Optimization Of Heat Exchanger Networks Of Rectisol Wash Process

Nowadays, as the chemical plant tends to be large, intensive and continuous, the energy problem is becoming the main break on our social economy sustainable development. The energy conservation and the reduction of pollutant emissions are the general trend of the chemical engineering development. Heat exchanger network is the major part of the heat recovery method. Among the variety of heat exchanger network optimization technologies, pinch analysis gained a wide use in process engineering because of its intuitive physical meaning and convince.Rectisol wash process is a typical purification of physical absorption of acid gas component. CO2 and H2S have a large solubility in methanol at low temperature so that methanol is used to remove acid gases with a high purification and a large capacity. Rectisol wash process has been widely applied in over one hundred ammonia and methanol synthesis plants. Rectisol wash unit is operated at low temperature therefore coolant is used which is quite expensive. As a result, using pinch analysis to find the bottleneck of rectisol wash process and to optimize the HEN has a great practical significance.In this paper, RPS software was used to simulate the process stream data as the basis of the optimization of HEN, and then pinch technology was applied to analysis three typical rectisol wash units, plotting the minimum approach temperature vs. total annual cost to set an optimum minimum approach temperature. After that retrofit HENs of those rectisol wash units were proposed, showing great economic benefits. In the optimization of the HEN in the Linde process, an energy saving plan and a heat transfer unit number optimization plan were got, and economic analysis was carried out showing that the total annual cost of the retrofit plans were smaller than the original HEN. As for the HEN optimization of Lurgi process, two energy saving optimization plans were presented, which had great advantages over the original HEN in the economic analysis. In the optimization of a new rectisol wash unit HEN, plus/minus principle was used to guide a process change. At last some general rules were summarized in the HEN optimization of rectisol wash unit.