WO2013082157A1

WO2013082157A1 - Multi-functional composition for rapid removal of mercury from a flue gas

Info

Publication number: WO2013082157A1
Application number: PCT/US2012/066861
Authority: WO
Inventors: Joseph M. Wong; Christopher VIZCAINO; Robert B. Huston; Frederick S. Cannon
Original assignee: Ada Carbon Solutions, Llc
Priority date: 2011-11-28
Filing date: 2012-11-28
Publication date: 2013-06-06
Also published as: CN103958030A; CN103958030B

Abstract

A multi-functional composition of matter that is useful for injection into a flue gas stream to remove mercury from the flue gas stream. The multi-functional composition of matter may include a sorbent such as powder activated carbon as well as other materials to enhance the oxidation reaction kinetics for the oxidation of mercury species as well as materials for enhancing the mass diffusion kinetics of the mercury species. The multi-functional composition of matter is particularly useful for the treatment of flue gas streams having a relatively high content of halogens such as chlorine.

Description

MULTI-FUNCTIONAL COMPOSITION FOR

RAPID REMOVAL OF MERCURY FROM A FLUE GAS

FIELD

[0001] This disclosure relates to the field of compositions for the rapid and efficient removal of mercury from a fluid stream such as a flue gas stream and to concrete- compatible byproducts incorporating the compositions.

BACKGROUND

[0002] Mercury (Hg) is a highly toxic compound and exposure at appreciable levels can lead to adverse health effects for people of all ages, including harm to the brain, heart, kidneys, lungs, and immune system. Mercury is naturally occurring but is also emitted from various human activities, such as burning fossil fuels and other industrial processes. For example, in the United States about 40% of the mercury introduced into the environment comes from coal-fired power plants.

[0003] In the United States and Canada, federal and state/provincial regulations have been implemented or are being considered to reduce mercury emissions, particularly from coal-fired power plants, steel mills, cement kilns, waste incinerators and boilers, industrial coal-fired boilers, and other coal combusting facilities. For example, the United States Environmental Protection Agency (U.S. EPA) has promulgated Mercury Air Toxics Standards (MATS), which would among other things require coal-fired power plants to capture approximately 90% of their mercury emissions beginning in about 2016.

[0004] The leading technology for mercury control from coal-fired power plants is activated carbon injection. Activated carbon injection involves the injection of sorbents, particularly powder activated carbon, into flue gas emitted by the boiler of a power plant. Powder activated carbon is a porous carbonaceous material having a high surface area, which exposes significant amounts of beneficial chemically functional and reaction sites and which creates high adsorptive potential for many compounds, including capturing mercury from the flue gas. Activated carbon injection technology has shown the potential to control mercury emissions in most coal-fired power plants, even those plants that may achieve some mercury control through control devices designed for other pollutants, such as wet or dry scrubbers used to control sulfur dioxide and acid gases.

[0005] In addition to mercury, the boiler's flue gas stream carriers a variety of compounds, including particulate matter such as fly ash. Equipment such as an electrostatic precipitator (ESP) or a fabric filter bag house is used to remove such particulate matter, and the fly ash may be sold by the power plant operator to a concrete manufacturer as a substitute for Portland cement. Such sales are highly advantageous to the power plant operator as they create an additional revenue stream and eliminate the need to landfill the fly ash.

SUMMARY

[0006] According to the present disclosure, the capture and removal of mercury from a boiler flue gas through activated carbon injection can be characterized by three primary steps, which may occur sequentially or simultaneously: (1 ) contact of the injected sorbent with the mercury species, which is typically present in very dilute concentrations in the flue gas {e.g., <100 parts per billion); (2) conversion of elemental mercury (i.e., Hg°), which is relatively inert and not easily adsorbed, into an oxidized mercury species {e.g., Hg⁺ and Hg⁺²), which is more readily adsorbable and is significantly more soluble in an aqueous solubilizing medium such as water; and (3) the diffusion of the oxidized mercury species into pores where it is held tightly {e.g., sequestered) without being released. The flue gas streams traverse the ductwork at very high velocities, such as in excess of 25 feet/second {e.g., in excess of 7.6 meters/second). Therefore, once injected, the sorbent must rapidly accomplish these three steps to contact, oxidize and sequester the mercury. In some instances, the sorbent only has a residence time of 1 to 2 seconds in the flue gas. Conventional powder activated carbons and other similar sorbent products do not efficiently accomplish the three required steps within such constraints. [0007] It would be advantageous to provide a novel composition of matter which overcomes the traditional limitations of conventional sorbents and can effectively act as a sorbent, catalyst, and solvent to efficiently and remove mercury from a flue gas stream, e.g., to meet governmental regulations for mercury emissions. In this regard, various embodiments of a composition of matter that is multi-functional are provided. These multi-functional compositions of matter overcome the limitations of conventional sorbents in that they can be injected into a flue gas stream to efficiently and rapidly remove mercury from the flue gas stream, e.g., to meet governmental regulations for mercury emissions.

