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Performance improvement of integrated coal gasification combined cycle by a new approach in exergy analysis
04 By-products
related to fuels
designed bench-scale apparatus. Mercury removal was shown to be due to a reaction with the carbonaceous dust from the gasifier; the dust had substantial capacity for mercury capture at temperatures below 200°C. the effect of the dust in modifying the bulk thermodynamic properties of the hot gas filter system composition is attributed to chemisorption of HgS. The capacity of the dust for mercury capture was observed to be much greater in the laboratory-scale reactor than in the hot gas filter of the pilot plant. This observation is believed to be due to the main mechanism of dust collection by the filter being gravity separation directly to the hopper, rather than deposition as a filter cake.
Design for a mixer in the coal bed gas at a low concentration dynamo engine 02/00881
Zhang, X. e/ crl. Meilun Z/mcm/~ucr, 2001, 24, (I), 40-43. (In Chinese) This paper puts emphasis on the design, characteristics and principle of a new mixer for use with coal-bed-gas-fired electricity generators. Compared with an old mixer, the new mixer can not only meet the demand of varying densities of fuel, but also reduce fuel consumption rate.
02lOO882 Performance improvement of integrated coal gasification combined cycle by a new approach in exergy analysis Kim, J.J. er al. Korean J. C/tern. Eng., 2001, 18, (I), 94-l 00. A new approach to exergy analysis is proposed for examining the consumption of energy as the minimum driving force and of exergy consumption that is avoidable, and for the development of a method to predict the alternatives in system improvement by exploring possible reduction in the avoidable exergy consumption. Also suggested in this study is a dimensionless parameter yAvo, which is the ratio of avoidable exergy consumption over total fuel energy input to the system. Detailed analyses, including the calculations of exergy consumption, exergy loss and avoidable exergy consumption, were conducted for each component in the syngas cooling system in the Integrated Coal Gasification Combined Cycle (IGCC) plant, to prove the effective application of the proposed method. The analysis showed that the rank of avoidable exergy consumption was different from that of total energy consumption, and hence it confirmed that an energy analysis by conventional methods misled the focus of improvement in system design. The methodology developed in this study offers a new approach for system designers to analyse and to improve the performance of a complex energy system such as an IGCC plant.
OZOO883 Temperature field model of two-stage underground coal gasification Yang, L. Huugong Xtrehuo (Chin. Ed.), 2001, 52, (3), 273-216. (In Chinese) Two-stage underground coal gasification is an effective method which can produce water gas with a high heating value, while the temperature is the key factor that determines its producing process. On the basis of model tests, the mathematical model for a two-dimensional, non-linear, unsteady temperature field is established through analysing the distribution law of the temperature field for combustion and gasification of coal seam in the stove, and outlining and treating the boundary conditions. A selection method of the model parameters has been introduced. The mathematical model is solved by the control volume method, and calculation results are analysed. The uniformity of calculations and real measurement value indicate that the numerical simulation of dynamic state temperature field for the coal seam medium in the gasification stove is correct. Thereby, it provides a necessarily theoretical base for further quantitative study on process of underground coal gasification.
Three-stage well-mixed reactor model for a pressurized coal gssifier
02/00884
Song, B.H. and Watkinson, A.P. Cun. J. Chem. Eng., 2000, 78, (I), 143155. Three Canadian coals of different rank were gasified with air-steam mixtures in a 0.1 m diameter spounted bed reactor at pressures to 292 kPa, average bed temperatures varying between 840 and 96O”C, and steam-to-coal feed ratios between 0.0 and 2.88. In order to analyse gasifier performance and correlate data, a three-stage model has been developed incorporating instantaneous devolatilization of coal, instantaneous combustion of carbon at the bottom of the bed, and steam/ carbon gasification and water gas shift reaction in a single well mixed isothermal stage. The capture of HzS by limestone sorbent injection is also treated. The effects of various assumptions and model parameters on the predictions were investigated. The present model indicates that gasifier performance is mainly controlled by the fast coal devolatilization and char combustion reactions, and the contribution to carbon conversion of the slow char gasification reactions is comparatively small. The incorporation of tar decomposition into the mode1 provides significantly closer predictions of experimental gas composition than is obtained otherwise.
