A Crystallizer Of Potassium Nitrate Of Numerical Simulation And Structural Optimization

Vacuum-crystallizer has a high evaporation capacity and have low price of the operation cost. And continuous operation is possible in vacuum crystallizer where it has low pressure, therefore, the vacuum crystallizer widely use in chemical, petroleum and different industries of the inorganic salt solution of evaporation concentration, it also can be use in waste liquor treatment, etc. In vaccum-cooling- crystallization process, using the crystallizer, produces the potassium nitrate.According to the research results of DanXiang agricultural Means of Production Co., Ltd. and the documentation, when the potassium nitrate is crystallizing in vacuum-cooling-crystallization, as a result of the role of steam ejector which is a crystallizer of potassium nitrate(CPN) pump vacuum, inner of crystallizer appear obvious phenomenon which is splashing of solution with potassium nitrate. At same time, potassium nitrate particles are sedimentary under action of gravity field. Therefore, inner wall of crystallizer create potassium nitrate scale. Whether the crystallization effect of CPN is good or bad will directly affect continuous operation of potassium nitrate's vacuum-cooling-crystallization. On the basis of the potassium nitrate crystallizing, this paper carrys out the related research.When potassium nitrate crystallizes under vacuum-cooling condition, needing to pump vacuum by steam injector, in order to maintain the pressure of crystallizer, so the vacuum steam injector is one of the key components of whole cooling crystallization process. In manual of design data, the distance that between the outlet of the nozzle and the inlet of the mixing chamber X (see figure 3.2) is a value range, but this value greatly affects the steam ejector and the vacuum pressure of CPN. Thus, using Fluent 6.3 to research the distance of X, select an optimum value of X by analyzing the results the numerical simulation.There exist a phase-changing of liquor flash when potassium nitrate crystallizes in the process of vaccum cooling, so the model of crystallizing become a vapor-liquid-solid three phases model. This paper uses the Fluent, the module of ANSYS 12.1, to simulate calculation. At same time, dealing with the phase-changing of aqueous solution adopt the method of the secondary developing function to simulate calculation by the UDF program. The numeric result indicates that the volume fraction of solid-phase on the inner-wall above the inlet of potassium nitrate solution is higher than the opposite wall. Where is the inner-wall above the inlet, the value of the volume fraction of solid-phase come to 0.7, this simulation results are confirmed with the actual production situation of DanXiang agricultural Means of Production Co., Ltd. To this, the structure of the new CPN is optimized designed based on an original CPN, and also using Fluent module simulate it under the same condition parameters, under the same import and export boundary. Simulation results show that the first outlet avoids getting large pieces of potassium nitrate's particles crystallized, so the first mother liquor can easy to be drained out the CPN. In addition, contact surfaces of the optimized designed of CPN reduce dipping to potassium nitrate solution, therefore, the new CPN can effectively reduce the scaling phenomenon from the origin.