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Abstract: Despite the fact that a stand-alone ideal heat-integrated distillation column (ideal HIDiC) can be thermodynamically efficient and operationally stable, the application of an ideal HIDiC system to separate a close-boiling multi-component mixture is still a challenging problem because of the possibility of strong interactions within/between the ideal HIDiCs involved. In this work, employment of two ideal HIDiCs to separate a close-boiling ternary mixture is studied in terms of static and dynamic performance. It is found that the ideal HIDiC system can be a competitive alternative with a substantial energy saving and comparable dynamic performance in comparison with its conventional counterpart. The direct sequence appears to be superior to the indirect sequence due to the relatively small vapor flow rates to the compressors. Controlling the bottom composition of the first ideal HIDiC with the pressure elevation from the stripping section to the rectifying section helps to suppress the disturbances from the feed to the second ideal HIDiC. Special caution should, however, be taken when the latent heat of the distillates is to be recovered within/between the ideal HIDiCs involved, because a positive feedback mechanism may be formed and give rise to additional difficulties in process operation. [Copyright &y& Elsevier]

Abstract: In this work, a novel temperature control scheme is derived for an ideal heat-integrated distillation column (ideal HIDiC), in which a temperature difference between two stages is designated as the controlled variable to circumvent the side-effect of continuous pressure variations in the rectifying section. For making an appropriate compensation to the changes in operating conditions, an inferential signal extracted from the feed stage, , is used to adjust the set-point of the temperature difference controller. Control of two ideal HIDiCs, separating, respectively, a binary mixture of benzene and toluene and an ideal ternary mixture of hypothetical components A–C is studied. It is demonstrated that the proposed temperature control scheme can retain a stable operation around the vicinity of the nominal steady state with improved dynamic performance and tolerable steady state discrepancies in comparison with the direct composition control scheme. Moreover, the proposed temperature control scheme is also found to be quite robust to the selection of temperature measurements. [Copyright &y& Elsevier]

Abstract: Process intensification calls for the combination of two or more conventional unit operations within one framework, thus giving rise to a challenging coordination problem in process synthesis and design. Seeking synergistic effect among all the conventional unit operations involved is found to be an important principle for process development. Three cases of process intensification are studied to evaluate the principle, including: (i) a hypothetical reactive distillation system; (ii) a reactive distillation column for the hydration of ethylene oxide; (iii) an ideal heat-integrated distillation column. It is demonstrated that simply combining two or more conventional unit operations together does not necessarily tap out the full potentials of capital investment reduction and energy saving. Only after the synergistic effect has been deliberately considered in process synthesis and design, can process intensification be carried out in the most effective manner. Furthermore, seeking synergistic effect appears frequently to yield improved process dynamics and provide additional redundancy to process operation because the underlying conflicts could be attenuated among all the conventional unit operations involved. [Copyright &y& Elsevier]