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This paper presents a model for group combustion of a cylindrical stream of coal particles and preliminary experimental data. Results are obtained for transient ignition and combustion behaviour. It is found that homogeneous ignition (ignition of volatiles) occurs for a dense cloud, while heterogeneous ignition (ignition of carbon) occurs for a dilute cloud. Once ignited, the flame moves towards...
The influence of coal rank, maceral composition, particle size, pressure, temperature and heating rate on the ignition of single coal particles was studied with a heated-grid apparatus (1400 K, 10 MPa) working in connection with a high-speed camera. Experimental conditions were chosen to simulate the conditions of p.f. combustion and to provide data for a kinetic description. The temperatures of...
Peat samples were subjected to oven experiments spanning a considerable temperature range, some resulting in ignition and some in failure to ignite. Heat release rates for the two display a temperature dependence describable by a single pair of Arrhenius parameters in spite of significantly greater volatiles release in some experiments than in others. Applicability of the Frank-Kamenetskii treatment...
Previously presented results for the oxidation kinetics and hence the spontaneous combustion propensity of six Scottish bituminous coals are reappraised in terms of ignition times, an aspect not considered previously. All six coals could be considered unsafe to ship according to safety criteria based on the spontaneous combustion propensity, but at least two of them have ignition times so long that...
Ignition behaviour of combustible wastes from the pulp and paper industry was studied in a modified thermogravimetric furnace. Criteria for ignition and the ignition mechanism were developed. The ignition of combustible wastes was predominantly homogeneous. The influence of different factors, such as particle size, sample type, heating rate and oxygen concentration, was studied. In general, no monotonic...
The reactivity and ignition behaviour of solid fuels is a major parameter for combustion and gasification processes, but also for a safe transport and storage of pyrophoric solids. In this work, seven non-isothermal methods were compared with respect to characterise the ignition behaviour as well as to calculate kinetic parameters; for comparison also 'classical' isothermal measurements were done...
Microwave plasma is studied as an alternative to oil or gas fuel for ignition and stabilisation of burning of lean coal. The study is performed on an experimental set-up, which includes a burner with a microwave plasma generator, coal and air supply systems, and measurement equipment. Power and thermochemical characteristics of the coal–plasma interaction have been measured and analysed. The obtained...
A study of the unsteadiness problem of the ignition of static premixed gases that contain CH 4 and steam by a catalytic hot sphere and a non-catalytic hot sphere were conducted, and a comparison between calculated and experimental results was done in the paper. The catalytic reforming reaction of CH 4 with steam on the surface of the sphere produced a small amount of H 2 ,...
Induction-heating ignition burner for the pulverized coal fired boiler is introduced. Some experiments were conducted on an experimental set-up, which includes alternative current power system, induction-heating system, pulverized coal and air supplier system, and measurement system to study the ignition process of coal powder and air mixture stream. Some results are presented. An industrial induction-heating...
An experimental study to determine the temperature and mechanism of coal ignition was carried out by using an entrained flow reactor (EFR) at relatively high coal feed rates (0.5gmin −1 ). Seven coals ranging in rank from subbituminous to semianthracite, were tested and the evolved gases (O 2 , CO, CO 2 , NO) were measured continuously. The ignition temperature was evaluated...
Ignition tests were conducted with delayed and fluid petroleum cokes, a high volatile bituminous coal and their blends in bench- and pilot-scale fluidized bed combustors. In the bench-scale FBC tests, a visual inspection ignition criterion was developed based on the ‘CO–CO 2 ’ profiles obtained as a function of time and bed temperature. In the pilot-scale unit, the rapid increase in SO ...
Prediction of pulverized coal ignition behavior in a 40MW tangentially fired commercial boiler is studied. Pulverized coal combustion simulation is performed considering radiation properties of particles. Coal devolatilization and char combustion are modeled and the first order spherical harmonic approximation is used to model the radiative transfer equation. To confirm the accuracy of the simulation...
In this investigation, coal pellets were combusted using a high temperature oxidizer with varying oxygen concentration, using a small scale batch reactor able to preheat the oxidizer to 1273K. In base of the experimental results, the influence of oxygen concentration on the ignition mechanism, the solid temperature inside the particle at the moment of ignition, the mass lost at the moment of the ignition...
Oxy-fuel combustion is a GHG abatement technology in which coal is burned using a mixture of oxygen and recycled flue gas, to obtain a rich stream of CO 2 ready for sequestration. An entrained flow reactor was used in this work to study the ignition and burnout of coals and blends with biomass under oxy-fuel conditions. Mixtures of CO 2 /O 2 of different concentrations were...
This paper describes the thermochemical properties and ignition characteristics of pyrolants consist of B+KNO 3 , B+PbO 2 and B+Ba(NO 3 ) 2 mixtures, where boron is known as fuel and KNO 3 , PbO 2 and Ba(NO 3 ) 2 act as oxidant. Differential thermal analysis (DTA) and thermogravimetry (TG) techniques have been employed to elucidate the...
Ignition and flame propagation characteristics of 18 kinds of coal and a petroleum coke were investigated through a laser ignition experiment. Flame stability was strongly influenced by amount of volatile matter and pyrolysis rate. Lean limit of flame propagation was strongly influenced by amount of volatile matter. Flame propagation was observed when pyrolized volatile matter was mixed with surrounding...
In this investigation, ignition processes of methane (CH 4 >98%) and propane (C 3 H 8 >95%) using a high-temperature oxidizer (T oxi >T ai ) with a varying oxygen concentration (zO2=0.05÷0.21), applying two types of experimental installations, viz. a constant–volume bomb (CVB) and a co-flow reactor (CFR) were investigated. The influence of the initial...
Diesel engine cold start is an important issue for current technology at low (below 0°C) temperatures and for future applications. The aim of this work is to develop a description of how, when and where does fuel spray ignition occur in a glow-plug assisted engine under simulated low temperature cold start conditions. In-cylinder pressure analysis is combined with high speed visualization in an optical...
The current work presents the results of an experimental study of the intermediates formed during ignition of methyl butanoate (C 5 H 10 O 2 ) and air mixtures. A rapid-sampling system and the University of Michigan rapid compression facility were used to acquire gas samples at conditions of P=10.2atm and T=985K using mixtures of χ mb =0.96%, χO2=20.79%, χN2=52.89%,...
Starting at low temperatures (below 0°C) is an important issue for current and near future diesel engine technology. Low ambient temperature causes long cranking periods or complete misfiring in small diesel engines and, as a consequence, an increased amount of pollutant emissions. This paper is devoted to study the influence of nozzle geometry on ignition and combustion progression under glow-plug...
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