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Emission fluxes of heavy metals from the fluidized bed combustion of fossil fuels
J. Aerosol Sci., Vol. 26. Suppl I, pp. $655-$656, 1995 Elsevier Science Ltd Printed in Great Britain 0021-8502/95 $9.50 + 0.00
ll~Dernalnon
EMISSION FLUXES OF HEAVY METALS FROM THE FLUIDIZED BED COMBUSTION OF FOSSIL FUELS (A project supported from 1995 by GA CR No 104/95/0653) J. SMOLIK, M. HARTMAN, I. S~KOROVA#, J. KUCERA## Institute of Chemical Process Fundamentals AS CR, Rozvojovfi 135, !65 02 Prague 6 #Institute of Rock Structure and Mechanics AS CR, V Hole~ovi~k~ich41, 182 09 Prague 8 ##Nuclear Physics Institute AS CR, 250 68 l~e~at Prague KEYWORDS Coal combustion,Combustion aerosols, Heavy metals emissions MOTIVATION The air pollution, especially exposure to high levels of particulates, is thought to be the most important external factor affecting human health. The damage caused by toxic elements, attached to the airborne particulate matter is highly exacerbated by relatively high ambient level of sulphur dioxide and other gases. In the Czech Republic about 70% of solid emissions (about 350 kt in 1992) released into the atmosphere originate from low rank coal and lignite fired in power and heating plants and households. This coal is produced mainly in Most and Sokolov Basins (about 75 Mt in 1994). With eleven thermal power plants (four of them with output above 500 MW) belongs this region to so called "Black Triangle". In 1992 25% particulate pollutants, 46% of SO2 and 31% of NOx emissions in the Czech Republic were produced in this area. The project "Emission Fluxes of Heavy Metals in the Fluidized Bed Combustion of Fossil Fuels" is aimed at a fundamental understanding of the process when a metals containing fuel is introduced into a fluidized bed combustor equipped with standard, effluent gas cleaning facilities such as cyclones, barrier filters and wet scrubbing. To asses the potential environmental and toxic effects of metal species, a detailed physical and chemical charecteristic of suspended particulate matter will be established (size, shape, chemical composition). While the primary objective of the project is to provide a fundamental understanding of the intricate phenomena involved, it is also the authors ambition to contribute to the amelioration of the damaged environment of the Czech Republic. For this purpose the measurements will be carried out with samples of brown coal from North Bohemian Brown Coal Mining Area (Most and Sokolov Basins) which are mostly used in the Czech Republic.
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GOALS OF THE PROJECT To explore quantitatively the division of hazardous metals (e.g. arsenic, cadmium, chromium, cooper, lead, mercury, zinc) between different emissinon streams (bottom bed ash, fly ash captured in cyclones, fly ash from wet scrubbing, ultrafine solids remaining in flue gas) when brown coal originated from different open-pit mines are fired. To examine the size and composition distributions of particulate matter emisions at different stages of the overall combustion process: above the bed, at the top ofa combustor, at the inlet and outlet of the cyclone, and in the stack flue gas. To evaluate the influence of the operating conditions of the fluidized bed combustor on the formation and release of metals emissions: bed temperature, residence time of solids and gas, concentration of oxygen. To investigate physical and chemical interactions between the metals species and the bed material" ash, ceramsite, additions od silica sand and limestone. To find a relationship between the mineral matrix of coal and the release of metals. To examine the overall picture of gaseous and solid pollutants (i.e. including also SO2, NOx CO, and organic residuals) as a function of the operating conditions of the fluidized bed combustor.
