- Email: [email protected]
01421 Possible effects of coal chlorine on furnace wall fireside corrosion in utility boilers
06 Steam raising (boiler operation/design) 99101412 High temperature corrosion of boiler tube steels in simulated coal-fired plant atmospheres containing water vapor Quadakkers, W. J. et al. Corros. Its Control, Proc. Int. Conf. Corros., 1997 (Pub 1998). (l), 199-207. Edited by Khanna, A. S. et al. An investigation has been carried out into the corrosion behaviour of ferritic steels in atmospheres simulating the service environments of components operating in coal-fired power generation plants. The oxidation rates depend heavily upon the chromium content - the 12% chromium steels that have chromium contents near to the maximum specified exhibiting very much better corrosion resistance than steels with 9% chromium. The effect of the observed corrosion rates on the service life has been estimated. The loss of a load-bearing cross-section leads to an increase in the effective stress on the component and an associated reduction in service life. The magnitude of the life reduction effect for tube components with wall thicknesses between 2 and 20 mm has been calculated; the effect of corrosion in the service environment cannot be neglected for components of wall thickness below about 6 mm. Therefore, despite the inherently higher stress rupture strength of the 9% chromium steels, thinwalled components of the 9% chromium steels may offer no advantage over the 12% chromium steels in terms of service life.
Hot corrosion of the steel grades lSChlMF, 13CrMo4-4 and lOCrMoS-10 in a pulverized coal boiler at a metal temperature <540 99101413
Tallermo, H. and Klevtsov, I. VOE Kraftwerkstech., 1998, 78, (8), 105-111. (In German) An experimental investigation of the corrosion of the title substances in chlorine-containing ash deposits of a pulverized coal boiler was carried out. The mechanism of corrosion acceleration in the 12ChlMF steel was analysed for the concentration of chlorine in the outer deposits and the empirical terms for the determination of corrosion depth were identified for all steels.
in-bed recirculation 99101414 circulating fluidized bed boiler
of particle
and design of
He, Q. et al. Ranshao Kexue Yu Jishu, 1998, 4, (l), 69-74. (In Chinese) In recent years, circulating fluidized bed combustion technology has been extensively developed in China. The coal feed size ranges from 2 mm to 3.5 mm resulting in a fluidized bed consisting of a dense and a diluted phase zone. The coal combustion fraction in the dense phase zone is larger, so the heat balance and heat exchange surface area of the dense phase zone are very important. If the heat exchange area is designed too large or not large enough, the circulating fluidized bed boiler can not run stably. This paper analyses the heat balance and conducts the design of heat exchange surface of the dense phase zone for a circulating fluidized bed boiler of 75 t/h steam capacity. Also discussed is the effect of coal type, recirculation ratio of fly ash and coal combustion fraction on amount of heat exchange surface and height of dense phase zone.
The influence of fouling on the heat transfer 99lO1415 characteristics of boiler tubes: a comparison between a numerical simulatlon and an industrial test case Delle Site, C. et al. AES (Am. Sot. Mech. Eng.), 1997, 37, 271-278. A numerical simulation of the effects of fouling on a representative section of the vertical boiler tubes in a pulverized coal boiler for a thermoelectric power plant is presented in this paper. The fouling is here simulated by a uniform coating of solid homogeneous material with average thermal properties derived by experimental data. Both heat transfer modes are simulated in the numerical calculation, that has been performed via a commercial finite-element code, FIDAP of FDI Inc. After a twodimensional numerical test, necessary to calibrate the simulation parameters and to determine a suitable mesh, a fully three-dimensional simulation was carried out. Full account has been taken of the properties of the real fluid and of the real characteristics of its flow. The heat transfer in the coating and in the tube wall has been calculated without introducing heat exchange coefficients, but imposing instead a well-established heat transfer correlation for the boiling water side. Using a modified k-c model, turbulent effects have been simulated. Periodic flow in the vertical direction and forced velocity on the core side have been imposed as boundary conditions. The results of the numerical computation are compared with those of an extensive experimental campaign conducted in 1992 on an industrial boiler for a pulverized coal, 240 MW power plant. It is shown that the numerical results agree verv well with the exuerimental data for the selected test section: it iH therefire proposed to extknd the generality of the numerical simulation to implement and complete the results of future tests on the effects of fouling.
Measurement of the viscosity of coal ashes for the 99101416 analysis of the position of deposits in steam boilers Vaisburd, S. et al. VGB Kruftwerkstech, 1998, 78, (8), 70-73. (In German) At temperatures of 1450-155O”C, the viscosity of ash samples was determined with a high-temperature viscosimeter. The results revealed the viscosity had an exponential dependence on the reciprocal temperature. The activation energy of the viscous ash fusion flow was calculated from this dependence. The results of calculations were found to be valid only if the composition of the ash is comparable with that from which the method of calculation was derived. At various sites of the boiler, the comparison of the temperature with the corresponding ash viscosities can be used to predict the sites of ash deposition.
