COMPLEX THERMAL INTEGRATION OF THE RECTIFICATION PROCESS OF THE BENZENE-TOLUENE MIXTURE

Abstract

Comprehensive thermal integration of the benzene-toluene mixture rectification process was carried out. Thermal integration was carried out using pinch analysis methods with using thermocompression. The principle technological scheme of rectification of the benzene-toluene mixture with a productivity of 11 t/h is taken as a basis. For this performance, the consumption of flows, their temperatures, heat load, and flow heat capacities are calculated on the basis of the material and heat balance. Based on the calculated data, a flow table was created. Three hot streams are selected for integration: the distillate, the tailings, and the vapor from the top of the column, and two cold streams: the initial mixture and the column cube. The necessary degree of vapor compression is calculated for thermocompression. For a given degree of compression, the temperature of the steam after compression and the temperature of its condensation were calculated. Based on the technical and economic considerations, the minimum temperature difference DTmin=12 °С was determined for this technological scheme of the rectification process. For the selected DTmin, the component curves of the flows are constructed. Using the table algorithm method, the temperatures of the furnace for hot and cold flows were determined, which are ТНpinh=82 °С, ТСpinh=70 °С. The minimum number of hot and cold utilities is determined: QНmin and QCmin. For the selected DTmin, heat recovery was obtained in the amount of Qrek=2186,82 kW. A grid diagram is constructed, heat exchangers are located in accordance with CP and N rules. A technological scheme of the rectification process after reconstruction using thermocompression is proposed. The upgraded scheme includes the use of four recuperative heat exchangers, one heater and two coolers to achieve target flow temperatures. It is recommended to install a compressor for thermocompression. The use of Alfa Laval plate heat exchangers is proposed as heat exchange equipment. The payback period of the proposed solution is approximately two to two and a half years.