U.S. patent application number 14/011051 was filed with the patent office on 2013-12-26 for reducing aluminosilicate scale in the bayer process.
This patent application is currently assigned to Nalco Company. The applicant listed for this patent is Nalco Company. Invention is credited to Ji Cui, John D. Kildea, Timothy La, David H. Slinkman.
Application Number | 20130343970 14/011051 |
Document ID | / |
Family ID | 43780614 |
Filed Date | 2013-12-26 |
United States Patent
Application |
20130343970 |
Kind Code |
A1 |
La; Timothy ; et
al. |
December 26, 2013 |
REDUCING ALUMINOSILICATE SCALE IN THE BAYER PROCESS
Abstract
The invention provides methods and compositions for inhibiting
the accumulation of DSP scale in the liquor circuit of Bayer
process equipment. The method includes adding one or more
particular silane based small molecules to the liquor fluid
circuit. These scale inhibitors reduce DSP scale formation and
thereby increase fluid throughput, increase the amount of time
Bayer process equipment can be operational and reduce the need for
expensive and dangerous acid washes of Bayer process equipment. As
a result, the invention provides a significant reduction in the
total cost of operating a Bayer process.
Inventors: |
La; Timothy; (Kardinya,
AU) ; Cui; Ji; (Aurora, IL) ; Kildea; John
D.; (Baldivis, AU) ; Slinkman; David H.;
(Collegeville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nalco Company |
Naperville |
IL |
US |
|
|
Assignee: |
Nalco Company
Naperville
IL
|
Family ID: |
43780614 |
Appl. No.: |
14/011051 |
Filed: |
August 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12567116 |
Sep 25, 2009 |
8545776 |
|
|
14011051 |
|
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Current U.S.
Class: |
423/127 |
Current CPC
Class: |
C22B 21/0015 20130101;
C01F 7/47 20130101; C02F 5/105 20130101 |
Class at
Publication: |
423/127 |
International
Class: |
C02F 5/10 20060101
C02F005/10; C22B 21/00 20060101 C22B021/00 |
Claims
1. A method for reducing aluminosilicate containing scale in a
Bayer process comprising: adding to a Bayer liquor an
aluminosilicate scale reducing amount of a non-polymeric reaction
product resulting from the reaction of: a first molecule which is
an amine-containing small molecule and a second molecule which is
an amine-reactive molecule containing at least one amine-reactive
group per molecule and at least one --Si(OR).sub.n group per
molecule, where n=1, 2, or 3, and R=C.sub.1-C.sub.12 alkyl, aryl,
H, Na, K, Li, or NH.sub.4.
2. The method of claim 1 in which the amine containing molecule is
selected from the group consisting of: isophoronediamine,
C,C,C-trimethylhexanediamine, hexanediamine, meta-xylenediamine,
4,4'-methylenebiscyclohexylamine, 1,2-diaminocyclohexane, saturated
fatty amines, unsaturated fatty amines, N-fatty-1,3-propanediamine,
and any combination thereof.
3. The method of claim 1 wherein the amine-reactive molecule, is
selected from a list comprised of 3-glycidoxypropyltrialkoxysilane,
3-glycidoxypropylalkyldialkoxysilane,
3-glycidoxypropyldialkylmonoalkoxysilane,
3-isocyanatopropyltrialkoxysilane,
3-isocyanatopropylalkyldialkoxysilane,
3-isocyanatopropyldialkylmonoalkoxysilane,
3-chloropropyltrialkoxysilane, 3-chloropropylalkyldialkoxysilane,
and 3-chloropropyldialkylmonoalkoxysilane, and any combination
thereof.
4. The method of claim 1 wherein the reaction product is a product
of a reaction between the first molecule with a second molecule and
also with a third molecule wherein the third molecule is an
amine-reactive hydrophobic molecule with a molecular weight of less
than 500 daltons.
5. The method of claim 4 in which the amine-reactive hydrophobic
small molecule is selected from a group consisting of
C.sub.3-C.sub.22 glycidyl ether, C.sub.3-C.sub.22 isocyanate,
C.sub.3-C.sub.22 chloride, C.sub.3-C.sub.22 bromide,
C.sub.3-C.sub.22 iodide, C.sub.3-C.sub.22 sulfate ester,
C.sub.3-C.sub.22 phenolglycidyl ether, and any combination
thereof.
