Heat Integrated Reactive Distillation Designs for Hydrolysis of Methyl Acetate
Hao-Yeh Lee, Hsiao-Ping Huang, and Yi-Chen Lee. Chemical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, Taiwan
In this paper, two designs of heat-integrated reactive distillation for the hydrolysis of methyl acetate are studied. The first one employs internal heat-integrated reactive distillation column (r-HIDIC) and the other utilizes feed-split reactive distillation column (r-FS). The savings in energy consumption and total annual costs are focused on the reactive column only. The reference base case for comparison is the RD column in the work of Lin et al. (2007). In both cases, part of the reactive distillation utilizes a higher pressure. This is because a higher pressure makes heat transfers in the system possible. In fact, this higher pressure benefits the reaction taking place. Because, the hydrolysis reaction of methyl acetate is slightly endothermic, a higher operating pressure implies higher temperatures, faster reaction rates, and better equilibrium constants in the reaction part. The energy conservation studies show that HIDIC can reduce energy saving up to 27%, and FS had 38% saving when the process conditions are both optimized. Nevertheless, as far as economic aspect is concerned, HIDIC has no benefit, because of 33% more total annual cost (TAC) than the original RD column is required. This is due to an expensive gas compressor which takes 61.9% total capital cost and 31.3% utility cost. On the other hand, FS has a better economical efficiency with 6.4% TAC and 15.2% operating cost savings. FS has two smaller distillation columns but the capital cost is almost same as the original one. Raising the operating pressure in one part of the RD columns increases the temperature and the reaction rate which, in turn, results in smaller equipments and catalyst requirements.