ions in the form of
AlCl.sub.3, and separating said precipitate from said liquid; and
heating said precipitate under conditions effective for converting
AlCl.sub.3 into Al.sub.2O.sub.3 and optionally recovering gaseous
HCl so-produced.
19. A process for treating fly ash, the process comprising:
leaching said fly ash comprising a first metal with HCl so as to
obtain a leachate comprising ions of said first metal and a solid,
and separating the solid from the leachate; reacting the leachate
with HCl so as to obtain a liquid and a precipitate comprising a
chloride of the first metal, and separating the precipitate from
the liquid; and heating the precipitate under conditions effective
for converting the chloride of the first metal into an oxide of the
first metal.
20. A process for treating fly ash comprising: leaching fly ash
with an acid so as to obtain a leachate and a solid residue, and
separating said leachate from said solid residue; at least
partially removing iron ions from said leachate by substantially
selectively precipitating said iron ions at a pH greater than 10 by
reacting said leachate with a base and at least partially removing
said precipitated iron ions from said leachate, thereby obtaining
an Al-rich composition comprising Al.sup.3+ ions; optionally
purifying said Al.sup.3+ ions; and converting said Al.sup.3+ ions
into alumina.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is Continuation of U.S. Ser. No.
14/388,285 filed on Sep. 26, 2014 that is a 35 USC 371 national
stage entry of PCT/CA2013/000218 filed on Mar. 11, 2013 and which
claims priority on U.S. 61/617,422 filed on Mar. 29, 2012; and on
U.S. 61/706,028 filed on Sep. 26, 2012. These documents are hereby
incorporated by reference in their entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to improvements in the field
of processes for treating industrial waste materials. For example,
it relates to processes for treating fly ash. For example, these
processes can be effective for extracting various materials from
fly ash such as alumina and various metal oxides, silica, and rare
earths, etc.
BACKGROUND OF THE DISCLOSURE
[0003] Fly ash is one of the residues generated in combustion. It
comprises fine particles that rise with the flue gases. Ash which
does not rise is termed bottom ash. Fly ash material can solidify
while suspended in the exhaust gases and is collected by
electrostatic precipitators or filter bags. Since the particles
solidify while suspended in the exhaust gases, fly ash particles
can be generally spherical in shape and range in size from 0.5
.mu.m to 100 .mu.m. Fly ash can comprise silicon dioxide
(SiO.sub.2) (which can be present in two forms: amorphous, which is
rounded and smooth, and crystalline, which is sharp, pointed and
hazardous); aluminium oxide (Al.sub.2O.sub.3) and iron oxide
(Fe.sub.2O.sub.3). Fly ashes can also comprise calcium oxide (CaO).
Fly ashes can also be highly heterogeneous. They can comprise a
mixture of glassy particles with various identifiable
components.
[0004] For example, fly ash can refer to ash produced during
combustion of coal. Depending upon the source and makeup of the
coal being burned, the components of fly ash vary considerably.
[0005] In the past, fly ash was generally released into the
atmosphere, but pollution control equipment mandated in recent
decades now require that it be captured prior to release. Fly ash
is generally captured by electrostatic precipitators or other
particle filtration equipment before the flue gases reach the
chimneys of coal-fired power plants, and together with bottom ash
removed from the bottom of the furnace is in this case jointly
known as coal ash. For example, in the US, fly ash can be generally
stored at coal power plants or placed in landfills. About 43
percent is recycled,.sup.[3] often used to supplement Portland
cement in concrete production. However, some scientists have
expressed health concerns about this.
[0006] In the past, fly ash produced from coal combustion was
simply entrained in flue gases and dispersed into the atmosphere.
This created environmental and health concerns that prompted laws
which have reduced fly ash emissions to less than 1 percent of ash
produced. Worldwide, more than 65% of fly ash produced from coal
power stations is disposed of in landfills and ash ponds. The
recycling of fly ash has become an increasing concern in recent
years due to increasing landfill costs and current interest in
sustainable development. As of 2005, U.S. coal-fired power plants
reported producing 71.1 million tons of fly ash, of which 29.1
million tons were reused in various applications. If the nearly 42
million tons of unused fly ash had been recycled, it would have
reduced the need for approximately 27,500 acreft (33,900,000
m.sup.3) of landfill space.
[0007] There is thus a need for at least an alternative process for
treating, recycling and/or valorizing fly ash.
SUMMARY OF THE DISCLOSURE
[0008] According to one aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0009] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0010] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0011] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and recovering gaseous HCl so-produced; and
[0012] recycling the gaseous HCl so-produced by contacting it with
water so as to obtain a composition having a concentration higher
than HCl azeotrope concentration (20.2 weight %) and reacting the
composition with a further quantity of aluminum-containing material
so as to leaching it.
[0013] According to another aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0014] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0015] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0016] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and recovering gaseous HCl so-produced; and
[0017] recycling the gaseous HCl so-produced by contacting it with
water so as to obtain a composition having a concentration of about
18 to about 45 weight % or about 25 to about 45 weight % and
reacting the composition with a further quantity of
aluminum-containing material so as to leaching it.
[0018] According to another aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0019] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0020] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0021] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and recovering gaseous HCl so-produced; and
[0022] recycling the gaseous HCl so-produced by contacting it with
water so as to obtain a composition having a concentration of about
18 to about 45 weight % or about 25 to about 45 weight % and using
the composition for leaching the aluminum-containing material.
[0023] According to another aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0024] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0025] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0026] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and recovering gaseous HCl so-produced; and
[0027] recycling the gaseous HCl so-produced by contacting it with
the leachate so as to precipitate the aluminum ions in the form of
AlCl.sub.3.6H.sub.2O.
[0028] According to another aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0029] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0030] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; and [0031] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3.
[0032] According to another aspect, there is provided a process for
preparing alumina and optionally other products, the process
comprising: [0033] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0034] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; and [0035] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and optionally recovering gaseous HCl
so-produced.
[0036] According to one aspect, there is provided a process for
preparing aluminum and optionally other products, the process
comprising: [0037] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0038] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0039] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3; and [0040] converting Al.sub.2O.sub.3 into
aluminum.
[0041] According to another aspect, there is provided a process for
preparing aluminum and optionally other products, the process
comprising: [0042] leaching an aluminum-containing material with
HCl so as to obtain a leachate comprising aluminum ions and a
solid, and separating the solid from the leachate; [0043] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising the aluminum ions in the form of AlCl.sub.3, and
separating the precipitate from the liquid; [0044] heating the
precipitate under conditions effective for converting AlCl.sub.3
into Al.sub.2O.sub.3 and optionally recovering gaseous HCl
so-produced; and [0045] converting Al.sub.2O.sub.3 into
aluminum.
[0046] According to another aspect, there is provided a process for
preparing various products, the process comprising: [0047] leaching
an aluminum-containing material comprising a first metal with HCl
so as to obtain a leachate comprising ions of the first metal and a
solid, and separating the solid from the leachate; [0048] reacting
the leachate with HCl so as to obtain a liquid and a precipitate
comprising a chloride of the first metal, and separating the
precipitate from the liquid; and [0049] heating the precipitate
under conditions effective for converting the chloride of the first
metal into an oxide of the first metal.
[0050] According to another aspect, there is provided a process for
preparing various products, the process comprising: [0051] leaching
an aluminum-containing material comprising a first metal with an
acid so as to obtain a leachate comprising ions of the first metal
and a solid, and separating the solid from the leachate; [0052]
substantially selectively removing ions of the first metal from the
leachate, thereby obtaining a composition; and substantially
selectively removing ions of a second metal from the
composition.
[0053] According to another aspect, there is a process for treating
an aluminum-containing material comprising: [0054] leaching fly ash
with an acid so as to obtain a leachate and a solid residue, and
separating the leachate from the solid residue; [0055] at least
partially removing iron ions from the leachate by substantially
selectively precipitating the iron ions at a pH greater than 10 by
reacting the leachate with a base and at least partially removing
the precipitated iron ions from the leachate, thereby obtaining an
Al-rich composition comprising Al.sup.3+ ions; [0056] optionally
purifying the Al.sup.3+ ions; and [0057] converting the Al.sup.3+
ions into alumina.
[0058] According to another aspect, there is a process for treating
an aluminum-containing material comprising: [0059] leaching the
aluminum-containing material with an acid so as to obtain a
leachate and a solid residue, and separating the leachate from the
solid residue; [0060] at least partially removing iron ions from
the leachate by substantially selectively precipitating the iron
ions at a pH of about 3 to about 6 by reacting the leachate with a
base and at least partially removing the precipitated iron ions
from the leachate, thereby obtaining an Al-rich composition
comprising Al.sup.3+ ions; [0061] optionally purifying the
Al.sup.3+ ions; and [0062] converting the Al.sup.3+ ions into
alumina.
BRIEF DESCRIPTION OF DRAWINGS
[0063] In the following drawings, which represent by way of example
only, various embodiments of the disclosure:
[0064] FIG. 1 shows a bloc diagram of an example of process for
preparing alumina and various other products according to the
present disclosure;
[0065] FIG. 2 is an extraction curve for Al and Fe in which the
extraction percentage is expressed as a function of a leaching time
in a process according to an example of the present
application;
[0066] FIG. 3 shows a bloc diagram of another example of process
for preparing alumina and various other products according to the
present disclosure;
[0067] FIG. 4 is a schematic representation of an example of a
process for purifying/concentrating HCl according to the present
disclosure;
[0068] FIG. 5 is a schematic representation of an example of a
process for purifying/concentrating HCl according to the present
disclosure;
[0069] FIG. 6 shows another bloc diagram of an example of process
for preparing alumina and various other products according to the
present disclosure; and
[0070] FIG. 7 shows another bloc diagram of an example of process
for preparing alumina and various other products according to the
present disclosure.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0071] The following non-limiting examples further illustrate the
technology described in the present disclosure.
[0072] The aluminum-containing material can be for example chosen
from aluminum-containing ores (such as aluminosillicate minerals,
clays, argillite, nepheline, mudstone, beryl, cryolite, garnet,
spinel, bauxite, kaolin or mixtures thereof can be used). The
aluminum-containing material can also be a recycled industrial
aluminum-containing material such as slag, red mud or fly ash.
[0073] The expression "red mud" as used herein refers, for example,
to an industrial waste product generated during the production of
alumina. For example, such a waste product can comprise silica,
aluminum, iron, calcium, and optionally titanium. It can also
comprise an array of minor constituents such as Na, K, Cr, V, Ni,
Ba, Cu, Mn, Pb, and/or Zn etc. For example, red mud can comprises
about 15 to about 80% by weight of Fe.sub.2O.sub.3, about 1 to
about 35% by weight Al.sub.2O.sub.3, about 1 to about 65% by weight
of SiO.sub.2, about 1 to about 20% by weight of Na.sub.2O, about 1
to about 20% by weight of CaO, and from 0 to about 35% by weight of
TiO.sub.2. According to another example, red mud can comprise about
30 to about 65% by weight of Fe.sub.2O.sub.3, about 10 to about 20%
by weight Al.sub.2O.sub.3, about 3 to about 50% by weight of
SiO.sub.2, about 2 to about 10% by weight of Na.sub.2O, about 2 to
about 8% by weight of CaO, and from 0 to about 25% by weight of
TiO.sub.2.
[0074] The expression "fly ashes" or "fly ash" as used herein
refers, for example, to an industrial waste product generated in
combustion. For example, such a waste product can contain various
elements such as silica, oxygen, aluminum, iron, calcium. For
example, fly ash can comprise silicon dioxide (SiO.sub.2) and
aluminium oxide (Al.sub.2O.sub.3). For example, fly ash can further
comprises calcium oxide (CaO) and/or iron oxide (Fe.sub.2O.sub.3).
For example fly ash can comprise fine particles that rise with flue
gases. For example, fly ash can be produced during combustion of
coal. For example, fly ash can also comprise at least one element
chosen from arsenic, beryllium, boron, cadmium, chromium, chromium
VI, cobalt, lead, manganese, mercury, molybdenum, selenium,
strontium, thallium, and/or vanadium. For example, fly ash can also
comprise rare earth elements and rare metals. For example, fly ash
can be considered as an aluminum-containing material. For example,
fly ash can comprise about 40 to about 50% by weight SiO.sub.2,
about 20 to about 30% by weight Al.sub.2O.sub.3, about 15 about 25%
by weight Fe.sub.2O.sub.3, about 1 to about 6% by weight Ca.sub.2O,
about 0 to about 2% by weight MgO, about 0 to about 2% Na.sub.2O
and about 1 to about 4% K.sub.2O
[0075] The expression "rare earth element" (also described as
"REE") as used herein refers, for example, to a rare element chosen
from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium,
promethium, samarium, europium, gadolinium, terbium, dysprosium,
holmium, erbium, thulium, ytterbium, and lutetium. The expression
"rare metals" as used herein refers, for example, to rare metals
chosen from indium, zirconium, lithium, and gallium. These rare
earth elements and rare metals can be in various form such as the
elemental form (or metallic form), under the form of chlorides,
oxides, hydroxides etc. The expression "rare earths" as used in the
present disclosure as a synonym of "rare earth elements and rare
metals" that is described above.
[0076] The expression "at least one iron chloride" as used herein
refers to FeCl.sub.2, FeCl.sub.3 or a mixture thereof.
[0077] The term "hematite" as used herein refers, for example, to a
compound comprising .alpha.-Fe.sub.2O.sub.3.
[0078] The expression "iron ions" as used herein refers, for
example to ions comprising to at least one type of iron ion chosen
from all possible forms of Fe ions. For example, the at least one
type of iron ion can be Fe.sup.2+, Fe.sup.3+, or a mixture
thereof.
[0079] The expression "aluminum ions" as used herein refers, for
example to ions comprising to at least one type of aluminum ion
chosen from all possible forms of Al ions. For example, the at
least one type of aluminum ion can be Al.sup.3+.
[0080] The expression "at least one aluminum ion", as used herein
refers, for example, to at least one type of aluminum ion chosen
from all possible forms of Al ions. For example, the at least one
aluminum ion can be Al.sup.3+.
[0081] The expression "at least one iron ion", as used herein
refers, for example, to at least one type of iron ion chosen from
all possible forms of Fe ions. For example, the at least one iron
ion can be Fe.sup.2+, Fe.sup.3+, or a mixture thereof.