6. The method of claim 1 in which the amine containing molecule is
selected from the list consisting of cocoalkylpropanediamine,
oleylpropanediamine, dodecylpropanediamine, hydrogenized
tallowalkylpropanediamine, and tallowalkylpropanediamine.
7. The method of claim 1 in which the reaction product comprises
molecules having a structure according to that of Formula I:
##STR00006##
8. The method of claim 1 in which the reaction product comprises
molecules having a structure according to that of Formula II:
##STR00007##
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 12/567,116 filed on Sep. 25, 2009.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable.
BACKGROUND OF THE INVENTION
[0003] The invention relates to compositions, methods, and
apparatuses for improving treating scale in various industrial
process streams, in particular certain silane based small molecules
that have been found to be particularly effective in treating
aluminosilicate scale in a Bayer process stream.
[0004] As described among other places in U.S. Pat. No. 6,814,873
the contents of which are incorporated by reference in their
entirety, the Bayer process is used to manufacture alumina from
Bauxite ore. The process uses caustic solution to extract soluble
alumina values from the bauxite. After dissolution of the alumina
values from the bauxite and removal of insoluble waste material
from the process stream the soluble alumina is precipitated as
solid alumina trihydrate. The remaining caustic solution known as
"liquor" and/or "spent liquor" is then recycled back to earlier
stages in the process and is used to treat fresh bauxite. It thus
forms a fluid circuit. For the purposes of this application, this
description defines the term "liquor". The recycling of liquor
within the fluid circuit however has its own complexities.
[0005] Bauxite often contains silica in various forms and amounts.
Some of the silica is unreactive so it does not dissolve and
remains as solid material within the Bayer circuit. Other forms of
silica (for example clays) are reactive and dissolve in caustic
when added into Bayer process liquors, thus increasing the silica
concentration in the liquor. As liquor flows repeatedly through the
circuit of the Bayer process, the concentration of silica in the
liquor further increases, eventually to a point where it reacts
with aluminum and soda to form insoluble aluminosilicate particles.
Aluminosilicate solid is observed in at least two forms, sodalite
and cancrinite. These and other forms of aluminosilicate are
commonly referred to, and for the purposes of this application
define, the terms "desilication product" or "DSP".
[0006] DSP can have a formula of
3(Na.sub.2O.Al.sub.2O.sub.3.2SiO.sub.2.0-2H.sub.2O)*2NaX where X
represents OH.sup.-, Cl.sup.-, CO.sub.3.sup.2-, SO.sub.4.sup.2-.
Because DSP has an inverse solubility (precipitation increases at
higher temperatures) and it can precipitate as fine scales of hard
insoluble crystalline solids, its accumulation in Bayer process
equipment is problematic. As DSP accumulates in Bayer process
pipes, vessels, heat transfer equipment, and other process
equipment, it forms flow bottlenecks and obstructions and can
adversely affect liquor throughput. In addition because of its
thermal conductivity properties, DSP scales on heat exchanger
surfaces reduce the efficiency of heat exchangers.
[0007] These adverse effects are typically managed through a
descaling regime, which involves process equipment being taken off
line and the scale being physically or chemically treated and
removed. A consequence of this type of regime is significant and
regular periods of down-time for critical equipment. Additionally
as part of the descaling process the use of hazardous concentrated
acids such as sulfuric acid are often employed and this constitutes
an undesirable safety hazard.
[0008] Another way Bayer process operators manage the buildup of
silica concentration in the liquor is to deliberately precipitate
DSP as free crystals rather than as scale. Typically a
"desilication" step in the Bayer process is used to reduce the
concentration of silica in solution by precipitation of silica as
DSP, as a free precipitate. While such desilication reduces the
overall silica concentration within the liquor, total elimination
of all silica from solution is impractical and changing process
conditions within various parts of the circuit (for example within
heat exchangers) can lead to changes in the solubility of DSP,
resulting in consequent precipitation as scale.