$655
$656
J. SMOLiKet al.
METHODOLOGY AND EXPERIMENTAL FACILITIES Extensive experimental measurements will be carried out on two high temperature, fluidized bed reactors: a small-scale, electrically heated 8.5 cm inside diameter reactor and a large-scale, rectangular 30cmx30cmx450cm reactor with supplementary gas bumer (Hartman et al., 1991,1993).Both reactors are equipped with all needed feeding systems, measuring and control peripherals. The spatial temperature profiles can be accurately monitored within the whole expanded bed as well as through the freeboard of the pilot-plant burner. Tha gas sampling system allows determination of oxygen (Magnos 4G), carbon monoxide (Uras 10 P), carbon dioxide (Infralyt 5), NO x (Model 951 A-Beckman), and sulphur dioxide (Infralyt 4). Samples of fine particulate matter remaining in flue gas leaving the separation equipment will be taken according to the Czech Republic standards by means of heated isokinetic probe. Stack particulates will be fractionated and collected using Berner-type low pressure impactor Hauke 25/015. The differential size distributions in submicron range will be also measured by EAA, TSI model 3030 with hot stack gases cooled and diluted below the dew point by Aerosol Diluter. In the experiments both chemical and structural analysis of fuel, bottom ash, fly ash from separating units, and fly ash remaining in the flue gas will be carried out. Brown coal will be characterised by chemical and petrographic analysis according to the Czech Republic standards (S2~korov~i, 1994). It will include proximate analysis (content of water, ash, volatile matter, total content of sulphur, content of sulphate and pyritic sulphur, calorific value, composition and melting point of ash), ultimate analysis (C, H, N, S, and O content) and microscopical analysis (mean reflectance, maceral composition, microlithotype composition, size and morphology of mineral grains, elemental composition of mineral components and their distribution in coal samples). The characterisation will be accomplished with the use ofmicroscope-microphotometer USMP 30 Petro, Opton-Zeiss, SEM BS 301 Tesla, and electron microprobe JXA-50, Jeol. Elemental composition of materials to be fired, fly ash from separating devices and fractionated aerosol collected after separating units will be determined by INAA with facilities of Laboratory oflNNA of the Nuclear Physics Institute ( WWR-S type nuclear reactor, gamma-ray spectrometer). For the lead determination PIXE analyses will be performed on the device built up on the Van de Graaff accelerator of the same Institute (Ku~era et al., 1992).
REFERENCES Svoboda K., Hartman M. (1991) Formation of NO x at fluidized bed combustion of model mixtures of liquid organic compounds containing nitrogen, Fuel 70, 865. Hartman M., Tmka O. (1993) Reaction between calcium oxide and flue gas containing sulphur dioxide at lower temperatures, AIChE J. 39, 615. S~,korovh I. (1994) Petrological characteristics of Czech low rank coal, Proc.Int. Conf. Energy and Environment- Transitions in East Central Europe, Prague 1994. Kurera J., Obrusnik I., Sfftrkov~iB., ~antroch J. (1992) Use of instrumental neutron activation analysis in monitoring of atmospheric pollutants and quality assurance of the analyses. Proc.Int.Symp.IAEA on Applications of Isotopes and Radiation in Conservation of the Environment, Karlsruhe 1992.
ll~Dernalnon
EMISSION FLUXES OF HEAVY METALS FROM THE FLUIDIZED BED COMBUSTION OF FOSSIL FUELS (A project supported from 1995 by GA CR No 104/95/0653) J. SMOLIK, M. HARTMAN, I. S~KOROVA#, J. KUCERA## Institute of Chemical Process Fundamentals AS CR, Rozvojovfi 135, !65 02 Prague 6 #Institute of Rock Structure and Mechanics AS CR, V Hole~ovi~k~ich41, 182 09 Prague 8 ##Nuclear Physics Institute AS CR, 250 68 l~e~at Prague KEYWORDS Coal combustion,Combustion aerosols, Heavy metals emissions MOTIVATION The air pollution, especially exposure to high levels of particulates, is thought to be the most important external factor affecting human health. The damage caused by toxic elements, attached to the airborne particulate matter is highly exacerbated by relatively high ambient level of sulphur dioxide and other gases. In the Czech Republic about 70% of solid emissions (about 350 kt in 1992) released into the atmosphere originate from low rank coal and lignite fired in power and heating plants and households. This coal is produced mainly in Most and Sokolov Basins (about 75 Mt in 1994). With eleven thermal power plants (four of them with output above 500 MW) belongs this region to so called "Black Triangle". In 1992 25% particulate pollutants, 46% of SO2 and 31% of NOx emissions in the Czech Republic were produced in this area. The project "Emission Fluxes of Heavy Metals in the Fluidized Bed Combustion of Fossil Fuels" is aimed at a fundamental understanding of the process when a metals containing fuel is introduced into a fluidized bed combustor equipped with standard, effluent gas cleaning facilities such as cyclones, barrier filters and wet scrubbing. To asses the potential environmental and toxic effects of metal species, a detailed physical and chemical charecteristic of suspended particulate matter will be established (size, shape, chemical composition). While the primary objective of the project is to provide a fundamental understanding of the intricate phenomena involved, it is also the authors ambition to contribute to the amelioration of the damaged environment of the Czech Republic. For this purpose the measurements will be carried out with samples of brown coal from North Bohemian Brown Coal Mining Area (Most and Sokolov Basins) which are mostly used in the Czech Republic.
