05202 Behavior of coal ash in combustion and gasification processes

05202 Behavior of coal ash in combustion and gasification processes

09 Heat transfer characteristics in a small-scale fluid96105193 ized bed boiler Tia, S. er al., Inr. J. Energy Research, Jun. 1996, 20, (6), 521-530...

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Heat transfer characteristics in a small-scale fluid96105193 ized bed boiler Tia, S. er al., Inr. J. Energy Research, Jun. 1996, 20, (6), 521-530. Heat transfer characteristics in a small-scale fluidized bed boiler were studied using lignite and corn cob as fuels. Depending on air velocity, the heat transfer rates from bed to water membrane wall and from hot flue gas to convective tube bank were in the ranges 75-55% and 25-45% of the total heat absorbed by the boiler, respectively. At designed capacity, the heat transfer flux based on bed cross sectional area and on water membrane wall area were about 0.45 and 0.15 MW m.2, respectively. Under the conditions studied, it was found that the overall heat transfer coefficient between bed and water membrane wall was 100-300 Wm“ K“, whereas the between flue gas and convective tube bank was lo-30 Wm’* K.‘. The study of heat transfer to a horizontal tube immersed in the bed as well as placed in the freeboard region were also studied.

Combustion

96/05199 Atmos herlc fluldlzed bed combustion of hlgh sulfur high volatile N. If . Region coals of India Borah, R. C. et al., Res. lnd., 1995, 40, (4), 315-321. Sulphur capture by limestone as well as combustion characteristics of the coals were studied in a 0.67 m2 cross-sectional area fluidized bed combustor (10 t/h hot water capacity). Flue gas was monitored continuously with online gas analysis system. 96105200 An automatic control system for clean coal combustion on a chain-grate stoker Neuffer, D. er al., Coal Sci. Technol., 1995, 24, (l), 559-562. In order to evaluate modern control methods process model has been developed to describe the behaviour of a IMW chain-grate stoker. 96/05201 Basic coal science. Ill. Coal liquefaction and reaction mechanism Nagaishi, H. Nippon Enerugi Gakkaishi, 1996, 75, (l), 49-55. (In Japanese) Discusses the purpose apparatus, mass transfer, and reaction mechanism of coal liquefaction.

09 COMBUSTION Burners,

Combustion (burners, combustion systems)

Systems

96105194 Advanced power systems and coal quality Scott, D. and Carpenter, A. IEA Coal Research, Gemini House, lo-18 Putney Hill, London SW15 6AA, IEACRI 87, f300. (non-member countries) f 100. (member countries), May 1996. The report reviews the effects of coal quality on the design, performance and availability of advanced electric power generating systems, namely: supercritical pulverised coal fired boilers (supercritical PC), fluidised bed combustors and integrated gasification combined cycle (IGCC).

96105195 The amounts of NO, and N,O formed in a fluidized bed combustor during the burning of coal volatiles and also of char Hayhurst, A. N. and Lawrence, A. D. Combusnon & Flame, May 1996, 105, (3), 341-357. Three quite different coals were burned batchwise in electrically heated beds of sand fluidized with O2 and N2 at either 800 or 900°C. The coal was injected into the bed either as a single piece (1 or 2 cm in size) or as 1.0 g batches of smaller particles either 1.4-1.7 or 2.0-2.4 mm in diameter). The concentration of NO, (i.e., t NO]+ [NC?,]), N,O, CO, and CO, in the offgases were measured as functions of time whilst the coal was burning. It proved relatively easy to separate the emission of any one of these gases into that from the initial, devolatilization stage of combustion and that from the subsequent burning of the char. Application of front tracking techniques to the tur96105196 bulent combustion processes in a single stroke device Bielert, I-!. et al., Combusfion & Flame, Jul. 1996, 106, (l), 11-28. A numerical model for the simulation of turbulent combustion processes has been developed that employs front tracking techniques originally designed for thin laminar flames and extends these techniques to turbulent reaction zones of finite thickness. The main features of the model are a two dimensional calculation of the propagation of the combustion zone and the pertient flow field and a two-zone model for the temperature, pressure and composition. For the turbulent burning velocity an expression is established which describes its development with time in the inilial stage of combustion and its approach to a sleady state value. Application of rate-ratio asymptotics of the predic96105197 tion of extinction for methanol droplet combustion Zhang, B. L. et al., Combustion & Flame, May 1996, 105, (3), 267-290. Asymptotic methods are employed to describe the flame Structure and extinclion of quasisteady, spherically symmetrical diffusion flames around methanol droplets. Starting with a short mechanism involving 14 steps, five of which are reversible, sequentially reduced overall descriptions of four. three, and two steps are obtained by investigating the character of the deparlure of the H atom and its associated radicals from steady stales and by demonstrating in agreement with earlier work that, conrrary to hydrocarbon flames, water-gas equilibrium is an excellent approximation in the reaclion zones of these methanol flames. An appropriate kinetic model for well-preserved 96105196 algal kerogens Burnham, A. K. ef al., Energy Fuels, 19Y6, 10, (l), 49-59. Alrhough the broadness of the pyrolysis profile of most kerogens is usually described well by a parallel reaction model, the pyrolysis profile at conStan1 heating rate for certain well-preserved algal kerogens is narrower than can be described by a single first-order reaction. Further, these kerogens show an acceleration period under isothermal conditions that is inconsistent with any parallel or nth-order reaction model. Three different models (serial, Bouster, and three-parameter) were tested against isorhermal and nonisothermal pyrolysis dala for a few samples, with the conclusion thal the three-parameter model fits well and is the most stable and reliable.

