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01427 Ash fusion temperatures and the transformations of coal ash particles to slag
09
Combustion
(burners, combustion
systems)
limitation is currently based primarily on information reported by UK utilities. A sound understanding of the effects of chlorine on fireside corrosion in utility boilers would provide a rational basis for utility costbenefit decisions. Such an understanding also could lead to a basis for increasing the interest of utilities in high chlorine coals, which are currently under-utilized. The paper summarizes the results of (1) the many years of experience that UK utilities have had with high-chlorine coals (2) a test programme in the UK, employing novel corrosion probe technology in a model test facility, to derive a relation for use in coal quality evaluation tools and (3) an overview of lessons learned from the UK experience that should allow utilities to develop a more informed position when considering use of high-chlorine coal.
variables. By differentiating the entropy generation number equation respect to the operating parameters, various optimization parameters be obtained.
09
Research priorities in chemistry to control corrosion on the secondary side of steam generators
99101422
Baes, C. F. Control Corros. Second. Side Steam Gener., Proc. Meet., 1995 (Pub. 1996), 27-33. Edited by Staehle, R. W. et al., NACE International, Houston, Texas. In the investigation of corrosion in steam boilers, the methods of chemical thermodynamics embodied in MULTEQ provide a valuable tool. The most important modelling needs of MULTEQ include (1) an improved treatment of the thermodynamics of electrolyte solutions that changes in a continuous fashion from the present treatment of diluted solutions to one for concentrated solutions more suited to wet molten salts; (2) improved correlations of the entropy change for reactions that, along with the use of the isocoulombic rule, will enable one to establish more reliably the species formed by the association of ions in aqueous solutions at high temperatures. The most important data needs of MULTEQ include (1) solubility measurements, especially of new substances found in corrosion environments; (2) pH measurements with the hydrogen electrode, especially in conjunction with solubility measurements of oxides and hydroxides, to establish the species formed by metal ions in high temperature aqueous solutions; and (3) continued support of existing programmes of isopiestic, calorimetric, conductivity, density and volatility measurements in high temperature aqueous systems.
Retrofit of a 75 t/h pulverized-coal-fired boiler into a 100 t/h circulating fluidized bed boiler
99101423
Wang, Q. et al. Zhejiang Daxue Xuebao, Ziran Kexueban, 1997, 31, (5), 628-634. (In Chinese) Proposed was a new scheme to retrofit a 75 t/h pulverized coal fired (PC) boiler into a 100 t/h circulating fluidized bed boiler. This practical retrofitting scheme is applied to solve the operating problem of the 75 t/h PC boiler in a chemical plant. It can be extensively applied to the existing PC boiler in China because of the advantages of circulating fluidized bed boiler.
Slagging tendency of peat ash 99101424 Heikainen, R. et al. Fuel Process. Technol., 1998, 56, (l-2) 69-80. In Finland the combustion of peat in power plant boilers has increased in recent years. Whereas the operation of such power plants is generally smooth, the slagging of peat ash can, in some cases, lead to a plant shutdown, thus causing significant economic losses to the entire energyproduction chain. It is therefore important to predict the slagging tendency of ash in a given peat type prior to combustion. In this work we discuss the factors involved in the slag formation of peat samples. The work centres both on standard peat ash and on the samples collected from an actual power-plant boiler. To complement the microscopic studies, the formation and properties of ash particles have been studied with SEM combined with automatic image analysis X-ray powder diffraction data. Three gas reburning field applications. Final re99101425 sults and long-term performance Folsom, B. et al. Combust. Can. ‘96 Conf: Future Changing Role Combust. Can.-Efjk. Environ., 1996, (39), 1-18. In boiler/furnace applications Gas Reburning (GR) is a NO, control technology. Natural gas is injected above the burner zone to produce a slightly fuel-rich zone where NOx may be reduced by 60-70%. Overfire air completes the gas combustion. As part of the US Department of Energy’s Clean Coal Technology Program three comprehensive GR demonstrations have been completed on US utility boilers. The boilers included tangential, wall and cyclone firing configurations firing coal with capacities of 33 to 158 MW net. Two of the units were also tested firing 100% gas as the primary and reburning fuels and on one unit GR was integrated with low-NO, coal burners. One of the demonstrations included first and second generation GR designs. The second generation improvements included elimination of flue gas recirculation (FGR) as the natural gas carrier and dual concentric overfire air ports. Data is presented showing both parametric test results and long-term performance in normal utility service. With no significant adverse operational impacts NO, reductions up to 76% and NO, levels as low as 0.05 lb/106 Btu (on 100% gas) were achieved.