108 Fuel and Energy Abstracts
March 2002
04
BY-PRODUCTS TO FUELS
RELATED
Abrasive cleansing and polishing material including fly ash
02/00885
Salem, M. Brit. UK Pat. Appl. CB 2,351,502 (Cl. CllD3114). 3 Jan 2001, GB Appl. 199918,762, 17 Apr 1999. 11. The material for abrasive cosmetics and cleansing products comprises a pulverized fuel ash and/or a cenosphere (glass oxide microsphere) as abrasive agent.
Activated carbon fibers and films derived from poly(vinylidene fluoride)
02/00886
Yamashita, J. el crl. Corhon, 2001, 39, (2) 207-214. Activated carbons having different ranges of pore sizes from those derived by the conventional heat-treatment of organic compounds have been produced by carrying out a part of the conversion process through a liquid phase chemical treatment. Poly(vinylidene fluoride) (PVDF) was chosen as a starting polymer by taking into account the processability of this polymer into various geometries. The PVDF fibres and films were converted to activated carbons by using the combination of chemical dehydrofluorination with a strong base, hightemperature heat-treatment and activation in a carbon dioxide gas. The resulting activated carbon film exhibited superior methylene blue adsorption of 538 mg g ‘. Formation of a rigid skeleton during dehydrofluorination accounted for the ability of dehydrofluorinated PVDF to maintain its macroscopic precursor geometry during hightemperature heat-treatment and the formation of pores with large sizes.
Anodic performance and insertion mechanism of hard carbons prepared from synthetic isotropic pitches
02lOO887
Mochida, I. L’Irr[_ Curbon, 2001, 39, (3). 399-410. Anodic performances and structures of hard carbons prepared from synthetic isotropic pitches through solid phase oxidation were investigated to discuss their insertion sites for lithium ion and correlation between the capacity and structure. The derived hard carbons showed complicated voltage profiles of charge and discharge, indicating five kinds of insertion sites; partially charge transferring surface site (Type I), intercalation site like graphite (Type II), cluster gap between edges of carbon hexagon clusters (Type III), microvoid surrounded by hexagonal planes (Type IV) and atomic defect created by evolution of heteroatom (Type V). Types I-III are common to those found in the soft carbon. Very unique capacities of the present hard carbons calcined at 1000°C were found at the potentials of O-O.13 V (Type IV) and 0.5-2.0 V (Type V) and varied markedly with oxidization extent and heteroatom contents of precursor pitch, respectively. The microvoid among the hexagonal planes and atomic defects created by evolution of heteroatom are suggested to serve such insertion sites of Types IV and V, respectively. The microvoid holds reduced lithium ions with different extents of charge transfer to the carbon, which exist independently at 140 K but exchange rapidly at room temperature to their averaged chemical shift in ‘Li-NMR. Type V showed very similar charge-discharge behaviours to that of Type III, which was found more in the soft carbon carbonized at around 700°C and decreased sharply by the heat-treatment at 1000°C due to the coupling of hexagon clusters. The amount of microvoid or capacity at O-O.13 V is correlated to XRD parameters and oxygen content of the precursors. Smaller crystal, lower stacking or more oxygen content in the precursor allows apparently larger capacity. Random assemble of smaller graphitic units may induce the microvoid among the cluster units, although the microvoid has not been specifically defined yet. 02/00888
Ash utilization in India: challenge for the new
millennium Dhar, T.K. Fly Ash Disposal Uril.. In/. Cm/.. Proc., 2nd, 2000, I, 2/l-2/ 9. Edited by Varma C.V.J. The alarming magnitude of the problem of ash waste production has recently attracted the attention of government officials, scientists, technologists and policy-makers. Ash products are superior to conventional building products and provide an excellent opportunity for sustainable development. Development of suitable technologies for the use of ash and ash-based products and also state-of-the-art equipment required for manufacturing ash-based products has emerged as the major challenge for India. Concerted efforts from all sectors are required to take up the challenge and move fly ash from waste product category to co-product category. The present scenario of ash utilization of India, its potential for the future, and the opportunities and challenges it provides, are discussed. Also, the problems and suggestions with regards to promoting ash utilization in general and the use of ash-based products in particular, are discussed.
