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03548 Improving limestone utilization in a commercial scale circulating fluidized bed boiler through ash reactivation and recycle
08 Steam raising (boiler operation/design)
compatible with the EU, Turow decided to, replace and upgrade six units (l-6) from 200 to 230 MW units and remove one unit 7. Units 8, 9 and 10 were equipped with dry sorbent desulfurization technology. Units 1 and 2 were replaced with new clean coal, circulating fluidized bed technology. These changes will make Turow, with six CFR units, the largest power station in the world based on fluidized bed technology. 00103546 Dynamic simulation of a circulating fluidized bed boiler of low circulating ratio with wide particle size distributions Lu, H. et al. Proc. Int. Conf Fluid. Bed Comhusr., 1999, 432440. This paper presents a steady state model of a coal fired CFB boiler considering the hydrodynamics, heat transfer and combustion. This model predicts the flue gas temperature, the chemical gas species (Oz, HaO, CO, COz and SOz) and char concentration distributions in both the axial and radial location along the furnace including the bottom and upper portion. To validate the model, it was compared to experimental data generated in a 35 t/h commercial CFB boiler with low circulating ratio. 00103547 Effect of thermochemical treatment of anthracite dust on changes of its properties Dunavskaya, N. I. Ekotekhnol. Resursoshere-/lenie, 1999, 2, 10-15. (In Russian) The thermochemical treatment of coal during its combustion is discussed as to whether it is the most effective way of improving the ignition and combustion of lower quality anthracites in utility boilers. The thermochemical preparation decreases the particle average diameter, increases the specific surface area, separates the organic and mineral matter, and partially gasifies coal. 00103546 Improving limestone utilization in a commercial scale circulating fluidized bed boiler through ash reactivation and recycle Tsuo, Y. et al. Proc. In/. Cot~f. Fluid. Bed Comhus~., 1999, 1278-1286. Using earlier bench-scale and pilot-scale studies, the partially reacted sorbent presented in the ash can be further utilized by various ash recycle processes, such as dry ash recycle or reactivated ash recycle. The ash hydration process, simply mixing ash and water together, was one of most feasible methods to reactivate the spent sorbent. The hydration process increases the accessibility of the unused calcium oxide in sorbent particle to sulfur dioxide. Field tests on the hydrated ash recycle were conducted in a Foster Wheeler commercial-scale circulating fluidized bed boiler. The effect of hydrated ash versus dry ash recycle and fly ash versus bottom ash recycle on boiler efficiency, limestone consumption and NOx emissions were investigated. Test results in these field tests showed that =lO-20% limestone saving can be achieved without any negative effect on boiler efficiency. It also demonstrated that there was no need for ash handling or environmental concerns as the ash hydration process can be done with a simple system. 00103549 Influence of air-staging on the concentration profiles of NH3 and HCN in the combustion chamber of a CFB boiler burning coal Kassman, H. et al. Proc. Inr. Con/Y Fluid. Bed Comhusr., 1999, 352-365. It is very important to understand the characterization of the concentration profiles of NHs and HCN if knowledge of the formation and destruction pathways of NO and NaO in a fluidized bed boiler is to be increased. Further improvements of the sampling methods for the determination of both NHs and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier transform infra red (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on the analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analysed by wet chemicals. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three airstaging cases with the addition of limestone for sulfur capture. The concentration profiles of NH3 and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NHs were observed during reducing conditions (severe airstaging), and the lowest were found under oxidizing conditions (no airstaging). The levels of HCN were much lower than those measured for NHs. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. In the case of the three airstaging cases, the potential reactions involving NHs and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed. 00/03550 Modeling of hydrodynamics of large scale atmospheric circulating fluidired bed coal combustors Leretaille, P. Y. et al. Proc. Int. Conf. Fluid. Bed Combusr. [computer
optical
