US008303919B2 

(12) Ulllted States Patent (10) Patent N0.: US 8,303,919 B2 

Gadgil et al. (45) Date of Patent: Nov. 6, 2012 

(54) SYSTEM AND METHOD FOR PROTECTION 20027050059204 21* 11/200? Thubetl Mk‘ 1 423/244 04 sy uevs 1yeta. .. . 

0F SCR CATALYST AND CONTROL OF 2005/0261122 A1 * 11/2005 Quesada Perez et al. ..... .. 502/80 

MULTIPLE EMISSIONS 2007/0140940 A1 6/2007 Varma et al. 

2007/0243996 A1 * 10/2007 Pujado .......................... .. 502/38 

(75) Inventors: Mandar R. Gadgil, Akron, OH (US); S. 2010/0273643 A1 10/2010 Gadgil et al. 

Behrooz Ghorishi, UniontoWn, OH OTHER PUBLICATIONS 

(US); Bryan J. Jankura, UniontoWn, 

OH (Us) W.A. Punjak et al.; Aluminosilicate Sorbents for Control of Alkali 

Vapors during Coal Combustion and Gasi?cation; Energy and Fuels, 

(73) Assignee: Babcock & Wilcox Power Generation vol. 2(5), 1988, pp. 702 to 708. 

Group, Inc,’ Barbertons OH (Us) W.A. Punjaket al.; High-TemperatureAdsorption ofAlkaliVapors on Solid Sorbents; AIChE Journal, vol. 35(7), Jul. 1989, pp. 1186 to 

( * ) Notice: Subject to any disclaimer, the term of this 1194 

patent is extended or adjusted under 35 M. Uberoi et al.; The Kinetics and Mechanism of Alkali Removal 

from Flue Gas by Solid Sorbents; Progress in Energy and Combus 

USC‘ 1546)) by 0 days‘ tion Science, vol. 16(4), 1990, pp. 205 to 211. 

M. Uberoi et al.; Aluminosilicates as Potential Sorbents for Control 

(21) Appl' NO" 12/909’753 ling Metal Emissions; Clean Energy from Waste and Coal, ACS 

22 F1 d‘ 0 t 21 2010 Symposium, 1992, pp. 214 to 222. 

( ) 1 e ' c ‘ ’ P.O. MWabe et al.; Mechanisms Governing Trace Sodium Capture by 

_ _ _ Kaolinite in a Down?ow; Twenty-Sixth Symposium (International) 

(65) Pnor Pubhcatlon Data on Combustion, The Combustion Institute, 1996, pp. 2447 to 2453. 

BM. Steenari et al.; High-Temperature Reactions of Straw Ash and 

Us 2012/0100052 A1 Apr' 26’ 2012 the Anti-Sintering Additives Kaolin and Dolomite; Biomass and 

(51) Int Cl Bioenergy, vol. 14(1), Mar. 1998, pp. 67 to 76. 

B01D 53/46 (2006.01) (Continued) 

B01D 53/64 (2006.01) 

B01J 33/00 (2006.01) Primary Examiner * Timothy Vanoy 

(52) U.S. Cl. ....... .. 423/210; 502/439; 502/520; 502/521 (74) Attorney, Agent, or Firm * Eric Marich 

(58) Field of Classi?cation Search ................ .. 423/210; 

502/439, 520, 521 (57) ABSTRACT 

See application ?le for Complete Search history- The present invention relates generally to the ?eld of emis 

_ sion control equipment for boilers, heaters, kilns, or other ?ue 

(56) References Clted gas-, or combustion gas-, generating devices (e.g., those 

4,061,716 

4,572,085 

4,843,980 

4,871,522 

4,925,633 

5,540,897 

5,567,394 

US. PATENT DOCUMENTS 

12/1977 

2/1986 

7/1989 

10/1989 

5/1990 

7/1996 

10/1996 

Doyle 

Doyle 

McGauley 

Hepworth 

Markham et al. 

Chu et al. 

Chu et al. 

140 

a 11 GOAL 

1 1o PULV. 

located at poWer plants, processing plants, etc.) and, in par 

ticular to a neW and useful method and apparatus for prevent 

ing the poisoning and/or contamination of an SCR catalyst. In 

another embodiment, the method and apparatus of the present 

invention is designed to protect an SCR catalyst, While simul 

taneously providing emission control. 

26 Claims, 1 Drawing Sheet 

20 
US 8,303,919 B2 

Page 2 

OTHER PUBLICATIONS 

S .Q. Turn et al.; A Review of Sorbent Materrials for Fixed Bed Alkali 

Getter Systems in Biomass Gasi?er Combined Cycle Power Genera 

tion Applications; Journal of the Institute of Energy, vol. 71, Dec. 

1998, pp. 163 to 177. 

SB. Davis et al.; Competition for Sodium and Toxic Metals Capture 

on Sorbents; Aerosol Science and Technology, vol. 32(2), Feb. 2000, 

pp. 142 to 151. 

M. Ohman et al.; The Role of Kaolin in Prevention of Bed Agglom 

eration during FluidiZed Bed Combustion of Biomasss Fuels; Energy 

& Fuels, vol. 14, 2000, pp. 618 to 624. 

V. V. Lissianski et al.; Utilization of Iron Additives for Advanced 

Control of NOx Emissions from Stationary Combustion Sources; 

Ind. Eng. Chem. Res. 2001 (published on the Internet on Jun. 22, 

2001), 40, pp. 3287 to 3293. 

SQ. Turn et al.; An Experimental Investigation of Alkali Removal 

from Biomass Producer Gas Using a Fixed Bed of Solid Sorbent; Ind. 

Eng. Chem. Res., vol. 40, 2001, pp. 1960 to 1967. 

T.K. Gale et al.; High-Temperature Interactions Between Multiple 

Metals and Kaolin; Combustion and Flame vol. 131 (3), Nov. 2002, 

pp. 299 to 307. 

T.K. Gale et al.; Mechanisms and Models Describing Sodium and 

Lead Scavenging by a Kaolinite Aerosol at High Temperatures; Aero 

sol Science and Technology, vol. 37, 2003, pp. 865 to 876. 

T. Ake et al.; Limestone Injection for Protection of SCR Catalyst; 

Riley Power, Duke Energy, Cormetech, Inc. Paper #175, 2003. 

K.Q. Tran et al.; On the Application of Surface Ionization Detector 

for the Study of Alkali Capture by Kaolin in a Fixed Bed Reactor; 

Fuel, vol. 83(718), May 2004, pp. 807-812. 

Q.K. Tran et al.; Capture of Potassium and Cadmium by Kaolin in 

OxidiZing and Reducing Atmospheres; Energy & Fuels, vol. 18, 

2004, pp. 1870 to 1876. 

K.Q. Tran et al.; A Kinetic Study of Gaseous Alkali Capture by 

Kaolin in the Fixed Bed Reactor Equipped with an Alkali Detector; 

Fuel, vol. 84(2/3), Jan/Feb. 2005, pp. 807-812. 

V. Kroger; Poisoning of Automotive Exhaust Gas Catalyst Compo 

nentsiThe Role of Phosphorus in the Poisoning Phenomena; Aca 

demic Dissertation, University of Oulu, Finlandi2007. 

B. Jens et al.; The Behavior of Particle Bound Phosphorus During the 

Combustion of Phosphate Doped Coal; Fuel, 86, 2007 (available 

online Sep. 27, 2006), pp. 632 to 640. 

E. Matinde et al.; Phosphorus Gasi?cation from Sewage Sludge 

During Carbothermic Reduction; ISIJ International, vol. 48, 2008, No. 7, pp. 912 to 917. 

A. Tate et al.; Environmentally Sound Handling of Deactivated SCR 

Catalyst; Downloaded from the Internet on May 13, 2009 at http:// 

www.coalpowermag.com/environmenta1/ 13 6 .html. 

* cited by examiner 

US 8,303,919 B2 

1 

SYSTEM AND METHOD FOR PROTECTION 

OF SCR CATALYST AND CONTROL OF 

MULTIPLE EMISSIONS 

FIELD AND BACKGROUND OF THE 

INVENTION 

1. Field of the Invention 

The present invention relates generally to the ?eld of emis 

sion control equipment for boilers, heaters, kilns, or other ?ue 

gas-, or combustion gas-, generating devices (e.g., those 

located at poWer plants, processing plants, etc.) and, in par 

ticular to a neW and useful method and apparatus for reducing 

or preventing the poisoning and/ or contamination of an SCR 

catalyst. In another embodiment, the method and apparatus of 

the present invention is designed to protect the SCR catalyst. 

2. Description of the Related Art 

NO,C refers to the cumulative emissions of nitric oxide 

(NO), nitrogen dioxide (N02) and trace quantities of other 

nitrogen oxide species generated during combustion. Com 

bustion of any fossil fuel generates some level of NO,C due to 

high temperatures and the availability of oxygen and nitrogen 

from both the air and fuel. NO,C emissions may be controlled 

using loW NO,C combustion technology and post-combustion 

techniques. One such post-combustion technique involves 

selective catalytic reduction (SCR) systems in Which a cata 

lyst facilitates a chemical reaction betWeen NO,C and a reagent 

(usually ammonia) to produce molecular nitrogen and Water 

vapor. 

