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新型多级逆流式超重力旋转床精馏性能研究
Studies of Distillation in a Novel Multi-Stage Counter-Current Rotating Packed Bed
【作者】 高鑫；
【导师】 陈建峰；
【作者基本信息】 北京化工大学 ， 化学工程与技术， 2010， 硕士
【摘要】 在化工生产中,通常利用塔器精馏设备对液-液混合物进行分离。但是在传统塔器设备中,液相靠重力自上而下流动,液膜较厚且流动缓慢,存在传质系数低、设备庞大、操作弹性小等缺点。在原料浓度波动大、流量不稳定、有一定间歇性的溶剂回收等领域,传统的塔器精馏设备难以满足操作要求。超重力旋转床作为一种过程强化设备,可有效弥补塔器精馏设备在上述领域的不足,有望发挥更加重要的作用。本文在总结传统旋转填料床(RPB)和折流式旋转床(RZB)特点的基础上开发出一种新型连续精馏设备——多级逆流式超重力旋转床(MSCC-RPB),采用转子外径365mm、内径145mm、具有双层转子的MSCC-RPB,在常压下以甲醇-水体系为主要研究对象、乙醇-水体系为辅助研究对像,进行连续精馏实验,以理论塔板数(NT)来表征旋转床分离效率,考察了旋转床填料、转速(N)、进料浓度(xF)、进料热状况(q)、回流比(R)、分离体系对NT的影响规律。研究结果表明,不同操作条件下,填装填料后旋转床的分离效率提高了30-75%,且随转子转速的增加提高幅度减小。MSCC-RPB的NT随N的增加先增大后减小,并在700-800 r·min-1时达到最佳值。NT随xF的增加变化不大,随q及R的增加而增大。MSCC-RPB对乙醇-水体系的分离效率明显高于甲醇-水体系。在实验考察范围内,对乙醇-水体系,MSCC-RPB理论塔板高度在19.5-31.4mm之间,与传统两台RPB连续精馏的理论塔板高度相当,与RZB相比传质效率提高近一倍且最佳转速更低。
【Abstract】 In chemical industry, distillation was often emplyed to separate or purify liquid mixtures in a column. In a traditional distillation column, the liquid flows under the drive of the gravitational force which led to thicker liquid film and lower liquid velocity. Therefore, some disadvantages such as low mass transfer coefficients, small operational flexibility and big volume are existed in traditional distillation column. In some fields, the solvents and crude product are fluctuations in concentration and flowrate, and most of them are batch or semi-continuous effluent. Therefore, the specifications by traditional distillation process are not satisfactory in these fields. As a process intensification device, rotating packed bed(RPB) has small size, high separation efficiency, easily-operated and wide flexiblity, which was supposed to meet the demands in above-mentioned fields.In view of the characteristic of conventional RPB and rotating zigzag bed(RZB), a novel multi-stage counter-current rotating packed bed(MSCC-RPB) was developed. Its structure and principle was described in detail. Continuous’distillation experiments with methanol-water and alcohol-water binary system were carried out in a MSCC-RPB with outside diameter of 365mm, and inside diameter of 145mm at atmospheric pressure. The separation performance of MSCC-RPB was characterized by the number of theoretical trays(NT). Effects of packing, varying rotation speed(N), feedstock concentration(xF), thermal condition of feed(q), reflux ratio(R) and separating binary system on NT of MSCC-RPB were investigated. Experimental results indicated that the separation efficiency with packing in MSCC-RPB increased 30-75% compared with no packing in MSCC-RPB, and the improvement decreased with increasing of N. The optimum value of N for NT was found to be 700-800r·min-1.NT increased with increasing of N at N<700r·min-1, and decreased with increasing of N for N>800r·min-1. The value of NT remained nearly constant with the increase of xF, and increased with increasing values of q and R. The separation efficiency was much higher for alcohol-water binary system than that of methanol-water. For alcohol-water binary system, the height equivalent of a theoretical tray ranged from 19.5 to 31.4mm, which is almost the same as in a conventional RPB. Compare with RZB, the separation efficiency is nearly doubled, and the optimum rotating speed is much lower than that of RZB(its optimun rotating speed is about 1000r·min-1).