Study on the Smelting Treatment of City Sludge

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In order to clarify the performance of the sludge-melting furnace with coke packed bed, numerical analysis of gas flow, liquid flow, movement of solid and heat transfer in the furnace were carried out in company with model experiments. For developing a mathematical model of a sludge-melting furnace, a series of experiments were made to obtain the equation of motion for the solid. From the experimental data, it was found that the kinematic model is favorable, supporting the applicability of the present mathematical model for estimating the solid flow in a moving bed. A staggered differencing technique on boundary-fitted curvilinear grids was used to compute flow and heat transfer in a sludge-melting furnace having an arbitrarily shaped domain. Ergun's equation with an inertial term was used for the equation of motion of gas and a kinematic model was used for the equation of solid flow. Fundamental equations of heat transfer in gas and solid were composed of terms for convection, conduction, heat exchange and heat source. Two-dimensional distributions for the velocities and temperatures of gas and solid were obtained numerically by applying the finite difference method. It was found that the temperature distribution was affected principally by gas and solid flow and that a significant temperature change and high solid velocity appeared within the gas inlet zone. Gas temperature is higher than solid temperatures except in the inlet zone.In the final stage of this study, the model experiments and mathematical simulation were performed for the behavior of smelting material. Computed results agreed considerably with the observed one. Therefore, it was expected to estimate the complex phenomena in the sludge-melting furnace by the mathematical model and to obtain the useful results for the design of new developing process.