SCR technology is used WorldWide to control NO,C emis 

sions from combustion sources. This technology has been 

used Widely in Japan for NO,C control from utility boilers since 

the late 1970’s, in Germany since the late 1980’s, and in the 

US since the 1990’s. Industrial scale SCRs have been 

designed to operate principally in the temperature range of 

500° F. to 900° F., but most often in the range of 550° F. to 

750° F. SCRs are typically designed to meet a speci?ed NO,C 

reduction e?iciency at a maximum alloWable ammonia slip. 

Ammonia slip is the concentration, expressed in parts per 

million by volume, of unreacted ammonia exiting the SCR. 

For additional details concerning NO,C removal technolo 

gies used in the industrial and poWer generation industries, 

the reader is referred to Steam/its generation and use, 41“ 

Edition, Kitto and StultZ, Eds., Copyright 2005, The Babcock 

& Wilcox Company, Barberton, Ohio, U.S.A., particularly 

Chapter 34iNitrogen Oxides Control, the text of Which is 

hereby incorporated by reference as though fully set forth 

herein. 

Regulations issued by the EPA promise to increase the 

portion of utility boilers equipped With SCRs. SCRs are gen 

erally designed for a maximum e?iciency of about 90%. This 

limit is not set by any theoretical limits on the capability of 

SCRs to achieve higher levels of NO,C destruction. Rather, it is 

a practical limit set to prevent excessive levels of ammonia 

slip. This problem is explained as folloWs. 

In an SCR, ammonia reacts With NO,C according to one or 

more of the folloWing stoichiometric reactions (a) to (d): 

The above catalysis reactions occur using a suitable cata 

lyst. Suitable catalysts are discussed in, for example, US. Pat. 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

2 

Nos. 5,540,897; 5,567,394; and 5,585,081 to Chu et al., all of 

Which are hereby incorporated by reference as though fully 

set forth herein. Catalyst formulations generally fall into one 

of three categories: base metal, Zeolite and precious metal. 

Base metal catalysts use titanium oxide With small 

amounts of vanadium, molybdenum, tungsten or a combina 

tion of several other active chemical agents. The base metal 

catalysts are selective and operate in the speci?ed tempera 

ture range. The major draWback of the base metal catalyst is 

its potential to oxidiZe SO2 to S03; the degree of oxidation 

varies based on catalyst chemical formulation. The quantities 

of SO3 Which are formed can react With the ammonia carry 

over to form various ammonium-sulfate salts. 

Zeolite catalysts are aluminosilicate materials Which func 

tion similarly to base metal catalysts. One potential advantage 

of Zeolite catalysts is their higher operating temperature of 

about 9700 F. (5210 C.). These catalysts can also oxidiZe SO2 

to S03 and must be carefully matched to the ?ue gas condi 

tions. 

Precious metal catalysts are generally manufactured from 

platinum and rhodium. Precious metal catalysts also require 

careful consideration of ?ue gas constituents and operating 

temperatures. While effective in reducing NOX, these cata 

lysts can also act as oxidiZing catalysts, converting CO to CO2 

under proper temperature conditions. HoWever, SO2 oxida 

tion to S03 and high material costs often make precious metal 

catalysts less attractive. 

As is knoWn to those of skill in the art, various SCR cata 

lysts undergo poisoning When they become contaminated by 

various compounds including, but not limited to, certain 

phosphorus compounds such as phosphorous oxide (P0) or 

phosphorous pentoxide (P205). Additionally, certain com 

pounds that contain potassium (K), sodium (Na) and phos 

phorous (P) that are found in, or generated by, various coal 

based fuels are knoWn to cause rapid deactivation of SCR 

catalyst in full-scale units and also in slip-stream units. In 

these fuels, potassium and sodium are mainly in the form of 

organically bonded inorganics, or Water soluble salts, (see, 

e.g., Steenari et al.; Energy and Fuels; Vol. 18 (2004) 6, pp. 

1870 to 1876). This form of association in the fuel makes it 

very easy for potassium and sodium to vaporiZe during com 

bustion. Phosphorus can also be contained in the fuel Where it 

is organically bonded (as in the case in biomass) or inorgani 

cally bonded (as is the case in PoWder River Basin (PRB) 

coal). Phosphorus is released in the gas phase due to carbo 

ther'mic reduction reaction happening during char combus 

tion as folloWs: 

(see, e.g., Hino, et. al.;lSlJlnlernali0nal, Vol. 48 (2008)7, pp. 

912 to 917). Of particular concern With biomass, phosphorus 

is released in the gas phase as a result of the combustion 

process itself irrespective of Whether the combustion is staged 

or un-staged since phosphorus is organically associated With/ 

in the fuel. 

More particularly, as the SCR catalysts are exposed to the 

dust laden ?ue gas there are numerous mechanisms including 

blinding, masking and poisoning that deactivates the catalyst 

and causes a decrease in the catalyst’s performance over time. 

The mo st common catalyst poison encountered When burning 

eastern domestic coal (i.e., coal mined in the eastern United 

States) is arsenic. The most common catalyst poison encoun 

tered When burning Western domestic coal (i.e., coal mined in 

the Western United States) is phosphorus and calcium sulfate 

is the most common masking mechanism. The most common 

catalyst poisons encountered When burning biomass are typi 
US 8,303,9l9 B2 

3 

cally potassium and sodium, or potassium- and sodium-con 

taining compounds. One method of recycling the used cata 

lyst is the process called regeneration Washing or 

rejuvenation. The initial steps of the regeneration process 

involve the removal of these toxic chemicals by processing 

the catalysts through various chemical baths in Which the 

poisons are soluble. While this treatment process does an 

excellent job of removing the desired poisons it produces 

WasteWater With very high arsenic concentrations. 

Furthermore, as is knoWn to those of skill in the art, selec 

tive catalyst reduction (SCR) technology is used WorldWide 

to control NO,C emissions from combustion sources at high 

temperatures (550° F. to 750° F). High temperature SCR 

technology has been used in Japan for NO,C control from 

utility boilers since the late 1970s, in Germany since the late 

l980’s, in US since the 1990’s and in China since 2000. The 

function of the SCR system is to react NO,C With ammonia 

(NH3) and oxygen to form molecular nitrogen and Water. Due 

to anticipated requirements for loWer NO,C emission limits 

there is a groWing need to control NO,C emissions from lignite 

?red coal poWer plants in the US and Canada. Some lignite 

?red units are already in the process of retro?tting SCR to 

control NOX. Other units Will have to folloW suit in the near 

future. There is also an increasing trend to co-combust coal 

and biomass on existing units With or Without SCR. Some 

older units are completely sWitching from pulveriZed coal 

?ring to pulverized biomass combustion. These units even 

With biomass alone or With coal and biomass co-combustion 

Will have to comply With strict NO,C emissions. The most 

effective method of complying With loW NO,C emission 

requirements is by SCR technology. The main issue With SCR 

performance on these units is the deactivation of the catalyst. 

Both lignite and biomass fuels have potassium, sodium and 

phosphorous and/or various potassium, sodium and phospho rous compounds Which are knoWn catalyst poisons. These 

poisons attack the catalyst resulting in deactivation of the 

catalyst over a period of time, thereby shortening the cata 

lyst’s active life cycle. As a result of the deactivation, the 

catalyst cannot function to carry out NO,C reduction as effec 

tively for a longer period of time. Given this, the deactivation 

reduces the effective life cycle of a catalyst and as a result 

more frequent catalyst changes are needed for NO,C compli ance. Although, there are some catalyst vendors that claim 

resistance to arsenic poisoning of their catalysts via the use of 

molybdenum in the catalyst formulation, to date no catalyst 

have been brought to market that resist poisoning by various 

potassium, sodium and phosphorous compounds, their 

elemental species, or their ionic species. 

Additionally, beyond controlling NO,C emissions, other 

emission controls must be considered and/ or met in order to 

comply With various state, EPA and/or Clean Air Act regula 

tions. Some other emission controls Which need to be consid 

ered for boilers, heaters, kilns, or other ?ue gas-, or combus 

tion gas-, generating devices (e.g., those located at poWer 

plants, processing plants, etc.) include, but are not limited to, 

mercury, SOX, and certain particulates. 

Given the above, a need exists for a method that provides 

for an economical and environmentally suitable method and/ 

or system to remove the gaseous potassium, sodium and 

phosphorous compounds, their elemental species, or their 

ionic species from a combustion process prior to any phos 

phorus compounds poisoning a catalyst in an SCR. 

SUMMARY OF THE INVENTION 

The present invention relates generally to the ?eld of emis 

sion control equipment for boilers, heaters, kilns, or other ?ue 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

4 

gas-, or combustion gas-, generating devices (e. g., those 

located at poWer plants, processing plants, etc.) and, in par 

ticular to a neW and useful method and apparatus for reducing 

or preventing the poisoning and/ or contamination of an SCR 

catalyst. In another embodiment, the method and apparatus of 

the present invention is designed to protect an SCR catalyst. 

Accordingly, one aspect of the present invention is draWn 

to a method for increasing the active life of an SCR catalyst, 

the method comprising the steps of: (a) providing at least one 

kaolin-bearing compound to a combustion Zone or ?ue gas 

stream of a fumace, or boiler, prior to entry of the ?ue gas into 

an SCR; and (b) permitting the at least one kaolin-bearing 

compound to react With any gaseous potassium and/or 

sodium compounds, or potassium- and/or sodium-containing 

compounds present in the combustion Zone or ?ue gas prior to 

the entry of the ?ue gas into the SCR. 

