- Email: [email protected]
01060 Coal characterisation for NOx prediction in airstaged combustion of pulverised coals
01 Solid fuels (sources, winning, properties)
O1
SOLID F U E L S Sources, winning, properties
06•01059 Chemical fractionation tests on South African coal sources to obtain species-specific information on ash fusion temperatures (AFT) van Dyk, J. C. et al. Fuel, 2005, 84, (14 15), 1768 1777. Coals from the different sources used by Sasol vary substantially in terms of chemical and physical properties, and this directly relates to gasifier behaviour. Due to the large variation in coal properties from various sources, detailed coal and feedstock characteristics are essential to predict gasification performance when a specific coal source is to be gasified. One property that specifically gives detailed information on the suitability of a coal source for gasification purposes is the ash fusion temperature (AFT). The AFT of a coal source indicates the extent to which ash agglomeration and ash clinkering are likely to occur within the gasifier. Ash clinkering inside the gasifier can cause channel burning, pressure drop problems and unstable gasifier operation. The principle aim of this paper is to obtain mineral speciesspecific information on ash properties and the specific effect on AFT. Chemical fractionation treatment resulted in coals having different mineral properties that can be used to explain the effect of specific minerals on the AFT of coal. The highest concentration and species of minerals were removed from the coal by acid leaching (HC1 and HNO3) where A1, Ca, Mg, Na and Fe were removed in high concentrations from the coal. An interesting finding in the ash composition of the coal after leaching was that the SO3 concentration decreased from >2 mass % in the original coal sources to <0.3 mass % after the acid leaching. The AFT of coal after leaching increased to >1600°C. Based on the 95% confidence intervals depicted, the following components can be highlighted as having a statistically significant effect on the AFT: A1203, Fe203, CaO, MgO, P2Os and SiO2 A1203 combination. When mineral ratio was used, the best correlation coefficient (R) with AFT was obtained with the dolomite ratio. This is in agreement with the results obtained from the correlations between the AFT and the ash composition where CaO and MgO resulted in the best correlation with AFT. Although the correlation (R) of 0.81 is fairly similar to that of the individual correlations with CaO and MgO, the dolomite ratio also includes Fe, Na and K, which can have mineral interaction with the Ca and Mg and thus may be included in the ratio. Results presented in this paper again highlighted the fact and confirmed work from other researchers that ash composition (elemental analyses) on its own does not explain AFT behaviour or commercial performance of coal accurately.
06•01060 Coal characterisation for NOx prediction in airstaged combustion of pulverised coals Man, C. K. et al. Fuel, 2005, 84, (17), 2190 2195. A series of world-traded coal samples has been tested using the Imperial College high temperature wire mesh apparatus (HTWM) in order to assess the relationship between high temperature (1600°C) char nitrogen content and NOx formation in Hemweg Power Station (in the Netherlands) using deep furnace air staging. A linear relationship between high temperature char nitrogen and NOx formation has been confirmed. These results suggest that high temperature char N content is the main factor limiting NOx emissions with deep air-staged combustion. Char N and (hence apparently deep air-staged NO~) can be predicted with an accuracy of approximately ±20% for most coals from the coal proximate and ultimate analysis but this might not be sufficient for stations operating close to their emission limits. Measuring high temperature char N directly reduces the likely uncertainty in deep air-staged NOx emissions for coals (and most blends) to approximately ±10%. Its use should be considered on a routine basis for coal selection on plants employing this technology.
06•01061 Coalification analysis as a tool for regional geology in the Northern Eifel (Rhenish Massif, Germany Ribbert, K.-H. and Vieth, A. International Journal o f Coal Geology, 2005, 62, (1 2), 61 70. This study is a compilation of regional coalification work which was done in association with geological mapping in the northern part of the Eifel mountains (Devonian, Western Germany). The results are documented and interpreted by using different kinds of twodimensional presentations: (1) a lateral coalification map, (2) a vertical coalification/stratigraphical height diagram (pseudoborehole), (3) a model cross-section explaining isochronous deviations in coalification. The map shows the highest level of coalification is not restricted to the oldest Palaeozoic strata but includes some sections of Lower Devonian age. The lines of equal coalification cross-geological strata lines that
162
Fuel and Energy Abstracts
May 2006
means there is a component of coalification not conformable with simple burial influence. With the help of a pseudoborehole diagram the areal gradient development in different stages of rank is discussed as well as local rapid coalification changes. In a cross-section from the Eifel North South Zone to the flank of the Venn Anticline, the burial and coalification development is explained by a hypothetical Eifelian sedimentation trough, which marks the time of maximal burial of Lower Devonian strata. Petrophysical influences on coalification of pelitic sediments and the age of coalification are discussed.