related to fuels
designed bench-scale apparatus. Mercury removal was shown to be due to a reaction with the carbonaceous dust from the gasifier; the dust had substantial capacity for mercury capture at temperatures below 200°C. the effect of the dust in modifying the bulk thermodynamic properties of the hot gas filter system composition is attributed to chemisorption of HgS. The capacity of the dust for mercury capture was observed to be much greater in the laboratory-scale reactor than in the hot gas filter of the pilot plant. This observation is believed to be due to the main mechanism of dust collection by the filter being gravity separation directly to the hopper, rather than deposition as a filter cake.
Design for a mixer in the coal bed gas at a low concentration dynamo engine 02/00881
Zhang, X. e/ crl. Meilun Z/mcm/~ucr, 2001, 24, (I), 40-43. (In Chinese) This paper puts emphasis on the design, characteristics and principle of a new mixer for use with coal-bed-gas-fired electricity generators. Compared with an old mixer, the new mixer can not only meet the demand of varying densities of fuel, but also reduce fuel consumption rate.
02lOO882 Performance improvement of integrated coal gasification combined cycle by a new approach in exergy analysis Kim, J.J. er al. Korean J. C/tern. Eng., 2001, 18, (I), 94-l 00. A new approach to exergy analysis is proposed for examining the consumption of energy as the minimum driving force and of exergy consumption that is avoidable, and for the development of a method to predict the alternatives in system improvement by exploring possible reduction in the avoidable exergy consumption. Also suggested in this study is a dimensionless parameter yAvo, which is the ratio of avoidable exergy consumption over total fuel energy input to the system. Detailed analyses, including the calculations of exergy consumption, exergy loss and avoidable exergy consumption, were conducted for each component in the syngas cooling system in the Integrated Coal Gasification Combined Cycle (IGCC) plant, to prove the effective application of the proposed method. The analysis showed that the rank of avoidable exergy consumption was different from that of total energy consumption, and hence it confirmed that an energy analysis by conventional methods misled the focus of improvement in system design. The methodology developed in this study offers a new approach for system designers to analyse and to improve the performance of a complex energy system such as an IGCC plant.
OZOO883 Temperature field model of two-stage underground coal gasification Yang, L. Huugong Xtrehuo (Chin. Ed.), 2001, 52, (3), 273-216. (In Chinese) Two-stage underground coal gasification is an effective method which can produce water gas with a high heating value, while the temperature is the key factor that determines its producing process. On the basis of model tests, the mathematical model for a two-dimensional, non-linear, unsteady temperature field is established through analysing the distribution law of the temperature field for combustion and gasification of coal seam in the stove, and outlining and treating the boundary conditions. A selection method of the model parameters has been introduced. The mathematical model is solved by the control volume method, and calculation results are analysed. The uniformity of calculations and real measurement value indicate that the numerical simulation of dynamic state temperature field for the coal seam medium in the gasification stove is correct. Thereby, it provides a necessarily theoretical base for further quantitative study on process of underground coal gasification.
Three-stage well-mixed reactor model for a pressurized coal gssifier
02/00884
Song, B.H. and Watkinson, A.P. Cun. J. Chem. Eng., 2000, 78, (I), 143155. Three Canadian coals of different rank were gasified with air-steam mixtures in a 0.1 m diameter spounted bed reactor at pressures to 292 kPa, average bed temperatures varying between 840 and 96O”C, and steam-to-coal feed ratios between 0.0 and 2.88. In order to analyse gasifier performance and correlate data, a three-stage model has been developed incorporating instantaneous devolatilization of coal, instantaneous combustion of carbon at the bottom of the bed, and steam/ carbon gasification and water gas shift reaction in a single well mixed isothermal stage. The capture of HzS by limestone sorbent injection is also treated. The effects of various assumptions and model parameters on the predictions were investigated. The present model indicates that gasifier performance is mainly controlled by the fast coal devolatilization and char combustion reactions, and the contribution to carbon conversion of the slow char gasification reactions is comparatively small. The incorporation of tar decomposition into the mode1 provides significantly closer predictions of experimental gas composition than is obtained otherwise.