99101417
The modelina of LEBS-Kalina Dower cvcles
Enick, R. M. et al. PWR (Am. Sot. Mech. Eng.), 7997, 32,12), 55-67. The LEBS (low emission boiler system) is an advanced, pulverized coalfired plant .designed to provide-power in an economic, efficient and environmentally sound manner. Thermal efficiencies of LEBS plants are exoected to be at least 42% HHV (hieher heating value).,I a sienificant \ ikprovement over conventional systems. Two types of working fliids are being considered by DOE contractors developing the LEBS technology, supercritical steam and ammonia-water mixtures used in the Kalina cycle. In this study, a LEBS-Kalina power cycle was modelled. The working fluid composition for the Kalina cycle was 25% water/75% ammonia. A pinch analysis of the plant indicated that the heat exchange network was efficiently designed. Simulations were performed using AspenPlus, a process simulator. The Schwartzentruber-Renon equation of state and the more accurate WATAM program developed by Exergy were used for thermodynamic calculations. An overly optimistic efficiency was obtained when the less accurate thermodynamic model was used. The net plant efficiency of the LEBS-Kalina System 5 plant modelled using WATAM was 41.0% operating at turbine inlet conditions of 1050°F and 2415 psia. In preliminary results, net plant efficiencies greater than 42% were attained for more advanced LEBS-Kalina cycles by incorporating heat exchange networks that were more efficient than System 5. D
NO, control industrial cyclone boiler
99101416
using natural
gas reburn on an
Farzan, H. et al. PWR (Am. Sot. Mech. Eng.), 1996, 30, (2), 835-845. Located in Rochester, New York, Eastman Kodak Company’s cyclone boiler, has been retrofitted with the gas reburn technology developed by the Babcock & Wilcox (B&W) Company to reduce NO, emissions in order to comply with the New York State regulations adopted in conformance with the Title I of the Clean Air Act Amendments (CAAA) of 1990. At the peak load, the ozone non-attainment required NO, reduction from baseline levels necessary to meet the presumptive limit for cyclone boilers in this regulation is 56%. Co-sponsoring this project are Eastman Kodak Company and the Gas Research Institute (GRI). Chevron has supplied the natural gas. Equipment installation for the gas reburn system was performed in a September 1995 outage. Boiler No. 43’s maximum continuous rating (MCR) is 550,000 lb per hour of steam flow (or approximately equivalent to 60 MW,). Because of the compact boiler design, there is insufficient furnace residence time to use coal or oil as the reburn fuel, thus making it a prime candidate for gas reburn. Kodak currently has four cyclone boilers. Contingent unon successful comoletion of this eas reburn nroiect. modifi&tion o’f Kodak’s ‘other cyclo;e boilers to include reburn tec’hndlogi will be considered. The paper will describe B&W’s gas reburn data from a cyclone-equipped pilot facility (B&W’s Small Boiler Simulator), gas reburn system design, manufacturing and installation information specific to Kodak’s Unit No. 43. The paper will discuss in addition numerical modelling and the full-scale commercial boiler test results.
An online advisory system using dynamic optimization enables Allegheny power to improve boiler efficiency and control NO,
99101419
Eakle, D. L. et al. EC (Am. Sot. Mech. Eng.), 1997, 5, (l), 45-50. Allegheny Power is installing an on-line operator advisory system at its Harrison power station. The utility desires to improve efficiency at Harrison in order -to compete effectively- in the mark&place established by the Energy Policy Act of 1992. The advisory system utilizes the Ultramax method and dynamic optimization technology known as ULTRAMAX. Allegheny Power decided to proceed with an on-line operator advisory system for Units 1, 2 and 3 following the 1995 optimization of Harrison Unit 2, a Foster-Wheeler opposed-wall boiler fuelled by pulverized coal. Resulting in substantial efficiency gains and demonstrating the viability of integrating ULTRAMAX with the boiler control system was the optimization. The Operator Advisory System will be utilized by Harrison personnel as a support tool for continuous improvement of boiler operations. Offering the opportunity for reducing emissions, lowering fuel costs and responding rapidly and flexibly to changes in operating conditions, compliance regulations and the market environment is the implementing of dynamic optimization as an integrated on-line solution.
99/01420 Overall mathematical model of a circulating fluidized bed boiler and comparison of model predictlons with test results Wang, Q. et al. Gongcheng Rewuli Xuebao, 1998, 19, (2), 251-255. (In Chinese) This paper, based on the previous research work, aimed to develop an overall mathematical model of a circulating fluidized bed (CFB) boiler. The overall model is applied to the simulation of a 75 t/h CFB boiler and the predictions agree well with the performance test results. Operation testing proves that the overall model applies well to CFB boilers.
