OPERABILITY INVESTIGATION OF ENERGY INTEGRATED DISTILLATION SCHEMES

摘要

Two energy integrated distillation schemes for the separation of three different ternary mixtures of four different feed compositions have been rigorously investigated and compared to the best conventional two-column scheme. The two energy integrated schemes are: The heat integrated two column system and the fully thermally coupled distillation column known as Petlyuk column. The comparison of the energy savings and the total costs of the investigated schemes show that the two column heat integrated scheme is always economically better than the conventional scheme. The Petlyuk column shows considerable energy savings in several cases, however, it can be competitive with the heat integrated two column system only in those rare cases where the concentration of the middle component is high, the split between the first and second component is harder than the split between the second and third component, and the separation is not too sharp. The rigorous economic study is supported here by operability studies for the two energy integrated distillation schemes. The operability studies are performed at two operating conditions. Degrees of freedom analysis and steady-state multivariable control structure synthesis tools show that both investigated schemes can be controlled by conventional decentralised control structures, however, in the case of the heat integrated two column scheme heuristics and also the steady-state control indices show that the interaction among the control loops is less than in the case of the fully thermally coupled distillation column.