CFD studies of scraper built in SPA clarifying tank based on mixture
CHEN Yu1, ZHOU Jianxu 1*, ZHANG Zhengyang2
1.College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2.China Water Resources Beifang Investigation, Design and Research Co. Ltd., Tianjin 300222, China
摘要 In the industrial process of producing the strong phosphoric acid (SPA), clarification of the solution is essential to the ultimate product. However, the large viscosity of sediment and the induced interface interaction result in difficulties when the SPA is clarified. CFD numerical methodology is applied to simulate internal flow field and performance of the low speed scraper based on Mixture solidliquid twophase flow model. Sediment deposition is generated by loading solid particles at the bottom of clarifying vessel. The moving mesh and RNG k-ε model are used to simulate the rotational turbulent flow in clarifying tank. Variables studied, amongst others, are the scraper rotation speed and the mounting height, which can affect the solid suspension height. Features of flow field and solid volume fraction distribution in computational domain are presented and analyzed. The numerical reports of the scraper torque and velocities of inlet and outlet filed are obtained. It seems the torque value of rotational axis and particle suspending height augment with an increasing rotating speed. Meanwhile, a high revolving speed is good for the deposition discharge. The particle fraction distribution in meridional surface and horizontal surface at fixed rotation speed are analyzed to determine the corresponding optimal installation height. The simulating results reflect the flow field is marginally stirred by the scraper and proper working parameters are obtained, in which case the comprehensive properties of the scraper and the clarifying tank are superior.
［1］CANG Q. Analysis on scaling in PA production and its countermeasures［J］. Phosphate ＆ compound fertilizer, 2002, 17(6):27-28.［2］DUAN F G. Practice and study of phosphoric acid settlement used in AP plant［J］. SP ＆ BMH related engineering,2008,4: 8-14.［3］YANG J. Clarify pool research and development［J］. Jiangxi chemical industry,2010,3:21-23.［4］WANG S Y, JIANG X X, WANG R C, et al. Numerical simulation of flow behavior of particles in a liquidsolid stirred vessel wiith baffles［J］. Advanced powder technology, 2017, 28(6):1611-1624 ［5］ALESSANDRO T, ANDREA C, GIORGIO M, et al. Particle suspension in vortexing unbaffled stirred tanks［J］. Industrial ＆ engineering chemistry research, 2016, 55(27):7535-7547.［6］DIVYAMAAN W, MOSES O T, VISHNU K P, et al. CFD simulation of solidliquid stirred tanks for low to dense solid loading systems［J］. Particuology, 2016, 29:16-33.［7］ZHAO H L, ZHANG Z M, ZHANG T A, et al. Experimental and CFD studies of solidliquid slurry tank stirred with an improved Intermig impeller［J］. Transactions of Nonferrous Metals Society of China, 2014, 24(8):2650-2659.［8］MOHAMED A E, MOHAMED H A, AHMED A Z, et al. Liquidsolid mass transfer behavior of a stirredtank reactor with a fixed bed at its bottom［J］. Chemical engineering technology,2014, 37(9):1525-1531.［9］WEI H Z, TAO B L, SHU A Q, et al. Numerical simulation of two phase flow in phosphate aging tank［J］. Journal of Wuhan Institute of Technology,2012,34(12):54-57.［10］HUANG X B, YAN X B, SHI L T, et al. Liquid velocity distributions in solidliquid stirred vessels ［J］. Journal of chemical industry and engineering,2002, 53(7):717-722.［11］LIANG Z, WANG J Q, REN L C, et al. Theoretical study of solidliquid separation hydrocyclone flow field［M］. Beijing: Petroleum Industry Press,2011.［12］XIE Y F. Numerical simulation of lowsedimentcondition flow using mixture model of multiphase flow［D］. Xi′an: Xi′an University of Technology,2005.［13］WANG W G, CHEN L, ZHANG L X, et al. Determination of densities and viscosities of phosphoric acid at low temperatures and its correlation ［J］. Journal of Wuhan Institute of Technology,2011, 33(9):1-3.［14］ZHOU D Q, MI Z H, MAO Y T. 3D numerical simulation of inlet structure flow in pumping station based on Eulerian solidliquid twophase flow model［J］. Transactions of the CSAM,2013, 44(1):48-52.［15］VAN J P, RAITHBY G G. Enhancement of the SIMPLE method for predicting incompressible fluid flow ［J］.Numerical heat transfer,1984, 7:147-163.
