| The water treatment plant plays an important role in the development of social urbani-zation.As core equipments of a water purification treatment process,a coagulation agitation tank and a flat flow sedimentation tank can effectively reduce the treatment load of their follow-up equipments,so their flow field characteristics and solid particle distribution states limit the operating efficiency of the water treatment plant.Three-dimensional models of different operating conditions are simulated and flow field structures are optimized by a computational fluid dynamics?CFD?as for Shijiazhuang Xuanwu Water Purification Plant,and the main research results are as follows:?1?Changes of rotational speeds obviously affect distribution characteristics of fluid flows:The average speed in the coagulation agitation tank is increased by 20.6%and the influence range of the circulation flow area is increased by 33.1%as the rotational speed increases from 18 rad/min to 138 rad/min;Coagulation agitation tank occur slarge local concentrations,and the largest one of which reaches to be 6.987×10-8 kg/m3.Coagulant concentration distribution is more uniform than others when rotor speed is 48 rad/min.?2?As the inflow rate increases from 1000 m3/h to 4000 m3/h,the average speed of the coagulation agitation tank increases by 268.76%and the influence range of the circulation flow area is increased by 17.5%;Average stop time of coagulants decreases by 31.09%;The mixing efficiency reaches to be the best when the influent flow rate is 2500 m3/h.?3?Sedimentation effects of suspended solids steadily decreases along the water flow way;there are several eddies in the inflow hole area of a grid screen wall,and their influence areas are 40.6%of the inflow area;the eddies increase turbulence characteristics of the water flows,so the condition is not good at the settlements of suspended solids;the flow is stable in the outflow area,and the sedimentation effects of suspended solids are significant.?4?Reducing flow speed of the flat flow sedimentation tank accelerates the settlements of micro size suspended solids:As the inflow rate decreases from 4000 m3/h to 1000 m3/h,the average speed in the flat flow sedimentation tank decreases by 267.6%and the settlement efficiency of the suspended solids increases by 1.468%. |
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