In yet another aspect of the present invention, there is 

provided a method for increasing the active life of an SCR 

catalyst, the method comprising the steps of: (i) providing at 

least one kaolin-bearing compound to a combustion Zone of a 

furnace or boiler; and (ii) permitting the at least one kaolin 

bearing compound to react With any gaseous potassium and/ 

or sodium compounds, or potassium- and/or sodium-contain 

ing compounds present in the combustion Zone prior to the 

entry of the ?ue gas into an SCR, Wherein the kaolin-bearing 

compound is selected from one or more kaolin-containing 

clays, kaolinite-containing clays, kaolinite, or mixtures of tWo or more thereof. 

In yet another aspect of the present invention, there is 

provided a method for sequestering one or more potassium 

and/or sodium compounds, or potassium- and/or sodium 

containing compounds, in the form of one or more less reac 

tive sodium aluminosilicate-containing, or potassium alumi 

nosilicate-containing, compounds, the method comprising 

the steps of: (A) providing at least one kaolin-bearing com 

pound to a combustion Zone or ?ue gas stream of a furnace, or 

boiler; and (B) permitting the at least one kaolin-bearing 

compound to react With any potassium and/or sodium com 

pounds, or potassium- and/or sodium-containing compounds 

present in the combustion Zone or ?ue gas to form one or more 

less reactive sodium aluminosilicate or potassium alumino 

silicate compounds. 

In yet another aspect of the present invention, there is 

provided a method for increasing the active life of an SCR 

catalyst While concurrently controlling mercury in a gas, the 

method comprising the steps of: (I) providing at least one 

kaolin-bearing compound to a combustion Zone or ?ue gas 

stream of a fumace, or boiler, prior to entry of the ?ue gas into 

an SCR; (II) providing at least one iron-bearing halide com 

pound to a combustion Zone or ?ue gas stream of a furnace, or 

boiler, prior to entry of the ?ue gas into an SCR; (III) permit 

ting the kaolin portion of the at least one kaolin-bearing 

compound to react With any gaseous potassium and/or 

sodium compounds, or potassium- and/or sodium-containing 

compounds present in the combustion Zone or ?ue gas prior to 

the entry of the ?ue gas into the SCR; (IV) permitting the iron 

portion of the at least one iron-bearing halide compound to 

react With any gaseous phosphorus compounds, or phospho 

rus-containing compounds present in the combustion Zone or 

?ue gas prior to the entry of the ?ue gas into the SCR; and (V) 

permitting the halide portion of the at least one iron-bearing 

halide compound to react With any gaseous mercury com 

pounds, or mercury-containing compounds, present in the 

combustion Zone or ?ue gas. 

In yet another aspect of the present invention, there is 

provided a method for sequestering one or more potassium 

and/or sodium compounds, or potassium- and/or sodium 
US 8,303,919 B2 

5 

containing compounds, in the form of one or more less reac 

tive sodium aluminosilicate-containing, or potassium alumi 

nosilicate-containing, compounds, as Well as sequestering 

one or more phosphorus compounds, or phosphorus-contain 

ing compounds, in the form of one or more less reactive 

iron-phosphorus-containing compounds While concurrently 

sequestering mercury, the method comprising the steps of: (1) 

providing at least one kaolin-bearing compound to a combus 

tion Zone or ?ue gas stream of a furnace, or boiler; (2) pro 

viding at least one iron-bearing halide compound to a com 

bustion Zone or ?ue gas stream of a furnace, or boiler; (3) 

permitting the kaolin portion of the at least one kaolin-bear 

ing compound to react With any gaseous potassium and/or 

sodium compounds, or potassium- and/ or sodium-containing 

compounds present in the combustion Zone or ?ue gas to form 

one or more less reactive sodium aluminosilicate-containing, 

or potassium aluminosilicate-containing, compounds; (4) 

permitting the iron portion of the at least one iron-bearing 

halide compound to react With any gaseous phosphorus com 

pounds, or phosphorus-containing compounds, present in the 

combustion Zone or ?ue gas to form one or more less reactive 

iron-phosphorus-containing compounds; and (5) permitting 

the halide portion of the at least one iron-bearing halide 

compound to react With any gaseous mercury compounds, or 

mercury-containing compounds, present in the combustion Zone or ?ue gas. 

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 

speci?c bene?ts attained by its uses, reference is made to the 

accompanying draWings and descriptive matter in Which 

exemplary embodiments of the invention are illustrated. 

BRIEF DESCRIPTION OF THE DRAWINGS 

The sole FIGURE is a schematic representation of a typical 

fossil fuel burning facility With an SCR system, and Which 

includes a system for practicing the methods of the present 

invention. 

DESCRIPTION OF THE INVENTION 

While the present invention Will be described in terms of 

SCR systems Which use ammonia as the NO,C reducing agent, 

since ammonia is frequently preferred for economic reasons, 

the present invention is not limited to ammonia based sys 

tems. The concepts of the present invention can be used in any 

system Which uses an ammoniacal compound. As used in the 

present disclosure, an ammoniacal compound is a term meant 

to include compounds such as urea, ammonium sulfate, cya 

nuric acid, and organic amines as Well as ammonia (NH3). 

These compounds could be used as reducing agents in addi 

tion to ammonia, but as mentioned above, ammonia is fre 

quently preferred for economic reasons. Some non-ammo 

niacal compounds such as carbon monoxide or methane can 

be used as Well, but With loss in effectiveness. 

As used herein, the terms “-bearing compound(s)” and 

“-containing compound(s)” are used interchangeably. For 

example, the terms “kaolin-bearing compoun ” and “kaolin 

containing compound” are to be construed as the same and as 

noted above are utiliZed interchangeably. As Would be appar 

ent, this distinction applies equally to all terms that utiliZe the 

same constructs noted herein. Additionally, as used herein, 

the term “gas phase” includes and/ or encompasses both a 

compound, or compounds, in a gaseous state as Well as the 

same compound, or compounds, in an aerosol state. Also, as 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

6 

used herein, the term “species” includes both a compound 

and/or an element in an ionic form/ state as Well as a com 

pound and/or an element in a atomic form/ state. 

Although the present invention is described in relation to a 

boiler, or a fossil fuel boiler, it is not limited solely thereto. 

Instead, the present invention can be applied to any combus 

tion source that generates NO,C regardless of Whether such a 

combustion source is utiliZed in conjunction With a boiler, or 

a steam generator. For example, the present invention could 

be used in combination With a kiln, a heater, or any other type 

of combustion process that generates, in Whole or in part, a 

?ue gas or combustion gas containing NOX. Accordingly, the 

description beloW is to be construed as merely exemplary. 

As illustrated in the FIGURE, the present invention may be 

applied to a boiler installation Which employs a Wet ?ue gas 

desulfuriZation (WFGD or Wet scrubber) for removal of sul 

fur oxides from the ?ue gases, as shoWn in the upper right 

hand side of the FIGURE. In this con?guration, the Wet 

scrubber is typically preceded (With respect to a direction of 

?ue gas ?oW through the system) by a particulate collection 

device (PCD), advantageously a fabric ?lter (FF) bag house, or an electrostatic precipitator (ESP). If desired, there may 

also be provided a Wet electrostatic precipitator (Wet ESP or 

WESP) Which may be provided as a ?nal “polishing” stage 

for ?ne particulate or SO3. Alternatively, the present inven 

tion may be applied to a system Which employs a spray dryer 

apparatus (SDA) or dry scrubber for removal of sulfur oxides 

from the ?ue gases, as shoWn in the loWer right-hand side of 

the FIGURE. In this con?guration, the SDA or dry scrubber is 

typically folloWed (With respect to a direction of ?ue gas ?oW 

through the system) by a particulate collection device (PCD), 

advantageously a fabric ?lter or baghouse, an electro 

static precipitator (ESP) or even a Wet electrostatic precipita 

tor (Wet ESP). 

Additionally, the present invention can be applied to any 

SCR catalyst that is adversely affected by poisoning With a 

phosphorus-based compound such as, but not limited to, 

H3PO4, PO or P2O5, potassium-based compounds such as, 

but not limited to, potassium chloride (KCl) and/orpotassium 

sulfate (K2SO4), and/or sodium-based compounds such as, 

but not limited to, sodium chloride (NaCl) and/or sodium 

sulfate (Na2SO4).As such, the present invention is not limited 

to any one type of SCR catalyst, but rather is broadly appli 

cable to a Wide range of SCR catalyst systems. Suitable 

catalyst systems for Which the present invention is applicable 

include, but are not limited to, honeycomb, plate or corru 

gated type con?gurations. 

In one embodiment, the present invention is directed to 

reducing the rate of SCR catalyst deactivation on PoWder 

River Basin (PRB) coal combustion units. It should be noted 

that although the present invention is described in relation to 

PRB coal, the present invention is not limited thereto. Rather, 

the present invention is broadly applicable to any situation 

Where an SCR catalyst is poisoned by one or more gaseous 

phosphorus compounds, one or more gaseous potassium 

compounds, one or more gaseous sodium compounds, and/or 

any combination of tWo or more of such compounds. 