[0009] Previous attempts at controlling and/or reducing DSP scale
in the Bayer process have included adding polymer materials
containing three alkyloxy groups bonded to one silicon atom as
described in U.S. Pat. No. 6,814,873 B2, US published applications
2004/0162406 A1, 2004/0011744 A1, 2005/0010008 A2, international
published application WO 2008/045677 A1, and published article Max
HTTM Sodalite Scale Inhibitor: Plant Experience and Impact on the
Process, by Donald Spitzer et. al., Pages 57-62, Light Metals 2008,
(2008) all of whose contents are incorporated by reference in their
entirety.
[0010] Manufacturing and use of these trialkoxysilane-grafted
polymers however can involve unwanted degrees of viscosity, making
handling and dispersion of the polymer through the Bayer process
liquor problematic. Other previous attempts to address foulant
buildup are described in U.S. Pat. Nos. 5,650,072 and 5,314,626
both of which are incorporated by reference in their entirety.
[0011] Thus while a range of methods are available to Bayer process
operators to manage and control DSP scale formation, there is a
clear need for, and utility in, an improved method of preventing or
reducing DSP scale formation on Bayer process equipment. The art
described in this section is not intended to constitute an
admission that any patent, publication or other information
referred to herein is "prior art" with respect to this invention,
unless specifically designated as such. In addition, this section
should not be construed to mean that a search has been made or that
no other pertinent information as defined in 37 C.F.R.
.sctn.1.56(a) exists.
BRIEF SUMMARY OF THE INVENTION
[0012] To satisfy the long-felt but unsolved needs identified
above, at least one embodiment of the invention is directed towards
a method for reducing siliceous scale in a Bayer process comprising
the step of adding to a Bayer liquor an aluminosilicate scale
inhibiting amount of reaction product between an amine-containing
molecule and an amine-reactive molecule containing at least one
amine-reactive group per molecule and at least one --Si(OR)n group
per molecule, where n=1, 2, or 3, and R=H, C1-C12 Alkyl, Aryl, Na,
K, Li, or NH4, or a mixture of such reaction products.
[0013] Another embodiment is directed towards a method for reducing
siliceous scale in a Bayer process comprising the step of adding to
a Bayer liquor an efficacious amount of reaction product between:
1) an amine-containing small molecule, and 2) an amine-reactive
small molecule containing at least one amine-reactive group per
molecule and at least one --Si(OR)n group per molecule, where n=1,
2, or 3, and R=H, C1-C12 Alkyl, Aryl, Na, K, Li, or NH4, or a
mixture of such reaction products, and 3) a non-polymeric amine
reactive hydrophobic hydrocarbon.
[0014] At least one embodiment is directed towards a method of
reducing DSP in a Bayer process comprising the step of adding to
the Bayer process stream an aluminosilicate scale inhibiting amount
of a mixture of products as defined above.
[0015] Additional features and advantages are described herein, and
will be apparent from, the following Detailed Description.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The following definitions are provided to determine how
terms used in this application, and in particular how the claims,
are to be construed. The organization of the definitions is for
convenience only and is not intended to limit any of the
definitions to any particular category.
[0017] "Polymer" means a chemical compound comprising essentially
repeating structural units each containing two or more atoms. While
many polymers have large molecular weights of greater than 500,
some polymers such as polyethylene can have molecular weights of
less than 500. Polymer includes copolymers and homo polymers.
[0018] "Small molecule" means a chemical compound comprising
essentially non-repeating structural units. Because an oligomer
(with more than 10 repeating units) and a polymer are essentially
comprised of repeating structural units, they are not small
molecules. Small molecules can have molecular weights above and
below 500. The terms "small molecule" and "polymer" are mutually
exclusive.
[0019] "Foulant" means a material deposit that accumulates on
equipment during the operation of a manufacturing and/or chemical
process which may be unwanted and which may impair the cost and/or
efficiency of the process. DSP is a type of foulant.
[0020] "Amine" means a molecule containing one or more nitrogen
atoms and having at least one secondary amine or primary amine
group. By this definition, monoamines such as dodecylamine,
diamines such as hexanediamine, and triamines such as
diethylenetriamine, are all amines.
