【摘要】：柱塞流電化學反應(yīng)器(PFER)是一種可以提高電流效率,降低處理成本的新型電化學法處理技術(shù)。網(wǎng)板柱塞流電化學反應(yīng)器(MPE-PFER)因陰陽電極面積相同且垂直于流體流動方向,電極為棱形網(wǎng)孔結(jié)構(gòu),可解決傳統(tǒng)柱塞流電化學反應(yīng)器電流分布不均、流體速度分布不均、湍流強度不均等不足,有利于污染物的傳質(zhì)和分解。計算流體力學(CFD)可有效模擬反應(yīng)器內(nèi)部流場、粒子圖像測速技術(shù)(PIV)可直觀觀測反應(yīng)器內(nèi)部流場,結(jié)合這兩種技術(shù)可為反應(yīng)器的性能研究和結(jié)構(gòu)優(yōu)化提供可靠的依據(jù)。本文采用CFD與PIV相結(jié)合的方式,分別模擬和測試了不同進口方式(軸向、徑向和切向)對反應(yīng)器的影響,分析了反應(yīng)器進口區(qū)域的速度場和整個反應(yīng)器的壓強降等水力特性。結(jié)果顯示,模擬結(jié)果與測試結(jié)果基本一致,進口區(qū)域?qū)倭黧w流動的過渡區(qū)域,受進口方式的影響較大。相比其他兩種進口方式,切向進口的速度分布均勻,沒有大的速度梯度,沒有回流死區(qū),電極表面流速也比較適合,且壓降最小。其次,通過DPM模型,分析了不同氣泡直徑和質(zhì)量流量對反應(yīng)器內(nèi)部流場的影響。模擬結(jié)果表明,氣泡對連續(xù)相流場的影響隨著氣泡直徑的增大而增大,氣泡直徑較小時,氣泡增強湍動且使流場分布變得均勻,而直徑較大時,反應(yīng)器上下部分湍動強度分布不均勻,上端湍動劇烈,而下端出現(xiàn)低湍動區(qū);當氣泡量少時,連續(xù)相流動起主導作用,氣泡對湍動強度的影響不明顯,隨著氣泡的增多,氣泡效應(yīng)越來越明顯,流場分布變得越來越均勻。最后,分別從流場分布和傳質(zhì)性能兩方面對比分析了MPE-PFER和PFER的性能。從流場來看,MPE-PFER中流場受進口區(qū)域影響小,流場可以更早達到穩(wěn)定,穩(wěn)定后徑向流速分布更加均勻,在網(wǎng)孔處達到速度峰值;PFER中電極間流場呈拋物線型分布,流場受進口區(qū)域影響較大。通過對兩種反應(yīng)器傳質(zhì)半經(jīng)驗公式的分析發(fā)現(xiàn),由于網(wǎng)板電極的存在,MPE-PFER的傳質(zhì)性能明顯高于PFER,MPE-PFER的傳質(zhì)關(guān)聯(lián)式是PFER的23.061.4?u倍,在相同的流量變化下,MPE-PFER傳質(zhì)系數(shù)提高的是PFER的兩倍。
[Abstract]:Plunger flow electrochemical reactor (PFER) is a new electrochemical treatment technology which can improve current efficiency and reduce treatment cost. Because of the same area of cathode and positive electrode and perpendicular to the direction of fluid flow, the electrode of MPE-PFER is a prism mesh structure, which can solve the problem of uneven current distribution and uneven fluid velocity distribution in traditional plunger flow electrochemical reactor (MPE-PFER). The uneven turbulence intensity is favorable to the mass transfer and decomposition of pollutants. Computational fluid dynamics (CFD) can effectively simulate the flow field in the reactor. Particle image velocimetry (PIV) can directly observe the flow field in the reactor. The combination of these two techniques can provide reliable basis for the performance research and structural optimization of the reactor. In this paper, the effects of different inlet modes (axial, radial and tangential) on the reactor were simulated and tested by using CFD and PIV, respectively. The velocity field in the inlet region of the reactor and the hydraulic characteristics of the whole reactor such as pressure drop were analyzed. The results show that the simulation results are in good agreement with the test results, and the inlet region is a transition region of fluid flow, which is greatly affected by the inlet mode. Compared with the other two methods, the velocity distribution of tangential inlet is uniform, there is no large velocity gradient, there is no reflux dead zone, the electrode surface velocity is more suitable, and the pressure drop is minimum. Secondly, the influence of different bubble diameter and mass flow rate on the flow field in the reactor was analyzed by DPM model. The simulation results show that the effect of bubbles on the continuous phase flow field increases with the increase of bubble diameter. When the bubble diameter is small, the bubble increases turbulence and makes the flow field distribution more uniform. The turbulent intensity distribution of the upper and lower parts of the reactor is uneven, the upper end of the reactor is intense, and the lower end of the reactor has a low turbulent zone, when the amount of bubbles is small, the continuous phase flow plays a leading role, and the effect of bubbles on the turbulent intensity is not obvious, with the increase of bubbles, The bubble effect becomes more and more obvious, and the flow field distribution becomes more and more uniform. Finally, the performance of MPE-PFER and PFER are compared and analyzed in terms of flow field distribution and mass transfer performance. From the point of view of the flow field, the flow field in MPE-PFER is less affected by the inlet region, the flow field can be stabilized earlier, the radial velocity distribution is more uniform after stabilization, and the flow field between the electrodes in the PFER reaches the peak velocity at the mesh. The flow field is greatly affected by the inlet area. Through the analysis of the semi-empirical formula of mass transfer in two reactors, it is found that the mass transfer performance of MPE-PFER is obviously higher than that of PFER by 23.061.4u, and the mass transfer coefficient of MPE-PFER is twice that of PFER under the same flow rate.
【學位授予單位】：浙江工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X703

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本文編號：2226160