U.S. patent application number 10/461888 was filed with the patent office on 2004-05-27 for disassociation processing of metal oxides.
Invention is credited to Boren, Richard M., Hammel, Charles F., Pahlman, John E., Pahlman, Kathleen S., Tuzinski, Patrick A..
Application Number | 20040101457 10/461888 |
Document ID | / |
Family ID | 32329691 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040101457 |
Kind Code |
A1 |
Pahlman, John E. ; et
al. |
May 27, 2004 |
Disassociation processing of metal oxides
Abstract
The invention relates to systems and processes for recovery
and/or extraction of metal values from ore or other raw material
containing oxides of the metal and to precipitation of oxides of
metals that have oxidation states and/or pollutant loading
capacities equal to or greater than that of the metal oxides in the
ore or other raw material which are suitable, amongst other uses,
as a sorbent for capture and removal of target pollutants from
industrial and other gas streams. Further, the invention relates to
oxides of metals so recovered and precipitated.
Inventors: |
Pahlman, John E.;
(Bloomington, MN) ; Pahlman, Kathleen S.;
(Bloomington, MN) ; Hammel, Charles F.;
(Escondido, CA) ; Boren, Richard M.; (Bakerfield,
CA) ; Tuzinski, Patrick A.; (Bloomington,
MN) |
Correspondence
Address: |
INTELLECTUAL PROPERTY GROUP
FREDRIKSON & BYRON, P.A.
4000 PILLSBURY CENTER
200 SOUTH SIXTH STREET
MINNEAPOLIS
MN
55402
US
|
Family ID: |
32329691 |
Appl. No.: |
10/461888 |
Filed: |
June 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60387994 |
Jun 11, 2002 |
|
|
|
Current U.S.
Class: |
423/50 |
Current CPC
Class: |
B01J 20/3433 20130101;
C22B 47/0081 20130101; B01J 23/34 20130101; B01J 20/3475 20130101;
C22B 47/0054 20130101; B01J 20/06 20130101 |
Class at
Publication: |
423/050 |
International
Class: |
C22B 047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2003 |
US |
US03/07098 |
Dec 23, 2002 |
US |
US02/41276 |
Claims
What is claimed is:
1. A method for rapid and adaptive recovery of metal values as
precipitates of oxides of metals having loading capacities and/or
oxidation states equal to or greater than that of the metal oxides
in the ore or other raw material, comprising: leaching metal values
from ore or other metal oxide containing material to form a
solution containing cations and anions of disassociated metal
salts; heating the solution containing cations and anions of
disassociated metal salts; mixing the heated solution containing
cations and anions of disassociated metal salts and a heated
aqueous oxidizing solution in a precipitation vessel to form a
solution mixture, the heated aqueous oxidizing solution being
prepared so as to have Eh and pH values within the metal oxide
stability area of an aqueous solution heated to a temperature at or
near boiling temperature at atmospheric pressure and being heated
to a temperature at or near the boiling temperature; monitoring and
adjusting the temperature, Eh value and pH value of the solution
mixture so as to rapidly move mixture conditions into and to
maintain them within the metal oxide stability area; and
maintaining the solution conditions within the metal oxide
stability area so as to precipitate the metal cations out of
solution as precipitated oxides of metal having loading capacities
and/or average oxidation states equal to or greater than that of
the metal oxides in the ore or other raw material.
2. A method for rapid and adaptive recovery of manganese values as
precipitates of oxides of manganese having loading capacities
and/or oxidation states equal to or greater than that of the oxides
of manganese in the ore or other raw material, comprising: leaching
manganese values from ore or other metal oxide containing material
to form a solution containing cations and anions of disassociated
manganese salts; heating the solution containing cations and anions
of disassociated manganese salts; mixing the heated solution
containing cations and anions of disassociated manganese salts and
a heated aqueous oxidizing solution in a precipitation vessel to
form a solution mixture, the heated aqueous oxidizing solution
being prepared so as to have Eh and pH values within the MnO2
stability area of an aqueous solution heated to a temperature at or
near boiling temperature at atmospheric pressure and being heated
to a temperature at or near the boiling temperature; monitoring and
adjusting the temperature, Eh value and pH value of the solution
mixture so as to rapidly move mixture conditions into and to
maintain them within the MnO2 stability area; and maintaining the
solution conditions within the MnO2 stability area so as to
precipitate the manganese cations out of solution as precipitated
oxides of manganese having loading capacities and/or average
oxidation states equal to or greater than that of the oxides of
manganese in the ore or other raw material.
3. The method of any one of claims 1-2, further comprising the
step: maintaining solution or solution mixture pH constant
throughout the processing cycle.
4. The method of claim 1 further comprising the steps of:
separating the oxides of metal from the aqueous oxidizing solution
to provide separated oxides of metal and a oxidation filtrate, the
oxidation filtrate being routed for further processing and
handling; rinsing and filtering the separated oxides of metal to
provide rinsed oxides of metal and a rinse filtrate, the rinse
filtrate being directed for further handling and processing;
optionally, drying and/or comminuting the rinsed oxides of
metal.
5. The method of claim 2 further comprising the steps of:
separating the oxides of manganese from the aqueous oxidizing
solution to provide separated oxides of manganese and a oxidation
filtrate, the oxidation filtrate being routed for further
processing and handling; rinsing and filtering the separated oxides
of manganese to provide rinsed oxides of manganese and a rinse
filtrate, the rinse filtrate directed further handling and
processing; optionally, drying and/or comminuting the rinsed oxides
of manganese.
6. The method of any one of claims 1-2, wherein the aqueous
oxidizing solution contains an oxidant or oxidizer compatible with
chemicals used to adjust the pH.
7. The method of any one of claims 1-2, wherein the aqueous
oxidizing solution contains an oxidant or oxidizer selected from
the group consisting of persulfates, chlorates, perchlorates,
permanganates, peroxides, hypochlorites, oxygen, air, and ozone
(O3).
8. The method of claim 1, wherein temperature, Eh and pH are
maintained within the metal oxide stability area for a period
ranging from about 20 to about 70 minutes.
9. The method claim 2, wherein temperature, Eh and pH are
maintained within the MnO2 stability area for a period ranging from
about 20 to about 70 minutes.
10. The method of claim 1, wherein temperature, Eh and pH are
maintained within the metal oxide stability area for a period
ranging from about 35 to about 55 minutes.
11. The method of claim 2, wherein temperature, Eh and pH are
maintained within the MnO2 stability area for a period ranging from
about 35 to about 55 minutes.
12. The method of claim 1, wherein temperature, Eh and pH are
maintained within the metal oxide stability area for a period
ranging from about 40 to about 50 minutes.
13. The method of claim 2, wherein temperature, Eh and pH are
maintained within the MnO2 stability area for a period ranging from
about 40 to about 50 minutes.
14. Oxides of metal produced by a method of rapid and adaptive
recovery of metal values as precipitates of oxides of metals having
loading capacities and/or oxidation states equal to or greater than
that of the metal oxides in the ore or other raw material, the
method comprising the steps of: leaching metal values from ore or
other metal oxide containing material to form a solution containing
cations and anions of disassociated metal salts; heating the
solution containing cations and anions of disassociated metal
salts; mixing the heated solution containing cations and anions of
disassociated metal salts and a heated aqueous oxidizing solution
in a precipitation vessel to form a solution mixture, the heated
aqueous oxidizing solution being prepared so as to have Eh and pH
values within the metal oxide stability area of an aqueous solution
heated to a temperature at or near boiling temperature at
atmospheric pressure and being heated to a temperature at or near
the boiling temperature; monitoring and adjusting the temperature,
Eh value and pH value of the solution mixture so as to rapidly-move
mixture conditions into and to maintain them within the metal oxide
stability area; and maintaining the solution conditions within the
metal oxide stability area so as to precipitate the metal cations
out of solution as precipitated oxides of metal having loading
capacities and/or oxidation states equal to or greater than that of
the metal oxides in the ore or other raw material.
15. Oxides of manganese produced by a method of rapid and adaptive
recovery of manganese values as precipitates of oxides of manganese
having loading capacities and/or oxidation states equal to or
greater than that of the metal oxides in the ore or other raw
material, the method comprising: leaching manganese values from ore
or other raw material to form a solution containing cations and
anions of disassociated manganese salts; heating the solution
containing cations and anions of disassociated manganese salts;
mixing the heated solution containing cations and anions of
disassociated manganese salts and a heated aqueous oxidizing
solution in a precipitation vessel to form a solution mixture, the
heated aqueous oxidizing solution being prepared so as to have Eh
and pH values within the MnO2 stability area of an aqueous solution
heated to a temperature at or near boiling temperature at
atmospheric pressure and being heated to a temperature at or near
the boiling temperature; monitoring and adjusting the temperature,
Eh value and pH value of the solution mixture so as to rapidly move
mixture conditions into and to maintain them within the MnO2
stability area; and maintaining the solution conditions within the
MnO2 stability area so as to precipitate the manganese cations out
of solution as precipitated oxides of manganese having loading
capacities and/or oxidation states equal to or greater than that of
the oxides of manganese in the ore or other raw material.
16. The oxides of metal of claim 14, wherein the method further
comprises the step of maintaining solution or solution mixture pH
constant throughout the processing cycle.
17. The oxides of manganese of claim 15, wherein the method further
comprises the step of maintaining solution or solution mixture pH
constant throughout the processing cycle.
18. The oxides of metal of claim 14, wherein the method further
comprises the steps of: separating the oxides of metal from the
aqueous oxidizing solution to provide separated oxides of metal and
a oxidation filtrate, the oxidation filtrate being routed for
further processing and handling; rinsing and filtering the
separated oxides of metal to provide rinsed oxides of metal and a
rinse filtrate, the rinse filtrate being directed for further
handling and processing; and optionally, drying and/or comminuting
the rinsed oxides of metal.
19. The oxides of manganese of claim 15, wherein the method further
comprises the steps of: separating the oxides of manganese from the
aqueous oxidizing solution to provide separated oxides of manganese
and a oxidation filtrate, the oxidation filtrate being routed for
further processing and handling; rinsing and filtering the
separated oxides of manganese to provide rinsed oxides of manganese
and a rinse filtrate, the rinse filtrate directed further handling
and processing; and optionally, drying and/or comminuting the
rinsed oxides of manganese.
20. The oxides of metal of claim 14, wherein the aqueous oxidizing
solution contains as oxidant or oxidizer selected from the group
consisting of persulfates, chlorates, perchlorates, permanganates,
peroxides, hypochlorites, oxygen, air, and ozone (O3).
21. The oxides of manganese of claim 15, wherein the aqueous
oxidizing solution contains as oxidant or oxidizer selected from
the group consisting of persulfates, chlorates, perchlorates,
permanganates, peroxides, hypochlorites, oxygen, air, and ozone
(O3).
22. The oxides of metal of claim 14, wherein temperature, Eh and pH
are maintained within the metal oxide stability area for a period
ranging from about 20 to about 70 minutes.
23. The oxides of manganese of claim 15, wherein temperature, Eh
and pH are maintained within the MnO2 stability area for a period
ranging from about 20 to about 70 minutes.
24. The oxides of metal of claim 14, wherein temperature, Eh and pH
are maintained within the metal oxide stability area for a period
ranging from about 35 to about 55 minutes.
25. The oxides of manganese of claim 15, wherein temperature, Eh
and pH are maintained within the MnO2 stability area for a period
ranging from about 35 to about 55 minutes.
26. The oxides of metal of claim 14, wherein temperature, Eh and pH
are maintained within the metal oxide stability area for a period
ranging from about 40 to about 50 minutes.
27. The oxides of manganese of claim 15, wherein temperature, Eh
and pH are maintained within the MnO2 stability area for a period
ranging from about 40 to about 50 minutes.