[0021] "GPS" is 3-glycidoxypropyltrimethoxysilane.
[0022] "Alkyloxy" means having the structure of OX where X is a
hydrocarbon and O is oxygen. It can also be used interchangeably
with the term "alkoxy". Typically in this application, the oxygen
is bonded both to the X group as well as to a silicon atom of the
small molecule. When X is C.sub.1 the alkyloxy group consists of a
methyl group bonded to the oxygen atom. When X is C.sub.2 the
alkyloxy group consists of an ethyl group bonded to the oxygen
atom. When X is C.sub.3 the alkyloxy group consists of a propyl
group bonded to the oxygen atom. When X is C.sub.4 the alkyloxy
group consists of a butyl group bonded to the oxygen atom. When X
is C.sub.5 the alkyloxy group consists of a pentyl group bonded to
the oxygen atom. When X is C.sub.6 the alkyloxy group consists of a
hexyl group bonded to the oxygen atom.
[0023] "Monoalkyloxy" means that attached to a silicon atom is one
alkyloxy group.
[0024] "Dialkyloxy" means that attached to a silicon atom are two
alkyloxy groups.
[0025] "Trialkyloxy" means that attached to a silicon atom are
three alkyloxy groups.
[0026] "Synthetic Liquor" or "Synthetic Spent Liquor" is a
laboratory created liquid used for experimentation whose
composition in respect to alumina, soda, and caustic corresponds
with the liquor produced by recycling through the Bayer
process.
[0027] "Bayer Liquor" is actual liquor that has run through a Bayer
process in an industrial facility.
[0028] In the event that the above definitions or a definition
stated elsewhere in this application is inconsistent with a meaning
(explicit or implicit) which is commonly used, in a dictionary, or
stated in a source incorporated by reference into this application,
the application and the claim terms in particular are understood to
be construed according to the definition in this application, and
not according to the common definition, dictionary definition, or
the definition that was incorporated by reference.
[0029] In the Bayer process for manufacturing alumina, bauxite ore
passes through a grinding stage and alumina, together with some
impurities including silica, are dissolved in added liquor. The
mixture then typically passes through a desilication stage where
silica is deliberately precipitated as DSP to reduce the amount of
silica in solution. The slurry is passed on to a digestion stage
where any remaining reactive silica dissolves, thus again
increasing the concentration of silica in solution which may
subsequently form more DSP as the process temperature increases.
The liquor is later separated from undissolved solids, and alumina
is recovered by precipitation as gibbsite. The spent liquor
completes its circuit as it passes through a heat exchanger and
back into the grinding stage. DSP scale accumulates throughout the
Bayer process but particularly at the digestion stage and most
particularly at or near the heat exchanger, where the recycled
liquor passes through.
[0030] In this invention, it was discovered that dosing of various
types of silane-based products can reduce the amount of DSP scale
formed.
[0031] In at least one embodiment of the invention, an effective
concentration of a silane-based small molecule product is added to
some point or stage in the liquor circuit of the Bayer process,
which minimizes or prevents the accumulation of DSP on vessels or
equipment along the liquor circuit.
[0032] In at least one embodiment, the small molecule comprises the
reaction product between an amine and at least one amine-reactive
silane, the silicon of the silane can be monoalkyloxy, dialkyloxy,
trialkyloxy or trihydroxy.
[0033] In at least one embodiment the small molecule is a reaction
product between an amine-containing small molecule and an
amine-reactive molecule containing at least one amine-reactive
group per molecule and at least one --Si(OR).sub.n group per
molecule, where n=1, 2, or 3, and R=H, C1-C12 Alkyl, Aryl, Na, K,
Li, or NH.sub.4, or a mixture of such reaction products.
[0034] In at least one embodiment, the amine molecule is selected
from a linear or branched, aliphatic or cycloaliphatic monoamines
or diamines. The total number of carbon atoms in the amine is
preferred to be less than 30 and more preferred to be less than 20.