[0082] The expression "at least one precipitated iron ion", as used
herein refers, for example, to at least one type of iron ion chosen
from all possible forms of Fe ions that was precipitated in a solid
form. For example, the at least one iron ion present in such a
precipitate can be Fe.sup.2+, Fe.sup.3+, or a mixture thereof.
[0083] Terms of degree such as "about" and "approximately" as used
herein mean a reasonable amount of deviation of the modified term
such that the end result is not significantly changed. These terms
of degree should be construed as including a deviation of at least
.+-.5% or at least .+-.10% of the modified term if this deviation
would not negate the meaning of the word it modifies.
[0084] For example, the material can be leached with HCl having a
concentration of about 10 to about 50 weight %, about 15 to about
45 weight %, of about 18 to about 45 weight % of about 18 to about
32 weight %, of about 20 to about 45 weight %, of about 25 to about
45 weight %, of about 26 to about 42 weight %, of about 28 to about
40 weight %, of about 30 to about 38 weight %, or between 25 and 36
weight %. For example, HCl at about 18 wt % or about 32 wt % can be
used.
[0085] Leaching can also be carried out by adding dry highly
concentrated acid (for example, 85%, 90% or 95%) in gas phase into
the aqueous solution. Alternatively, leaching can also be carried
out by using a weak acid solution (for example <3 wt %).
[0086] For example, leaching can be carried out by using HCl having
a concentration of about 18 to about 32 wt % in a first reactor and
then, by using HCl having concentration of about 90 to about 95%
(gaseous) in a second reactor.
[0087] For example, leaching can be carried out by using HCl having
a concentration of about 18 to about 32 wt % in a first reactor
then, by using HCl having concentration of about 90 to about 95%
(gaseous) in a second reactor; and by using HCl having
concentration of about 90 to about 95% (gaseous) in a third
reactor.
[0088] For example, leaching can be carried out under an inert gas
atmosphere (for example argon or nitrogen).
[0089] For example, leaching can be carried out under an atmosphere
of NH.sub.3.
[0090] For example, the material can be leached at a temperature of
about 125 to about 225.degree. C., about 150 to about 200.degree.
C., about 160 to about 190.degree. C., about 185 to about
190.degree. C., about 160 to about 180.degree. C., about 160 to
about 175.degree. C., or about 165 to about 170.degree. C.
[0091] For example, the material can be leached at a pressure of
about 4 to about 10 barg, about 4 to about 8 barg, or about 5 to
about 6 barg.
[0092] The leaching can be carried out under pressure (for example
greater than atmospheric pressure) into an autoclave. For example,
it can be carried out at a pressure of about 5 KPa to about 850
KPa, about 50 KPa to about 800 KPa, about 100 KPa to about 750 KPa,
about 150 KPa to about 700 KPa, about 200 KPa to about 600 KPa, or
about 250 KPa to about 500 KPa. The leaching can be carried out at
a temperature of at least 80.degree. C., at least 90.degree. C., or
about 100.degree. C. to about 110.degree. C. In certain cases, it
can be done at higher temperatures.
[0093] The leaching can also be carried out under pressure. For
example, the pressure can be about 100 to about 300 or about 150 to
about 200 psig. The leaching can be carried out for about 30
minutes to about 5 hours. It can be carried out at a temperature of
about 60.degree. C. to about 200.degree. C.
[0094] For example, the processes can further comprise recycling
the gaseous HCl so-produced by contacting it with water so as to
obtain a composition having a concentration of about 18 to about 45
weight % or 25 to about 45 weight %.
[0095] For example, the processes can further comprise recycling
the gaseous HCl so-produced by contacting it with water so as to
obtain a composition having a concentration of about 18 to about 45
weight %, about 26 to about 42 weight %, about 28 to about 40
weight %, about 30 to about 38 weight %, between 18 and 36 weight
%, between 19 and 36 weight %, between 25 and 36 weight % or about
25 to about 45 weight % and optionally using the composition for
leaching the material.
[0096] For example, the liquid can comprise iron chloride. Iron
chloride can comprise at least one of FeCl.sub.2, FeCl.sub.3, and a
mixture thereof.
[0097] For example, the liquid can have an iron chloride
concentration of at least 30% by weight; and can then be hydrolyzed
at a temperature of about 155 to about 350.degree. C.
[0098] For example, the liquid can be concentrated to a
concentrated liquid having an iron chloride concentration of at
least 30% by weight; and then the iron chloride can be hydrolyzed
at a temperature of about 155 to about 350.degree. C. while
maintaining a ferric chloride concentration at a level of at least
65% by weight, to generate a composition comprising a liquid and
precipitated hematite, and recovering the hematite.
[0099] For example, non-hydrolysable elements with hematite can be
concentrated back to a concentration of about 0.125 to about 52%
wt. in circulation loop in view of selective extraction.
[0100] For example, the liquid can be concentrated to a
concentrated liquid having a concentration of the at least one iron
chloride of at least 30% by weight; and then hydrolyzed at a
temperature of about 155 to about 350.degree. C.
[0101] For example, the liquid can be concentrated to a
concentrated liquid having a concentration of the at least one iron
chloride of at least 30% by weight; and then the at least one iron
chloride is hydrolyzed at a temperature of about 155 to about
350.degree. C. while maintaining a ferric chloride concentration at
a level of at least 65% by weight, to generate a composition
comprising a liquid and precipitated hematite, and recovering the
hematite.
[0102] For example, the liquid can be concentrated to a
concentrated liquid having a concentration of the at least one iron
chloride of at least 30% by weight; and then the at least one iron
chloride is hydrolyzed at a temperature of about 155 to about
350.degree. C. while maintaining a ferric chloride concentration at
a level of at least 65% by weight, to generate a composition
comprising a liquid and precipitated hematite; recovering the
hematite; and recovering rare earth elements and/or rare metals
from the liquid.
[0103] For example, the at least one iron chloride can be
hydrolyzed at a temperature of about, 150 to about 175, 155 to
about 170 or 165 to about 170.degree. C.
[0104] For example, the liquid can be concentrated to a
concentrated liquid having an iron chloride concentration of at
least 30% by weight; and then the iron chloride can be hydrolyzed
at a temperature of about 155 to about 350.degree. C. while
maintaining a ferric chloride concentration at a level of at least
65% by weight, to generate a composition comprising a liquid and
precipitated hematite; recovering the hematite; and recovering rare
earth elements and/or rare metals from the liquid.
[0105] For example, the processes can further comprise, after
recovery of the rare earth elements and/or rare metals, reacting
the liquid with HCl so as to cause precipitation of MgCl.sub.2, and
recovering same.
[0106] For example, the processes can further comprise calcining
MgCl.sub.2 into MgO and optionally recycling HCl so-produced.
[0107] For example, the processes can further comprises, after
recovery of the rare earth elements and/or rare metals, reacting
the liquid with HCl, and substantially selectively precipitating
Na.sub.2SO.sub.4. For example, Na.sub.2SO.sub.4 can be precipitated
by reacting the liquid with H.sub.2SO.sub.4.
[0108] For example, the processes can further comprises, after
recovery of the rare earth elements and/or rare metals, reacting
the liquid with HCl, and substantially selectively precipitating
K.sub.2SO.sub.4. For example, K.sub.2SO.sub.4 can be precipitated
by adding H.sub.2SO.sub.4.
[0109] For example, the liquid can be concentrated to a
concentrated liquid having an iron chloride concentration of at
least 30% by weight; and then the iron chloride can be hydrolyzed
at a temperature of about 155 to about 350.degree. C. while
maintaining a ferric chloride concentration at a level of at least
65% by weight, to generate a composition comprising a liquid and
precipitated hematite; recovering the hematite; and reacting the
liquid with HCl. For example, such processes can further comprises
reacting the liquid with H.sub.2SO.sub.4 so as to substantially
selectively precipitate Na.sub.2SO.sub.4. The processes can also
comprise further reacting the liquid with H.sub.2SO.sub.4 so as to
substantially selectively precipitating K.sub.2SO.sub.4.
[0110] For example, the processes can comprise reacting dry
individual salts (for example Na or K salts) obtained during the
processes with H.sub.2SO.sub.4 and recovering HCl while producing
marketable K.sub.2SO.sub.4 and Na.sub.2SO.sub.4 and recovering
hydrochloric acid of about 15 to about 90% wt.
[0111] For example, sodium chloride produced in the processes can
undergo a chemical reaction with sulfuric acid so as to obtain
sodium sulfate and regenerate hydrochloric acid. Potassium chloride
can undergo a chemical reaction with sulfuric acid so as to obtain
potassium sulfate and regenerate hydrochloric acid. Sodium and
potassium chloride brine solution can alternatively be the feed
material to adapted small chlor-alkali electrolysis cells. In this
latter case, common bases (NaOH and KOH) and bleach (NaOCl and
KOCl) are produced.
[0112] For example, the processes can further comprise, after
recovery of the rare earth elements and/or rare metals, recovering
NaCl from the liquid, reacting the NaCl with H.sub.2SO.sub.4, and
substantially selectively precipitating Na.sub.2SO.sub.4.
[0113] For example, the processes can further comprise, downstream
of recovery of the rare earth elements and/or rare metals,
recovering KCl from the liquid, reacting the KCl with
H.sub.2SO.sub.4, and substantially selectively precipitating
K.sub.2SO.sub.4.
[0114] For example, the processes can further comprise, downstream
of recovery of the rare earth elements and/or rare metals,
recovering NaCl from the liquid, carrying out an electrolysis to
generate NaOH and NaOCl.
[0115] For example, the processes can further comprise, downstream
of recovery of the rare earth elements and/or rare metals,
recovering KCl from the liquid, reacting the KCl, carrying out an
electrolysis to generate KOH and KOCl.
[0116] For example, the liquid can be concentrated to a
concentrated liquid having a concentration of the at least one iron
chloride of at least 30% by weight; and then the at least one iron
chloride is hydrolyzed at a temperature of about 155 to about
350.degree. C. while maintaining a ferric chloride concentration at
a level of at least 65% by weight, to generate a composition
comprising a liquid and precipitated hematite; recovering the
hematite; and extracting NaCl and/or KCl from the liquid.
[0117] For example, the processes can further comprise reacting the
NaCl with H.sub.2SO.sub.4 so as to substantially selectively
precipitate Na.sub.2SO.sub.4.
[0118] For example, the processes can further comprise reacting the
KCl with H.sub.2SO.sub.4 so as to substantially selectively
precipitate K.sub.2SO.sub.4.
[0119] For example, the processes can further comprise carrying out
an electrolysis of the NaCl to generate NaOH and NaOCl.
[0120] For example, the processes can further comprise carrying out
an electrolysis of the KCl to generate KOH and KOCl.
[0121] For example, the processes can comprise separating the solid
from the leachate and washing the solid so as to obtain silica
having a purity of at least 95%, at least 96%, at least 97%, at
least 98%, at least 99%, at least 99.5% or at least 99.9%.
[0122] For example, AlCl.sub.3 can be in the form of
AlCl.sub.3.6H.sub.2O.
[0123] For example, the processes can comprise reacting the
leachate with gaseous HCl so as to obtain the liquid and the
precipitate comprising the aluminum ions in the form of
AlCl.sub.3.6H.sub.2O.
[0124] For example, the processes can comprise reacting the
leachate with dry gaseous HCl so as to obtain the liquid and the
precipitate comprising the aluminum ions in the form of
AlCl.sub.3.6H.sub.2O.
[0125] For example, the processes can comprise reacting the
leachate with acid of at least 30% wt. that was recovered,
regenerated and/or purified as indicated in the present disclosure
so as to obtain the liquid and the precipitate comprising the
aluminum ions in the form of AlCl.sub.3.6H.sub.2O.
[0126] For example, the processes can comprise reacting the
leachate with gaseous HCl so as to obtain the liquid and the
precipitate comprising the aluminum ions, the precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
[0127] For example, the processes can comprise reacting the
leachate with dry gaseous HCl so as to obtain the liquid and the
precipitate comprising the aluminum ions, the precipitate being
formed by crystallization of AlCl.sub.3.6H.sub.2O.
[0128] For example, aluminum ions can be precipitated under the
form of AlCl.sub.3 (for example AlCl.sub.3.6H.sub.2O) in a
crystallizer, for example, by adding HCl having a concentration of
about 26 to about 32 wt % or about 24 to about 26% wt.
[0129] For example, the gaseous HCl can have a HCl concentration of
at least 85% wt. or at least 90% wt.
[0130] For example, the gaseous HCl can have a HCl concentration of
about 90% wt. or about 90% to about 95% wt.
[0131] For example, during the crystallization of
AlCl.sub.3.6H.sub.2O, the liquid can be maintained at a
concentration of HCl of about 25 to about 35% by weight, about 30
to about 32% by weight or about 23 to about 26% by weight.
[0132] For example, the crystallization can be carried out at a
temperature of about 45 to about 65.degree. C. or about 50 to about
60.degree. C.
[0133] For example, the HCl can be obtained from the gaseous HCl
so-produced.
[0134] For example, in the processes of the present disclosure, a
given batch or quantity of the aluminum-containing material will be
leached, will then be converted into AlCl.sub.3.6H.sub.2O and when
the HCl generated during calcination of AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 will be used for example to leach another given
batch or quantity of the aluminum-containing material.
[0135] For example, the processes can comprise heating the
precipitate at a temperature of at least 850, 900, 925, 930, 1000,
1100, 1200 or 1250.degree. C. for converting AlCl.sub.3.6H.sub.2O
into Al.sub.2O.sub.3.
[0136] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise calcination of AlCl.sub.3.
[0137] For example, calcination is effective for converting
AlCl.sub.3.6H.sub.2O into beta-Al.sub.2O.sub.3.
[0138] For example, calcination is effective for converting
AlCl.sub.3.6H.sub.2O into alpha-Al.sub.2O.sub.3.
[0139] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination via a
two-stage circulating fluid bed reactor or via a single stage
circulating fluid bed, or via any arrangement fluid bed, kiln, or a
plasma system.
[0140] For example, converting AlCl.sub.3 into Al.sub.2O.sub.3 can
comprise carrying out a calcination via a two-stage circulating
fluid bed reactor that comprises a preheating system.