estimation of the flow of solid near the walls was fulfilled with special care due to its influence on heat transfers. For the validation of the model, measurements of solid concentration with guarded capacitance probes were performed in the 250 MWe Stein Industrie-Lurgi type CFB boiler in Gardanne, France. Finally, an attempt to predict the vertical pressure profile in the riser, starting from the operating conditions (and based on an empirical evaluation of the variation of the downward flow of solid from local conditions) is presented and a comparison with the experimental data is made. 00103551 Numerical simulation of the combustion processes in a W-shaped boiler furnace under different operating conditions Liang, X. H. e/ al. Inr. J. Energy Res., 1999. 23, (S), 707-717. In this paper, numerical simulations of gas-solid flows, heat transfer and gas-particle turbulent combustion are conducted for a three-dimensional, W-shaped boiler furnace. The gas-particle flow, distributions of temperature and concentrations of gaseous constituents, distributions of the rates of heat release, burnout rates of coal particles, and formations of volatiles have been predicted. The results indicate that a steady high-temperature zone is formed under the arch of the W-shaped flame boiler. This zone would be of benefit to the ignition and carbon burn-out. The results also suggest that the W-shaped flame boiler is suitable for burning low-quality coals and can operate well for full and partial loads under different operating conditions. 00/03552 Removal of boiler emissions from air Batluk, V. A. Ekotekhnol. Resursoshere-henie, 1997, 6, 47-50. (In Ukrainian) This paper presents an analysis of ash dispersed from the burning of coal from the Lvov-Volyn basin. An ash-catching plant has been proposed. It includes an ash separator with an ash storage bin, for which an optimum form and sizes ratio has been determined. Introduction of this plant increases the efficiency of dust catching by 2-3%, decreasing the dimension sizes and hydraulic strength. Slurry feeders for pressurized fluidired-bed boilers 00/03553 Wada, S. Jpn. Kokai Tokkyo Koho JP 11 211,067 [99 211,0671 0 (Cl. F23Kl/ 02), 6 Aug 1999, Appl. 1998115,907, 28 Jan 1998. 5. (In Japanese) The slurry feeders for pressurized-bed boilers are equipped with a sludge feeder, a fuel control circuit for the coal-feeding motor based on heat generation, and a water control circuit for the water-feeding valve based on the fuel slurry concentration. The CFB boiler in Gardanne - an experimental 00/03554 investigation of its bottom zone Wiesendorf, V. er al. Proc. In/. Conf. Fluid. Bed Comhusr., 1999, 1514-1524. The fluid dynamics in the bottom zone of the 250 MWe circulating fluidized bed (CFB) boiler in Gardanne, France were analysed using different measurement techniques. In particular, horizontal profiles of the local solids volume concentration were measured with a capacitance probe and the vertical pressure profile was measured by a probe with densely spaced pressure taps. Local velocities were measured by cross-correlating the signals of a two-channel capacitance probe. In order to get some information on the influence of the flow structure on local combustion conditions a probe was used which combines both capacitance and zirconiacell sensors. This probe measured simultaneously local solids volume concentrations, local velocities and the local presence of oxygen. The results show the existence of a dense bed with a bed height of ~2% of the total riser height. This bottom bed has a flow structure which is different from the core-annulus structure observed in the upper dilution zone of the CFB combustor by several researchers. The lateral solids mixing does not seem to be enough to provide an even distribution of char over the whole crosssection of the bottom bed. However, the discovery of an even temperature distribution in the end did indicate that mixing is sufficient to equalize the uneven heat generation. 00103555 The implication of CFB technology for repowering of old pulverized coal boiler in Russian Ryabov, G. A. and Nadirov, I. 1. Proc. Inr. Cotzf. Fluid. Bed Combusr., 1999, 1803-1811. The development of new economically efficient and environmentally friendly technologies is one of the main priorities of the energy strategy of Russia. At the moment > 100 old pulverized coal boilers with steam capacity of 170-240 t/h need to be reconstructed. Modern requirements on pollution and possibility of low-grade coal firing make the usage of CFB technology more attractive. This paper presents some results of an economic comparison and estimations of the power range versus typical Russian fuel quality. Different CFB technology modifications are compared. As a results it would be perspective to use the CFB boiler with simple impact ash collectors. Some technical data of boiler design for Nesvetay thermal power plant (TPP) and Cherepetskay TPP are given.
disk], 1999, 15, 228-240.
