Resistance Investigation Of The Oxidation Bed Based On Homogeneous Porous Media Mode

Ventilation air methane is directly discharged into the atmosphere at present because of low concentration, huge volume flow and other characteristics which not only wastes resources but also causes environment pollution by greenhouse effect and destruction of the ozone layer. The thermal flow-reversal reactor can effectively oxidize methane and recover energy, and regenerative oxidation bed filled with lots of ceramic regenerators is one of the major energy consumption. In this paper, flow and heat transfer simulation of the regenerative oxidation bed based on CFD aims to select honeycomb ceramic regenerators and optimize the regenerative oxidation bed. The main contents of this dissertation are:1. In order to choose an appropriate ceramic regenerator filled in regenerative oxidation bed of the thermal reverse flow reactor, firstly the geometric structure of types of square, tube-shaped, and hexagonal ceramic regenerators were analyzed and investigated theoretically, the effects of ceramic regenerator's porosity and ratio surface area were obtained under the characteristic length of the ceramic regenerator. And then these types of ceramic regenerators were simulated by using Fluent software, the results were that in the same hole density and porosity, the square ceramic regenerator have a better regenerative ability while the types of tube-shaped, hexagonal honeycomb ceramic regenerator can reduce the pressure loss, the resistance in a square ceramic regenerator is lower and heat transfer efficiency in a hexagonal ceramic regenerator is better under the conditions of the same porosity, specific surface area and equivalent diameter.2. The control equations and chemical reaction equation about coal mine methane thermal oxidation were proposed for a self-developed thermal reverse-flow reactor. The effects of flow resistance and outlet temperature were studied under operating parameters of the oxidation bed, structural parameters and physical parameters of honeycomb ceramic by using homogeneous porous media model. The results show that the oxidation bed resistance instantaneously increases while switching the direction of airflow, gradually stabilized after 1～2s. With the increase of coal mine methane superficie velocity, pressure loss and outlet temperature of the oxidation bed increase. The methane concentration has less effect on pressure loss. With the increase of porosity of ceramic honeycomb, pressure loss decrease obviously, but regenerative capacity decreased obviously. With the increase of specific heat, operation stability of thermal reverse-flow reactor increase. With the increase of equivalent diameter, pressure loss decrease significantly.3. The square and hexagonal honeycomb ceramic regenerative oxidation beds were studied using porous medium model by fluent software firstly. The pressure loss in the square honeycomb ceramic oxidation bed is larger than that in hexagonal honeycomb ceramic oxidation bed, but the outlet temperature is lower. Then a combined oxidation bed which consisted of square and hexagonal honeycomb ceramic is proposed based on the calculating results of the temperature, velocity and resistance loss distribution in axial direction of the oxidation bed, in which the hexagonal honeycomb ceramic is filled in the central of the combined bed, and the square honeycomb ceramic is filled in the two sides. The resistance loss and outlet temperature for seven kinds of combined beds are calculated. The results indicate that the suitable length of hexagonal ceramics in the combined oxidation bed is 1.05m more or less.