Waste heat bollsr optimization by entropy mini99101426 mization principle
Reddy, B. V. et al. AES (Am. Sot. Mech. Eng.), 1996,36,465-471. For a waste heat boiler having an economizer, evaporator and superheater, a second law analysis has been undertaken. Following the principle of minimization of entropy generation, a general equation for entropy generation number is derived, which incorporates all the operating
144 Fuel and Energy Abstracts
March 1999
with can
COMBUSTION Burners, Combustion
Systems
99101427 Ash fusion temperatures and the transformations of coal ash particles to slag
Gupta, S. K. et al. Fuel Process. Technol., 1998, 56, (l-2) 33-43. Coal ash is heated and its shrinkage is measured continuously up to a temperature of 1600°C. The temperatures corresponding to the rapid rate of shrinkage correspond to the formation of eutectics identified on phase diagrams. Samples were therefore heated to these temperatures, cooled rapidly and examined using a scanning electron microscope (SEM) to identify the associated chemical and physical changes. The progressive changes in the range of chemical composition, the extent of undissolved ash particles and porosity were then quantified and related to homogenization, viscosity and ash fusion mechanisms. Alternative ash fusion temperatures based on different levels of shrinkage have also been suggested to characterize the ash deposition tendency of the coals.
99101428 Assessment of ability of limestone for fixing sulfur in coal combustion Yu, 2. et al. Huanjing Baohu, 1997, (7), 28-30. (In Chinese) By using the TGD thermal analysis instrument and ZCL automatic sulfurmeasuring instrumental direct integral method, the ability of sulfur fixing by limestone in coal combustion was assessed. Both methods worked well, but ZCL was found to be better than TGD.
Catalytic pyrolysis and gasification of coal in an atmospheric pressure whe-mesh reactor
99101429
Lemaignen, L. et al. IChemE Res. Event, Two-Day Symp., 1998, 586-595. In our laboratory, the atmospheric pressure wire-mesh reactor allows the study of coal pyrolysis and gasification under various experimental conditions without secondary reactions of the primary volatiles released. The heating rate can be as high as 5000 K/s and the holding temperature can be chosen up to 1500 K. These characteristics make this reactor a powerful tool to study every step of the industrial gasification process. The reactor has been used to study the influence of inherent mineral matter on the pyrolysis and COz gasification of a base coal under atmospheric pressure. Because of its inactive mineral matter content, Longannet is the coal chosen. The coal has been tested raw, demineralized (with HF and HCI) and impregnated with aqueous solutions of different salts believed to catalyse the gasification reaction. The samples have been characterized by SEM, Fourier Transform IR (ET-IR) spectroscopy and surface area determination, in both nitrogen and carbon dioxide.
99101430 Characterization of coke on H-gallosilicate (MFI) propane aromatization catalyst. Influence of coking conditions on nature and removal of coke ChTurhary,
V. R. et al.
Microporous Mesoporous Mater., 1998, 21, (l-3),
Using i3C-CP-MAS NMR, ESE, IR, thermal analysis, GC-MS analysis and temperature-programmed oxidation (TPO) coke deposited on H-gallosilicate (MFJ) catalyst in propane aromatization was characterized. The nature of the coke and its removal from the zeolite are strongly influenced by the coking conditions, particularly temperature and space velocity, used in the propane aromatization. However, the period of coking has little or no effect on both the nature and removal of coke. Aromatization in high temperature and at low space velocity, the coke formed is insoluble (or hard) and nonvolatile in nature; it consists of highly polycondensed aromatics having graphite-like character. Its removal is possible only by oxidative treatment at high temperature. However, with the decrease in the coking temperature, the coke nature is gradually changed from highly polyaromatic to low polyaromatic. Also the coke removal by oxidative treatment becomes easier; it can be effected at lower temperatures. The formation of CO and COz in coke oxidation is strongly influenced by the coking conditions and hence by the nature of the coke.
