CONTROL OF A HEAT-INTEGRATED COMPLEX DISTILLATION CONFIGURATION

Several steady-state design studies of distillation systems that combine complex configurations (prefractionators and sidestream columns) and heat integration have appeared in the literature and have shown the potential for large reductions (50%) in energy consumption compared to conventional designs. However, the dynamics and control aspects of these highly interactive and multivariable systems have been virtually unexplored. This paper presents the results of computer simulation studies of the dynamic controllability of a complex heat-integrated distillation system for the ternary mixture of benzene, toluene, and m-xylene. Both low- and high-purity separations were explored. For the low-purity (95% product purities) separation, the complex heat-integrated system was found to be controllable by using conventional diagonal SISO controllers. Dynamic responses were comparable to the simple conventional system. For the high-purity (99.9%) separation, the complex heat-integrated system was found to be controllable but could only handle small (<10%) feed composition disturbances and was dynamically worse than the conventional system. © 1990, American Chemical Society. All rights reserved.