[0008] In this regard, disclosed herein is a multi-functional composition of matter that is particularly useful for injection into a flue stream from a boiler {e.g., a coal burning and/or biomass burning boiler) to remove mercury therefrom. The multi-functional composition of matter may include minerals, an aqueous-based solubilizing medium (e.g., for solubilizing mercury species) and a sorbent (e.g., powder activated carbon) having a well-controlled pore structure. The multi-functional composition of matter may also have a relatively small median average particle size, such as not greater than about 15 μιτι. The multi-functionality of the composition, the adsorptive properties of the sorbent and the relatively small average particle size enable the composition to efficiently and rapidly capture mercury from a flue gas stream. The resulting admixture of fly ash that is extracted from the flue gas stream and the multi-functional composition of matter may be used as a substitute for cement in the manufacture of concrete, where the concrete foam stabilizes in a very short period of time during concrete manufacture.

[0009] In one exemplary embodiment, a multi-functional composition of matter is provided. The multi-functional composition of matter may include at least about 20 wt.% and not greater than about 50 wt.% minerals, at least about 20 wt.% fixed carbon and not greater than about 80 wt.% fixed carbon, and at least about 3 wt.% and not greater than about 15 wt.% of an aqueous-based solubilizing medium. The multi-functional composition of matter may have a small average particle size, such as a median average particle size of not greater than about 15 μιτι. In one aspect, the multi-functional composition of matter may include at least about 25 wt.% minerals. The minerals may include minerals selected from the group consisting of calcium-containing minerals, potassium-containing minerals, iron- containing minerals, silicon-containing minerals, silicate-containing minerals, sodium- containing minerals, tin-containing minerals, zinc-containing minerals, magnesium- containing minerals, aluminosilicate containing minerals and combinations thereof. In one aspect, the minerals comprise oxide minerals, and in one particular aspect the minerals comprise at least about 1 wt.% iron-containing minerals.

[0010] In another aspect, the multi-functional composition of matter may include not greater than about 12 wt.% aqueous-based solubilizing medium for solubilizing mercury species, such as not greater than about 10 wt.% aqueous-based solubilizing medium. The aqueous-based solubilizing medium may consist essentially of water, for example. In a further aspect, the multi-functional composition of matter includes little or no halogens {e.g., Br or CI) and in one embodiment the multi-functional composition of matter includes not greater than about 1 wt.% of a halogen.

[0011] In another aspect, the multi-functional composition of matter may have a median average particle size of at least about 8 μιτι and not greater than about 12 μιτι. In another aspect, the multi-functional composition of matter may have a Hardgrove Grindability Index of at least about 90, such as a Hardgrove Grindability Index (HGI) of at least about 100.

[0012] As is noted above, the multi-functional composition of matter may have well- controlled physical properties, such as particle density, average pore size and pore size distribution. In one aspect, the multi-functional composition of matter has a mercury particle density of at least about 0.5 g/cc and not greater than about 0.9 g/cc. In another aspect, the multi-functional composition of matter has an envelope particle density of at least about 0.5 g/cc and not greater than about 1 .0 g/cc.

[0013] Pore volume and pore size distribution may also be well-controlled. As used herein, pore volumes are expressed as the volume of pores in the carbon sorbent per gram of multi-functional composition. Thus, in one aspect, total pore volume of the carbon sorbent in the composition is at least about 0.25 cc/g. In another aspect, the mesoporosity volume of the activated carbon sorbent is at least about 0.1 cc/g. In yet a further aspect, the microporosity volume of the activated carbon sorbent is at least about 0.1 cc/g. For example, the mesoporosity volume of the activated carbon sorbent may be at least about 0.10 cc/g and not greater than about 0.15 cc/g while the microporosity volume of the activated carbon sorbent may be at least about 0.10 cc/g and not greater than about 0.15 cc/g.