99101431 Co-pyrolysis of carbochemlcal waste plastic materlals
compounds with
Kaloc, M. DGMK Tagungsber., 1998, 9802, 271-277. Investigated was the utilization of waste plastic materials at co-pyrolysis with higher aromatic substances (coal tar and pitch) was compared with products of standard tar and pitch pyrolysis. The co-pyrolysis of carbochemical products with waste plastics is technologically feasible. Plastics admixture influences the yield of liquid and gaseous products, a
Combustion
(burners, combustion
systems)
limitation is currently based primarily on information reported by UK utilities. A sound understanding of the effects of chlorine on fireside corrosion in utility boilers would provide a rational basis for utility costbenefit decisions. Such an understanding also could lead to a basis for increasing the interest of utilities in high chlorine coals, which are currently under-utilized. The paper summarizes the results of (1) the many years of experience that UK utilities have had with high-chlorine coals (2) a test programme in the UK, employing novel corrosion probe technology in a model test facility, to derive a relation for use in coal quality evaluation tools and (3) an overview of lessons learned from the UK experience that should allow utilities to develop a more informed position when considering use of high-chlorine coal.
variables. By differentiating the entropy generation number equation respect to the operating parameters, various optimization parameters be obtained.
09
Research priorities in chemistry to control corrosion on the secondary side of steam generators
99101422
Baes, C. F. Control Corros. Second. Side Steam Gener., Proc. Meet., 1995 (Pub. 1996), 27-33. Edited by Staehle, R. W. et al., NACE International, Houston, Texas. In the investigation of corrosion in steam boilers, the methods of chemical thermodynamics embodied in MULTEQ provide a valuable tool. The most important modelling needs of MULTEQ include (1) an improved treatment of the thermodynamics of electrolyte solutions that changes in a continuous fashion from the present treatment of diluted solutions to one for concentrated solutions more suited to wet molten salts; (2) improved correlations of the entropy change for reactions that, along with the use of the isocoulombic rule, will enable one to establish more reliably the species formed by the association of ions in aqueous solutions at high temperatures. The most important data needs of MULTEQ include (1) solubility measurements, especially of new substances found in corrosion environments; (2) pH measurements with the hydrogen electrode, especially in conjunction with solubility measurements of oxides and hydroxides, to establish the species formed by metal ions in high temperature aqueous solutions; and (3) continued support of existing programmes of isopiestic, calorimetric, conductivity, density and volatility measurements in high temperature aqueous systems.
Retrofit of a 75 t/h pulverized-coal-fired boiler into a 100 t/h circulating fluidized bed boiler
99101423
Wang, Q. et al. Zhejiang Daxue Xuebao, Ziran Kexueban, 1997, 31, (5), 628-634. (In Chinese) Proposed was a new scheme to retrofit a 75 t/h pulverized coal fired (PC) boiler into a 100 t/h circulating fluidized bed boiler. This practical retrofitting scheme is applied to solve the operating problem of the 75 t/h PC boiler in a chemical plant. It can be extensively applied to the existing PC boiler in China because of the advantages of circulating fluidized bed boiler.
Slagging tendency of peat ash 99101424 Heikainen, R. et al. Fuel Process. Technol., 1998, 56, (l-2) 69-80. In Finland the combustion of peat in power plant boilers has increased in recent years. Whereas the operation of such power plants is generally smooth, the slagging of peat ash can, in some cases, lead to a plant shutdown, thus causing significant economic losses to the entire energyproduction chain. It is therefore important to predict the slagging tendency of ash in a given peat type prior to combustion. In this work we discuss the factors involved in the slag formation of peat samples. The work centres both on standard peat ash and on the samples collected from an actual power-plant boiler. To complement the microscopic studies, the formation and properties of ash particles have been studied with SEM combined with automatic image analysis X-ray powder diffraction data. Three gas reburning field applications. Final re99101425 sults and long-term performance Folsom, B. et al. Combust. Can. ‘96 Conf: Future Changing Role Combust. Can.-Efjk. Environ., 1996, (39), 1-18. In boiler/furnace applications Gas Reburning (GR) is a NO, control technology. Natural gas is injected above the burner zone to produce a slightly fuel-rich zone where NOx may be reduced by 60-70%. Overfire air completes the gas combustion. As part of the US Department of Energy’s Clean Coal Technology Program three comprehensive GR demonstrations have been completed on US utility boilers. The boilers included tangential, wall and cyclone firing configurations firing coal with capacities of 33 to 158 MW net. Two of the units were also tested firing 100% gas as the primary and reburning fuels and on one unit GR was integrated with low-NO, coal burners. One of the demonstrations included first and second generation GR designs. The second generation improvements included elimination of flue gas recirculation (FGR) as the natural gas carrier and dual concentric overfire air ports. Data is presented showing both parametric test results and long-term performance in normal utility service. With no significant adverse operational impacts NO, reductions up to 76% and NO, levels as low as 0.05 lb/106 Btu (on 100% gas) were achieved.