In one embodiment, phosphorous in PRB coal is suspected 

to cause rapid deactivation in staged combustion and other 

units. This deactivation is suspected to be caused by gas phase 

phosphorus released via carbothermic reduction reaction. In 

this reaction under oxygen de?cient conditions, phosphorus 

bearing compounds release gas phase phosphorus by the fol 

loWing reaction: 

P2O5(solid phase compounds)+3C(s)—>2PO(g)+ 

3CO(g). 
US 8,303,919 B2 

7 

This gas phase phosphorous attaches to the active sites 

Within the catalyst causing the deactivation of the sites for 

NO,C reduction. As a result of this deactivation the SCR cata 

lyst cannot carry out the NO,C reduction process to the same 

performance level as unused catalyst. 

In another embodiment, potassium, sodium, potassium 

containing compounds, and/or sodium-containing com 

pounds in PRB coal and/or biomass is/are suspected to cause 

rapid deactivation in staged combustion and other units. 

While not Wishing to be bound to any one theory, this deac 

tivation is suspected to be caused by gas phase potassium 

and/or sodium released via the combustion process due to 

presence of various potassium and/or sodium compounds in 

the coal and/or biomass. In this situation, the release of such 

alkali metal ions and/ or atoms occurs due to the temperatures 

utiliZed to conduct combustion of the coal and/ or biomass and 

the subsequent vaporization and/or dissociation of the afore 

mentioned potassium and/or sodium compounds. 

This gas phase potassium and/or sodium ions and/or atoms 

attach to the active sites Within the catalyst causing the deac 

tivation of such sites for NO,C reduction. As a result of this 

deactivation, the SCR catalyst cannot carry out the NO,C 

reduction process to the same performance level as unused 

and/ or “fresh” catalyst. 

In one embodiment, the present invention relates to a sys 

tem and method to prevent formation of gas phase potassium, 

sodium and/or phosphorus species in the combustion envi 

ronment thus reducing, mitigating and/ or eliminating the rate 

of SCR deactivation. In one embodiment, the present inven 

tion accomplishes the aforementioned goal by the addition of 

at least one kaolin-bearing compound, at least iron-bearing 

compound, or any suitable combination thereof to the PRB 

coal prior to combustion. 

In one embodiment, the kaolin-bearing compound(s) of the 

present invention is/are any kaolin-containing compound 

(e. g., kaolinite Which is a mineral that is contained in kaolin 

clays and Which has a chemical composition of Al2Si2O5 

(OH)4). Accordingly, as used herein, “kaolin” is de?ned to 

mean, and encompass, any clay that contains a suf?cient 

amount of kaolin therein (e.g., any clay that is at least 25 

Weight percent kaolin), or any clay or other compound that 

contains a suf?cient amount of the mineral kaolinite 

(Al2Si2O5 (OH)4) (e. g., any clay, or other compound, that is at 

least 25 Weight percent kaolinite). In another embodiment, 

the amount of kaolin in kaolin-containing compound is at 

least about 30 Weight percent, at least about 40 Weight per 

cent, at least about 50 Weight percent, at least about 60 Weight 

percent, at least about 70 Weight percent, at least about 75 

Weight percent, at least about 80 Weight percent, at least about 

90 Weight percent, or even at least about 95 Weight percent. In 

still another embodiment, any kaolin-containing compound 

regardless of kaolin content can be utiliZed in conjunction 

With the present invention so long as the kaolin content 

thereof is at least about 10 Weight percent. Here, as Well as 

elseWhere in the speci?cation and claims, individual range 

values can be combined to form additional and/or non-dis 

closed ranges. While not Wishing to be bound to any one 

theory, it is believed that the aluminosilicate portion of the 

kaolin reacts With “free” potassium and/or sodium ions that 

are generated due to the combustion of coal and/or biomass 

that contains various potassium, sodium and/ or phosphorous 

compounds to generate potassium and/or sodium alumino 

silicate compounds (e.g., NaAlSi3O8 and KAlSi3O8). This in 

turnpermits the sequestration of the potassium and/or sodium 

ions and/or atoms that Would otherWise be “free” to poison 

the SCR catalyst. 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

8 

Regarding any phosphorous compounds that are contained 

in the combustion gases, such compounds are sequestered via 

the inclusion of one or more iron-bearing compounds in com 

bination With a kaolin-bearing compound as de?ned above. 

Thus, in one embodiment, the present invention enables the 

sequestration of multiple species selected from potassium, 

sodium, phosphorus and any combination thereof. 

In one embodiment, the iron-bearing compound(s) of the 

present invention is/are any iron compound (e.g., an iron 

oxide compound) that is/are able to undergo reduction in the 

combustion environments common to boilers, furnaces, 

poWer plants, etc. In one particular embodiment, the iron 

bearing compound is iron (III) oxide (Fe2O3), also knoWn as red iron oxide or hematite. In the embodiment Where iron (III) 

oxide is utiliZed the reactions of interest that occur in the 

combustion portion of a boiler or furnace are as shoWn beloW: 

It should be noted that the Fe3O4, also knoWn as black iron 

oxide or magnetite, of the ?rst reaction above can also be 

Written more accurately as FeO.Fe2O3. The FeO or iron (II) 

oxide, also knoWn as ferrous oxide, Which is generated due to 

the reduction of Fe2O3 is then available to tie-up, bind and/or 

sequester any PO gas present in the combustion Zone, or the 

?ue gas, of a boiler, or fumace, prior to arrival at the SCR. 

This PO gas Will then form FeiP and/or FeiP4O com 

pounds in particulate phase prior to arrival at the SCR. The 

particulate Will pass through the catalyst and avoid the cata 

lyst deterioration. 

In another embodiment, the present invention can utilize 

iron (II) carbonate Which is converted to the desired iron (II) 

oxide in the combustion Zone via the reaction shoWn beloW: 

In still another embodiment, the present invention can uti 

liZe one or more iron halides. Suitable iron halides include, 

but are not limited to, iron (II) bromide, iron (III) bromide, 

iron (II) chloride, iron (III) chloride, iron (II) iodide, iron (III) 

iodate (Fe(IO3)3), or any mixture of tWo or more thereof. In 

still another embodiment, any one or more iron halides can be 

used in combination With another non-halide containing iron 

compound (e.g., iron (II) carbonate). In still another embodi 

ment, the present invention utiliZes a combination of iron (II) 

bromide and/or iron (III) bromide With iron (II) carbonate to 

control the amount of phosphorous in a ?ue gas, or combus 

tion gas While concurrently permitting the control of mercury 

compounds, or mercury-containing compounds, in a ?ue gas, 

or combustion gas. As used herein, mercury compounds, or 

mercury-containing compounds, include, but are not limited 

to, any compound that contains either oxidiZed mercury, or 

bound elemental mercury. In still another embodiment, the 

present invention is directed to concurrently permitting the 

control of mercury compounds, or mercury-containing com 

pounds, that contain primarily, or only, oxidiZed mercury. As 

used herein any iron compound, halide or otherwise, can be 

utiliZed in a hydrated or non hydrated form. As such, refer 

ence to any iron compound herein by de?nition includes any 

hydrated forms that exist Whether or not speci?cally men 

tioned by chemical formula. 

As is knoWn in the art, (see, e. g., United States Patent 

Application Publication No. 2008/ 0107579 DoWns et al. the 

text of Which is hereby incorporated by reference as though 

fully set forth herein) halide-containing compounds are uti 

liZed to oxidiZe elemental mercury present in a ?ue, or com 

bustion, gas. Due to this oxidation reaction, the halide portion 
US 8,303,919 B2 

9 

of a suitable halide-containing compound permits elemental 

mercury to be converted into a more favorable form for sub 

sequent capture, or sequestration, via one or more suitable 

environmental control technologies (e.g., a Wet scrubber or 

spray dry absorber (SDA), a ?ue gas desulfuriZation system 

(FGD), a poWdered activated carbon system (PAC), or a par 

ticulate collecting system such as a fabric ?lter (FF) or a 

electrostatic precipitator (ESP)). In one instance, as is knoWn 

in the art, the addition of one or more suitable halide-contain 

ing compounds also increases the amount of mercury that is 

particulate-bound. Given that numerous patents and pub 

lished applications detail the manner by Which suitable 

halide-containing compounds permit the increased recovery 

of mercury from a ?ue, or combustion, gas, a detailed discus 

sion hereof is omitted for the sake of brevity. 

As such, in still another embodiment, the present invention 

encompasses utiliZing at least one kaolin-bearing compound 

in conjunction With at least one iron halide compound in order 

to achieve a multi-faceted control of various gas phase potas 

sium, sodium, phosphorus and mercury compounds, ions 

and/ or atoms, as discussed above. 

In any of the above embodiments, one or more suitable 

kaolin-bearing compounds, one or more suitable iron-bearing 

compounds, one or more suitable iron halide compounds, or 

any mixture thereof can be added to the coal in the pulveriZer. 

In still another embodiment, one or more suitable kaolin 

bearing compounds, one or more suitable iron-bearing com 

pounds, one or more suitable iron halide compounds, or any 

mixture thereof of the present invention can be added to the 

combustion Zone of a boiler and/or furnace via a suitable 

supply line designed to deliver one or more poWderiZed com 

pounds to the combustion Zone of a furnace and/or boiler. To 

this end, the FIGURE illustrates several embodiments of 

suitable design schemes for accomplishing this result. 