28. A system for rapid and adaptive recovery of metal values as
precipitates of oxides of metal having loading capacities and/or
oxidation states equal to or greater than that of the metal oxides
in the ore or other raw material, the system comprising: a well
bore hole for injecting a leaching solution; a leaching solution
injector; a well bore hole for recovering a solution containing
cations and anions of disassociated metal salts; solution
recovering equipment; a precipitation vessel equipped with probes
for measuring temperature, Eh and pH values of aqueous solutions
within the precipitation vessel, the precipitation vessel being
configured for introduction of a solution containing cations and
anions of disassociated metal salts; a oxidant feeder containing a
supply of aqueous oxidizing solution, the aqueous oxidizing
solution being prepared so as to have Eh and pH values within the
metal oxide stability area for an aqueous solution heated to a
temperature at or near boiling temperature at atmospheric pressure;
a heater for providing heat to the precipitation vessel; a base
and/or acid feeder for feeding base or acid to the precipitation
vessel; at least one filtration and/or rinse unit, which optionally
may be incorporated into and a part of the precipitation vessel;
and a controller for simultaneously monitoring and adjusting system
operational parameters and regulating system components, the
controller being in electronic communication with the probes of the
precipitation vessel, the feeders, the at least one filtration
and/or rinse unit and the heaters; the controller being capable of
monitoring and adjusting system operational parameters selected
from the group consisting of temperature, Eh, pH and feeder rates
so as maintain conditions in the oxidation vessel within the metal
oxide stability area through processing cycles.
29. A system for rapid and adaptive recovery of manganese values as
precipitates of oxides of manganese having loading capacities
and/or oxidation states equal to or greater than that of the metal
oxides in the ore or other raw material, the system comprising; a
well bore hole for injecting a leaching solution; a well bore hole
for recovering a solution containing cations and anions of
disassociated manganese salts; solution recovering equipment; a
leaching solution injector; a precipitation vessel equipped with
probes for measuring temperature, Eh and pH values of aqueous
solutions within the precipitation vessel, the precipitation vessel
being configured for introduction of a solution containing cations
and anions of disassociated manganese salts; a oxidant feeder
containing a supply of aqueous oxidizing solution, the aqueous
oxidizing solution being prepared so as to have Eh and pH values
within the MnO2 stability area for an aqueous solution heated to a
temperature at or near boiling temperature at atmospheric pressure;
a heater for providing heat to the precipitation vessel; a base
and/or acid feeder for feeding base or acid to the precipitation
vessel; at least one filtration and/or rinse unit, which optionally
may be incorporated into and a part of the precipitation vessel;
and a controller for simultaneously monitoring and adjusting system
operational parameters and regulating system components, the
controller being in electronic communication with the probes of the
precipitation vessel, the feeders, the at least one filtration
and/or rinse unit and the heaters; the controller being capable of
monitoring and adjusting system operational parameters selected
from the group consisting of temperature, Eh, pH and feeder rates
so as maintain conditions in the oxidation vessel within the MnO2
stability area through processing cycles.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 60/387,994, filed Jun. 11, 2002, U.S. Provisional
Application No. 60/342,587, filed Dec. 21, 2001, now U.S. patent
application Ser. No. 10/328,490, filed Dec. 23, 2002 and
International Application No. US02/41276, filed Dec. 23, 2002, and
U.S. Provisional Application No. 60/362,477, filed Mar. 6, 2002,
now U.S. patent application Ser. No. 10/384,473, filed Mar. 6, 2003
and International Application No. US03/07098, filed Mar. 6, 2003,
which are incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The invention relates to systems and processes for recovery
and/or extraction of metal values from ore or other raw material
containing oxides of the metal and precipitation of oxides of
metals that have oxidation states and/or pollutant loading
capacities equal to or greater than that of the metal oxides in the
ore or other raw material which are suitable, amongst other uses,
as a sorbent for capture and removal of target pollutants from
industrial and other gas streams. Further, the invention relates to
oxides of metals so recovered and precipitated.
BACKGROUND OF THE INVENTION
[0003] Metal oxides of various types have been found to have very
beneficial properties. For example, oxides of manganese are
utilized for a number of industrial applications, such as pollution
control systems, steel manufacture, batteries and catalytic
converters, to name a few. Of particular, but not exclusive,
interest to Applicants is the use of oxides of manganese in
pollution control systems. Applicants are co-inventors of the
subject matter of co-pending U.S. patent applications Nos.
09/919,600, 09/951,697, 10/044,089 and 10/025,270, the disclosures
of which are incorporated herein by reference. These applications
disclose pollutant removal systems and processes, known as
Pahlman.TM. systems and processes, which utilize dry and wet
removal techniques and combinations thereof, incorporating the use
of oxides of manganese as a sorbent for capture and removal of
target pollutants from gas streams.
[0004] Metal oxides that are useful in these applications are not
limited to manganese oxides. Any metal oxide that forms soluble
and/or thermally decomposable metal salts when reacted with target
pollutants in a gas stream may be used in such pollutant removal
systems and are relevant to this invention. Suitable metal oxide
will react with a target pollutant to produce a reaction product
exhibiting one or both properties. Metal oxides that can yield
reaction products with the desired properties include, but are not
limited to representative metals and transition metals.
[0005] Before going further, the following definitions will be with
respect to this background discussion and to the understanding of
the invention disclosed herein:
[0006] The term "target pollutant," as used herein, refers to the
pollutant or pollutants that are to be captured and removed from a
gas stream. Examples of target pollutants that may be removed with
an oxide of metal sorbent include, but are not limited to, NOX,
SOX, mercury (Hg) and mercury compounds, H2S and other totally
reduced sulfides (TRS), chlorides, such as hydrochloric acid (HCl),
and oxides of carbon (CO and CO2).
[0007] "Reacted" or "loaded," as used interchangeably herein,
refers in conjunction with "oxides of metal," "oxides of
manganese," and/or "sorbent" to oxides of metal, oxides of
manganese, or sorbent that has interacted with one or more target
pollutants in a gas whether by chemical reaction, catalysis,
adsorption or absorption. The term does not mean that all reactive
or active sites of the sorbent have been utilized as all such sites
may not actually be utilized.
[0008] "Unreacted" or "virgin," as used interchangeably herein,
refers in conjunction with "oxides of metal," "oxides of manganese"
and/or "sorbent" to oxides of metal, oxides of manganese or sorbent
that has not interacted with target pollutants in a gas or gas
stream.
[0009] "Nitrates of manganese," as used herein, refers to and
includes the various forms of manganese nitrate, regardless of
chemical formula, that may be formed through the chemical reaction
between NOX and the sorbent and includes hydrated forms as
well.
[0010] "Sulfates of manganese," as used herein, refers to and
includes the various forms of manganese sulfate, regardless of
chemical formula that may be formed through the chemical reaction
between SOX and the sorbent and includes hydrated forms as
well.
[0011] "Metal oxide stability area" or "stability area," as used
herein, refers to the region of thermodynamic stability for metal
oxides at their valence states delineated by Eh and pH values for
aqueous solutions or, phrased alternatively, the domain of metal
oxide stability for an aqueous solution. More specifically, it
refers to the region or domain delineated by Eh and pH values for
aqueous solutions in an electrochemical stability diagram, such as
presented by Pourbaix diagrams and their equivalents, such as the
Latimer Diagram or the Frost Diagram.
[0012] "MnO.sub.2 stability area," as used herein, refers to the
metal oxide stability area for manganese dioxide; or, phrased
alternatively, the region or domain of MnO.sub.2 stability
delineated by Eh and pH values for aqueous solutions in an
electrochemical stability diagram, such as presented by Pourbaix
diagrams and their equivalents, such as the Latimer Diagram or the
Frost Diagram.
[0013] "Recovered metal values" or "recovered manganese values," as
used herein, refers to metal or manganese recovered from raw metal
ores or nodules or other.
[0014] "Regenerated oxides of metal" or "regenerated oxides of
manganese," as used herein, refers to loaded or reacted oxides of
manganese that have been processed according to the methods of the
invention in which a heated aqueous oxidizing solution is mixed
with a heated slurry of loaded oxides of metal to form a mixture,
or a heated aqueous oxidizing solution to which loaded oxides of
metal are added to from a slurry mixture, the mixtures being
adjusted and maintained so as to be within the metal oxide
stability area.
[0015] "Precipitated oxides of metal" or "precipitated oxides of
manganese," as used herein, refers to oxides of metal formed or
newly formed by precipitation from a mixture of a heated metal salt
solution and a heated aqueous oxidizing solution or a mixture
formed by addition of manganese salt solution to a heated aqueous
oxidizing solution, the mixtures being adjusted and maintained so
as to be within the metal oxide stability area.
[0016] Oxides of manganese or other metals in various forms,
utilized as sorbents, are introduced into the Pahlman.TM. systems
(and other pollution removal systems) and interact with the target
pollutants in gas streams routed through the systems as a catalyst,
a reactant, an absorbent or an adsorbent. Without being limited and
by way of example, in one possible interaction in the process of
pollutant removal, the oxidation (or valence) state of the oxides
of manganese sorbent, for example, is reduced from its original
state during reaction with the target pollutants. For example,
where the target pollutants are NOX or SO2, pollutant removal
occurs possibly through overall reactions such as the
following:
SO2+MnO2.fwdarw.MnSO4 Reaction (1)
2NO+O2+MnO2.fwdarw.Mn(NO3)2 Reaction (2)
[0017] In both of the reactions above, manganese (Mn) is reduced
from the +4 valence state to +2 valence state during formation of
the reaction products shown. It should be noted that the actual
reactions may include other steps not shown, and that indicating
Reactions 1 and 2 is solely for illustrative purposes.
[0018] Many representative and transition metals, and therefore
oxides of these metals, may exist in different valence (oxidation)
states. Of particular interest and usefulness for gaseous pollutant
removal are those oxides of manganese having valence states of +2,
+3, and +4, which correspond to the oxides MnO, Mn2O3, MnO2 and
Mn3O4. The oxide Mn3O4 is believed to be a solid-solution of both
the +2 and +3 states.
[0019] A characteristic of most oxides of manganese species is
non-stoichiometry. For example; most MnO2 species typically contain
on average less than the theoretical number of 2 oxygen atoms, with
numbers more typically ranging from 1.5 to 2.0. The
non-stoichiometry characteristic of oxides of manganese is thought
to result from solid-solution mixtures of two or more oxide species
(such as may occur in the oxide Mn3O4), or distortions of molecular
structure and exists in all but the beta (.beta.), or pyrolusite,
form of manganese dioxide. Oxides of manganese having the formula
MnO.sub.x where X is about 1.5 to about 2.0 are particularly
suitable for use as sorbent for dry removal of target pollutants
from gas streams and may be also be utilized in wet removal.
However, the most active types of oxides of manganese for use as a
sorbent for target pollutant removal usually have the formula
MnO1.7 to 1.95, which translates into average manganese valence
states of +3.4 to +3.9, as opposed to the theoretical +4.0 state.
It is unusual for average valence states above about 3.9 to exist
in most forms of oxides of manganese.
[0020] Oxides of manganese are known to exhibit several
identifiable crystal structures, which result from different
assembly combinations of their basic molecular structural units.
These basic structural "building block" units are MnO6 octahedra,
which consist of one manganese atom at the geometric center, and
one oxygen atom at each of the six apex positions of an octahedral
geometrical shape. The octahedra may be joined together along their
edges and/or corners, to form "chain" patterns, with void spaces
("tunnels"). Regular (and sometimes irregular) three-dimensional
patterns consist of layers of such "chains" and "tunnels" of joined
octahedra. These crystalline geometries are identified by
characteristic x-ray diffraction (XRD) patterns. Most oxides of
manganese are classifiable into one or more of the six fundamental
crystal structures, which are called alpha (.alpha.), beta
(.beta.), gamma (.gamma.), delta (.delta.), epsilon (.epsilon.),
and ramsdellite. Certain older literature also included rho (.rho.)
and lambda (.lambda.) structures, which are now thought obsolete,
due partly to improvements in XRD technique. Some (amorphous) forms
of MnO2 exhibit no crystalline structure. Oxides of other
transition metals and some representative metals also may have wide
varieties of stoichiometric configurations and crystalline
structures similar to the manganese example.
