09 Combustion (burners, combustion systems) 00103575 Modelling of combustion of low grade lignites in fluidized beds with heat extraction Mancuhan , E. and Ozyl, E. Proc. Inr. Conf. Nrlid. Bed Comhusf., 1999. IZI- 139. In this project, a computerized model was developed for any low rank coal with a known particle size distribution and mass fraction. When the coal is fed into the bed, the volatile matter is assumed to be released instantaneously and a new particle size distribution is achieved within the bed. The effect of elutriation and chemical reactions are also taken into account. The effect of excess air on elutriation, particle size distribution of the semi-coke and the mass fraction values within the bed at steady-state conditions is examined The excess air ranged from 1 to 1.48. It also takes into account the effect of coal type on the bed-temperature, which, as is already known, may vary significantly from type to type in the low quality coal range, much more than the high quality coal types. The results of the model simulation studies are compared with a limited amount of experimental work available for Turkish lignites and the agreement between the model prediction and the experimental data is reasonably good. Closer to distributor plate the bed temperature prediction, of the model is low, but agreement improves as the active bed surface is reached. The results obtained from the model are presented for the feed air temperatures of 300, 400 and 500 K for Seyitomer lignite. If 60% of the desired heat is extracted from the active bed the optimum results can be obtained. 70% of the volatile matter is burnt within the active bed and the remainder in the freeboard in optimum conditions. 00103576 NO, reduction by air staging and reburning Hesselmann, G. er al. Eur. Comm., [Rep./ EUR, 1999, l-89. In this study, coal combustion by air staging or natural gas reburning for reduced NO, formation was examined for three coals. For single-stage, NO, formation increases linearly with excess 02, and losses of unburned coals increased with decreasing excess air and sharply increases at low oxygen availability. For furnace air staging, NO, is linearly dependent on excess Oz but the sensitivity was less than for single-stage combustion. Unburned losses followed the same trends as for single-stage combustion but were significantly higher. NO, levels decreased sharply as primary zone stoichiometry decreased from air-rich to fuel-rich, with an optimum at ~0.9. For natural gas reburning, a lower reburn zone stoichiometry leads to reduced NO, emissions, with an optimum at -0.85-0.9. Burnout is relatively insensitive to reburn zone stoichiometry. It was found that coal quality is less important a factor in natural gas reburning systems. 00103577 Numerical simulation of turbulent propane-air combustion with nonhomogeneous reactants Haworth, D. C. er al. Comhus~ion and Flame, 2000, 121, (3). 395-417. High-resolution two-dimensional numerical simulations have been per- formed for premixed turbulent propane-air flames propagating into regions of non-homogeneous reactant stoichiometry. Simulations include complex chemical kinetics, realistic molecular transport, and fully resolved hydrodynamics (no turbulence model). Aerothermochemical conditions (pressure, temperature, stoichiometry and turbulence velocity scale) approach those in an automotive gasoline direct-injection (GDI) engine at a low-speed, part-load operating condition. (Salient findings are as follows: (1) There is no leakage of the primary fuel (propane) behind an initial thin premixed heat-release zone. This ‘primary premixed flame’ can be described using a monotonic progress variable and laminar premixed flamelet concepts. (2) For the conditions simulated, differences in global heat release and flame area (length) between homogeneous and non- homogeneous reactants having the same overall stoichiometry are small. (3) Beyond three-to-four flame thicknesses behind the primary flame, practically all hydrocarbon fuel has broken down into CO and Hz. (4) The rate of heat release in the ‘secondary reaction zone’ behind the primary premixed flame is governed by turbulent mixing and the kinetics of COz production. Mixture-fraction-conditioned secondary heat release, CO, and CO* production rates are qualitatively similar to results from a first-order conditional moment closure (CMC) model; CMC gives poor results for Hz, HzO, and radical species. Description of the secondary heat release using steady laminar diffusion flamelet concepts is problematic. (5) Of the chemical species considered, HCO mass fraction or the product of CHzO and OH mass fractions correlates best with local heat-release rate. (6) Computational considerations demand modifications to chemical mech- anisms involving CsH, and CHsCO. Specific changes are proposed to strike a satisfactory balance between accuracy and computational efficiency over a broad range of reactant stoichiometry. 00/03578 Principles and practice of biomass fast pyrolysis processes for liquids Bridgwater, A. V. J. Anal. Appl. Pyolysis, 1999, 51, (l-2), 3-22. In Europe, the fast pyrolysis of biomass is of rapidly growing interest as it is perceived to offer significant logistical and hence economic advantages over other thermal conversion processes. This is because the liquid product can be stored until required or readily transported to where it can be most effectively utilized. The objective of this paper is to review the design considerations faced by the developers of fast pyrolysis as well as the upgrading and utilization processes in order to successfully implement the technologies. Design aspects of a fast pyrolysis system include feed drying, particle size, pre-treatment, reactor configuration, heat supply, heat transfer, heating rates, reaction temperature, vapour residence time, secondary cracking, char separation, ash separation and liquids collection. This paper reviews and discusses each of these aspects. 