Patent Publication Number: US-2010113267-A1

Title: System and method for coproduction of activated carbon and steam/electricity

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of PCT application PCT/US2008/063743, filed on May 15, 2008, which itself claims priority of application 60/938,592 filed on May 17, 2007 and application Ser. No. 12/120,639 filed on May 14, 2008. The disclosures of these three prior applications are incorporated herein by reference, and priority is claimed. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Contract Numbers DE-FC26-98FT40320 and DE-FC26-98FT40321 awarded by the United States Department of Energy. The government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the generation of steam/electricity from a carbonaceous material and the production of activated carbon. Appropriate combination of these two processes provides significant cost savings through requiring fewer pieces of equipment, reducing operating costs, and increasing efficiency between the two processes. A portion of coal processed for a steam/electricity generation plant is diverted to a carbon activation plant thereby reducing equipment costs. A portion of steam produced in the steam/electricity generation plant is directed to the activated carbon plant for steam activation of a carbonized product. A portion of the combustible gases resulting from the carbonization and activation steps of the activated carbon plant is directed back to the steam/electricity plant, e.g. for reburn, and a portion may be recycled for use in the carbonization and/or activation steps. Activated carbon product resulting from the activated carbon production plant may be used, for example, to reduce heavy metal (e.g. mercury) emissions and/or to control NO x  emissions in power plant flue gas, for example, coal-fired power plant flue gas, by contacting the NO x -containing flue gas with activated carbon thereby converting NO to N 2 . 
     2. Background of the Invention 
     Carbon-based sorbents, including activated carbon, are currently used for controlling vapor-phase mercury emissions in coal-fired power plant flue gases. In a typical application, carbon sorbents are injected into the flue gas duct upstream of a particulate removal device such as a fabric filter or an electrostatic precipitator. The activated carbon used for such injection is typically manufactured off-site from carbonaceous materials like coal or coconut shells. 
     In existing stand-alone activated carbon production plants, an associated boiler generates steam for activating a carbonized material. The typical activated carbon plant generates, from both carbonization and activation steps, product gases which may comprise, for example, hydrocarbons, carbon monoxide, hydrogen, ammonia, hydrogen cyanide, hydrogen sulfide, and combinations thereof. Heat generated from combustion of these gases may be used to make steam in the on-site boiler. The steam may then be directed back to the carbonization and/or activation steps. Depending on regulatory requirements, the resultant flue gas from the boiler must be cleaned to varying degrees before discharge into the atmosphere via a stack. 
     The current use of separate systems for activated carbon production and energy production is not optimal, requires separate energy production for the operation of duplicate processes, and produces significant pollution as a result of the energy production. 
     Accordingly, there is an ongoing need for a system and method for the coproduction of activated carbon and steam/electricity. 
     SUMMARY OF THE INVENTION 
     Herein disclosed is a method of producing activated carbon comprising carbonizing a solid carbonaceous material to yield a carbonized product and carbonization product gases; activating the carbonized product via activation with steam to yield activated carbon and activation product gases; and utilizing process gas comprising at least a portion of the carbonization product gases or a combustion product thereof; at least a portion of the activation product gases or a combustion product thereof; or a combination thereof, in a solid fuel boiler system that burns a solid fuel boiler feed, wherein the boiler system comprises a boiler upstream of an air heater within a steam/electricity generation plant, said boiler comprising a combustion zone. 
     In embodiments, the method further comprises burning at least a portion of the activation product gases, at least a portion of the carbonization product gases, or a combination thereof in a gas furnace to yield furnace combustion gas and introducing at least a portion of the furnace combustion gas into the solid fuel boiler system. In embodiments, at least a portion of the furnace combustion gas is introduced into the solid fuel boiler system upstream of the air heater. The furnace combustion gas may be introduced downstream of the combustion zone and upstream of the air heater. In embodiments, at least a portion of the furnace combustion gas is introduced into the solid fuel boiler system upstream of a pollution control device. In embodiments, at least a portion of the furnace combustion gas is introduced into the solid fuel boiler system downstream of the air heater and upstream of a pollution control device. The furnace combustion gas may be introduced to a convective pass section of the boiler. In embodiments wherein the process gas is burned in a gas furnace to yield furnace combustion gas, the process gas may comprise at least a portion of the carbonization product gas. 
     In some embodiments, the heat input of the at least a portion of the furnace combustion gas introduced into the solid fuel boiler system is greater than about 0.1% and less than about 5% of the total heat input of the steam/electricity generation plant. In some embodiments, the heat input of the at least a portion of the furnace combustion gas introduced into the solid fuel boiler system is greater than 1% and less than about 5% of the total heat input of the steam/electricity generation plant. In embodiments, the at least a portion of the furnace combustion gas introduced into the solid fuel boiler system is greater than about 0.1% and less than about 5% of the total flue gas flowing through the steam/electricity generation plant. In embodiments, the at least a portion of the furnace combustion gas introduced into the solid fuel boiler system is greater than 1% and less than about 5% of the total flue gas flowing through the steam/electricity generation plant. In some embodiments, the heat input of the at least a portion of the furnace combustion gas introduced into the solid fuel boiler system is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5% to 1% or may be greater than 1%. 
     In embodiments, the process gas is introduced into the combustion zone of the solid fuel boiler. In embodiments, the amount of combustion gas produced from combustion of the process gas is greater than about 0.1% and less than about 5% of the total flue gas flowing through the steam/electricity generation plant. In embodiments, the amount of combustion gas produced from combustion of the process gas is greater than 1% and less than about 5% of the total flue gas flowing through the steam/electricity generation plant. In embodiments, the amount of combustion gas produced from combustion of the process gas is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5% from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5% to 1% or may be greater than 1%. 
     The process gas is sometimes used as a reburn fuel (secondary combustion) to reduce NO x  production from the solid fuel boiler. In embodiments wherein the process gas is used as a reburn fuel, the process gas may comprise at least a portion of the activation product gas. In some embodiments wherein the process gas is used as reburn fuel, the heat input of the process gas used as reburn fuel is greater than about 0.1% and less than about 5% of the total heat input of the steam/electricity generation plant. In some embodiments wherein the process gas is used as reburn fuel, the heat input of the process gas used as reburn fuel is greater than about 1% and less than about 5% of the total heat input of the steam/electricity generation plant. In some embodiments wherein the process gas is used as reburn fuel, the heat input of the process gas used as reburn fuel is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5% to 1%, or may be greater than 1%. 