[0014] The multi-functional composition of matter may be injected into a flue gas stream to efficiently remove mercury from the flue gas stream to meet governmental regulations, while not having a significant detrimental impact on the ability of the admixtures of fly ash and the multi-functional composition removed from the flue gas stream to be sold as a cement substitute. In this regard, the multi-functional composition of matter advantageously may adsorb not greater than about 1 mg of air entrainment agent per 1 g of multi-functional composition, e.g., during the manufacture of concrete using the admixture recovered from the flue gas stream as a cement substitute. In another aspect, the multi-functional composition of matter is adapted to be blended with a cementitious composition including an air entrainment agent and water, wherein the foam stability time of the blend is not greater than about 45 minutes, such as not greater than about 30 minutes. As used herein, the foam stability time is the amount of time until an initially stabilized foam requires no more air entrainment agent to remain stabilized.

[0015] Also disclosed herein is a method for the treatment of a flue gas stream to remove mercury therefrom, comprising the step of contacting the flue gas stream with the multi-functional composition of matter in accordance with the embodiments and aspects disclosed herein. In one aspect, a method for the treatment of a flue gas stream to remove mercury therefrom includes contacting the flue gas stream with the multi-functional composition of matter for not greater than about five seconds, such as not greater than about one second. The flue gas stream may include a halogen {e.g., CI and/or Br) that is formed in-situ during combustion of a combustion feed in a boiler and/or that is injected into the flue gas stream, e.g., upstream of the multi-functional composition of matter. The multi-functional composition of matter may advantageously be separated from the flue gas stream with the fly ash in an electrostatic precipitator (ESP) or a fabric filter bag house.

DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 illustrates a schematic view of a multi-functional composition of matter.

[0017] FIG. 2 illustrates a flow sheet for the manufacture of a multi-component composition of matter.

[0018] FIG. 3 illustrates a plant configuration and method for the capture and sequestration of mercury from a flue gas stream.

DETAILED DESCRIPTION

[0019] Various embodiments of a multi-functional composition of matter are provided that are particularly useful when injected into a fluid gas stream such as a flue gas stream {e.g., from a coal-burning boiler or a waste energy boiler) to rapidly and efficiently capture and remove mercury from the flue gas stream. In this regard, the multi-functional composition of matter advantageously includes several different components that synergistically may (1 ) increase the probability of contact with mercury species in the flue gas, (2) decrease the time required for mercury oxidation and capture {e.g., as a result of enhanced oxidation reaction kinetics and/or mass diffusional kinetics), and (3) advantageously reduce the total amount of material that must be injected to recover sufficient amounts of mercury to meet mercury removal criteria, such as applicable government regulations. Further, when the multi-functional composition of matter is removed from the flue gas stream after mercury capture {e.g., in an electrostatic precipitator or fabric filter baghouse) along with fly ash from the boiler, the multi-functional composition of matter may be used with the fly ash as an acceptable substitute for cement in the manufacture of concrete or similar cementitious products.

[0020] In this regard, the composition of matter is a multi-functional composition of matter. That is, the composition of matter advantageously includes several different components that synergistically may decrease the time required for mercury oxidation and capture from the flue gas stream (e.g., enhance oxidation reaction kinetics and/or mass diffusional kinetics) and may advantageously reduce the total amount of sorbent {e.g., powder activated carbon sorbent) that must be injected into the flue gas stream to recover sufficient amounts of mercury to meet applicable government regulations.

[0021] In this regard, the multi-functional composition of matter may include minerals that enhance {e.g., catalyze) the oxidation of elemental mercury by an oxidizing agent {e.g., an oxidizing agent contained in the flue gas stream), an aqueous- based solubilizing medium such as water to solubilize oxidized mercury and enhance mass diffusional kinetics, and a sorbent such as powder activated carbon having a well- controlled pore size and pore size distribution to provide a large surface area on which both kinetic mechanisms occur and to provide sufficient microporosity to sequester the oxidized mercury. The multi-functional composition of matter may also have a relatively small median average particle size, i.e., as compared to typical sorbent compositions used for injection into a flue gas stream.

[0022] Thus, one component of the multi-functional composition of matter includes minerals. The minerals may advantageously catalyze the oxidation of the elemental mercury in the flue gas stream. The presence of such minerals may thereby enhance the kinetics of the mercury oxidation such that a reduced contact time with the flue gas stream is required to oxidize and remove sufficient amounts of mercury from the flue gas stream.