Possible effects of coal chlorine on furnace wall 99101421 fireside corrosion in utility boilers Mehta. A. K. et al. Corros. Its Control. Proc. Int. Conf. Corros.. 1997 (Pub 1998),‘(2), 1231-1245. Edited by Khanha, A. S. et al. 1 ’ In many pulverized fuel-fired boilers world-wide, fireside corrosion represents-a prominent threat to the integrity of furnace wall tubing. The concern of this paper is to establish the factual basis for the existence of a limitation on chlorine content in coal specifications used by utilities. This
Fuel and Energy Abstracts
March 1999
143
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
Hot corrosion of the steel grades lSChlMF, 13CrMo4-4 and lOCrMoS-10 in a pulverized coal boiler at a metal temperature <540 99101413
Tallermo, H. and Klevtsov, I. VOE Kraftwerkstech., 1998, 78, (8), 105-111. (In German) An experimental investigation of the corrosion of the title substances in chlorine-containing ash deposits of a pulverized coal boiler was carried out. The mechanism of corrosion acceleration in the 12ChlMF steel was analysed for the concentration of chlorine in the outer deposits and the empirical terms for the determination of corrosion depth were identified for all steels.
in-bed recirculation 99101414 circulating fluidized bed boiler
of particle
and design of
He, Q. et al. Ranshao Kexue Yu Jishu, 1998, 4, (l), 69-74. (In Chinese) In recent years, circulating fluidized bed combustion technology has been extensively developed in China. The coal feed size ranges from 2 mm to 3.5 mm resulting in a fluidized bed consisting of a dense and a diluted phase zone. The coal combustion fraction in the dense phase zone is larger, so the heat balance and heat exchange surface area of the dense phase zone are very important. If the heat exchange area is designed too large or not large enough, the circulating fluidized bed boiler can not run stably. This paper analyses the heat balance and conducts the design of heat exchange surface of the dense phase zone for a circulating fluidized bed boiler of 75 t/h steam capacity. Also discussed is the effect of coal type, recirculation ratio of fly ash and coal combustion fraction on amount of heat exchange surface and height of dense phase zone.
The influence of fouling on the heat transfer 99lO1415 characteristics of boiler tubes: a comparison between a numerical simulatlon and an industrial test case Delle Site, C. et al. AES (Am. Sot. Mech. Eng.), 1997, 37, 271-278. A numerical simulation of the effects of fouling on a representative section of the vertical boiler tubes in a pulverized coal boiler for a thermoelectric power plant is presented in this paper. The fouling is here simulated by a uniform coating of solid homogeneous material with average thermal properties derived by experimental data. Both heat transfer modes are simulated in the numerical calculation, that has been performed via a commercial finite-element code, FIDAP of FDI Inc. After a twodimensional numerical test, necessary to calibrate the simulation parameters and to determine a suitable mesh, a fully three-dimensional simulation was carried out. Full account has been taken of the properties of the real fluid and of the real characteristics of its flow. The heat transfer in the coating and in the tube wall has been calculated without introducing heat exchange coefficients, but imposing instead a well-established heat transfer correlation for the boiling water side. Using a modified k-c model, turbulent effects have been simulated. Periodic flow in the vertical direction and forced velocity on the core side have been imposed as boundary conditions. The results of the numerical computation are compared with those of an extensive experimental campaign conducted in 1992 on an industrial boiler for a pulverized coal, 240 MW power plant. It is shown that the numerical results agree verv well with the exuerimental data for the selected test section: it iH therefire proposed to extknd the generality of the numerical simulation to implement and complete the results of future tests on the effects of fouling.
Measurement of the viscosity of coal ashes for the 99101416 analysis of the position of deposits in steam boilers Vaisburd, S. et al. VGB Kruftwerkstech, 1998, 78, (8), 70-73. (In German) At temperatures of 1450-155O”C, the viscosity of ash samples was determined with a high-temperature viscosimeter. The results revealed the viscosity had an exponential dependence on the reciprocal temperature. The activation energy of the viscous ash fusion flow was calculated from this dependence. The results of calculations were found to be valid only if the composition of the ash is comparable with that from which the method of calculation was derived. At various sites of the boiler, the comparison of the temperature with the corresponding ash viscosities can be used to predict the sites of ash deposition.
