Coal combustion process

Coal combustion process

09 Combustion (100% MBM inclusion) for the first series of pellets. Increasing compaction pressure increased the residence time. For the second series...

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09 Combustion (100% MBM inclusion) for the first series of pellets. Increasing compaction pressure increased the residence time. For the second series of pellets, the residence time varied from about 300 s (25% MBM inclusion) to 100 s (100% MBM inclusion). MBM was found to be a volatile product (about 65%) and co-firing it with milled peat in a pellected feed format reduces its volatie intensity. Pellets made from 100% bone based meal remained intact within the bed and are thought to have undergone a process of calcination during combustion. A maximum MBM inclusion rate of 35% with milled peat in a pellet is recommended from this work. 02/01041 Biomass-coal jet cofiring Alekhnovich, A.N. er crl. Teploenerge/ika ~Moscon’~. 2001, 2, 26-33. (In Russian) Cofiring of biomass with coal in coal-pulverizing power plant boilers was investigated. Results of experimental investigation of jet combustion of wastes from milling production in mixture with coal, carried out in a testing unit, are presented. Problems of grinding, combustion, slagging properties, corrosion, and emissions of harmful gaseous substances are analysed. 02/01042 Coal combustion process Wachendorfer, P. U.S. US 6,216,613 (Cl. 110-347; F23B7/00, 17 Apr 2001, US Appl. 897,939, 21 Jul 1997. 11. A process for solid fossil fuel oxidation that utilizes a refractory that defines a reactor core and a combustor chamber in serial communication. The reactor core is heated by burning an air-fuel mixture external to the reactor core. A non-oxidizing gas/coal mixture is introduced into the reactor core where heat energy is transferred to the non-oxidizing gas/coal mixture so that the specific heat of the mixture is substantially raised. The non-oxidizing gas/coal mixture is discharged from the reactor core into the combustor chamber at which point an oxidizing medium such as air is introduced to instantly oxidize the heated non-oxidizing gas/coal mixture. The non-oxidizing gas may be a flammable gas, such as methane. 02/01043 Coke quality requirements for blast furnaces Cheng, A. Iron Sieelmuker, 2001, 28, (I), 30-32. In a first part the principle processes in a blast furnace are outlined, describing the reduction of iron oxides by CO to metallic Fe. The principle fuel of a blast furnace was coke, but in some cases it was replaced by coal, oil or gas, and beside iron ore and coke fluxes were added to achieve a liquid slag. The zones within a blast furnace are described. In general a blast furnace was a two-stage reactor with a low temperature zone where the ducts were dried, devolatilized, preheated and a iron oxides were reduced to wustite, while in the high temperature zone the reduction of wustite to Fe occurred simultaneously with the melting of the metal and the slag. 02/01044 Comparison of products from the pyrolysis and catalytic pyrolysis of rice husks Williams, P.T. and Nugranad, N. Energy /O.~fcjrd], 2000, 25, (6), 493513. Rice husks were pyrolysed in a fluidized bed reactor at 400, 450, 500, 550, and 600”. The rice husks were then pyrolysed at 550” with zeolite ZSM-5 catalyst upgrading of the pyrolysis vapours at catalyst temperatures of 400, 450, 500, 550, and 600”. The pyrolysis oils were collected in a series of condensers and cold traps and analysed to cletermine their yield and composition in relation to process conditions. The gases were analysed off-line by packed column gas chromatography. The pyrolysis oils before catalysis were homogeneous, of low viscosity, and highly oxygenated. Polycyclic aromatic hydrocarbons (PAHs) were present in the oils at low concentration and increased in concentration with increasing temperature of pyrolysis. Oxygenated compounds in the oils consisted mainly of phenols, cresols, benzenecliols, and guaiacol and their alkylated derivatives. In the presence of the catalyst the yield of oil was markedly reduced, although the oxygen content of the oil was reduced with the formation of coke on the catalyst. The influence of the catalyst was to convert the oxygen in the pyrolysis oil to largely Hz0 at the lower catalyst temperatures and to largely CO and COz at the higher catalyst temperatures. The molecular weight distribution of the oils was decreased after catalysis and further decreased with increasing temperature of catalysis. The catalysed oils were markedly increased in single-ring aromatic hydrocarbons and PAHs as compared to uncatalysed btomass pyrolysis oils. The concentration of aromatic and polycyclic aromatic species increased with increasing catalyst temperature. 02/01045 Effect of lignite properties on reactivity of lignite Kiiciikbayrak, S. er al. Energy Conversion und Manogernent, 2001, 42, (5), 613-626. The purpose of this study is to relate the combustion reactivity of lignite to its physical and chemical properties. Non-isothermal thermogravimetry, where the sample whose temperature increased at a linear rate (40 kimin) was heated in air, has been used to investigate

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the combustion reactivities of 25 lignite samples originating from different areas of Turkey. Since combustion reactivity is affected by the chemical and physical properties of coal, the combustion reactivity of the lignites used in this study was related to their proximate and ultimate analysis results and physical properties such as pore structure and surface area. The calculated activation energy values for the combustion reactions of the lignites ranged between 64 and 139 kJ/mol. Definite correlations between the activation energy values and the above-mentioned properties were found.

