U.S. patent application number 13/837221 was filed with the patent office on 2017-08-10 for system and method for controlling one or more process parameters associated with a combustion process.
This patent application is currently assigned to Babcock & Wilcox Power Generation Group, Inc.. The applicant listed for this patent is BABCOCK & WILCOX POWER GENERATION GROUP, INC.. Invention is credited to Shannon R. Brown, Daniel B. Johnson.
Application Number | 20170227216 13/837221 |
Document ID | / |
Family ID | 51164199 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170227216 |
Kind Code |
A9 |
Johnson; Daniel B. ; et
al. |
August 10, 2017 |
SYSTEM AND METHOD FOR CONTROLLING ONE OR MORE PROCESS PARAMETERS
ASSOCIATED WITH A COMBUSTION PROCESS
Abstract
The present invention relates generally to the generation of
steam via the use of a combustion process to produce heat and, in
one embodiment, to a device, system and/or method that enables one
to control one or more process parameters of a combustion process
so as to yield at least one desirable change in at least one
downstream parameter. In one embodiment, the present invention is
directed to a system and/or method for controlling at least one
process parameter of a combustion process so as to yield at least
one desirable change in at least one downstream process parameter
associated with one or more of a wet flue gas desulfurization
(WFGD) unit, a particulate collection device and/or control of
additives thereto and/or a nitrogen oxide control device and/or
control of additives thereto and/or additives to the system.
Inventors: |
Johnson; Daniel B.; (Orland
Park, IL) ; Brown; Shannon R.; (Doylestown,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BABCOCK & WILCOX POWER GENERATION GROUP, INC. |
Barberton |
OH |
US |
|
|
Assignee: |
Babcock & Wilcox Power
Generation Group, Inc.
Barberton
OH
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20140196639 A1 |
July 17, 2014 |
|
|
Family ID: |
51164199 |
Appl. No.: |
13/837221 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13832065 |
Mar 15, 2013 |
9457316 |
|
|
13837221 |
|
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|
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61752167 |
Jan 14, 2013 |
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61671007 |
Jul 12, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 31/12 20130101;
B01D 53/504 20130101; B01D 2251/2062 20130101; B03C 3/68 20130101;
F23J 2215/20 20130101; B01D 53/346 20130101; F23J 15/02 20130101;
B01D 2258/0283 20130101; B03C 3/017 20130101; B03C 3/013 20130101;
G01N 31/005 20130101; B01D 2251/404 20130101; F23J 2219/40
20130101; G01N 1/22 20130101; G01N 33/1846 20130101; B01D 53/8631
20130101; B03C 2201/24 20130101 |
International
Class: |
F23J 15/02 20060101
F23J015/02 |
Claims
1. A method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: (I) measuring, analyzing and/or
controlling at least one parameter selected from: (a) the type
and/or amount of fuel to be combusted in the combustion process;
(b) the oxidation air flow rate to the combustion process; (c) the
ammonia slip across the selective catalytic reduction unit; (d) the
nitrogen oxide output from a selective catalytic reduction unit;
(e) the particulate control and/or capture device; (f) the mercury
speciation in the flue gas and/or absorber tank; (g) the selenium
speciation in the flue gas and/or absorber tank; (h) the chemistry
in the flue gas and/or absorber tank of the WFGD; (i) the oxidation
reduction potential of the absorber tank of the WFGD; (j) the
amount of the suspended solids in the absorber tank of the wet flue
gas desulfurization unit; (k) the analysis of the limestone and/or
lime utilized in the wet flue gas desulfurization unit; (l) the
amount of various reagents supplied to the wet flue gas
desulfurization unit tower; (m) the SO.sub.2 concentration at the
flue gas inlet of the wet flue gas desulfurization unit; (n) the
inlet opacity of the wet flue gas desulfurization unit; (o) the PI
data from the wet flue gas desulfurization unit; (p) the amount of
dissolved solids in the wet flue gas desulfurization unit; and/or
(q) the relative saturation of the gypsum crystals in the wet flue
gas desulfurization unit; (II) generating data from the at least
one parameter of Step (I); (III) using the data generated in Step
(II) to adjust at least one operational parameter selected from:
(A) the operational wet flue gas desulfurization unit tower level;
(B) the reagent feed flow to the wet flue gas desulfurization unit;
(C) the oxidation air flow to the wet flue gas desulfurization
unit; (D) the rate of absorber bleed from the wet flue gas
desulfurization unit; (E) the liquid to gas ratio in the wet flue
gas desulfurization unit tower; (F) the number of operating
absorber recycle pumps in the wet flue gas desulfurization unit;
(G) the dewatering operation parameters; (H) the ammonia feed rate
to the selective catalytic reduction unit; (I) the gypsum purity;
(J) the gypsum-related scale formation in the wet flue gas
desulfurization unit absorber tower; (K) the parasitic power loss
by the wet flue gas desulfurization unit equipment; (L) the
oxidation-reduction potential in the absorber recirculation tank;
(M) the wet flue gas desulfurization unit effluent stream waste
water treatment parameters; (N) the SO.sub.2 removal efficiency by
the wet flue gas desulfurization unit; (O) the relative saturation
of the gypsum crystals in the slurry; and/or (P) the total
dissolved solids in the wet flue gas desulfurization unit.
2. A method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: (i) measuring, analyzing and/or
controlling at least one parameter in real time selected from: (a)
the type and/or amount of fuel to be combusted in the combustion
process; (b) the oxidation air flow rate to the combustion process;
(c) the ammonia slip across the selective catalytic reduction unit;
(d) the nitrogen oxide output from a selective catalytic reduction
unit; (e) the particulate control and/or capture device; (f) the
mercury speciation in the flue gas and/or absorber tank; (g) the
selenium speciation in the flue gas and/or absorber tank; (h) the
chemistry in the flue gas and/or absorber tank of the WFGD; (i) the
oxidation reduction potential of the absorber tank of the WFGD; (j)
the amount of the suspended solids in the absorber tank of the wet
flue gas desulfurization unit; (k) the analysis of the limestone
and/or lime utilized in the wet flue gas desulfurization unit; (l)
the amount of various reagents supplied to the wet flue gas
desulfurization unit tower; (m) the SO.sub.2 concentration at the
flue gas inlet of the wet flue gas desulfurization unit; (n) the
inlet opacity of the wet flue gas desulfurization unit; (o) the PI
data from the wet flue gas desulfurization unit; (p) the amount of
dissolved solids in the wet flue gas desulfurization unit; and/or
(q) the relative saturation of the gypsum crystals in the wet flue
gas desulfurization unit; (ii) generating real-time data from the
at least one parameter of Step (I); (iii) using the real-time data
generated in Step (ii) to adjust at least one operational parameter
selected from: (A) the operational wet flue gas desulfurization
unit tower level; (B) the reagent feed flow to the wet flue gas
desulfurization unit; (C) the oxidation air flow to the wet flue
gas desulfurization unit; (D) the rate of absorber bleed from the
wet flue gas desulfurization unit; (E) the liquid to gas ratio in
the wet flue gas desulfurization unit tower; (F) the number of
operating absorber recycle pumps in the wet flue gas
desulfurization unit; (G) the dewatering operation parameters; (H)
the ammonia feed rate to the selective catalytic reduction unit;
(I) the gypsum purity; (J) the gypsum-related scale formation in
the wet flue gas desulfurization unit absorber tower; (K) the
parasitic power loss by the wet flue gas desulfurization unit
equipment; (L) the oxidation-reduction potential in the absorber
recirculation tank; (M) the wet flue gas desulfurization unit
effluent stream waste water treatment parameters; (N) the SO.sub.2
removal efficiency by the wet flue gas desulfurization unit; (O)
the relative saturation of the gypsum crystals in the slurry;
and/or (P) the total dissolved solids in the wet flue gas
desulfurization unit.
3. A method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: controlling, measuring and/or
analyzing at least one process parameter of a combustion process
and/or at least one combustion process air quality control system
in order to yield at least one data set; using the at least one
data set to effect a desirable change in at least one downstream
process parameter associated with one or more of a wet flue gas
desulfurization unit, a particulate collection device and/or a
nitrogen oxide control device.
4. A method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: controlling, measuring and/or
analyzing at least two process parameters of a combustion process
and/or at least one combustion process air quality control system
in order to yield at least one data set; using the at least two
data sets to effect a desirable change in at least one downstream
process parameter associated with one or more of a wet flue gas
desulfurization unit, a particulate collection device and/or a
nitrogen oxide control device.
5. A method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: measuring, analyzing and/or
controlling at least one parameter selected from: (i)
desulfurization tower load; (ii) oxidation air flow rate; (iii) one
or more boiler parameters; (iv) one or more selective catalytic
reduction unit parameters; and/or (v) one or more electrostatic
precipitator parameters; generating data from the at least one
parameter of the previous Step; and using the data generated in the
previous Step to adjust at least one operational parameter selected
from: (a) one or more gypsum production properties and/or
parameters; (b) the oxidation-reduction potential in the absorber
recirculation tank; (c) the pH of the absorber recirculation tank
solution; (d) the concentration, type and/or speciation of one or
more compounds and/or ions in the absorber recirculation tank
solution; and/or (e) the concentration, type and/or speciation of
one or more oxidizer compounds and/or ions in the absorber
recirculation tank solution and/or the wet flue gas desulfurization
unit.
6. The method of claim 5, wherein the method includes a step of
adding at least one of SO.sub.3 or trona to an electrostatic
precipitator and controlling the amount of such one or more
compounds to the electrostatic precipitator so as to reduce the
amount of sparking that occurs in an electrostatic precipitator
while injecting one or more of SO.sub.3 or trona versus the amount
of sparking that occurs without such injection.
7. The method of claim 5, wherein the method includes a step of
controlling the amount of sparking that occurs in an electrostatic
precipitator so as to reduce the concentration and/or type of one
or more oxidizers that are formed as a result of the sparking.
8. The method of claim 5, wherein the method includes a step of
controlling the amount of sparking that occurs in an electrostatic
precipitator so as to reduce the concentration and/or type of one
or more oxidizers that are formed in the electrostatic
precipitator.