99101417
The modelina of LEBS-Kalina Dower cvcles
Enick, R. M. et al. PWR (Am. Sot. Mech. Eng.), 7997, 32,12), 55-67. The LEBS (low emission boiler system) is an advanced, pulverized coalfired plant .designed to provide-power in an economic, efficient and environmentally sound manner. Thermal efficiencies of LEBS plants are exoected to be at least 42% HHV (hieher heating value).,I a sienificant \ ikprovement over conventional systems. Two types of working fliids are being considered by DOE contractors developing the LEBS technology, supercritical steam and ammonia-water mixtures used in the Kalina cycle. In this study, a LEBS-Kalina power cycle was modelled. The working fluid composition for the Kalina cycle was 25% water/75% ammonia. A pinch analysis of the plant indicated that the heat exchange network was efficiently designed. Simulations were performed using AspenPlus, a process simulator. The Schwartzentruber-Renon equation of state and the more accurate WATAM program developed by Exergy were used for thermodynamic calculations. An overly optimistic efficiency was obtained when the less accurate thermodynamic model was used. The net plant efficiency of the LEBS-Kalina System 5 plant modelled using WATAM was 41.0% operating at turbine inlet conditions of 1050°F and 2415 psia. In preliminary results, net plant efficiencies greater than 42% were attained for more advanced LEBS-Kalina cycles by incorporating heat exchange networks that were more efficient than System 5. D
NO, control industrial cyclone boiler
99101416
using natural
gas reburn on an
Farzan, H. et al. PWR (Am. Sot. Mech. Eng.), 1996, 30, (2), 835-845. Located in Rochester, New York, Eastman Kodak Company’s cyclone boiler, has been retrofitted with the gas reburn technology developed by the Babcock & Wilcox (B&W) Company to reduce NO, emissions in order to comply with the New York State regulations adopted in conformance with the Title I of the Clean Air Act Amendments (CAAA) of 1990. At the peak load, the ozone non-attainment required NO, reduction from baseline levels necessary to meet the presumptive limit for cyclone boilers in this regulation is 56%. Co-sponsoring this project are Eastman Kodak Company and the Gas Research Institute (GRI). Chevron has supplied the natural gas. Equipment installation for the gas reburn system was performed in a September 1995 outage. Boiler No. 43’s maximum continuous rating (MCR) is 550,000 lb per hour of steam flow (or approximately equivalent to 60 MW,). Because of the compact boiler design, there is insufficient furnace residence time to use coal or oil as the reburn fuel, thus making it a prime candidate for gas reburn. Kodak currently has four cyclone boilers. Contingent unon successful comoletion of this eas reburn nroiect. modifi&tion o’f Kodak’s ‘other cyclo;e boilers to include reburn tec’hndlogi will be considered. The paper will describe B&W’s gas reburn data from a cyclone-equipped pilot facility (B&W’s Small Boiler Simulator), gas reburn system design, manufacturing and installation information specific to Kodak’s Unit No. 43. The paper will discuss in addition numerical modelling and the full-scale commercial boiler test results.
An online advisory system using dynamic optimization enables Allegheny power to improve boiler efficiency and control NO,
99101419
Eakle, D. L. et al. EC (Am. Sot. Mech. Eng.), 1997, 5, (l), 45-50. Allegheny Power is installing an on-line operator advisory system at its Harrison power station. The utility desires to improve efficiency at Harrison in order -to compete effectively- in the mark&place established by the Energy Policy Act of 1992. The advisory system utilizes the Ultramax method and dynamic optimization technology known as ULTRAMAX. Allegheny Power decided to proceed with an on-line operator advisory system for Units 1, 2 and 3 following the 1995 optimization of Harrison Unit 2, a Foster-Wheeler opposed-wall boiler fuelled by pulverized coal. Resulting in substantial efficiency gains and demonstrating the viability of integrating ULTRAMAX with the boiler control system was the optimization. The Operator Advisory System will be utilized by Harrison personnel as a support tool for continuous improvement of boiler operations. Offering the opportunity for reducing emissions, lowering fuel costs and responding rapidly and flexibly to changes in operating conditions, compliance regulations and the market environment is the implementing of dynamic optimization as an integrated on-line solution.
99/01420 Overall mathematical model of a circulating fluidized bed boiler and comparison of model predictlons with test results Wang, Q. et al. Gongcheng Rewuli Xuebao, 1998, 19, (2), 251-255. (In Chinese) This paper, based on the previous research work, aimed to develop an overall mathematical model of a circulating fluidized bed (CFB) boiler. The overall model is applied to the simulation of a 75 t/h CFB boiler and the predictions agree well with the performance test results. Operation testing proves that the overall model applies well to CFB boilers.
Possible effects of coal chlorine on furnace wall 99101421 fireside corrosion in utility boilers Mehta. A. K. et al. Corros. Its Control. Proc. Int. Conf. Corros.. 1997 (Pub 1998),‘(2), 1231-1245. Edited by Khanha, A. S. et al. 1 ’ In many pulverized fuel-fired boilers world-wide, fireside corrosion represents-a prominent threat to the integrity of furnace wall tubing. The concern of this paper is to establish the factual basis for the existence of a limitation on chlorine content in coal specifications used by utilities. This
Fuel and Energy Abstracts
March 1999
143
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