Reseaech On Flow Characteristics Of An Atmospheric Pulverized Coal Gasifier With Strong Rotation

At present,China's existing or under development of coal gasification technology is pressurized coal gasification technology,but it is not suitable for a large number of small and medium-sized chemical enterprises in china.For the large number of small and medium sized chemical enterprises in our country,it is the most reasonable choice to adopt the technology of atmospheric gasifier for upgrading.Therefore,in the current basic situation of our country,it is necessary and urgent to study the advanced atmospheric gasification technology suitable for a large number of small and medium sized chemical enterprises in china.In this paper,a pulverized coal atmospheric gasifier product 40000Nm3/h is taken as a prototype,and the structure and operation parameters of cold test-bed are obtained according to the calculation principle of gas solid two phase cold model.A cold test-bed with prototype1:6 is established.On a cold test-bed,when the ratio of primary air and secondary air is 2:8,a three-dimensional PDA system is used to study the gas solid two phase flow characteristic in a cold test-bed,when changing the angle of the swirling blades.The results show that there is obvious strong rotating flow field in the gasifier,with the increasing of angle of the swirling blades,the rotation ability also increases,but the increase is smaller.A stable central recirculation zone exists in the gasifier,and the recirculation zone is deflected from bottom to top through the entire gasifier.With the increasing of the angle of the swirling blades,the velocity and size of the central recirculation zone will also increase.The gap between the first nozzle section and the middle section of the first and second nozzles is obvious,and the other section increases slightly.The particle volume flux is higher near the wall,smaller and negative in the central recirculation zone and the wall recirculation zone.The particle size near the wall is larger and smaller in the central recirculation zone.Taken together,the selected angle of the swirling blades is the design value 40.In this paper,under the angle of the swirling blades is 40,the numerical simulation of FLUENT software is used to study the characteristics of gas solid two phase flow in a cold test-bed when changjing the ratio of primary air and secondary air.The simulation results are in good agreement with the experimental results.Under different working conditions,the rotating flow field is produced in the gasifier,when the ratio of primary air and secondary air is 2:8,the rotation ability is maximum,the central recirculation zone size and the velocity is acceptable.When the ratio of primary air and secondary air is 6:4 or 4:6,the central recirculation zone is affected by secondary air,and fluctuates widely and have two peak values,The central recirculation zone is small,is not conducive to the uniform distribution of heat load.The residence time distribution results show that when the ratio of primary air and secondary air is 2:8,particle residence time is longer than the other two working conditions.The particle residence time decreases with the increase of particle size and density.On the whole,this paper recommends the angel of the swirling blades is 40,the ratio of primary air and secondary air is 2:8.