The effects of the physical properties of slurried and pulverised fuels (specifically particle size, density, and phase composition) on combustion are described in this paper, For solid fuels there is considerable flexibility for controlling the particle size, which in turn has a significant impact on ignition, char burnout, and emissions. In contrast, the chemical properties and reaction temperature range of a given fuel are narrowly constrained in most applications. In this work we use a laminar flow reactor to study the initial stages of combustion of coal/water slurries and pulverized coal. In conjunction with the flow reactor, a laser-based in situ particle counter has been used to determine the size distributions of pulverized coal and various slurry mixtures prior to and during combustion. Initial size distributions and subsequent evolution of these distributions vary markedly depending on the fuel preparation, emphasizing the importance of the physical properties of the fuel in determining subsequent combustion performance. Two numerical models are used in conjunction with the experimental results to provide a preliminary analysis of the effects of water content on evaporation and devolatilization, and also of the effects of particle swelling on char burnout times.
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