[0021] One of the key features of transition metal chemistry is the
wide range of oxidation states (oxidation numbers) that the metals
can show. Certain characteristics of oxides of metals probably
arise from the size and shape of voids within these crystalline
patterns and from certain elements, and compounds, which may occupy
the voids and appear to help prevent collapse of certain
structures. Applicants believe that these characteristics in
addition to the oxidation state may have an affect upon the loading
capacity of oxides of metal sorbent. Further, many oxides of
metals, including those that are the subject of the present, come
in hydrated or hydrous forms, having water chemically bound or
combined to or within their crystalline structures, containing one
or more molecules of water; this is sometimes referred to as bound
water, structural water, water of crystallization or water of
hydration. In these forms, the water is combined is such a way that
it may be removed with sufficient heat without substantially
changing the chemical structure of the oxides of metal. Such oxides
of metal are also useful as a sorbent. This bound water may also
contribute to the chemical reactivity and possibly catalytic
behavior of the species.
[0022] Some oxides of metal have the ability to absorb oxygen from
gas. Manganous oxide (MnO) and Mn(OH)2 will oxidize to MnO2 in the
presence of air, for example. Additionally, the dioxides of
manganese are themselves oxidizers. They readily exchange oxygen in
chemical reactions and are known to have catalytic properties. This
oxygen exchange ability may be related to proton mobility and
lattice defects common within most MnO2 crystal structures.
[0023] The oxidizing potential of MnO2 and other metal oxides is
advantageously utilized in target pollutant removal in the
Pahlman.TM. and other pollutant removals systems and processes.
Target pollutants, such as NOX, SO2, CO, and CO2 gases, mercury
(Hg) and other pollutants, require oxidation of the species prior
to reaction with metal oxide sorbent to form reaction products,
such as metal sulfates, nitrates, and carbonates, mercury
compounds, and other metal salts and corresponding reaction
products, in order for them to be captured and removed from gas
streams.
[0024] Manganese sulfate and nitrate salts are soluble in water,
while manganese oxides are not. During the formation of reaction
products such as manganese nitrates and sulfates, the manganese
present is converted from an insoluble oxide to a soluble metal
salt. This property allows the reaction products formed on the
surface of oxides of manganese sorbent particles to be readily
dissolved and removed from the sorbent particles in aqueous
solutions by disassociation into reaction product anions, such as
sulfate or, nitrate, and manganese cations such as Mn+2 cations.
This property may be advantageously utilized with other metal oxide
sorbents as well.
[0025] Manganese dioxides are divided into three origin-based
categories, which are: 1) natural (mineral) manganese dioxide
(NMD), 2) chemical manganese dioxide (CMD), and 3) electrolytic
manganese dioxide (EMD). As implied, NMD occurs naturally as
various minerals, which may be purified by mechanical or chemical
means. The most common form of NMD is pyrolusite (.beta.-MnO2),
which is inexpensive, but has rather low chemical activity and
therefore low pollutant loading capacity. CMD and EMD varieties are
synthetic oxides of manganese. EMD is produced primarily for the
battery industry, which requires relatively high bulk density
(which often results from relatively large, compact particles),
relatively high purity, and good electrochemical activity. Though
useful as sorbent, characteristics such as low surface area and
large compact particle size make EMD somewhat inferior to CMD for
gas removal applications, despite its good electrochemical
activity. Chemically synthesized oxides of manganese of all kinds
fall into the CMD category and includes chemically treated or
pretreated oxides of manganese. In chemical synthesis, a great deal
of control is possible over physical characteristics such as
particle size and shape, porosity, composition, surface area, and
bulk density in addition to electrochemical or oxidation potential.
It is believed that these characteristics contribute to the loading
capacity of some oxides of manganese.
[0026] Oxides of manganese and other metals have the ability to
capture target pollutants from gas streams, however, the low
pollutant loading rates achieved with various prior art oxides of
metals have made some industrial applications of this
characteristic uneconomical. The low target pollutant loading rates
of various prior art oxides of metal sorbents would require
voluminous amounts to effectively capture large quantities of
target pollutants that exist at many industrial sites, e.g., NOx
and/or SO2. The large quantity of sorbent that would be required to
capture NOx and/or SO2 could result in an overly costly pollutant
removal system and sorbent regeneration system. It would therefore
be desirable to enhance the loading capacities of the oxides of
metal sorbents in order to economically implement a pollution
removal system utilizing oxides of metals.
[0027] Using manganese as an example, it is believed that metal
salt reaction products, such as the manganese salts of Reaction (1)
and Reaction (2) above, form on the surfaces of the sorbent
particles of oxides of manganese. These reactions may extend to
some depth inside the sorbent particles and into the pores and
micro fissures. Applicants believe that formation of such reactions
products occurs primarily on the surfaces of the oxides of
manganese particles, resulting in a layer or coating, which
effectively isolates the covered portion of the particle surface
and thereby prevents continued rapid reaction with additional
target pollutants. Further, the oxidation state and thus the
loading capacity of the oxides of manganese below the surface of
the reaction product coating may be reduced during the pollutant
removal, thus diminishing the loading capacity of sorbent even
after the reaction product have been removed or disassociated into
an aqueous solution. It would therefore be desirable for economic
reasons to re-use or regenerate the unreacted portions of the
sorbent for subsequent cycles of pollutant gas removal.
[0028] In order to regenerate the reacted oxides of manganese
effectively for subsequent re-use as a gas sorbent with high
removal efficiencies and target pollutant loading rates, it is
advantageous to: (1) remove soluble reaction products or reaction
product salts, such as salts MnSO4, Mn(NO3)2, MnCl2 and other
manganese halides, manganese salt reaction products, and the like,
from the sorbent particle surfaces with an aqueous solution through
disassociation into their constituent cations and anions, e.g,
Mn+2, Cl-1 SO4-2, and NO3-1 ions; (2) restore or increase the
target pollutant loading capacity and/or oxidation state of the
remaining solid oxides of manganese sorbent below the surface of
the reaction product coating that is now dissociated in an aqueous
solution, (3) recover, through precipitation, the Mn+2 ions that
were dissociated into solution from the reaction products formed
through reactions with the various target pollutants; and (4) to
recover other ions and form marketable or otherwise useful
by-products. Note that some soluble and insoluble reaction products
may be removed through thermal decomposition.
[0029] Applicants have developed methods of recovering metal values
by converting insoluble metal oxides to soluble metal salts and
recovering the solution so formed. For example, ore deposits or
extracted ore containing metal of interest may be leached either in
situ or after extraction. Applicants can treat this solution of
soluble metal salts to produce oxides of metal useful, amongst
other applications as sorbent for pollutant removal. Oxides of
metal so produced may exhibit high or increased loading capacity
and/or valence states as compared to reacted and virgin oxides of
metal of various forms, including a variety of commercially
available oxides of metal.
[0030] One objective of this invention is to create active metal
oxides by recovering metal values from ore deposits or extracted
ore by converting insoluble metal oxides in the ore to soluble
metal salts and pumping the solution so formed out of the ore,
either in situ or from ore that has been extracted from the earth,
and oxidizing the soluble metal salt through an oxidation
process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a Pourbaix diagram for an aqueous solution of 1
mole/liter manganese ion concentration.
[0032] FIG. 2 is a Pourbaix diagram for an aqueous solution of 10-6
mole/liter manganese ion concentration.
[0033] FIG. 3 is a block flow diagram of a system and process
according to the invention.
[0034] FIG. 4 is a block flow diagram of system and process
according to the invention with electronic controls.
[0035] FIG. 5 is a block flow diagram of system and process
according to the invention with electronic controls.
[0036] FIG. 6 is a block flow diagram of system and process
according to the invention with electronic controls.
[0037] FIG. 7 is a graph plotting SOX loading capacities of oxides
of manganese.
[0038] FIG. 8 is a graph plotting NOX loading capacities of oxides
of manganese.
[0039] FIG. 9 is a graph plotting pH and Eh values relative to
processing times.
[0040] FIG. 10 is a graph plotting pH and Eh values relative to
processing times with and without pH control.
SUMMARY OF THE INVENTION
[0041] The invention relates to systems and processes, for recovery
and precipitation of oxides of metals that have high oxidation
states and/or high pollutant loading capacities which are suitable,
amongst other uses, as a sorbent for capture and removal of target
pollutants from industrial and other gas streams from ore or other
raw material containing impure oxides of the metal.
[0042] In an embodiment of a method of the invention ore containing
a target metal is processed to recover dissociated metal salts
which are precipitated to form oxides of the target metal. The
method of this embodiment comprises the steps of: leaching metal
values from ore to form a solution containing cations and anions of
disassociated metal salts; heating the solution containing cations
and anions of disassociated metal salts; mixing the heated solution
containing cations and anions of disassociated metal salts and a
heated aqueous oxidizing solution in a precipitation vessel to form
a solution mixture, the heated aqueous oxidizing solution being
prepared so as to have Eh and pH values within the metal oxide
stability area of an aqueous solution heated to a temperature at or
near boiling temperature at atmospheric pressure and being heated
to a temperature at or near the boiling temperature; monitoring and
adjusting the temperature, Eh value and pH value of the solution
mixture so as to rapidly move mixture conditions into and to
maintain them within the metal oxide stability area; and
maintaining the solution conditions within the metal oxide
stability area so as to precipitate the metal cations out of
solution as precipitated oxides of metal having loading capacities
and/or oxidation states equal to or greater than that of the metal
oxides in the ore or other raw material.
[0043] In another embodiment of a method, ore containing manganese
is processed to recover dissociated manganese salts which are
precipitated to form oxides of manganese. The method of this
embodiment comprise the steps of: leaching manganese values from
ore to form a solution containing cations and anions of
disassociated manganese salts; heating the solution containing
cations and anions of disassociated manganese salts; mixing the
heated solution containing cations and anions of disassociated
manganese salts and a heated aqueous oxidizing solution in a
precipitation vessel to form a solution mixture, the heated aqueous
oxidizing solution being prepared so as to have Eh and pH values
within the MnO2 stability area of an aqueous solution heated to a
temperature at or near boiling temperature at atmospheric pressure
and being heated to a temperature at or near the boiling
temperature; monitoring and adjusting the temperature, Eh value and
pH value of the solution mixture so as to rapidly move mixture
conditions into and to maintain them within the MnO2 stability
area; and maintaining the solution conditions within the MnO2
stability area so as to precipitate the manganese cations out of
solution as precipitated oxides of manganese having loading
capacities and/or oxidation states equal to or greater than that of
the metal oxides in the ore or other raw material.
[0044] Other embodiments of the invention include the oxides of
metal produced by the above methods. The above methods may further
comprise the step of maintaining solution or solution mixture pH
constant throughout the processing cycle.
[0045] In any of the above methods, the aqueous oxidizing solution
may contain a suitable or compatible oxidant or oxidizer included
but not limited to those selected from the group consisting of
persulfates, chlorates, perchlorates, permanganates, peroxides,
hypochlorites, oxygen, air, and ozone(O3).