[0141] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination at low
temperature, for example, of at least about 350.degree. C., at
least 375.degree. C. about 300 to about 600.degree. C., about 325
to about 550.degree. C., about 350 to about 500.degree. C., about
375 to about 450.degree. C., about 375 to about 425.degree. C., or
about 385 to about 400.degree. C. and/or injecting steam.
[0142] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination at low
temperature, for example, at least 350.degree. C. and/or injecting
steam.
[0143] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination at low
temperature, for example, less than 600.degree. C. and/or injecting
steam.
[0144] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination by using
coal as combustion source and by using a degasification unit.
[0145] For example, steam (or water vapor) can be injected at a
pressure of about 200 to about 700 psig, about 300 to about 700
psig, about 400 to about 700 psig, about 550 to about 650 psig,
about 575 to about 625 psig, or about 590 to about 610 psig.
[0146] For example, steam (or water vapor) can be injected and a
plasma torch can be used for carrying fluidization.
[0147] For example, the steam (or water vapor) can be
overheated.
[0148] For example, the steam (or water vapor) can be at a
temperature of about 300 to about 400.degree. C.
[0149] For example, acid from the offgases generated during
calcination can be then treated via a gas phase purification
process.
[0150] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination by means of
carbon monoxide (CO).
[0151] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a calcination by means of
a Refinery Fuel Gas (RFG).
[0152] For example, calcination can be carried out by injecting
water vapor or steam and/or by using a combustion source chosen
from fossil fuels, carbon monoxide, a Refinery Fuel Gas, coal, or
chlorinated gases and/or solvents.
[0153] For example, the processes can comprise converting
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying out a
calcination of AlCl.sub.3.6H.sub.2O that is provided by the
combustion of gas mixture that is a an incoming smelter gas or a
reducer offgas.
[0154] For example, the processes can comprise converting
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying out a
calcination of AlCl.sub.3.6H.sub.2O that is provided by the
combustion of gas mixture that is a an incoming smelter gas or a
reducer offgas.
[0155] For example, the processes can comprise converting
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying out a
calcination of AlCl.sub.3.6H.sub.2O that is provided by the
combustion of gas mixture that comprises:
[0156] CH.sub.4: 0 to about 1% vol;
[0157] C.sub.2H.sub.6: 0 to about 2% vol;
[0158] C.sub.3H.sub.8: 0 to about 2% vol;
[0159] C.sub.4H.sub.10: 0 to about 1% vol;
[0160] N.sub.2: 0 to about 0.5% vol;
[0161] H.sub.2: about 0.25 to about 15.1% vol;
[0162] CO: about 70 to about 82.5% vol; and
[0163] CO.sub.2: about 1.0 to about 3.5% vol.
[0164] For example, O.sub.2 can be substantially absent from the
mixture.
[0165] For example, calcination can be carried out by injecting
water vapor or steam and/or by using a combustion source chosen
from natural gas or propane.
[0166] For example, calcination can be carried out by providing
heat by means of electric heating, gas heating, microwave heating
and plasma heating.
[0167] The obtained alumina can be washed by demineralized water so
as to at least partially remove NaCl and/or KCl.
[0168] For example, the fluid bed reactor can comprise a metal
catalyst chosen from metal chlorides.
[0169] For example, thee fluid bed reactor can comprise a metal
catalyst that is FeCl.sub.3, FeCl.sub.2 or a mixture thereof.
[0170] For example, the fluid bed reactor can comprise a metal
catalyst that is FeCl.sub.3.
[0171] For example, the preheating system can comprise a plasma
torch.
[0172] For example, steam can be used as the fluidization medium
heating. Heating can also be electrical.
[0173] For example, a plasma torch can be used for preheating the
calcination reactor.
[0174] For example, a plasma torch can be used for preheating air
entering in the calcination reactor.
[0175] For example, a plasma torch can be used for preheating a
fluid bed.
[0176] For example, the plasma torch can be effective for
generating steam that is injected into a calcination reactor.
[0177] For example, the plasma torch can be effective for
generating steam that is as fluidization medium in a fluid bed
reactor.
[0178] For example, the calcination medium can be substantially
neutral in terms of O.sub.2 (or oxidation). For example, the
calcination medium can favorize reduction (for example a
concentration of CO of about 100 ppm).
[0179] For example, the calcination medium is effective for
preventing formation of Cl.sub.2.
[0180] For example, the processes can comprise converting
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying out a
calcination of AlCl.sub.3.6H.sub.2O that is provided by the
combustion of gas mixture that comprises:
[0181] CH.sub.4: 0 to about 1% vol;
[0182] C.sub.2H.sub.6: 0 to about 2% vol;
[0183] C.sub.3H.sub.8: 0 to about 2% vol;
[0184] C.sub.4H.sub.10: 0 to about 1% vol;
[0185] N.sub.2: 0 to about 0.5% vol;
[0186] H.sub.2: about 0.25 to about 15.1% vol;
[0187] CO: about 70 to about 82.5% vol; and
[0188] CO.sub.2: about 1.0 to about 3.5% vol.
[0189] Such a mixture can be efficient for reduction in off gas
volume of 15.3 to 16.3%; therefore the capacity increases of 15.3
to 16.3% proven on practical operation of the circulating fluid
bed. Thus for a same flow it represents an Opex of
0.65*16.3%=10.6%.
[0190] For example, the air to natural gas ratio of (Nm.sup.3/h
over Nm.sup.3/h) in the fluid bed can be about 9.5 to about 10
[0191] For example, the air to CO gas ratio of (Nm.sup.3/h over
Nm.sup.3/h) in the fluid bed can be about 2 to about 3.
[0192] For example, the processes can comprise, before leaching the
aluminum-containing material, a pre-leaching removal of fluorine
optionally contained in the aluminum-containing material.
[0193] For example, the processes can comprise leaching of the
aluminum-containing material with HCl so as to obtain the leachate
comprising aluminum ions and the solid, separating the solid from
the leachate; and further treating the solid so as to separate
SiO.sub.2 from TiO.sub.2 that are contained therein.
[0194] For example, the processes can comprise leaching the
aluminum-containing material with HCl so as to obtain the leachate
comprising aluminum ions and the solid, separating the solid from
the leachate; and further treating the solid with HCl so as to
separate Si from Ti that are contained therein.
[0195] For example, the processes can comprise leaching the
aluminum-containing material with HCl so as to obtain the leachate
comprising aluminum ions and the solid, separating the solid from
the leachate; and further treating the solid with HCl at a
concentration of less than 20% wt., at a temperature of less than
85.degree. C., in the presence of MgCl.sub.2, so as to separate Si
from Ti that are contained therein.
[0196] For example, the processes can comprise leaching said fly
ash with HCl so as to obtain the leachate comprising aluminum ions
and the solid, separating the solid from the leachate; and further
treating the solid so as to separate SiO.sub.2 from TiO.sub.2 that
are contained therein.
[0197] For example, the processes can comprise comprising leaching
the fly ash with HCl so as to obtain the leachate comprising
aluminum ions and the solid, separating the solid from the
leachate; and further treating the solid with HCl so as to separate
SiO.sub.2 from TiO.sub.2 that are contained therein.
[0198] For example, the processes can comprise leaching the fly ash
with HCl so as to obtain the leachate comprising aluminum ions and
the solid, separating the solid from the leachate; and further
treating the solid with HCl at a concentration of less than 20% by
weight, at a temperature of less than 85.degree. C., in the
presence of MgCl, so as to separate SiO.sub.2 from TiO.sub.2 that
are contained therein.
[0199] For example, converting AlCl.sub.3.6H.sub.2O into
Al.sub.2O.sub.3 can comprise carrying out a one-step
calcination.
[0200] For example, the processes can comprise converting
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 by carrying out a
calcination of AlCl.sub.3.6H.sub.2O, the calcination comprising
steam injection.
[0201] For example, calcination can be carried out at different
temperatures with steam. Temperature applied of superheated steam
can be of about 350.degree. C. to about 550.degree. C. or about
350.degree. C. to about 940.degree. C. or about 350.degree. C. to
about 1200.degree. C.
[0202] For example, multi stage evaporation step of the hydrolyser
can be carried out to reduce drastically energy consumption.
[0203] For example, the processes can be effective for providing an
Al.sub.2O.sub.3 recovery yield of at least 93%, at least 94%, at
least 95%, about 90 to about 95%, about 92 to about 95%, or about
93 to about 95%.
[0204] For example, the processes can be effective for providing a
Fe.sub.2O.sub.3 recovery yield of at least 98%, at least 99%, about
98 to about 99.5%, or about 98.5 to about 99.5%.
[0205] For example, the processes can be effective for providing a
MgO recovery yield of at least 96%, at least 97%, at least 98%, or
about 96 to about 98%.
[0206] For example, the processes can be effective for providing a
HCl recovery yield of at least 98%, at least 99%, about 98 to about
99.9% or about 98 to about 99.99%.
[0207] For example, the processes can be effective for providing
chlorides of rare earth elements (REE-Cl) and chlorides of rare
metals (RM-Cl) in recovery yields of about 75% to about 96.5% by
using internal processes via an internal concentration loop.
[0208] For example, the processes can be effective for providing
hydrochloric acid recovery yield of about 99.75% with
non-hydrolysable elements.
[0209] For example, the aluminum-containing material can be
argillite.
[0210] For example, the aluminum-containing material can be
bauxite.
[0211] For example, the aluminum-containing material can be red
mud.
[0212] For example, the aluminum-containing material can be fly
ash.
[0213] For example, the aluminum-containing material can be chosen
from industrial refractory materials.
[0214] For example, the aluminum-containing material chosen from
aluminosilicate minerals.
[0215] For example, the processes can be effective for avoiding
producing red mud.
[0216] For example, the alumina and the other products are
substantially free of red mud.
[0217] For example, HCl can be recycled. For example, such a
recycled HCl can be concentrated and/or purified.
[0218] For example, gaseous HCl can be concentrated and/or purified
by means of H.sub.2SO.sub.4. For example, gaseous HCl can be
treated with H.sub.2SO.sub.4 so as to reduce the amount of water
present in the gaseous HCl. For example, gaseous HCl can be passed
through a packed column where it is contacted with a
H.sub.2SO.sub.4 countercurrent flow. For example, by doing so,
concentration of HCl can be increased by at least 50% wt., at least
60% wt., at least 70% wt., at least 75% wt., at least 80% wt.,
about 50% wt. to about 80% wt., about 55% wt. to about 75% wt., or
about 60% wt. For example, the column can be packed with a polymer
such as polypropylene(PP) or polytrimethylene terephthalate
(PTT).
[0219] For example, gaseous HCl can be concentrated and/or purified
by means of CaCl.sub.2 or LiCl. For example, gaseous HCl can be
passed through a column packed with CaCl.sub.2 or LiCl.
[0220] For example, the concentration of gaseous HCl can be
increased from a value below the azeotropic point before treatment
to a value above the azeotropic point after treatment.
[0221] For example, the various products obtained by the processes
of the present disclosure such as alumina, hematite, titanium
oxides, magnesium oxides, rare earth elements and rare metals can
be further purified by means of a plasma torch. For example, the
rare earth elements and rare metals, once isolated, can be
individually injected into a plasma torch so as to further purify
them.
[0222] For example, the acid can be chosen from HCl, HNO.sub.3,
H.sub.2SO.sub.4 and mixtures thereof.
[0223] For example, the first metal can be aluminum or iron. For
example, the second metal can be aluminum or iron.
[0224] For example, when the first metal is aluminum, the aluminum
ions can be removed from said leachate by reacting the leachate
with an acid (such as HCl) so as to obtain a liquid and a
precipitate comprising said aluminum ions (for example in the form
of AlCl.sub.3), and separating said precipitate from said liquid.
Then, iron ions can be recovered from the liquid by precipitation,
hydrolysis, purification etc.
[0225] For example, when the first metal is iron, the iron ions can
be removed from said leachate by leachate with a base (such as NaOH
or KOH) so as to obtain a liquid and a precipitate comprising said
iron ions, and separating said precipitate from said liquid. Then,
aluminum ions can be recovered from the liquid by precipitation,
hydrolysis, purification etc.
[0226] For example, the processes can comprise precipitating said
Al.sup.3+ ions under the form of Al(OH).sub.3. For example, wherein
precipitating said Al.sup.3+ under the form of Al(OH).sub.3 is
carried out at a pH of about 7 to about 10, about 9 to about 10,
about 9.2 to about 9.8, about 9.3 to about 9.7, about 9.5, about
7.5 to about 8.5, about 7.8 to about 8.2 or about 8.
[0227] For example, the iron ions can be precipitated at a pH
greater than 11, a pH greater than 12, a pH comprised between 10
and 11, a pH of about 11.5 to about 12.5 or of about 11.8 to about
12.0.
[0228] For example, the iron ions can be precipitated at a pH of
about 3.0 to about 5.5, about 3 to about 5, about 3 to about 4,
about 3.0 to about 3.5, about 3.5 to about 4.0, about 4 to about 5,
about 4.5 to about 5.0, about 5 to about 6 by adding said base.
[0229] For example, when the first metal to be removed is iron, the
processes can be carried out in a manner similar as described in
WO2008/141423 or in WO2012/065253 and by using, for example, using
an aluminum-containing material as described in the present
disclosure as starting material. These document are hereby
integrated by reference in their entirety.
[0230] For example, the Al.sup.3+ ions can be purified.
[0231] For example, the processes can further comprise converting
alumina (Al.sub.2O.sub.3) into aluminum. Conversion of alumina into
aluminum can be carried out, for example, by using the Hall-Heroult
process. References is made to such a well known process in various
patents and patent applications such as US 20100065435; US
20020056650; U.S. Pat. No. 5,876,584; U.S. Pat. No. 6,565,733.
Conversion can also be carried out by means of other methods such
as those described in U.S. Pat. No. 7,867,373; U.S. Pat. No.
4,265,716; U.S. Pat. No. 6,565,733 (converting alumina into
aluminum sulfide followed by the conversion of aluminum sulfide
into aluminum.). For example, aluminium can be produced by using a
reduction environment and carbon at temperature below 200.degree.
C. Aluminum can also be produced by reduction using potassium and
anhydrous aluminum chloride (Wohler Process).
[0232] For example, converting AlCl.sub.3 into Al.sub.2O.sub.3 can
be done under an inert gas atmosphere.
