Retrofitting of a distillery based on process synthesis

This work points out some improper heat exchanger settings and retrofit modifications by the process integration technology, studying the case of the five column alcohol distillation section, which is broadly used in new distilleries in China. In the rectification grand composite curve, there is a mass of secondary vapor with the temperature of about 80 °C, below the pinch. Some of it is used as the heat source for the LiBr-H₂O absorption refrigerator through the single effect refrigerating cycle, and therefore, this part of the secondary vapor is changed into liquid without condensation and cooling. At the same time, the low temperature cooling water is generated from the refrigerating cycle, and it can be used in the other sections, except the distillation, like the fermentation and cooling the end product. The other secondary vapor is upgraded by the heat pump to replace the partial heating steam. After the above retrofitting for the distillery with the annual yield of 49,416 kl, 247.1 t/h low temperature cooling water can be obtained to replace the deep well water completely; the amount of heating steam and recycled cooling water, respectively, is decreased by 8.257 t/h and 205.9 t/h, but the power consumption is raised by 445.6 kW for driving the heat pump compressor. By thermoeconomic analysis, the following performance of the retrofitting case can be achieved: an overall investment of 7,476,900 ¥RMB, savings of 7,452,100 ¥RMB/year in the operating cost and savings of 187.5 ¥RMB/t in the production cost, the pay back period will be 1.01 years.