9. The method of claim 8, wherein the one or more oxidizers that
are controlled are selected from persulfate, permanganate,
manganate, ozone, hypochlorite, chlorate, nitric acid, iodine,
bromine, chlorine, fluorine, or combinations of any two or more
thereof.
10. The method of claim 5, wherein the method permits control of
both the oxidation-reduction potential and the pH in the solution
of an absorber recirculation tank.
11. The method of claim 10, wherein the oxidation-reduction
potential in the solution of an absorber recirculation tank is less
than about 500 mV and the pH is less than about 7.
12. The method of claim 10, wherein the oxidation-reduction
potential in the solution of an absorber recirculation tank is less
than about 450 mV and the pH is less than about 6.5.
13. The method of claim 10, wherein the oxidation-reduction
potential in the solution of an absorber recirculation tank is less
than about 400 mV and the pH is less than about 6.
14. The method of claim 10, wherein the oxidation-reduction
potential in the solution of an absorber recirculation tank is less
than about 350 mV and the pH is less than about 6.
15. The method of claim 10, wherein the oxidation-reduction
potential in the solution of an absorber recirculation tank is less
than about 300 mV and the pH is less than about 6.
16. The method of claim 5, wherein the method permits control of
the oxidation-reduction potential in the solution of an absorber
recirculation tank so that the oxidation-reduction potential is
less than about 500 mV.
17. The method of claim 5, wherein the method permits control of
the oxidation-reduction potential in the solution of an absorber
recirculation tank so that the oxidation-reduction potential is
less than about 450 mV.
18. The method of claim 5, wherein the method permits control of
the oxidation-reduction potential in the solution of an absorber
recirculation tank so that the oxidation-reduction potential is
less than about 400 mV.
19. The method of claim 5, wherein the method permits control of
the oxidation-reduction potential in the solution of an absorber
recirculation tank so that the oxidation-reduction potential is
less than about 350 mV.
20. The method of claim 5, wherein the method permits control of
the oxidation-reduction potential in the solution of an absorber
recirculation tank so that the oxidation-reduction potential is
less than about 300 mV.
21. The method of claim 5, wherein the method permits control of at
least the selenium speciation in the absorber recirculation tank
solution while simultaneously permitting control of mercury
reemission from the wet flue gas desulfurization unit.
22. The method of claim 5, wherein the method permits control of at
least the selenium speciation in the absorber recirculation tank
solution.
23. The method of claim 5, wherein the method permits control of
one or more of the selenium speciation, the manganese speciation,
the cobalt speciation, the mercury speciation, or any two or more
thereof in the absorber recirculation tank solution.
Description
FIELD AND BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to the generation of
steam via the use of a combustion process to produce heat and, in
one embodiment, to a device, system and/or method that enables one
to control one or more process parameters of a combustion process
so as to yield at least one desirable change in at least one
downstream parameter. In one embodiment, the present invention is
directed to a system and/or method for controlling at least one
process parameter of a combustion process so as to yield at least
one desirable change in at least one downstream process parameter
associated with one or more of a wet flue gas desulfurization
(WFGD) unit, a particulate collection device and/or control of
additives thereto and/or a nitrogen oxide control device and/or
control of additives thereto and/or additives to the system. In
another embodiment, the present invention is directed to a system
and/or method for controlling at least two process parameters of a
combustion process so as to yield at least one desirable change in
at least one downstream process parameter associated with one or
more of a wet flue gas desulfurization (WFGD) unit, a particulate
collection device and/or control of additives thereto and/or a
nitrogen oxide control device and/or control of additives thereto
and/or additives to the system.
[0003] 2. Description of the Related Art
[0004] A variety of SO.sub.2 control processes and technologies are
in use and others are in various stages of development.
Commercialized processes include wet, semidry (slurry spray with
drying) and completely dry processes. The wet flue gas
desulfurization (WFGD) scrubber is the dominant worldwide
technology for the control of SO.sub.2 from utility power plants,
with approximately 85 percent of the installed capacity, although
the dry flue gas desulfurization (DFGD) systems are also used for
selected lower sulfur applications.
[0005] Wet scrubbing processes are often categorized by reagent and
other process parameters. The primary reagent used in wet scrubbers
is limestone. However, any alkaline reagent can be used, especially
where site-specific economics provide an advantage. Other common
reagents are lime (CaO), magnesium enhanced lime (MgO and CaO),
ammonia (NH.sub.3), and sodium carbonate (Na.sub.2CO.sub.3).
[0006] A number of the wet processes are also classified as either
non-regenerable or regenerable systems. In non-regenerable systems,
the reagent in the scrubber is consumed to directly generate a
byproduct containing the sulfur, such as gypsum. In regenerable
systems, the spent reagent is regenerated in a separate step to
renew the reagent material for further use and to produce a
separate byproduct, such as elemental sulfur. The dominant
limestone and lime reagent systems used today are non-regenerable.
In many cases the regenerable systems have been retrofitted with
non-regenerable limestone or lime reagent systems to reduce costs
and improve unit availability.
[0007] As known to those of skill in the art, the most common WFGD
absorber module is the spray tower design (see, e.g., Steam/its
generation and use, 41st Edition, Kitto and Stultz, Eds., Copyright
2005, The Babcock & Wilcox Company, Barberton, Ohio, U.S.A.,
particularly Chapter 35--Sulfur Dioxide Control, the text of which
is hereby incorporated by reference as though fully set forth
herein). In the most common WFGD set-up the flue gas enters the
side of the spray tower at approximately its midpoint and exits
through a transition at the top. The upper portion of the module
(absorption zone) provides for the scrubbing of the flue gas to
remove the SO.sub.2 while the lower portion of the module serves as
an integral slurry reaction tank (also frequently referred to as
the recirculation tank (or absorber recirculation tank) and
oxidation zone) to complete the chemical reactions to produce
gypsum. The self-supporting absorber towers typically range in
diameter from 20 feet to 80 feet (6 meters to 24 meters) and can
reach 150 feet (46 meters) in height. In some designs, the lower
reaction tank is flared downward to provide a larger diameter tank
for larger slurry inventory and longer retention time. Other key
components include the slurry recirculation pumps, interspatial
spray headers and nozzles for slurry injection, moisture separators
to minimize moisture carryover, oxidizing air injection system,
slurry reaction tank agitators to prevent settling, and the
perforated tray to enhance SO.sub.2 removal performance.
[0008] It has been found that higher concentrations (generally
above about 700 ppm) of one or more oxidizers including, but not
limited to persulfate, permanganate, manganate, ozone,
hypochlorite, chlorate, nitric acid, iodine, bromine, chlorine,
fluorine, or combinations of any two or more thereof, coupled with
thermodynamically favorable pH and oxidation-reduction potential
(ORP) (generally above 500 mV) conditions in the wet scrubber, will
cause soluble manganese (Mn.sup.2+) to form Mn.sub.xO.sub.y
precipitate, as well as impact upon the nature, the amount and/or
the conditions of mercury reemission and selenium emission from the
WFGD. Additionally, the ORP in a WFGD can impact emission rate
and/or phase partitioning and/or nature of one or more other
compounds, or species. Additionally, the ORP in a WFGD absorber
tank can influence the oxidation state of any selenium that is
present in the absorber tank thereby impacting the ability of to
control the emission of one or more selenium species. Generally
speaking, an ORP of greater than about 300 mV in an ART tends to
favor the formation of selenium (VI) species and/or compounds
(e.g., selenate ions and/or compounds, etc.).
[0009] Additionally, the control of various Air Quality Control
Systems (AQCS) are in need of optimization. As more and more power
generation utilities are beginning to vary megawatt (MW) output,
the boilers, SCRs, SNCRs, bag houses, ESPs and WFGD are being
"asked" to fluctuate performance to respond to these changes in
load. Thus, there is a need for various optimization programs that
will permit for a more efficient use of ammonia, power input in the
ESPs, limestone and/or lime injection into the WFGD or DFGDs and a
potential for a higher quality gypsum byproduct.
[0010] Given the above, a need exists in the art for a system
and/or method by which to control one or more process parameters of
a combustion process so as to yield a favorable change in and/or
permit the control of the ORP of a WFGD absorber tank thereby
resulting in the ability to control one or more the downstream
parameters so as to positively impact the ORP in the absorber tank
of a WFGD unit, improve the operation of a WFGD unit, or improve,
mitigate and/or control the emission of one or more species or
compounds that occur from or downstream of a WFGD unit.
Additionally a need exists to control the parameters of the various
AQCS equipment to allow for one or more holistic optimization
programs for one or more portions, of the totality, of an AQCS.
SUMMARY OF THE INVENTION
[0011] The present invention relates generally to the generation of
steam via the use of a combustion process to produce heat and, in
one embodiment, to a device, system and/or method that enables one
to control one or more process parameters of a combustion process
so as to yield at least one desirable change in at least one
downstream parameter. In one embodiment, the present invention is
directed to a system and/or method for controlling at least one
process parameter of a combustion process so as to yield at least
one desirable change in at least one downstream process parameter
associated with one or more of a wet flue gas desulfurization
(WFGD) unit, a particulate collection device and/or control of
additives thereto and/or a nitrogen oxide control device and/or
control of additives thereto and/or additives to the system. In
another embodiment, the present invention is directed to a system
and/or method for controlling at least two process parameters of a
combustion process so as to yield at least one desirable change in
at least one downstream process parameter associated with one or
more of a wet flue gas desulfurization (WFGD) unit, a particulate
collection device and/or control of additives thereto and/or a
nitrogen oxide control device and/or control of additives thereto
and/or additives to the system.