[0233] For example, converting AlCl.sub.3 into Al.sub.2O.sub.3 can
be done under a nitrogen atmosphere.
[0234] For examples, the processes of the present disclosure can be
continuous processes or semi-continuous processes.
[0235] According to one example as shown in FIG. 1, the processes
can involve the following steps (the reference numbers in FIG. 1
correspond to the following steps):
[0236] 1--The aluminum-containing material is reduced to an average
particle size of about 50 to about 80 .mu.m.
[0237] 2--The reduced and classified material is treated with
hydrochloric acid which allows for dissolving, under a
predetermined temperature and pressure, the aluminum with other
elements like iron, magnesium and other metals including rare earth
elements and/or rare metals. The silica and titanium (if present in
raw material) remain totally undissolved.
[0238] 3--The mother liquor from the leaching step then undergoes a
separation, a cleaning stage in order to separate the purified
silica from the metal chloride in solution. The purified silica can
then optionally undergo one or two additional leaching stages (for
example at a temperature of about 150 to about 160.degree. C.) so
as to increase the purity of silica above 99.9%. TiO.sub.2
contained in silica can be separated from silica through a leach
made by using HCl and MgCl.sub.2 as a lixiviant composition.
[0239] 4--The spent acid (leachate) obtained from step 1 is then
brought up in concentration with dry and highly concentrated
gaseous hydrogen chloride by sparging this one into a crystallizer.
This results into the crystallization of aluminum chloride
hexahydrate (precipitate) with a minimum of other impurities.
Depending on the concentration of iron chloride at this stage,
further crystallization step(s) can be required. The precipitate is
then separated from the liquid.
[0240] 5--The aluminum chloride hexahydrate is then calcined (for
example by means of a rotary kiln, fluid bed, etc) at high
temperature in order to obtain the alumina form. Highly
concentrated gaseous hydrogen chloride is then recovered and excess
is brought in aqueous form to the highest concentration possible so
as to be used (recycled) in the acid leaching step. Acid can also
be directly sent in gas phase to the acid purification stage to
increase HCl concentration from about 30 wt % to about 95 wt %.
This can be done, for example, during drying stage.
[0241] 6--Iron chloride (the liquid obtained from step 4) is then
pre-concentrated and hydrolyzed at low temperature in view of the
Fe.sub.2O.sub.3 (hematite form) extraction and acid recovery from
its hydrolysis. All heat recovery from the calcination step (step
5), the leaching part exothermic reaction (step 1) and other
section of the processes is being recovered into the
pre-concentrator.
[0242] 10--After the removal of hematite, a solution rich in rare
earth elements and/or rare metals can be processed. As it can be
seen in FIG. 3, an internal recirculation can be done (after the
removal of hematite) and the solution rich in rare earth elements
and/or rare metals can be used for crystallization stage 4.
Extraction of the rare earth elements and/or rare metals can be
done as described in PCT/CA2012/000253 and/or PCT/CA2012000419.
These two documents are hereby integrated by reference in their
entirety.
[0243] Other non-hydrolysable metal chlorides (Me-Cl) such as
MgCl.sub.2 and others then undergo the following steps:
[0244] 7--The solution rich in magnesium chloride and other
non-hydrolysable products at low temperature is then brought up in
concentration with dry and highly concentrated gaseous hydrogen
chloride by sparging it into a crystallizer. This results into the
precipitation of magnesium chloride as an hexahydrate, for example
after sodium and potassium chloride removal.
[0245] 8--Magnesium chloride hexahydrate is then calcined (either
through a rotary kiln, fluid bed, etc.) and hydrochloric acid at
very high concentration is thus regenerated and brought back to the
leaching step.
[0246] 9--Other Me-Cl undergo a standard pyrohydrolysis step where
mixed oxides (Me-O) can be produced and hydrochloric acid at the
azeotropic point (20.2% wt.) is regenerated.
[0247] NaCl can undergo chemical reaction with H.sub.2SO.sub.4 to
produce Na.sub.2SO.sub.4 and HCl at a concentration at or above
azeotropic concentration. Moreover, KCl can undergo chemical
reaction with H.sub.2SO.sub.4 to produce K.sub.2SO.sub.4 and HCl
having a concentration that is above the azeotropic concentration.
Sodium and potassium chloride brine solution can be the feed
material to adapted small chlor-alkali electrolysis cells. In this
latter case, common bases (NaOH and KOH) and bleach (NaOCl and
KOCl) are produced as well as HCl.
[0248] For example, the liquid can be concentrated to a
concentrated liquid having an iron chloride concentration of at
least 30% by weight; and then the iron chloride can be hydrolyzed
at a temperature of about 155 to about 350.degree. C. while
maintaining a ferric chloride concentration at a level of at least
65% by weight, to generate a composition comprising a liquid and
precipitated hematite, and recovering the hematite.
[0249] For example, the liquid can be concentrated to a
concentrated liquid having an iron chloride concentration of at
least 30% by weight; and then the iron chloride can be hydrolyzed
at a temperature of about 155 to about 350.degree. C. while
maintaining a ferric chloride concentration at a level of at least
65% by weight, to generate a composition comprising a liquid and
precipitated hematite; recovering the hematite; and recovering rare
earth elements and/or rare metals from the liquid. For example, the
processes can further comprise, after recovery of the rare earth
elements and/or rare metals, reacting the liquid with HCl so as to
cause precipitation of MgCl.sub.2, and recovering same.
[0250] However, the person skilled in the art will understand that
the continuous processes can handle high percentages of silica
(>55%) and impurities as well as relatively low percentages of
aluminum (for example as low as about 15%) and still being
economically and technically viable. Satisfactory yields can be
obtained (>93-95%) on Al.sub.2O.sub.3 and greater than 75%, 85
or 90% on rare earth elements and/or rare metals. No pre-thermal
treatment in most cases are required. The processes disclosed in
the present disclosure involve special techniques on leaching and
acid recovery at very high strength, thereby offering several
advantages over alkaline processes.
[0251] In step 1 the mineral, whether or not thermally treated is
crushed, milled, dried and classified to have an average particle
size of about 50 to about 80 .mu.m.
[0252] In step 2, the milled raw material is introduced into the
reactor and will undergo the leaching phase.
[0253] The leaching hydrochloric acid used in step 2 can be a
recycled or regenerated acid from steps 5, 6, 8, 9, 10 and 11 (see
FIG. 3) its concentration can vary from 15% to 45% weight percent.
Higher concentration can be obtained using membrane separation,
cryogenic and/or high pressure approach. The acid leaching can be
carried out under pressure and at temperature close to its boiling
point thus, allowing a minimal digestion time and extended reaction
extent (90%-100%). Leaching (step 2) can be accomplished in a
semi-continuous mode where spent acid with residual free
hydrochloric acid is replaced, following pressurization, by highly
concentrated acid at a certain stage of the reaction or allowing a
reduced acid/mineral ratio, thereby reducing reaction time and
improving reaction kinetics. For example, kinetic constant k can
be: 0.5-0.75 g/moleL, or 0.65-0.82 g/moleL.
[0254] As previously indicated, alkali metals, iron, magnesium,
sodium, calcium, potassium, rare earth elements and other elements
will also be in a chloride form at different stages. Silica and
optionally titanium can remain undissolved and will undergo (step
3) a liquid/solid separation and cleaning stage. The processes of
the present disclosure tend to recover maximum amount of free
hydrochloric acid left and chlorides in solution in order to
maximize hydrochloric acid recovery yield, using techniques such as
rake classifying, filtration with band filters, centrifugation, and
others. Pure SiO.sub.2 (one additional leaching stage) cleaning
with nano water purity 99% min. Mother liquor free of silica is
then named as spent acid (various metal chlorides and water) and
goes to the crystallization step (step 4).
[0255] In step 4, the spent acid (or leachate) with a substantial
amount of aluminum chloride is then saturated with dry and highly
concentrated gaseous hydrogen chloride obtained or recycled from
step 5 or with aqueous HCl>30% wt., which results in the
precipitate of aluminum chloride hexahydrate
(AlCl.sub.3.6H.sub.2O). The precipitate retained is then washed and
filtered or centrifuged before being fed to the calcination stage
(step 5). The remaining of the spent acid from step 4 is then
processed to acid recovery system (steps 6 to 8) where pure
secondary products will be obtained.
[0256] In step 5, aluminum oxide (alumina) is directly obtained
from high temperature conditions. The highly concentrated hydrogen
chloride in gaseous form obtained can be fed to steps 4 and 7 for
crystallization where it can be treated through hydrophobic
membranes. The excess hydrogen chloride is absorbed and used as
regenerated acid to the leaching step 2 as highly concentrated
acid, higher than the concentration at the azeotropic point
(>20.2%). For example, such a concentration can be about 18 to
about 45 weight %, about 25 to about 45 weight % or between 25 and
36 weight %. Acid can also be redirected in gas phase directly
(>30 wt %) to acid purification.
[0257] After step 4, various chlorides derivatives (mainly iron
with magnesium and rare earth elements and rare metals) are next
subjected to an iron extraction step. Such a step can be carried
out for example by using the technology disclosed in WO
2009/153321, which is hereby incorporated by reference in its
entirety. Moreover, hematite can be seeded for crystal growth. For
example, hematite seeding can comprise recirculating the
seeding.
[0258] In step 6, a hydrolysis at low temperature (155-350.degree.
C.) is carried out and pure Fe.sub.2O.sub.3 (hematite) is being
produced and hydrochloric acid of at least 15% concentration is
being regenerated. The method as described in WO 2009/153321 is
processing the solution of ferrous chloride and ferric chloride,
possible mixtures thereof, and free hydrochloric acid through a
series of steps pre-concentration step, oxidation step where
ferrous chloride is oxidized into ferric form, and finally through
an hydrolysis step into an operational unit called hydrolyser where
the ferric chloride concentration is maintained at 65 weight % to
generate a rich gas stream where concentration ensures a hydrogen
chloride concentration of 15-20.2% and a pure hematite that will
undergo a physical separation step. Latent heat of condensation is
recovered to the pre-concentration and used as the heating input
with excess heat from the calcination stage (step 5).
[0259] The mother liquor from the hydrolyser (step 6) can be
recirculated partially to first step crystallization process where
an increase in concentration of non-hydrolysable elements is
observed. After iron removal, the liquor is rich in other
non-hydrolysable elements and mainly comprises magnesium chloride
or possible mixture of other elements (various chlorides) and rare
earth elements and rare metals.
[0260] Rare earth elements and rare metals in form of chlorides are
highly concentrated in percentage into the hydrolyser operational
unit (step 6) and are extracted from the mother liquor (step 10)
where various known techniques can be employed to extract a series
of individual RE-O (rare earth oxides). Among others, the processes
of the present disclosure allows to concentrate to high
concentration the following elements, within the hydrolyser:
scandium (Sc), galium (Ga), yttrium (Y), dysperosium (Dy), cerium
(Ce), praseodynium (Pr), neodynium (Nd), europium (Eu), lanthanum
(La), samarium (Sm), gadolinium, (Gd), erbium (Er), zirconium (Zr)
and mixtures of thereof. Technologies that can be used for
extracting rare earth elements and/or rare metals can be found, for
example, in Zhou et al. in RARE METALS, Vol. 27, No. 3, 2008, p
223-227, and in US 2004/0042945, hereby incorporated by reference
in their entirety. The person skilled in the art will also
understand that various other processes normally used for
extracting rare earth elements and/or rare metals from the Bayer
process can also be used. For example, various solvent extraction
techniques can be used. For certain elements, a technique involving
octylphenyl acid phosphate (OPAP) and toluene can be used. HCl can
be used as a stripping agent. This can be effective for recovering
Ce.sub.2O.sub.3, Sc.sub.2O.sub.3, Er.sub.2O.sub.3 etc. For example,
different sequence using oxalic acid and metallic iron for ferric
chloride separation can be used.
[0261] The spent acid liquor from steps 6 and 10 rich in value
added metals, mainly magnesium, is processed to step 7. The
solution is saturated with dry and highly concentrated gaseous
hydrogen chloride from step 5, which results in the precipitation
of magnesium chloride hexahydrate. For example, same can be
accomplished with HCl in aqueous form over 30% wt. The precipitate
retained, is fed to a calcination stage step 8 where pure MgO
(>98% wt.) is obtained and highly concentrated hydrochloric acid
(for example of at least 38%) is regenerated and diverted to the
leaching step (step 2). An alternative route for step 7 is using
dry gaseous hydrochloric acid from step 8.
[0262] In step 9, metal chlorides unconverted are processed to a
pyrohydrolysis step (700-900.degree. C.) to generate mixed oxides
and where hydrochloric acid from 15-20.2% wt. concentration can be
recovered.
[0263] According to another example as shown in FIG. 3, the
processes can be similar to the example shown in FIG. 1 but can
comprise some variants as below discussed.
[0264] In fact, as shown in FIG. 3, the processes can comprise
(after step 6 or just before step 10) an internal recirculation
back to the crystallization step 4. In such a case. The mother
liquor from the hydrolyser (step 6) can be recirculated fully or
partially to the crystallization of step 4 where a concentration
increase will occur with respect to the non-hydrolysable elements
including rare earth elements and/or rare metals.
[0265] Such a step can be useful for significantly increasing the
concentration of rare earth elements and/or rare metals, thereby
facilitating their extraction in step 10.
[0266] With respect to step 7, the solution rich in magnesium
chloride and other non-hydrolysable products at low temperature is,
as previously discussed, then brought up in concentration with dry
and highly concentrated gaseous hydrogen chloride by sparging it
into a crystallizer. This can result into the precipitation of
magnesium chloride as an hexahydrate (for example after sodium and
potassium chloride removal). This can also be accomplished with HCl
in aqueous form.
[0267] As shown in FIG. 3, an extra step 11 can be added. Sodium
chloride can undergo a chemical reaction with sulfuric acid so as
to obtain sodium sulfate and regenerate hydrochloric acid at a
concentration at or above the azeotropic point. Potassium chloride
can undergo a chemical reaction with sulfuric acid so as to obtain
potassium sulfate and regenerate hydrochloric acid at a
concentration above the azeotropic concentration. Sodium and
potassium chloride brine solution can be the feed material to
adapted small chlor-alkali electrolysis cells. In this latter case,
common bases (NaOH and KOH) and bleach (NaOCl and KOCl) are
produced and can be reused to some extent in other areas of the
processes of the present disclosure (scrubber, etc.).