[0046] In another embodiment of the invention is a system for rapid
and adaptive recovery of metal values as precipitates of oxides of
metal having loading capacities and/or oxidation states equal to or
greater than that of the metal oxides in the ore or other raw
material, the system comprising; a well bore hole for injecting a
leaching solution; a well bore hole for recovering a solution
containing cations and anions of disassociated metal salts; a
precipitation vessel equipped with probes for measuring
temperature, Eh and pH values of aqueous solutions within the
precipitation vessel, the precipitation vessel being configured for
introduction of a solution containing cations and anions of
disassociated metal salts; a oxidant feeder containing a supply of
aqueous oxidizing solution, the aqueous oxidizing solution being
prepared so as to have Eh and pH values within the metal oxide
stability area for an aqueous solution heated to a temperature at
or near boiling temperature at atmospheric pressure; a heater for
providing heat to the precipitation vessel; a base and/or acid
feeder for feeding base or acid to the precipitation vessel; a
least one filtration and/or rinse unit, which optionally may be
incorporated into and a part of the precipitation vessel; and a
controller for simultaneously monitoring and adjusting system
operational parameters and regulating system components, the
controller being in electronic communication with the probes of the
precipitation vessel, the feeders, the at least one filtration
and/or rinse unit and the heaters; the controller being capable of
monitoring and adjusting system operational parameters selected
from the group consisting of temperature, Eh, pH and feeder rates
so as maintain conditions in the oxidation vessel within the metal
oxide stability area through processing cycles.
DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS
[0047] The methods and systems of the invention each involve and
employ Applicants' recognition that oxides of metal processed in
aqueous; systems in which conditions and parameters are adjusted
and maintained within the metal oxide stability area will yield
oxides of metal having desired pollutant loading capacities and/or
oxidation states. In its various embodiments, the invention and the
methods and systems thereof provide for rapid, adaptive and stable
processing of oxides of metal as compared to the methods and
systems currently know in the art. Oxides of metal thus processed
are suitable for use as a sorbent in dry and wet gaseous pollutant
removal systems and are particularly suitable for use in dry
pollutant removal systems. They may also be utilized in a variety
of commercial, industrial and other applications, unrelated to
pollutant removal, that incorporate or employ oxides of metal.
[0048] The metal values used in the invention are recovered from
raw in situ ore, recovered ore, or from metal oxides in particle
form by a leaching process. Applicants believe that, by way of
non-limiting example, some metals so leached occur naturally in an
insoluble oxide form which is reduced through the use of a reducing
agent, and reacted with an anion to form a soluble metal salt. The
anion may be provided by the reducing agent itself or it may be an
additional element in the leaching solution. Possible leaching
solution active components are water containing dissolved sulfur
dioxide, nitric, nitrous, sulfuric, or sulfurous acids, soluble
salts of hydrosulfite, bisulfite, or metabisulfite or other
chemicals capable of dissolving the metal oxides of interest.
[0049] This leaching process can take place in situ, with the metal
containing ore or nodule still in the earth or sea bed, or with the
ore extracted from the earth previously, or metal oxides in
particulate form, such as those that are commercially available.
Underground mineral leaching involves injecting a leaching solution
into the rock or ore deposit at one point and retrieving it by
known leachate extraction techniques such as pumping it out from a
lower point after the solution has passed through the rock
formation. The leaching solution dissolves some of the metal of
interest, which is recovered as a component of the recovered
solution. Typically a series of injection and recovery holes are
drilled into the formation containing the ore. The leaching
solution is then injected into the formation. Natural fissures in
the rock formation may allow the leaching solution to sub-optimally
pass by some of the mineral bearing ore without penetrating the
formation and recovering the mineral. Therefore the pressure of the
leaching fluid is kept relatively low to avoid fracturing the rock
formation further and increasing this bypass phenomenon.
[0050] The minerals could also be recovered through traditional
open-cut or subterranean mining where the mineral bearing rock is
brought to the surface. The rock may be crushed and the minerals
may then be extracted chemically using similar leaching solutions
and producing similar solutions of metal salts.
[0051] Without being bound by theory or limited by this example,
Applicants believe that the processing of recovered metal oxides
values, such as manganese cations and the precipitation of newly
formed metal oxides, e.g., oxides of manganese in a heated aqueous
oxidizing solution system maintained within the metal oxide
stability area may beneficially affect a number of characteristics
of the metal oxides. Such characteristics include, but are not
limited to, particle size and shape, crystalline structure or
morphology, porosity, composition, surface area (BET), bulk
density, electrochemical or oxidation potential and/or metal
valence states. Some or all of these characteristics affect the
performance of metal oxides of manganese in their various uses and,
particularly, in their use as a sorbent for removal of gaseous
pollutants. With attention to maintaining aqueous system conditions
within the stability area, Applicants have found that they are able
to produce metal oxides, particularly oxides of manganese, having
desirable loading capacities and/or metal valence states.
[0052] The application of these principles can be understood with
reference to the following discussion relative to oxides of
manganese. The stability area for an aqueous system will vary based
upon the conditions of the system and may shift or drift as
reactions in the aqueous system proceed. With oxides of manganese
as an example, changes in dissolved manganese ion concentration,
oxidizer concentration, pH, Eh, solution temperature, and competing
dissolved ions may affect the boundaries of the domain or region of
stability for MnO.sub.2. The aqueous oxidizing solution systems of
the invention are typically at temperatures at or near the boiling
temperature of aqueous solutions at given atmospheric pressures.
The boiling point of aqueous solutions will vary depending upon
elevation and will be different at sea level than at other
elevations. The effects of such changes or different atmospheric
conditions upon the boundaries of the MnO.sub.2 stability area or
other metal oxide stability area on a Pourbaix Eh-pH diagram can be
determined either by empirical data derived from experimentation or
with computer software programs known to those skilled in the art,
such as HSC Chemistry distributed by Outokumpu Oy of Finland.
Software may also be written to determine stability areas as
defined by other diagrams, such as the Latimer Diagram or the Frost
Diagram.
[0053] With reference to FIGS. 1 and 2, impact of system conditions
on the MnO.sub.2 stability area is illustrated with respect to
Pourbaix diagrams for systems at 25.degree. C. and at atmospheric
pressure at sea level. In FIG. 1, the ranges of pH and Eh values
for thermodynamically stable aqueous solutions of various manganese
compounds are illustrated in graph form for aqueous solution
systems at 25.degree. C. and a 1 mole/liter manganese ion
concentration. FIG. 2 similarly illustrates ranges of pH and Eh
values for aqueous solution systems at 25.degree. C. but at a
1.0.times.10-6 mole/liter manganese ion concentration. The Pourbaix
Window diagrams depicted in FIGS. 1 and 2 were derived from the
diagram presented in Atlas Of Electrochemical Equilibria in Aqueous
Solutions," Marcel Pourbaix, pages 286-293, National Association of
Corrosion Engineers, Houston, Tex. The Eh and pH values as plotted
on the graphs delineate the boundaries of the MnO.sub.2 stability
area for each of the two aqueous solution systems, emphasized with
shading in FIGS. 1 and 2. A comparison of the boundaries of the two
shaded areas on FIGS. 1 and 2 is illustrative of the different
stability areas that exist under different system conditions.
[0054] In the methods and systems disclosed herein, the conditions
or parameters of aqueous systems are maintained within the metal
oxide stability area for the target metal oxide valence state with
regard to electrochemical (oxidizing) potential (Eh) range and pH
range at the prescribed system temperature at ambient atmospheric
conditions in order to provide an Eh-pH combination to achieve
stable solution equilibrium, as defined by the stability area as
delineated in, for example, a Pourbaix Window diagram, such as
those depicted in FIGS. 1 and 2.
[0055] In a Pourbaix diagram, the metal oxide stability area is
defined by the thermodynamically stable ranges or boundaries of
pH-Eh combinations that promote the existence and formation of high
valence metal oxides, for example MnO.sub.2 (where manganese has an
average valence state close to +4), as the most thermodynamically
stable form of metal oxide in an aqueous solution system. In the
methods of the invention, the constituents of the aqueous solution
systems are the loaded oxides of metal and their disassociated
metal salts along with the oxidizer or oxidizers in the aqueous
oxidizing solution and the base or acids that may be added thereto.
During processing, aqueous solution system conditions must be moved
to and maintained at or within the boundary area delineated by the
combination of Eh and pH ranges. In order to accomplish this, Eh
and/or pH adjustments must be made through the addition of
oxidizer, base or acid.
[0056] To this end, Applicants utilize a heated aqueous oxidizing
solution to provide the oxidizer or oxidant. The oxidizer, for
example, but not limited to, gaseous oxidizers may also be added
directly to a sorbent slurry or solution contain disassociated
reactions products, though this methodology is not preferred. The
oxidizer must be able to provide the required electrochemical
(oxidizing) potential (Eh) at the specified temperature and within
the specified pH ranges to provide an Eh-pH combination to achieve
stable aqueous solution system equilibrium within the metal oxide
stability area for metal oxides of the target valence state.
Suitable oxidizers to name a few include, but are not limited to,
persulfates, such as potassium peroxidisulfate (K2S2O8), sodium
peroxidisulfate (Na2S2O8), and ammonia peroxidisulfate
((NH4)2S2O8), chlorates, such as sodium chlorate (NaClO3),
perchlorates such as sodium perchlorate (NaClO4), permanganates,
such as potassium permanganate (KMnO4), oxygen (O2) or air, ozone
(O3), peroxides, such as H2O2, and hypochlorites, such as sodium
hypochlorite (NaOCl). Other oxidizers may be selected by those
skilled in the art based upon their compatibility with the metal
oxide and corresponding reaction products. Other oxidizers suitable
for use in the methods of the invention will be apparent to those
skilled in the art; it being understood that the electrochemical
potential (Eh) of the heated aqueous oxidizing solution, and
therefore the effectiveness of the methods of the invention,
depends, in part, upon the strength of the oxidizer and/or the
concentration of the oxidizer in the solution.
[0057] Depending upon the conditions and constituents of the
aqueous solution system, the pH range of the boundary may be
acidic, near neutral, or basic. In short, processing may be carried
out over the full pH spectrum. However, the oxidizer strength or
concentrations required at the extremes of the pH spectrum may make
such processing uneconomic though nonetheless achievable. As the
reactions proceed, metal oxide is being produced and the oxidizer
is being consumed, the system may tend to shift away from the
desired pH range, in which case the addition of a suitable base or
acid will help accomplish the necessary adjustment to maintain the
system within the appropriate Eh-pH range of the metal oxide
stability area. Applicants have found it beneficial to maintain pH
relatively constant during processing. Alternatively, the
introduction of additional oxidizer to bring the system within the
appropriate Eh range as pH drifts or shifts in the aqueous system
may also beneficially accomplish the necessary adjustment. The
aqueous solution system is, and therefore the methods and systems
of the invention are, dynamic and adaptive with necessary
adjustments being made not only by introduction of acid or base but
with introduction of oxidizer as well.
[0058] Examples of useful bases include but are not limited to
alkali or ammonium hydroxides, potassium hydroxides, and sodium
hydroxides. Examples of useful bases include but are not limited to
sulfuric, nitric, hydrochloric and perchloric acid to name a few.
Applicants have found it useful to match the cations of the oxidant
and base. For example, where the oxidant is a persulfate, such as
potassium peroxodisulfate (K2S2O8), the pH could be adjusted with a
compatible or suitable base, such as potassium hydroxide (KOH). If
sodium peroxodisulfate is used (Na2S2O8), a compatible base would
be sodium hydroxide (NaOH); and with ammonium peroxodisulfate
((NH4)2S2O8), ammonium hydroxide ((NH4OH) would be a compatible
base. The acids or bases and other process additives are generally
commercially available and those skilled in the art would be able
to readily identify compatible process additives useful within the
scope of the invention.
[0059] Using manganese as an example, Applicants are able to
achieve stable and controlled precipitation so as to rapidly and
adaptively yield oxides of manganese having equal or increased
loading capacity when compared to the untreated commercially
available EMD and CMD oxides of manganese (NMD, EMD, and CMD) or
when compared to virgin oxides of manganese. At a given pH, Eh and
temperature ranges within the MnO2 stability area, the desired
manganese valence state (theoretically close to +4) will exist.
