- Email: [email protected]
N2O emissions from coal combustion
N29
lys~s of the relatlonshrp between lobs and emrssions In Vol 27, No 5, of Env SCI Technol HISanalysis IS based on the 1989 TOXICSRelease Inventory in the USA which contains reports of 328 toxic chemical discharged to air, land and water n the USA in 1989 Emissions per job were lowest in New Jersey (129 pounds per job) and California (247) and highest in Alabama (5985) and Louisiana (14,198) The author concludes that there was a relationship between the qualrty ofa state’s environmental policies and the emissions to lobs ratio In an interesting analysis of emissions for all chemical sectors in the USA the article showsthat industrial inorganic, agncultural chemicals, nrtrogenous fertilizer, phosphatrc fertilizer and carbon black production were the sectors which gave the highest emission to lobs ratios An article in Vol 27, No 7 of Env SCI Technol describes that NOx emissions from coal-fired power plants can be curtailed to below 150 ppm by the TFS 2009 system, developed by Asea Brown Boven (ABB, Stamford, CT) It IS based on new methods of pulverizing and injecting the coal into a staged air-frnng system The objective ISto reduce the formation of pollutants dunng the combustion process rather than after burning NOx IS reduced through careful control of the fuel-air mrxture The article also announces the ABB EV Burner for gas-fired borlers, which could cut NOx emissions to below 15 ppm A mixture of gas, air, and recirculated exhaust gases keeps the flame cool enough to rnhrbrt NOx production
N20 Emissions from Coal Combustion
N20 has been attracting attention because of rts contribution to both the greenhouse effect and ozone layer depletion applied catalysis B environmental
The June issue of the Fuel Process Technol (34 (1) (1993) 1-71) contains an extenswe review, pubkshed by M A Wojtowaz, J R Pels and J A Moulijn, on vanous aspects of Na produced during coal combustion The review, wrth more than 299 references, represents the state of the art on the topic The global mass balance of N20 IS compared wrth the other greenhouse gases A link IS also made between N20 emission and existrng NOx and SO, measures It IS noted that N20 levels have been steadily increasing at about 0 3% per year The environmental concerns are raised because of a very long lrfetrme and strong radlatlve forcing of N20 N20 production during fluid bed combustion (FBC) IS an order of magnrtude greaterthan in conventional boilers Before N20 was recognized as the environmental pollutant, the FBC was vtewed as a successfull approach to combat problems wrth NOx and SOX emissions At relatrvely low temperatures, such as in FBC, HCN IS a precursor of N20 formation in the gas phase, whereas at high temperatures NO IS formed preferentially from HCN This constltutes the essence of the NO-versusN20 trade-off observed experimentally Thus, the sum of N20 and NO in FBC appears to be constant It IS assumed that during F&C, the only contnbutron to final NOx/N20 emissions comes from fuelbound nrtrogen The fate of nrtrogen during pyrolysis and combustion as well as mechanisms of NOx/N20 formation and destruction are discussed, including the role of HCN and NH3 in the overall mechanism Several heterogeneous routes are proposed to describe competttive emsslons of N20 and NOx So2, rf present, rnhrbrts NOx formation Then, coal desulphunzation may lead to increased NOx emrssrons A summary of kinetic parame-
Volume 2 No 4 -
15 September 1993
N30
ters of all relevant reactions 1.salso given Equlllbnum calculattons, based on total Gibbs energy mmlmization, are used to discuss reacttons occurnng In the gas phase Most of the NzO IS formed in heterogeneous reactions, involving char and/or coal bound nitrogen Group VIII transition metal oxldes are active as catalysts for N20 decomposltlon CaO IS also very active This IS Important when limestone IS injected Into FBC However, in the presence of llmestone decreased N20 emissions were accompanied by increased NO formation In the presence of CaSO4, the N20 formation accompanied NO reduction Combmed effects of Son, CaO and CaS0.j on N20 formation and/or decomposltlon dunng FBC combustion deserve some additional attention Also, information on the effect of coal’s mineral matter on N20/NOx emissions IS still rather limited Besides temperature, which IS the most important parameter, other parameters also influence N20 formation Coal-nl-
