Chaotic mixing performance and mass transfer enhanced by rigid-flexible impeller with pulse jet

Conventional stirred reactors generally use rigid impeller for mechanical stirring, which leads to the easy creation of isolation mixing regions in the reactor and reduces the efficiency of fluid mixing. The use of multi-flow field coupling to induce chaos and promote more fluids into a chaotic state is one of the effective ways to improve fluid mixing efficiency. In this work, the largest Lyapunov exponent(LLE) and multi-scale entropy(MSE) are investigated with the Matlab compile pressure pulsation signals. The effects of duty ratio, paddle type, flexible paddle thickness, paddle height from the bottom and pulsed air jet flow rate on the chaotic mixing of fluids in a stirred reactor under different pulse periods are explored. In addition, the effects of different impeller types, jet types and air jet flow rate on the volume oxygen mass transfer coefficient K_La are compared and analyzed. When T=0.4 s and D=80%, the results show that the LLE of the rigid-flexible RT impeller compared with the rigid RT impeller increases 11.58% and the MSE of the rigid-flexible RT impeller is also larger than that of rigid RT impeller. It was showed that the pulsed jet rigid-flexible impeller system can better enhance fluid chaos, increase the fluid mixing efficiency and homogenize the system energy distribution. In addition, pulse jet coupling RF-RT impeller system enhances the turbulent characteristics of the fluid, promotes the reduction of the thickness of the liquid film, strengthens the mass transfer and increases the K_La value of the system. When power consumption per unit volume is 360 W/m³, the K_La of the PJ-RF-RT system compared with the PT-R-RT system increases 13.46%, and the K_La of the PJ-R-RT system compared with the SJ-R-RT system increases 11.86%.     

适用于粗颗粒矿物浮选的颗粒悬浮特性的研究

在实验室条件下通过测定新型叶轮定子系统在不同转速条件下浮选槽内的颗粒悬浮参数,确定适用于粗颗粒矿物选别的完全离底悬浮临界转速,同时对新型叶轮定子系统和普通KYF叶轮定子系统在浮选槽内的矿物颗粒悬浮参数进行对比,分析得出新型叶轮定子系统上下两个循环通道的分界面到槽底的距离比普通KYF叶轮大,可以有效提高粗重颗粒的离底悬浮高度,在避免粗颗粒矿物快速沉降的同时可以提高其回收效果。     

中小型叶轮给煤机监控系统设计

开发了一套基于RS485总线通讯的中小型叶轮给煤机监控系统,具有开发费用较低、通讯稳定性和实时性高、现场适应性广等特点。     

Mixing Time Studies in Multiple Impeller Agitated Reactors

Mixing time studies have been carried in a 0.3m diameter and 0.9m tall vessel equipped with three impellers. Conductivity measurement technique has been used for the measurements of mixing time. Effect of the various parameters i.e. tracer density, tracer volume, speed of rotation and impeller combination on mixing time has been studied for two impeller combinations used viz. PTD‐PTD‐PTD and PTD‐PTD‐DT. A compartment model (with one fitted parameter, the exchange flow rate Q_E) with single compartment per agitation stage has been used to predict the conductivity response and the exchange coefficients are calculated from the model parameter. An attempt has been made to explain the experimental results on the basis of the liquid phase axial dispersion coefficient and cell residence time, calculated from the model parameter Q_E     

三叶后掠-HEDT组合桨搅拌釜内流场的模拟及实验

对应用于聚乙烯聚合反应中的三叶后掠-HEDT组合桨的搅拌釜内流场进行了模拟研究,分析组合桨的离底距C ₁、桨间距C ₂以及转速N的变化对搅拌釜内流场的影响,利用PIV实验对模拟结果进行了验证;将该组合桨与三叶后掠-六直叶圆盘涡轮组合桨进行了模拟对比研究。结果表明：当桨间距与釜内径的比为0.35时,釜内桨叶间的流体流动效果最好,该条件下能够改善搅拌釜上层流体的速度分布;当离底距与釜内径的比值为0.29时,组合桨下方出现了整体的环流,有利于釜底流体的混合;桨叶转速N=90 r/min时釜内流体速度分布均匀,同时上层HEDT桨叶产生的射流方向趋于水平。两种组合桨的对比研究表明：二者流型相近,但前者搅拌功率能够得到明显降低。研究结果可为三叶后掠-HEDT组合桨在聚乙烯聚合反应釜中的工程应用提供参考。     

湿法磷酸固-液体系混沌混合与浸出强化行为

湿法磷酸浸出过程中，传统刚性搅拌桨的作用方式主要是剪切作用，容易形成对称性流场结构，降低搅拌效率。实验考察了桨叶类型、离底高度、搅拌速度、柔性钢丝绳长度、柔性钢丝直径对磷矿浸出率及最大Lyapunov指数(LLE)的影响。实验结果表明：刚柔组合桨通过刚-柔-流的耦合作用，改善流场的结构，提高了流体混沌混合效果。当搅拌转速225 r/min，浸出时间120 min，离底高度h=T/4，柔性钢丝绳直径d= 0.42r，柔性钢丝绳长度L=1.3T时，刚柔组合桨的最大Lyapunov指数达到0.09071，磷矿浸出率提高了10.8%。另外，在相同的功耗(P _v=9890 W/m³)条件下，刚柔组合桨使反应器内的悬浮均匀度和渣中磷含量分别降低了40.8%和17.67%，有效地改善了晶体的形貌，提高了磷石膏的过滤性能，强化了颗粒的混合与浸出。     

翼型桨叶片尾涡结构的PIV实测与LES模拟研究

在塔径383 mm、高径比为1的翼型桨搅拌反应器内,采用粒子图像测速(PIV)技术和大涡模拟(LES)研究了一种翼型桨的叶片尾涡结构. 对比二维PIV技术测定的翼型桨搅拌反应器平均速度场数据,验证了LES方法的可靠性. 并通过叶片端的速度矢量场、叶片区内的涡量大小及湍动能分布清楚地识别了翼型桨叶片尾涡结构. 发现该叶片尾涡为单涡结构,其尾涡轴心轨迹几乎就在桨叶尖划过的圆柱面上. 此外,还探讨了叶片尾涡对湍动能分布、湍流特性等的影响,表明最大无因次湍动能k/Vtip2约为0.04~0.06,其位置约在0.5相似文献   

液氯液下泵故障分析及改进

分析了LSY40 -10/7型液氯液下泵气相部分、支撑管、出液接管、推力盘等部件烧毁,泵轴承断裂的原因,并提出了改进措施.