Referring to the FIGURE, there is illustrated a schematic 

representation of a typical fossil fuel burning facility, gener 

ally designated 10, With an SCR system, and Which includes 

a system for practicing the methods of the present invention. 

As shoWn, boiler 12 is provided for extracting the heat from 

the combustion of a fossil fuel, such as coal, through com 

bustion With an oxidant, typically air. The heat is transferred 

to a Working ?uid, such as Water, to generate steam used to 

either generate poWer via expansion through a turbine gen 

erator apparatus (not shoWn) or for industrial processes and/ 

or heating. 

The raW coal 14 must be crushed to a desired ?neness and 

dried to facilitate combustion. RaW coal 14 is temporarily 

stored in a coal bunker 16 and then transferred by means of a 

gravimetric or volumetric feeder 18 to one or more coal 

pulveriZers 20. In the embodiment shoWn in the FIGURE, 

there are six (6) coal pulveriZers, identi?ed as coal pulveriZers 

A-F. As is knoWn to those skilled in the art, each coal pulver 

iZer 20 grinds the coal to a desired ?neness (e. g., 70% through 

200 mesh) and as it is ground, hot primary air from primary air 

fans (not shoWn) is conveyed into each coal pulveriZer 20 to 

preheat and remove moisture from the coal to desired levels as 

it is ground. The primary air is also used to convey the pul 

veriZed coal (PC) out of each coal pulveriZer 20 and delivers 

it along a plurality of pulverized coal supply lines (one such 

burner line is identi?ed at A in the FIGURE; a single coal 

pulveriZer 20 may supply coal through 4-8 pulveriZed coal 

supply lines) to the burners 22 on the front and rear Walls of 

the boiler 12. Typically, the burners 22 are located in spaced 

elevations on one or both of the opposed front and rear Walls 

of the boiler 12, or at the corners of the boiler in installations 

knoWn as comer-?red or tangentially-?red units (not shoWn). 

The present invention can be utiliZed in conjunction With, but 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

10 

is not limited solely to, single-Wall ?red, opposed-Wall ?red 

and comer- or tangentially-?red units. Typically, a single coal 

pulveriZer 20 only provides coal to a single elevation of 

burners 22 on a Wall. Thus, in the embodiment shoWn in the 

FIGURE, the six coal pulveriZers A-F supply corresponding 

burner elevations A-F. HoWever, as is knoWn to those skilled 

in the art, other pulveriZer and burner con?gurations are 

knoWn (e. g., single pulveriZers supplying burners on multiple 

Walls and/or elevations or multiple pulveriZers supplying 

burners on a single elevation) and the present invention 

applies to any such con?gurations. 

The combustion process begins in the burner Zone 24 of the 

boiler 12’s furnace 26, releasing heat and creating hot ?ue gas 

28 Which is conveyed upWardly to the upper portion 30 of the 

boiler 12, across heating surfaces schematically indicated as 

rectangles 32. The ?ue gas 28 is then conveyed across the 

heating surfaces in the pendant convection pass 34, into the 

upper portion 36 of the horiZontal convection pass 38. The 

?ue gas 28 is then conveyed through a selective catalytic 

reduction (SCR) apparatus 40 Where NO,C in the ?ue gas is 

reduced, and then through primary and secondary air heater 

devices schematically indicated at 42. The air heaters 42 

extract additional heat from the ?ue gas 28, loWering the 

temperature of the ?ue gas, and preheat the incoming air used 

for combustion. 

As illustrated in the FIGURE, and doWnstream of the air 

heaters 42, the ?ue gas 28 undergoes further treatment for the 

removal of particulates and sulfur oxides. TWo typical con 

?gurations of the doWnstream equipment employed to 

accomplish these tasks are shoWn on the right-hand side of the 

FIGURE. The upper equipment con?guration in the FIGURE 

comprises a particulate collection device (PCD) schemati 

cally indicated at 44, for removal of particulates from the ?ue 

gas 28, and Which may comprise in practice a fabric ?lter or 

an electrostatic precipitator. Downstream of the PCD 44 there 

is provided a Wet ?ue gas desulfuriZation (WFGD) device, 

also knoWn as a Wet scrubber, for removal of sulfur oxides 

from the ?ue gas 28. The cleaned, scrubbed ?ue gas may 

(optionally) be conveyed through a Wet ESP 47 for removal of 

?ne particulate or S03, and then conveyed to stack 48 for 

discharge to the atmosphere. 

The loWer equipment con?guration in the FIGURE com 

prises a spray dryer apparatus (SDA) schematically indicated 

at 50, also knoWn as a dry scrubber, for removal of sulfur 

oxides from the ?ue gas 28. Downstream of the SDA 50 there 

is provided a particulate collection device (PCD) 44, as 

described above, for removal of particulates from the ?ue gas 

28. The cleaned, scrubbed ?ue gas is then conveyed to stack 

48 for discharge to the atmosphere. 

In order to further reduce NO,C emissions, some boilers 12 

employ staged combustion Wherein only part of the stoichio 

metric amount of air is provided in the main burner Zone 24, 

With the balance of the air for combustion, together With any 

excess air required due to the fact that no combustion process 

is 100 percent e?icient, is provided above the burner Zone 24 

via over ?re air (OFA) ports 52. If staged combustion is 

employed in a boiler 12, due to the reduced air supplied to the 

burner Zone 24, a reducing atmosphere is created in the loWer 

portion of the furnace 26, including the hopper region 54. 

In accordance With a ?rst embodiment of the present inven 

tion, one or more suitable kaolin-bearing compounds, one or 

more suitable iron-bearing compounds, one or more suitable 

iron halide compounds, or any mixture thereof is/ are added to 

the one or more coal pulveriZers 20 prior to supplying the 

pulverized coal to the one or more burners 22. The system and 

apparatus for accomplishing this desired result is also shoWn 

in the FIGURE, generally designated 100. The system 100 
US 8,303,919 B2 

11 

comprises a storage means 120 for temporarily storing the 

potassium, sodium, phosphorous and/or mercury reduction/ 

sequestration compound, generally designated 110; delivery means 130, 135 for conveying the compound(s) 110 to a 

desired location, including valves, seals, etc. as required; and 

control means 150, advantageously microprocessor-based 

control means, Which are accessed via an operator via human 

operator interface (I/O) station 160, Which includes display 

and data collection and storage means as required. In the 

FIGURE, the raW coal 14 to Which compound(s) 110 has/ 

have been added is referred to as 140. Advantageously, com 

pound(s) 110 may be provided along With the raW coal 14 via 

the feeder 18, Which permits close control and measurement 

of the delivery of both raW coal 14 and compound(s) 110 into 

the coal pulverizer 20. Alternatively, compound(s) 110 may 

be provided directly into the coal pulverizer 20 and/ or directly 

into one or more individual burner lines A-F providing the 

pulverized coal to individual burners 22, With suitable sealing 

devices against the positive pressure Within the coal pulver 

izer 20 or burner lines A-F. The delivery means may be 

slurry-based or pneumatic as required by the particulars of 

compound(s) 110 and the amount and location of introduc 

tion into the ?ue gas 28. An interconnected arrangement of 

control or signal lines 170, 180, 190 and 195 interconnect 

these various devices to provide control signals, compound(s) 

110 level signals, and potassium, sodium, phosphorous and/ 

or mercury level signals in the ?ue gas 28 (from a sensor 200) 

to permit the introduction of the potassium, sodium, 

phosphorous and/ or mercury reducing/ sequestration com 

pound(s) 110 into the ?ue gas 28 to be controlled by a human 

operator, or automatically controlled. HoWever, if a suitable, 

real-time sensor 200 for measuring levels of gaseous potas 

sium, sodium, phosphorous and/ or mercury in the ?ue gas 28 

is/are not available, ?ue gas samples may instead be taken at 

the location 200 for later laboratory analysis via suitable test 

methods, Which may be inductively coupled plasma-mass 

spectrometry (ICP-MS). Based upon the laboratory results, a human operator could then use the operator interface 160 to 

manually input a desired set-point into control means 150 for 

the amount of potassium, sodium, phosphorous and/or mer 

cury reducing/ sequestration compounds 110 introduced into 

the ?ue gas 28. Provided that subsequent laboratory analyses 

do not indicate any signi?cant variation in gaseous potas 

sium, sodium, phosphorous and/or mercury levels in the ?ue 

gas 28, there may be no need for real-time, close control of the 

introduction of potassium, sodium, phosphorous and/or mer 

cury reducing/sequestration compound(s) 110. Instead, the 

amount of potassium, sodium, phosphorous and/or mercury 

reducing/ sequestration compound(s) 110 introduced into the 

?ue gas 28 may be simply a function of boiler load or coal 

feed rate values. 

