通过调整进出料热状况消除隔离壁精馏塔的黑洞

Eliminating black-hole problem of DWDC by adjusting thermal conditions of feed and intermediate product

隔离壁精馏塔在同时控制4个质量指标(塔顶、侧线、塔底产品浓度以及侧线采出杂质比)时会产生设计与操作黑洞,黑洞的产生对隔离壁精馏塔的应用范围带来很大的限制。本文提出了一种通过调整进料和侧线采出的热状况对隔离壁精馏塔的黑洞进行填补的策略。这两个操作变量通过对全塔热平衡的影响,改善预分离塔与主塔之间的耦合关系,进而改善两者分离能力并最终消除黑洞,同时改善了隔离壁精馏塔的动态特性。针对进出料热状况的调整,本文结合牛顿法给出了简单的调整规则,调整会形成3种不同的方案,为不同能量供应条件下填补隔离壁精馏塔的黑洞提供了可能。通过使用Aspen Plus模拟理想三元物系分离,对黑洞填补方法进行稳态分析和动态响应验证,证明采用调整进出料热状况的方法可以有效的填补隔离壁精馏塔的设计与操作黑洞并使其动态特性得到改善。本文所提出的方法完善了填补黑洞的方法体系,增加了隔离壁精馏塔的灵活性与适应性。

While four-point control strategy （i.e.,the main compositions of the three products and the ratio between the two impurities in the intermediate product are controlled simultaneously） is used for the dividing-wall distillation column （DWDC）,the black-hole problem occurs and limits process flexibility and operability. In this paper,a philosophy was proposed to eliminate the black-hole problem with careful adjustment of the thermal conditions of feed and intermediate product. Through strong influence on the overall energy balance of the DWDC,these two variables affected the interlinking flows between prefractionator and main distillation column involved and could thus serve to coordinate their relationship. The dynamic responses were also improved after elimination of the black-hole problem. A simple rule was proposed to adjust the thermal conditions and three possible configurations could be obtained. The separation of a hypothetical ternary mixture,A,B,and C simulated with Aspen Plus,was chosen to evaluate the feasibility and effectiveness of the proposed philosophy. After steady-state analysis and closed-loop control studies,the results demonstrated that the black-hole problem could be completely removed through careful adjustment of the thermal conditions of feed and intermediate product. This philosophy brought the method of eliminating the black-hole problem to completion and enhanced the flexibility and operability of the DWDC.