Thus, there is no propensity for Mn compounds at or close to +4
valence state to degrade to +3 or +2 valence states. However, if
conditions are not maintained within the MnO.sub.2 stability area
such degradation may occur. Applicants have found that oxides of
manganese precipitated from a heated oxidizing solution maintained
within the MnO.sub.2 stability area will exhibit a Mn valence state
of close to +4 and exhibit target pollutant loading capacities
equal to and/or greater than (increased) the loading capacities of
virgin oxides of manganese.
[0060] As further discussed below heated oxidizing: solutions
having the desired pH-Eh-temperature combination can be prepared:
and maintained or adjusted by increasing or decreasing oxidizer,
acid or base concentrations and/or temperature adjustment as
appropriate, so that the conditions are adjusted to remain within
the metal oxide stability area. With monitoring of Eh, pH, and
temperature, an operator can make necessary adjustments in order to
maintain or return the oxidizing solution to conditions within the
metal oxide stability area. Such monitoring and adjusting can also
be automated utilizing electronic probes or sensors and controllers
as discussed later herein below.
[0061] In the various embodiments of the invention disclosed
herein, the systems in which the methods of the invention are
carried out all have common or corresponding components that are
substantially the same. Though referred to, in appropriate
instances by slightly different terms (for purposes of clarity) and
being identified with corresponding but different reference numbers
in the figures and the disclosure herein below, their operation and
function will also be understood to be substantially the same and
equivalent. To the extent that there are operational or functional
differences, they are identified and discussed as appropriate. The
common system components include oxidation vessels in which
regeneration, pretreatment and precipitation are carried out;
agitation devices and probes for temperature, Eh and ph measurement
with which the oxidation vessels are equipped, filtration units,
and rinses. Heaters supply heat to the process streams which enter
the oxidation vessels and the oxidation vessels are also equipped
with a heater (heaters not shown in the figure hereof) for adding
heat to and maintaining the temperature of the solutions in the
vessels. For applications requiring dried oxides of metal, a dryer
would be another common component. And, for applications requiring
the oxides of metal to be comminuted and sized, a comminuting
device would be another common component. These components are
further discussed herein below. It should be understood that
discussion of these components in the first instance with respect
to one embodiment of the invention is equally applicable and
relevant to the components as incorporated into the other
embodiments of the invention. Therefore, in the interest of
efficiency and to avoid undue repetition, the discussion of the
components may not be serially repeated in detail.
[0062] Turning to FIG. 3, a precipitation system 50 is shown. The
recovered metal values in FIG. 3 are introduced or conveyed to
precipitation vessel 54 which is equipped with an agitator 55, also
referred to herein as an agitation means 55. Any of various
agitation devices known to those skilled in the art to be suitable
for agitating, mixing and stirring the solid-liquid slurries so as
to keep the solid oxides of metal particles generally suspended in
the solution can be utilized. As illustrated in FIG. 3, vessel 54
is optionally equipped with temperature, probe 53A, pH probe 53B
and Eh probe 53C. These probes are utilized to measure their
respective parameters in the heated aqueous oxidizing solution and
may be in electronic communication with a controller as later
discussed herein with reference to FIG. 4.
[0063] In the vessel 54, the recovered metal values are mixed with
a heated oxidizing aqueous solution. The heated aqueous oxidizing
solution and the recovered metal value solution are preferably
preheated to temperatures at or near the boiling point of aqueous
solutions at atmospheric pressure or other operational pressure.
The heating of the two constituent solutions prior to mixture
serves to avoid or minimize the precipitation of undesired oxides
of metal and also serves to provide for fairly rapid processing
times. The heated oxidizing solution is so prepared as to have
conditions that move the mixture between it, the acid or base
solution, and the recovered metal value solution toward the metal
oxide stability area. For example, at sea level, this would be
about 100.degree. C. Oxidation and precipitation may be carried out
at temperatures ranging from about 90.degree. C. to about
110.degree. C., with temperatures between 95.degree. C. to about
108.degree. C. being preferred, and temperatures between about
100.degree. C. to about 105.degree. C. being more preferred at sea
level atmospheric pressures. The solution temperature should be
maintained unless a temperature adjustment away from near boiling
is required in order to maintain the aqueous solution system within
the metal oxide stability area as other system parameters shift
during processing. Determining which parameter adjustments to make
is a matter of engineering or operator choice as long as the
adjustment moves system conditions into or maintains those
conditions within the metal oxide stability area.
[0064] For the recovered metal values, the heated aqueous oxidizing
solution provides the required electrochemical (oxidizing)
potential (Eh), within the specified temperature and pH range to
yield metal oxides having pollutant loading capacities and/or
oxidations states equal to or greater than that of the metal oxides
in the ore or other raw material. Under agitation, the slurry
formed in the precipitation vessel 34 as the metal oxides
precipitate is continuously mixed and the pH of the slurry is
adjusted by appropriate means, e.g., addition of acid or base. The
metal oxides are allowed to remain within the slurry for a time
sufficient to achieve an increased oxidation state and/or a target
pollution loading capacity equal or greater than that of virgin
metal oxides. At or near the sea level atmospheric pressures, a
sufficient time may be between about 20 minutes to about 70
minutes, preferably between about 35 minutes to about 55 minutes,
and more preferably between about 40 minutes to about 50 minutes.
Such processing times are rapid compared to the hours and tens of
hours of sometimes staged processing of prior art methods.
Applicants have found that an optimal time for the precipitated
metal oxides to remain in the precipitation vessel (34) is
approximately 45 minutes, during which time the precipitated metal
oxides have their average valence state increased. Manganese
oxides, for example, are oxidized up to valance states close to +4.
A deviation of two to three minutes above or below 45 minutes is
near enough to optimal to provide metal oxides having oxidation
states and/or loading capacities particularly suitable for use as a
sorbent for target pollutant removal. It being understood that with
greater deviations from the optimal time but yet within the above
stated time ranges oxides of manganese suitable pollutant removal
(particularly when high loading capacity is not required) and for
other uses may nonetheless be produced with the invention
[0065] Separation of the precipitated oxides of metal and the
oxidation filtrate is best preformed at close to operating
temperature in precipitation vessel 34, or close to about
100.degree. C. Allowing the solution containing reformed oxides of
manganese and the aqueous oxidizing solution to cool to
temperatures below the solubility temperatures for residual ions in
solution, for example, but not limited to K+1 and SO4-2 can result
in the precipitation of solid salts such as K2SO4. Through
experimentation, it has been recorded that allowing salts to
precipitate with the precipitated oxides of metal sorbent lowers
the target removal efficiency and loading rates and should
therefore be avoided.
[0066] The precipitated metal oxide sorbent is then rinsed with
water to wash away any remaining spectator ions. In FIG. 3 this is
illustrated as two separate steps: 1) filtering and separating the
precipitated oxides of metal from the aqueous oxidizing solution to
provide an oxidation filtrate in filtration unit 56; and 2) rinsing
the sorbent with water to wash away remaining spectator ions in the
sorbent precipitation rinse 57. Any of a variety of suitable
filtration techniques and devices known to those skilled in the art
may be utilized for this purpose. It should be noted that the
filtration and rinsing step could be combined using filtration and
rinsing equipment known to those skilled in the art. Further, the
filtration unit 56 may alternatively be incorporated into and as
part of the precipitation vessel 54.
[0067] The rinsing of the precipitated oxides of metal should be of
sufficient duration and with sufficient volume of water as to
remove dissolved ions associated with the oxidizer, metal salt,
base, and acid in the aqueous oxidizing solution to a suitable
level. The presence of these ions in the precipitated sorbent in
sufficient amounts may negatively impact the loading capacity or
removal efficiency of the precipitated oxides of metal. This is not
to say that precipitated oxides of metal that are not so rinsed
will be ineffective for removal of target pollutants because in
fact they may be so utilized without the rinse and good removal
rates can be achieved. However, the precipitated oxides of metal
may be more efficiently utilized following rinsing.
[0068] Various measurement techniques and devices known to those
skilled in the art can be employed to determine the level or
concentration of such ions in rinse water and thereby determine
whether the oxides of metal have been adequately rinsed. Such
techniques include measurement of conductivity, resistivity, total
dissolve solids (TDS) or other indicators of the level of
disassociated ions and/or dissolved solids and fine particulates in
a solution, such as specific gravity or density or chemical
analysis. By way of example and not limitation, TDS measurements of
the oxidation filtrate taken by Applicants have been in the range
of 80,000-200,000, representing the disassociated ions from the
oxidant, metal salt, base or acid and other possible dissolved
solids or fine particulates associated with the precipitation. The
rinse step should generally being designed to remove such ions,
solids and particulates from the precipitated oxides of metal to an
acceptable level or tolerance. Where precision is required the
vessel or apparatus in which the rinse is carried out should be
equipped with an appropriate measurement device for conductivity,
resistivity, TDS level or other indicator. With monitoring of such
measurements, the rinse step can be carried out until the oxidation
filtrate reaches the desired level based upon the measurement
technique employed. Through a series of precipitation cycles and
use cycles, the acceptable level or tolerance for the given use to
which the precipitated oxide will be put can be determined, as well
as the volume, flow rate and duration of the rinse in order to
establish or standardize operating procedures. Although lowering
the TDS of the filtrate generally favorably impacts target
pollutant removal efficiency and loading rates, Applicants have
found that oxides of metal prepared according to the methods of the
invention may be utilized for target pollutant removal with or
without the rinsing step. Applicants have achieved adequate target
pollutant removal with precipitated oxides of metal that is not
rinsed prior to use as a sorbent, but have seen better removal at
measured TDS levels in the filtrate of less than 100,000 and even
better performance at less than 10,000.
[0069] Returning to FIG. 3, the wet precipitated oxides of metal,
if being utilized in a dry target pollutant removal system such as
the Pahlman.TM. system, is first routed for drying to a dryer 58.
Oxides of metal may be introduced into pollution removal systems as
a dry power, a wet filter cake, or a slurry by a slurry or spray
feeder. In dry removal systems, the wet filter cake and sprayed
slurry may be "flash dried" upon contact with industrial gas
streams which may be introduced at elevated temperatures into the
pollutant removal systems. For such applications the drying step
may not be necessary and the wet or moist filter cake may be
conveyed to a filter cake feeder. Similarly, with slurry or spray
feeders, once adequately rinsed, the precipitated oxides of metal
need not be filtered or separated. Rather, they can be conveyed as
a slurry to the feeder. However, when the oxide of metal sorbent is
to be introduced as a dry particulate or powder, both drying and
comminuting to size of the oxides of metal particles is typically
performed. The dryer 58 may be a kiln or other suitable dryer used
for such purposes and known to those skilled in the art. The dryer
58 may utilize waste heat generated by combustion which is
transferred or exchanged from combustion or process gases at an
industrial or utility plant. When drying is required the
temperature should be below the thermal decomposition temperature
of the oxides of metal but sufficiently high so as to drive off
surface water or moisture without removing any waters of hydration
or water of crystallization. As an illustrative example only,
temperatures around 100.degree. C. to 160.degree. C. have been
found to be adequate for this purpose for manganese oxide. Drying
can be conducted at lower temperatures but drying time may be
uneconomically extended; and at higher temperatures, which can be
utilized in Applicants' invention, short drying time will have to
be closely observed so as to avoid thermal decomposition of the
oxides of metal, driving off structural water, or undesired damage
to the crystalline structure of the oxides of metal.