[0268] The following are non-limitative examples.
Example 1
Preparation of Alumina and Various Other Products
[0269] As a starting material a sample of clay was obtained from
the Grande Vallee area in Quebec, Canada.
[0270] These results represent an average of 80 tests carried out
from samples of about 900 kg each.
[0271] Crude clay in the freshly mined state after grinding and
classification had the following composition:
Al.sub.2O.sub.3: 15%-26%;
SiO.sub.2: 45%-50%;
Fe.sub.2O.sub.3: 8%-9%;
MgO: 1%-2%;
[0272] Rare earth elements and/or rare metals: 0.04%-0.07%;
LOI: 5%-10%.
[0273] This material is thereafter leached in a two-stage procedure
at 140-170.degree. C. with 18-32 weight % HCl. The HCl solution was
used in a stoichiometric excess of 10-20% based on the
stoichiometric quantity required for the removal of the acid
leachable constituents of the clay. In the first leaching stage of
the semi-continuous operation (step 2), the clay was contacted for
2.5 hours with required amount or certain proportion of the total
amount of hydrochloric acid. After removal of the spent acid, the
clay was contacted again with a minimum 18 weight % hydrochloric
acid solution for about 1.5 hour at same temperature and
pressure.
[0274] A typical extraction curve obtained for both iron and
aluminum for a single stage leaching is shown in FIG. 2.
[0275] The leachate was filtered and the solid was washed with
water and analyzed using conventional analysis techniques (see step
3 of FIG. 1). Purity of obtained silica was of 95.4% and it was
free of any chlorides and of HCl.
[0276] In another example, the purity of the silica was 99.67%
through an extra leaching step.
[0277] After the leaching and silica removal, the concentration of
the various metal chlorides was:
AlCl.sub.3: 15-20%;
FeCl.sub.2: 4-6%;
FeCl.sub.3: 0.5-2.0%;
MgCl.sub.2: 0.5-2.0%;
REE-Cl: 0.1-2%
Free HCl: 5-50 g/l
[0278] Spent acid was then crystallized using about 90 to about 98%
pure dry hydrochloric acid in gas phase in two stages with less
than 25 ppm iron in the aluminum chloride hexahydrate formed. The
concentration of HCl in solution (aqueous phase) was about 22 to
about 32% or 25 to about 32%, allowing 95.3% of Al.sub.2O.sub.3
recovery. The recovered crystallized material (hydrate form of
AlCl.sub.3 having a minimum purity of 99.8%) was then calcined at
930.degree. C. or 1250.degree. C., thus obtaining the .alpha. form
of the alumina. Heating at 930.degree. C. allows for obtaining the
beta-form of alumina while heating at 1250.degree. C. allows for
obtaining the alpha-form.
[0279] Another example was carried out at low temperature
(decomposition and calcination at about 350.degree. C.) and the
.alpha. form of the alumina was less than 2%.
[0280] HCl concentration in gas phase exiting the calcination stage
was having a concentration greater than 30% and was used (recycled)
for crystallization of the AlCl.sub.3 and MgCl.sub.2. Excess of
hydrochloric acid is absorbed at the required and targeted
concentration for the leaching steps.
[0281] Iron chloride (about 90 to about 99.5%% in ferric form) is
then sent to a hydrothermal process in view of its extraction as
pure hematite (Fe.sub.2O.sub.3). This can be done by using the
technology described in WO 2009/153321 of low temperature
hydrolysis with full heat recovery from calcining, pyrohydrolysis
and leaching stage.
[0282] Rare earth elements and rare metals are extracted from the
mother liquor of the hydrolyzer where silica, aluminum, iron and a
great portion of water have been removed and following
preconcentration from hydrolyser to crystallization. It was
measured that rare earth elements can be concentrated by a factor
of about 4.0 to 10.0 on average within the hydrolyzer itself on a
single pass through it i.e. without concentration loop. The
following concentration factors have been noted within the
hydrolyzer (single pass): [0283] Ce>6 [0284] La>9 [0285]
Nd>7 [0286] Y>9
[0287] Remaining magnesium chloride is sparged with dry and highly
concentrated hydrochloric acid and then calcinated to MgO while
recovering high concentration acid (for example up to 38.4%).
[0288] Mixed oxides (Me-O) containing other non-hydrolysable
components were then undergoing a pyrohydrolysis reaction at
700-800.degree. C. and recovered acid (15-20.2% wt.) was rerouted
for example to the leaching system.
Overall Yields Obtained:
[0289] Al.sub.2O.sub.3: 93.0-95.03% recovery; Fe.sub.2O.sub.3:
92.65-99.5% recovery; Rare earth elements: 95% minimum recovery
(mixture); MgO: 92.64-98.00% recovery; Material discarded: 0-5%
maximum; HCl global recovery: 99.75% minimum; HCl strength as feed
to leaching 15-32% (aqueous); 95% (gas) Red mud production:
none.
Example 2
Preparation of Alumina and Various Other Products
[0290] A similar feed material (bauxite instead of clay) was
processed as per in example 1 up to the leaching stage and revealed
to be easily leachable under the conditions established in example
1. It provided an extraction percentage of 100% for the iron and
over 90-95% for aluminum. The technology was found to be
economically viable and no harmful by-products (red mud) were
generated. Samples tested had various concentrations of
Al.sub.2O.sub.3 (up to 51%), Fe.sub.2O.sub.3 (up to 27%) and MgO
(up to 1.5%). Gallium extraction of 97.0% was measured. Scandium
extraction was 95%.
Example 3
HCl Gas Enrichment and Purification: H.sub.2SO.sub.4 Route
[0291] H.sub.2SO.sub.4 can be used for carrying out purification of
HCl. It can be carried out by using a packing column with
H.sub.2SO.sub.4 flowing counter currently (see FIG. 4). This allows
for converting the recovered HCl into HCl having a concentration
above the azeotropic point (20.1% wt) and increase its
concentration by about 60 to about 70% at minimum.
[0292] Water is absorbed by H.sub.2SO.sub.4 and then
H.sub.2SO.sub.4 regeneration is applied where H.sub.2SO.sub.4 is
brought back to a concentration of about 95 to about 98% wt. Water
release at this stage free of sulphur is recycled back and used for
crystallization dissolution, etc. Packing of the column can
comprise polypropylene or polytrimethylene terephthalate (PTT).
[0293] Combustion energy can be performed with off gas preheating
air and oxygen enrichment. Oxygen enrichment: +2% represents flame
temperature increase by: 400.degree. C. maximum.
Example 4
HCl Gas Enrichment and Purification: Calcium Chloride to Calcium
Chloride Hexahydrate (Absorption/Desorption Process)
[0294] As shown in FIG. 5, CaCl.sub.2 can be used for drying HCl.
In fact, CaCl.sub.2 can be used for absorbing water contained into
HCl. In such a case, CaCl.sub.2 is converted into its hexachloride
form (CaCl.sub.2.6H.sub.2O) and one saturated system is eventually
switched into regeneration mode where hot air recovered from
calcination off gas of alumina and magnesium oxide spray roasting
is introduced to regenerate the fixed bed. Alternatively, other
absorbing agent such as LiCl can be used instead of CaCl.sub.2.
Such an ion/exchange type process can be seen in FIG. 4 and the
cycle can be inversed to switch from one column to another one.
[0295] The person skilled in the art would understand that the
processes described in examples 3 and 4 can be used in various
different manners. For example, these processes can be combined
with the various processes presented in the present disclosure. For
example, such purifications techniques can be integrated to the
processes shown in FIG. 1, 3 or 6. For example, these techniques
can be used downstream of at least one of step chosen from steps 5,
6, 8, 9, 10 and 11 (see FIGS. 1 and 3). They can also be used
downstream of step 4 and/or step 7. They can also be used
downstream of at least one of step chosen from steps 104 to 111
(see FIG. 6)
Example 5
Preparation of Alumina and Various Other Products
[0296] This example was carried out by using a process as
represented in FIGS. 6 and 7. It should be noted that the processes
represented in FIGS. 6 and 7 differ only by the fact that FIG. 7
show to additional stages i.e. stages 112 and 113.
Raw Material Preparation
[0297] Raw material, clay for example, was processed in a secondary
crusher in the clay preparation plant 101. Dry milling and
classifying occurs on a dry basis in vertical roller mills (for
example Fuller-Loesche LM 30.41). The clay preparation 101 included
three roller mills; two running at a capacity of approximately
160-180 tph and one on standby. Raw material, if required, can be
reduced to 85% less than 63 microns. Processed material was then
stored in homogenization silos before being fed to the acid
leaching plant 102. Below in Table 1 are shown results obtained
during stage 101. If the ore contains the fluorine element, a
special treatment can be applied before carrying out the 102 stage.
In presence of hydrochloric acid, fluorine can produce hydrofluoric
acid. This acid is extremely corrosive and damaging for human
health. Thus, before leaching 102, an optional treatment fluorine
separation 112 can be done. Stage 112 can comprise treating the
processed material coming from stage 101 with an acid in a
pre-leaching treatment so as to remove hydrofluoric acid.
Therefore, depending on the composition of the raw material, a
fluorine separation stage 112 (or pre-leaching stage 112) can be
carried out.
TABLE-US-00001 TABLE 1 Clay preparation Rate 290 tph Composition
feed SiO.sub.2: 50.9% (main constituents) Al.sub.2O.sub.3: 24.0%
Fe.sub.2O.sub.3: 8.51% CaO: 0.48% MgO: 1.33% Na.sub.2O: 1.06%
K.sub.2O: 2.86% MnO: 0.16% Cr.sub.2O.sub.3: 0.01% TiO.sub.2: 0.85%
P.sub.2O.sub.5: 0.145% SrO: 0.015% BaO: 0.05% V.sub.2O.sub.5
0.0321% Other (including H.sub.2O 9.63% and REE): Obtained particle
size 85% <63 .mu.m Residual moisture 0.5-0.7% Yield 99.5%
min
Acid Leaching
[0298] Next, acid leaching 102 was performed semi-continuously in
an 80 m.sup.3 glass-lined reactor. Semi-continuous mode comprises
replacing reacted acid 1/3 in the reaction period with higher
concentration regenerated acid, which greatly improves reaction
kinetics. The reactor arrangement comprises for example, a series
of three reactors.
[0299] Leaching was performed at high temperature and pressure
(about 160 to about 195.degree. C. and pressures of about 5 to
about 8 barg) for a fixed period of time. Reaction time was a
function of the reaction extent targeted (98% for Al.sub.2O.sub.3),
leaching mode, acid strength, and temperature/pressure applied.
[0300] Spent acid recovered out of the acid leaching 102 was then
filtered 103 from unreacted silica and titanium dioxide and washed
through an automated filter press where all free HCl and chloride
are recovered. This allows, for example, a maximum quantity of
about 30 ppm SiO.sub.2 going into spent liquor. Cleaned silica at a
concentration of .apprxeq.96%+SiO.sub.2 is then produced. Various
options are possible at that point. For example, the 96% silica can
undergo final neutralization through caustic bath, cleaning, and
then bricketing before storage. According to another example, the
silica purified by adding another leaching step followed by a solid
separation step that ensures TiO.sub.2 removal (see stage 113 in
FIG. 7). In that specific case, high purity silica 99.5%+ is
produced. In stage 113, titanium and silicium can be separated from
one another in various manners. For example, the solid obtained
from stage 103 can be leached in the presence of MgCl.sub.2 at a
temperature below 90 or 80.degree. C. and at low acid
concentration. For example, acid concentration can be below 25 or
20%. The acid can be HCl or H.sub.2SO.sub.4. In such a case,
titanium remains soluble after such a leaching while titanium is
still in a solid form. These solid and liquid obtained after stage
113 are thus separated to provide eventually TiO.sub.2 and
SiO.sub.2. Water input and flow for silica cleaning is in a ratio
of 1:1 (silica/water) (150 t/h SiO.sub.2 /150 t/h H.sub.2O), but
comprises of wash water circulation in closed loop in the process
and limited amount of process water for final cleaning of the
silica and recovery of all chlorides and free HCl generated at the
leaching stage. Below in Table 2 are shown results obtained during
stage 102.
TABLE-US-00002 TABLE 2 Acid Leaching Equivalent solid feed rate
259.6 tph Operation mode Semi-continuous Acid to clay ratio 3.10 @
23% wt (Equivalent to 3.35 with semi-continuous at 18.0% wt)
Regenerated acid 18.0-32.0% concentration Operating temperature
150-155.degree. C. (Pilot) 165-200.degree. C. (Plant) MAWP 120 psig
Typical chemical Fe.sub.2O.sub.3 + 6HCl .fwdarw. 2FeCl.sub.3 +
3H.sub.2O reactions Al.sub.2O.sub.3 + 6HCl .fwdarw. 2AlCl.sub.3 +
3H.sub.2O MgO + 2HCl .fwdarw. MgCl.sub.2 + H.sub.2O K.sub.2O + 2HCl
.fwdarw. 2KCl + H.sub.2O Re.sub.2O.sub.3 + 6HCl .fwdarw. 2
ReCl.sub.3 + 3H.sub.2O Spent acid flow to 600-1100 m.sup.3/h
crystallization Practical chemical FeCl.sub.3 4.33% composition
after step FeCl.sub.2 0.19% 102 without solid (SiO.sub.2)
AlCl.sub.3 16.6% MgCl.sub.2 0.82% NaCl 1.1% KCl 1.2% CaCl.sub.2
0.26% Extraction yields Iron 100% Al.sub.2O.sub.3 98% SiO.sub.2
Recovery 99.997%
AlCl.sub.3 Crystallization
[0301] Spent acid, with an aluminum chloride content of about 20 to
about 30%, was then processed in the crystallization stage 104. Dry
and highly concentrated HCl (>90% wt.) in gas phase was sparged
in a two-stage crystallization reactor, which allows the
crystallization of aluminum chloride hexahydrate.