This paper proposes a model for the evaluation of hydrodynamics of the gas-solid flow in the riser of a circulating fluidized bed coal boiler. The 3D fields of the gas and solid velocities and of the solid concentration in the riser are estimated from measured data of the vertical pressure profile. The model includes semi-empirical laws developed on the basis of a set of experimental data on six industrial boilers ranging from 12 MWth to 700 MWth. Its relevance for laboratory scale risers was not tested. The
396
Fuel and Energy Abstracts
November 2000
00103556 Update of operating experience of B&W IR-CFB coalfired boilers Belin, F. er al. Proc. Inl. Cmf. Fluid. Bed Cornbust., 1999, 822-831. The operating experience of two Babcock & Wilcox (B&W) coal-fired, internal recirculation circulating fluidized-bed (IR-CFB) boilers is updated in this paper. The first boiler is located at Southern Illinois University (SIU) in Carbondale, Illinois USA, and is designed for 35 MWth output for
compatible with the EU, Turow decided to, replace and upgrade six units (l-6) from 200 to 230 MW units and remove one unit 7. Units 8, 9 and 10 were equipped with dry sorbent desulfurization technology. Units 1 and 2 were replaced with new clean coal, circulating fluidized bed technology. These changes will make Turow, with six CFR units, the largest power station in the world based on fluidized bed technology. 00103546 Dynamic simulation of a circulating fluidized bed boiler of low circulating ratio with wide particle size distributions Lu, H. et al. Proc. Int. Conf Fluid. Bed Comhusr., 1999, 432440. This paper presents a steady state model of a coal fired CFB boiler considering the hydrodynamics, heat transfer and combustion. This model predicts the flue gas temperature, the chemical gas species (Oz, HaO, CO, COz and SOz) and char concentration distributions in both the axial and radial location along the furnace including the bottom and upper portion. To validate the model, it was compared to experimental data generated in a 35 t/h commercial CFB boiler with low circulating ratio. 00103547 Effect of thermochemical treatment of anthracite dust on changes of its properties Dunavskaya, N. I. Ekotekhnol. Resursoshere-/lenie, 1999, 2, 10-15. (In Russian) The thermochemical treatment of coal during its combustion is discussed as to whether it is the most effective way of improving the ignition and combustion of lower quality anthracites in utility boilers. The thermochemical preparation decreases the particle average diameter, increases the specific surface area, separates the organic and mineral matter, and partially gasifies coal. 00103546 Improving limestone utilization in a commercial scale circulating fluidized bed boiler through ash reactivation and recycle Tsuo, Y. et al. Proc. In/. Cot~f. Fluid. Bed Comhus~., 1999, 1278-1286. Using earlier bench-scale and pilot-scale studies, the partially reacted sorbent presented in the ash can be further utilized by various ash recycle processes, such as dry ash recycle or reactivated ash recycle. The ash hydration process, simply mixing ash and water together, was one of most feasible methods to reactivate the spent sorbent. The hydration process increases the accessibility of the unused calcium oxide in sorbent particle to sulfur dioxide. Field tests on the hydrated ash recycle were conducted in a Foster Wheeler commercial-scale circulating fluidized bed boiler. The effect of hydrated ash versus dry ash recycle and fly ash versus bottom ash recycle on boiler efficiency, limestone consumption and NOx emissions were investigated. Test results in these field tests showed that =lO-20% limestone saving can be achieved without any negative effect on boiler efficiency. It also demonstrated that there was no need for ash handling or environmental concerns as the ash hydration process can be done with a simple system. 00103549 Influence of air-staging on the concentration profiles of NH3 and HCN in the combustion chamber of a CFB boiler burning coal Kassman, H. et al. Proc. Inr. Con/Y Fluid. Bed Comhusr., 1999, 352-365. It is very important to understand the characterization of the concentration profiles of NHs and HCN if knowledge of the formation and destruction pathways of NO and NaO in a fluidized bed boiler is to be increased. Further improvements of the sampling methods for the determination of both NHs and HCN in the combustion chamber in full-scale CFB boilers are also needed. A gas-sampling probe connected to a Fourier transform infra red (FTIR) instrument and a gas-quenching (GQ) probe in which the sample is quenched directly in the probe tip by a circulating trapper solution were used. The FTIR technique is based on the analysis of hot combustion gases, whereas the trapper solutions from the GQ probe were analysed by wet chemicals. The tests were performed during coal combustion in a 12 MW CFB boiler, which was operated at three airstaging cases with the addition of limestone for sulfur capture. The concentration profiles of NH3 and HCN in the combustion chamber showed a different pattern concerning the influence of air-staging. The highest levels of NHs were observed during reducing conditions (severe airstaging), and the lowest were found under oxidizing conditions (no airstaging). The levels of HCN were much lower than those measured for NHs. The highest levels of HCN were observed for reversed air-staging and severe air-staging showed almost no HCN. In the case of the three airstaging cases, the potential reactions involving NHs and HCN in the combustion chamber as well as the potential measurement errors in each sampling technique are discussed. 00/03550 Modeling of hydrodynamics of large scale atmospheric circulating fluidired bed coal combustors Leretaille, P. Y. et al. Proc. Int. Conf. Fluid. Bed Combusr. [computer
optical