[0012] Accordingly, one aspect of the present invention is drawn to
a method for optimizing a wet flue gas desulfurization unit, the
method comprising the steps of: (I) measuring, analyzing and/or
controlling at least one parameter selected from: (a) the type
and/or amount of fuel to be combusted in the combustion process;
(b) the oxidation air flow rate to the combustion process; (c) the
ammonia slip across the selective catalytic reduction unit; (d) the
nitrogen oxide output from a selective catalytic reduction unit;
(e) the particulate control and/or capture device; (f) the mercury
speciation in the flue gas and/or absorber tank; (g) the selenium
speciation in the flue gas and/or absorber tank; (h) the chemistry
in the flue gas and/or absorber tank of the WFGD; (i) the oxidation
reduction potential of the absorber tank of the WFGD; (j) the
amount of the suspended solids in the absorber tank of the wet flue
gas desulfurization unit; (k) the analysis of the limestone and/or
lime utilized in the wet flue gas desulfurization unit; (I) the
amount of various reagents supplied to the wet flue gas
desulfurization unit tower; (m) the SO.sub.2 concentration at the
flue gas inlet of the wet flue gas desulfurization unit; (n) the
inlet opacity of the wet flue gas desulfurization unit; (o) the PI
data from the wet flue gas desulfurization unit; (p) the amount of
dissolved solids in the wet flue gas desulfurization unit; and/or
(q) the relative saturation of the gypsum crystals in the wet flue
gas desulfurization unit; (II) generating data from the at least
one parameter of Step (I); (III) using the data generated in Step
(II) to adjust at least one operational parameter selected from:
(A) the operational wet flue gas desulfurization unit tower level;
(B) the reagent feed flow to the wet flue gas desulfurization unit;
(C) the oxidation air flow to the wet flue gas desulfurization
unit; (D) the rate of absorber bleed from the wet flue gas
desulfurization unit; (E) the liquid to gas ratio in the wet flue
gas desulfurization unit tower; (F) the number of operating
absorber recycle pumps in the wet flue gas desulfurization unit;
(G) the dewatering operation parameters; (H) the ammonia feed rate
to the selective catalytic reduction unit; (I) the gypsum purity;
(J) the gypsum-related scale formation in the wet flue gas
desulfurization unit absorber tower; (K) the parasitic power loss
by the wet flue gas desulfurization unit equipment; (L) the
oxidation-reduction potential in the absorber recirculation tank;
(M) the wet flue gas desulfurization unit effluent stream waste
water treatment parameters; (N) the SO.sub.2 removal efficiency by
the wet flue gas desulfurization unit; (O) the relative saturation
of the gypsum crystals in the slurry; and/or (P) the total
dissolved solids in the wet flue gas desulfurization unit.
[0013] In yet another aspect of the present invention, there is
provided a method for optimizing a wet flue gas desulfurization
unit, the method comprising the steps of: (i) measuring, analyzing
and/or controlling at least one parameter in real time selected
from: (a) the type and/or amount of fuel to be combusted in the
combustion process; (b) the oxidation air flow rate to the
combustion process; (c) the ammonia slip across the selective
catalytic reduction unit; (d) the nitrogen oxide output from a
selective catalytic reduction unit; (e) the particulate control
and/or capture device; (f) the mercury speciation in the flue gas
and/or absorber tank; (g) the selenium speciation in the flue gas
and/or absorber tank; (h) the chemistry in the flue gas and/or
absorber tank of the WFGD; (i) the oxidation reduction potential of
the absorber tank of the WFGD; (j) the amount of the suspended
solids in the absorber tank of the wet flue gas desulfurization
unit; (k) the analysis of the limestone and/or lime utilized in the
wet flue gas desulfurization unit; (I) the amount of various
reagents supplied to the wet flue gas desulfurization unit tower;
(m) the SO.sub.2 concentration at the flue gas inlet of the wet
flue gas desulfurization unit; (n) the inlet opacity of the wet
flue gas desulfurization unit; (o) the PI data from the wet flue
gas desulfurization unit; (p) the amount of dissolved solids in the
wet flue gas desulfurization unit; and/or (q) the relative
saturation of the gypsum crystals in the wet flue gas
desulfurization unit; (ii) generating real-time data from the at
least one parameter of Step (I); (iii) using the real-time data
generated in Step (ii) to adjust at least one operational parameter
selected from: (A) the operational wet flue gas desulfurization
unit tower level; (B) the reagent feed flow to the wet flue gas
desulfurization unit; (C) the oxidation air flow to the wet flue
gas desulfurization unit; (D) the rate of absorber bleed from the
wet flue gas desulfurization unit; (E) the liquid to gas ratio in
the wet flue gas desulfurization unit tower; (F) the number of
operating absorber recycle pumps in the wet flue gas
desulfurization unit; (G) the dewatering operation parameters; (H)
the ammonia feed rate to the selective catalytic reduction unit;
(I) the gypsum purity; (J) the gypsum-related scale formation in
the wet flue gas desulfurization unit absorber tower; (K) the
parasitic power loss by the wet flue gas desulfurization unit
equipment; (L) the oxidation-reduction potential in the absorber
recirculation tank; (M) the wet flue gas desulfurization unit
effluent stream waste water treatment parameters; (N) the SO.sub.2
removal efficiency by the wet flue gas desulfurization unit; (O)
the relative saturation of the gypsum crystals in the slurry;
and/or (P) the total dissolved solids in the wet flue gas
desulfurization unit.
[0014] In yet another aspect of the present invention, there is
provided a method for optimizing a wet flue gas desulfurization
unit, the method comprising the steps of: controlling, measuring
and/or analyzing at least one process parameter of a combustion
process and/or at least one combustion process air quality control
system in order to yield at least one data set; using the at least
one data set to effect a desirable change in at least one
downstream process parameter associated with one or more of a wet
flue gas desulfurization unit, a particulate collection device
and/or a nitrogen oxide control device.
[0015] In yet another aspect of the present invention, there is
provided a method for optimizing a wet flue gas desulfurization
unit, the method comprising the steps of: controlling, measuring
and/or analyzing at least two process parameters of a combustion
process and/or at least one combustion process air quality control
system in order to yield at least one data set; using the at least
two data sets to effect a desirable change in at least one
downstream process parameter associated with one or more of a wet
flue gas desulfurization unit, a particulate collection device
and/or a nitrogen oxide control device.
[0016] In yet another aspect of the present invention, there is
provided a method for optimizing a wet flue gas desulfurization
unit, the method comprising the steps of: measuring, analyzing
and/or controlling at least one parameter selected from: (i)
desulfurization tower load; (ii) oxidation air flow rate; (iii) one
or more boiler parameters; (iv) one or more selective catalytic
reduction unit parameters; and/or (v) one or more electrostatic
precipitator parameters; generating data from the at least one
parameter of the previous Step; and using the data generated in the
previous Step to adjust at least one operational parameter selected
from: (a) one or more gypsum production properties and/or
parameters; (b) the oxidation-reduction potential in the absorber
recirculation tank; (c) the pH of the absorber recirculation tank
solution; (d) the concentration, type and/or speciation of one or
more compounds and/or ions in the absorber recirculation tank
solution; and/or (e) the concentration, type and/or speciation of
one or more oxidizer compounds and/or ions in the absorber
recirculation tank solution and/or the wet flue gas desulfurization
unit.
[0017] The various features of novelty which characterize the
invention are pointed out with particularity in the claims annexed
to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and
specific benefits attained by its uses, reference is made to the
accompanying drawings and descriptive matter in which exemplary
embodiments of the invention are illustrated.
DESCRIPTION OF THE INVENTION
[0018] The present invention relates generally to the generation of
steam via the use of a combustion process to produce heat and, in
one embodiment, to a device, system and/or method that enables one
to control one or more process parameters of a combustion process
so as to yield at least one desirable change in at least one
downstream parameter. In one embodiment, the present invention is
directed to a system and/or method for controlling at least one
process parameter of a combustion process so as to yield at least
one desirable change in at least one downstream process parameter
associated with one or more of a wet flue gas desulfurization
(WFGD) unit, a particulate collection device and/or control of
additives thereto and/or a nitrogen oxide control device and/or
control of additives thereto and/or additives to the system. In
another embodiment, the present invention is directed to a system
and/or method for controlling at least two process parameters of a
combustion process so as to yield at least one desirable change in
at least one downstream process parameter associated with one or
more of a wet flue gas desulfurization (WFGD) unit, a particulate
collection device and/or control of additives thereto and/or a
nitrogen oxide control device and/or control of additives thereto
and/or additives to the system.
[0019] In one embodiment, the present invention the system and/or
method of the present invention includes controlling and/or
monitoring one or more of: (i) desulfurization tower load; (ii)
oxidation air flow rate; (iii) one or more boiler parameters; (iv)
one or more selective catalytic reduction (SCR) unit parameters;
and (v) one or more parameters of the particulate collection device
(e.g., the electrostatic precipitator (ESP)).
[0020] Given the above, a more detailed discussion of each of the
above parameters will be discussed herein below. Turning to
parameter (i), in one embodiment the system and/or method of the
present invention involves analyzing, controlling and/or monitoring
the tower load of a desulfurization unit (e.g., a wet flue gas
desulfurization unit (WFGD)) via analyzing, controlling and/or
monitoring one or more of the megawatt load being generated by the
boiler unit; the SO.sub.2 removal rate; and/or the inlet SO.sub.2
amount present at least one inlet to the desulfurization unit.
[0021] Turning to parameter (ii), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the amount, flow rate and/or type of
the oxidation air that is supplied to a desulfurization unit (e.g.,
a wet flue gas desulfurization unit (WFGD)). While not wishing to
be bound to any one theory, it is believed that by analyzing,
controlling and/or monitoring the amount, flow rate and/or type of
the oxidation air that is supplied to a desulfurization unit it is
possible to control the production of sulfite compounds and/or
species in the flue gas as well as in the desulfurization unit.
This in turn is believed to impact the formation of other strong
oxidizers as sulfite ions are known to act as reducing agents in a
flue gas and/or desulfurization unit environment. Furthermore, the
production of sulfite ions and/or species can have an impact on the
production and/or presence of any ozone that may occur due to the
operation of any one or more particulate collection devices (e.g.,
an electrostatic precipitator). Additionally, via the control of
the amount and/or concentration of various types of sulfite species
and/or ions, it is possible to control the calcium sulfite to
calcium sulfate conversion rate which in turn permits one to
control the gypsum production rate and/or purity of the WFGD.