In still yet another embodiment, the present invention uti 

lizes at least one kaolin-bearing compound in combination 

With iron (II) oxide. In this embodiment, the need for a reduc 

tion reaction to occur is eliminated and the addition points for 

the iron (II) oxide of this embodiment are therefore broader 

then previous embodiments. In this case, the kaolin-bearing 

compound and the iron (II) oxide can be added at any suitable 

point post-combustion and pre-SCR in order to capture, 

reduce, tie-up, bind and/ or sequester any “free” gaseous 

potassium, sodium, phosphorus and/or mercury compounds, 

ions, and/or atoms present in the ?ue gas of a boiler, or 

furnace, prior to arrival at the SCR. In particular, the phos 

phorous reduction compound can be supplied at one or more 

of the locations G through Q shoWn in the FIGURE. More 

particularly, the potassium, sodium, phosphorous and/or mer 

cury reducing/sequestration compound(s) can also be pro 

5 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

12 

vided (e.g., either separately, independently, or in any com 

bination) into the ?ue gas 28 at one or more of the folloWing 

locations: 

G: into or beloW the burner zone 24, in one or more of the 

front, rear or side Walls, via means separate from the 

burners 22; 

H: into the furnace 26 at a location above the burner zone 

24, in one or more of the front, rear or side Walls; 

I, J: into the fumace 26 in the vicinity of or via the OFA 

ports 52 on one or both of the front or rear Walls; 

K: into the boiler 12 in the pendant convection pass 34; 

L: into the boiler 12 in the upper portion 36 of the horizon 

tal convection pass 38; 

M, N, O, P: into the boiler 12 in the horizontal convection 

pass 38; and/or 

Q: into the boiler 12 in the hopper region beloW the hori 

zontal convection pass 38. 

Given the above, the reduced iron, or iron (II) oxide, of the 

present invention is able to capture, reduce, tie-up, bind and/ 

or sequester the gas phase phosphorus in the form of iron 

phosphorus alloys Which upon coming in contact With the 

over ?re air from iron-phosphorus oxide compounds, While 

the kaolin-bearing compound is able to capture, reduce, tie 

up, bind and/or sequester any gas phase potassium and/or 

sodium compounds. This signi?cantly reduces the amount of 

gas phase potassium, sodium and/or phosphorus accumula 

tion in an SCR catalyst. Another advantage of the present 

invention is that through addition of kaolin and/or iron a 

signi?cant portion of any potassium, sodium and/or phospho rus present Will be aluminosilicate-bound and/ or iron-bound. 

While not Wishing to be bound to any one theory, alkali 

aluminosilicates are believed to be less likely to be in a gas 

phase state in the conditions commonly found in a combus 

tion process and/ or an SCR unit. This enables the minimiza 

tion of the amount potassium and sodium that is transferred to 

an SCR catalyst and thus available to poison the SCR catalyst. 

Additionally, Iron-bound phosphorus compounds are less 

leachable thereby minimizing the transfer of phosphorus to 

an SCR catalyst. Furthermore, phosphorus associated With 

and/or bound to an iron compound (e.g., an iron oxide) is 

more stable than phosphorus that is associated With and/or 

bound to a calcium compound (e.g., calcium oxide). Given 

this, the present invention is, in one embodiment, directed to 

the situation Where a majority of the potassium, sodium and/ 

or phosphorus present in the combustion and/ or ?ue stream is 

sequestered in a suitable alkali aluminosilicate compound 

and/or iron-phosphorus-oxygen-containing compound 

thereby substantially reducing the amount of “free” gaseous 

potassium-/sodium-containing compounds and/or calcium/ 

phosphorus/oxygen-containing compounds that are able to 

react With SOX. This in turn substantially reduces the amount 

of gaseous potassium-/sodium-containing compounds that 

can poison the SCR catalyst. Furthermore, the amount of 

gaseous phosphorus that is produced in the combustion and/ 

or ?ue gas stream is substantially reduced by restricting the 

amount of calcium/phosphorus/oxygen-containing com 

pounds that are present in the combustion and/or ?ue gas 

stream to react With various SO,C compounds resulting in the 

unWanted production of gaseous phosphorus compounds, or 

phosphorus/oxygen compounds, that can lead to the undes 

ired poisoning of an SCR catalyst. 

In still another embodiment, the one or more kaolin-bear 

ing compounds, and/or one or more iron-bearing compounds 

of the present invention can be added in any suitable manner, 

including the manner detailed in the FIGURE. Suitable 

kaolin-bearing compounds are detailed above. Suitable iron 

bearing compounds include, but are not limited to, aqueous 
US 8,303,919 B2 

13 

and soluble forms of iron-bearing compounds such as iron 

halides (e.g., iron chlorides, iron bromides, iron iodide, or 

iron iodate), metallic iron, one or more iron oxides, iron 

carbonate, or mixtures of tWo or more thereof. If an existing 

skid is used then one or more aqueous reagents can be 

pumped via positive displacement pumps from a storage tank 

to the one or more coal feeders Where the reagent is sprayed 

on the coal as the coal passes on a feeder belt upstream of the 

pulveriZers. 

In one embodiment, the present invention is advantageous 

in that it is applicable to both existing SCRs (retro?ts) and 

neW SCRs. Additionally, the present invention can be applied 

to plants that utiliZe biomass as a fuel source. In one embodi 

ment, implementation of the present invention can be accom 

plished in a cost-effective manner utiliZing loW cost hardWare 

designed to supply the necessary iron compound to a com 

bustion process. The present invention also does not affect the 

current design of boilers and SCRs. 

In one embodiment, the amount of the one or more kaolin 

bearing compounds and/or iron compound, or compounds, 

utiliZed in conjunction With the present invention varies 

depending upon the phosphorus content in the coal to be 

burned. As is knoWn to those of skill in the art, the potassium, 

sodium and/or phosphorus content of coal and/orbiomass can 

be determined by various knoWn methods. Thus, in this 

instance, the present invention is not limited to any one range, 

or amount, of kaolin-bearing compounds and/or iron-bearing 

compounds that are supplied/utiliZed. Instead, a stoichiomet 

ric ratio is utiliZed. In one embodiment, the stoichiometric 

ratio of potassium and/or sodium to kaolin-bearing com 

pound is in the range of about 1:3 to about 3:1, or from about 

1:2 to about 2:1, or from about 1:1.5 to about 1.5:1, or from 

about 111.25 to about 1.25:1, or even about 1:1. In one 

embodiment, the stoichiometric ratio of iron to phosphorus is 

in the range of about 1:3 to about 3:1, or from about 1:2 to 

about 2:1, or from about 1:1.5 to about 1.511, or from about 

111.25 to about 1.25:1, or even about 1:1. Here, as Well as 

elseWhere in the speci?cation and claims, individual range 

values can be combined to form additional and/or non-dis 

closed ranges. 

In another embodiment, the amount of kaolin-bearing 

compound, or compounds, and/or iron-bearing compound, or 

compounds, utiliZed in conjunction With the present inven 

tion is Within a given range When the fuel utiliZed is PoWder 

River Basin/Lignite coal, biomass, or any combination 

thereof. In this embodiment, the amount of the kaolin-bearing 

compound, or compounds, and/or iron-bearing compound, or 

compounds, to PoWder River Basin/Lignite coal, biomass, or 

any combination thereof, is expressed as the amount of 

kaolin-bearing compound, or compounds, and/or iron-bear 

ing compound, or compounds, (hereinafter referred to as just 

“kaolin” and/or “iron” in only this instance) in pounds for 

every 1,000 pounds of coal and/or biomass. In one embodi 

ment, the amount of kaolin and/or iron compound, or com 

pounds, utiliZed is in the range of about 0.7 pounds of 

“kaolin” and/or “iron” per 1,000 pounds of coal and/or bio 

mass to about 6 pounds of “kaolin” and/or “iron” per 1,000 

pounds of coal and/or biomass. In another embodiment, the 

amount of kaolin and/ or iron compound, or compounds, uti 

liZed is in the range of about 1 pound of “kaolin” and/ or “iron” 

per 1,000 pounds of coal and/ or biomass to about 5.5 pounds 

of “kaolin” and/or “iron” per 1,000 pounds of coal and/or 

biomass, or from about 1.5 pounds of “kaolin” and/or “iron” 

per 1,000 pounds of coal and/ or biomass to about 5 pounds of 

“kaolin” and/or “iron” per 1,000 pounds of coal and/or bio 

mass, or from about 2 pounds of “kaolin” and/or “iron” per 

1,000 pounds of coal and/or biomass to about 4.5 pounds of 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

14 

“kaolin” and/or “iron” per 1,000 pounds of coal and/or bio 

mass, or from about 2.5 pounds of “kaolin” and/or “iron” per 

1,000 pounds of coal and/or biomass to about 4 pounds of 

“kaolin” and/or “iron” per 1,000 pounds of coal and/or bio 

mass, or from about 3 pounds of “kaolin” and/or “iron” per 

1,000 pounds of coal and/or biomass to about 3.5 pounds of 

“kaolin” and/or “iron” per 1,000 pounds of coal and/or bio 

mass. Here, as Well as elseWhere in the speci?cation and 

claims, individual range values can be combined to form 

additional and/or non-disclosed ranges. 