     In embodiments, the method further comprises diverting a portion of the solid fuel from the steam/electricity generation plant for use as solid carbonaceous material. In embodiments, the portion of the solid fuel diverted from the steam/electricity generation plant is greater than about 0.1% and less than about 5% of the solid fuel boiler feed. In embodiments, the portion of the solid fuel diverted from the steam/electricity generation plant is greater than about 0.3% and less than about 5% of the solid fuel boiler feed. In embodiments, the portion of the solid fuel diverted from the steam/electricity generation plant is greater than about 1% and less than about 5% of the solid fuel boiler feed. In embodiments, the portion of the solid fuel diverted from the steam/electricity generation plant is in the range of from 0.1% to 5%, from 0.3% to 5%, 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5% to 1%, or may be greater than 1%. 
     In specific embodiments of the disclosed method, the solid carbonaceous material comprises coal. In embodiments, the solid carbonaceous material further comprises biomass. In some embodiments, the solid carbonaceous material comprises coal, biomass, or a combination thereof, the solid fuel boiler feed comprises coal, biomass, or a combination thereof, and the portion of the solid fuel diverted from the steam/electricity generation plant for use as solid carbonaceous material is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5 to 1%, or may be greater than 1%. 
     In some embodiments, the solid carbonaceous material is coal and/or biomass, the solid fuel boiler feed comprises coal and/or biomass, and the portion of the solid fuel diverted from the steam/electricity generation plant for use as solid carbonaceous material comprises greater than 1% and less than about 5% of the solid fuel boiler feed, alternatively, greater than 0.3% and less than 5%. In some embodiments, the solid carbonaceous material is coal and/or biomass, the solid fuel boiler feed comprises coal and/or biomass, and the portion of the solid fuel diverted from the steam/electricity generation plant for use as solid carbonaceous material is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5 to 1%, or may be greater than 1%. 
     In embodiments, the solid carbonaceous material comprises lignite. The lignite may have a base to acid ratio greater than or equal to about 0.4 and an ash content of less than or equal to about 15%. 
     Steam for the activation of the carbonized product may be diverted from the steam produced in the steam/electricity generation plant. The diverted steam stream may comprise less than about 5% of the steam generated in the steam/electricity generation plant. Alternatively, the diverted steam stream may comprise greater than 0.1% and less than about 5%; greater than 0.3% and less than about 5%; greater than 0.5% and less than about 5%, greater than 1% and less than about 5%; greater than 0.1% and less than 2%; greater than 0.3% and less than 2%, greater than 0.5% and less than 2%, or greater than 1% and less than 2% of the steam generated in the steam/electricity generation plant. 
     The steam/electricity generation plant may further comprise pollution control equipment and the pollution control equipment of the steam/electricity generation plant may be used to remove pollutants from the process gas. A portion of the activated carbon produced via the disclosed method may be injected into a flue gas of the steam/electricity generation plant to reduce NO x  emissions therefrom. The method of producing activated carbon may further comprise removing fines from the process gas. Fines removed from the process gas may be recycled to the activating or carbonizing steps of the method. 
     A fraction of the carbonized product (char) may be introduced into the boiler to increase heat production and/or reduce NO x  emissions. 
     The method may further comprise recycling a portion of the process gas to the activating step, the carbonizing step or both, wherein combustion of said process gas is used to generate heat. 
     In embodiments, the carbonization zone and the activation zone are distinct zones within a single unit. In embodiments, the single unit comprises a multiple hearth reactor. In alternative embodiments, the carbonization zone and the activation zone are in separate reactors. In some embodiments wherein the carbonization zone and the activation zone are in separate reactors, the separate reactors comprise rotary kilns. 
     In embodiments, the solid carbonaceous material is in the carbonization zone for a residence time and the carbonization product gases are in the carbonization zone for a residence time, and the residence time of the solid carbonaceous material in the carbonization zone is greater than the residence time of the carbonization product gases in the carbonization zone. In embodiments, the carbonized product is in the activation zone for a residence time and the activation product gases are in the activation zone for a residence time, and the residence time of the carbonized product in the activation zone is greater than the residence time of the activation product gases in the activation zone. 
     In embodiments, the activated carbon has a surface area greater than about 400 m 2 /g. 
     Also disclosed is a system for the coproduction of activated carbon and boiler-produced steam, the system comprising: a boiler in which a solid fuel from a solid fuel source is thermally converted via combustion with air to produce boiler-produced steam and flue gas, the boiler comprising a boiler-produced steam outlet and at least one flue gas outlet; an activated carbon production apparatus, the activated carbon production apparatus comprising a carbonization zone in which a carbonaceous material is carbonized to produce carbonization gases and char, the carbonization zone comprising carbonaceous material inlet, a char outlet and a carbonization gas outlet; and an activation zone in which char is activated with activation steam to produce activated carbon and activation gases, the activation zone comprising an activated carbon outlet, an activation gas outlet, and an activation steam inlet. In embodiments, solid fuel comprises coal, biomass, or a combination thereof. In embodiments, the coal is lignite. In embodiments, the lignite comprises a base to acid ratio of greater than or equal to about 0.4 and an ash content of less than or equal to about 15%. 
     In some embodiments of the system, the carbonization zone and the activation zone are distinct zones within the same reactor. In this case, the reactor may be a multiple hearth furnace. In alternative embodiments of the system, the carbonization zone and the activation zone are in separate reactors. In this case, the system may comprise at least one rotary kiln. 
     The system may further comprise an activated carbon inlet whereby a portion of the activated carbon is injected into the flue gas. In embodiments of the system, the boiler-produced steam outlet and the activation steam inlet are fluidly connected, whereby a portion of the boiler-produced steam may be introduced into the activation zone. In some embodiments, the system further comprises piping connecting the solid fuel source to the carbonaceous material inlet, whereby a portion of the solid fuel source may be introduced into the carbonaceous material inlet. 
     The present invention comprises a combination of features and advantages which enable it to overcome various problems of prior devices and methods. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic of a typical configuration for carbon injection in a coal-fired power plant. 
         FIG. 2  is a schematic according to the present disclosure of an embodiment of a system for the coproduction of activated carbon and steam/electricity, with product gas from the activated carbon production plant directed to the combustor/boiler of a steam/electricity generation plant. 
         FIG. 3  is a schematic of another embodiment according to the present disclosure of a system for the coproduction of activated carbon and steam/electricity, with product gas from the activated carbon plant directed to an aftercombustor and gases from the aftercombustor sent downstream of the combustor/boiler of a steam/electricity generation plant, e.g. upstream of flue gas cleaning unit(s) of the steam/electricity generation plant. 
         FIG. 4  is a frequency distribution of sodium (expressed as equivalent oxide) in ash from as-fired samples of suitable lignite. 
         FIG. 5  is a frequency distribution of ash (weight percent on an as-fired basis) in as-fired samples of suitable lignite. 
         FIG. 6  is a frequency distribution of calcium (expressed as equivalent oxide) in ash from as-fired samples of suitable lignite. 
         FIG. 7  is a frequency distribution of the base-to-acid component ratio of the ash derived from as-fired samples of suitable lignite. 
         FIG. 8  is a plot of ash content versus base to acid ratio for as-fired samples of suitable lignite. 
     