[0022] Turning to parameter (iii), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring various boiler parameters. Such
parameters include, but are not limited to, fuel supply rate,
oxidation air supply rate, overfire air supply rate, type of fuel,
fuel composition, fuel type, fuel impurities, etc. Given the
analysis, control and/or monitoring of one or more of the above
noted boiler parameters, various resulting downstream parameters or
downstream process parameters can be controlled. While not wishing
to be bound to any one theory and/or downstream process parameters
that can be controlled, it is then possible via the control of one
or more of the above noted boiler parameters to impact the ORP in,
for example, a recirculation tank of a wet scrubber (also referred
to as an absorber recirculation tank or ART). This in turn permits
the control and/or mitigation of various corrosion issues that
occur when the ORP in an ART becomes undesirable. Additionally, the
analysis, control and/or monitoring of one or more boiler
parameters can permit the control of ash resistivity.
[0023] As used herein, "ash resistivity" refers to the resistivity
of the ash to accept a charge. The ash resistivity affects the
ability of the particulate collection device, and in particular, an
electrostatic precipitator, to efficiently complete its assigned
task (that is the collection of particulate material from a flue
gas). Additionally, the boiler parameters also have an impact on
the operating conditions of any SCR that might be utilized to
remove nitrous oxides from the flue gas. Given the above, the
boiler parameters can indirectly impact the amount of ozone that
may be produced by an ESP as the boiler parameters impact the
amount and/or type of ash that is produced by the combustion
process. The ash type and/or amount in turn influences the
operating conditions that are necessary in the ESP to collect said
ash. For example, if an ESP has to operate at a high power and/or
higher sparking rate in order to adequately collect the ash in the
flue gas, such conditions can lead to an increase in the production
of ozone in the flue gas.
[0024] While not wishing to be bound to any one theory, it is
believed that an increase in the concentration (or amount) of ozone
in the flue gas leads to an undesirable change in the ORP in an ART
(this is of course in the case where the flue gas desulfurization
unit is a WFGD). This is because ozone is a strong oxidizer. Thus,
the boiler parameters indirectly impact the amount of ozone
generated via the impact such parameters have on ash resistivity.
This is true in most cases but may not generate and/or yield the
same results and/or impact on ozone production and/or ESP
parameters if one or more additives added to the coal prior to the
coal being supplied to the burners and/or any additives are added
to the boiler and/or flue gas stream upstream (i.e., the hot side)
of the SCR.
[0025] Turning to parameter (iv), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring various SCR parameters. Such
parameters include, but are not limited to, the ammonia slip across
the selective catalytic reduction (SCR) unit and/or the nitrogen
oxide output from a SCR. It is believed that such parameters can
impact the ORP in the ART. In one embodiment, the control of
various boiler parameters are more important in the control of the
ORP in the ART than it is to control various SCR parameters. In
another embodiment, it is more important to control the SCR
parameters instead of the boiler parameters in order to achieve the
desired ORP control. In yet another embodiment, the desired control
of the ORP in the ART is achieved by controlling any various
combination of at least one boiler parameter in combination with at
least one SCR parameter.
[0026] Turning to parameter (v), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring various ESP parameters. As would be
apparent to those of skill in the art, this factor applies only if
there is an ESP present in the air quality control systems attached
to the combustion process in question. In one embodiment, the ESP
parameters that are analyzed, controlled and/or monitored include,
but are not limited to, ESP power and/or ESP sparking rate.
[0027] As noted above, ESP power and/or ESP sparking rate is a
function of ash resistivity. This is because it is necessary to
increase either one or both of ESP power and/or ESP sparking rate
to achieve a desired level of ash removal if the ash has a high
resistivity to the acceptance of a charge. The higher the ESP power
and/or ESP sparking rate, the higher the ozone production rate
and/or concentration. This in turn leads to a higher ORP in the ART
do to either the direct impact of an increase in the concentration
of ozone or some chemical and/or species generated by ozone
reacting with another species or compound present in the flue gas.
The injection of SO.sub.3, trona (i.e., trisodium
hydrogendicarbonate which can also be written in its hydrated form
as Na.sub.3(CO.sub.3)(HCO.sub.3).2H.sub.2O) and/or hydrated lime
seems to impact the formation of ozone in the ESP. It should be
noted that the term "trona" is to be broadly construed and is not
solely limited to just the hydrated state detailed above.
[0028] While not wishing to be bound to any one theory, it is
believed that the injection of one or more of the above compounds
effects ash resistivity and thus impacts either positively or
negatively the amount of ozone generated by the power and sparking
in the ESP. As such, in one embodiment the present invention
encompasses the analysis, control and/or monitoring of the type of
materials injected into the flue gas stream to determine the impact
of such compounds on ash resistivity. As noted above, an increase
in ash resistivity can lead to an increase in ozone production
because it becomes necessary to increase either one or both of ESP
power and/or ESP sparking rate in order to achieve the desired
level of ash removal as the ash becomes more resistive to accepting
a charge. This in turn can, as noted above, result an undesired
change in the ORP of an ART due to the presence of an increased
amount of ozone and/or an increase in various reaction products
formed due to the interaction of various flue gas constituents with
the increased level of ozone.
[0029] Given the above, the one or more analyses, control measures,
measurements and/or determinations of the various parameters listed
above can permit the control and/or optimization of one or more of
the following: (a) one or more gypsum production properties and/or
parameters including, but no limited to, gypsum purity, gypsum
moisture content and/or gypsum mass flow; (b) the
oxidation-reduction potential (ORP) in the absorber recirculation
tank (ART); and (c) the pH of the ART solution. The ORP in the Art
can be measured, monitored and/or determined by the ORP in mV or a
sensor designed to measure and/or monitor the oxidizer content in
the ART solution. The ORP in turn can influence various parameters
including, but not limited to, the aqueous species in the ART
solution such as selenium, cobalt, manganese, mercury, arsenic, as
well as potentially any other trace elements that might be in coal
that might be regulated now or in the near future. Regarding the pH
of the ART solution, the pH of this solution can be measured by
various known methods including, but not limited to, titration, pH
meters, etc.
[0030] In another embodiment, the system and/or method of the
present invention includes controlling and/or monitoring one or
more of: (I) the type and/or amount of fuel to be combusted in the
combustion process (e.g., fossil fuel type such as coal type); (II)
the oxidation air flow rate to the combustion process; (III) the
ammonia slip across the selective catalytic reduction (SCR) unit,
if present; (IV) the nitrogen oxide output from a SCR, if present;
(V) the particulate control and/or capture device (e.g.,
electrostatic precipitator (ESP)) including, but not limited to,
one or more particulate collection device operating parameters; the
additives to the ESP system including, but not limited to, ash
condition agents including but not limited to sulfur species;
system additives injected for SO.sub.3 mitigation; (VI) the mercury
speciation in the flue gas and/or absorber tank; (VII) the selenium
speciation in the flue gas and/or absorber tank; (VIII) the
chemistry in the flue gas and/or absorber tank of the WFGD; (IX)
the oxidation reduction potential (ORP) of the absorber tank of the
WFGD; the pH within the absorber tank; (X) the amount of the
suspended solids (SS) in the absorber tank of the WFGD; (XI) the
analysis of the limestone and/or lime utilized in the WFGD; (XII)
the amount of various reagents supplied to the WFGD tower; (XIII)
the SO.sub.2 concentration at the flue gas inlet of the WFGD; (XIV)
the inlet opacity of the WFGD; and/or (XV) the PI data from the
WFGD.
[0031] Given the above, a more detailed discussion of each of the
above parameters will be discussed herein below. Turning to
parameter (I), in one embodiment the system and/or method of the
present invention involves analyzing, controlling and/or monitoring
the type and/or amount of fuel to be combusted in the combustion
process (e.g., fossil fuel type such as coal type). In the case
where an analysis of this parameter is utilized the analysis of the
fuel to be combusted can be accomplished by any one or more known
analysis techniques including, but not limited to, gas
chromatography, liquid chromatography, gas chromatography-mass
spectroscopy (GC-MS), mass spectroscopy, NMR analysis, FTIR, flame
analysis, etc. In another embodiment, the analysis of the fuel to
be combusted can be accomplished by utilizing any two or more of
the above-mentioned techniques. When utilized, the analysis of the
fuel to be combusted can involve analyzing the heating value, the
amount of phosphorus, hydrogen, chlorine, fluorine, sulfur, one or
more heavy metals (e.g., mercury, cadmium, selenium, etc.),
moisture content, ash content, carbon content, mineral content
(e.g., pyrite).
[0032] Alternatively, the amount of sulfur and/or phosphorus in a
combustion gas can be ascertained utilizing one or more sensors or
probes designed to measure the amount of gas-phase sulfur and/or
gas-phase phosphorus. Since such probes are known to those of skill
in the art, a detailed discussion herein is omitted for the sake of
brevity. As would be apparent to those of skill in the art, any
probes and/or sensors utilized in connection with the various
systems and/or methods of the present invention can be placed at
one or more locations in a steam generation combustion process
including, but not limited to, the boiler, the combustion zone of
the boiler, the economizer, the air heater (if present), the SCR or
SNCR (if present), the particulate control device (e.g., a ESP or
bag house), and/or the WFGD. It should be noted that the above
positions are exemplary in nature and the present invention is not
limited to solely the above-listed locations. Rather, any location
within a steam generation system can be utilized where any one more
sensors, or probes, located therein yield at least one piece of
useful data. Additionally, any of the analyses discussed herein
can, if so possible, be accomplished in real-time if a suitable
sensor, or probe, is available to measure and/or analyze the
desired given parameter, or parameters.
