Vapor Recompression Column Research Articles

98/00675 Optimum performance of a corrugated, collector-driven, irreversible Carnot heat engine and absorption refrigerator

Many developed energy efficient configurations based on heat-integrated distillation column (HIDiC) have been proved to be attractive separation alternatives for saving energy. The key limitation of heat integrated technology is how to build splendid schemes for the heat integrated distillation column. In this work, the overall economic evaluation of conventional distillation column (CDiC), basic heat-integrated distillation column (basic HIDiC) and vapor recompression column (VRC) were executed systematically. Based on the comparison of results, by coupling the basic HIDiC with heat pump technology, a new distillation process model was developed as an intensified HIDiC (int-HIDiC) configuration for propylene-propane splitter. By this enhanced heat integration, the reboiler and the low pressure steam were no longer needed in the process. Meanwhile, the heat distribution proportion and the corresponding operating conditions of this int-HIDiC were optimized through vast simulations and computations. Finally, based on the above optimization results, we developed a simplified HIDiC configuration with two separated columns. The results show the better economic and energy performances than all the other energy-saving schemes including VRC.

Basic Analysis of Rectification Energy

(1) In the schematic arrangement of the reversible rectifying column, it is desirable that it resembles the actual column as nearly as possible and yet be clearly reversible.(2) The deviation in the relationship between temperature and heat input or output of an irreversible column compared with that of a reversible column was examined. In the irreversible column m (<1) and K (positive integer) were induced as parameters of the shape of the relationship between temperature and heat input or output.(3) Fig.8 illustrates graphically how the required work is increased from a reversible column to a vaporrecompression column. This suggests that the work of compression in a vapor-recompression column can be reduced by the following mean:1) Reduction of the reflux ratio, 2) Use of a rectifying column equipped with a secondary still or a secondary condenser, or the use of successive rectifying columns, 3) Modification of the tower construction for larger heat transfer area, higher heat transfer coefficient and lower pressure drop through the column, 4) Recovery of mechanical energy from the excess vapor of the plant, 5) Improvement of the compressor efficiency.(4) Table 2 shows numerically the difference in work balance between the steam heating process and the vapor recompressin process. According to Table 2, the reflux condenser loss is recovered by the use of the vapor-recompression method. Next, in the case of the vapor-recompression process of the adiabatic column, the tower loss becomes the largest loss, and the adoption of a column equipped with a secondary still is a method which will further reduce the required work by reducing the tower loss. In the case of the vaporrecompression column epuipped with a secondary still, the still loss becomes the largest loss. Consequently, Table 2 poses questions concerning the most effective type of tower construction which reduces the still loss and hence, reduces the required work.