108 Fuel and Energy Abstracts
March 2002
04
BY-PRODUCTS TO FUELS
RELATED
Abrasive cleansing and polishing material including fly ash
02/00885
Salem, M. Brit. UK Pat. Appl. CB 2,351,502 (Cl. CllD3114). 3 Jan 2001, GB Appl. 199918,762, 17 Apr 1999. 11. The material for abrasive cosmetics and cleansing products comprises a pulverized fuel ash and/or a cenosphere (glass oxide microsphere) as abrasive agent.
Activated carbon fibers and films derived from poly(vinylidene fluoride)
02/00886
Yamashita, J. el crl. Corhon, 2001, 39, (2) 207-214. Activated carbons having different ranges of pore sizes from those derived by the conventional heat-treatment of organic compounds have been produced by carrying out a part of the conversion process through a liquid phase chemical treatment. Poly(vinylidene fluoride) (PVDF) was chosen as a starting polymer by taking into account the processability of this polymer into various geometries. The PVDF fibres and films were converted to activated carbons by using the combination of chemical dehydrofluorination with a strong base, hightemperature heat-treatment and activation in a carbon dioxide gas. The resulting activated carbon film exhibited superior methylene blue adsorption of 538 mg g ‘. Formation of a rigid skeleton during dehydrofluorination accounted for the ability of dehydrofluorinated PVDF to maintain its macroscopic precursor geometry during hightemperature heat-treatment and the formation of pores with large sizes.
Anodic performance and insertion mechanism of hard carbons prepared from synthetic isotropic pitches
02lOO887
Mochida, I. L’Irr[_ Curbon, 2001, 39, (3). 399-410. Anodic performances and structures of hard carbons prepared from synthetic isotropic pitches through solid phase oxidation were investigated to discuss their insertion sites for lithium ion and correlation between the capacity and structure. The derived hard carbons showed complicated voltage profiles of charge and discharge, indicating five kinds of insertion sites; partially charge transferring surface site (Type I), intercalation site like graphite (Type II), cluster gap between edges of carbon hexagon clusters (Type III), microvoid surrounded by hexagonal planes (Type IV) and atomic defect created by evolution of heteroatom (Type V). Types I-III are common to those found in the soft carbon. Very unique capacities of the present hard carbons calcined at 1000°C were found at the potentials of O-O.13 V (Type IV) and 0.5-2.0 V (Type V) and varied markedly with oxidization extent and heteroatom contents of precursor pitch, respectively. The microvoid among the hexagonal planes and atomic defects created by evolution of heteroatom are suggested to serve such insertion sites of Types IV and V, respectively. The microvoid holds reduced lithium ions with different extents of charge transfer to the carbon, which exist independently at 140 K but exchange rapidly at room temperature to their averaged chemical shift in ‘Li-NMR. Type V showed very similar charge-discharge behaviours to that of Type III, which was found more in the soft carbon carbonized at around 700°C and decreased sharply by the heat-treatment at 1000°C due to the coupling of hexagon clusters. The amount of microvoid or capacity at O-O.13 V is correlated to XRD parameters and oxygen content of the precursors. Smaller crystal, lower stacking or more oxygen content in the precursor allows apparently larger capacity. Random assemble of smaller graphitic units may induce the microvoid among the cluster units, although the microvoid has not been specifically defined yet. 02/00888
Ash utilization in India: challenge for the new
millennium Dhar, T.K. Fly Ash Disposal Uril.. In/. Cm/.. Proc., 2nd, 2000, I, 2/l-2/ 9. Edited by Varma C.V.J. The alarming magnitude of the problem of ash waste production has recently attracted the attention of government officials, scientists, technologists and policy-makers. Ash products are superior to conventional building products and provide an excellent opportunity for sustainable development. Development of suitable technologies for the use of ash and ash-based products and also state-of-the-art equipment required for manufacturing ash-based products has emerged as the major challenge for India. Concerted efforts from all sectors are required to take up the challenge and move fly ash from waste product category to co-product category. The present scenario of ash utilization of India, its potential for the future, and the opportunities and challenges it provides, are discussed. Also, the problems and suggestions with regards to promoting ash utilization in general and the use of ash-based products in particular, are discussed.