    
    
     NOTATION AND NOMENCLATURE 
     As used herein, the term “carbonization” refers to the devolatilization of an organic feedstock to yield carbonization gas and solid carbonized product, i.e. char. 
     Where not stated otherwise, percentages presented herein are weight percentages. 
     DETAILED DESCRIPTION 
     I. Overview 
     Herein disclosed are a system and method for combining the production of activated carbon with the generation of steam/electricity from a solid fuel boiler system. The disclosed combination may enable cost savings for the carbon activation process, the steam/electricity generation processes, or both. Steam generated by the steam/electricity generation plant may be used in the activation of the carbonized product produced in the activated carbon production apparatus (ACPA). Gases resulting from the activated carbon production apparatus may be used as fuel for steam creation, reused in activation and carbonization processes, used in solid fuel (e.g., coal) heating and/or drying, used as reburn fuel in the steam/electricity generation plant, and/or burned in an aftercombustor, as further described hereinbelow. The activated carbon produced may be used to advantage to reduce the level of a contaminant, e.g. NO x  and/or heavy metal (e.g., mercury) level, from the flue gases from the boiler, as discussed further hereinbelow. 
     The disclosed system and method simplify the production of activated carbon: the disclosed system and method may minimize the equipment required for the manufacture of activated carbon, may reduce production costs by minimizing raw carbonaceous material handling and processing, reduces the need for supplemental fuel within the activated carbon production process, eliminates the need for stand-alone steam-generating equipment for the activated carbon production process, eliminates the need for stand-alone pollution control equipment dedicated to the activated carbon production process, and produces a high-heating-value char that may be co-fired within the power plant and/or put to use in NO x  reduction technologies. 
       FIG. 1  is a schematic of a typical configuration for carbon injection in a coal-fired power plant  100 . Air  105  is heated via air heater  140  to yield heated air  120 . Heated air  120  and coal  110  enter boiler  130 , where combustion occurs. Hot flue gas  155  is used to heat air  105  in heat exchanger  140 , yielding heat-exchanged flue gas  160 . Activated carbon  150  is injected into heat-exchanged flue gas  160  or hot flue gas  155  entering air heater  140  or earlier in boiler  130  to reduce NO x  or heavy metal content therein. The contaminant-reduced flue gas  165  is sent to particulate separation device  170  wherein particles escaping boiler  130  are removed to yield particulate-reduced flue gas  177  which is sent to stack  180  for disposal. 
     As mentioned above, the presently disclosed system integrates two production systems, namely a system for the production of activated carbon and a system for the generation of steam/electricity from a carbonaceous material such as coal. By integrating these two systems, significant cost savings may be achieved both in terms of a decrease in equipment requirements, as well as a potential reduction of operating costs. 
     System 
     Details of the integration of a carbonaceous fuel (e.g., coal)-fired steam/electricity plant and activated carbon production plant will now be made with reference to  FIG. 2  which is schematic of an embodiment of an integrated system according to the present disclosure for the coproduction of activated carbon and steam/electricity, with product gas from the activated carbon production directed to a combustor/boiler of the steam/electricity generation plant. While  FIG. 2  and the following discussion describe a coal-fired boiler, it is to be understood that steam/electricity generation plant  295  may comprise any solid fuel boiler compatible with the disclosed system and methods. 
     Integrated system  250  integrates steam/electricity generation plant (hereinafter SEGP)  295  and activated carbon production plant (hereinafter ACPP)  215 . SEGP  295  comprises boiler  230 . Boiler  230  comprises an inlet for inlet coal  210 , an inlet for air  220 , an inlet for boiler feedwater  232 , an outlet for boiler-produced steam  233 , and at least one outlet for flue gas  255  produced in boiler  230 . SEGP  295  also comprises an inlet for activated carbon  245 , whereby activated carbon is intimately mixed with flue gas to reduce the level of at least one contaminant therein. 
     SEGP  295  may further comprise coal-handling apparatus, such as, by way of non-limiting example, coal source/storage  201 , coal crushing apparatus  202 , conveyor  203 , and grinder  204   a . In embodiments, SEGP  295  further comprises heat exchanger  240  wherein air  205  is heated via heat exchange in air heater  240  with hot flue gas  255  exiting boiler  230  via the outlet for flue gas  255 . SEGP may further comprise at least one steam turbine  235  for the production of electricity. SEGP  295  may further comprise apparatus for cleaning flue gas  255  prior to introduction of the flue gas to a stack  280 . Such apparatus may be any apparatus known to those of skill in the art, and may comprise, for example, at least one activated carbon inlet for introducing activated carbon  245  into the flue gas, particulate collection device  270 , and SO 2  scrubber  275 , as shown in  FIG. 2 . Preferably, the at least one inlet for activated carbon  245  is upstream of particulate collection device  270 . In the embodiment of  FIG. 2 , activated carbon  245  is injected into heat exchanged flue gas stream  260  to produce contaminate reduced flue gas stream  265 . Alternatively or additionally, activated carbon  245  may be introduced into hot flue gas  255 . 
     ACPP  285  comprises activated carbon production apparatus ACPA  211 . ACPA  211  comprises carbonization zone  208  in which carbonaceous material is carbonized to produce carbonization gases and solid carbonized product, the carbonization zone comprising an inlet for ACPP inlet stream  206 , a carbonized product outlet and a carbonization gas outlet; and an activation zone  209  in which carbonized product from the carbonization zone is activated with diverted steam  237  to produce activated carbon  213  and activation gases, the activation zone comprising an outlet for activated carbon  213 , an outlet for activation gas, and an inlet for diverted steam stream  237 . In embodiments, the outlet for steam  233  from SEGP  295  is fluidly connected to the inlet for diverted steam  237  of ACPA  211 , whereby a portion of steam  233  may be used to activate carbonized product from carbonization zone  208 . In embodiments, coal source  201  is connected with the inlet for ACPP inlet stream  206 , whereby a portion of coal from coal source  201  may be diverted for use as carbonaceous material in ACPP  285 . 
     ACPP  285  may further comprise gas/solids separator  215  fluidly connected to the outlet for carbonization gases, the outlet for activation gases, or both, whereby fines may be removed from the carbonization and/or activation gases. All or a portion of the fines-reduced gases  239  or boosted product gas  239   a  may subsequently be recycled via piping as ACPA product gas recycle stream  217  to ACPA  211 . A stream divider may be used split ACPA product gas recycle stream  217  into recycle combustion streams  227 ,  228 , and  229  with all or none of stream  217  being introduced into drying zone  207 , carbonization zone  208 , and/or activation zone  209  via product gas recycle combustion streams  227 ,  228 , and/or  229  respectively. 
     In embodiments, SEGP  295  comprises an inlet in fluid communication with ACPA  211  whereby all or a portion of the gases separated in separator  215  are sent to boiler  230  as known to those of skill in the art. In some embodiments further discussed hereinbelow, ACPP  285  further comprises aftercombustor  219 , as shown in  FIG. 3 , wherein all or a portion of the gases separated in separator  215  (and making up fines-reduced product gas  239  or boosted product gas  239   a ) are combusted. In embodiments, aftercombustor  219  is in fluid communication with SEGP  295 , whereby at least a portion of gases produced in aftercombustor  219  are introduced into the flue gas from boiler  230 . In embodiments, as shown in  FIG. 3 , at least a portion of aftercombustor gas  234  produced in aftercombustor  219  is introduced into the flue gas. In embodiments, at least a portion of aftercombustor gas  234  is introduced into the flue gas upstream of air heater  240 . In alternative embodiments, at least a portion of gases produced in aftercombustor  219  are introduced into the flue gas downstream of air heater  240 . The boiler flue gas treatment apparatus of SEGP  295  may thus be used to clean gases produced in ACPA  211 . In embodiments, at least a portion of combusted gas  234  is introduced into a combustion zone of boiler  230 , for example, to take advantage of the radiative heat transfer surface in boiler  230 . In some embodiments, at least a portion of the furnace combustion gas  234  is introduced into the solid fuel boiler system upstream of at least one pollution control device. In embodiments, at least a portion of the furnace combustion gas is introduced into the solid fuel boiler system downstream of the air heater and upstream of a pollution control device. 
     The system will be described in more detail during the following discussion of the method for the coproduction of activated carbon and steam/electricity. 
     Method 
     Raw Material/Coal Handling 
     Boiler inlet coal  210  for use in SEGP  295  may be taken from coal source  201 , crushed in coal crusher  202 , and conveyed via conveyor  203  to coal grinding  204   a . The disclosed system and method for operation of an integrated system or plant for the coproduction of activated carbon and steam/electricity, hereinafter IP  250 , take advantage of the coal-handling infrastructure of steam/power plant  295 . In stand-alone ACPPs, coal is delivered, stored, precrushed, and conveyed to a feed storage bin before being reduced to the final size in a device such as a hammer mill. In  FIG. 2 , after it has been delivered, stored, and precrushed, in embodiments, a portion of coal from coal source  201  is diverted via diverted coal stream  200  from steam/power plant conveyor  203  to ACPP  285 . 