•
•
•
• • •
GOALS OF THE PROJECT To explore quantitatively the division of hazardous metals (e.g. arsenic, cadmium, chromium, cooper, lead, mercury, zinc) between different emissinon streams (bottom bed ash, fly ash captured in cyclones, fly ash from wet scrubbing, ultrafine solids remaining in flue gas) when brown coal originated from different open-pit mines are fired. To examine the size and composition distributions of particulate matter emisions at different stages of the overall combustion process: above the bed, at the top ofa combustor, at the inlet and outlet of the cyclone, and in the stack flue gas. To evaluate the influence of the operating conditions of the fluidized bed combustor on the formation and release of metals emissions: bed temperature, residence time of solids and gas, concentration of oxygen. To investigate physical and chemical interactions between the metals species and the bed material" ash, ceramsite, additions od silica sand and limestone. To find a relationship between the mineral matrix of coal and the release of metals. To examine the overall picture of gaseous and solid pollutants (i.e. including also SO2, NOx CO, and organic residuals) as a function of the operating conditions of the fluidized bed combustor.
$655
$656
J. SMOLiKet al.
METHODOLOGY AND EXPERIMENTAL FACILITIES Extensive experimental measurements will be carried out on two high temperature, fluidized bed reactors: a small-scale, electrically heated 8.5 cm inside diameter reactor and a large-scale, rectangular 30cmx30cmx450cm reactor with supplementary gas bumer (Hartman et al., 1991,1993).Both reactors are equipped with all needed feeding systems, measuring and control peripherals. The spatial temperature profiles can be accurately monitored within the whole expanded bed as well as through the freeboard of the pilot-plant burner. Tha gas sampling system allows determination of oxygen (Magnos 4G), carbon monoxide (Uras 10 P), carbon dioxide (Infralyt 5), NO x (Model 951 A-Beckman), and sulphur dioxide (Infralyt 4). Samples of fine particulate matter remaining in flue gas leaving the separation equipment will be taken according to the Czech Republic standards by means of heated isokinetic probe. Stack particulates will be fractionated and collected using Berner-type low pressure impactor Hauke 25/015. The differential size distributions in submicron range will be also measured by EAA, TSI model 3030 with hot stack gases cooled and diluted below the dew point by Aerosol Diluter. In the experiments both chemical and structural analysis of fuel, bottom ash, fly ash from separating units, and fly ash remaining in the flue gas will be carried out. Brown coal will be characterised by chemical and petrographic analysis according to the Czech Republic standards (S2~korov~i, 1994). It will include proximate analysis (content of water, ash, volatile matter, total content of sulphur, content of sulphate and pyritic sulphur, calorific value, composition and melting point of ash), ultimate analysis (C, H, N, S, and O content) and microscopical analysis (mean reflectance, maceral composition, microlithotype composition, size and morphology of mineral grains, elemental composition of mineral components and their distribution in coal samples). The characterisation will be accomplished with the use ofmicroscope-microphotometer USMP 30 Petro, Opton-Zeiss, SEM BS 301 Tesla, and electron microprobe JXA-50, Jeol. Elemental composition of materials to be fired, fly ash from separating devices and fractionated aerosol collected after separating units will be determined by INAA with facilities of Laboratory oflNNA of the Nuclear Physics Institute ( WWR-S type nuclear reactor, gamma-ray spectrometer). For the lead determination PIXE analyses will be performed on the device built up on the Van de Graaff accelerator of the same Institute (Ku~era et al., 1992).
REFERENCES Svoboda K., Hartman M. (1991) Formation of NO x at fluidized bed combustion of model mixtures of liquid organic compounds containing nitrogen, Fuel 70, 865. Hartman M., Tmka O. (1993) Reaction between calcium oxide and flue gas containing sulphur dioxide at lower temperatures, AIChE J. 39, 615. S~,korovh I. (1994) Petrological characteristics of Czech low rank coal, Proc.Int. Conf. Energy and Environment- Transitions in East Central Europe, Prague 1994. Kurera J., Obrusnik I., Sfftrkov~iB., ~antroch J. (1992) Use of instrumental neutron activation analysis in monitoring of atmospheric pollutants and quality assurance of the analyses. Proc.Int.Symp.IAEA on Applications of Isotopes and Radiation in Conservation of the Environment, Karlsruhe 1992.