[0033] Turning to parameter (II), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the oxidation air flow rate to the
combustion process. In this embodiment, such an analysis can be
accomplished by the use of a flow meter or other system that
permits one to ascertain the amount of oxidation air that is being
supplied to a combustion process. Alternatively, a metering system
can be utilized so as to permit one to determine the amount of
oxidation air that is being supplied to a combustion process. In
another embodiment, various other system and/or methods are known
to those that permit the metering and/or measurement of a gas being
supplied to a process and can be utilized herein to determine the
amount of oxidation air being supplied to a combustion process. It
should be noted that some combustion process might not utilize a
discrete oxidation air supply. In this instance, the analyses of
the amount of oxidation air being supplied to a combustion process
would be omitted.
[0034] Turning to parameter (III), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the ammonia slip across the selective
catalytic reduction (SCR) unit, if so present. As would be known to
those of skill in the emissions control arts, systems and/or
methods for determining the amount ammonia slip across an SCR are
known in the art and any such system and/or method can be utilized
in conjunction with the present invention to obtain data relating
to the amount of ammonia slip across the SCR. Since such systems
and/or methods are known in the art, a detailed discussion herein
is omitted for the sake of brevity.
[0035] Turning to parameter (IV), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the nitrogen oxide output from a SCR,
if present. As would be known to those of skill in the emissions
control arts, systems and/or methods for determining the amount
nitrogen in a gas are known in the art and any such system and/or
method can be utilized in conjunction with the present invention to
obtain data relating to the amount and/or concentration of nitrogen
and/or nitrogen-containing compounds in a gas. Since such systems
and/or methods are known in the art, a detailed discussion herein
is omitted for the sake of brevity.
[0036] Turning to parameter (V), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the operating parameters of one or
more particulate control and/or capture devices (e.g.,
electrostatic precipitator (ESP)). Such operating parameters can
include, but are not limited to, power input, spark rate. Such
operating parameters also include additives to or upstream of the
ESP, including but not limited to fly ash conditioning agents,
including but not limited to injection of sulfur species
[0037] Turning to parameter (VI), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the mercury speciation in the flue
gas and/or absorber tank. As would be known to those of skill in
the emissions control arts, systems and/or methods for determining
the type of mercury species in a flue gas are known in the art and
any such system and/or method can be utilized in conjunction with
the present invention to obtain data relating to the type, amount
and/or concentration of various mercury species in a gas. Suitable
methods can include, but are not limited to, titration, liquid
chromatography, gas chromatography-mass spectroscopy (GC-MS), mass
spectroscopy, NMR analysis, FTIR, and/or flame analysis. Since such
systems and/or methods are known in the art, a detailed discussion
herein is omitted for the sake of brevity.
[0038] Turning to parameter (VII), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the selenium speciation in the flue
gas and/or absorber tank. As would be known to those of skill in
the emissions control arts, systems and/or methods for determining
the type of selenium species in a flue gas are known in the art and
any such system and/or method can be utilized in conjunction with
the present invention to obtain data relating to the type, amount
and/or concentration of various selenium species in a gas. Suitable
methods can include, but are not limited to, titration, liquid
chromatography, gas chromatography-mass spectroscopy (GC-MS), mass
spectroscopy, NMR analysis, FTIR, and/or flame analysis. Since such
systems and/or methods to accomplish same are known in the art, a
detailed discussion herein is omitted for the sake of brevity.
[0039] Turning to parameter (VIII), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the chemistry in the flue gas and/or
absorber tank of the WFGD. As would be known to those of skill in
the emissions control arts, systems and/or methods for determining
various chemical and/or physical parameters in the solution of an
absorber tank of a WFGD are known to those of skill in the art.
Exemplary chemical and/or physical parameters that can be analyzed
include, but are not limited to, the pH of the absorber tank
solution, the specific gravity of the absorber tank solution, the
viscosity of the absorber tank solution, the opacity of the
absorber tank solution, the total suspended solids in the absorber
tank solution, the recirculation rate of the solution in the
absorber tank, and/or the present of one or more aqueous species in
the absorber tank (e.g., persulfate species concentration and/or
type, one or more oxidizer species and/or concentration, chloride
concentration, fluoride concentration, calcium concentration,
sulfur-oxygen compounds, sulfur-nitrogen compounds, magnesium
species concentration and/or type, mercury concentration, selenium
concentration and type). Here, as well as elsewhere in the
specification and claims, the term "oxidizer" includes, but not
limited to, persulfate, permanganate, manganate, ozone,
hypochlorite, chlorate, nitric acid, iodine, bromine, chlorine,
fluorine, or combinations of any two or more thereof. Here, as well
as elsewhere in the specification and claims, the term "persulfate"
is defined to include one or both of peroxodisulfate ions
(S.sub.2O.sub.8.sup.2-) or peroxomonosulfate ions
(SP.sub.5.sup.2-). Accordingly, as used throughout the
specification and claims the term "persulfate" includes both
persulfate ions and other forms of the noted ionic compounds above
regardless of whether such ions are bound in a chemical composition
or in an ionic state because they are in solution.
[0040] Regarding the above one or more parameters to be measured
and/or analyzed, suitable methods can include, but are not limited
to, titration, liquid chromatography, gas chromatography-mass
spectroscopy (GC-MS), mass spectroscopy, NMR analysis, FTIR, and/or
flame analysis. Since such systems and/or methods to accomplish
same are known in the art, a detailed discussion herein is omitted
for the sake of brevity.
[0041] Turning to parameter (IX), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the oxidation reduction potential
(ORP) of the absorber tank of the WFGD. Such a determination of the
ORP of the absorber tank solution can be accomplished by a variety
of methods including, but not limited to, determining the
concentration of various aqueous species (e.g., one or more
oxidizer species concentration and/or type, persulfate species
concentration and/or type, magnesium species concentration and/or
type, chloride concentration, fluoride concentration, calcium
concentration, sulfur-oxygen compounds, sulfur-nitrogen compounds,
magnesium species concentration and/or type, mercury concentration,
selenium concentration and type). Regarding the above one or more
aqueous species to be measured and/or analyzed, suitable methods
can include, but are not limited to, titration, liquid
chromatography, gas chromatography-mass spectroscopy (GC-MS), mass
spectroscopy, NMR analysis, FTIR, electrical measurement of the
conductiveness of the absorber tank solution, oxidation reduction
potential measurements, and/or flame analysis. Since such systems
and/or methods to accomplish same are known in the art, a detailed
discussion herein is omitted for the sake of brevity.
[0042] Turning to parameter (X), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the suspended solids (SS), or even
total suspended solids (TSS), in the absorber tank of the WFGD.
Such measurements can be accomplished by a variety of known
techniques and/or systems including, but not limited to, turbidity
and/or opacity measurements, titration, etc.
[0043] Turning to parameter (XI), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the limestone and/or lime utilized in
the WFGD. Such an analysis can include, but is not limited to, a
compositional analysis, the amount of limestone and/or lime being
supplied to the WFGD via one or more techniques including, but not
limited to, titration, liquid chromatography, gas
chromatography-mass spectroscopy (GC-MS), mass spectroscopy, NMR
analysis, FTIR, electrical measurement of the conductiveness of the
absorber tank solution, oxidation reduction potential measurements,
and/or flame analysis. Since such systems and/or methods to
accomplish same are known in the art, a detailed discussion herein
is omitted for the sake of brevity.
[0044] Turning to parameter (XII), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the amount of various reagents
supplied to the WFGD tower. Such reagents include, but are not
limited to, water, pH buffer, reducing agents, oxidizing agents,
organic acids). Such an analysis can include, but is not limited
to, a compositional analysis, purity analysis, etc. supplied to a
WFGD via one or more techniques including, but not limited to,
titration, liquid chromatography, gas chromatography-mass
spectroscopy (GC-MS), mass spectroscopy, NMR analysis, FTIR,
electrical measurement of the conductiveness of the absorber tank
solution, oxidation reduction potential measurements, and/or flame
analysis. Since such systems and/or methods to accomplish same are
known in the art, a detailed discussion herein is omitted for the
sake of brevity.
[0045] Turning to parameter (XIII), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the SO.sub.2 concentration at the
flue gas inlet of the WFGD. As would be known to those of skill in
the emissions control arts, systems and/or methods for determining
the amount SO.sub.2 in a gas are known in the art and any such
system and/or method can be utilized in conjunction with the
present invention to obtain data relating to the amount and/or
concentration of SO.sub.2 in a gas. Since such systems and/or
methods are known in the art, a detailed discussion herein is
omitted for the sake of brevity.
[0046] Turning to parameter (XIV), in one embodiment the system
and/or method of the present invention involves analyzing,
controlling and/or monitoring the inlet opacity of the WFGD. Such
an analysis can be accomplished by a variety of methods including,
but not limited to, titration testing, turbidity measurements
and/or opacity measurements. Turning to parameter (XV), in one
embodiment the system and/or method of the present invention
involves analyzing the PI data from the WFGD.
[0047] Additionally, as noted above, any of the analyses discussed
herein can, if so possible, be accomplished in real-time if a
suitable sensor, or probe, is available to measure and/or analyze
the desired given parameter, or parameters. In the case where real
time data is desired at least one computer and/or computational
system can be utilized in conjunction with the present invention.
Such computer systems and/or computational devices are known to
those of skill in the art and as such a discussion herein is
omitted for the sake of brevity.
[0048] Given the above, the one or more analyses, control measures,
measurements and/or determinations of the various parameters listed
above can permit the control and/or optimization of one or more of
the following: (A) operational WFGD tower level; (B) reagent feed
flow to the WFGD; (C) oxidation air flow to the WFGD; (D) rate of
absorber bleed from the WFGD; (E) liquid to gas ratio in the WFGD
tower; (F) the number of operating absorber recycle pumps in the
WFGD; (G) dewatering (hydroclone) operation parameters; (H) ammonia
feed rate to the SCR (if present); (I) the number of ESP feeds in
operation in a WFGD; (J) gypsum purity; (K) gypsum-related scale
formation in the WFGD absorber tower; (L) parasitic power loss by
the WFGD equipment; (M) WFGD effluent stream waste water treatment
parameters; and (N)SO.sub.2 removal efficiency by the WFGD.