[0023] The minerals may advantageously be comprised of minerals including, but not limited to, aluminum-containing minerals, calcium-containing minerals, iron- containing minerals, silicon-containing minerals, silicate-containing minerals, sodium- containing minerals, potassium-containing minerals, zinc-containing minerals, tin- containing minerals, magnesium-containing minerals, and combinations thereof. The minerals may predominantly be oxide-based minerals, such as metal oxide minerals {e.g., CaO, Fe₂O₃, Fe3O₄, FeO, AI2O3), and silicates {e.g. AI₂SiO₅). In one characterization, the minerals predominantly include metal oxides, particularly aluminum oxides and iron oxides. In another characterization, the minerals include calcium- containing minerals, iron-containing minerals and aluminosilicates. These types of minerals are particularly well adapted to catalyze the oxidation reaction of the mercury. Iron-containing minerals are particularly well adapted to catalyze the oxidation reaction, and in one characterization, the minerals include at least 1 wt.% iron-containing minerals. The minerals are intimately intertwined within the multi-functional composition of matter within a well controlled porous structure that facilitates the oxidation, capture and removal of mercury. To provide sufficient reaction activity and rapid oxidation kinetics, the multi-functional composition of matter may include at least about 20 weight percent of the minerals, such as at least 25 weight percent and even at least about 30 weight percent of the minerals. However, excessive amounts of the minerals in the multi-functional composition of matter may be detrimental to the capture of mercury. In this regard, the multi-functional composition of matter may include not greater than about 50 weight percent of the minerals, such as not greater than about 45 weight percent. Advantageously, the multi-functional composition of matter may include not greater than about 40 weight percent of the minerals, such as not greater than about 35 weight percent of the minerals. The total mineral content may be measured by a TGA701 Thermalgravitmetric Analyzer (LECO Corporation, St. Joseph, Ml). The specific types and amount of particular minerals may be measured by the Niton XL3t X- Ray Fluorescence (XRF) Analyzer (Thermo Fisher Scientific Inc., Waltham, MA).

[0024] In addition, the multi-functional composition of matter may also include an amount of aqueous-based solubilizing medium such as water. The presence of a minimum level of solubilizing medium may advantageously enhance the mass diffusional kinetics of the mercury oxidation and sequestration by solubilizing oxidized mercury species on the sorbent surface, e.g., within the mespores and micropores. In this regard, the multi-functional composition of matter may include at least about 2 weight percent of the solubilizing medium, such as at least about 3 weight percent or at least about 6 weight percent. However, the amount of solubilizing medium in the multifunctional composition of matter should be not greater than about 15 weight percent, such as not greater than about 12 weight percent, or even not greater than about 10 weight percent to avoid interfering with the mercury oxidation reaction(s).

[0025] The multi-functional composition of matter also includes a sorbent that is adapted to provide a large surface area for the mercury oxidation and to sequester the oxidized mercury from the flue gas stream. In one aspect, the sorbent may include fixed carbon such as a porous carbonaceous material (e.g., powder activated carbon) having a high surface area and well-controlled pore structure.

[0026] The multi-functional composition may include at least about 10 weight percent of the fixed carbon, such as at least about 15 weight percent or even at least about 20 weight percent fixed carbon. However, it is preferred that the fixed carbon of the multifunctional composition not exceed about 80 weight percent, such as not greater than about 6 weight percent, or even not greater than about 55 weight percent. Due to a well-controlled pore structure and the presence of the other components in the multifunctional composition, a relatively low amount of fixed carbon [e.g., activated carbon) is required for mercury oxidation and sequestration, e.g., a low amount of activated carbon per unit volume of the flue gas stream as compared to typical sorbent compositions.

[0027] To further enhance the oxidation reaction kinetics and mass diffusional kinetics, the multi-functional composition of matter may have a relatively small average particle size {e.g., median average particle size, also known in the art as d₅o) particularly as compared to typical sorbent compositions used for activated carbon injection. In this regard, the multi-functional composition of matter may have a median average particle size of not greater than about 18 μιτι, such as not greater than about 15 μιτι, and even not greater than about 12 μιτι. In another aspect, the multi-functional composition matter may have a median average particle size of at least about 5 μιτι, such as at least about 6 μιτι or even about 8 μιτι. The median average particle size may be measured using techniques such as light scattering techniques {e.g., using a Saturn DigiSizer, available from Micromeritics Instrument Corporation, Norcross, GA). A relatively small median particle size, such as not greater than about 15 μιτι, means greater surface area per volume of the multi-functional composition of matter. The increased surface area results in many benefits, including, but not limited to, increased exposure of the mercury to minerals, increased area available for reactions to occur, and thus overall improved reaction kinetics.