[0302] The flow rate of acid through these reactors is about 600 to
about 675 m.sup.3/h and the reactor was maintained at about 50 to
about 60.degree. C. during this highly exothermic reaction. Heat
was recovered and exchanged to the acid purification 107 part of
the plant thus ensuring proper heat transfer and minimizing heat
consumption of the plant. Aluminum chloride solubility decreases
rapidly, compared to other elements, with the increase in
concentration of free HCl in the crystallization reactor. The
concentration of AlCl.sub.3 for precipitation/crystallization was
about 30%
[0303] The HCl concentration during crystallization was thus about
30 to about 32% wt.
[0304] The aqueous solution from the crystallization stage 104 was
then submitted to the hydrothermal acid recovery plant 105, while
the crystals are processed through the decomposition/calcination
stage in the calcination plant 106.
[0305] A one-step crystallization stage or a multi-step
crystallization stage can be done. For example, a two-steps
crystallization stage can be carried out.
[0306] Below in Tables 3A and 3B are shown results obtained during
stage 104.
TABLE-US-00003 TABLE 3A Aluminum chloride crystallization Number of
crystallization 2 steps Operating temperature 50-60.degree. C.
Sparging HCl concentration 90% (gaseous) Typical chemicals formed
AlCl.sub.3.cndot.6H.sub.2O (s) Metal chlorides (aq)
AlCl.sub.3.cndot.6H.sub.2O residual <5% (practical); 8%
TABLE-US-00004 TABLE 3B Typical crystals composition main
constituents obtained at pilot scale and feeding calcination
Component Weight distribution (%) AlCl.sub.3.cndot.6H.sub.2O 99.978
BaCl.sub.2.cndot.2H.sub.2O 0.0000 CaCl.sub.2.cndot.6H.sub.2O 0.0009
CrCl.sub.4 0.0022 CuCl.sub.2.cndot.2H.sub.2O 0.0000
FeCl.sub.3.cndot.6H.sub.2O 0.0019 KCl 0.0063
MgCl.sub.2.cndot.6H.sub.2O 0.0093 MnCl.sub.2.cndot.4H.sub.2O 0.0011
NaCl 0.0021 SiCl.sub.4 0.0004 SrCl.sub.2.cndot.6H.sub.2O 0.0000
TiCl.sub.4 0.0001 VCl.sub.4 0.0000 Free Cl.sup.- 0.0000
Calcination and Hydrothermal Acid Recovery
[0307] The calcination 106 comprises the use of a two-stage
circulating fluid bed (CFB) with preheating systems. The preheating
system can comprise a plasma torch to heat up steam to process. It
processes crystals in the decomposition/calcination stage. The
majority of the hydrochloric acid was released in the first stage
which was operated at a temperature of about 350.degree. C., while
the second stage performs the calcination itself. Acid from both
stages (about 66 to about 68% of the recovered acid from the
processes) was then recovered and sent to either to the acid
leaching 102 or to the acid purification 107. In the second
reactor, which was operated at a temperature of about 930.degree.
C., acid was recovered through the condensation and absorption into
two columns using mainly wash water from the acid leaching sector
102. Latent heat from this sector was recovered at the same time as
large amounts of water, which limits net water input.
[0308] In the iron oxides productions and acid recovery 105 system,
which comprises, aqueous solution from the crystallization 104
first undergoes a pre-concentration stage followed by processing in
the hydrolyzer reactor. Here, hematite was produced during low
temperature processing (about 165.degree. C.). A recirculation loop
was then taken from the hydrolyzer and is recirculated to the
pre-concentrator, allowing the concentration of REE, Mg, K, and
other elements. This recirculation loop, allows rare earth element
chlorides and/or rare metal chlorides and various metal chlorides
concentration to increase without having these products
precipitating with hematite up to a certain extent.
[0309] Depending on acid balance in the plant, recovered acid is
sent either directly to the 102 or 107 stage. Table 4 shows results
obtained in stage 105.
TABLE-US-00005 TABLE 4 Hydrothermal acid recovery Flowrate from
crystallization to 592 m.sup.3/h (design) HARP 600 m.sup.3/h
(design) Operating hydrolyser 155-170.degree. C. temperature
Regenerated acid concentration 27.4% Regenerated acid flowrate
205.2 tph HCl Hematite total production rate 24 TPH (design) HCl
recovery >99.8% Reflux (recirculation loop) rate in 56 tph
between hydrolyzer and pre- concentrator Rare earth element
chlorides .apprxeq.12.8 t/h and/or rare metal chlorides rate in
recirculation loop Hematite quality obtained and/or projected
Fe.sub.2O.sub.3 purity >99.5% Hydrolysable chlorides <0.2%
Moisture Max 20% after filtration PSD 25-35 microns Density (bulk)
2-3 kg/l Typical chemical reaction in stage 105 2FeCl.sub.3 +
3H.sub.2O .fwdarw. Fe.sub.2O.sub.3 + 6HCl 155-170.degree. C.
[0310] Table 5 shows results obtained in stage 106.
TABLE-US-00006 TABLE 5 Calcination Plant 106 Process
characteristics: Two-stage circulating fluid bed (CFB) with
pre-heating system Two-stage hydrochloric acid regeneration
Production rate (practical) About 66 tph CFB feed rate 371 tph
Typical chemical reaction occurring 2(AlCl.sub.3.cndot.6H.sub.2O) +
Energy .fwdarw. Al.sub.2O.sub.3 + 6HCl + 9H.sub.2O Typical alumina
chemical composition obtained from aluminum chloride hexahydrate
crystals being fed to calcination Component Weight distribution (%)
Al.sub.2O.sub.3 99.938 Fe.sub.2O.sub.3 0.0033 SiO.sub.2 0.0032
Cr.sub.2O.sub.3 0.0063 V.sub.2O.sub.5 0.0077 Na 0.0190 MgO 0.0090
P.sub.2O.sub.5 0.0039 K 0.0053 Ca 0.0020 MnO 0.0002 Free Cl.sup.-
Undetectable
Rare Earth Elements and Rare Metals Extractions
[0311] The stream that was taken out of 105 recirculation then was
treated for rare earth elements and are metals extraction 108, in
which the reduction of the remaining iron back to iron 2
(Fe.sup.2+), followed by a series of solvent extraction stages, was
performed. The reactants were oxalic acid, NaOH, DEHPA
(Di-(2-ethylhexyl)phosphoric acid) and TBP (tri-n-butyl phosphate)
organic solution, kerosene, and HCl were used to convert rare earth
element chlorides and rare metals chlorides to hydroxides.
Countercurrent organic solvent with stripping of solution using HCl
before proceeding to specific calcination from the rare earth
elements and rare metals in form of hydroxide and conversion to
high purity individual oxides. An ion exchange technique is also
capable of achieving same results as polytrimethylen terephtalate
(PET) membrane.
[0312] Iron powder from 105, or scrap metal as FeO, can be used at
a rate dependent on Fe.sup.3+ concentration in the mother liquor.
HCl (100% wt) at the rate of 1 tph can be required as the stripped
solution in REE Solvent Extraction (SX) separation and re-leaching
of rare earth elements and/or rare metals oxalates.
[0313] Water of very high quality, demineralized or nano, at the
rate of 100 tph was added to the strip solution and washing of
precipitates.
[0314] Oxalic acid as di-hydrate at a rate of 0.2 tph was added and
contributes to the rare earth elements and rare metals oxalates
precipitation. NaOH or MgOH at a rate of 0.5 tph can be used as a
neutralization agent.
[0315] DEHPA SX organic solution at the rate of 500 g/h was used as
active reagent in rare earth elements separation while TBP SX
organic solution at the rate of 5 kg/h is used as the active
reagent for gallium recovery and yttrium separation. Finally, a
kerosene diluent was used at the rate of approximately 2 kg/h in
all SX section. Calcination occurs in an electric rotary furnace
via indirect heating to convert contents to REE.sub.2O.sub.3
(oxides form) and maintain product purity.
[0316] Results of various tests made regarding stage 108 are shown
in Table 6.
[0317] One line divided in subsections (5) to isolate the following
elements using solvent extraction: [0318] Ga.sub.2O.sub.3 [0319]
Y.sub.2O.sub.3 [0320] Sc.sub.2O.sub.3 [0321]
Eu.sub.2O.sub.3+Er.sub.2O.sub.3+Dy.sub.2O.sub.3 [0322]
Ce.sub.2O.sub.3+Nd.sub.2O.sub.3+Pr.sub.2O.sub.3
TABLE-US-00007 [0322] Equivalent output earths oxides 166.14 kg/h
Projected production as per pilot testing results Incoming Final
extraction Feed (kg/h) individual (kg/h) Ga.sub.2O.sub.3 15.66
11.98 Sc.sub.2O.sub.3 9.06 8.11 Y.sub.2O.sub.3 22.56 20.22
La.sub.2O.sub.3 32.24 25.67 Ce.sub.2O.sub.3 61.37 51.82
Pr.sub.2O.sub.3 8.08 6.18 Nd.sub.2O.sub.3 30.3 27.24
Sm.sub.2O.sub.3 5.7 4.51 Eu.sub.2O.sub.3 1.06 0.95 Gd.sub.2O.sub.3
4.5 4.06 Dy.sub.2O.sub.3 3.9 3.55 Er.sub.2O.sub.3 2.1 1.86 Total
196.55 166.14
[0323] Global yield: 84.53%
[0324] Alternatively, stage 108 can be carried out as described in
PCT/CA2012/000253 and/or PCT/CA2012000419.
[0325] The solution after stages 108 and 109 contained mainly
MgCl.sub.2, NaCl, KCl, CaCl.sub.2, FeCl.sub.2/FeCl.sub.3, and
AlCl.sub.3 (traces), and then follows stage 111 Na, K, Ca that
follows the MgO can be extracted in stage 110 by crystallization in
a specific order; Na first, followed by K, and then Ca. This
technique can be employed for example in the Israeli Dead Sea salt
processing plant to produce MgO and remove alkali from the raw
material.
HCl Regeneration
[0326] Alkali (Na, K), once crystallized, was sent and processed in
the alkali hydrochloric acid regeneration plant 110 for recovering
highly concentrated hydrochloric acid (HCl). The process chosen for
the conversion can generate value-added products
[0327] Various options are available to convert NaCl and KCl with
intent of recovering HCl. One example can be to contact them with
highly concentrated sulfuric acid (H.sub.2SO.sub.4), which
generates sodium sulphate (Na.sub.2SO.sub.4) and potassium sulfate
(K.sub.2SO.sub.4), respectively, and regenerates HCl at a
concentration above 90% wt. Another example, is the use of a sodium
and potassium chloride brine solution as the feed material to
adapted small chlor-alkali electrolysis cells. In this latter case,
common bases (NaOH and KOH) and bleach (NaOCl and KOCl) are
produced. The electrolysis of both NaCl and KCl brine is done in
different cells where the current is adjusted to meet the required
chemical reaction. In both cases, it is a two-step process in which
the brine is submitted to high current and base (NaOH or KOH) is
produced with chlorine (Cl.sub.2) and hydrogen (H.sub.2). H.sub.2
and Cl.sub.2 are then submitted to a common flame where highly
concentrated acid in gas (100% wt.) phase is produced and can be
used directly in the crystallization stage 104, or to
crystallization stages requiring dry highly concentrated acid.
Magnesium Oxide
[0328] The reduced flow, which was substantially free of most
elements (for example AlCl.sub.3, FeCl.sub.3, REE-Cl, NaCl, KCl)
and rich in MgCl.sub.2, was then submitted to the magnesium oxides
plant 111. In the MgO, pyrohydrolysis of MgCl.sub.2 and any other
leftover impurities were converted into oxide while regenerating
acid. The first step was a pre-evaporator/crystallizer stage in
which calcium is removed and converted into gypsum
(CaSO.sub.4.2H.sub.2O) by a simple chemical reaction with sulfuric
acid, for which separation of MgO is required. This increases the
capacity of MgO roasting and also energy consumption slightly,
while substantially recovering HCl. The next step was the specific
pyrohydrolysis of MgO concentrated solution by spray roasting. Two
(2) main products were generated; MgO that was further treated and
HCl (about 18% wt.), which was either recycled back to the upstream
leaching stage 102 or to the hydrochloric acid purification plant
(107 The MgO-product derived from the spray roaster can require
further washing, purification, and finally calcining depending on
the quality targeted. The purification and calcining can comprise a
washing-hydration step and standard calcining step.
[0329] The MgO from the spray roaster is highly chemically active
and was directly charged into a water tank where it reacts with
water to form magnesium hydroxide, which has poor solubility in
water. The remaining traces of chlorides, like MgCl.sub.2, NaCl,
dissolved in water. The Mg(OH).sub.2 suspension, after settling in
a thickener, was forwarded to vacuum drum filters, which remove the
remaining water. The cleaned Mg(OH).sub.2 is then forwarded into a
calcination reactor where it is exposed to high temperatures in a
vertical multi-stage furnace. Water from hydration is released and
allows the transformation of the Mg(OH).sub.2 to MgO and water. At
this point, the magnesium oxide was of high purity (>99%).
HCl Purification
[0330] The hydrochloric acid purification stage 107 is effective
for purifying HCl regenerated from different sectors (for example
105, 106, 111) and to increase its purity for crystallization,
whereas dry highly concentrated acid (>90% wt.) can be used as
the sparging agent. Stage 107 also allowed for controlling the
concentration of the acid going back to stage 102 (about 22 to
about 32% wt.) and allows total acid and water balance. Total plant
water balance is performed mainly by reusing wash water as
absorption medium, as quench agent or as dissolution medium at the
crystallization stages
[0331] For example, purification can be carried out by means of a
membrane distillation process. The membrane distillation process
applied here occurs when two aqueous liquids with different
temperatures are separated through a hydrophobic membrane. The
driving force of the process was supplied by the partial pressure
vapour difference caused by the temperature gradient between these
solutions. Vapour travels from the warm to the cold side. Without
wishing to be bound to such a theory, the separation mechanism was
based on the vapour/liquid equilibrium of the HCl/water liquid
mixture. Practical application of such a technology has been
applied to HCl/water, H.sub.2SO.sub.4/water systems and also on
large commercial scales on aqueous solution of sodium chloride with
the purpose of obtaining potable water from seawater and nano water
production. Therefore membrane distillation was a separation
process based on evaporation through a porous hydrophobic membrane.