00103579 Process and apparatus for pyrolysis of carbonaceous feedstocks Hiltunen, .I. ef al. PCT Int. Appl. WO 99 43,768 (Cl. CIOJ3/54), 2 Sep 1999. FI Appl. 1998/456, 27 Feb 1998. 22. A process and apparatus for the thermal conversion of biomass and organic wastes have been invented. The feedstock is fed into a fluidized-bed reactor, wherein the feed is converted at an elevated temperature under the influence of particulate matter held in a fluidized state by a fluidizing gas, the particulate matter is transferred from the reactor to a regenerator for regeneration and then recirculated to the reactor after the regeneration, and the converted hydrocarbon products are recovered from the reactor. Both the reactor and the regenerator comprise risers having an axially annular cross section and being equipped with multi-inlet cyclones for separation of particulate matter. It is possible to produce pyrolysis oil, the quality of which is higher than that of oil produced with the conventional processes. The incorporation of multi-inlet cyclones into the reactor configuration decreased gas velocities, reduced the physical size of the cyclone, and shortened the residence time of gases in the cyclone. 00103580 Pyrolysis and hydropyrolysis of a Turkish lignite under high pressure Canel, M. Wiss. Ber. - Forschungsrent. Karlsruhe. 1999, 137-140. A Turkish lignite was both pyrolysed and hydropyrolysed in nitrogen and hydrogen atmospheres in a flow through reactor. The influence of an ambient gas atmosphere (inert, reactive) and the pressure on the yield of products have been investigated. The yield of liquid and gas products is significantly influenced by the type of gaseous atmosphere. The tar and gaseous products obtained by hydropyrolysis are greater than those obtained by pyrolysis under the same conditions. The tar yield in hydropyrolysis increased substantially as 1 he pressure increased. An increase of pressure for both pyrolysis and hydropyrolysis leads first to an increase in the yield of gaseous products than a decrease at high pressures. As a result of the reaction of char with the Hz gas existing m the reactor in hydropyrolysis the amount of CHI and CzH6 present in the gaseous products is substantially higher than those existing in pyrolysis. Hydro- pyrolysis obtained higher formation rates of tar and total gaseous products than by ordinary pyrolysis. 00103581 Pyrolysis kinetics of blends of Tuncbilek lignite with Denizli peat, Turkey Guldogan, Y. e/ nl. Thermochim. Acra, 1999, 332, (I), 75-81. The pyrolysis of Tuncbilek lignite and Denizli peat and several peat-lignite blends took place in a thermobalance apparatus at atmospheric pressure. Experiments were carried out dynamically by increasing the temperature from 25 to 900°C with a heating rate of 20’C/min under an argon atmosphere. Differential thermogravimetric data were analysed by a reaction rate model assuming first-order kinetics. The effect of the blending ratio of peat and lignite on the pyrolysis kinetics was investigated and the kinetic parameters were determined and the results discussed. 00/03582 Pyrolysis of coals and lube oil wastes in a bench- scale unit Lazaro, M. J. et al. Energy Fuel.~, 1999, 13, 14), 307.-913. A lube oil waste (LOW) and two coals have been co-pyrolysed. The main objective of this study is to compare product yields from the co-pyrolysis with those obtained in the pyrolysis of coal and LOW alone. The influence of temperature, pressure, and coal nature on the yields obtained has been studied. The work has been carried out at a bench-scale using mixtures of coal and LOW in a mass ratio of 50150. Three temperatures, 600, 650, and 700°C and three pressures 0.1,0.5, and 1 MPa have been studied. Two coals largely differing in rank have been used in order to state the influence of coal nature. Occurrence of synergetic effects on some products has been observed which confirms that co-pyrolysis of LOW and coal as a mixture enhances the transfer of coal hydrogen to valuable petrochemical products that otherwise would be transferred to molecular hydrogen if coal was pyrolysed alone. Comparing the theoretical values with the real ones, there is a synergy in the hydrogen transferred to CH4 and light alkanes, ethylene, and propylene that increases as temperature increases and the Hz transferred to > Cq compounds does not reveal synergy. However, for the hydrogen transferred to BTX, the theoretical values remain similar to the actual ones. The synergy in the hydrogen transferred to CHI and light alkanes increases with pressure, and also the Hz transferred to BTX. However, pressure does favour the synergy in the hydrogen transferred to BTX. The effects observed for the Figaredo coal are lower than for the Samca coal/LOW, but the same considerations do apply to both coal/oil mixtures. 00/03583 Pyrolysis of oil shales: influence of particle grain size on polycyclic aromatic compounds in the derived shale oils Williams, P. T. and Nazzal, J. M. J. Inst. Energy, 1999, 72, (491). 48-55. Oil shales of different particle grain sizes were pyrolysed in a 10 cm diameter x 100 cm high fluidized-bed reactor under both a nitrogen and a steam atmosphere. The oil shales were from the Kimmeridge clay of Jurassic age in the UK. The influence of particle grain size on the yield and composition of the oil and gases was determined. Analysis of the gases took Fuel and Energy Abstracts November 2000 401