air flames diluted by additions of inert solid particles

air flames diluted by additions of inert solid particles

09 piston is cycled in the cylinder by using an electric motor driven hydraulic ram. Ignition is started by an exeimer laser beam focused into a comb...

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piston is cycled in the cylinder by using an electric motor driven hydraulic ram. Ignition is started by an exeimer laser beam focused into a combustion chamber. Conventional electric spark ignition is used as a basis for comparison between the two different ignition methods and the resultant early breakdown kernel characteristics. The initial stages of kernel formation were recorded by a streak camera. Results indicate that only used for producing laser ignition produce a radial certain wavelengths expansion wave. Laser ignition kernel size is calculated and laser-supported breakdown velocity is calculated by using Raizer’s theory and is compared with measured results. 99lO2284

Mathematical

model for single pulverized

coal

combustion Chen, Y. et al. Gangtie Yonjiu Xuehao, 1997, 9, (3), l-5. (In Chinese) Simulation of the combustion of single pulverized coal particle was achieved in a mathematical model. It is used for predicting the burning rate, burning time and the burning temperature in different conditions for different coal particle size. The surface temperature of pulverized coal particles change with the burning time and the relation between burning rate, burning time and diameter of pulverized coal particle and the distribution of gas composition and temperature in the thin film around the pulverized coal particle were obtained. Coal burning rate for large scale pulverized coal injection in blast furnaces can also be determined with the model.

Modelling sulfur dioxide capture in a pulverized coal combustor

99lo2295

Nair, R. B. and Yavuzkurt, S. /. Ena. Gas Turbines Power, 1997, 119, (2), 291-297. Investigates sulfur dioxide formation and capture in a pulverized coal combustor. A two-dimensional, steady, axisymmetrical code, PCGC-2 (pulverized coal gasification and combustion-two dimensional), originally developed at Brigham Young University, has been used to simulate combustion of the pulverized coal. This paper represents part of a project to simultaneously investigate the enhancement of both sulfur capture and particulate agglomeration in combustor effluents. Results from the code have been compared to experimental data obtained from MTCI’s (manufacturing technology and conversion international) test pulse combustor, which generates sound pressure levels of -180 dB. The overall goal behind the pulse combustor program at MTCI is the development of combustors for stationary gas turbines that use relatively inexpensive coalbased fuels. An attempt to simulate the capture of sulfur dioxide when injected into a pulse combustor firing micronized coal and the effects of the acoustic field are expressed by increased heat and mass transfer to the particles in question. A comprehensive calcination-sintering-sulfation model for single particles was used to model the capture of sulfur dioxide by limestone sorbent. The model was incorporated into the PCGC-2 programme. Comparisons of exit concentrations of SOz agreed quite well with the experimental results from MTCI.

A multi domain method for the simulation pulverized coal fired multiburner furnaces

98102286

of

Jacobson, T. Rep. TKK-V-B, 1995, (TKK-V-B104, Proceedings of the 2nd Colloquium on Process Simulation, 1995), 39-63. The modelling of the near burner region has a very significant role in the furnace simulations, particularly for large multiburner furnaces where the chemical reactions, important to combustion and formation of emissions, take place in relatively small region. The modelling of the near burner region is essentially improved by refining the grid locally, but only by a moderate increase in the grid size and computational time. The MultiDomain Technique (MDT) is used to achieve local refinement. This technique is where the calculation region is divided into the main domain and several sub-domains. MDT allows the use of different physical submodels and solution parameters in each domain. For calculation of the radiative heat transfer the discrete transfer method has also been applied to MDT. MDT has been tested for a gaseous and pulverized coal combustion in tangentially fired 600 MW furnace. In MDT simulations the furnace was divided into four burner zones and one main domain. A more detailed analysis of the results has as yet been made only for gaseous combustion while the simulation results with particles is shown to demonstrate the capabilities of the technique. In all cases, the convergence behaviour of MDT was very satisfactory.

A new combustion stability Index CSI for utility coal-fired boilers

98/02207

Cheng, R. et al. Gongcheng Rewuli Xuebao, 1997, 18, (4) 512-516. (In Chinese) The review discusses the shortage of the general suitability of some existing assessment methods for relative combustion stability, and proposes a new combustion stability index (CSI) for utility coal-fired boilers, based on the concepts of BIB0 stability theory. CSI was measured by the maximum disturbance ratio of fuel mass flow rate which can be overcome by stable combustion process. A combustion process with CSI being zero or one corresponds to the lowest or highest combustion stability, respectively. The results of dynamic combustion simulation on a utility boiler and experiments on two types of burner in a laboratory-scale single-burner furnace have proved initially the effectiveness of CSI. After assessing the relative combustion stability of industrial combustion processes, it is likely that a comprehensive method will be established.