The process was performed at about 60.degree. C. and was effective
to recover heat from the 104 and 102 stage with an internal water
circulation loop, in order to maintain a constant incoming
temperature to the membranes. For example, eight membranes of
300,000 m.sup.2 equivalent surface area can be used per membrane to
obtain a concentration of HCl well above the azeotropic point (i.e.
>36%) of the .apprxeq.750 m.sup.3/h and final 90% concentration
is then obtained through pressure distillation (rectification
column).
[0332] Purification of HCl by processing thus regenerated acid
through hydrophobic membrane and separating water from HCl;
therefore increasing HCl concentration up to about 36% (above
azeotropic point) and therefore allowing with a single stage of
rectification through a pressure stripping column to obtain >90%
in gaseous phase, for crystallization stage (sparging); and
therefore controlling acid concentration into crystallization
stages up to 30-35%.sub.(aq).
[0333] As indicated stage 107 was operated at about 60.degree. C.
and heat input provided by heat recovery from stages 102 to 110.
Rectification column was operated at about 140.degree. C. in the
reboiler part. Net energy requirement was neutral (negative in fact
at -3.5 Gj/t Al.sub.2O.sub.3) since both systems were in
equilibrium and in balance.
[0334] For example, the acid purification can be carried out by
using adsorption technology over an activated alumina bed. In
continuous mode, at least two adsorption columns are required to
achieve either adsorption in one of them and regeneration in the
other one. Regeneration can be performed by feeding in
counter-current a hot or depressurized gas. This technology will
result in a purified gas at 100% wt.
[0335] For example, the acid purification can be made by using
calcium chloride as entrainer of water. A lean hydrochloric acid
solution is contacted with a strong calcium chloride solution
through a column. The water is then removed from the hydrochloric
acid solution and 99.9% gaseous HCl comes out of the process.
Cooling water and cryogenic coolant is used to condense water
traces in the HCl. The weak CaCl.sub.2 solution is concentrated by
an evaporator that ensures the recuperation of calcium chloride.
Depending on the impurities in the incoming HCl solution feed to
the column, some metals can contaminate the calcium chloride
concentrated solution. A precipitation with Ca(OH).sub.2 and a
filtration allows the removal of those impurities. The column can
operate for example at 0.5 barg. This technology can allow for the
recuperation of 98% of the HCl.
[0336] Table 7 shows the results obtained concerning the process
shown in FIG. 6.
TABLE-US-00008 Composition Stage 101 Stage 102 Stage 106 Stage 105
MgO Stage 107 Stage 108 TOTAL PRODUCED (% wt) Yield (%) Yield (%)
Yield (%) Yield (%) tpy Yield (%) Yield (%) Yield (%) Yield (%)
Main Constituents SiO.sub.2 -- 99.997% -- -- -- -- -- -- 99.997% Al
-- 98.02% 95.03% -- -- -- -- -- 95.03% Fe -- 100.00% -- 92.65% --
-- -- -- 92.65% Mg -- 99.998% -- -- 29.756 92.64% -- -- 92.64% Ca
-- 99.998% -- -- -- -- -- -- 98.28% Na -- 99.998% -- -- -- -- -- --
92.76% K -- 100.00% -- -- -- -- -- -- 93.97% Others incl. H.sub.2O
-- -- -- -- -- -- -- -- RE/RM -- 99.80% -- 92.32% -- -- -- 84.67%
84.67% By-Products NaOH -- -- -- -- 68.556 -- -- -- -- NaOCl -- --
-- -- 9.269 -- -- -- -- KOH -- -- -- -- 73.211 -- -- -- -- KOCl --
-- -- -- 9.586 -- -- -- -- CaSO.sub.4 -- -- -- -- 46.857 -- -- --
-- Reactants H.sub.4SO.sub.4(*) -- -- -- -- 19.204 -- -- -- --
Fresh HCl M-UP -- -- -- -- -- -- 99.75% -- 99.75% Total -- 98.55%
95.03% 256.419 92.64% 99.75% 84.67%
[0337] Tables 8 to 26 show results obtained concerning the products
made in accordance with the process shown in FIG. 6 in comparison
with standard of the industry.
TABLE-US-00009 TABLE 8 Chemical composition of obtained alumina
Standard used in Element % Weight industry Al.sub.2O.sub.3 99.938
98.35 min Fe.sub.2O.sub.3 0.0033 0.0100 SiO.sub.2 0.0032 0.0150
TiO.sub.2 0.0003 0.0030 V.sub.2O.sub.5 0.0008 0.0020 ZnO 0.0005
0.0030 Cr.sub.2O.sub.3 0.0003 N/A MgO 0.0090 N/A MnO 0.0002 N/A
P.sub.2O.sub.5 0.0039 0.0010 Cu 0.0030 N/A Ca 0.0020 0.0030 Na
0.0190 0.4000 K 0.0053 0.0150 Li 0.0009 N/A Ba <0.00001 0.0000
Th <0.000001 0.0000 U <0.000001 0.0000 Free Cl.sup.- Not
detectable 0.0000 LOI <1.0000 <1.0000
TABLE-US-00010 TABLE 9 Physical properties of obtained alumina
Standard used in Property Orbite Alumina industry PSD < 20 .mu.m
5-10% N/A PSD < 45 .mu.m 10-12% <10% PSD > 75 .mu.m 50-60%
N/A SSA (m.sup.2/g) 60-85 60-80 Att. Index 10-12% <10% .alpha.
Al.sub.2O.sub.3 2-5% <7-9%
TABLE-US-00011 TABLE 10 Chemical composition of obtained hematite
Element % Weight Fe.sub.2O.sub.3 >99.5% Hydrolysable elements
<0.2%
TABLE-US-00012 TABLE 11 Physical properties of obtained hematite*
Property Orbite hematite PSD.sub.mean 25-35 .mu.m Density (bulk)
2000-3000 kg/m.sup.3 Humidity after filtration <10% *Material
can be produced as brickets
TABLE-US-00013 TABLE 12 Chemical composition of obtained silica
Element % Weight SiO.sub.2 >99.7 Al.sub.2O.sub.3 <0.25% MgO
.apprxeq.0.1% Fe.sub.2O.sub.3 .apprxeq.0.1% CaO .apprxeq.0.01%
Na.sub.2O <0.1% K.sub.2O <0.1% Note: Product may have
unbleached cellulose fiber filter aid. Cellulose wood flour.
TABLE-US-00014 TABLE 13 Physical properties of obtained silica
Property Orbite silica PSD.sub.mean 10-20 .mu.m Specific surface
area 34 m.sup.2/g Density (bulk) 2000-2500 kg/m.sup.3 Humidity
after filtration <40%
TABLE-US-00015 TABLE 14 Purity of obtained rare earth element
oxides Element Purity (%) Ga.sub.2O.sub.3 >99% Sc.sub.2O.sub.3
Y.sub.2O.sub.3 La.sub.2O.sub.3 Ce.sub.2O.sub.3 Pr.sub.2O.sub.3
Nd.sub.2O.sub.3 Sm.sub.2O.sub.3 Eu.sub.2O.sub.3 Gd.sub.2O.sub.3
Dy.sub.2O.sub.3 Er.sub.2O.sub.3 Physical properties of obtained
REE-O/RM-O Property Orbite REE-O/RM-O PSD.sub.mean 2-30 .mu.m
Density 5500-13000 kg/m.sup.3 LOI <1%
TABLE-US-00016 TABLE 15 Chemical composition of obtained MgO
Element Typical Specification MgO 99.0.sup.+ 98.35 min CaO 0.0020
0.83 SiO.sub.2 0.0000 0.20 max B.sub.2O.sub.3 0.0000 0.02 max
Al.sub.2O.sub.3 0.0300 0.12 max Fe.sub.2O.sub.3 0.0160 0.57 max
MnO.sub.2 <0.14 0.14 max LOI 0.7% <1%
TABLE-US-00017 TABLE 16 Physical properties of obtained MgO
Property Orbite MgO PSD.sub.mean 10 .mu.m Density N/A LOI 650
kg/m.sup.3
TABLE-US-00018 TABLE 17 Chemical composition of obtained NaOH
Element % Weight Sodium hydroxide 32% Water 68%
TABLE-US-00019 TABLE 18 Physical properties of obtained NaOH
Property Sodium hydroxide (NaOH) Physical state Liquid Vapour
pressure 14 mmHg Viscosity >1 Boiling point 100.degree. C.
Melting point 0.degree. C. Specific gravity 1.0
TABLE-US-00020 TABLE 19 Chemical composition of obtained sodium
hypochlorite (bleach) Element % Weight Sodium hypochlorite 12%
Sodium hydroxide <1% Water >80%
TABLE-US-00021 TABLE 20 Physical properties of obtained NaOCl
Property Sodium hypochlorite (NaOCl) Physical state Liquid Vapour
pressure 1.6 kPa Viscosity N/A Boiling point 100.degree. C. Melting
point -3.degree. C. Specific gravity 1.2
TABLE-US-00022 TABLE 21 Chemical composition of obtained potassium
hydroxide Element % Weight Potassium hydroxide 32% Water 68%
TABLE-US-00023 TABLE 22 Physical properties of obtained potassium
hydroxide Property KOH Physical state Liquid Vapour pressure 17.5
mmHg Viscosity N/A Boiling point 100.degree. C. Melting point N/A
Specific gravity 1.18
TABLE-US-00024 TABLE 23 Chemical composition of obtained potassium
hypochlorite (KOCl) Element % Weight Potassium hypochlorite 12%
Potassium hydroxide <1% Water >80%
TABLE-US-00025 TABLE 24 Physical properties of obtained potassium
hypochlorite Property KOCl Physical state Liquid Vapour pressure
N/A Viscosity N/A Boiling point 103.degree. C. Melting point N/A
Specific gravity >1.0
TABLE-US-00026 TABLE 25 Chemical composition of obtained calcium
sulphate dihydrate Element % Weight Calcium sulphate 100%
dihydrate
TABLE-US-00027 TABLE 26 Physical properties of obtained calcium
sulphate dihydrate Property Orbite CaSO.sub.4.cndot.2H.sub.2O
Physical state Solid Specific gravity 2.32
[0338] In order to demonstrate the versatility of the processes of
the present disclosure, several other tests have been made so as to
shown that these processes can be applied to various sources of
starting material.
Example 6
[0339] Another starting material has been used for preparing acidic
compositions comprising various components. In fact, a material
that is a concentrate of rare earth elements and rare metals
(particularly rich in zirconium) has been tested. Table 27 shows
the results of the leaching carried out on such a starting material
using a similar process as shown in FIGS. 1, 3, 6 and 7 and as
detailed in Examples 1, 2 and 5. It can thus be inferred from the
results shown in Table 27 that the various components present in
the leaching (various metals such as aluminum, iron, magnesium as
well as rare earth elements and rare metals) can be extracted from
the obtained leaching composition and that they can eventually be
isolated by the processes of the present disclosure such as, for
example, those presented in Examples 1, 2 and 5.
Example 7
[0340] Other tests have been made in a similar manner as described
in Example 6. In the present example, carbonatite has been used as
a starting material. (see Table 28 below).
TABLE-US-00028 TABLE 27 Tests made on a zirconium rich material.
Composition Average Extraction rate .smallcircle. All Orbite
measure and/or measured for measured (ALP) process Raw material
evaluated (% wt.) testing (% wt.) (%) recovery (%) Al.sub.2O.sub.3
6.12 6.12 89.65 86.97 Fe.sub.2O.sub.3 15.80 15.80 99.50 97.51
SiO.sub.2 36.00 36.00 0.000 99.997 MgO 3.08 3.08 99.75 92.66
Na.sub.2O 1.13 1.13 99.50 99.50 K.sub.2O 2.12 2.12 99.50 99.50 CaO
6.10 6.10 99.50 99.00 S total 0.22 0.22 100.00 F 1.98 1.98 99.50
99.00 TiO.sub.2 0.13 0.13 0.000 99.03 V.sub.2O.sub.5 0.00 0.00
98.00 96.04 P.sub.2O.sub.5 1.10 1.10 98.00 96.04 MnO 0.43 0.43
98.00 96.04 ZrO.sub.2 12.43 12.43 22.70 20.43 Cr.sub.2O.sub.3 0.00
0.00 0.00 0.00 Ce.sub.2O.sub.3 3.05 3.045 97.31 92.98
La.sub.2O.sub.3 1.34 1.337 99.55 92.68 Nd.sub.2O.sub.3 1.55 1.551
98.40 94.79 Pr.sub.2O.sub.3 0.37 0.375 99.75 97.52 Sm.sub.2O.sub.3
0.15 0.151 88.75 84.80 Dy.sub.2O.sub.3 0.09 0.089 80.35 76.77
Er.sub.2O.sub.3 0.03 0.030 72.60 69.37 Eu.sub.2O.sub.3 0.03 0.027
85.57 81.76 Gd.sub.2O.sub.3 0.21 0.205 82.85 79.16 Ho.sub.2O.sub.3
0.01 0.013 77.10 73.67 Lu.sub.2O.sub.3 0.00 0.003 60.15 57.47
Tb.sub.2O.sub.3 0.02 0.022 78.05 74.58 Th 0.02 0.022 88.10 84.18
Tm.sub.2O.sub.3 0.00 0.004 66.85 63.88 U 0.01 0.014 81.90 78.26
Y.sub.2O.sub.3 0.30 0.300 72.70 69.46 Yb.sub.2O.sub.3 0.02 0.023
62.80 60.01 Ga.sub.2O.sub.3 0.02 0.016 96.90 92.59 Sc.sub.2O.sub.3
0.00 0.003 95.00 90.77 LOI (inc. water) 6.122023973 6.12
TABLE-US-00029 TABLE 28 Tests made on carbonatite Composition
Average Extraction rate .smallcircle. All Orbite measure and/or
measured for measured (ALP) process Raw material evaluated (% wt.)
testing (% wt.) (%) recovery (%) Al.sub.2O.sub.3 0.70 0.70 84.31
81.61 Fe.sub.2O.sub.3 11.22 11.22 94.14 92.15 SiO.sub.2 2.11 2.11
0.00003 99.997 MgO 6.50 6.500 100 96.25 Na.sub.2O 0.07 0.07 92.54
90.55 K.sub.2O 0.18 0.181 37.33 37.33 CaO 16.51 16.51 100 98.00
TiO.sub.2 0.00 0.000 0.00000 100.000 V.sub.2O.sub.5 0.00 0.000 0
100.000 P.sub.2O.sub.5 0.00 0.000 0 100.000 MnO 0.00 0.000 0
100.000 ZrO.sub.2 0.00 0.000 0 100.000 Cr.sub.2O.sub.3 0.00 0.000 0
100.000 Ce.sub.2O.sub.3 1.19 1.195 64.04 61.190 La.sub.2O.sub.3
0.46 0.463 63.86 61.018 Nd.sub.2O.sub.3 0.45 0.448 81.46 77.835
Pr.sub.2O.sub.3 0.14 0.142 67.59 64.582 Sm.sub.2O.sub.3 0.03 0.033
65.32 62.413 Dy.sub.2O.sub.3 0.00 0.000 78.12 74.644
Er.sub.2O.sub.3 0.00 0.000 86.15 82.316 Eu.sub.2O.sub.3 0.01 0.007
66.45 63.493 Gd.sub.2O.sub.3 0.01 0.013 54.46 52.037
Ho.sub.2O.sub.3 0.00 0.000 83.12 79.421 Lu.sub.2O.sub.3 0.00 0.000
88.86 84.906 Tb.sub.2O.sub.3 0.00 0.001 41.42 39.577 Th 0.06 0.065
Tm.sub.2O.sub.3 0.00 0.000 90.70 86.664 U 0.01 0.007 Y.sub.2O.sub.3
0.00 0.000 84.68 80.912 Yb.sub.2O.sub.3 0.00 0.000 85.11 81.323
Ga.sub.2O.sub.3 0.00 0.000 0 0.000 Sc.sub.2O.sub.3 0.00 0.000 0
0.000 LOI (inc. water) 60.33
[0341] It can thus be inferred from the results shown in Table 28
that the various metals, rare earth elements and rare metals
extracted present in the obtained leaching composition can
eventually be isolated by the processes of the present disclosure
such as, for example, those presented in Examples 1, 2 and 5.