[0070] Precipitated oxides of metal may be filtered, decanted or
otherwise collected and dried. If further oxidation of the
precipitated oxides of metal is required, the drying step may be
carried out in an oxidizing atmosphere. Alternatively, in
accordance with the methods of the invention, an oxidizer, as
previously described may be introduced into vessel 50 while the
oxides of metal are being formed and precipitated. For example air
or oxygen can be bubbled through or a persulfate or other suitable
oxidizer may be used. In the production of a manganese sorbent, for
example, the newly precipitated oxides of manganese have a valence
state close to 4+ and an oxidation strength in the range of 1.5 to
2.0, preferably 1.7 to 2.0, and has a BET value ranging from about
1 to 1000 m2/gr. With comminuting, oxides of manganese particles
can be sized for industrial and chemical application uses and
particularly a particle size ranging from 0.5 to about 500 microns
and be sent to the sorbent feeder for reuse in removal of target
pollutants.
[0071] Use of acoustic energy during processing particularly during
precipitation may favorably affect the performance of the oxides of
metal produced in the various embodiment of the invention. Acoustic
energy, as applied industrially, includes the range from
ultrasonic, which is short-wave, high-frequency (greater than
20,000 Hz.) energy, to infrasonic, which is long-wave,
low-frequency (less than 20 Hz.) energy. All forms of acoustic
energy are transmitted as pressure waves, and are usually generated
by specialized devices or transducers which convert electricity or
pressurized air into acoustic energy within the desired frequency
range.
[0072] Industrial applications of ultrasonic acoustic energy
include agitation of liquid solutions for applications such as
solvent parts cleaning for example. Infrasonic acoustic energy, for
example, is used to loosen material in dry powder transport
systems, to promote smooth flow and prevent stoppage of the
material, or to remove filter cake from bag-type filters; it is not
typically used in liquid applications. These and other applications
of such technology may also be methods of transferring energy to a
solution, gas, or solid material, without raising its
temperature.
[0073] There are many commercial manufacturers of ultrasonic
equipment such as small or laboratory scale ultrasonic equipment
like those available from the Cole-Parmer Instrument Company and
large scale equipment, such as high pressure and/or high
temperature device available from Misonix.
[0074] With the application of acoustic energy in the form of
ultrasonic or infrasonic waves has improvements in sorbent activity
or loading capacity can be achieved. The application of acoustic
energy during processing of oxides of metal may be doing all or
some of the following actions: (1) enhancing agitation during
sorbent processing to improve reaction rates and enhance mixing;
(2) increasing dissolution rates of chemicals used in the
processing of oxides of metal; (3) altering structural development
of crystal structure during and following precipitation from
solution; and (4) breaking up large oxides of metal crystal
formations. In the methods and systems of the invention, acoustic
energy would be generated by specialized devices or transducers and
directed which may optionally be incorporated into the
precipitation vessel 54. Such sonication devices may be used and
incorporated into other system components, such as oxidant, acid or
base vessels or vessel in which metal salts are mixed with water
prior to precipitation processing.
[0075] Monitoring and adjustment of the conditions of the
precipitation vessels employed in the different embodiments of the
invention are carried out utilizing electronic controls. FIGS. 4-6
illustrate embodiments of the invention incorporating an electronic
controller 67 to provide adaptive integrated simultaneous
monitoring and adjustment of operational parameters, e.g.,
temperature, Eh, and pH, within the oxidations vessels with an
optional feed back loop for checking the loading capacity of the
oxides of metal produced according the methods of the invention. In
FIGS. 4-6, embodiments of the precipitation system are depicted as
being integrated with a pollutant removal system 60 that utilizes
oxides of metal as a sorbent for target pollutant removal.
[0076] The system 60 is presented a representation of pollutant
removal systems in general and it should be understood that the
system 60 could be a wet scrubbing removal system, a dry removal
system or a combination thereof. System 60 as represented includes
a reaction chamber 62 and a sorbent feeder 64 which contains and/or
is configured to feed oxides of metal to the reaction chamber 62.
Depending upon the type of reaction chamber, oxides of metal may be
fed as a dry powder or dry particles, as a slurry, or as a wet
filter cake. Viewed as a representation of a Pahlman.TM. removal
system, a stream of untreated gas containing target pollutants is
shown entering into the reaction chamber 62. In this system 60, gas
and sorbent oxides of metal are introduced into the reaction
chamber 62 and contacted under conditions and for a time sufficient
to effect removal of the target pollutant(s) at a targeted removal
efficiency rate for the target pollutant(s). It should be
understood that the gas and the oxides of metal may be introduced
together or separately into reaction chamber 62, depending upon the
type pollutant removal system and type of reaction chamber
employed. Clean gas, gas from which a target pollutant has been
removed, is shown to be vented from the reaction chamber 62. Loaded
oxides of metal will be removed from the reaction chamber, as dry
reacted sorbent, a filter cake of reacted sorbent or a slurry of
reacted sorbent and conveyed for regeneration and/or precipitation
processing with appropriate handling.
[0077] Described in greater detail, the Pahlman.TM. system may be
viewed as being comprised of a feeder containing a supply of
sorbent or oxides of metal, at least one bag house configured to
receive sorbent and a gas containing target pollutants, such as
those identified herein above. Gas is introduced at temperatures
ranging from ambient temperature to below the thermal decomposition
or liquification temperature of metal salt reaction products formed
between the oxides of metal and the target pollutant. Gases are
introduced into the bag house and contacted with the sorbent for a
time sufficient to effect capture of the target pollutant at a
targeted pollutant capture rate. The target pollutant or pollutants
are captured through formation of the reaction product between the
target pollutant and the sorbent. The system will also include a
controller for simultaneously monitoring and adjusting system
operational parameters. The controller provides integrated control
of system differential pressure and other operational parameters
selected from the including, but not limited to, target pollutant
capture rates, gas inlet temperatures, sorbent feeder rates and any
combinations thereof. Differential pressure within the system is
regulated by the controller so that any differential pressure
across the system is no greater than a predetermined level and the
target pollutant is removed at the targeted pollutant capture rate
set point.
[0078] The system may incorporate more than one reaction zone, both
of which may be bag houses. Alternatively, the system may
optionally incorporate a reaction zone upstream of a bag house into
which gas and sorbent are introduced and subsequently directed to
the bag house. Such optional reaction zones may be selected from
the group of reaction zones that includes a fluidized bed, a
pseudo-fluidized bed, a reaction column, a fixed bed, a moving bed,
a serpentine reactor, a section of pipe or duct and a cyclone or
multi-clone. When two reaction zones are thus connected and the gas
stream contains at least two target pollutants, such as SOx and
NOx, for example, the first target pollutant may be captured or
removed in the first reaction zone or substantially removed in the
first reaction zone and the second target pollutant will be removed
in the second reaction zone. This can be advantageously utilized,
particularly where the two reaction zones are bag houses to capture
a first target pollutant such as SO.sub.x in the first reaction
zone and a second target pollutant such as NO.sub.x in the second
reaction zone. This would allow for separate regeneration of loaded
sorbent having reaction products thereon from reaction between
oxides of metal and a single target pollutant or at least different
target pollutants that are captured in the second bag house. Thus,
if the target pollutants are SO.sub.x and NO.sub.x this would allow
for separate regeneration and filtration of a SO.sub.x loaded
sorbent and NO.sub.x sorbent with their respective reaction product
ions being disassociated into separate pre-oxidation rinses with
the resultant pre-oxidation filtrates also being separately
processed to precipitate out oxides of metal. The respective
precipitation filtrates would then allow for separate production of
sulfate by-products and nitrate by-products.
[0079] With reference to FIG. 4, a precipitation system 30
substantially as depicted in FIG. 3 is illustrated in block flow
and is connected to removal system 60. Precipitation vessel 34 is
equipped with temperature probe 33A, pH probe 33B, and Eh probe
33C; regeneration vessel 14 is equipped with temperature probe 13A,
pH probe 13B, and Eh probe 13C all of which are in electronic
communication with a controller 67. An acid and/or base vessel (not
shown) is configured to feed acid and or base to precipitation
vessel 34 and regeneration vessel 14. An oxidant vessel containing
oxidizing solution (not shown) is configured to feed oxidizing
solution to precipitation vessel 34 and regeneration vessel 14.
Loaded sorbent may conveyed directly from reaction chamber 62 to
regeneration pre-oxidation rinse 12 or it may be directed to a
loaded sorbent vessel (not shown) for holding and subsequently
conveyed to rinse device 12. The pre-oxidation filtrate from rinse
12 is routed to precipitation vessel 34. The recovered metal values
from the metal ore are added to precipitation vessel 34 to provide
make up metal oxide to the system. The rinsed sorbent from
pre-oxidation rinse device 12 is routed to the regeneration vessel
14. The feeders (not shown) of acid and/or base vessel, oxidant
vessel, and loaded sorbent vessels (not shown) are in electronic
communication with the controller 67. The controller 67 is also in
electronic communication with the Eh probe 33C, pH probe 33B, and
temperature probe 33A with which the precipitation vessel 30 is
equipped and Eh probe 13C, pH probe 13B, and temperature probe 13A
with which the regeneration vessel 14 is equipped. As illustrated,
newly precipitated or virgin sorbent from the precipitation vessel
34 and regenerated sorbent from the regeneration vessel 14 is
routed to filtration unit 16 for filtering. The sorbent is further
routed to the rinse device 17 to be further rinsed. Alternatively,
filtration unit 16 and rinse 17 may be combined into one device so
as to remove filtrate and rinse in a combined operation. Also,
sorbent from the precipitation vessel 34 and the sorbent from
regeneration vessel 14 may each have its own filtration device and
processed sorbent rinse device. Sorbent is then routed to the
sorbent dryer 18 As illustrated, sorbent from sorbent dryer 18 is
routed to comminuting device 19 and then to sorbent feeder 64 which
in turn feeds the sorbent to reaction chamber 62. Alternatively,
sorbent from dryer 18 may be routed directly to reaction chamber 62
or to a sorbent storage vessel prior to being directed to the
feeder 64. Reaction chamber 62 is equipped with optional target
pollutant concentration readers or continuous emission monitors
(CEMS) for NOX and SO2, readers 68A and 68B, which are in
electronic communication with controller 67. It should be
understood the reaction chamber 62 may be equipped with other
equivalent readers where different target pollutants are being
captured.
[0080] The controller 67 interfaces with precipitation vessel 34
probes 33A, 33B, and 33C; NOx and SO2 readers 68A and 68B and
oxidant, base and or acid feeders and vessels (not shown) for
measurement and adjustment of operational parameters with in the
vessels 14 and 34. The controller 67 signals the addition of
oxidant, acid, and or base to precipitation vessel 34 based upon
the inputs received from the probes until the desired Eh/pH reading
is obtained prior to addition of the pre-oxidation filtrate into
the precipitation vessel 34. Agitator 35 continuously agitates the
solution. The temperature, pH, and Eh of the precipitation vessel
34 are monitored and adjusted continuously so as to maintain
conditions within the metal oxide stability area.
[0081] The controller 67 similarly interfaces with regeneration
vessel 14 probes 13A, 13B, and 13C; NOX and SO2 readers 68A and 68B
and oxidant, base and or acid feeders and vessels (not shown) for
measurement and adjustment of operational parameters within the
vessel 14. Thus, temperature, pH, and Eh of the aqueous oxidizing
solution in regeneration vessel 14 are monitored and adjusted
continuously so as to maintain conditions within the metal oxide
stability area.
[0082] Precipitation vessel 34 and regeneration vessel 14 may be
run in parallel operation or alternating operation so as to be able
to verify sorbent loading capability using the optional feedback
loop of the controller 67 and probes 68A and 68B.
[0083] The controller 67 contains a programmable logic controller
(PLC) and other hardware components necessary for the operation of
the controller such as a power supply, input and output modules
that would communicate with the probes 33A, 33B, and 33C; probes
13A, 13B, and 13C and/or readers 68A and 68B, and with the oxidant,
base and/or acid feeder and vessels (not shown), and loaded sorbent
feeder (not shown). The controller 67 receives inputs from the
various probes and readers and converts them into ladder logic
language that would be used by an internal proportional integral
derivative (PID) loop to individually and simultaneously monitor
system operational parameters and to reconcile the inputs with
predetermined or computer generated calculated set points for the
operational parameters, such as temperature, and Eh and pH levels.
