Estimation of burning rates in solid waste combustion furnaces

For a furnace burning solid wastes, one of the key areas in design is the s izing of the furnace which is often determined on the basis of empirically selected furnace heat release rate and grate burning rate. An independent e stimation of these factors would require the knowledge of physical processe s of refuse combustion such as drying and heating of the refuse bed, chemic al reactions of waste combustion, supply and distribution of combustion air , and mixing of combustion air with the burning refuse bed. In principle, the gross combustion rate of solid refuse bed is related to t he oxygen consumption rate of the burning refuse bed. In this paper an atte mpt is made to estimate the refuse burning rates in the furnaces by calcula ting the oxygen distribution in the combustion chamber. A model based on th e fundamental principles of conservation of mass, energy and momentum balan ce is established for this purpose. For different combustion chemistry mode ls, by using a reaction rate coefficient which could be affected by paramet ers like bed height, porosity of the fuel bed, and underfire air rates, the oxygen distribution in the fuel bed, and hence, the combustion rate can be determined. Comparisons of the theory with the laboratory test data and re al plant operating data indicate that the theory can be tuned to fit the da ta reasonably well by adjusting the reaction rate coefficient.