[0049] This system and/or method of the present invention can, in
one embodiment, achieve for a more responsive control system which
will allow the WFGD system to function better during times of
non-steady state operation by the boiler. More and more, coal fired
utilities are swinging boiler load to allow for steady power grid
operation. A more responsive control system may lead to better
tower chemistry thereby achieving an improvement in SO.sub.2
removal efficiency.
[0050] As an example of one such non-limiting parameter and/or
operating condition that can be measured and therefore controlled
is the ORP level of the solution in an absorber tank of a WFGD.
Controlling ORP to a pre-determined range and steady state
condition can help mitigate corrosion potential in the tower as
well as to control elemental vapor phase mercury formation and
reemission. An optimization program that will help to control the
SCR and ESP parameters may lead to less ammonia injection and less
power requirement by the ESP. An optimization program has the
potential to mitigate parasitic power loss of the equipment.
[0051] In one embodiment, the system and/or method of the present
invention involves flue gas testing that is accomplished by
continuous Fourier Transform Infrared Spectroscopy (FTIR)
monitoring for all gas species and carbon trap mercury monitoring
across the SCR and GEMS mercury testing at the SCR inlet during
baseline testing and SCR testing weeks. Stack mercury analysis will
be performed using sorbent traps in the stack during baseline
testing. Chemical analysis of the absorber slurry will consist of
speciated mercury, selenium and ICP-MS. Corrosion testing will also
be conducted in isolated buckets wherein metal samples and
Electrical Resistance (ER) probes would contact the process slurry.
This testing will afford the opportunity for B&W to optimize
the performance of these units.
[0052] As noted above, in one embodiment the present invention
relates generally to the field of emissions control and, in
particular to a new and useful method and/or system by which to
control various types of corrosion and/or precipitation issues in
at least a portion of a wet flue gas desulfurization (WFGD)
scrubber system. In one embodiment, the method and/or system of the
present invention relies on the supply of at least one reducing
agent to the slurry of a wet flue gas desulfurization scrubber to
lower the oxidation reduction potential in the absorber slurry
contained within the wet flue gas desulfurization scrubber. In
still another embodiment, the method and/or system of the present
invention control the oxidation-reduction potential in at least one
bleed stream of an absorber slurry, filtrate, and/or solution from
a wet flue gas desulfurization scrubber.
[0053] As discussed above, it has been determined that a high
oxidation-reduction potential (ORP) and concentration of one or
more oxidizer compounds and/or species (e.g., persulfate,
permanganate, manganate, ozone, hypochlorite, chlorate, nitric
acid, iodine, bromine, chlorine, fluorine, or combinations of any
two or more thereof) in a wet scrubber's absorber recirculation
tank (ART) causes precipitation of soluble manganese. While not
wishing to be bound to any one theory, it is believed manganese
dioxide precipitate (MnO.sub.2) settling on the walls of the ART
can create a galvanic cell leading to corrosion, or further
enhancing the circumstances that cause corrosion. While not wishing
to be bound to any one solution, one possible method to control,
reduce and/or mitigate the ORP in an ART is to reduce the ORP by
controlling, eliminating and/or reducing the concentration, or
amount, of one or more oxidizer compounds and/or species (e.g.,
persulfate, permanganate, manganate, ozone, hypochlorite, chlorate,
nitric acid, iodine, bromine, chlorine, fluorine, or combinations
of any two or more thereof--in the form of ions, etc.) that exist
in, or are formed in, the ART of a WFGD. While the present
invention is described in terms of corrosion that occurs in an ART
formed from Alloy 2205 (UNS S32205, a duplex stainless steel
alloy), the present invention is not limited thereto. Rather,
corrosion can and does occur in a wide range of iron-based alloys
and as such, the present invention applies to any situation where
the ORP needs to be controlled in order to reduce, control and/or
mitigate the corrosive nature of the environment in an ART.
[0054] In still another embodiment, the present invention further
includes the use of surplus oxidation air, regardless of where such
surplus is generated, as a manner by which to control the various
chemical properties of one or more aqueous-based solutions or
liquids. This embodiment of the present invention can be achieved
by supplying a desired amount of surplus oxidation air to one or
more tanks containing any type of desired aqueous-based or liquid
solutions via a least one supply method which include, but are not
limited to, sparging, bubblers, etc.
[0055] In still yet another embodiment, the present invention
permits the control of sparking in a particulate removal device
(e.g., an electrostatic precipitator--ESP) which in turn permits
the control of various factors that influence oxidizer formation.
While not wishing to be bound to any one theory, one exemplary
manner by which the ORP in an ART increases is due to the formation
of ozone. Ozone formation can be traced to, among other things, an
increase in sparking in an ESP. To prevent, control and/or mitigate
the amount of sparking in an ESP an additive such as SO.sub.3
and/or trona can be added upstream of an ESP. Upon the addition of
SO.sub.3 and/or trona a decrease in ozone formation is observed due
to a decrease in the amount of sparking in the ESP. This in turn
allows for a more favorable ORP in the ART which in turn results in
the ability to favorably control the nature of various aqueous
species in the ART solution. Such species that can be controlled
include, but are not limited to, oxidizer species concentration and
type (e.g., persulfate species concentration and/or type),
magnesium species concentration and/or type, chloride
concentration, fluoride concentration, calcium concentration,
sulfur-oxygen compounds, sulfur-nitrogen compounds, magnesium
species concentration and/or type, mercury concentration, selenium
concentration and type, or any two or more thereof.
[0056] One non-limiting example of the present invention was
performed via field testing at the Detroit Edison (DTE) Monroe
Power Plant in November and December of 2012. This testing was
conducted to examine the effects of process changes upon wet flue
gas desulfurization (WFGD) chemistry. Accordingly to one embodiment
of the present invention, a parametric test plan to change coals,
electrostatic precipitator (ESP) operation, ammonia slip to the
SCR, WFGD oxidation air injection loading and the total suspended
solids (TSS) of the WFGD absorber recirculation tank (ART). Various
parameters where measured and the results thereof are detailed in
Tables 1 and 2 below. Of the parameters tested, modification of the
SO.sub.3 injection to the ESP had the most pronounced impact on
WFGD absorber and effluent (WFGD bleed) stream chemistry.
[0057] The ESP at DTE Monroe is designed for operation with a
mid-sulfur coal, 3.0 lbs/mBTU. DTE Monroe has switched to burning a
lower-sulfur coal blend, with different physical characteristics,
than that for which the air quality control system (AQCS) had been
designed. SO.sub.3 was injected into the ductwork upstream of the
ESPs as a fly ash conditioning agent to improve ESP removal on the
current coal. During testing at DTE Monroe, SO.sub.3 injection
prior to the ESP was shut off. One effect of the SO.sub.3 injection
in combination with the coal burned is that, for this system, one
observes a decrease in spark rate within the ESP than would be
expected without injection. Accordingly, when the SO.sub.3
injection was turned off, ESP spark rate increased. Such an
increase in spark rate likely causes an increase in ozone
production within the WFGD, thereby increasing the concentration of
downstream oxidizer(s). Other potential routes for increased
oxidizer concentration within the flue gas may also be traced back
to this increased sparking. Within a short period of time after
shutting off the SO.sub.3 injection, the ORP in the WFGD absorber
reacting tank slurry increased by approximately 300 mV, changing
the oxidation state and phase partitioning of many slurry
constituents therein.
[0058] After the SO.sub.3 injection was restarted, the ORP of the
WFGD slurry slowly returned to the lower levels that had been
exhibited during baseline testing. This return to baseline
conditions occurred slowly and with a pattern consistent with
residence time decay. None of the other parameters tested exhibited
such a pronounced and dramatic change in scrubber chemistry. This
parametric change of turning the SO.sub.3 to the ESP has since been
replicated in both operating absorber towers (Units 3 & 4) at
DTE Monroe at least twice, all times exhibiting a similar response
to the change. Accordingly, given the above, in one embodiment the
present invention seeks to utilize SO.sub.3 and/or trona injection
prior to an ESP to effect a desirable change in the ORP of an ART
of a WFGD.
TABLE-US-00001 TABLE 1 Grab S.sub.2O.sub.8 by DCS Sample DO
Conductivity lodometry ORP Dissolved Total Hg Selenite Selenate
Date/Time ORP (mV) pH (mg/L) (mS) (mg/L) pH (mV) Hg (.mu.g/L)
(.mu.g/L) (.mu.g/L) (.mu.g/L) Nov. 15, 2012 243.70 5.40 0.00 0.00
0.00 0.00 N/A 3.83 473.80 76.98 73.01 14:35 Nov. 16, 2012 246.20
5.43 5.81 53.40 107.50 0.00 N/A 5.83 501.88 9.46 9.35 12:42 Nov.
17, 2012 235.70 5.56 5.05 33.80 115.20 0.00 N/A 7.96 558.55 159.83
73.41 10:45 Nov. 18, 2012 233.70 5.51 4.93 40.10 109.44 0.00 N/A
12.20 540.34 77.33 76.33 10:18 Nov. 19, 2012 245.60 5.56 5.20 38.90
109.44 0.00 N/A 10.60 533.04 22.56 83.99 10:20 Nov. 26, 2012 273.80
5.82 4.79 28.86 124.80 0.00 N/A 5.54 665.46 251.48 82.70 10:21 Nov.
27, 2012 266.90 5.78 5.62 32.80 115.20 5.75 249.00 9.73 585.70
265.09 933.27 9:59 Nov. 28, 2012 277.00 5.71 4.89 34.20 145.92 5.75
251.00 5.93 689.05 99.00 942.78 10:08 Nov. 29, 2012 279.40 5.64
4.42 33.60 126.72 5.72 250.00 7.27 613.27 246.27 1030.57 9:28 Nov.
30, 2012 298.90 5.61 4.21 33.00 167.00 5.72 247.00 8.40 594.52
69.27 995.66 8:50 Dec. 1, 2012 303.90 5.47 4.90 29.50 136.32 5.52
248.00 16.40 579.29 605.72 864.53 9:27 Dec. 2, 2012 301.90 5.11
4.46 34.30 117.12 5.15 248.00 23.50 559.98 431.29 882.29 9:35 Dec.
