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DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

Description: The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this report evaluates and compares several routes for the production of activated carbons from unburned carbon in fly ash, including physical and chemical activation methods. During the present reporting period (June 30, 2001-June 29, 2002), additional characterization work was conducted under Task 1 ''Procurement and characterization of CCBPs''. The suite collected includes samples from pulverized utility boilers, a utility cyclone unit equipped with a beneficiation technology, a stoker, and a fluidized bed combustor. Proximate, ultimate, and petrographic analyses of the fly ash samples previously collected were measured. Furthermore, the surface areas of the samples assembled were characterized by N{sub 2} adsorption isotherms at 77 K. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt%), while volatile matter contents of the samples varied between 0.45 to 24.8 wt%. The ultimate analyses of all the fly ash samples showed that they contained primarily carbon, while the hydrogen contents of all the samples were very low. In addition, during the current reporting period, also Task 2 ''Development of activated carbons'' and Task 3 ''Characterization of activated carbons'' were continued.
Date: September 27, 2002
Creator: Schobert, Prof. Harold H.; Maroto-Valer, Dr. M. Mercedes & Lu, Ms. Zhe
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

Description: The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly fly ash containing unburned carbon. However, the carbonaceous residue in fly ash, unburned carbon (UC), is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this research program focuses on the development of activated carbons from the unburned carbon present in fly ash. During the present reporting period (June 30, 1999--June 29, 2000), Task 1 ''Procurement and characterization of CCBPs'' was initiated and samples from various combustion systems were collected. The suite assembled thus far includes samples from pulverized utility boilers with low-NOx burners and Selective Non Catalytic Reduction system, and also from an utility cyclone unit. The characterization studies showed that the sample from the cyclone unit contained the highest carbon content (LOI of {approx} 80%), since this unit has been retrofitted with a technology to separate the unburned carbon from the fly ash. In contrast, the sample from the unit retrofitted with a Selective Non Catalytic Reduction system showed the lowest carbon content with LOI values around 2-4%. The samples from the utility boilers with low-NOx burners were collected from the hot-side hoppers and present carbon contents {approx} 50%. The BET (N{sub 2} 77K) surface areas of the samples investigated were between 30-40 m{sup 2}/g and the pore volume is mainly due to mesopores. In addition, during this reporting period, also Task 2 ''Development of activated carbons'' and Task 3 ''Characterization of activated carbons'' were initiated. The investigations showed that after steam activation at 850 C, the unburned carbon samples generated activated carbons with microporous structure and surface areas ...
Date: July 31, 2000
Creator: Schobert, Prof. Harold H.; Maroto-Valer, Dr. M. Mercedes & Lu, Ms. Zhe
Partner: UNT Libraries Government Documents Department

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

Description: The implementation of increasingly stringent Clean Air Act Regulations by the coal utility industry has resulted in an increase in the concentration of unburned carbon in coal combustion fly ash. In 1999, around 6 million tons of unburned carbon were disposed in the US, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, this report evaluates and compares several routes for the production of activated carbons from unburned carbon, including physical activation with steam or CO{sub 2}, and chemical activation using KOH pretreatment. During the present reporting period (June 30, 2000--June 29, 2001), Task 1 ''Procurement and characterization of CCBPs'' was concluded, including samples from pulverized utility boilers, a utility cyclone unit equipped with a beneficiation technology, a suspension-fired research boiler, and a class C fly ash. The characterization studies showed that the samples collected have significantly different carbon contents, as determined by the ASTM C114 procedure, with the sample from the cyclone unit containing the highest carbon content (LOI of {approx} 80%), since this unit has been retrofitted with a technology to separate the unburned carbon from the fly ash. The porosity of the samples assembled was characterized by N{sub 2} adsorption isotherms at 77K. The surface areas of the class F fly ash samples from pulverized coal combustors are between 30-40 m{sup 2}/g, while the samples from the suspension-fired research boiler had surface area around 115 m{sup 2}/g. As expected, the surface areas of the class C ash is much higher than that of the class F ashes, with values up to 390 m{sup 2}/g. In addition, during the current reporting period, also ...
Date: September 29, 2001
Creator: Schobert, Prof. Harold H.; Maroto-Valer, Dr. M. Mercedes & Lu, Ms. Zhe
Partner: UNT Libraries Government Documents Department