In another embodiment, Wherein the iron portion of the 

present invention that is to be utiliZed for controlling various 

compounds in a ?ue gas, or combustion gas, of a 100 MWe 

coal and/ or biomass poWer plant is both iron (II) bromide and 

iron (II) carbonate, the injection rate for the iron (II) carbon 

ate is as discussed above While the iron (II) bromide is sup 

plied as a solution and at an amount in the range of about 0.25 

gallons per hour to about 10 gallons per hour, or from about 

0.5 gallons per hour to about 5 gallons per hour, or even from 

about 1 gallon per hour to about 4 gallons per hour. In another 

embodiment, Where just an iron halide is utiliZed (e.g., iron 

(II) bromide and/or iron (III) bromide) the amount of iron 

halide supplied to the ?ue gas, or combustion gas, is suf?cient 

to yield a concentration of bromide betWeen about 10 ppm to 

about 200 ppm, or from about 25 ppm to about 175 ppm, or 

from about 50 ppm to about 150 ppm. It should be noted that 

depending upon the emissions control technology in place on 

the device generating the ?ue gas, or combustion gas, it may 

be desirable to use a loWer bromide concentration in order to 

prevent any type of detrimental effects to such doWnstream 

emissions technology. In one embodiment of such an instance 

the concentration of bromide is betWeen about 10 ppm to 

about 125 ppm, or from about 25 ppm to about 100 ppm, or 

from about 50 ppm to about 75 ppm. Here, as Well as else 

Where in the speci?cation and claims, individual range values 

(even from different embodiments) can be combined to form 

additional and/or non-disclosed ranges. 

In light of the above, one of skill in the art Would recogniZe 

that the amount of kaolin compounds and/ or iron compounds 

necessary to supply the desired amount of kaolin, iron and/or 

halogen to a ?ue gas, or combustion gas, in accordance With 

the process of the present invention Will vary depending upon 

the siZe of the device generating such ?ue gas, or combustion 

gas. Thus, the present invention is not limited to any speci?c 

rate or range of supply. 

In another embodiment, for a 100 MWe coal and/or biom 

ass poWer plant the amount of iron (II) bromide solution (25 

Weight percent solution) supplied to the ?ue gas, or combus 

tion gas, is in the range of about 0.25 gallons per hour to about 

6 gallons per hour, or from 0.5 gallons per hour to about 5 

gallons per hour, or even from 1 gallon per hour to about 4 

gallons per hour. Here, as Well as elseWhere in the speci?ca 

tion and claims, individual range values can be combined to 

form additional and/ or non-disclosed ranges. HoWever, as is 

noted above, the present invention is not limited to solely 

these supply rates. Rather, any supply rate can be used in 

order to achieve the desired concentration of bromide and/ or 

iron. As Would be apparent to one of skill in the art, other 

additional factors can impact the amount of iron-bearing 

compounds supplied in connection With the various embodi 

ments of the present invention. Such additional factors 

include, but are not limited to, the amount and/or type of 

phosphorus present in the coal, or other combustible fuel; the 

siZe and/or output of the boiler, heater, kiln, or other ?ue gas-, 

or combustion gas-, generating device; and the desired sto 
US 8,303,919 B2 

15 

ichiometric ratio to be achieved; the type and/or manner of 

combustion, the type and/or arrangement of any applicable 

equipment or structure. 

In another embodiment, the one or more kaolin com 

pounds, and/or one or more iron compounds utiliZed in con 

junction With the present invention can be of any particle siZe 

and/or particle geometry. Suitable particle geometries 

include, but are not limited to, spherical, platelet-like, irregu 

lar, elliptical, oblong, or a combination of tWo or more dif 

ferent particle geometries. In one embodiment, the one or 

more kaolin compounds, and/ or one or more iron compounds 

of the present invention, if Water soluble and/or suspendible, 

can be supplied in solution and/or suspension form. In such an 

instance, a solution and/or suspension concentration of at 

least about 15 Weight percent of the one or more Water soluble 

and/or suspendible kaolin compounds and/or iron com 

pounds is/are utiliZed. In another embodiment, a solution 

and/or suspension concentration of at least about 20 Weight 

percent, at least about 25 Weight percent, at least about 30 

Weight percent, at least about 35 Weight percent, at least about 

40 Weight percent, at least about 45 Weight percent, or even at 

least about 50 Weight percent of more of the one or more Water 

soluble and/or suspendible kaolin compounds and/or iron 

compounds is utiliZed is utiliZed in conjunction With the 

present invention. Here, as Well as elseWhere in the speci? 

cation and claims, individual range values can be combined to 

form additional and/or non-disclosed ranges. As Would be 

appreciated by those of skill in the art, the solution and/or 

suspension concentration of any one or more Water soluble 

and/or suspendible kaolin compounds and/or iron com 

pounds should not, in one embodiment, exceed the solubility 

amount for the one or more iron compounds. 

In still another embodiment, the one or more kaolin com 

pounds and/or iron compounds of the present invention can 

be supplied in a poWdered form, a solution form, an aqueous 

suspension form, or any combination thereof. In the case of an 

aqueous suspension, the one or more kaolin compounds and/ 

or iron compounds utiliZed in conjunction With the present 

invention should have a suitable particle siZe. Additionally, 

even absent the desire to place the one or more kaolin com 

pounds and/ or iron compounds of the present invention into 

an aqueous solution, the one or more kaolin compounds and/ 

or iron compounds should have a suitable particle siZe that 

facilitates a higher degree of reactivity When placed into 

contact With a ?ue, or combustion, gas. In one embodiment, 

both of these conditions can be met, Whether individually or 

in combination, by one or more kaolin compounds and/ or iron 

compounds Where at least about 95 percent of the particles 

have a particle siZe of less than about 400 um (microns), 

Where at least about 95 percent of the particles have a particle 

siZe of less than about 350 um (microns), Where at least about 

95 percent of the particles have a particle siZe of less than 

about 300 um (microns), Where at least about 95 percent of the 

particles have a particle siZe of less than about 250 um (mi 

crons), Where at least about 95 percent of the particles have a 

particle siZe of less than about 200 um (microns), or even 

Where at least about 95 percent of the particles have a particle 

siZe of less than about 175 um (microns). Here, as Well as 

elseWhere in the speci?cation and claims, individual range 

values can be combined to form additional and/or non-dis 

closed ranges. 

Although not limited hereto, When utiliZed, a suitable iron 

compound for use in conjunction With the present invention is 

iron (II) carbonate available from Prince Agri Products (a 

subsidiary of Phibro Animal Health Corporation located in 

Ridge?eld Park, N.J.). This iron (II) carbonate is a poWdered 

compound Where at least about 95% of its particles are less 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

16 

than 200 um (microns) in siZe. Additionally, the concentra 

tion of iron (II) carbonate in this product is about 80 percent 

by Weight With substantially all of the remaining 20 Weight 

percent being non-reactive in light of the use here. 

In the instance Where an aqueous suspension is utiliZed in 

conjunction With the present invention, such an aqueous sus 

pension can further comprise a suitable amount of one or 

more anti-settling, suspension, thickening or emulsi?cation 

agents. Suitable anti-settling, suspension, thickening or 

emulsi?cation agents include, but are not limited to, sodium 

polyacrylates, carbomers, acrylates, inorganic thickening 

agents. Other suitable anti-settling, suspension, thickening or 

emulsi?cation agents are knoWn to those of skill in the art and 

as such a discussion herein is omitted for the sake of brevity. 

In another embodiment, a suitable suspension or emulsi?ca 

tion can be achieved via agitation and does not necessarily 

require the use of one or more anti-settling, suspension, thick 

ening or emulsi?cation agents. In another embodiment, a 

combination of one or more anti-settling, suspension, thick 

ening or emulsi?cation agents can be utiliZed in combination 

With agitation. In still another embodiment, the one or more kaolin com 

pounds and/or iron compounds of the present invention 

should have a purity of at least about 50 Weight percent, at 

least about 55 Weight percent, at least about 60 Weight per 

cent, at least about 65 Weight percent, at least about 70 Weight 

percent, at least about 75 Weight percent, at least about 80 

Weight percent, at least about 85 Weight percent, at least about 

90 Weight percent, at least about 95 Weight percent, or even at 

least about 99 Weight percent or higher. Here, as Well as 

elsewhere in the speci?cation and claims, individual range 

values can be combined to form additional and/or non-dis 

closed ranges. 

As for the portion of the one or more kaolin compounds 

and/ or iron compounds that is not either “a kaolin compound” 

and/or “an iron compound,” such impurities should be non 

reactive in the environments present in conjunction With the 

present invention. Alternatively, if reactive, such impurities 

should either be easily captured, removed and/ or sequestered, 

or shouldnot add signi?cantly to any further contamination of 

any catalyst doWnstream. In still another embodiment, the 

amount of potassium-, sodium- and/or phosphorus-contain 

ing compound impurities in any of the one or more kaolin 

compounds and/or iron compounds that are utiliZed in con 

junction With the present invention should be less than about 

5 Weight percent, less than about 2.5 Weight percent, less than 

about 1 Weight percent, less than about 0.5 Weight percent, 

less than about 0.25 Weight percent, less than about 0.1 

Weight percent, or even less than about 0.01 Weight percent. 

Here, as Well as elseWhere in the speci?cation and claims, 

individual range values can be combined to form additional 

and/or non-disclosed ranges. In still yet another embodiment, 

the amount of potassium-, sodium- and/or phosphorus-con 

taining compound impurities in any of the one or more kaolin 

compounds and/or iron compounds that are utiliZed in con 

junction With the present invention should be Zero. That is, in 

this embodiment the one or more kaolin compounds and/or 

iron compounds that are utiliZed in conjunction With the 

present invention should be free from any potassium-, 

sodium- and/or phosphorus-containing compounds. 