In at least one embodiment the amine is selected from a list
consisting of: isophoronediamine, xylenediamine,
bis(aminomethyl)cyclohexane, hexanediamine,
C,C,C-trimethylhexanediamine, methylene bis(aminocyclohexane),
saturated fatty amines, unsaturated fatty amines such as oleylamine
and soyamine, N-fatty-1,3-propanediamine such as
cocoalkylpropanediamine, oleylpropanediamine,
dodecylpropanediamine, hydrogenized tallowalkylpropanediamine, and
tallowalkylpropanediamine and any combination thereof.
[0035] In at least one embodiment, a particularly effective small
molecule comprises the reaction product of an amine small molecule
together with 3-glycidoxypropyltrialkoxysilane (GPS).
[0036] In at least one embodiment the added small molecule is TG14.
For the purposes of this application, the definition of TG14 is a
small molecule having the structure of:
##STR00001##
where the M, J, and R groups are each one selected from the list
consisting of C.sub.1-C.sub.6 alkyloxy, hydrogen, hydroxide, or
C.sub.1-C.sub.6 alkyl groups. M, J, and R can each be different or
can be the same as some or all of the other groups. One form of
TG14 is TG14-R, which is described in U.S. Pat. No. 6,867,318. In
TG14-R the M, J, and R groups are all the same C.sub.1-C.sub.6
alkyloxy group.
[0037] In at least one embodiment the small molecule is a
monoalkyloxy TG14. In at least one embodiment the small molecule is
a dialkyloxy TG14. In at least one embodiment the small molecule is
a trialkyloxy TG14. In at least one embodiment the small molecule
is a trihydroxy TG14.
[0038] In at least one embodiment the added small molecule is DG12.
DG12 is a dodecylamine with one or more silane groups having one,
two, or three alkyloxy groups on each silane group. For purposes of
this application, the definition of DG12 is a small molecule having
the structure of:
##STR00002##
where the M, J, and R groups are each one selected from the list
consisting of C.sub.1-C.sub.6 alkyloxy, hydrogen, hydroxide, or
C.sub.1-C.sub.6 alkyl groups. M, J, and R can each be different or
can be the same as some or all of the other groups. One form of
DG12 is DG12-R, which is a trialkyloxy small molecule.
[0039] In at least one embodiment the small molecule is a
monoalkyloxy DG12. In at least one embodiment the small molecule is
a dialkyloxy DG12. In at least one embodiment the small molecule is
a trialkyloxy DG12. In at least one embodiment the small molecule
is a trihydroxy DG12.
[0040] The small molecule can also be selected from the list
consisting of mono, di, tri or tetramine-epoxy functional silane
adduct, mono, di, tri or tetramine-isocyanato functional silane
adduct, TG14, DG12, any reaction product between a small molecule
amine and an amine-reactive functional silane, and any combination
thereof.
[0041] In at least one embodiment the small molecule is a reaction
product between 1) an amine-containing small molecule, 2) an
amine-reactive molecule containing one amine-reactive group per
molecule and at least one --Si(OR).sub.n group per molecule, where
n=1, 2, or 3, and R=H, C1-C12 Alkyl, Aryl, Na, K, Li, or NH.sub.4,
or a mixture of such reaction products, together with 3) an amine
reactive hydrophobic molecule.
[0042] In at least one embodiment, an amine small molecule is
reacted with both 3-glycidoxypropyltrialkoxysilane (GPS) and a
hydrophobic molecule to form a DSP inhibition composition. The
hydrophobic molecule is an amine-reactive compound having an
amine-reactive functional group such as glycidyl, chloro, bromo, or
isocyanato groups. Besides the amine-reactive group, the
hydrophobic molecule has at least one C.sub.3-C.sub.22 hydrophobic
carbon chain, aromatic or aliphatic, linear or branched. A
particularly effective hydrophobic molecule is 2-ethylhexyl
glycidyl ether (E) the structure of which is shown below:
##STR00003##
Other representative hydrophobic molecules are nonylphenol
glycidylethers, which are described in International Patent
Application WO 08045677A1.
[0043] In at least one embodiment, the amine molecule is selected
from linear or branched, aliphatic or cycloaliphatic monoamines or
diamines. The total number of carbon atoms in the amine is
preferred to be less than 30 and more preferred to be less than
20.