02/01046 Flow-field Effects on Soot Formation in Normal and Inverse Methane-Air Diffusion Flames Kaplan, C.R. and Kailasanath, K. Comhusrion umi Flame, 2001, 124, (I/ 2) 275-294. The effects of the flow-field configuration on the sooting characteristics of normal and inverse coflowing diffusion flames were investigated. The numerical model solves the time-dependent, compressible, reactive-flow, Navier-Stokes equations, coupled with submodels for soot formation and thermal radiation transfer. A benchmark calculation is conducted and compared with experimental data, and shows that computed peak temperatures and species concentrations differ from the experimental values by less than lo%, while the computed peak soot volume fraction differs from the experimental values by lO40%, depending on height. Simulations are conducted for three normal diffusion flames in which the fuel/air velocities (cm/s) are 5110, 10110, and 10/5, and for an inverse diffusion flame (where the fuel and air ports have been reversed) with a fuel/air velocity of lO/lO. The results show significant differences in the sooting characteristics of normal and inverse diffusion flames. This work supports previous conclusions from the experimental work of others. However, in addition, the ability of the simulations to numerically track soot parcels along pathlines to further explain the experimentally observed phenomena were used. In normal diffusion flames, both the peak soot volume fraction and the total mass of soot generated is several orders of magnitude greater than for inverse diffusion flames with the same fuel and air velocities. In normal diffusion flames, soot forms in the annular region on the fuelrich side of the flame sheet, while in inverse flames, the soot forms in a fuel-rich region on top of the flame sheet. Surface growth is the dominant soot formation mechanism (compared to nucleation) for both types of flames; however, surface growth rates are much faster for normal diffusion flames compared to inverse flames. Soot oxidation rates are also much faster in normal flames, where the dominant sootoxidizing species is OH, compared to inverse flames, where the dominant soot-oxidizing species is Oz. In the inverse flame, surface growth continues after oxidation has ceased, causing the peak soot volume fraction to be sustained for a long period of time, and causing the emission of soot, even though the quantity of soot is small. Comparison of soot formation among the three normal diffusion flames shows that the peak soot volume fraction and total mass of soot generated increases as the fuel-to-air velocity ratio increases, A larger fuel-air velocity ratio results in a longer residence time from the nucleation to the oxidation stage, allowing for more soot particle growth. When the fuel-to-oxidizer ratio decreases, there is less time for surface growth, and the particles cross the flame sheet (where they are oxidized) earlier, resulting in decreased soot volume fraction.

02/01047 Fuelwood characteristics of some indigenous woody species of north-east India Kataki, R. and Konwer, D. Biomrrss and Bioenergy, 2001, 20, (I), 17-23. Wood energy is identified as the major source of energy in rural India and this has necessitated the identification of suitable tree species that can be included in energy plantation programme. As a preliminary to a more detailed future study of wood energy plantation, four indigenous perennial tree species, namely Albizzia lucida, Syzygium fruticosum, Pterospermum lanceaefolium and Premnu hengcrlensi.~ growing in their natural habitat of north-east India were collected for fuelwood characterization studies. Various physico-chemical properties, viz. moisture and ash content, density, solubility in cold water, hot water and alkali, cellulose, holocellulose, lignin and extractive contents of different parts of these species were determined on ash-free dry weight and extractive-free dry weight basis to find out relationship, if any, between ash and extractive content with the calorific value. In all the species. leaf component contained the highest calorific value presumably because of the presence of extractives in higher amount, followed by heartwood. Elimination of ash from the plant parts increased calorific value while extractive-free materials declined in net caloric content in all plant parts, indicating a possible relationship of these two parameters with the heat of combustion. This study concludes that A. htciclrr. S. .fruricosrmt and P. lunceucfoiium have better fuelwood properties and can be considered for inclusion m the energy plantation programme of north-east India. ’ Fuel and Energy Abstracts

March 2002