Pellet combustor

The combustion of sulfur-rich char is accompanied by the production of an undesirable reaction product, viz., sulfur dioxide. However, most of the sulfur dioxide should be removed from the combustion gases before they leave the combustor. This may be accomplished by the introduction into the combustor of suitable additives which can absorb sulfur dioxide. Limestone is such an additive. The limestone reacts with sulfur dioxide in the presence of oxygen to form calcium sulfate, which is a solid product and can be easily removed from the reactor. In this work, a model is proposed for the prediction of sulfur dioxide removal from the combustion gases, based on knowledge of gas-solid reactions taking place on a single pellet. 

The feedstock selected as the most applicable for the pilot facility was pelletized MSW. The pellets, obtained from the Teledyne National Company, had been preprocessed to remove metal and most of the moisture before pelletizing. A representative analysis based on an average of several analyses is presented in Tables I and II. The pellets were preferred over shredded MSW due to the relative ease of handling in the 10 cm diameter screw feeder used in the pilot facility. A larger combustor system would not be limited to the use of a pelletized feed. 

Prior to each run, the MSW hopper was loaded with MSW pellets the DSS feed tank was filled and the lime or clay (when needed) was mixed with the DSS the flue gas analyzers, pressure, and weight indicators were calibrated and the combustor and EHE were loaded with their respective dense and entrained bed material. A 650-675 C fluidizing gas stream was generated using a natural gas burner and was used to heat the bed. 

Catalysts in thin-wall honeycomb form offer the advantages of low pressure drop, high geometric surface area, and short diffusion distance as compared to conventional pellets and beads in fixed bed reactors (1). Active zeolite catalysts may be extruded in the form of a honeycomb structure or they may be washcoated on ceramic honeycomb substrates. The latter technique has been widely used in automotive emissions control (2), woodstove combustors (3), control of volatile organic emissions from organic solvents (4), ozone abatement in jet aircraft passenger cabins (5), and N0x abatement... 

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