[0028] The multi-functional composition of matter may also be characterized by having a well-controlled particle density. Controlling the particle density correlates to control over the surface area and total pore volume of the composition of matter, which in turn affect mercury capture performance. Two methods of measuring particle density are described below.

[0029] Particle density may be measured by liquid mercury volume displacement, in which case the result is referred to as the mercury particle density. In this regard, the multi-functional composition of matter may have a mercury particle density of at least about 0.5 g/cc, such as at least about 0.6 g/cc. Conversely, the mercury particle density of the multi-functional composition of matter may be not greater than about 0.9 g/cc, such as not greater than about 0.8 g/cc. Mercury particle density may be measured by the Micromeritics AccuPyc Pycnometer (Micromeritics Inc., Norcross, GA, USA).

[0030] Particle density may also be measured by sedimentary volume displacement, in which case the result is referred to as the envelope particle density. In this regard, the envelope particle density of the multi-functional composition of matter may be at least about 0.5 g/cc, such as at least about 0.6 g/cc or at least about 0.7 g/cc. The envelope particle density of the multi-functional composition of matter may be not greater than about 1 .0 g/cc, such as not greater than about 0.9 g/cc, or even not greater than about 0.8 g/cc. Envelope particle density may be measured using a Micromeritics GeoPyc Envelope Density Analyzer (Micrometrics, Inc., Norcross, GA, USA).

[0031] The multi-functional composition of matter also may have a high pore volume and a well-controlled distribution of the pores, particularly among the mesopores (i.e., from 20 A to 500 A width) and the micropores (i.e. , not greater than 20 A width). It has been found that a well-controlled distribution of micropores and mesopores are desirable for effective removal of mercury from the flue gas stream. In this regard, while not wishing to be bound by any theory, it is believed that the mesopores are the predominate structures for capture and transport of the oxidized mercury species to the micropores, whereas micropores are the predominate structures for sequestration of the oxidized mercury species.

[0032] In this regard, the sum of micropore volume plus mesopore volume (e.g., the total pore volume) of the multi-functional composition of matter may be at least about 0.10 cc/g, such as at least 0.20 cc/g, and at least about 0.25 cc/g or even at least about 0.30 cc/g. The micropore volume of the multi-functional composition of matter may be at least about 0.10 cc/g, such as at least about 0.15 cc/g. Further, the mesopore volume of the multi-functional composition of matter may be at least about 0.10 cc/g, such as at least about 0.15 cc/g. In one characterization, the ratio of micropore volume to mesopore volume may be at least about 0.7, such as at least about 0.9, and may be not greater than about 1 .5. Such levels of micropore volume relative to mesopore volume advantageously enable efficient capture and sequestration of oxidized mercury species, such as HgC or HgBr₂, by the multi-functional composition of matter. Pore volumes may be measured using gas adsorption techniques (e.g., N₂ adsorption) using instruments such as a TriStar II Surface Area Analyzer (Micromeritics Instruments Corporation, Norcross, GA, USA).

[0033] While not wishing to be bound by any particular theory, FIG. 1 schematically illustrates the mechanisms that are believed to be responsible for the rapid oxidation and sequestration of mercury from a flue gas stream using the multi-functional compositions of matter disclosed herein. The fixed carbon 102 provides a large surface area for the elemental mercury 110 to react with the minerals 106 and other components of the multi-functional composition of matter 100 in the presence of a halogen 108 such as CI^". The minerals 106 that are in close proximity with other redox agents on or near the surface advantageously catalyze, oxidize, enhance, and/or otherwise facilitate the oxidation of the mercury and the formation of oxidized mercury species 112 such as Hg⁺², which can bond with the halogen to form such species 114, for example HgCI₂. The presence of aqueous-based solubilizing medium on the multifunctional composition of matter [e.g., water 116) facilitates the redox activity, the transport of these mercury species 114 within the pore structure 104, and the solubilization of these mercury species 114 within the pores 104 to sequester the mercury species 114 therein. As a result, the mercury oxidation kinetics and the mass diffusional kinetics are enhanced to enable the rapid and efficient oxidation and sequestration of mercury by the multi-functional composition of matter 100.