3, 2012 305.00 5.57 4.44 33.40 142.08 5.58 239.00 16.90 611.64
117.06 890.55 9:50 Dec. 4, 2012 289.50 5.43 4.71 40.70 140.16 5.66
238.00 17.90 631.47 58.91 802.47 9:10 Dec. 5, 2012 298.30 5.55 4.71
32.90 145.92 5.72 246.00 7.42 548.42 69.93 825.34 9:43 Dec. 6, 2012
391.10 5.48 6.04 36.30 190.08 5.58 244.00 1.57 604.95 31.68 854.26
9:02 Dec. 7, 2012 312.10 5.82 5.98 28.12 172.80 5.87 235.00 2.82
516.64 0.00 950.24 8:49 Dec. 10, 2012 283.00 5.98 5.72 30.30 192.00
5.73 199.00 0.97 518.21 68.06 984.01 11:34 Dec. 10, 2012 276.50
5.97 5.16 29.20 176.64 5.76 203.00 1.74 440.27 29.60 953.80 14:18
Dec. 11, 2012 265.60 5.82 5.50 27.91 161.28 5.71 204.00 3.24 411.71
0.00 718.18 9:46 Dec. 11, 2012 263.10 5.91 5.36 26.76 159.36 5.69
197.00 0.78 320.22 621.20 710.93 12:04 Dec. 11, 2012 272.40 5.84
5.36 23.98 140.16 5.62 214.00 1.54 376.82 607.40 693.59 16:02 Dec.
12, 2012 236.90 6.08 5.69 18.74 144.00 5.92 193.00 0.56 291.39
565.78 369.53 9:09 Dec. 12, 2012 238.50 6.01 5.47 20.07 174.72 5.82
194.00 0.47 319.13 588.50 343.22 12:24 Dec. 12, 2012 248.50 5.83
5.33 19.77 192.00 5.79 187.00 0.69 325.57 657.16 344.06 14:09 Dec.
13, 2012 249.60 5.98 5.85 20.78 174.72 5.69 197.00 1.29 0.83 686.95
345.52 9:24 Dec. 13, 2012 245.20 5.96 5.70 23.00 186.24 5.70 191.00
0.82 285.02 672.70 363.64 11:38 Dec. 13, 2012 250.00 5.79 5.03
25.26 174.12 5.67 196.00 1.62 394.50 571.96 371.59 13:39 Dec. 14,
2012 226.10 5.75 5.25 42.70 165.12 5.82 174.00 1.21 417.07 429.11
332.80 8:26 Dec. 14, 2012 236.50 5.94 5.49 45.00 182.40 5.73 178.00
1.64 419.78 364.70 307.97 11:32 Dec. 14, 2012 215.10 5.82 5.54
524.00 196.20 5.61 193.00 1.86 457.41 368.67 339.61 16:15
TABLE-US-00002 TABLE 2 Grab S.sub.2O.sub.8 by DCS Sample DO
Conductivity lodometry ORP Dissolved Total Hg Selenite Selenate
Date/Time ORP (mV) pH (mg/L) (mS) (mg/L) pH (mV) Hg (.mu.g/L)
(.mu.g/L) (.mu.g/L) (.mu.g/L) Nov. 15, 2012 295.00 4.95 4.90 0.00
0.00 0.00 N/A 4.60 372.00 673.95 49.81 14:31 Nov. 16, 2012 275.30
5.34 6.21 39.60 96.00 0.00 N/A 2.97 404.00 780.82 54.52 12:22 Nov.
16, 2012 255.50 5.12 5.60 52.50 130.60 0.00 N/A 4.61 406.00 793.68
62.78 15:42 Nov. 17, 2012 260.80 5.68 5.98 31.70 105.60 0.00 N/A
5.26 434.00 901.84 60.18 12:57 Nov. 17, 2012 257.20 5.40 9.35 31.30
96.00 0.00 N/A 0.00 418.00 511.40 88.57 15:15 Nov. 18, 2012 246.90
5.31 5.72 34.20 109.44 0.00 N/A 7.50 445.00 851.21 64.96 9:26 Nov.
18, 2012 254.10 5.20 5.70 33.60 97.92 0.00 N/A 7.53 462.00 800.51
63.48 12:46 Nov. 18, 2012 276.90 5.21 5.61 33.10 97.92 0.00 N/A
9.20 447.00 788.90 67.89 15:28 Nov. 19, 2012 249.80 5.49 5.75 33.00
94.08 0.00 N/A 6.16 456.00 789.18 64.15 9:44 Nov. 19, 2012 256.70
5.67 5.71 31.10 72.00 0.00 N/A 12.40 458.00 753.51 56.41 13:25 Nov.
19, 2012 252.90 5.59 5.99 30.90 129.60 0.00 N/A 1.48 420.00 766.59
53.76 15:18 Nov. 26, 2012 557.20 5.66 4.63 24.11 357.12 0.00 N/A
297.00 436.00 0.00 3259.90 11:08 Nov. 26, 2012 531-557 5.59 4.92
24.45 458.90 5.64 524.00 335.00 466.00 0.00 3199.28 13:23 Nov. 26,
2012 546.90 5.71 4.75 24.88 403.20 5.63 525.00 322.00 446.00 0.00
3456.03 15:26 Nov. 27, 2012 564.30 5.42 5.24 22.18 328.32 5.58
513.00 334.00 437.00 0.00 3339.24 9:03 Nov. 27, 2012 547.00 5.55
4.87 27.60 378.24 5.62 520.00 333.00 411.00 0.00 3322.38 12:42 Nov.
27, 2012 548.00 5.55 4.90 28.56 359.04 5.53 519.00 372.00 477.00
0.00 3511.92 16:14 Nov. 28, 2012 548.00 5.65 4.75 32.00 366.72 5.52
519.00 391.00 499.00 0.00 4547.54 9:27 Nov. 28, 2012 564.00 5.53
5.36 24.60 364.80 5.54 523.00 408.00 528.00 0.00 4076.00 13:35 Nov.
28, 2012 526.00 5.67 5.27 32.40 345.60 5.44 491.00 414.00 483.00
0.00 3776.43 15:35 Nov. 29, 2012 570.60 5.41 5.15 26.87 357.12 5.55
540.00 384.00 493.00 0.00 3849.11 10:09 Nov. 29, 2012 534.90 5.61
6.36 24.95 351.36 5.75 511.00 401.00 465.00 0.00 3950.23 13:00 Nov.
29, 2012 549.00 5.45 4.99 32.40 334.08 5.51 537.00 396.00 514.00
0.00 3896.06 15:30 Nov. 30, 2012 520.30 5.37 5.21 33.00 362.88 5.66
505.00 325.00 408.00 0.00 2613.99 9:21 Nov. 30, 2012 494.00 5.65
4.88 0.00 343.68 5.72 472.00 269.00 405.00 0.00 2258.24 14:06 Nov.
30, 2012 522.00 5.62 4.62 34.60 339.84 5.74 457.00 278.00 382.00
0.00 2153.89 15:47 Dec. 1, 2012 542.00 5.48 4.96 24.81 389.76 5.65
513.00 219.00 322.00 0.00 2448.43 8:51 Dec. 1, 2012 511.00 5.65
5.23 25.60 418.56 5.67 493.00 206.00 351.00 0.00 2456.52 11:50 Dec.
1, 2012 520.20 5.60 4.94 24.65 397.44 5.74 504.00 197.00 320.00
0.00 2352.68 14:22 Dec. 2, 2012 527.00 5.72 5.22 28.22 405.12 0.00
450.00 240.00 355.00 0.00 2613.65 9:05 Dec. 2, 2012 509.50 5.68
4.85 27.42 418.56 5.83 497.00 220.00 354.00 0.00 2516.77 14:30 Dec.
2, 2012 505.10 5.69 5.14 27.10 455.04 5.84 495.00 226.00 330.00
0.00 2465.82 16:00 Dec. 3, 2012 508.80 5.61 4.99 25.87 472.32 5.79
511.00 224.00 360.00 0.00 2389.62 10:22 Dec. 3, 2012 510.90 5.40
5.72 35.10 456.96 5.76 510.00 235.00 349.00 0.00 2362.08 13:40 Dec.
3, 2012 513.10 5.53 4.81 33.80 460.80 5.77 511.00 214.00 346.00
6.69 2330.85 15:40 Dec. 4, 2012 522.10 5.54 4.89 31.40 458.88 5.78
511.00 205.00 302.00 10.04 2210.91 9:47 Dec. 4, 2012 513.00 5.79
5.46 31.60 470.40 5.84 502.00 212.00 309.00 0.00 2260.63 13:45 Dec.
4, 2012 519.40 5.49 5.10 30.80 470.40 5.65 508.00 192.00 328.00
0.00 2215.08 15:22 Dec. 5, 2012 527.30 5.45 4.62 24.94 464.64 5.63
536.00 188.00 300.00 0.00 2336.88 10:00 Dec. 5, 2012 579.20 5.20
5.00 24.24 399.36 5.42 553.00 84.20 281.00 0.00 2371.02 13:50 Dec.
5, 2012 534.40 5.38 5.23 28.85 412.80 5.36 561.00 136.00 298.00
0.00 2466.75 16:55 Dec. 6, 2012 579.60 5.25 5.19 24.09 416.60 5.46
556.00 110.00 316.00 0.00 3345.74 9:24 Dec. 6, 2012 531.30 5.52
5.46 24.48 444.48 5.45 557.00 119.00 338.00 0.00 3568.89 11:41 Dec.
6, 2012 560.10 5.56 5.56 22.66 359.04 5.50 560.00 148.00 329.00
0.00 3394.87 16:45 Dec. 7, 2012 600.20 5.37 5.32 22.80 359.04 5.35
575.00 193.00 281.00 0.00 3571.63 9:16 Dec. 7, 2012 632.10 5.32
5.82 22.87 353.28 5.25 575.00 219.00 348.00 0.00 3711.37 11:23 Dec.