Waste heat bollsr optimization by entropy mini99101426 mization principle
Reddy, B. V. et al. AES (Am. Sot. Mech. Eng.), 1996,36,465-471. For a waste heat boiler having an economizer, evaporator and superheater, a second law analysis has been undertaken. Following the principle of minimization of entropy generation, a general equation for entropy generation number is derived, which incorporates all the operating
144 Fuel and Energy Abstracts
March 1999
with can
COMBUSTION Burners, Combustion
Systems
99101427 Ash fusion temperatures and the transformations of coal ash particles to slag
Gupta, S. K. et al. Fuel Process. Technol., 1998, 56, (l-2) 33-43. Coal ash is heated and its shrinkage is measured continuously up to a temperature of 1600°C. The temperatures corresponding to the rapid rate of shrinkage correspond to the formation of eutectics identified on phase diagrams. Samples were therefore heated to these temperatures, cooled rapidly and examined using a scanning electron microscope (SEM) to identify the associated chemical and physical changes. The progressive changes in the range of chemical composition, the extent of undissolved ash particles and porosity were then quantified and related to homogenization, viscosity and ash fusion mechanisms. Alternative ash fusion temperatures based on different levels of shrinkage have also been suggested to characterize the ash deposition tendency of the coals.
99101428 Assessment of ability of limestone for fixing sulfur in coal combustion Yu, 2. et al. Huanjing Baohu, 1997, (7), 28-30. (In Chinese) By using the TGD thermal analysis instrument and ZCL automatic sulfurmeasuring instrumental direct integral method, the ability of sulfur fixing by limestone in coal combustion was assessed. Both methods worked well, but ZCL was found to be better than TGD.
Catalytic pyrolysis and gasification of coal in an atmospheric pressure whe-mesh reactor
99101429
Lemaignen, L. et al. IChemE Res. Event, Two-Day Symp., 1998, 586-595. In our laboratory, the atmospheric pressure wire-mesh reactor allows the study of coal pyrolysis and gasification under various experimental conditions without secondary reactions of the primary volatiles released. The heating rate can be as high as 5000 K/s and the holding temperature can be chosen up to 1500 K. These characteristics make this reactor a powerful tool to study every step of the industrial gasification process. The reactor has been used to study the influence of inherent mineral matter on the pyrolysis and COz gasification of a base coal under atmospheric pressure. Because of its inactive mineral matter content, Longannet is the coal chosen. The coal has been tested raw, demineralized (with HF and HCI) and impregnated with aqueous solutions of different salts believed to catalyse the gasification reaction. The samples have been characterized by SEM, Fourier Transform IR (ET-IR) spectroscopy and surface area determination, in both nitrogen and carbon dioxide.
99101430 Characterization of coke on H-gallosilicate (MFI) propane aromatization catalyst. Influence of coking conditions on nature and removal of coke ChTurhary,
V. R. et al.
Microporous Mesoporous Mater., 1998, 21, (l-3),
Using i3C-CP-MAS NMR, ESE, IR, thermal analysis, GC-MS analysis and temperature-programmed oxidation (TPO) coke deposited on H-gallosilicate (MFJ) catalyst in propane aromatization was characterized. The nature of the coke and its removal from the zeolite are strongly influenced by the coking conditions, particularly temperature and space velocity, used in the propane aromatization. However, the period of coking has little or no effect on both the nature and removal of coke. Aromatization in high temperature and at low space velocity, the coke formed is insoluble (or hard) and nonvolatile in nature; it consists of highly polycondensed aromatics having graphite-like character. Its removal is possible only by oxidative treatment at high temperature. However, with the decrease in the coking temperature, the coke nature is gradually changed from highly polyaromatic to low polyaromatic. Also the coke removal by oxidative treatment becomes easier; it can be effected at lower temperatures. The formation of CO and COz in coke oxidation is strongly influenced by the coking conditions and hence by the nature of the coke.
99101431 Co-pyrolysis of carbochemlcal waste plastic materlals
compounds with
Kaloc, M. DGMK Tagungsber., 1998, 9802, 271-277. Investigated was the utilization of waste plastic materials at co-pyrolysis with higher aromatic substances (coal tar and pitch) was compared with products of standard tar and pitch pyrolysis. The co-pyrolysis of carbochemical products with waste plastics is technologically feasible. Plastics admixture influences the yield of liquid and gaseous products, a