     In embodiments, the coal is lignite. A suitable coal is a lignite such as Center lignite, described in Example 1 hereinbelow. Desirable lignites for the production of high surface area activated carbon have high base to acid ratios on low ash contents. In embodiments, the lignite has an ash content (expressed as weight % on an as-fired basis) of less than about 15%. In embodiments, the lignite has an ash content (expressed as weight % on an as-fired basis) of less than about 10%. In embodiments, the coal comprises lignite, and the lignite has a base to acid ratio of greater than about 0.4. In embodiments, the coal comprises lignite, and the lignite has a base to acid ratio of greater than about 0.5. In embodiments, the coal comprises lignite, and the lignite has a base to acid ratio of greater than about 0.6. In some embodiments, the coal is lignite, and the lignite has a base to acid ratio greater than about 0.4 and an ash content of less than about 15%. In embodiments, the coal has a high alkali and alkaline earth element content. In embodiments, the lignite has an average sodium content (expressed as weight percent of equivalent oxide, Na 2 O, in the as-fired coal ash) of greater than about 3.5%, alternatively greater than about 5%, alternatively about 5.5%. In embodiments, the lignite has an average calcium content (expressed as weight percent of equivalent oxide, CaO, in the as-fired coal ash) of greater than about 10%. 
     In embodiments, formation of activated carbon  213  via ACPP  285  is incorporated into the operation of an existing SEGP. In order to stay within the flow of existing operation of an SEGP  295 , in embodiments, the amount of coal diverted via diverted coal stream  200  is small enough that operation of the SEGP is not significantly affected by the production of activated carbon. In embodiments, the amount of coal diverted via diverted coal stream  200  is less than about 5% of the feed to the SEGP plant. In other embodiments, the amount of coal diverted via diverted coal stream  200  is less than about 3% of the feed to the steam/power plant. In still other embodiments, the amount of coal diverted via diverted coal stream  200  is less than about 2% of the feed going to the steam/power plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is greater than about 0.1% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is greater than about 0.3% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is greater than about 0.5% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is greater than 1% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is in the range of greater than about 0.1% of the feed to the SEGP plant and less than or equal to about 5% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is in the range of greater than 0.3% of the feed to the SEGP plant and less than or equal to about 5% of the feed to the SEGP plant. In embodiments, the amount of coal diverted via diverted coal stream  200  is in the range of greater than 1% of the feed to the SEGP plant and less than or equal to about 5% of the feed to the SEGP plant. 
     Grinder  204   b  may be used to further reduce the size of coal in diverted coal stream  200  prior to carbonization. ACPP inlet stream  206  comprises solid carbonaceous material. In embodiments, ACPP inlet stream  206  comprises coal having an average diameter of less than about 5″. In other embodiments, ACPP inlet stream  206  comprises coal having an average diameter of less than about 3″. In still other embodiments, ACPP inlet stream  206  comprises coal having an average diameter of less than about 1″. In embodiments, ACPP inlet stream  206  comprises coal having an average diameter of from about 0.001 inch to about 5 inches. 
     ACPP inlet stream  206  may comprise biomass in addition to or in place of the primary coal source to SEGP  295 . Suitable biomass includes, but is not limited to wood, sunflower hulls, peat, coconut shells, and combinations thereof. In specific embodiments, inlet stream  206  comprises sunflower hulls. Depending on sources of additional biomass, biomass may be mixed with diverted coal stream  200  prior to grinder  204   b , mixed downstream of grinder  204   b ; introduced into drying zone  207  of activated carbon production reactor  211 , introduced into carbonization zone  208  of activated carbon production reactor  211 , introduced into activation zone  209  of activated carbon production reactor  211 , or a combination thereof (biomass introduced via additional carbonaceous material inlets (not shown)). In embodiments, ACPP inlet stream  206  comprises additional biomass mixed with coal from diverted coal stream  200 . In embodiments, inlet stream  206  comprises about 50 weight percent biomass and about 50 weight percent lignite diverted from SEGP  295 . Without wishing to be limited by theory, the use of biomass in ACPP  211  may be beneficial to IP  250  because it is a renewable energy resource and is CO 2  neutral. For example, biomass may not be usable in the SEGP due to difficulty in feeding the biomass to the boiler. It may also not be desirable to feed biomass directly into boiler  230  due to detrimental impacts that may result from the combustion of the biomass in the boiler  230 , such as ash deposition on boiler heat transfer. Such biomass may, in embodiments, be conveniently supplied to ACPA  211 , where a significant portion of its heating value may be transferred to the product gases  218  and subsequently routed to SEGP  295  as additional fuel (CO 2 -neutral) to, for example, boiler  230 . 
     Steam/Electricity Generation Plant 
     Within SEGP  295 , boiler inlet coal  210  is thermally converted (combusted) in boiler  230  with heated air  220 . Heat exchanger  241  is used to heat boiler feedwater  232  and produce steam  233 . Heat exchanger  241  contains boiler feedwater  232  that leaves boiler  230  as steam  233 . To produce electricity, steam  233  passes through one or more (three shown in  FIG. 2 ) steam turbines  235  which may be upstream of condenser  236 . 
     Hot flue gas  255  is cooled via radiative heat exchange, convective heat exchange in convective pass  231  and air heater  240 . Prior to disposal via stack  280 , flue gas may be treated, as is well known to those of skill in the art. Such treatment may include, but is not limited to, NO x  reduction, particulate reduction, and removal of sulfur or other contaminants. In  FIG. 2 , the content of one or more contaminants of flue gas, including but not limited to mercury, NO x , and sulfur is reduced by injection of powdered activated carbon  245 , as known to those of skill in the art. 
     At least a portion of powdered activated carbon (PAC)  245  is produced in IP  250  as further described hereinbelow. In embodiments, PAC  245  is injected into flue gas having a temperature of from about 204° C. (400° F.) to about 43° C. (110° F.). In embodiments, PAC  245  is injected upstream of heat exchanger  240  into flue gas  255 . In embodiments, flue gas  255  has a temperature of from about 204° C. (400° F.) to 482° C. (900° F.). In embodiments, PAC  245  is injected downstream of heat exchanger  240  into heat-exchanged flue gas  260 . In embodiments, heat-exchanged flue gas  260  has a temperature of from about 93° C. (200° F.) to 204° C. (400° F.). In  FIG. 2 , contaminant-reduced, e.g. NO x -reduced, flue gas  265  is sent to particulate collection device  270  wherein particulates escaping boiler  230  are removed. In the embodiment in  FIG. 2 , particulate-reduced flue gas  272  is sent to SO 2  scrubber  275  wherein sulfur is removed from particulate-reduced flue gas  272 . Sulfur-reduced flue gas  277  is sent to stack  280  for disposal. 
     Activated Carbon Production Plant 
     ACPP  285  produces activated carbon product in activated carbon product stream  213  and product gases  212 . Within ACPP  285  of IP  250 , carbonization occurs within carbonization zone  208  and activation in activation zone  209 . The method may further comprise drying (and/or heating) of ACPP inlet stream  206  in drying zone  207 . ACPP  285  generates product gases  212  from both the (distinct) carbonization and activation steps, product gases comprising, without limitation, hydrocarbons, carbon monoxide, hydrogen, ammonia, hydrogen cyanide, and hydrogen sulfide. In embodiments, carbonization and steam activation are carried out in different pieces of equipment. Alternatively, in embodiments, carbonization and steam activation are carried out in different zones within the same piece of equipment, as in the embodiments of  FIGS. 2 and 3 . For example, in embodiments, drying, carbonization, and activation are carried out within a multiple hearth reactor, with separate hearths used for drying zone  207 , carbonization zone  208 , and activation zone  209 . In embodiments, each of zones  207 ,  208 , and  209  may comprise more than one hearth of a multiple hearth furnace (MHF). It is to be understood, however, that drying, carbonization, and activation may be carried out in separate pieces of equipment, or within a single piece of equipment. For example, drying and carbonization may occur in one unit, with activation being performed in a separate unit, as known to those of skill in the art. In embodiments, drying, carbonization, and activation take places in three separate units. For example, in an embodiment, drying, carbonization, and activation take place in a plurality of rotary kilns. In embodiments, ACPA  211  comprises at least one rotary kiln. In embodiments, ACPA  211  comprises three rotary kilns in series. In some embodiments in which the use of a renewable carbonaceous material to decrease CO 2  emissions is beneficial to SEGP  295 , the solid carbonaceous material used in ACPP  285  comprises biomass, as mentioned hereinabove. The use of a MHF or serial rotary kilns may allow easier thermal conversion of biomass relative to a burner, as the MHF and rotary kilns may be more readily adaptable to potential inhomogeneity and physical characteristics of the biomass. A majority of the energy of a biomass can thus be transferred to SEGP  295  via the disclosed system and method, as described in more detail hereinbelow. 
     Drying Zone 
     In  FIG. 2 , ACPA  211  comprises drying zone  207  wherein the moisture content of ACPP inlet stream  206  is reduced. In embodiments, the temperature of gases in the drying zone  207  is from about 93° C. (200° F.) to about 704° C. (1300° F.). In embodiments, the residence time of the solid material in drying zone  207  is from about 5 minutes to about 30 minutes. In embodiments, drying zone  207  yields a solid carbonaceous material having a moisture content of from about 0.1% to about 5%. 
     Carbonization Zone 
     In  FIG. 2 , activated carbon production reactor (ACPA)  211  comprises carbonization zone  208  wherein pyrolysis of solid carbonaceous material occurs. Pyrolysis (devolatization) of the carbonaceous material yields carbonization product gas (released volatiles) and solid carbonized product (char). In embodiments, the temperature of carbonization zone  208  is from about 315° C. (600° F.) to about 760° C. (1400° F.); alternatively, the temperature of carbonization zone  208  is from about 426° C. (800° F.) to about 760° C. (1400° F.); alternatively, the temperature of carbonization zone  208  is about 648° C. (1200° F.). In embodiments, the residence time of the solid material in carbonization zone  208  is from about 5 minutes to about 1 hour. Preferably, from about 10 minutes to about 30 minutes. In embodiments, the residence time of product gas in carbonization zone  208  is from about 1 second to about 20 seconds. In embodiments, the residence time of the solid carbonaceous material in carbonization zone  208  is one order of magnitude greater than the residence time of the gas in carbonization zone  208  (i.e., the solid carbonaceous material is not substantially entrained in the gas). In embodiments, the residence time of the solid carbonaceous material in carbonization zone  208  is 1.5 orders of magnitude greater than the residence time of the gas in carbonization zone  208  (i.e., the solid carbonaceous material is not entrained in the gas). In embodiments, carbonization zone  208  yields a carbonized product (char) having a surface area of from about 100 m 2 /g to about 400 m 2 /g. 