[0034] Thus, the fixed carbon 102 provides a large surface area for the elemental mercury to react with halogen [e.g., CI^"). The halogen may be provided in the flue gas stream in-situ, such as when the combustion feed being fed to the boiler includes chlorine species. Examples of such combustion feeds include bituminous coals (e.g., coals from the Eastern regions of the United States) and combustion feeds that include biomass, in whole or in part. A halogen may also be added to the flue gas stream ex- situ, such as when a halogen-containing compound {e.g., a bromide salt solution) is injected into the flue gas stream upstream or near the injection point of the multifunctional composition. The multi-functional composition of matter may also include a small amount of a halogen {e.g., a halogen salt or other halogen moiety), such as not greater than about 1 wt.%.

[0035] In any event, the oxidation reaction(s) are catalyzed by minerals, which are in close proximity with the oxidizing agents on or near the surface of the carbon particles. These minerals advantageously catalyze the oxidation of the mercury and the formation of oxidized mercury species such as one or more mercury halide species. The presence of water (H₂O) facilitates the transport of these mercury species and the solubilization of these mercury species within the pores {e.g., micropores) to sequester the mercury species therein. As a result, the mercury oxidation kinetics and the mass diffusional kinetics are enhanced to enable the rapid oxidation and sequestration of mercury by the activated carbon.

[0036] FIG. 2 is a flow sheet that illustrates an exemplary method for the manufacture of a multi-functional composition of matter in accordance with one embodiment. The manufacturing process begins with a carbonaceous feedstock 201 such as low-rank lignite coal with a relatively high content of natural deposits of native minerals. In the manufacturing process, the feedstock is subjected to an elevated temperature and one or more oxidizing gases under exothermic conditions for a period of time to sufficiently increase surface area, create porosity, alter surface chemistry, and expose and exfoliate native minerals previously contained within feedstock. The specific steps in the process include: (1 ) dehydration 202, where the feedstock is heated to remove the free and bound water, typically occurring at temperatures ranging from 100°C to 150°C; (2) devolatilization 203, where free and weakly bound volatile organic constituents are removed, typically occurring at temperatures above 150°C; (3) carbonization 204, where non-carbon elements continue to be removed and elemental carbon is concentrated and transformed into random amorphous structures, typically occurring at temperatures of from about 350°C to about 800°C; and (4) activation 205, where steam, air or other oxidizing agent(s) is added and pores are developed, typically occurring at temperatures above 800°C. The manufacturing process may be carried out, for example, in a multi-hearth or rotary furnace. The manufacturing process is not discrete and steps can overlap and use various temperatures, gases and residence times within the ranges of each step to promote desired surface chemistry and physical characteristics of the manufactured product.

[0037] After activation 205, the product may be subjected to a comminution step 206 to reduce the particle size (e.g., reduce the median particle size) of the activated product. Comminution 206 may occur, for example, in a mill such as a roll mill, jet mill or other like process. Comminution 206 may be carried out for a time sufficient to reduce the median particle size of the thermally treated product to not greater than about 15 μιτι, such as not greater than about 12 μιτι.

[0038] Advantageously, the multi-functional composition of matter may have a relatively high Hardgrove Grindability Index (HGI), as measured by ASTM Method D409. The HGI was developed to empirically measure the relative difficulty of grinding coal to the particle size necessary for complete combustion in a coal boiler furnace. The use of HGI has been extended to grinding coal for other purposes such as iron-making, cement manufacture and chemical industries utilizing coal. Particulate materials of low value HGI are more difficult to grind than those with high values. Mill capacity also falls when grinding materials with a lower HGI. In this regard, the HGI of the multi-functional composition of matter may be at least about 80 such as at least about 90, at least about 100 or even at least about 1 10. The relatively high HGI enables the average particle size to be reduced with relatively low energy consumption. Further, the relatively soft materials of the multi-functional composition of matter will lead to reduced erosion {e.g., attrition) of the comminuting equipment as compared to harder materials having a low HGI. While not wishing to be bound by any theory, it has been observed that utilizing lignite matter feedstock will lead to a relatively high HGI.

[0039] In another embodiment, a method for the treatment of the flue gas stream to remove mercury therefrom is provided that includes the step of contacting the flue gas stream with the multi-functional composition of matter described herein. The flue gas stream 301 exits a boiler 302 where coal has been combusted. As illustrated in FIG. 3, the flue gas stream 301 may then proceed to an air heater unit 304 where the temperature of the flue gas stream 301 is reduced. Thereafter, the flue gas stream 301 may be introduced to a separation unit 307 such as an electrostatic precipitator (ESP) or a fabric filter bag house which removes particulate matter from the flue gas, before exiting out a stack 308. For example, a cold-side (i.e., after the air heater unit) electrostatic precipitator can be used. It will be appreciated by those skilled in the art that the plant may include other devices not illustrated in FIG. 3, such as a selective catalytic reduction unit (SCR) and the like, and may have numerous other configurations. In order to capture mercury from the flue gas, the multi-functional composition of matter may be introduced to (e.g., injected into) the flue gas stream 301 either before 303A or after 303B the air heater unit 304, but before the separation unit 307 which will remove it from the flue gas.