Behavior of coal ash In combustion and gaslflca96105202 tion processes Kojima, T. and Bi, J. Nippon Enerugi Gakkaishi, 1996, 75, (l), 28-34. (In Japanese) Discusses coal ash behaviour in combustion and gasification processes. The effects of elements such as Na, S, Fe, Si,Al and the corresponding compounds contained in ash on the ash melting, sintering or agglomeration and slagging were discussed. 96105203 Build-in slag crusher in coal gasifier Tanaka, MI. et al., (Assigned IO) Mitsubishi Heavy Industries Ltd., JAP. Pat. JP.O7,24?,283, Sep. 1995. To avoid slag accumulation, the slag crusher consists of a pair of hydraulic jacks with a rod with, on its end, a spreader arranged with gears for crushing of falling slag. 96105204 Burner development moves to another stage MPS, Modern Power Systems, Jun. 1996, 16, (6), 67, 69-70. Reports that following almost a decade of development, Mitsui Babcock is now working on the next stage in the development of its low NO, axial swirl burners. Burners of domestic heating boilers: A measure96105205 ment-based analysis approach almlng at quantlfylng correlations among the basic parameters of operation Karagiannidis, A. Energy Cowers. Mgmt., Apr. 1996, 37, (4), 447-456. The work presents an analysis of the results from a flue-gas measurement programme on diesel-oil domestic heating boilers, conducted in a Hellenic urban area, aimed at the quantification of the correlation between the basic parameters affecting the operation of their burners. Calculation of heat transfer Blot number of oil 96105206 shale particles during fluidized-bed combustion Wang, G. et al., Shlyou Daxue Xuebao, Ziran Kexueban, 1995, 19, (3), 114-116. (In Chinese) Discusses how the temperature gradients with a solid particle may be assessed with the aid of heat tranfer Biot number. The Biot number of oil shale particles during fluidized bed combustion which includes oil shale devolatization and shale char combustion was calculated. Calculation of steady-state operation characterls96105207 tics of fluidized bed coal combustors Eskin, N. and Kilic, A. Bull. Tech. Univ. Istanbul, 1995, 48, (l), 11-36. Describes the development of a comprehensive model for the simulation of fluidized bed coal combustors (FBCC) that was developed and the steadystate operational characteristics estimated on the basis of operational characteristics of a process simulation consisting of combustor model, balance equation and algorithms. Catalytic abatement of emissions from small-scale 96/05206 combustion of wood. A comparison of the catalytic effect In model and real flue gases Carno, J. er al., Fuel, Jun. 1996, 75, (8), 959-965. The aim of this study was to evaluate a laboratory technique for testing catalysts, as well as to investigate two commercial catalysts, for total oxidation of unburnt hydrocarbons and CO in flue gases from wood combustion. The catalyst activities for oxidation of methane, naphthalene and CO in the presence of steam and carbon dioxide were measured in a laboratory flow reactor and the activity for oxidation of methane C, hydrocarbons, benzene and CO in real flue gases was analysed in a 15 kW wood-fired healer. The results from the two investigations were compared to verify whether the laboratory method is a useful tool to simulate catalytic oxidation of the flue gases.

Fuel and Energy

Abstracts

September

1996

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