     Activation Zone 
     In  FIG. 2 , activated carbon production apparatus (ACPA)  211  comprises activation zone  209  wherein steam activation (i.e. gasification) of the solid char from carbonization zone  208  occurs. In embodiments, the carbonized material is activated substantially without cooling the carbonized material prior to activation. In activation zone  209 , char reacts with steam  237  to produce activation product gases comprising carbon monoxide and hydrogen, as well as activated carbon product  213 . In embodiments, the temperature of activation zone  209  is from about 600° C. (1112° F.) to about 1000° C. (1832° F.). In some embodiments, the temperature of activation zone  209  is about 875° C. (1607° F.). In embodiments, the residence time of the solid material in activation zone  209  is from about 10 minutes to about 3 hours. Alternatively, from about 30 minutes to about 2 hours. In embodiments, the residence time of the solid material in activation zone  209  is greater than 1 minute. In embodiments, the residence time of the solid material in activation zone  209  is greater than 10 minutes. In embodiments, the residence time of the solid material in activation zone  209  is greater than 30 minutes. In embodiments, the residence time of the solid material in activation zone  209  is greater than 60 minutes. In embodiments, the residence time of the solid material in activation zone  209  is greater than 90 minutes. In embodiments, the residence time of product gas in activation zone  209  is from about 5 seconds to about 120 seconds; in alternative embodiments, the residence time of product gas in activation zone  209  is from about 5 seconds to about 60 seconds. In embodiments, the residence time of the solid material in activation zone  209  is at least one order of magnitude greater than the residence time of the gas in activation zone  209  (i.e., the solid material is not substantially entrained in the gas). In embodiments, the residence time of the solid material in activation zone  209  is at least 1.5 orders of magnitude greater than the residence time of the gas in activation zone  209  (i.e., the solid material is not entrained in the gas). In embodiments, activation zone  209  yields an activated carbon or granular activated carbon (GAC) product having a surface area greater than about 400 m 2 /g. In embodiments, activation yields an activated carbon or granular activated carbon (GAC) product having a surface area greater than about 450 m 2 /g. In embodiments, activation zone  209  yields an activated carbon or granular activated carbon (GAC) product having a surface area greater than about 500 m 2 /g. In embodiments, activation zone  209  yields an activated carbon or granular activated carbon (GAC) product having a surface area greater than about 600 m 2 /g. In embodiments, activation zone  209  yields an activated carbon or granular activated carbon (GAC) product having a surface area greater than about 700 m 2 /g. 
     Activated Carbon or Granular Activated Carbon 
     The activated carbon or GAC in GAC product stream  213  may be further treated prior to injection into flue gas of SEGP  295 . Excess activated carbon or GAC may be transported to other locations for use or sale. For example, activated carbon GAC may be powdered further for better entrainment when injected into a flue gas. In embodiments, the activated carbon or GAC may be further treated as known to those of skill in the art, to enhance the ability of the activated carbon to remove specific contaminants from the flue gas, for example, a halogen may be deposited on the surface thereof to enhance the removal of mercury via adsorption with the treated activated carbon or GAC. 
     Steam activation, carbonization and raw material drying and heating are endothermic processes. In stand-alone ACPPs, additional fuel (typically gaseous or liquid) is combusted in the pieces of equipment performing these endothermic steps. The need for additional fuel may increase production costs in stand-alone ACPPs relative to the presently disclosed integrated plant and method, wherein product gases produced in carbonization and/or activation may be recycled and combusted to produce heat for the endothermic steps. 
     Steam Process 
     Steam is required for activation of the carbonized material produced via carbonization in  208 . For a 50-ton-per-day plant, a typical amount of steam required is 5000 lb/hr. In a stand-alone ACPP, the requisite steam is generated in a separate boiler wherein the combustible gases from the carbonization and steam activation steps are burned. The corresponding heat input required may be about 6 MMBtu/hr. In the prior art, the diversion and use of the product gases from the carbonization and activation steps for steam generation results in a smaller proportion of these combustible gases available for other parts of the process, such as for providing heat within the carbonization and activation steps. 
     In embodiments of IP  250 , a portion of steam  233  produced in the steam/electricity generation plant is used for activation of the carbonized material. In  FIG. 2 , a portion of the steam  233  produced in SEGP  295  is diverted via diverted steam stream  237  to ACPP  285  for steam activation of the carbonized product. Since steam need not be manufactured by the activated carbon plant, no separate boiler dedicated to activated carbon production is needed in the disclosed IP  250 . Furthermore, combustible gases  212  from the carbonization and/or activation steps are fully available for combustion in and providing heat for further activation and carbonization as well as for use in the steam/electricity generation steps, as further discussed hereinbelow. 
     In embodiments such as the embodiment of  FIG. 2 , diverted steam  237  is diverted from the intermediate-pressure turbine exhaust. In embodiments, diverted steam  237  has a pressure greater than about 1 bar to facilitate transport from SEGP  295  to ACPP  285  and to overcome any transportation, distribution, and injection pressure drops. In embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is greater than about 0.1% of steam  233  generated in SEGP  295 . In embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is greater than about 0.3% of steam  233  generated in SEGP  295 . In embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is greater than about 0.5% of steam  233  generated in SEGP  295 . In embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is less than about 5% of steam  233  generated in SEGP  295 . In some embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is less than 2% of steam  233  generated in SEGP  295 . In embodiments, the amount of steam diverted from SEGP  295  via diverted steam  237  is less than 1% of steam  233  generated in SEGP  295 . In embodiments, the amount of steam diverted from SEGP  295  via diverted steam stream  237  is in the range of from 0.1% to about 5%; from 0.3% to about 5%; from 0.5% to about 5%; from 1% to about 5%; from 0.1% to about 2%; from 0.3% to about 2%; from 0.5% to about 2%; or from 1% to about 2% of the steam  233  generated in SEGP  295 . 
     Product Gases from Activated Carbon Plant 
     In the embodiment of  FIG. 2 , hot product gases from the activation in activation zone  209  are directed to the carbonization step in carbonization zone  208 , the solids and product gases flowing in countercurrent fashion, and the final product gases  212  leave carbonization zone  208 . In other embodiments, the solids and the product gases may flow in a co-current fashion for both a rotary kiln and a multiple hearth furnace. In embodiments described further hereinbelow, product gases resulting from carbonization and product gases resulting from activation may be sent to different places within IP  250 . For example, at least a portion of the carbonization product gases or a combustion product thereof, at least a portion of the activation product gases or a combustion product thereof, or at least a portion of both may be sent to SEGP  295 . This contrasts with prior art stand-alone ACPPs where the activated carbon production plant itself comprises a combustion chamber/boiler wherein product gases  212  are combusted to generate heat/steam for the activation. 
     In embodiments, a portion of the activation and/or carbonization product gases is used as fuel for steam activation, carbonization and/or coal-heating and drying steps. In  FIG. 2 , product gases leaving activation step  209  are directed to the zone where carbonization and coal drying/heating (zones  208 ,  207 ) are performed. Product gases  212  leaving carbonization step  208  may be retained at a high temperature to prevent condensation of tars. Hot-gas booster fan  214  may be used to boost the pressure of combustible gases in product gas stream  212  or fines-reduced product gas stream  239  to yield boosted gas stream  239   a . In embodiments, product gas  212 , fines-reduced product gases  239 / 239   a , a portion thereof, or a combination thereof is directed to drying/heating zone  207 , activation zone  208 , and/or carbonization zone  209  where the product gases are combusted (e.g. with additional air) to provide heat as necessary. For example, a portion of product gas  212  may be diverted via ACPA product gas recycle stream  217  and sent back to ACPA  211 . Fractions of ACPA product gas recycle stream  217  may be sent to heating/drying zone  207 , carbonization zone  208 , and activation zone  209  via product gas recycle combustion streams  227 ,  228 , and  229  respectively. Air may be added to combust with streams  227 ,  228 , and/or  229  via air streams  224 ,  225 , and  226  respectively. Additional fuel, as needed, may be added to zones  207 ,  208 , and  209  of ACPA  211  via supplemental fuel streams  221 ,  222 , and  223 . 
     A separator upstream of booster fan  214  may be used to remove fine particles (fines) from the product gases from carbonization zone  208 , activation zone  209 , or both. The separator may comprise any means known to those of skill in the art whereby fines may be separated from the product gases, for example, cyclonization. In the embodiment of  FIG. 2 , for example, product gases  212  enter separator, e.g. cyclone,  215 . Fines are removed from separator  215  via fines recycle stream  216 . The fine carbonaceous particles may then be recycled to the activation or carbonization steps (not shown in  FIG. 2 ). 