[0044] In at least one embodiment the amine is selected from a list
consisting of: isophoronediamine, xylenediamine,
bis(aminomethyl)cyclohexane, hexanediamine,
C,C,C-trimethylhexanediamine, methylene bis(aminocyclohexane),
saturated fatty amines, unsaturated fatty amines such as oleylamine
and soyamine, N-fatty-1,3-propanediamine such as
cocoalkylpropanediamine, oleylpropanediamine,
dodecylpropanediamine, hydrogenized tallowalkylpropanediamine, and
tallowalkylpropanediamine and any combination thereof.
[0045] In at least one embodiment the amine is isophoronediamine
(A) whose structure is:
##STR00004##
When isophoronediamine is reacted with
3-glycidoxypropyltrialkoxysilane and 2-ethylhexylglycidyl ether at
1:1:1 molar ratio, the resulting inhibition composition is
primarily made of a molecule that has an isophoronediamine backbone
with a single silane unit and a single hydrophobic unit.
[0046] Two representative structures of such
amine-silane-hydrophobe adducts are shown below where the amine
containing molecules are hexanediamine and isophoronediamine
respectively, and wherein M, J, and R groups are each one
independently selected from the list consisting of C.sub.1-C.sub.6
alkyloxy, hydrogen, hydroxide, or C.sub.1-C.sub.6 alkyl groups.
##STR00005##
[0047] In at least one embodiment, a method for reducing siliceous
scale in a Bayer process comprises the step of adding to a Bayer
liquor a scale inhibiting amount of a composition of matter, the
composition comprising a reaction product made from reacting:
[0048] an amine-containing small molecule having at least one
--Si(OR).sub.n per molecule, where n=1, 2, or 3, and R=H, C1-C12
Alkyl, Aryl, Na, K, Li, or NH.sub.4, and [0049] an amine-reactive
hydrophobic molecule with a molecular weight of less than 500
daltons. The amine-containing small molecule can be any one or a
combination of the following molecules:
aminoethylaminopropyltrialkoxysilane,
aminoethylaminopropyldialkoxysilane, and
aminoethylaminopropylmonoalkoxysilane. The amine-reactive
hydrophobic small molecule can be selected from a group consisting
of C.sub.3-C.sub.22 glycidyl ether, C.sub.3-C.sub.22 isocyanate,
C.sub.3-C.sub.22 chloride, C.sub.3-C.sub.22 bromide,
C.sub.3-C.sub.22 iodide, C.sub.3-C.sub.22 sulfate ester,
C.sub.3-C.sub.22 phenolglycidyl ether, and any combination
thereof.
[0050] These silane-based small molecules reduce the amount of DSP
scale formed and thereby prevents its accumulation on Bayer process
equipment.
[0051] The effectiveness of these small molecules was unexpected as
the prior art teaches that only high molecular weight polymers are
effective. Polymer effectiveness was presumed to depend on their
hydrophobic nature and their size. This was confirmed by the fact
that cross-linked polymers are even more effective than single
chain polymers. As a result it was assumed that small molecules
only serve as building blocks for these polymers and are not
effective in their own right. (WO 2008/045677 [0030]). Furthermore,
the scientific literature states "small molecules containing" . . .
"[an] Si--O.sub.3 grouping are not effective in preventing sodalite
scaling" . . . because . . . "[t]he bulky group" . . . "is
essential [in] keeping the molecule from being incorporated into
the growing sodalite." Page 57 9 Light Metals 2008, (2008). However
it has recently been discovered that in fact, as further explained
in the provided examples, small molecules such as those described
herein are actually effective at reducing DSP scale.
[0052] It is believed that there are at least three advantages to
using a small molecule-based inhibitor as opposed to a polymeric
inhibitor with multiple repeating units of silane and hydrophobes.
A first advantage is that the smaller molecular weight of the
product means that there are a larger number of active, inhibiting
moieties available around the DSP seed crystal sites at the DSP
formation stage. A second advantage is that the lower molecular
weight allows for an increased rate of diffusion of the inhibitor,
which in turn favors fast attachment of the inhibitor molecules
onto DSP seed crystals. A third advantage is that the lower
molecular weight avoids high product viscosity and so makes
handling and injection into the Bayer process stream more
convenient and effective.