Combustion

(burners, combustion

systems)

Operation of combustion plant of coal-fired power station with slag tap flrlng

98102299

Hums, E. et al. PCT Int. Appl. WO 97 11,139 (Cl. ClOL9/10), 27 Mar 1997, DE Appl. 19,534,558, 18 Sep 1995, 26 pp. (In German) A combustible material content of 550% is found in the flue dust conveyed by the flue gas in a combustion untt of a coal-fired power plant. To attain high efficiency by complete combustion, the flue dust is recycled to the combustion chamber and residence time of coal or dust particles in the firing circuit is increased. To accelerate the full combustion, a titaniumcontaining material is added to coal and a spent TiOa-based catalyst from NO, removal is typically used as the combustion catalyst. The TiOz/coal ratio is <3:97. The fuel throughput and efficiency of the power plant are thus increased. 99lO2289

PFBC: Competitive power with minimal envlronmental Impact. Practical experience

Anderson, J. and Anderson, L. Inst. Chemical Eng. Symp. Ser., 1997, 143, 73-80. Developed by ABB, this PFBC (Pressurized Fluidized Bed Combinedcycle) technology is fast establishing itself as a competitive option for clean, efficient power generation from a wide range of solid fuels. PFBC plants have been put into operation in Europe, the United States and Japan over the last decade and the first generation of P200 (-75 MW) plants have so far achieved almost 90,000 h of operation. They have also provided valuable feedback on performance and operation. In addition to a further P200 currently under construction in Germany, the first utility size 360 MWe PFBC plant is now being built for Kyushu Electric Company in Japan. The combined-cycle arrangement provides a high thermal efficiency in the generation of power from coal. Excellent environmental control is offered by the use of a fluidized bed, with sulfur removal of up to 99% and inherently low NO, emission levels. PFBC has been demonstrated to allow fuel cost advantage to be combined with high efficiency and excellent environmental performance. An overview of the current status of ABB’s PFBC technology is presented, describing experience from plants in operation and under construction.

Propagation limits of dust/air flames diluted by additions of inert solid particles

9Blo2290

Blouquin, R. and Joulin, G. Symp. (I&.) Combust., /Proc./, 1996, 26, (I), 1565-1570. This work considers flames that propagate by radiation and Arrhenius heterogeneous chemical in two-phase premixtures consisting of a combustible dust, an oxidizer-containing gas and an inert dispersed solid that acts as a diluent. The focus lies on steady propagations inside tubes and on the propagation limits. The main assumptions are that (1) the reaction rate is strongly temperature dependent; (2) molecule transports are negligible; (3) radiation follows the Eddington approximation specialized to a grey medium; (4) the Boltzmann number is large; (5) the tubes have an O(1) transverse optical thickness; and (6) the tube walls act as imperfect mirrors and Kirchoff’s law holds. Radiant exchanges between wall and particles are then well approximated by bulk heat losses and the problem is quasi-one dimensional. Using asymptotic techniques followed by a shooting method the burning speed was obtained. Contrary to the case of fully combustible dusts, it is predicted that lean flames may exist in tubes that are wide enough, despite the increased heat capacity and reduced radiative conductive due to the inert particles. It is also postulated that an increase in the heat-loss level quenches the stoichiometric flames first, despite the high reaction temperature, due to a local increase in effective overall reaction order. In the absence of a flame, the burning-speed vs equivalence ratio curves are similar to (yet slightly lower than) those of non-diluted flames. In tubes that are too narrow or poorly-reflecting, no propagation is allowed.

98/02291 Pyrolysis of coals of various degrees of metamorphism in the presence of hydroxldes and acid Tamko, V. A. and Shevkoplyas, V. N. Khim. Tverd. Topl., 1996, (6), 43-50. (In Russian) The paper studies the effect of HCI, KOH, and Ca(OH)z on the pyrolysis of low-and medium-rank coals. The treatment was conducive to the rate and degree of conversion of organic matter to liquid and gas products. The nature of the coal, the type of chemical used and the pyrolysis conditions determined the low-molecular-weight product yield. The effect of inorganic substances on the strength of semi-coke and coke was shown.

The role of porosity and surface area in carbon combustion and gasification

98/02292

Aarna, I. and Suuberg, 159-162. 98102293

E. M.

Chemical Physical Processes Cornbust., 1997,

Solid fuel products

free of slag formation

in

combustion Drisdelle, M. and Lapointe, C. Can. Pat. Appl. CA 2,156,OlO (Cl. ClOL5/ 44) 15 Feb 1997, Appl. 2,156,010, 14 Aug 1995, 22 pp. Homogeneously blended PO.025 wt% additive in biomass increases the fusion temperature of the slag forming substances that may be present in the biomass above the temperature in a combustion chamber when burning the biomass. Thus, no slag is formed in the combustion chamber and the impurities accumulated as friable ash can easily be discarded. The additive comprises metal oxides, the mixture of which also includes NH,,NOs.

Fuel and Energy Abatfects

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