06•01062 Geochemistry, petrology, and palynology of the Pond Creek coal bed, northern Pike and southern Martin counties, Kentucky Hower, J. C. et al. International Journal q f Coal Geology, 2005, 62, (3), 167 181. The geochemistry, petrology, and palynology of the Duckmantian-age Pond Creek coal bed were investigated in northern Pike and southern Martin counties, eastern Kentucky. The coal bed exhibits significant vertical variation in the investigated geochemical parameters, with many diagenetic overprints of the original geochemistry. Included in the range of geochemical signatures are the presence of elements, particularly TiO2 and Zr, suggesting the detrital influences at the time of deposition of a low-vitrinite durain; a high CaO zone with elevated B/Be, both suggesting marine influence, in a lithotype in the middle of the coal bed; and the postdepositional emplacement of pyrite in the uppermost lithotype. Individual lithotypes, each representing distinct depositional environments, all complicated to some degree by diagentic overprints, comprise the complex history of the coal bed.
06•01063 Ignition behaviour of different rank coals in an entrained flow reactor Fatindez, J. et al. Fuel, 2005, 84, (17), 2172 2177. An experimental study to determine the temperature and mechanism of coal ignition was carried out by using an entrained flow reactor (EFR) at relatively high coal feed rates (0.5 g min 1). Seven coals ranging in rank from subbituminous to semianthracite, were tested and the evolved gases (O2, CO, CO2, NO) were measured continuously. The ignition temperature was evaluated from the gas evolution profiles, and it was found to be inversely correlated to the reactivity of the coal, as reflected by the increasing values of the ignition temperature in the sequence: subbituminous, high volatile bituminous, low volatile bituminous and semianthracite coals. The mechanism of ignition varied from a heterogeneous mechanism for subbituminous, low volatile bituminous and semianthracite coals, to a homogeneous mechanism for high volatile bituminous coals. A thermogravimetric analyser (TGA) was also used to evaluate coal ignition behaviour. Both methods, TGA and EFR, were in agreement as regards the mechanism of coal ignition. From the SEM micrographs of the coal particles retrieved from the cyclone, it was possible to observe the external appearance of the particles before, during and after ignition. The micrographs confirmed the mechanism deduced from the gas profiles.
06•01064 Influence of petrographical composition on coal flotability Fecko, P. et al. Fuel, 2005, 84, (14 15), 1901 1904. The paper deals with flotability of bituminous coal and examines how individual maceral groups float in the course of a fractional flotation test. Eight samples of bituminous coal from the localities of Jaworzno, Staszicz, Marcel (Poland), three samples from the Dukla Mine, CSA, CSM (Czech Republic) and two samples from Brut Petrosani and Brut Paroseli Mines in Romania were tested by flotation. The objective of this paper was to evaluate the flotation characteristics of bituminous coal from localities in Poland, the Czech Republic and Romania; using Montanol and Flotalex collector agents. The performance of these collector agents was tested and the results evaluated from the petrologic analyses.
06•01065 Molecular indicators for coal-forming vegetation of the Miocene Chukurovo lignite, Bulgaria Stefanova, M. et al. Fuel, 2005, 84, (14 15), 1830 1838. The main coal forming element in the peat paleoswamp of the Middle Miocene 'Chukurovo' lignite is Taxodiaceae (paleobotanical observation). The great preponderance of diterpenoids in the resinite is a chemical confirmation for the presence of coniferous vegetation in the paleoplant taxa. Subordinate quantities of the sesquiterpenoids cuparene, valencene and cadalene types and longifolane are present. Molecular indicators for angiosperm vegetation are also recognized in the bulk coal. The presence of olean-12-ene, urs-12-ene, 24,25dinoroleana-l,3,5(10)12-tetraene, and 24,25-dinorursa-l,3,5(10)12-tetraene all indicate flowering trees and provide the possibility to further assess the paleoplant community. The triterpenoid data indicate oxic diagenetic transformation of plant detritus had proceeded by aromatization of ring A E.