trogen, conversion to N20 Increases with coal rank In this regard, pyndlnlc nitrogen in coal may play an important role It appears that air staging may decrease N20 formation The use of addltlves, such as NH3, urea and cyanunc acid to control N20 emissions was also investigated No one-sided approach to N20 abatement IS likely to be successful due to a number of emission trade-offs between N20 and NO levels Emissions can be decreased through improvements In operating condttions and lnnovatlve combustor design Also, emissions of one pollutant can be sacrrflced for the sake of other pollutants while adopting special measures to reduce excessive levels ofthe selected pollutant It IS judged that successful N20/NOx abatement measures may include gas afterburning, use of catalytic adddtves to enhance N20 decomposition and an aftertreatment of flue gas at lower temperatures ED FURIMSKY
Calendar of Forthcoming Events (For detailed information on the crted events, please refer to the Applied Catalysis issue mentioned wfih the entry ) 17-21 Ott 1993 St Petersburg, Russia
*Symposium on Ceramic Materials, Including In the Automobile Part of 4th European East-West Conference and Exhibition on Materials and Processes Contact A G Romashm, Technologlya, 15 ffiev Chaussee, 240920 City of Obnmsk (Kaluga), Russia, (+7-095) 5463915, fax (+7-8439) 2552225 or R J Brook, Unlv of Oxford, Dept of Materials,, Parks Road, Oxford OX1 3PH, UK, (+44-865) 273782, fax (+ 44-855) 273789
17-19 Ott 1993 Redwood Qty, CA, USA
10th Anniversary Advances in Catalytic Technology (ACT) Seminar Contact J Naworskl, CatalytIca Studies Dlwslon, 430 Ferguson Drive, Mountam View, CA 94043-5272, (+ l-415)9406300, fax (+ l415)9587129
applied catalysis 8. environmental
Volume 2 No 4 -
15 September 1993
lys~s of the relatlonshrp between lobs and emrssions In Vol 27, No 5, of Env SCI Technol HISanalysis IS based on the 1989 TOXICSRelease Inventory in the USA which contains reports of 328 toxic chemical discharged to air, land and water n the USA in 1989 Emissions per job were lowest in New Jersey (129 pounds per job) and California (247) and highest in Alabama (5985) and Louisiana (14,198) The author concludes that there was a relationship between the qualrty ofa state’s environmental policies and the emissions to lobs ratio In an interesting analysis of emissions for all chemical sectors in the USA the article showsthat industrial inorganic, agncultural chemicals, nrtrogenous fertilizer, phosphatrc fertilizer and carbon black production were the sectors which gave the highest emission to lobs ratios An article in Vol 27, No 7 of Env SCI Technol describes that NOx emissions from coal-fired power plants can be curtailed to below 150 ppm by the TFS 2009 system, developed by Asea Brown Boven (ABB, Stamford, CT) It IS based on new methods of pulverizing and injecting the coal into a staged air-frnng system The objective ISto reduce the formation of pollutants dunng the combustion process rather than after burning NOx IS reduced through careful control of the fuel-air mrxture The article also announces the ABB EV Burner for gas-fired borlers, which could cut NOx emissions to below 15 ppm A mixture of gas, air, and recirculated exhaust gases keeps the flame cool enough to rnhrbrt NOx production
N20 Emissions from Coal Combustion
N20 has been attracting attention because of rts contribution to both the greenhouse effect and ozone layer depletion applied catalysis B environmental
