Numerical Study On Combustion System Of Circulating Fluidized Bed Boiler

Circulating Fluidized Bed(CFB) technology has been developed internationally as a new type of clean coal combustion technology .Because of its high efficiency,low pollution and wide sorts of coals,CFB technology deserved scholars great attention from many countries and it has been a primary guide to coal combustion technology.In this thesis a summary is made to describe characteristics of CFB combustion technology,It introduces the present research status and achievements of CFB combustion models. Based on previous research works, The characters of the gas and solid flowing, the fugitive constituent releasing and combusting, the coke combusting, the forming and reducing of the pollution, and the heat transfer are all adequately considered in this model. And the distribution character of the thermal parameter is also considered by the compartment model in the direction of axial, and the annular core structure in the direction of radial. Based on the mass conservation law, the energy conservation law and some empirical equations, the combustion model is built. distribution. Because of the complicated physical and chemical process in the furnace, some proper simplifications are introduced in the model.The model divides the furnace into two parts: a dense one at bottom part that is a bubbling bed and a dilute one at up part which is a annular core flow structure. Namely the model is based on a two phase structure,consisting of an upflowing lean suspension and a downflowing particle clusters. On the hydrodynamics model, a particle cluster renew mechanism is adopted to describe the heat transfer. The coal combustion model includes four submodels: devolatilization and volatilization combustion, coke combustion, fuel gas homogeneous combustion reaction, pollutant emission formation and reduction. In the pollutant submodule, has established the desulphurization model and simplified the nitrogen oxide compound production and thedecomposition model.Through established model in this article, Has carried on the numerical simulation computation and calculation analysis about the 75T/H CFB boiler combustion situation. are obtained in this paper. Has obtained the primary running parameters(circulating solids flux,temperature,desulfurater and so on) to the CFB boiler combustion performance influence rule. The flow and heat transfer is further understood and comprehended and this thesis provide a theoretic basis for further development and application of CFB boiler. In comparison with the experiment results of documentation data, numerical simulation results match well with the experiment results. It proves that the overall model is a useful tool to research and design the circulating fluidized bed boiler.