As determined by computer logic, the controller 67 will send an
output as necessary to any of the feeders of oxidant and base
and/or acid vessels (not shown) signaling a feeder to cycle on or
to change feeder rate so as to maintain or adjust system
operational parameters to within the metal oxide stability area for
either precipitation vessel 34 or regeneration vessel 14. The
controller 67 may also contain an Ethernet card or other component
that allows onsite or offsite remote display and operator interface
and control as needed.
[0084] The controller 67 would be given a start command and direct
the loaded sorbent feeder (not shown) to inject predetermined
amounts of loaded sorbent into the pre-oxidation rinse device 12.
The controller 67 signal injection of a predetermined amount of
oxidizing solution, acid and/or base into the precipitation vessel
34 and regeneration vessel 14 checking and or adjusting the Eh
and/or pH of the solution prior to feeding in the predetermined
amount of pre-oxidation filtrate from the pre-oxidation rinse
device 12 into the precipitation vessel 34 and a predetermined
amount of rinsed sorbent from the pre-oxidation rinse device 12
into the regeneration vessel 14. The Eh of the oxidizing solution
in precipitation vessel 34 and regeneration vessel 14 may be
adjusted by addition of an oxidizer in sufficient quantity as to
raise the Eh to the desired level from an oxidizer vessel (not
shown), containing a supply of oxidizer or aqueous oxidizing
solution. As determined by programmed controller logic, the
controller 67 would also check, based on inputs received from the
precipitation vessel 34 probes 33A, 33B, and 33C; and regeneration
vessel 14 probes 13A,13B, and 13C and/or adjust the conditions of
the precipitation vessel 34 and regeneration vessel 14 by adjusting
the temperature utilizing a heater: or heat exchanger (not shown)
to increase or decrease solution temperature; the pH, if needed, by
increasing or decreasing the rate of base or acid feed; and the Eh,
if needed, by increasing or decreasing the oxidizer concentration
of the aqueous oxidizing solution. An optional, final quality
control loop is provided utilizing the readers 68A and 68B checking
the loading performance of the processed oxides of metal sorbent by
sending, for example, SOx and NOx readings back to the controller
67. As determined by controller logic, the controller 67 would then
adjust the precipitation vessel 34 and regeneration vessel 14
parameters, if needed, to provide precipitated oxides of metal and
regenerated oxides of metal, respectively, capable of removing
target pollutants at the targeted removal rates. The same
controller may also be used to control the entire operation of the
removal system 60, the regeneration system 10 and the precipitation
system 34 and their components as discussed above including,
pre-oxidation rinse 12, filtration unit 16, rinse device 17, dryer
18, comminuting device 19, sorbent feeder device 64 and the
by-products processing vessel 66, or separate controllers may be
provided.
[0085] With reference to FIG. 5, the regeneration and precipitation
system 20 is depicted as integrated with removal system 60. The
controller 67 will be in electronic communication with the probes
of a single oxidation vessel, vessel 24; otherwise, the operation
and function of the electronic control and communication is
substantially the same as described above with respect to FIG. 4.
With reference to FIG. 6, this is equally applicable to the
integration of systems 30 and 60 to the electronic communication
and control of the corresponding system components. Note that a
variation of regeneration and precipitation method is illustrated.
In FIG. 6, reacted sorbent is rinsed and filtered and routed to
dryer 18. It is not direct to a regeneration vessel but the
pre-oxidation filtrate is routed to precipitation vessel 34 where
precipitation is carried out as previously described. This
variation of the method of the invention can be used where the
loading capacity oxides of metal below the reaction product surface
coating on the sorbent particles has not been significantly
diminished during pollutant removal as to require chemical
regeneration. In such cases, it is sufficient to wash away the
reaction products, dissolving and disassociating them into the
rinse solution or pre-oxidation filtrate and the rinse oxides of
metal can then be dried and comminuted if necessary prior to be
reused to capture target pollutants. Applicants have found SOX to
be one such target pollutant; and that where the gas stream
contains primarily concentrations of this pollutant a rinsing is
all that is required prior to reuse of the rinsed sorbent, with
recover of reaction product ions through precipitation and other
processing.
[0086] Two examples are provided to illustrate the precipitation of
oxides of manganese utilizing the methods of the applicants'
invention. The examples are provided for illustration purposes and
not intended to narrow the scope of the applicants' invention. Both
examples 1 and 2 use manganese sulfate (MnSO4*H2O) as the Mn+2
salt, potassium persulfate (K2S2O8) as the oxidizing agent, and
potassium hydroxide (KOH) as the compatible pH adjusting base. The
two examples serve to illustrate precipitation from leachate.
Example 1 outlines procedures to produce lab quantities (100 grams)
of virgin oxides of manganese sorbent with Example 2 outlining
large industrial quantities (50 pounds) of virgin oxides of
manganese sorbent. FIG. 3, can be referenced in both examples 1 and
2.
EXAMPLE 1
[0087] Turning now to precipitation example 1, in the precipitation
vessel, 169 grams (1 mole) of MnSO4*H2O and 750 milliliters of
water were mixed and heated to 100.degree. C. In the oxidant
vessel, 376 grams (1.4 moles) of K2S2O8 and 1000 milliliters of
water were mixed and heated to 80.degree. C. The oxidizing solution
was rapidly added to the manganese salt solution in the
precipitation vessel and vigorously stirred while the solution was
quickly heated to boil and maintained at not less than 100.degree.
C. Immediately following addition of oxidant to the precipitation
vessel, potassium hydroxide (20% KOH) was added with an
adjustable-flow fluid pump for the purpose of controlling the pH of
the solution at a target pH level of 1.85, within 0.02 pH units.
Solution pH and Eh readings during the course of the precipitation
reaction are presented in FIG. 9. The precipitation vessel was
continually mixed and the temperature maintained at not less than
100.degree. C. for 45 minutes after the combined solutions of
manganese sulfate and potassium persulfate reached a boil.
Following the 45 minute reaction time, the slurry solution was
poured into a Beuchner funnel equipped with a No.5 Whatman filter
paper for vacuum filtration to separate the newly precipitated
oxides of manganese from the clear oxidation filtrate. The
precipitated sorbent was then rinsed with clean water until
filtrate total dissolved solids (TDS) was approximately 1000 ppm.
The filter cake was then placed in an electric oven and dried at
127.degree. C. for 9 hours. The dried oxides of manganese was then
de-agglomerated and passed through an 80 mesh sieving screen.
[0088] Upon analysis of the newly precipitated oxides of manganese
from example 1, both physical and chemical characteristics were
determined and target pollutant loading rate testing was preformed.
The average particle size was found to be 91.2 microns, with a
range of 0.3 to 250 microns. The bulk density was measured to be
0.202 grams/cc with a true specific gravity of 4.246 grams/cc. The
precipitation resulted in oxides of manganese with an extremely
large surface area. Surface area (BET) was measured to be 271
m2/gram. Contributing to the large surface area, would be the
average pore volume, measured to be 0.984 cm2/gram and the average
pore diameter, which was found to be 0.0145 microns. Chemical
composition analysis was also conducted and the % by weight
constituents were measured as follows. 52.1% manganese (Mn), 3.82%
potassium (K), 16.4% structural water (H2O), 4.3% adsorbed water
(H2O), and the balance, determined by difference, to be 23.38%
oxygen (O).
[0089] Oxides of manganese having the formula MnOX where X is about
1.5 to about 2.0 are particularly suitable for dry removal of
target pollutants from gas streams. However, the most active types
of oxides of manganese for use as a sorbent for target pollutant
removal usually have the formula MnO1.7 to 1.95, which translates
into manganese valence states of +3.4 to +3.9, as opposed to the
theoretical +4.0 state. Upon analysis, it was found that the newly
precipitated oxides of manganese sorbent created in example 1
exhibits a valance state of 3.52, which translates into:
MnO1.76.
EXAMPLE 2
[0090] In example 2, a 50 pound quantity of newly precipitated
oxides of manganese sorbent was prepared. Precipitation of the 50
pound batch was conducted following the same techniques and
procedures as the 100 gram precipitation outlined in example 1 and
the pH and Eh values during the precipitation are illustrated in
FIG. 9, with the exception being the target pH level set point and
the strength of the KOH solution. In the precipitation vessel, 84.5
lbs of MnSO4*H2O and 45 gallons of water were mixed and heated to
100.degree. C. In the oxidant vessel, 188 lbs of K2S2O8 and 60
gallons of water were mixed and heated to 80.degree. C. Immediately
following addition of oxidant to the precipitation vessel,
potassium hydroxide (for example 2, 46% KOH) was added with an
adjustable-flow fluid pump for the purpose of controlling the pH of
the solution at a target pH level of 3.5, within 0.02 pH units. The
remaining oxides of manganese precipitation steps were conducted
exactly as with example 1, just on a larger scale. For example 2, a
one cubic foot capacity membrane filter press was utilized to both
filter the precipitate from the oxidation filtrate and to rinse the
newly precipitated oxides of manganese with clean water to obtain
the desired level of filtrate TDS.
[0091] Upon analysis of the newly precipitated oxides of manganese
from example 2, both physical and chemical characteristics were
determined and target pollutant loading rate testing was preformed.
The average particle size was found to be 92.5 microns, with a
range of 0.2 to 300 microns. The bulk density was measured to be
0.404 grams/cc with a true specific gravity of 3.5 grams/cc. The
precipitated oxides of manganese of example 2 was produced using a
higher pH set point of 3.5, resulting in precipitated oxides of
manganese with a higher surface area than was produced with a pH
set point of 1.85, as in example 1. Surface area (BET) was measured
to be 312 m2/gram. Average pore volume was measured to be 0.640
cm2/gram and the average pore diameter was found to be 0.0082
microns. Chemical composition analysis was also conducted and the %
by weight constituents were measured as follows: 48.9% manganese
(Mn), 6.81% potassium (K), 18.0% structural water (H2O), 1.0%
adsorbed water (H2O), and the balance, determined by difference, to
be 25.29% oxygen (O). Additionally, upon analysis, it was found
that the newly precipitated oxides of manganese sorbent created in
example 2 exhibited a valance state of 3.54, which translates into:
MnO1.77.
[0092] Without being limited by belief or theory, Applicants
believe, based upon the chemical composition data for precipitation
Examples 1 and 2, that the oxides of manganese compound formed may
be a mixture of cryptomelane (KMnO8O16), potassic manganese dioxide
monohydrate (K)MnO2*H2O, and/or potassic vernadite ((K)MnO2*yH2O).
Regardless of the actual chemical designation, applicants have
found the resulting oxides of manganese species to be useful to
exhibit high loading capacities for target pollutant capture or
removal.
[0093] Applicants conducted a series of lab-scale tests utilizing a
live slipstream of an actual exhaust gas from a coal-fired
combustion source in order to demonstrate the increased loaded
capacity achieved with the invention as compared to loading
capacity of commercially available oxides of manganese. Manganese
dioxides are divided into three origin-based categories, which are:
1) natural (mineral) manganese dioxide (NMD), 2) chemical manganese
dioxide (CMD), and 3) electrolytic manganese dioxide (EMD). As
implied, NMD occurs naturally as various minerals, which may be
purified by mechanical or chemical means. The most common form of
NMD is pyrolusite (.beta.-MnO2), which is inexpensive, but has
rather low chemical activity and therefore low pollutant loading
capacity. CMD and EMD varieties are synthetic oxides of manganese.