The June issue of the Fuel Process Technol (34 (1) (1993) 1-71) contains an extenswe review, pubkshed by M A Wojtowaz, J R Pels and J A Moulijn, on vanous aspects of Na produced during coal combustion The review, wrth more than 299 references, represents the state of the art on the topic The global mass balance of N20 IS compared wrth the other greenhouse gases A link IS also made between N20 emission and existrng NOx and SO, measures It IS noted that N20 levels have been steadily increasing at about 0 3% per year The environmental concerns are raised because of a very long lrfetrme and strong radlatlve forcing of N20 N20 production during fluid bed combustion (FBC) IS an order of magnrtude greaterthan in conventional boilers Before N20 was recognized as the environmental pollutant, the FBC was vtewed as a successfull approach to combat problems wrth NOx and SOX emissions At relatrvely low temperatures, such as in FBC, HCN IS a precursor of N20 formation in the gas phase, whereas at high temperatures NO IS formed preferentially from HCN This constltutes the essence of the NO-versusN20 trade-off observed experimentally Thus, the sum of N20 and NO in FBC appears to be constant It IS assumed that during F&C, the only contnbutron to final NOx/N20 emissions comes from fuelbound nrtrogen The fate of nrtrogen during pyrolysis and combustion as well as mechanisms of NOx/N20 formation and destruction are discussed, including the role of HCN and NH3 in the overall mechanism Several heterogeneous routes are proposed to describe competttive emsslons of N20 and NOx So2, rf present, rnhrbrts NOx formation Then, coal desulphunzation may lead to increased NOx emrssrons A summary of kinetic parame-
Volume 2 No 4 -
15 September 1993
N30
ters of all relevant reactions 1.salso given Equlllbnum calculattons, based on total Gibbs energy mmlmization, are used to discuss reacttons occurnng In the gas phase Most of the NzO IS formed in heterogeneous reactions, involving char and/or coal bound nitrogen Group VIII transition metal oxldes are active as catalysts for N20 decomposltlon CaO IS also very active This IS Important when limestone IS injected Into FBC However, in the presence of llmestone decreased N20 emissions were accompanied by increased NO formation In the presence of CaSO4, the N20 formation accompanied NO reduction Combmed effects of Son, CaO and CaS0.j on N20 formation and/or decomposltlon dunng FBC combustion deserve some additional attention Also, information on the effect of coal’s mineral matter on N20/NOx emissions IS still rather limited Besides temperature, which IS the most important parameter, other parameters also influence N20 formation Coal-nl-
trogen, conversion to N20 Increases with coal rank In this regard, pyndlnlc nitrogen in coal may play an important role It appears that air staging may decrease N20 formation The use of addltlves, such as NH3, urea and cyanunc acid to control N20 emissions was also investigated No one-sided approach to N20 abatement IS likely to be successful due to a number of emission trade-offs between N20 and NO levels Emissions can be decreased through improvements In operating condttions and lnnovatlve combustor design Also, emissions of one pollutant can be sacrrflced for the sake of other pollutants while adopting special measures to reduce excessive levels ofthe selected pollutant It IS judged that successful N20/NOx abatement measures may include gas afterburning, use of catalytic adddtves to enhance N20 decomposition and an aftertreatment of flue gas at lower temperatures ED FURIMSKY
Calendar of Forthcoming Events (For detailed information on the crted events, please refer to the Applied Catalysis issue mentioned wfih the entry ) 17-21 Ott 1993 St Petersburg, Russia
*Symposium on Ceramic Materials, Including In the Automobile Part of 4th European East-West Conference and Exhibition on Materials and Processes Contact A G Romashm, Technologlya, 15 ffiev Chaussee, 240920 City of Obnmsk (Kaluga), Russia, (+7-095) 5463915, fax (+7-8439) 2552225 or R J Brook, Unlv of Oxford, Dept of Materials,, Parks Road, Oxford OX1 3PH, UK, (+44-865) 273782, fax (+ 44-855) 273789
17-19 Ott 1993 Redwood Qty, CA, USA
10th Anniversary Advances in Catalytic Technology (ACT) Seminar Contact J Naworskl, CatalytIca Studies Dlwslon, 430 Ferguson Drive, Mountam View, CA 94043-5272, (+ l-415)9406300, fax (+ l415)9587129
applied catalysis 8. environmental
Volume 2 No 4 -
15 September 1993