estimation of the flow of solid near the walls was fulfilled with special care due to its influence on heat transfers. For the validation of the model, measurements of solid concentration with guarded capacitance probes were performed in the 250 MWe Stein Industrie-Lurgi type CFB boiler in Gardanne, France. Finally, an attempt to predict the vertical pressure profile in the riser, starting from the operating conditions (and based on an empirical evaluation of the variation of the downward flow of solid from local conditions) is presented and a comparison with the experimental data is made. 00103551 Numerical simulation of the combustion processes in a W-shaped boiler furnace under different operating conditions Liang, X. H. e/ al. Inr. J. Energy Res., 1999. 23, (S), 707-717. In this paper, numerical simulations of gas-solid flows, heat transfer and gas-particle turbulent combustion are conducted for a three-dimensional, W-shaped boiler furnace. The gas-particle flow, distributions of temperature and concentrations of gaseous constituents, distributions of the rates of heat release, burnout rates of coal particles, and formations of volatiles have been predicted. The results indicate that a steady high-temperature zone is formed under the arch of the W-shaped flame boiler. This zone would be of benefit to the ignition and carbon burn-out. The results also suggest that the W-shaped flame boiler is suitable for burning low-quality coals and can operate well for full and partial loads under different operating conditions. 00/03552 Removal of boiler emissions from air Batluk, V. A. Ekotekhnol. Resursoshere-henie, 1997, 6, 47-50. (In Ukrainian) This paper presents an analysis of ash dispersed from the burning of coal from the Lvov-Volyn basin. An ash-catching plant has been proposed. It includes an ash separator with an ash storage bin, for which an optimum form and sizes ratio has been determined. Introduction of this plant increases the efficiency of dust catching by 2-3%, decreasing the dimension sizes and hydraulic strength. Slurry feeders for pressurized fluidired-bed boilers 00/03553 Wada, S. Jpn. Kokai Tokkyo Koho JP 11 211,067 [99 211,0671 0 (Cl. F23Kl/ 02), 6 Aug 1999, Appl. 1998115,907, 28 Jan 1998. 5. (In Japanese) The slurry feeders for pressurized-bed boilers are equipped with a sludge feeder, a fuel control circuit for the coal-feeding motor based on heat generation, and a water control circuit for the water-feeding valve based on the fuel slurry concentration. The CFB boiler in Gardanne - an experimental 00/03554 investigation of its bottom zone Wiesendorf, V. er al. Proc. In/. Conf. Fluid. Bed Comhusr., 1999, 1514-1524. The fluid dynamics in the bottom zone of the 250 MWe circulating fluidized bed (CFB) boiler in Gardanne, France were analysed using different measurement techniques. In particular, horizontal profiles of the local solids volume concentration were measured with a capacitance probe and the vertical pressure profile was measured by a probe with densely spaced pressure taps. Local velocities were measured by cross-correlating the signals of a two-channel capacitance probe. In order to get some information on the influence of the flow structure on local combustion conditions a probe was used which combines both capacitance and zirconiacell sensors. This probe measured simultaneously local solids volume concentrations, local velocities and the local presence of oxygen. The results show the existence of a dense bed with a bed height of ~2% of the total riser height. This bottom bed has a flow structure which is different from the core-annulus structure observed in the upper dilution zone of the CFB combustor by several researchers. The lateral solids mixing does not seem to be enough to provide an even distribution of char over the whole crosssection of the bottom bed. However, the discovery of an even temperature distribution in the end did indicate that mixing is sufficient to equalize the uneven heat generation. 00103555 The implication of CFB technology for repowering of old pulverized coal boiler in Russian Ryabov, G. A. and Nadirov, I. 1. Proc. Inr. Cotzf. Fluid. Bed Combusr., 1999, 1803-1811. The development of new economically efficient and environmentally friendly technologies is one of the main priorities of the energy strategy of Russia. At the moment > 100 old pulverized coal boilers with steam capacity of 170-240 t/h need to be reconstructed. Modern requirements on pollution and possibility of low-grade coal firing make the usage of CFB technology more attractive. This paper presents some results of an economic comparison and estimations of the power range versus typical Russian fuel quality. Different CFB technology modifications are compared. As a results it would be perspective to use the CFB boiler with simple impact ash collectors. Some technical data of boiler design for Nesvetay thermal power plant (TPP) and Cherepetskay TPP are given.
disk], 1999, 15, 228-240.
This paper proposes a model for the evaluation of hydrodynamics of the gas-solid flow in the riser of a circulating fluidized bed coal boiler. The 3D fields of the gas and solid velocities and of the solid concentration in the riser are estimated from measured data of the vertical pressure profile. The model includes semi-empirical laws developed on the basis of a set of experimental data on six industrial boilers ranging from 12 MWth to 700 MWth. Its relevance for laboratory scale risers was not tested. The
396
Fuel and Energy Abstracts
November 2000
00103556 Update of operating experience of B&W IR-CFB coalfired boilers Belin, F. er al. Proc. Inl. Cmf. Fluid. Bed Cornbust., 1999, 822-831. The operating experience of two Babcock & Wilcox (B&W) coal-fired, internal recirculation circulating fluidized-bed (IR-CFB) boilers is updated in this paper. The first boiler is located at Southern Illinois University (SIU) in Carbondale, Illinois USA, and is designed for 35 MWth output for