热集成变压精馏分离吡啶-水的控制研究

Control of heat-integrated pressure swing distillation system for pyridine-water separation

对于吡啶-水的分离,与传统的变压精馏工艺相比,热集成变压精馏工艺更加节能经济,进料流量为3 000 kg/h时,可以节约能耗43.52%,节省年度总费用40.70%。为了将该工艺应用在实际生产中,必须解决其控制的问题。在最优设计基础上,提出2种基于PI控制器的控制结构,并采用动态模拟软件Aspen Dynamics检验了存在进料流量和进料组成干扰情况下控制结构的有效性。模拟结果表明:扰动存在时,由于基本控制结构CS1中二塔均存在压力效应,并且控温板温度稳定在设定值,导致水和吡啶产品质量存在较大稳态余差。进而,在CS1基础上引入温差控制策略和压力补偿温度控制策略,提出一种改进的控制结构CS2。模拟结果显示,针对相同的进料流量和进料组成扰动,控制结构CS2的动态控制性能显著提高,产品质量的稳态余差均较小。

The heat-integrated pressure swing distillation scheme is more energy-saving and economical compared with the corresponding traditional pressure swing distillation scheme for pyridine-water separation,with 43. 52%saving in energy consumption and 40. 70% reduction in total annual cost for the feed flow rate of 3 000 kg / h.Whether this more economical design can be applied in practice strongly depends on whether it can be effectively controlled. On the basis of the previous proposed optimal design,two control schemes using PI controllers were explored. Dynamic simulations were realized using commercial software Aspen Dynamics. To test the effectiveness of the two control schemes,step changes in feed flow rate and feed composition disturbances were made. The dynamic simulation results reveal that the proposed basic control scheme CS1 with fixed controlled plate temperatures cannot maintain the quality specifications for disturbances as a result of pressure fluctuation. Then,differential temperature control was introduced in the low-pressure column,and pressure-compensated temperature control was introduced in the high-pressure column on the basis of CS1. An improved control scheme CS2 was proposed. The corresponding dynamic responses show that control scheme CS2 works pretty effectively for the same feed flow rate and feed composition disturbances. The dynamic control performances are evidently improved. It does a good job in maintaining the quality of the two products.