Example 8
[0342] Test have been made for using fly ash as starting material.
The results are shown below in Tables 29, 30 and 31.
TABLE-US-00030 TABLE 29 Leaching conditions for fly ash Leaching
Operating Conditions Processing Reactor Pressure Temperature Time
Acid Ratio Volume 75-80 psi 150-165.degree. C. 420 Stoichiometry +
16 gallons minutes 30%
TABLE-US-00031 TABLE 30 Fly ash used Fly Ash Masse In 2600 Masse
Out 302 % H2O 30%
TABLE-US-00032 TABLE 31 Results - leaching of fly ash Recovery
Yield % Al K Na Fe Ca Si Intial % 8.02 1.21 0.42 8.27 1.65 13.9
compound kg 208.52 31.46 10.92 215.02 42.9 361.4 Cake % 9.15 1.15
0.25 1.75 0.3 36.9 kg 19.3431 2.4311 0.54964 3.6995 0.6342 78.0055
% recovery 90.72% 92.27% 94.97% 98.28% 98.52% 78.42% * 0% MgO
initially
[0343] It can thus be seen that fly ash has been successfully
leached with HCl, thereby allowing for good yields with respect to
the recovery of the various components present in Fly ash. These
various products or components present in the obtained leachate can
thus be all isolated and eventually transformed as previously
indicated in the processes of the present disclosure. The obtained
leachate can then be treated as described in the processes of the
present disclosure. The leaching of example 8 can be considered,
for example, as the leaching 2 of FIG. 1 or FIG. 3; the leaching
102 of FIG. 6 or FIG. 7, etc. For example, the leachate obtained in
Example 8 can then be treated as shown in FIGS. 1, 3, 6 and 7.
Example 9
[0344] Other tests have been made for using another alternative
source of fly ash. A similar process was used. The initial measured
conditions were:
TABLE-US-00033 TABLE 32 Fly Ash initial composition Element
Composition measured (% wt) SiO.sub.2 29.73 Al.sub.2O.sub.3 15.15
Fe.sub.2O.sub.3 11.82 CaO 2.31 Na.sub.2O 0.57 K.sub.2O 1.46
[0345] The samples were leached in batch mode at 75 psig
(150.degree. C.) for a 6 hours duration at stoechiometry+5% excess
Hcl (20% wt).
The following extraction yields were measured at the leaching
stage:
TABLE-US-00034 TABLE 33 Leaching extraction yield measured Raw
element Extraction measured (% wt) Al.sub.2O.sub.3 96.1
Fe.sub.2O.sub.3 98.5 N 95.7 Na.sub.2O K.sub.2O 93.4 CaO 98.7
[0346] After processing through main steps of process (see for
example FIG. 6), the following yields were measured.
TABLE-US-00035 TABLE 34 Global recovery yield Element Global
recovery (% wt) Al.sub.2O.sub.3 93.4 Fe.sub.2O.sub.3 96.5 SiO.sub.2
99.99 No2.sub.2O 93.7 K.sub.2O 93.4 CaO 96.8
Main characteristics of produced alumina were:
[0347] Chemical composition: 99.4%;
[0348] PSD dp.sub.50: 63 um;
[0349] .alpha. Al.sub.2O.sub.3: 2%; and
[0350] Bulk density: 0.63.
Example 10
[0351] Other tests was performed on another alternative source of
material always using the same process as per previous examples.
The initial composition measured was:
TABLE-US-00036 TABLE 35 Fly Ash initial composition Element
Composition measured (% t wt) SiO.sub.2 44.9 Al.sub.2O.sub.3 22.1
Fe.sub.2O.sub.3 21.0 CaO 4.1 Na.sub.2O 0.7 K.sub.2O 2.4
[0352] The samples were leached in hatch mode at 160.degree. C. (80
psig) for a 6 hours duration at stoechiometry+10% Hcl excess (20%
wt).
The following extraction yields were measured at the leaching
stage.
TABLE-US-00037 TABLE 36 Leaching extraction yield measured Raw
element Extraction measured (% wt) Al.sub.2O.sub.3 97.6
Fe.sub.2O.sub.3 99.5 Na.sub.2O 91.1 K.sub.2O 93.3 CaO 94.9
[0353] After processing through main steps of continuous process
(see FIG. 6) the following yield were measured:
TABLE-US-00038 TABLE 37 Global recovery yield Element Global
recovery (% wt) Al.sub.2O.sub.3 94.9 Fe.sub.2O.sub.3 97.5 SiO.sub.2
99.99 Na2O 89.1 K.sub.2O 93.3 CaO 93.0
[0354] The applicants have now discovered fully integrated and
continuous processes with substantially total hydrochloric acid
recovery for the extraction of alumina and other value added
products from various materials that contain aluminum (clay,
bauxite, aluminosilicate materials, slag, red mud, fly ash etc.)
containing aluminum. In fact, the processes allows for the
production of substantially pure alumina and other value added
products purified such as purified silica, pure hematite, pure
other minerals (ex: magnesium oxide) and rare earth elements
products. In addition, the processes do not require thermal
pre-treatment before the acid leach operation. Acid leach can be
carried out using semi-continuous techniques with high pressure and
temperature conditions and very high regenerated hydrochloric acid
concentration. The processes can also be carried out at atmospheric
pressure. In addition, the processes do not substantially generate
any residues not sellable, thus eliminating harmful residues to
environment like in the case of alkaline processes.
[0355] The advantage of the high temperature calcination stage, in
addition for allowing to control the .alpha.-form of alumina
required, can be effective for providing a concentration of
hydrochloric acid in the aqueous form (>38%) that is higher than
the concentration of HCl at the azeotropic point and thus providing
a higher incoming HCl concentration to the leaching stage. The
calcination stage hydrochloric acid network can be interconnected
to two (2) crystallization systems and by pressure regulation
excess HCl can be being absorbed at the highest possible aqueous
concentration. The advantage of having a hexahydrate chloride with
low moisture content (<2%) incoming feed allows for a continuous
basis to recover acid at a concentration that is higher than the
azeotropic concentration. This HCl balance and double usage into
three (3) common parts of the processes and above azeotropic point
is a substantial advance in the art.
[0356] Another advantage is when the use is made of the incoming
chemistry (ferric chloride) to the iron oxide and hydrochloric acid
recovery unit where all excess heat load from any calcination part,
pyrohydrolysis and leaching part is being recovered to
preconcentrate the mother liquor in metal chloride, thus allowing,
at very low temperature, the hydrolysis of the ferric chloride in
the form of very pure hematite and the acid regeneration at the
same concentration than at its azeotropic point.
[0357] A further major advantage of the processes of the present
disclosure at the ferric chloride hydrolysis step can be the
possibility to concentrate rare earth elements in form of chlorides
at very high concentration within the hydrolyser reactor through an
internal loop between hydrolyzer and crystallization. The advantage
is that the processes of the present disclosure benefit from the
various steps where gradual concentration ratios are applied. Thus,
at this stage, in addition to an internal concentration loop,
having the silica, the aluminum, the iron and having in equilibrium
a solution close to saturation (large amount of water evaporated,
no presence of free hydrochloric acid) allows for taking rare earth
elements and non-hydrolysable elements in parts per million into
the incoming feed and to concentrate them in high percentage
directly at the hydrolyser after ferric chloride removal
Purification of the specific oxides (RE-O) can then be performed
using various techniques when in percentage levels. The advantage
can be doubled here: concentration at very high level of rare earth
elements using integrated process stages and most importantly the
approach prevents from having the main stream (very diluted) of
spent acid after the leaching step with the risk of contaminating
the main aluminum chloride stream and thus affecting yields in
Al.sub.2O.sub.3. Another important improvement of the art can be
that on top of being fully integrated, selective removal of
components allows for the concentration of rare earth elements to
relatively high concentration (percentages).
[0358] Another advantage of the processes can be again a selective
crystallization of MgCl.sub.2 through the sparging of HCl from
either the alumina calcination step or the magnesium oxide direct
calcination where in both cases highly concentrated acid both in
gaseous phase or in aqueous form are being generated. As per
aluminum chloride specific crystallization, the direct
interconnection with the calcination reactor, the HCl gas very high
concentration (about 85 to about 95%, about 90 to 95% or about 90%
by weight) allows for exact adjustment in continuous of the
crystallizer based on quality of magnesium oxide targeted. Should
this process step (MgO production or other value added metal oxide)
be required based on incoming process feed chemistry, the rare
earth elements extraction point then be done after this additional
step; the advantage being the extra concentration effect
applied.
[0359] The pyrohydrolysis can allow for the final conversion of any
remaining chloride and the production of refined oxides that can be
used (in case of clay as starting material) as a fertilizer and
allowing the processing of large amount of wash water from the
processes with the recovery of hydrochloric acid in close loop at
the azeotropic point for the leaching step. The advantage of this
last step can be related to the fact that it does totally close the
process loop in terms of acid recovery and the insurance that no
residues harmful to the environment are being generated while
processing any type of raw material, as previously described.
[0360] A major contribution to the art can be that the proposed
fully integrated processes of the present disclosure are allowing,
among others, the processing of bauxite in an economic way while
generating no red mud or harmful residues. In addition to the fact
of being applicable to other natural of raw materials (any suitable
aluminum-containing material or aluminous ores), the fact of using
hydrochloric acid total recovery and a global concentration that
can be higher than the concentration at the azeotropic point (for
example about 21% to about 38%), the selective extraction of value
added secondary products and compliance (while remaining highly
competitive on transformation cost) with environmental
requirements, represent major advantages in the art.
[0361] The processes of the present disclosure can provide fully
continuous and economical solutions that can successfully extract
alumina from various type of materials while providing ultra pure
secondary products of high added value including highly
concentrated rare earth elements and rare metals. The technology
described in the present disclosure can allow for an innovative
amount of total acid recovery and also for a ultra high
concentration of recovered acid. When combing it to the fact that
combined with a semi-continuous leaching approach that favors very
high extraction yields and allows a specific method of
crystallization of the aluminum chloride and concentration of other
value added elements. These processes can also allow for preparing
aluminum with such a produced alumina.
[0362] For example, through the type of equipment that can be used
(for example vertical roller mill) and its specific operation, raw
material grinding, drying and classifying can be applicable to
various kinds of material hardness (furnace slag for example),
various types of humidity (up to 30%) and incoming particle sizes.
The particle size established can provide the advantage, at the
leaching stage, of allowing efficient contact between the minerals
and the acid and then allowing faster kinetics of reaction.
Particles size employed can be effective to reduce drastically the
abrasion issue and allows for the use of a simplified
metallurgy/lining when in contact with hydrochloric acid.
[0363] A further advantage of the processes of the present
disclosure can be the combined high temperature and high incoming
hydrochloric acid concentration. Combined with a semi continuous
operation where the free HCl driving force can be used
systematically, iron and aluminum extraction yields do respectively
reach 100% and 98% in less than about 40% of the reference time of
a basic batch process. Another advantage of higher HCl
concentration than the concentration at azeotropic point can be the
potential of capacity increase. Again a higher HCl concentration
than the concentration of HCl at the azeotropic point and the
semi-continuous approach can represent a substantial advance in the
art.
[0364] Another advantage in that technique used for the mother
liquor separation from the silica after the leaching stage
countercurrent wash, can be that band filters provide ultra pure
silica with expected purity exceeding 96%.
[0365] The crystallization of AlCl.sub.3 into AlCl.sub.3.6H.sub.2O
using dried, cleaned and highly concentrated gaseous HCl as the
sparging agent can allow for a pure aluminum chloride hexahydrate
with only few parts per million of iron and other impurities. A
minimal number of stages can the be required to allow proper
crystal growth.
[0366] The direct interconnection with the calcination of
AlCl.sub.3.6H.sub.2O into Al.sub.2O.sub.3 which can produce very
high concentration of gas allows the exact adjustment in continuous
of the HCl concentration within the crystallizer and thus proper
control of the crystal growth and crystallization process.
[0367] It was thus demonstrated that the present disclosure
provides fully integrated processes for the preparation of pure
aluminum oxide using a hydrochloric acid treatment while producing
high purity and high quality products (minerals) and extracting
rare earth elements and rare metals.
[0368] While a description was made with particular reference to
the specific embodiments, it will be understood that numerous
modifications thereto will appear to those skilled in the art.
Accordingly, the above description and accompanying drawings should
be taken as specific examples and not in a limiting sense.
* * * * *