EMD is produced primarily for the battery industry, which requires
relatively high bulk density (which often results from relatively
large, compact particles), relatively high purity, and good
electrochemical activity. Though useful as sorbent, characteristics
such as low surface area and large compact particle size make EMD
somewhat inferior to CMD for gas removal applications, despite its
good electrochemical activity. Chemically synthesized oxides of
manganese of all kinds fall into the CMD category and includes
chemically treated or pretreated oxides of manganese. In chemical
synthesis, a great deal of control is possible over physical
characteristics such as particle size and shape, porosity,
composition, surface area, and bulk density in addition to
electrochemical or oxidation potential. It is believed that these
characteristics contribute to the loading capacity of some oxides
of manganese.
[0094] A glass reactor designed to mimic the gas-solid interactions
known to be present in the reaction zones of a Pahlman.TM. dry
target pollutant removal system was utilized for the tests. The
glass reactor was a vertically positioned Pyrex.TM. glass cylinder
having an internal diameter of 2 inches and a length of
approximately 18 inches. For each test run, 25.0 grams of oxides of
manganese were suspended in the reactor using a permeable fritted
glass filter positioned approximately 4 inches from the bottom of
the reactor, allowing for flow of the gas stream through the
reactor while keeping the oxides of manganese suspended. The test
reactor was insulated and configured with thermocouples for
temperature readings and heating elements for temperature control
to maintain a temperature set point, which in the purposes of the
conducted testes was 280.degree. F.
[0095] A NOx and SO2 laden gas stream was pumped into the bottom of
the test reactor at a flow rate which provided adequate
fluidization of the bed of sorbent to promote optimal gas/solids
contact. The reactor was heated during the testing to 280.degree.
F. and the gas flow rate was metered at a constant 6.5 liters per
minute (1 pm). The slipstream of actual exhaust gas was from a 570
MW tangentially-fired coal-burning boiler operating on Powder River
Basin (PRB) western coal.
[0096] The composition of the exhaust gas was measured both on the
inlet and outlet of the test reactor with appropriate gas
analyzers, as one skilled in the art would employ and for the test
run examples presented found to be within the following ranges:
Oxygen (O2) 5.8-6.5%, carbon dioxide. (CO2) 10-12%, oxides of
nitrogen (NOx) 237-300 ppm, sulfur dioxide (SO2) 207-455 ppm. The
composition of the inlet gas to the test reactor varied slightly
from test to test, therefore the data was normalized and presented
as pounds (1 bs) of NOx or SO2 into and out of the test reactor.
The extent of NOx and SO2 loading was then calculated to determine
the increased sorbent loading capacity of the precipitated sorbent
as compared to commercially available oxides of manganese. The
slipstream of the NOx and SO2 laden gas stream was passed through
the fluidized bed of oxides of manganese, where the flow carried a
portion of the sorbent up onto a sintered metal filter, thus
creating a filter cake, which mimics a bag house reaction chamber
of a Pahlman.TM. dry target pollutant removal system.
[0097] SO2 and NOX concentrations were measured continuously
alternating from the reactor inlet and outlet utilizing a
continuous emissions monitoring system (CEMS). SO2 concentrations
were measured utilizing a Bovar Western Research model 921NMP
spectrophotometric instrument and NOX concentrations were measured
utilizing a Thermo Electron model 42H chemiluminescent instrument.
In order to obtain accurate and reliable emission concentrations,
sampling and reporting was conducted in accordance with US EPA
Reference CFR 40, Part 60, Appendix A, Method 6C. Inlet gas
temperature was 280.degree. F., with a differential pressure across
the permeable fritted glass filter of 2" of water. FIGS. 8 and 7
show the results of comparative loading rate test runs of four
different virgin oxides of manganese samples conducted utilizing 25
g each of: two commercially available forms EMD, CGM, and two forms
precipitated utilizing methods of the applicants' invention.
[0098] FIG. 8 shows the NOx loading curves. Looking now at FIG. 8,
EMD type oxides of manganese was at least achieving 90% NOx removal
on a ppm basis for 12 minutes, during which time an accumulative
total of 0.0451 grams of NOx entered into the laboratory test
reactor with only 0.0029 grams of NOx exiting the reactor, for a
total of 0.0422 grams of NOx being captured by the virgin EMD type
oxides of manganese sorbent. CMD type oxides of manganese was at
least achieving 90% NOx removal on a ppm basis for 27 minutes,
during which time an accumulative total of 0.1157 grams of NOx
entered into the laboratory test reactor with only 0.0034 grams of
NOx exiting the reactor, for a total of 0.1123 grams of NOx being
captured by the virgin CMD type oxides of manganese sorbent.
Precipitated sorbent example 1, which was previously described in
this application, achieved 90% NOx removal on a ppm basis for 102
minutes, with an accumulative total of 0.4372 grams of NOx entering
the laboratory test reactor with only 0.0067 grams exiting, for a
total of 0.4305 grams of NOx being captured by the oxides of
manganese sorbent precipitated according to methods of the
applicants invention. The second example provided (example 2)
achieved 90% NOx removal on a ppm basis for 181 minutes, with an
accumulative total of 0.6801 grams of NOx entering the laboratory
test reactor with only 0.0125 grams exiting, for a total of 0.6676
grams of NOx being captured by the oxides of manganese precipitated
in example 2, detailed previously in this application. From the
provided graph in FIG. 8 and the NOx loading rates provided,
applicants have illustrated the ability of the oxides of manganese
precipitated according to this invention to exhibit substantially
improved NOx loading rates, as compared to commercially available
oxides of manganese
[0099] FIG. 7 shows the SO2 loading curves. Looking now at FIG. 7,
EMD type oxides of manganese was at least achieving 99% SO2 removal
on a ppm basis for 18 minutes, during which time an accumulative
total of 0.0999 grams of SO2 entered into the laboratory test
reactor with only 0.0009 grams of SO2 exiting the reactor, for a
total of 0.0990 grams of SO2 being captured by the virgin EMD type
oxides of manganese sorbent. CMD type oxides of manganese was at
least achieving 99% SO2 removal on a ppm basis for 36 minutes,
during which time an accumulative total of 0.2022 grams of SO2
entered into the laboratory test reactor with only 0.0011 grams of
SO2 exiting the reactor, for a total of 0.2011 grams of SO2 being
captured by the virgin CMD type oxides of manganese sorbent.
Precipitated sorbent example 1, which was previously described in
this application, achieved 99% SO2 removal on a ppm basis for 120
minutes, with an accumulative total of 0.5082 grams of SO2 entering
the laboratory test reactor with only 0.0016 grams exiting, for a
total of 0.5066 grams of SO2 being captured by the oxides of
manganese sorbent precipitated according to methods of the
applicants invention. The second example provided (example 2)
achieved 99% SO2 removal on a ppm basis for 214 minutes, with an
accumulative total of 1.6984 grams of SO2 entering the laboratory
test reactor with only 0.0096 grams exiting, for a total of 1.688
grams of SO2 being captured by the oxides of manganese precipitated
in example 2, detailed previously in this application. From the
provided graph in FIG. 7 and the SO2 loading rates provided,
applicants have illustrated the ability of the oxides of manganese
precipitated according to this invention to exhibit substantially
improved loading rates for SO2, as compared to commercially
available oxides of manganese
[0100] The data from the lab-scale tests presented in FIGS. 8 and 7
illustrate the increased loading capacity for target pollutants NOx
and SO2 that is achievable with the methods of the applicants'
invention. Additionally, FIGS. 8 and 7 serve to illustrate the
differential loading rates of target pollutants, specifically NOx
and SO2. Looking at the loading rates of oxides of manganese
precipitated in example 1, the loading rate for SO2 is
approximately 2.5 times the loading rate of NOx by weight; with SO2
in example 1 precipitated sorbent capturing 1.688 grams of SO2 at a
99% removal rate and 0.6676 grams of NOx at a 90% removal rate. The
differential loading rates for NOx and SO2 are believed to be
indicative of the reaction kinetics of the removal process when, in
this example, oxides of manganese are used as a sorbent.
[0101] FIG. 9 contains the ph and Eh values through time for
precipitation of oxides of manganese reactions, as outlined above
in examples 1 and 2. In both cases the pH was held constant at the
pH set point for the duration of the approximate 45 minute
production time. As is illustrated in example 1, where the pH set
point of 1.85 was reached within two minutes of the solution
reaching 100.degree. C., the Eh increased from 1150 to about 1380
within about 12 minutes. The Eh remained at about 1380 for the
remainder of the 45 minute reaction time. By contrast example 2,
where the pH set point of 3.5 was reached within two minutes of the
solution reaching 100.degree. C., the Eh increased to a lower value
of 1325 within about 10 minutes. Both examples 1 and 2 were
conducted with the same ratio of oxidant to manganese sulfate and
the pH set point resulted in differing Eh solution values. The data
presented in FIG. 9 serves to further illustrate the applicants'
concept of adjusting the solution composition to produce oxides of
manganese within the MnO2 stability window that exhibit increased
target pollutant loading rates and how the MnO2 stability window
will change as one moves through the possible pH range
[0102] As indicated above, Applicants have found it beneficial to
maintain pH constant throughout processing according to the methods
of the invention. FIG. 9 plots ph and Eh values through time for
precipitation of oxides of manganese reactions for Examples 1 and 2
above. In both cases after the aqueous oxidizing solution reached
operating temperatures and an equilibrium point within the MnO2
stability-area, the pH was held constant at the pH set point for
the duration of the approximate 45 minute production time. With
respect to Example 1, where the pH set point of 1.85 was reached
within two minutes of the solution reaching 100.degree. C., the Eh
increased from 1150 to about 1380 within about 12 minutes. The Eh
remained at about. 1380 for the remainder of the 45 minute reaction
time. By contrast in Example 2, where the pH set point of 3.5 was
reached within two minutes of the solution reaching 100.degree. C.,
the Eh increased to a lower value of 1325 within about 10 minutes.
Both Examples 1 and 2 were conducted with the same ratio of oxidant
to manganese sulfate; however, their respective pH set points
resulted in differing Eh solution values. The data presented in
FIG. 9, serves to further illustrate the Applicants' concept of
adjusting and maintaining the solution conditions to produce oxides
of manganese within the MnO2 stability area that exhibit increased
target pollutant loading rates and/or valences stats and how the
MnO2 stability area will change as one moves through the possible
pH range
[0103] Applicants have found that by not holding the pH constant
during the regeneration, pretreatment and precipitation methods of
the invention, the solution Eh value will tend to decrease. This
decrease in Eh can move the solution outside of the MnO2 stability
area, and result in oxides of manganese with diminished target
loading rates and/or diminished valence states. Rather than
maintaining pH constant, additional oxidizer could be required to
maintain sufficient Eh levels as to remain within the MnO2
stability area. FIG. 10, presents the pH and Eh values for
precipitation reactions where: 1) the pH is controlled at a
constant set point of 1.85 (Example 1) for the duration of the
reaction and 2) the pH is uncontrolled, or allow to exhibit a
greater swing throughout the reaction. The resulting solution Eh
value for the uncontrolled case is approximately 50 millivolts
below the controlled case, but additionally the controlled case
reached its stable Eh value at about 12 minutes where the
uncontrolled case took about 19 minutes to reach its stable Eh
value. One possible result of the decreased solution Eh and the
loss of time at the stable Eh condition would be to move the
solution outside of the MnO2 stability area, producing oxides of
manganese with decreased target pollutant loading rates or to
require additional reaction time, which could negatively affect the
overall economics of the regeneration, pretreatment, or
precipitation process. Applicants utilize their system for
electronic process controls (discussed in this application) to
avoid such negative impacts.
[0104] While exemplary embodiments of this invention and methods of
practicing the same have been illustrated and described, it should
be understood that various changes, adaptations, and modifications
might be made therein without departing from the spirit of the
invention and the scope of the appended claims.
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