O1
SOLID F U E L S Sources, winning, properties
06•01059 Chemical fractionation tests on South African coal sources to obtain species-specific information on ash fusion temperatures (AFT) van Dyk, J. C. et al. Fuel, 2005, 84, (14 15), 1768 1777. Coals from the different sources used by Sasol vary substantially in terms of chemical and physical properties, and this directly relates to gasifier behaviour. Due to the large variation in coal properties from various sources, detailed coal and feedstock characteristics are essential to predict gasification performance when a specific coal source is to be gasified. One property that specifically gives detailed information on the suitability of a coal source for gasification purposes is the ash fusion temperature (AFT). The AFT of a coal source indicates the extent to which ash agglomeration and ash clinkering are likely to occur within the gasifier. Ash clinkering inside the gasifier can cause channel burning, pressure drop problems and unstable gasifier operation. The principle aim of this paper is to obtain mineral speciesspecific information on ash properties and the specific effect on AFT. Chemical fractionation treatment resulted in coals having different mineral properties that can be used to explain the effect of specific minerals on the AFT of coal. The highest concentration and species of minerals were removed from the coal by acid leaching (HC1 and HNO3) where A1, Ca, Mg, Na and Fe were removed in high concentrations from the coal. An interesting finding in the ash composition of the coal after leaching was that the SO3 concentration decreased from >2 mass % in the original coal sources to <0.3 mass % after the acid leaching. The AFT of coal after leaching increased to >1600°C. Based on the 95% confidence intervals depicted, the following components can be highlighted as having a statistically significant effect on the AFT: A1203, Fe203, CaO, MgO, P2Os and SiO2 A1203 combination. When mineral ratio was used, the best correlation coefficient (R) with AFT was obtained with the dolomite ratio. This is in agreement with the results obtained from the correlations between the AFT and the ash composition where CaO and MgO resulted in the best correlation with AFT. Although the correlation (R) of 0.81 is fairly similar to that of the individual correlations with CaO and MgO, the dolomite ratio also includes Fe, Na and K, which can have mineral interaction with the Ca and Mg and thus may be included in the ratio. Results presented in this paper again highlighted the fact and confirmed work from other researchers that ash composition (elemental analyses) on its own does not explain AFT behaviour or commercial performance of coal accurately.
06•01060 Coal characterisation for NOx prediction in airstaged combustion of pulverised coals Man, C. K. et al. Fuel, 2005, 84, (17), 2190 2195. A series of world-traded coal samples has been tested using the Imperial College high temperature wire mesh apparatus (HTWM) in order to assess the relationship between high temperature (1600°C) char nitrogen content and NOx formation in Hemweg Power Station (in the Netherlands) using deep furnace air staging. A linear relationship between high temperature char nitrogen and NOx formation has been confirmed. These results suggest that high temperature char N content is the main factor limiting NOx emissions with deep air-staged combustion. Char N and (hence apparently deep air-staged NO~) can be predicted with an accuracy of approximately ±20% for most coals from the coal proximate and ultimate analysis but this might not be sufficient for stations operating close to their emission limits. Measuring high temperature char N directly reduces the likely uncertainty in deep air-staged NOx emissions for coals (and most blends) to approximately ±10%. Its use should be considered on a routine basis for coal selection on plants employing this technology.
06•01061 Coalification analysis as a tool for regional geology in the Northern Eifel (Rhenish Massif, Germany Ribbert, K.-H. and Vieth, A. International Journal o f Coal Geology, 2005, 62, (1 2), 61 70. This study is a compilation of regional coalification work which was done in association with geological mapping in the northern part of the Eifel mountains (Devonian, Western Germany). The results are documented and interpreted by using different kinds of twodimensional presentations: (1) a lateral coalification map, (2) a vertical coalification/stratigraphical height diagram (pseudoborehole), (3) a model cross-section explaining isochronous deviations in coalification. The map shows the highest level of coalification is not restricted to the oldest Palaeozoic strata but includes some sections of Lower Devonian age. The lines of equal coalification cross-geological strata lines that
162
Fuel and Energy Abstracts
May 2006
means there is a component of coalification not conformable with simple burial influence. With the help of a pseudoborehole diagram the areal gradient development in different stages of rank is discussed as well as local rapid coalification changes. In a cross-section from the Eifel North South Zone to the flank of the Venn Anticline, the burial and coalification development is explained by a hypothetical Eifelian sedimentation trough, which marks the time of maximal burial of Lower Devonian strata. Petrophysical influences on coalification of pelitic sediments and the age of coalification are discussed.