     In the IP of the present disclosure, precise temperature control, if required within the various zones or pieces of equipment of the ACPA, may be difficult to achieve by combustion of ACPA product gas recycle  217 , as the quality of the product gas will vary with input quality of ACPP inlet  206 . To overcome this issue, in embodiments, not all heat required within ACPA  211  is generated from combustion of product gases. Rather, a portion of the heat supply may be provided by combustion of supplementary gaseous/liquid fuel supplied to heating/drying zone  207 , carbonization zone  208 , and/or activation zone  209  via supplemental fuel streams  221 ,  222 , and  223  respectively. The amount of combustion of supplemental fuel may be controlled to achieve the prescribed temperature in each of the zones or pieces of equipment in ACPP  285 . 
     In the integrated plant, the portion of product gases not redirected to the activated carbon production equipment, i.e. remaining product gas stream  218 , can be utilized in various ways. In  FIG. 2 , remaining product gas stream  218  is directed to combustion zone  230  of SEGP  295 , where it is used as fuel, for example reburn (secondary combustion) fuel. In embodiments, remaining product gas stream  218  comprises at least a portion of activation product gases, at least a portion of carbonization product gases, or a combination thereof. The use of at least a portion of remaining product gas stream  218  as reburn fuel may be particularly advantageous as it may reduce the level of at least one contaminant in the flue gas. For example, use of at least a portion of remaining product gas stream  218  as reburn fuel may reduce SEGP  295  emissions of nitrogen oxide. In embodiments, the heat input of the portion of remaining product gas stream  218  directed to SEGP  295  is greater than about 0.1% of the total heat input of SEGP  295 . In embodiments, the heat input of the portion of remaining product gas stream  218  directed to SEGP  295  is greater than about 0.3% of the total heat input of SEGP  295 . In embodiments, the heat input of the portion of remaining product gas stream  218  sent to SEGP  295  is less than about 5% of the total heat input of SEGP  295 . In alternative embodiments, the heat input of the portion of remaining product gas stream  218  sent to SEGP  295  is less than 2% of the total heat input of SEGP  295 . In still other embodiments, the heat input of the portion of remaining product gas stream  218  sent to SEGP  295  is less than 1% of the total heat input of SEGP  295 . In embodiments, the heat input of the portion of remaining product gas stream  218  directed to SEGP  295  is in the range of from 0.1% to about 5% of the total heat input of SEGP  295 ; from about 0.3% to about 2% of the total heat input of SEGP  295 ; from about 0.5% to about 2% of the total heat input of SEGP  295 , from 1% to about 5% of the total heat input of SEGP  295 ; from about 0.1% to about 2% of the total heat input of SEGP  295 ; from about 0.3% to about 2% of the total heat input of SEGP  295 ; from about 0.5% to about 2% of the total heat input of SEGP  295  or from 1% to about 2% of the total heat input of SEGP  295 . 
     In embodiments, product gases produced in activation zone  209 , which activation product gases contain predominantly hydrogen and carbon monoxide, are used as reburn fuel in SEGP  295 . The use of product gases from activation zone  209  as reburn fuel may reduce NO x  emissions from solid fuel boiler  230 . In embodiments, product gases produced in carbonization zone  208  from pyrolysis of high molecular weight carbonaceous material are introduced into a gas furnace or aftercombustor as further described hereinbelow. As previously mentioned, carbonization produces carbonization product gas and solid carbonized product, i.e. char. The char product produced as an intermediate step in the integrated activated carbon production has a high heating value. In embodiments, at least a portion of char produced in carbonization zone  208  is cofired with fuel in SEGP  295  to improve combustion. In embodiments, a portion of char produced in carbonization zone  208  is used in a separate process for the reduction of NO x  in the lower-temperature regions of the boiler. NO x  reduction may comprise low-temperature gasification which NO x  levels by converting NO to N 2  upon contact of the NO x -containing flue gas with char particles. 
     AfterCombustor 
       FIG. 3  is a schematic of another embodiment of an IP  250  according to the present disclosure for the coproduction of activated carbon and steam/electricity. In this embodiment, at least a portion of the remaining product gas stream  218  not recycled to the activated carbon production equipment is burned with air  238  in aftercombustor  219 . At least a portion of furnace combustion gas  234  may be directed to convective pass  231  or other position upstream of air heater  240  of SEGP  295 , whereby the energy in furnace combustion gas  234  is extracted. In this manner, no additional heat-transfer equipment is present other than what is already available at SEGP  295 . In embodiments, the heat input of furnace combustion gas  234  directed to SEGP  295  from aftercombustor  219  of ACPP  285  is greater than about 0.1% of the total heat input of SEGP  295  or greater than about 0.3% of the total heat input of SEGP  295 . In embodiments, the heat input of furnace combustion gas  234  from aftercombustor  219  of ACPP  285  is less than about 5% of the total heat input of SEGP  295 , less than 2%, or alternatively less than 1% of the total heat input of SEGP  295 . Table 2 of Example 2 hereinbelow presents exemplary flow rates and temperatures for various streams according to an embodiment as in  FIG. 3 . In embodiments, the heat input of furnace combustion gas  234  from aftercombustor  219  of ACPP  285  is in the range of from 0.1% to about 5%, from 0.3% to about 5%, from 0.5% to about 5%, from 1% to about 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, or from 1% to 2%. 
     Cleaning ACPP Process Gas 
     In a stand-alone activated carbon production plant, product gases from carbonization and activation steps are combusted in an associated boiler to generate steam. The flue gases from this boiler contain pollutants including nitrogen oxides, sulfur oxides, trace metals, and particulates. Depending on regulatory requirements, the flue gas must be cleaned to varying degrees before discharge into the atmosphere via a stack. The flue gas may be cleaned as known to those of skill in the art. Typically, a particulate removal device such as a fabric filter or an electrostatic precipitator is used for reducing particulate emissions, and a wet or dry flue gas desulfurization device is used for reducing SO 2  emissions. These requirements impart additional costs in terms of equipment required in a stand-alone plant as well as additional operating costs. 
     In the IP of the present disclosure, at least a portion of the product gases from carbonization zone  208 , activation zone  209 , or both is introduced into the combustion zone of a SEGP to act as a reburn fuel or is combusted in an aftercombustor (gas furnace) and the hot combusted gases advantageously introduced into SEGP  295 , for example, into the convection pass section  231  or upstream of a flue gas cleaning section of the steam/electricity generation plant  295 . The injection location for product gases from the activated carbon plant in all embodiments is thus before at least one air pollution control device of SEGP  295 , thus eliminating the need for stand-alone pollution control equipment dedicated to the activated carbon production process. The at least one pollution control device may be selected from the group consisting of selective catalytic control systems for nitrogen oxide control, selective non-catalytic control systems for nitrogen oxide control, particulate collection devices (such as, for example, fabric filters, electrostatic precipitators, particulate scrubbers, and cyclones) for particulate emission control, desulfurization scrubbers for sulfur oxide control, including without limitation, sulfur scrubbers such as dry scrubbers, semi-dry scrubbers, wet flue gas desulfurization devices, and combinations thereof. 
     In embodiments, the amount of combusted gases from the activated carbon plant, in cases where an aftercombustor is used, or the amount of combusted gases that would result from the combustion of the product gases from the carbonization and activation steps of the activated carbon plant if the product gases are directed to the combustion section of the SEGP, is less than about 5% of the total flue gas flowing through the SEGP; alternatively, less than 2%; alternatively less than 1%. In embodiments, the amount of combusted gases from the activated carbon plant, in cases where an aftercombustor is used, or the amount of combusted gases that would result from the combustion of the product gases from the carbonization and activation steps of the activated carbon plant if the product gases are directed to the combustion section of the SEGP, is greater than about 0.1% of the total flue gas flowing through the SEGP. In embodiments, the amount of combusted gases from the activated carbon plant, in cases where an aftercombustor is used, or the amount of combusted gases that would result from the combustion of the product gases from the carbonization and activation steps of the activated carbon plant if the product gases are directed to the combustion section of the SEGP, is greater than about 0.3% of the total flue gas flowing through the SEGP. Thus, in embodiments, the amount of combusted gases from the activated carbon plant, in cases where an aftercombustor is used, or the amount of combusted gases that would result from the combustion of the product gases from the carbonization and activation steps of the activated carbon plant if the product gases are directed to the combustion section of the SEGP, is in the range of from 0.1% to 5%, from 0.3% to 5%, from 0.5% to 5%, from 1% to 5%, from 0.1% to 2%, from 0.3% to 2%, from 0.5% to 2%, from 1% to 2%, from 0.1 to 1%, from 0.3% to 1%, from 0.5% to 1%, or may be greater than 1%. 
     EXAMPLES 
     The invention having been generally described, the following examples are given as particular aspects of the invention and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification of the claims to follow in any manner. 
     Example 1 
     Lignite 
     A database comprising 1317 as-fired samples of Center lignite was analyzed. The average, standard deviation, maximum, minimum and selected percentiles for ash, sulfur, heating value, and selected ash constituents are included in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Statistical analysis of Ash, Sulfur, Heating Value, and Selected Ash Constituents. 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 Ash 1   
                 S 1   
                 Heating value 2   
                 CaO 3   
                 MgO 3   
                 K 2 O 3   
                 Na 2 O 3   
                 B/A 4   
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Average 
                 9.64 
                 1.0 
                 6578 
                 13.2 
                 4.0 
                 1.3 
                 4.4 
                 0.7 
               
