Design And Performance Study Of Backflow Type Dynamic Cyclone Separator

Coalbed methane is a kind of unconventional gas resources that has a symbiosis with coal. Our country is rich in coalbed methane reserves. With the rapid growth of demand for natural gas in China, the development of coalbed methane resources can be an effective supplement to the natural gas production, to improve our country’s energy structure.Coalbed methane contains sand grains inevitably during the exploitation process, the existence of these particles improves the transportation cost, and it is difficult to meet the production condition of downstream users, so the CBM surface gathering process puts forward strict requirements on dust removal efficiency, on one hand coalbed methane has the characteristics of that containing small size particles, being mined at low pressure, fluctuating significantly in flow, on the other hand, the existing separation technology is difficult to meet the need well, therefore there is a need to develop a separation equipment with high efficiency which is suitable to coalbed methane.This paper mainly analyzes the characteristics of traditional gas-solid separation device and summarizes the measures to improve the performance of the separator. By referring to the previous studies and considering the working condition of coalbed methane, this paper designs a new type of more efficient gas-solid separation equipment named as backflow type dynamic cyclone separator and introduces structure principle and performance indicators of the device as well.Using Fluent software, the flow field inside the separator is simulated adopting Reynolds stress model (RSM) and the particle trajectory and the separation efficiency are also simulated with discrete phase model (DPM).This paper stimulates and analyses the influence law of structural parameters and operating parameters on flow field and separation efficiency, in order to provide the basis for design optimization.After machining an experimental prototype, the author builds up a complete set of experimental platform and measures the separation efficiency. The influence law of structural parameters and operating parameters on pressure performance and separation performance is studied through experimental way, and the performance of the optimized whole machine is obtained.The numerical simulation and experimental study show that:the flow field of backflow type dynamic cyclone is symmetric, the new structure effectively eliminates the secondary vortex flow which exists in traditional cyclone separator, resulting in being conducive to separation. The fractionation efficiency of particles that are larger than5μm is more than95%, and as to the particles whose mean size is10μm in dusty gas, the separation efficiency is up to99.5%. Return pipe has the effects of stabilizing flow field, improving efficiency and reducing the pressure loss, by setting the return pipe, the separation efficiency of fine dust increases by10%and the pressure loss decreases by more than100Pa. When exhaust pipe diameter decreases, separation efficiency increases and the pressure loss increased significantly as well. When impeller diameter increases, the separation efficiency increases first and then decreases, but the pressure loss continuously increases. Handling capacity fluctuations have greater impact on the pressure loss, but less impact on the separation efficiency, if the capacity changes by rate of50%, the separation efficiency only changes by rate of less than2%and all are around98%, that result shows the separator has a good ability to resist flow fluctuation. The impeller speed should not be too large, otherwise the pressure loss and energy consumption increases, but the separation efficiency decreases.Summed up simulation and experimental results, we obtain the optimal equipment structure and operation conditions.