7, 2012 627.20 5.32 5.16 27.60 349.44 5.28 572.00 190.00 315.00
0.00 3853.27 12:45 Dec. 13, 2012 337.80 7.35 8.85 13.38 136.32 7.77
350.00 26.80 144.00 77.98 1698.63 9:46 Dec. 14, 2012 246.30 6.52
6.31 20.40 307.20 6.53 463.00 2.54 131.00 316.49 1942.57 8:40
[0059] In one embodiment, the present invention permits control of
various compounds and/or species in the ART of a WFGD which in turn
can impact on the amount of total dissolved solids, selenite and/or
selenite, mercury, and/or boron in an effluent stream of a
WFGD.
[0060] In another embodiment, the present invention is directed to
a method of controlling one or more upstream parameters so as to
control the oxidation-reduction potential (ORP) in an absorber
recirculation tank (ART). In one embodiment, it is desirable to
control both the pH of the ART as well as the ORP therein. While
not wishing to be bound to any one theory, in one embodiment the
present invention is directed to controlling one or more upstream
parameters so as to impact the pH and ORP in an ART. In one
embodiment, it is desirable to achieve a pH of less than about 7,
less than about 6.5, or even less than about 6 while at the same
time controlling various factors that impact on the ORP (e.g., ESP
sparking, the type and/or concentration of one or more oxidizers,
etc.) so that the ORP is less than about 500 mV, less than about
450 mV, less than about 400 mV, less than about 350 mV, or even
less than about 300 mV. Here, as well as elsewhere in the
specification and claims, individual numerical values can be
combined to form additional and/or non-disclosed ranges. As would
be appreciated by those of skill in the art, oxidation-reduction
potential when measured at a pH of about 7 can generally range from
a low of -0.8 V to a high of 1.2 V. It should also be noted that pH
can influence the oxidation-reduction potential number. As such,
the above range generally applies to the typical
oxidation-reduction potential range when measured at pH 7. At other
pHs different broad ranges could apply.
[0061] Accordingly, in another embodiment the present invention
relates to one or more methods by which to control the ORP in an
ART so as to reduce same. The reduction of the ORP in an ART can,
in one embodiment, result in the formation of more desirable
species and/or forms of one or more metals including, but not
limited to, selenium, mercury, magnesium, cobalt, etc. As a
non-limiting example, when the ORP in an ART is less than about 500
mV, less than about 450 mV, less than about 400 mV, less than about
350 mV, or even less than about 300 mV, the amount of selenium (IV)
tends to be higher than when the ORP is above 500 mV. As an
example, at an ORP of more than about 400 mV the amount of selenium
(VI) tends to be much greater than the amount of selenium (IV) in
an ART slurry and/or solution. Additionally, as the ORP in an ART
slurry and/or solution further decreases below 400 mV (e.g., below
about 350 mV, or below about 325 mV, or even below 300 mV), the
amount of selenium (VI) decreases and the amount of selenium (IV)
increases. While not wishing to be bound to any one theory, it is
believed that when the ORP in an ART slurry and/or solution is
above 500 mV almost all, if not all, of the selenium present in the
ART slurry and/or solution is in the form of selenium (VI) which in
turn facilitates, or highly favors, the formation of various
aqueous soluble selenium compounds and/or ions (e.g., selenate
ions). This in turn results in selenium being undesirably
discharged from one or more aqueous effluent streams and may, in
the future, require additional emissions control technologies to
reduce the amount of selenium emitted in various effluent streams.
Thus, in various situations, it is desirable to control the ORP in
an ART to thereby achieve at least some level of control over
selenium speciation and in turn mitigate, reduce and/or control the
concentration of various aqueous soluble selenium compounds and/or
ions in various aqueous effluent streams. Given this, a reduction
in the ORP in an ART below about 500 mV, below about 450 mV, below
about 400 mV, below about 350 mV, or even below about 300 mV,
results in at least some reduction, mitigation and/or control of
the amount of aqueous soluble selenium compounds and/or ions that
are emitted from one or more effluent streams from a WFGD.
Furthermore, any additional reduction in the ORP in an ART below
300 mV can result in even more selenium being speciated as selenium
(IV) and result in a further reduction, mitigation and control of
aqueous soluble selenium compounds and/or ions in one effluent
streams. Here, as well as elsewhere in the specification and
claims, individual numerical values can be combined to form
additional and/or non-disclosed ranges.
[0062] It should be noted that in some embodiments of the present
invention it might be more desirable to mitigate, control and/or
reduce the emission of one or more compounds and/or ions even if
such mitigation, control and/or reduction causes an increase in the
emission of one or more different compounds, ions and/or
pollutants. In such cases, a second and different technology can be
used to mitigate, reduce and/or control the emission of any such
different compound, ion and/or pollutant which, although
undesirable, is emitted at an increased level. As a non-limiting
example, one might desire to have a higher degree of mitigation,
reduction and/or control over selenium speciation. However, this
may result in an undesirable increase in the emission of one or
more other compounds, ions and/or pollutants (e.g., mercury
reemission). Accordingly, rather than trying to achieve an ORP in
the ART that impacts favorable on every compound, ion and/or
pollutant that one is seeking to mitigate, reduce and/or control,
in some instances it could be, and typically is, desirable to
utilize one or more other emissions control technologies to deal
with any other compounds, ions and/or pollutants that may be
emitted at an undesirable and/or increased amount (e.g., mercury
reemission). In still another embodiment, it might be desirable to
control, reduce and/or mitigate the type, amount and/or speciation
of various other compounds, ions and/or pollutants via control of
the ORP in an ART that will be unfavorable to selenium speciation
while using a different emissions control technology to deal with
any selenium that is emitted from one or more aqueous effluent
streams or other emissions points. In summation, it might be
necessary to "choose" a given ORP in an ART with the knowledge that
by doing so one might selectively control a certain portion of
total compounds, ions and/or pollutants that are sought to be
controlled. Regarding the compounds, ions and/or pollutants that
are not controlled via the selection of a favorable ORP in an ART
for such a control process, these compounds, ions and/or pollutants
could be controlled by one or more other emissions control
technologies that do not solely depend on the ORP value in the
ART.
[0063] In still another embodiment, when it is desired to control
selenium speciation as well as mercury speciation, the present
invention relates to a method that permits one to control the
oxidation-reduction potential (ORP) in an ART so as to be in the
range of about 300 mV to about 500 mV. While not wishing to be
bound to any one theory, it is believed that at the typical pHs
present in an ART when the ORP in such an ART is in a range of
about 300 mV to about 500 mV, mercury ions (e.g., in the form of
mercury (II) and/or mercury (IV)) are the predominant species of
mercury present in an WFGD instead of elemental mercury)(Hg.sup.0).
This in turn permits one to reduce the amount of mercury reemission
that occurs from a WFGD as mercury ions (e.g., in the form of
mercury (II) and/or mercury (IV)) can be controlled via a number of
technologies that result in mercury recapture in a WFGD.
[0064] In still another embodiment, the present invention seeks to
control the ORP in an ART so as to mitigate, reduce and/or control
the amount, type and/or concentration of one or more oxidizers in a
WFGD and/or the ART of a WFGD. Another benefit of this embodiment
of the present invention is that it results in a reduction in the
generation of various gaseous species from the ART of a WFGD. For
example, when the ORP in an ART is above about 500 mV various
gaseous forms of the halogens can be generated. Such halogen gas
generation is undesirable as it can lead to corrosive compounds
escaping the ART of a WFGD and causing corrosion issues in one or
more downstream emissions control devices.
[0065] Given the above, in one embodiment the present invention
relates to a method for controlling at least one parameter that is
directly, or indirectly, linked to a combustion process (e.g., a
fossil fuel-based combustion process, biomass combustion process,
etc.) in order to optimize at least one downstream emissions
control device (e.g., a wet flue gas desulfurization unit, an SCR,
an ESP, a baghouse or other particulate collection device, etc.).
In another embodiment, the present invention relates to a method
for controlling at least one parameter that is directly, or
indirectly, linked to a combustion process (e.g., a fossil
fuel-based combustion process, biomass combustion process, etc.) in
order to optimize at the oxidation-reduction potential in at least
one downstream wet flue gas desulfurization unit.
[0066] In another embodiment the present invention relates to a
method for controlling at least one parameter that is directly, or
indirectly, linked to one or more emissions control device, or
technology, in order to optimize at least one other upstream and/or
downstream emissions control device (e.g., a wet flue gas
desulfurization unit, an SCR, an ESP, a baghouse or other
particulate collection device, etc.). In another embodiment, the
present invention relates to a method for controlling at least one
parameter that is directly, or indirectly, linked to one or more
emissions control device, or technology, in order to optimize at
least the oxidation-reduction potential in at least one wet flue
gas desulfurization unit.
[0067] In still yet another embodiment, the present invention
relates to a method for controlling at least one parameter that is
directly, or indirectly, linked to a combustion process (e.g., a
fossil fuel-based combustion process, biomass combustion process,
etc.) in combination with controlling at least one parameter that
is directly, or indirectly, linked to one or more emissions control
device, or technology in order to optimize at least one other
upstream and/or downstream emissions control device (e.g., a wet
flue gas desulfurization unit, an SCR, an ESP, a baghouse or other
particulate collection device, etc.). In still yet another
embodiment, the present invention relates to a method for
controlling at least one parameter that is directly, or indirectly,
linked to a combustion process (e.g., a fossil fuel-based
combustion process, biomass combustion process, etc.) in
combination with controlling at least one parameter that is
directly, or indirectly, linked to one or more emissions control
device, or technology in order to optimize at least the
oxidation-reduction potential in at least one wet flue gas
desulfurization unit.
[0068] While specific embodiments of the present invention have
been shown and described in detail to illustrate the application
and principles of the invention, it will be understood that it is
not intended that the present invention be limited thereto and that
the invention may be embodied otherwise without departing from such
principles. In some embodiments of the invention, certain features
of the invention may sometimes be used to advantage without a
corresponding use of the other features. Accordingly, all such
changes and embodiments properly fall within the scope of the
following claims.
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