[0040] The nature of the multi-functional composition of matter may advantageously enable a diminished amount of the multi-functional composition of matter to be injected into the flue gas stream to obtain high mercury removal rates as compared to typical sorbent compositions. The amount of multi-functional composition of matter required to remove mercury from the flue gas stream will vary depending upon the composition of the coal and process emission control steps. Therefore, it is advantageous to define a percent removal of mercury from the coal or fuel burned in the boiler, as percent removed in pounds of mercury per trillion BTU of fuel calorimetric heating value (lb Hg/Tbtu) from coal as measured at the plant stack 308 in accordance with US EPA MATS methodologies. The ability to capture high levels of mercury while injecting less sorbent material may advantageously reduce material cost to the power plant operator.

[0041] While the separation unit 307 may be selected from a number of devices, including an ESP or a fabric filter bag house, the multi-functional composition of matter disclosed herein is particularly useful for removing mercury from the flue gas stream 301 when an ESP is utilized as the separation unit 307. For example, the separation unit 307 can be a cold-side ESP. While ESP units generally have a lower capital cost than a fabric filter bag house unit, fabric filter bag house units are often utilized to increase the contact time between the sorbent composition and the flue gas stream because the unit traps the sorbent and the flue gas continues to pass through the sorbent on the filter until the filter is rapped to remove the sorbent and other trapped materials. Such resident times are often deemed necessary to adequately capture mercury from the flue gas stream with temperatures of less than about 177°C. However, utilizing the multi-functional composition of matter disclosed herein, which provides rapid kinetics for the oxidation reaction and mass diffusion of mercury species, even very short residence times {e.g., the contact times) between the flue gas stream and the multi-functional composition of matter may be sufficient to remove at least about 85% of the mercury from the flue gas stream, such as at least about 90% of the mercury. In this regard, the residence time may be not greater than about 5 seconds, such as not greater than about 3 seconds or even not greater than about 1 second while achieving such removal rates.

[0042] As stated previously, the separation unit 307 separates the multi-functional composition of matter from the flue gas stream, along with fly ash that is produced by combustion of coal in the boiler. This admixture 306 may be advantageously used in the manufacture of a cementitious material such as concrete by blending the admixture 306 with a cementitious composition including an air entrainment agent. In this regard, while not wishing to be bound by any theory, it is believed that due to the relatively small amount of fixed carbon in the multi-functional composition of matter, the multi-functional composition of matter adsorbs a diminished amount of air entrainment agent as compared to typical sorbent compositions. Thus, the multi-functional composition of matter recovered with fly ash may be blended with cementitious compositions to produce higher quality cement as compared to typical sorbent compositions.

[0043] Specifically, during the manufacture of concrete, air entrainment agents {e.g., surfactants) are added to the mixture to entrain air into the concrete to form stable foam, which is necessary for concrete strength. Upon the introduction of the air entrainment agent, concrete manufacturers prefer that the foam stabilize over a relatively short period of time e.g., within less than about 30 minutes. This short-time frame is particularly important for use in ready-mix concrete. However, most fly ash mixtures that contain conventional sorbents require both a high concentration of air entrainment agent due to the sorbent competing for the agent, and also result in the foam destabilizing over time.

[0044] In this regard, it is a particular advantage that the multi-functional composition of matter may adsorb not greater than 800 parts of air entrainment agent per million parts of multi-functional composition of matter such as not greater than 750 parts of air entrainment agent per million parts of multi-functional composition of matter by weight. Because the multi-functional composition of matter adsorbs a relatively low amount of air entrainment agent, more air entrainment agent is available to entrain air in the concrete mixture and the foam stabilization time is reduced to not greater than 30 minutes, such as not greater than 10 minutes. Further, due to the synergistic effect of the multi-functional composition of matter, a reduced amount of activated carbon may be injected into the flue gas stream to remove mercury as compared to typical sorbent compositions, resulting in a reduced amount of fixed carbon that is extracted with the admixture 306 from the separation device 307.