               
                 Standard Deviation 
                 2.0 
                 0.27 
                 179 
                 3.17 
                 0.8 
                 0.4 
                 2.2 
                 0.34 
               
               
                 Max 
                 25.5 
                 2.6 
                 7101 
                 24.0 
                 7.1 
                 2.3 
                 13.0 
                 2.5 
               
               
                 Min 
                 5.0 
                 0.5 
                 5852 
                 6.8 
                 2.3 
                 0.2 
                 0.6 
                 0.3 
               
               
                 90th Perc. 
                 12.51 
                 1.29 
                 6820 
                 19.9 
                 5.7 
                 1.9 
                 8.7 
                 1.26 
               
               
                 10th Perc. 
                 7.06 
                 0.72 
                 6359 
                 9.7 
                 3.0 
                 0.6 
                 2.0 
                 0.44 
               
               
                 45th Perc. 
                 9.33 
                 0.90 
                 6552 
                 12.2 
                 3.8 
                 1.4 
                 4.1 
                 0.59 
               
               
                 55th Perc. 
                 9.75 
                 0.94 
                 6592 
                 12.7 
                 4.0 
                 1.4 
                 4.6 
                 0.64 
               
               
                 50 th  Perc. 
                 9.53 
                 0.93 
                 6572 
                 12.5 
                 3.89 
                 1.4 
                 4.4 
                 0.61 
               
               
                   
               
               
                   1 Weight percent on an as-fired basis. 
               
               
                   2 Heating express as BTU/lb on an as-fired basis. 
               
               
                   3 Weight percent of the ash, elemental weight percent express as equivalent oxide. 
               
               
                   4 B/A is the base to acid ratio of the ash constituents (B/A = [Na 2 O + MgO + CaO + K 2 O + FeO]/[SiO 2  + Al 2 O 3  + TiO 2 ]). 
               
            
           
         
       
     
     The results of the analysis show that the lignite ash has an average sodium content of 4.4%; however, there is a multimodal distribution of sodium levels in the coal ash, as shown in  FIG. 4  which is a plot of the distribution of sodium oxide in Center lignite ash.  FIG. 5  shows the frequency distribution of ash constituents. The higher ash content values were not included in the plot. However, a sample with 25.5% ash is included in the database.  FIG. 6  is a frequency distribution of calcium.  FIG. 7  is distribution frequency plot of the base-to-acid ratio of the ash derived from the coals in the Center lignite as-fired database. The distributions need to be used along with the average, standard deviation, minimum and maximum information to assess ash behavior.  FIG. 8  shows the relationship between ash content and the base to acid ratio. Desirable coals for the activated carbon may have a base to acid ratio greater than or equal to about 0.4 and an ash content less than or equal to about 15%. 
     Example 2 
     Process Flow Parameters 
     In embodiments, ACPA  211  of IP  250  comprises a multiple hearth furnace. Flow rates and temperatures of an exemplary process according to an embodiment according to  FIG. 2  comprising a MHF are presented in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Process Flow Parameters 
               
            
           
           
               
               
               
               
               
            
               
                 Stream 
                 Temp, ° F. 
                 lb/hour 
                 SCFM 
                 ACFM 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 200 - Wet coal feed 
                 60 
                 15700 
                   
                   
               
               
                 221 + 222 + 223 + 
                 60 
                 100 
                 10 
                 10 
               
               
                 227 + 228 + 229 
               
               
                 Multiple Hearth Furnace 
               
               
                 (MHF) Fuel 
               
               
                 224 + 225 + 226 
                 60 
                 870 
                 200 
                 200 
               
               
                 MHF Burner Air + 
               
               
                 Injection Air 
               
               
                 237 
                 250 
                 5000 
                 700 
                 950 
               
               
                 MHF Steam 
               
               
                 212 
                 825 
                 50000 
                 10000 
                 25000 
               
               
                 MHF Exhaust Gas 
               
               
                 238 
                 60 
                 12000 
                 2500 
                 2500 
               
               
                 Post Combustor Air Supply 
               
               
                 213 
                 1650 
                 5000 
               
               
                 Hot Product 
               
               
                 234 
                 1700 
                 50000 
                 12500 
                 50000 
               
               
                 Post Combustor Exhaust Gas 
               
               
                   
               
            
           
         
       
     
     Example 3 
     Carbonization of Biomass, Coal, and Blend of Coal and Biomass 
     Production of activated carbon was carried out in a pilot-scale rotary kiln system. Carbonization is first described and steam activation of carbonized char is described thereafter. High potassium sunflower hulls were from a sunflower processing plant in North Dakota, Center lignite coal received from BNI coal. Both sunflower hulls and center lignite coals were sized to nominal −⅛-in. +10-mesh material. A hull and coal blend (HCB) comprising a one to one mass ratio basis of sunflower hull to center lignite coal was carbonized, along with sunflower hull alone and coal alone. Carbonization was performed at 600° C. in the rotary kiln system. The test matrix of the carbonization process is given in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Test Matrix for Carbonization Tests in Rotary Kiln 
               
            
           
           
               
               
               
            
               
                 Feed Material 
                 Carbonization Temperature, ° C. 
                 Reactor 
               
               
                   
               
               
                 Sunflower Hull 
                 600 
                 Rotary kiln 
               
               
                 Coal 
                 600 
                 Rotary kiln 
               
               
                 Hull and Coal Blend 
                 600 
                 Rotary kiln 
               
               
                   
               
            
           
         
       
     
     The results of the proximate, ultimate, and bulk ash chemistry analyses performed on sunflower hull and coal are presented in Table 4 and Table 5. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Analysis of High Potassium Sunflower Hull 
               
            
           
           
               
               
               
            
               
                   
                 As Sampled 
                 Moisture Free 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Proximate Analysis, wt % 
                   
                   
               
               
                   
                 Moisture Content 
                 6.82 
                 NA* 
               
               
                   
                 Volatile Matter 
                 73.84 
                 79.24 
               
               
                   
                 Fixed Carbon 
                 17.33 
                 18.60 
               
               
                   
                 Ash 
                 2.01 
                 2.16 
               
               
                   
                 Ultimate Analysis, wt % 
               
               
                   
                 Hydrogen 
                 6.98 
                 6.68 
               
               
                   
                 Carbon 
                 44.26 
                 47.50 
               
               
                   
                 Nitrogen 
                 1.25 
                 1.34 
               
               
                   
                 Sulfur 
                 0.13 
                 0.14 
               
               
                   
                 Oxygen 
                 45.37 
                 42.18 
               
               
                   
                 Ash 
                 2.01 
                 2.16 
               
               
                   
                 Ash Analysis, wt % 
               
               
                   
                 SiO 2   
                   
                 5.50 
               
               
                   
                 Al 2 O 3   
                   
                 0.40 
               
               
                   
                 Fe 2 O 3   
                   
                 0.15 
               
               
                   
                 TiO 2   
                   
                 0.04 
               
               
                   
                 P 2 O 5   
                   
                 7.40 
               
               
                   
                 CaO 
                   
                 11.30 
               
               
                   
                 MgO 
                   
                 9.58 
               
               
                   
                 Na 2 O 
                   
                 0.00 
               
               
                   
                 K 2 O 
                   
                 59.89 
               
               
                   