EXAMPLES
[0053] The foregoing may be better understood by reference to the
following examples, which are presented for purposes of
illustration and are not intended to limit the scope of the
invention. In particular the examples demonstrate representative
examples of principles innate to the invention and these principles
are not strictly limited to the specific condition recited in these
examples. As a result it should be understood that the invention
encompasses various changes and modifications to the examples
described herein and such changes and modifications can be made
without departing from the spirit and scope of the invention and
without diminishing its intended advantages. It is therefore
intended that such changes and modifications be covered by the
appended claims.
Example 1
[0054] Polypropylene bottles and a temperature controlled rotary
water bath were used under isothermal conditions for batch
desilication experiments. Synthetic spent Bayer liquor was prepared
on the same day or one day prior to the experiment. Typical
analysis for the synthetic liquor used was:
Alumina (A): 84.62 g/L as Al.sub.2O.sub.3;
Caustic (C): 238.42 g/L as Na.sub.2CO.sub.3;
Ratio of A to C: 0.355.
[0055] A series of tests were conducted by adding the specified
dose of TG14 and DG12 to the bottles containing synthetic spent
Bayer liquor (150-200 mL). The synthetic liquor was heated in the
water bath and as the desired temperature (95.degree. C.) was
reached, sodium metasilicate solution was added. (A calculated
amount to give the starting SiO.sub.2 concentration of 0.05M was
added.) The resulting solutions were heated and held at 95.degree.
C. for the duration of the test (4 hours). Final solutions were
filtered through a 0.45 .mu.m membrane to collect solids, which
were washed with hot de-ionized water and air-dried. Table 1 shows
the percent of DSP mass precipitated relative to an undosed control
test.
TABLE-US-00001 TABLE 1 Percent DSP Mass precipitated in tests
versus undosed control sample mass. % DSP Mass Dosage, Precipitated
vs. Products ppm Control Control 0 100 TG14 200 34 DG12 200 69
[0056] The results showed that TG14 and DG12 reduce the mass of the
resulting precipitate indicating inhibition of DSP formation.
Example 2
[0057] A series of further tests were conducted in a similar manner
to that described in example 1 using Bayer process liquor from two
operational refineries. In these and subsequent examples the
following method was employed:
[0058] To a series of polypropylene bottles containing plant spent
liquor (200 mL each), a 20 mL sample of 117 g/L
Na.sub.2SiO.sub.3.5H.sub.2O solution was added (3.0 g/L as
SiO.sub.2). To selected bottles, a specified dose of individual
inhibitor product was also added. Duplicate bottles for each dose
of each inhibitor were used, together with duplicate undosed
control samples in each test. The resulting liquor mixtures were
heated in a rotating water bath with temperature held constantly at
95.degree. C. throughout the duration of the test (4 hours) so as
to induce precipitation of DSP. After 4 hours, the contents of each
bottle were individually filtered to collect the solids, which were
washed with hot de-ionized water and dried at room temperature
overnight. The effectiveness of the additives was determined by
comparing the mass of the solid obtained from samples where an
inhibitor was added, to that of the undosed control samples
(without additives).
[0059] Tables 2 displays the results of individual tests using
inhibitor molecules produced by the reaction of a small molecule
amine with the amine-reactive silane, 3-glycidoxypropyltrialkoxysi
lane (GPS). Inhibition results are displayed as the mass of DSP
precipitated from treated samples as a percentage of the mass of
DSP precipitated from untreated control samples. Average values of
duplicate samples for all treatments were used to calculate the
percent precipitated.
[0060] The individual amines used to produce the various reagents
and the nomenclature used to identify the amines is as follows:
A=Isophoronediamine
T=C,C,C-trimethylhexanediamine
S=Soyamine
O=Oleylamine
[0061] The ratio denoted in table 2 indicates the molar ratio of
amine to GPS (as amine:GPS) used in the reaction to produce the
active small molecule products. Variation of the molar ratio was
observed to result in products displaying a variety of inhibitory
properties.
