Design of a Minimum Energy/CO2 Emissions Distillation Column for Separation of Close Boiling Mixtures
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Poster Session (EPIC - Poster) - P2
Keywords: Distillation, Heat integration, Energy efficiency, CO2 emissions, PP-splitter
An internally heat integrated distillation column, HIDiC, offers the maximum energy saving potential for difficult and energy intensive separations, such as propylene-propane and the like, which are carried out in tray columns. Since the stage requirement differs considerably for rectification and stripping sections, there are several possibilities for heat coupling, which, as experienced, strongly affect the heat transfer duty and consequently heat transfer area requirement per stage. Coupling all stripping section stages with equivalent number of stages in the upper part of rectification section appeared to be the best option in this respect. Simulations indicate that energy requirements and CO2 emissions generation of this HIDiC are respectively 25 % and 36 % lower than that of a state of the art vapor recompression column. This HIDiC configuration was translated into a concentric distillation column design, with low pressure annular stripping section configured around a high pressure rectifying section, with integrated part placed above the conventionally designed part of rectification section column. Heat transferring panels are placed on the active area of an annular type stripping section sieve tray, which was developed and evaluated experimentally at the TU Delft. Results of total reflux experiments carried out at atmospheric pressure using cyclohexane/n-heptane system obtained in a 0.8 m diameter pilot plant were used to validate literature models for the prediction of the heat and mass transfer efficiency and pressure drop. The separation efficiency and pressure drop of this complex annular tray resemble those of a conventional cross flow sieve tray. The heat panels appeared to have a significant enhancing effect on tray efficiency, without affecting the pressure drop and/or capacity adversely. The obtained values of the overall heat transfer coefficients and mass transfer efficiency were used to design a HIDiC version of a state of the art, stand alone propylene splitter. It appears that an equivalent HIDiC PP-splitter could be realized at a 20 % lower total annualized cost. With increasing energy costs, this gain tends to increase, and with energy cost making 70 % of total annual cost the moment is not far when building such a capital intensive column will be economically justified. However further scale-up relevant research is needed to ensure certainty regarding the level of heat transfer efficiency expected under actual operation conditions.
Presented Thursday 20, 13:30 to 14:40, in session EPIC-1: Poster Session (EPIC - Poster) - P2.