06•01062 Geochemistry, petrology, and palynology of the Pond Creek coal bed, northern Pike and southern Martin counties, Kentucky Hower, J. C. et al. International Journal q f Coal Geology, 2005, 62, (3), 167 181. The geochemistry, petrology, and palynology of the Duckmantian-age Pond Creek coal bed were investigated in northern Pike and southern Martin counties, eastern Kentucky. The coal bed exhibits significant vertical variation in the investigated geochemical parameters, with many diagenetic overprints of the original geochemistry. Included in the range of geochemical signatures are the presence of elements, particularly TiO2 and Zr, suggesting the detrital influences at the time of deposition of a low-vitrinite durain; a high CaO zone with elevated B/Be, both suggesting marine influence, in a lithotype in the middle of the coal bed; and the postdepositional emplacement of pyrite in the uppermost lithotype. Individual lithotypes, each representing distinct depositional environments, all complicated to some degree by diagentic overprints, comprise the complex history of the coal bed.
06•01063 Ignition behaviour of different rank coals in an entrained flow reactor Fatindez, J. et al. Fuel, 2005, 84, (17), 2172 2177. An experimental study to determine the temperature and mechanism of coal ignition was carried out by using an entrained flow reactor (EFR) at relatively high coal feed rates (0.5 g min 1). Seven coals ranging in rank from subbituminous to semianthracite, were tested and the evolved gases (O2, CO, CO2, NO) were measured continuously. The ignition temperature was evaluated from the gas evolution profiles, and it was found to be inversely correlated to the reactivity of the coal, as reflected by the increasing values of the ignition temperature in the sequence: subbituminous, high volatile bituminous, low volatile bituminous and semianthracite coals. The mechanism of ignition varied from a heterogeneous mechanism for subbituminous, low volatile bituminous and semianthracite coals, to a homogeneous mechanism for high volatile bituminous coals. A thermogravimetric analyser (TGA) was also used to evaluate coal ignition behaviour. Both methods, TGA and EFR, were in agreement as regards the mechanism of coal ignition. From the SEM micrographs of the coal particles retrieved from the cyclone, it was possible to observe the external appearance of the particles before, during and after ignition. The micrographs confirmed the mechanism deduced from the gas profiles.
06•01064 Influence of petrographical composition on coal flotability Fecko, P. et al. Fuel, 2005, 84, (14 15), 1901 1904. The paper deals with flotability of bituminous coal and examines how individual maceral groups float in the course of a fractional flotation test. Eight samples of bituminous coal from the localities of Jaworzno, Staszicz, Marcel (Poland), three samples from the Dukla Mine, CSA, CSM (Czech Republic) and two samples from Brut Petrosani and Brut Paroseli Mines in Romania were tested by flotation. The objective of this paper was to evaluate the flotation characteristics of bituminous coal from localities in Poland, the Czech Republic and Romania; using Montanol and Flotalex collector agents. The performance of these collector agents was tested and the results evaluated from the petrologic analyses.
06•01065 Molecular indicators for coal-forming vegetation of the Miocene Chukurovo lignite, Bulgaria Stefanova, M. et al. Fuel, 2005, 84, (14 15), 1830 1838. The main coal forming element in the peat paleoswamp of the Middle Miocene 'Chukurovo' lignite is Taxodiaceae (paleobotanical observation). The great preponderance of diterpenoids in the resinite is a chemical confirmation for the presence of coniferous vegetation in the paleoplant taxa. Subordinate quantities of the sesquiterpenoids cuparene, valencene and cadalene types and longifolane are present. Molecular indicators for angiosperm vegetation are also recognized in the bulk coal. The presence of olean-12-ene, urs-12-ene, 24,25dinoroleana-l,3,5(10)12-tetraene, and 24,25-dinorursa-l,3,5(10)12-tetraene all indicate flowering trees and provide the possibility to further assess the paleoplant community. The triterpenoid data indicate oxic diagenetic transformation of plant detritus had proceeded by aromatization of ring A E.