                 SO 3   
                   
                 4.42 
               
               
                   
                 BaO 
                   
                 0.02 
               
               
                   
                 SrO 
                   
                 0.03 
               
               
                   
                   
               
               
                   
                 *Not applicable. 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Analysis of Center Lignite Coal 
               
            
           
           
               
               
               
            
               
                   
                 As Sampled 
                 Moisture Free 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Proximate Analysis, wt % 
                   
                   
               
               
                   
                 Moisture Content 
                 22.17 
                 NA* 
               
               
                   
                 Volatile Matter 
                 40.56 
                 52.11 
               
               
                   
                 Fixed Carbon 
                 31.72 
                 40.75 
               
               
                   
                 Ash 
                 5.56 
                 7.14 
               
               
                   
                 Ultimate Analysis, wt % 
               
               
                   
                 Hydrogen 
                 5.92 
                 4.44 
               
               
                   
                 Carbon 
                 50.71 
                 65.16 
               
               
                   
                 Nitrogen 
                 0.98 
                 1.26 
               
               
                   
                 Sulfur 
                 0.79 
                 1.02 
               
               
                   
                 Oxygen 
                 36.04 
                 20.98 
               
               
                   
                 Ash 
                 5.56 
                 7.14 
               
               
                   
                 Ash Analysis, wt % 
               
               
                   
                 SiO 2   
                   
                 13.80 
               
               
                   
                 Al 2 O 3   
                   
                 8.50 
               
               
                   
                 Fe 2 O 3   
                   
                 9.48 
               
               
                   
                 TiO 2   
                   
                 0.26 
               
               
                   
                 P 2 O 5   
                   
                 0.13 
               
               
                   
                 CaO 
                   
                 25.10 
               
               
                   
                 MgO 
                   
                 6.88 
               
               
                   
                 Na 2 O 
                   
                 12.35 
               
               
                   
                 K 2 O 
                   
                 0.57 
               
               
                   
                 SO 3   
                   
                 21.60 
               
               
                   
                 BaO 
                   
                 0.62 
               
               
                   
                 SrO 
                   
                 0.69 
               
               
                   
                   
               
               
                   
                 *Not applicable. 
               
            
           
         
       
     
     Carbonization was carried out on a semi-continuous basis. The feed material was loaded into the feeder hopper and refilled as needed. Table 6 shows the operating conditions, and characteristics of the char produced. Product yield was higher for carbonization tests using Center lignite coal compared to sunflower hulls. The product char yield was 22.33, 41.8, and 30.62% respectively for sunflower hull, center lignite coal, and HCB. Tables 4 and 5 show that volatile content of sunflower hulls is higher than that of center lignite coal, and carbon content of center lignite coal is higher than that of sunflower hull. The carbonization process drives out moisture and volatiles from the feed material leaving carbon in the char. The difference in volatile matter, and fixed carbon contents of sunflower hull and coal are reasons for variation in char yield. The iodine number is a simple measure of surface area on activated carbons and was measured according to ASTM D4607-94. The iodine number tracks the internal surface area (micropores) of the sorbent as absorption of iodine in mg I 2 /g carbon. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Test Conditions for Carbonization Tests of Sunflower 
               
               
                 Hulls, Center Lignite Coal, and Hull and Coal 
               
               
                 Blend, −⅛-in. +10-Mesh Particle-Size Fraction 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Test No.: 
                 1 
                 2 
                 3 
               
               
                   
                   
               
               
                   
                 Feed Material 
                 Sunflower 
                 Center 
                 Hull and 
               
               
                   
                   
                 Hull 
                 Lignite 
                 Coal Blend 
               
               
                   
                 Feed Moisture, wt % 
                 6.82 
                 22.17 
                 N/A 
               
               
                   
                 Temperature, ° C. 
                 600 
                 600 
                 600 
               
               
                   
                 Tube Incline, ° 
                 1 
                 1 
                 1 
               
               
                   
                 Tube Speed, rpm 
                 2 
                 2 
                 2 
               
               
                   
                 Feed Rate, lb/hr 
                 10 
                 10 
                 10 
               
               
                   
                 Material Processed, lb 
                 30 
                 50 
                 40 
               
               
                   
                 Char Recovered, lb 
                 6.70 
                 20.90 
                 12.25 
               
               
                   
                 Product Yield, % 
                 22.33 
                 41.8 
                 30.62 
               
               
                   
                 Iodine No., mg I 2 /g 
                 175 
                 291 
                 110 
               
               
                   
                   
               
            
           
         
       
     
     Example 4 
     Steam Activation of Carbonized Char 
     Steam activation of carbonized char was carried out with three different types of char described in Table 7. Sample 4 comprises char derived from coal alone; sample 5 comprises char derived from carbonization of a 1:1 mass ratio of sunflower hull:coal (HCB char); and sample 6 comprises a 1:1 mass ratio of coal char:sunflower hull char (i.e. sample 6 is a blend of individually-derived chars). 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Test Matrix for Steam Activation Tests in Rotary Kiln 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Activation 
                   
                 Steam 
                   
               
               
                 Feed 
                 Temperature, 
                   
                 Rate, 
                 Residence 
               
               
                 Material 
                 ° C. 
                 Reactor 
                 lb/hr 
                 Time, min 
               
               
                   
               
               
                 Coal Char (#4) 
                 875 
                 rotary kiln 
                 4 
                 90 
               
               
                 Blend Char 1  (#5) 
                 875 
                 rotary kiln 
                 4 
                 90 
               
               
                 Coal and Hull 
                 875 
                 rotary kiln 
                 4 
                 90 
               
               
                 char 2  (#6) 
               
               
                   
               
               
                   1 Blend char is derived from coal:hull = 1:1 (mass basis) of raw material 
               
               
                   2 Coal char:hull char = 1:1 (mass basis) 
               
            
           
         
       
     
     Steam activation was carried at around 5.5 lb/hr of char feed rate and 4 lb/hr of steam flow rate. Activation was carried out at 875° C. with residence time of 90 minutes. Table 8 shows the operating conditions for the steam activation tests performed using chars described in Table 7. From iodine number comparison, activation of HCB char (Sample #5) produced more surface area compared to activation of char derived from coal alone (Sample #4) and activation of a 1:1 mass ratio blend of individually carbonized sunflower hull char and coal char (Sample #6). Activated carbon derived from at least a portion of sunflower hulls appears to comprise an increased surface area relative to fully coal-derived activated carbon. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Test Conditions for Optimization Test of Char Derived 
               
               
                 from Sunflower Hull, Coal, and Blend of Coal and Hull 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Coal 
                 Blend 
                 Coal and 
               
               
                   
                 Feed Material 
                 Char #4 
                 Char #5 
                 Hull Char #6 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Activation Temp., ° C. 
                 875 
                 875 
                 875 
               
               
                   
                 Tube Incline, ° 
                 1 
                 1 
                 1 
               
               
                   
                 Tube Speed, rpm 
                 1.31 
                 1.31 
                 1.31 
               
               
                   
                 Est. Res. Time, min 
                 90 
                 90 
                 90 
               
               
                   
                 Char Feed Rate, lb/hr 
                 5.5 
                 5.5 
                 5.5 
               
               
                   
                 Steam Rate, lb/hr 
                 4 
                 4 
                 4 
               
               
                   
                 Char Processed, lb 
                 10 
                 9.15 
                 10 
               
               
                   
                 Carbon Recovered, lb 
                 6.45 
                 5.2 
                 6.7 
               
               
                   
                 Iodine No., mg I 2 /g 
                 803 
                 964 
                 815 
               
               
                   
                   
               
            
           
         
       
     
     As mentioned hereinabove, the iodine number for activated carbon is a parameter that is used as a measure of the surface area of the product. Previous pilot-scale tests (not shown here) show activation temperature is a key variable impacting product surface area. Pilot-scale tests also confirmed that longer residence time increases the iodine number of activated carbon. An activated carbon with a surface area in the range of 800 to 965 mg I 2 /g product was obtained from the activation of char produced by carbonization of 1:1 mass ratio sunflower hull:Center North Dakota lignite. Steam activation of Center North Dakota lignite alone yielded iodine numbers of 500 to 800 mg I 2 /g under similar carbonization and activation conditions. 
     While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of the term “optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc. 
     Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the preferred embodiments of the present invention. The discussion of a reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent they provide exemplary, procedural or other details supplementary to those set forth herein.