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The co-combustion of pulverised coal and biomass is increasingly being used for environmental reasons, and a number of computational fluid dynamic investigations are being undertaken to understand the details of the combustion process. These investigations assume that the particle flow entering the burner is uniformly distributed across the burner mouth or inlet. In this paper, this assumption is examined for an industrial burner by numerically simulating the fuel particle flows in the tube leading to the burner mouth. While there is evidence of maldistribution of the particles at the burner mouth, it is concluded from the flame data that this effect does not significantly influence the combustion flame in the furnace for the cases investigated.

The co-firing of pulverised coal/biomass in power generation plants is receiving considerable attention due to its influence in reducing all forms of emissions. Unlike coal, milled biomass, such as straw, may contain large particles of different sizes and shapes, which can have an impact on the combustion characteristics and emissions. Computational fluid dynamics (CFD) is often used to understand the influence of large biomass particles in a furnace. However, most CFD sub-models simplify heat transfer effects within the particles during combustion. In this paper a particle heat-up model, which considers the influence of thermal gradients within large biomass particles, is applied to a co-firing coal/biomass simulation in a tangentially fired furnace with up to 12% thermal biomass loading. Different sizes of biomass particles of non-spherical shape and their impact on the combustion behavior have been investigated. The influence of the particle size and shape distribution on the combustion characteristics and emissions was found to be significant. The computed results were found to be in good agreement with the experimental data.

Recent national and international emission legislations to reduce emissions of carbon dioxide are forcing power generation industries using coal to look at various alternatives, such as biomass and especially by co-firing techniques. Biomass is transported to the burners either mixed with the primary fuel, in general, coal, or used in dedicated pipelines. In both cases, transportation of biomass is difficult due to its composition, size, shape and physical behaviour in comparison to the transportation of coal. This study considers experimental measurements for biomass particle transportation in a pipeline with a transverse elbow and compares the results with those using computation fluid dynamic (CFD) techniques. Various materials: flour, willow, wood, bark and a mixture of flour and willow, have been considered in the present investigation. The experimental work was performed using the dynamic changes in the electrostatic charges of biomass particles in conjunction with correlation signal processing techniques. The CFD simulations were performed by considering the effects of gravity, non-spherical drag (based on estimated shape factor), detailed information of the particle distribution, particle wall collisions and particle–particle interactions. Good quantitative and qualitative agreement was obtained between the CFD simulations and the experimental data. It is concluded that particle–particle interactions are of less importance if the mass loading ratio of particles to air is less than 0.03.

The authors describe their contribution to the ETSI (European Telecommunications Standards Institute) effort for a definition of a GSM (Group Special Mobile) standard half-rate coding system for the pan-European digital mobile cellular radio system. The system consists of a speech coder and a channel coder. An overview of the speech coding algorithm is given. The results from a study of the different versions of the speech coder are described. A two-stage channel coding scheme is presented, and the performance test results are shown. An overview of the DSP implementation, computational requirements, and memory usage is also presented. >