[0045] The combustion feed that is combusted in the boiler 302 may include a relatively high chlorine content, such as at least about 250 ppm CI, at least about 500 ppm CI, or even at least about 750 ppm CI. Examples of such a combustion feed may include, but are not limited to, bituminous coals and biomass feeds. High chlorine combustion feeds may advantageously form an oxidizing agent {e.g., CI) in-situ within the flue gas stream. Alternatively, or in addition to, an oxidizing agent {e.g., a bromide salt solution) may be injected ex-situ into the flue gas stream, such as upstream of the injection of the multi-functional composition of matter.

[0046] While various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.

Claims

What is Claimed is:

1 . A multi-functional composition of matter, the composition of matter comprising at least about 20 wt.% and not greater than about 50 wt.% minerals, at least about 20 wt.% and not greater than about 80 wt.% fixed carbon, and at least about 3 wt.% and not greater than about 15 wt.% of an aqueous-based solubilizing medium, wherein the multi-functional composition of matter has a median average particle size of not greater than about 15 μιτι.

2. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter comprises at least about 25 wt.% minerals.

3. The multi-functional composition of matter recited in Claim 1 , wherein the minerals comprise minerals selected from the group consisting of calcium-containing minerals, potassium-containing minerals, iron-containing minerals, silicon-containing minerals, silicate-containing minerals, sodium-containing minerals, tin-containing minerals, zinc-containing minerals, magnesium-containing minerals, aluminosilicate containing minerals and combinations thereof.

4. The multi-functional composition of matter recited in Claim 1 , wherein the minerals comprise oxide minerals.

5. The multi-functional composition of matter recited in Claim 1 , wherein the minerals comprise at least about 1 wt.% iron-containing minerals.

6. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter comprises not greater than about 1 wt.% of a halogen.

7. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter comprises not greater than about 12 wt.% aqueous-based solubilizing medium.

8. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter comprises not greater than about 10 wt.% aqueous-based solubilizing medium.

9. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter has a median average particle size of at least about 8 μιτι and not greater than about 12 μιτι.

10. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter has a Hardgrove Grindability Index of at least about 90.

1 1 . The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter has a Hardgrove Grindability Index of at least about 100.

12. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter has a mercury particle density of at least about 0.5 g/cc and not greater than about 0.9 g/cc.

13. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter has an envelope particle density of at least about 0.5 g/cc and not greater than about 1 .0 g/cc.

14. The multi-functional composition of matter recited in Claim 1 , wherein the total pore volume of the activated carbon sorbent is at least about 0.25 cc/g.

15. The multi-functional composition of matter recited in Claim 1 , wherein the mesoporosity volume of the activated carbon sorbent is at least about 0.1 cc/g.

16. The multi-functional composition of matter recited in Claim 1 , wherein the microporosity volume of the activated carbon sorbent is at least about 0.1 cc/g.

17. The multi-functional composition of matter recited in Claim 1 , wherein the mesoporosity volume of the activated carbon sorbent is at least about 0.10 cc/g and not greater than about 0.15 cc/g and the microporosity volume of the activated carbon sorbent is at least about 0.10 cc/g and not greater than about 0.15 cc/g.

18. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter adsorbs not greater than about 1 mg of air entrainment agent per 1 g of the multi-functional composition.

19. The multi-functional composition of matter recited in Claim 1 , wherein the multi-functional composition of matter is adapted to be blended with a cementitious composition including an air entrainment agent and water, wherein the foam stability time of the blend is not greater than about 30 minutes.

20. A method for the treatment of a flue gas stream to remove mercury therefrom, comprising the step of contacting the flue gas stream with the multi-functional composition of matter recited in any of the preceding claims.

21 . The method recited in Claim 20, comprising the step of contacting the flue gas stream with the multi-functional composition of matter for not greater than about five seconds.

22. The method recited in Claim 20, comprising the step of contacting the flue gas stream with the multi-functional composition of matter for not greater than about one second.

23. The method recited in Claim 20, wherein the flue gas stream comprises a halogen.

24. The method recited in Claim 20, wherein the flue gas stream comprises at least about 250 parts per million chlorine.

25. The method recited in Claim 23, wherein the halogen is formed in-situ during the combustion of a feed in a boiler.

26. The method recited in Claim 23, wherein at least a portion of the halogen is injected into the flue gas stream after the flue gas stream exits a boiler.

27. The method recited in Claim 20, wherein the multi-functional composition of matter is separated from the flue gas stream in an electrostatic precipitator or a fabric filter bag house.