TABLE-US-00002 TABLE 2 Inhibition of DSP by small molecule adducts
of amine/silane reaction. % DSP Amine- Product Precipitated Active
Dose vs Undosed Amine Silane Hydrophobe Ratio (ppm) control A GPS
-- 1:4 25 86 T GPS -- 1:4 50 95 S GPS -- 1:2 40 72 O GPS -- 1:2 40
73
[0062] In all cases the addition of the reaction product of the
amine and GPS is shown to result in a lower mass of DSP
precipitated than the mass of untreated samples. This indicates
inhibition of the precipitation of DSP when such reagents are added
to the Bayer liquor.
Example 3
[0063] Similar tests were conducted to assess the effect of
reagents comprising the reaction products of 1) a small molecule
amine, 2) an amine reactive silane and 3) an amine reactive
hydrophobe. The method used was the same as that described in
example 2 and reagents used to produce the active components are
listed in table 3 together with the activity as measured by percent
of DSP precipitated compared to an undosed control sample.
[0064] Again, in all cases the precipitation of DSP is reduced by
addition of the reaction products as specified, indicating that
inhibition of DSP precipitation is achieved by application of the
relevant small molecules to the Bayer liquor.
[0065] Nomenclature used in Table 3 is the same as that used for
Table 2 with the addition of:
ED=N-[3-(Trimethoxysilyl)propyl]ethylenediamine
P=4-nonylphenolglycidyl ether E=2-Ethylhexylglycidyl ether
H=1,6-Hexanediamine
TABLE-US-00003 [0066] TABLE 3 Inhibition of DSP by small molecule
adducts of amine/silane/hydrophobe reaction. % DSP Amine- Product
Precipitated Active Dose vs Undosed Amine Silane Hydrophobe Ratio
(ppm) control A GPS P 1:3:1 40 75 A GPS E 1:2:2 40 96 A GPS E 1:2:1
40 63 A GPS E 1:1:1 50 18 A GPS E 1:1:1 20 67 ED -- E 1:0:1 80 44 A
GPS E 1:1:0.5 20 57 T GPS E 1:1:1 6 2 H GPS E 1:1:0.3 9 7
[0067] While this invention may be embodied in many different
forms, there are described in detail herein specific preferred
embodiments of the invention. The present disclosure is an
exemplification of the principles of the invention and is not
intended to limit the invention to the particular embodiments
illustrated. All patents, patent applications, scientific papers,
and any other referenced materials mentioned herein are
incorporated by reference in their entirety. Furthermore, the
invention encompasses any possible combination of some or all of
the various embodiments mentioned herein, described herein and/or
incorporated herein. In addition the invention encompasses any
possible combination that also specifically excludes any one or
some of the various embodiments mentioned herein, described herein
and/or incorporated herein.
[0068] The above disclosure is intended to be illustrative and not
exhaustive. This description will suggest many variations and
alternatives to one of ordinary skill in this art. All these
alternatives and variations are intended to be included within the
scope of the claims where the term "comprising" means "including,
but not limited to". Those familiar with the art may recognize
other equivalents to the specific embodiments described herein
which equivalents are also intended to be encompassed by the
claims.
[0069] All ranges and parameters disclosed herein are understood to
encompass any and all subranges subsumed therein, and every number
between the endpoints. For example, a stated range of "1 to 10"
should be considered to include any and all subranges between (and
inclusive of) the minimum value of 1 and the maximum value of 10;
that is, all subranges beginning with a minimum value of 1 or more,
(e.g. 1 to 6.1), and ending with a maximum value of 10 or less,
(e.g. 2.3 to 9.4, 3 to 8, 4 to 7), and finally to each number 1, 2,
3, 4, 5, 6, 7, 8, 9, and 10 contained within the range. All
percentages, ratios and proportions herein are by weight unless
otherwise specified.
[0070] This completes the description of the preferred and
alternate embodiments of the invention. Those skilled in the art
may recognize other equivalents to the specific embodiment
described herein which equivalents are intended to be encompassed
by the claims attached hereto.
* * * * *