OPERABILITY INVESTIGATION OF ENERGY INTEGRATED DISTILLATION SCHEMES

Two energy integrated distillation schemes for the separation of three different ternary mixtures of four different feed compositions have b een rigorously investigated and compared to the best conventional two- column scheme. The two energy integrated schemes are: The heat integra ted two column system and the fully thermally coupled distillation col umn known as Petlyuk column. The comparison of the energy savings and the total costs of the investigated schemes show that the two column h eat integrated scheme is always economically better than the conventio nal scheme. The Petlyuk column shows considerable energy savings in se veral cases, however, it can be competitive with the heat integrated t wo column system only in those rare cases where the concentration of t he middle component is high, the split between the first and second co mponent is harder than the split between the second and third componen t, and the separation is not too sharp [1]. The rigorous economic stud y is supported here by operability studies for the two energy integrat ed distillation schemes. The operability studies are performed at two operating conditions. Degrees of freedom analysis and steady-state mul tivariable control structure synthesis tools show that both investigat ed schemes can be controlled by conventional decentralised control str uctures, however, in the case of the heat integrated two column scheme heuristics and also the steady-state control indices show that the in teraction among the control loops is less than in the case of the full y thermally coupled distillation column.