回流缝宽度对三相分离器分离效果影响的模拟

Effect of Sludge Return Crack Width on Separation Efficiency of Three-phase Separator in UASB Reactor

为探索厌氧反应器中三相分离器污泥回流缝对分离器内流场及气、液、固三相分离性能的影响,以Eulerian多相流模型为理论框架,利用计算流体动力学(CFD)技术对厌氧反应器及三相分离器中的气、液、固三相三维流场以及分离效率进行了模拟分析,模拟中采用工程上常用的80、95、110、125、140 mm回流缝宽度。模拟结果表明:三相分离器内部的三相流速大大高于反应器的设计上升流速,其中固相平均流速相对较高;三相分离器内部液相流场以环流为主;污泥回流缝宽度对气、液流动相影响小,对固相影响则相对较大;三相分离器对固相的分离效率较高,混合液经过一层挡板的固相分离率均大于87%,而气相的分离率最低在60%;污泥回流缝宽度越宽、各单层的气、固相分离效率下降,通过三相分离器最上层沉淀区域的补充,混合液中的固相基本上能达到完全分离,而气相在回流缝宽度为95 mm左右时分离效率最高。

The crack width of sludge return crack for the three-phase separator （TS） plays a key role in the separation process. To evaluate the effects of crack width on the separation efficiency of solid, liquid, gas in TS of USAB reactor, a 3-D CFD simulation was adopted based on Eulerian multi-phase model. Five typical crack width settings as 80 mm, 95 mm, 110 mm, 125 mm, 140 mm were investigated for a typical UASB reactor. The result shows that the average flow speed of three phases in the TS region was much higher than the UASB＇ s designed up-flow speed, and the flow speed of solid phase exceeded that of gas and liquid. Circulation pattern turbulence dominated the liquid flow in TS region. The crack width had more obvious effect on solid phase than on gas and liquid. The separation efficiency was much effective for solid phase in five cases through one platewhile only 60% for gas. The separation efficiency of gas and solid phases became lower with a wider crack gap. With the supplement of precipitation layer in the top of TS, the solid phase could separate completely, while the highest separation efficiency for gas was obtained with gap width of 95mm.