While not Wishing to be bound to any one theory, it is 

believed that the present invention exploits various preferen 

tial reactions betWeen potassium, sodium and/or phospho 

rous compounds, or potassium-, sodium- and/ or phosphorus 

containing compounds, to sequester various potassium, 

sodium and/or phosphorous compounds, or potassium-, 
US 8,303,919 B2 

17 

sodium- and/or phosphorus-containing compounds that are 

detrimental to an increased active, or service, life of an SCR 

catalyst. Thus, the reactions discussed herein are to be con 

strued as non-limiting in that other additional reactions may 

be occurring in the combustion and/ or ?ue gas stream. 

While speci?c embodiments of the present invention have 

been shoWn and described in detail to illustrate the applica 

tion 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. 

What is claimed is: 

1. A method for increasing the active life of an SCR cata 

lyst, the method comprising the steps of: 

(a) providing at least one kaolin-bearing compound to a 

combustion Zone or ?ue gas stream of a fumace, or 

boiler, prior to entry of the ?ue gas into an SCR; and 

(b) permitting the at least one kaolin-bearing compound to 

react With any gaseous potassium and/or sodium com 

pounds, or potassium- and/or sodium-containing com 

pounds present in the combustion Zone or ?ue gas prior 

to the entry of the ?ue gas into the SCR. 

2. The method of claim 1, Wherein the kaolin-bearing com 

pound is selected from one or more kaolin-containing clays, 

kaolinite-containing clays, kaolinite, or mixtures of tWo or 

more thereof. 

3. The method of claim 1, Wherein the kaolin-bearing com 

pound is selected from kaolinite. 

4. The method of claim 1, Wherein the at least one kaolin 

bearing compound is provided to the combustion Zone via 

addition to pulverized coal, biomass, or a mixture thereof. 

5. The method of claim 1, Wherein the at least one kaolin 

bearing compound is provided to the combustion Zone via a 

dedicated supply line. 

6. The method of claim 1, Wherein the method further 

comprises the steps of: 

(c) providing at least one iron-bearing compound to a com 

bustion Zone or ?ue gas stream of a furnace, or boiler, 

prior to entry of the ?ue gas into an SCR; and 

(d) permitting the at least one iron-bearing compound to 

react With any gaseous phosphorus compounds, or phos 

phorus-containing compounds, present in the combus 

tion Zone or ?ue gas prior to the entry of the ?ue gas into 

the SCR. 

7. A method for increasing the active life of an SCR cata 

lyst, the method comprising the steps of: 

(i) providing at least one kaolin-bearing compound to a 

combustion Zone of a fumace or boiler; and 

(ii) permitting the at least one kaolin-bearing compound to 

react With any gaseous potassium and/or sodium com 

pounds, or potassium- and/or sodium-containing com 

pounds present in the combustion Zone prior to the entry 

of the ?ue gas into an SCR, 

Wherein the kaolin-bearing compound is selected from one 

or more kaolin-containing clays, kaolinite-containing 

clays, kaolinite, or mixtures of tWo or more thereof. 

8. The method of claim 7, Wherein the at least one kaolin 

bearing compound is provided to the combustion Zone via 

addition to pulverized coal, biomass, or a mixture thereof. 

9. The method of claim 7, Wherein the at least one kaolin 

bearing compound is provided to the combustion Zone via a 

dedicated supply line either in aqueous suspension or in a 

poWdered form. 

5 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

18 

10. The method of claim 7, Wherein the method further 

comprises the steps of: 

(iii) providing at least one iron-bearing compound to a 

combustion Zone of a fumace or boiler; and 

(iv) permitting the at least one iron-bearing compound to 

react With any gaseous phosphorus compounds, or phos 

phorus-containing compounds, present in the combus 

tion Zone prior to the entry of the ?ue gas into an SCR. 

11. A method for increasing the active life of an SCR 

0 catalyst While concurrently controlling mercury in a gas, the 

method comprising the steps of: 

(1) providing at least one kaolin-bearing compound to a 

combustion Zone or ?ue gas stream of a fumace, or 

boiler, prior to entry of the ?ue gas into an SCR; 

(ll) providing at least one iron-bearing halide compound to 

a combustion Zone or ?ue gas stream of a furnace, or 

boiler, prior to entry of the ?ue gas into an SCR; 

(Ill) permitting the kaolin portion of the at least one kaolin 

bearing compound to react With any gaseous potassium 

and/or sodium compounds, or potassium- and/or 

sodium-containing compounds present in the combus 

tion Zone or ?ue gas prior to the entry of the ?ue gas into 

the SCR; 

(IV) permitting the iron portion of the at least one iron 

bearing halide compound to react With any gaseous 

phosphorus compounds, or phosphorus-containing 

compounds present in the combustion Zone or ?ue gas 

prior to the entry of the ?ue gas into the SCR; and 

(V) permitting the halide portion of the at least one iron 

bearing halide compound to react With any gaseous mer 

cury compounds, or mercury-containing compounds, 

present in the combustion Zone or ?ue gas. 

12. The method of claim 11, Wherein the kaolin-bearing 

compound is selected from one or more kaolin-containing 

clays, kaolinite-containing clays, kaolinite, or mixtures of tWo or more thereof. 

13. The method of claim 11, Wherein the kaolin-bearing 

compound is selected from kaolinite. 

14. The method of claim 11, Wherein the iron-bearing 

halide compound is selected from iron (ll) bromide, iron (Ill) 

bromide, iron (ll) chloride, iron (Ill) chloride, iron (ll) iodide, 

iron (Ill) iodate, or mixtures of tWo or more thereof. 

15. The method of claim 11, Wherein the iron-bearing 

halide compound is iron (11) bromide. 

16. The method of claim 11, further comprising supplying 

one or more non-halogen-containing iron-bearing com 

pounds in combination With the at least one iron-bearing 

halide, Where the one or more non-halogen-containing iron 

bearing compounds are selected from iron (Ill) oxide, iron 

(11) carbonate, iron (ll) oxide, or mixtures of tWo or more 

thereof. 

17. The method of claim 11, further comprising supplying 

iron (ll) carbonate in combination With the at least one iron 

bearing halide. 

18. The method of claim 11, further comprising supplying 

iron (11) carbonate in combination With one or more of iron 

(11) bromide or iron (Ill) bromide. 

19. A method for sequestering one or more potassium 

and/or sodium compounds, or potassium- and/or sodium 

containing compounds, in the form of one or more less reac 

tive sodium aluminosilicate-containing, or potassium alumi 

nosilicate-containing, compounds, as Well as sequestering 

one or more phosphorus compounds, or phosphorus-contain 

ing compounds, in the form of one or more less reactive 

iron-phosphorus-containing compounds While concurrently 

sequestering mercury, the method comprising the steps of: 
US 8,303,919 B2 

19 

(1) providing at least one kaolin-bearing compound to a 

combustion Zone or ?ue gas stream of a fumace, or 

boiler; 

(2) providing at least one iron-bearing halide compound to 

a combustion Zone or ?ue gas stream of a furnace, or 5 

boiler; 

(3) permitting the kaolin portion of the at least one kaolin 

bearing compound to react With any gaseous potassium 

and/or sodium compounds, or potassium- and/or 

sodium-containing compounds present in the combus 

tion Zone or ?ue gas to form one or more less reactive 

sodium alumino silicate-containing, or potassium alumi 

nosilicate-containing, compounds; 

(4) permitting the iron portion of the at least one iron 

bearing halide compound to react With any gaseous 

phosphorus compounds, or phosphorus-containing 

compounds, present in the combustion Zone or ?ue gas 

to form one or more less reactive iron-phosphorus-con 

taining compounds; and 

(5) permitting the halide portion of the at least one iron 

bearing halide compound to react With any gaseous mer 

cury compounds, or mercury-containing compounds, 

present in the combustion Zone or ?ue gas. 

20. The method of claim 19, Wherein the kaolin-bearing 

compound is selected from one or more kaolin-containing 

10 

20 

20 

clays, kaolinite-containing clays, kaolinite, or mixtures of tWo or more thereof. 

21. The method of claim 19, Wherein the kaolin-bearing 

compound is selected from kaolinite. 

22. The method of claim 19, Wherein the iron-bearing 

halide compound is selected from iron (ll) bromide, iron (Ill) 

bromide, iron (ll) chloride, iron (Ill) chloride, iron (ll) iodide, 

iron (Ill) iodate, or mixtures of tWo or more thereof. 

23. The method of claim 19, Wherein the iron-bearing 

halide compound is one or more of iron (11) bromide or iron 

(Ill) bromide. 

24. The method of claim 19, further comprising supplying 

one or more non-halogen-containing iron-bearing com 

pounds in combination With the at least one iron-bearing 

halide, Where the one or more non-halogen-containing iron 

bearing compounds are selected from iron (Ill) oxide, iron 

(11) carbonate, iron (ll) oxide, or mixtures of tWo or more 

thereof. 

25. The method of claim 19, further comprising supplying 

iron (ll) carbonate in combination With the at least one iron 

bearing halide. 

26. The method of claim 19, further comprising supplying 

iron (11) carbonate in combination With one or more of iron 

(11) bromide or iron (Ill) bromide. 

* * * * *