The Simulation And Optimization Of A Crude Distillation Unit And Its Heat Exchanger Network

Energy is the foundation of human being's material production activities. The atmosphere-vacuum distillation unit consumes the most energy in a refinery, which occupies twenty percent to thirty percent of energy consumption in the entire refinery. So, optimizing the heat exchanger network and maximizing the energy-saved are of great importance. This paper takes the flow simulation and optimization of heat exchanger network of atmosphere-vacuum distillation unit as the research. We apply theory of flow simulation and optimization of heat exchanger network to simulate the distillation process, and to optimize the heat exchanger network. Detail researches are summarized as below.This paper provides a critical review of the literature on heat exchanger network synthesis, the most commonly problem in process synthesis. Three methods of heat exchanger network synthesis including pinch technology, mathematics programming method and artificial intelligence method are reviewed. The contents, methods as well as the chronological milestone in the development of these methods are presented.According to the flow of atmosphere-vacuum distillation unit, the paper applies sequential modular method on flash tower, atmospheric tower and vacuum tower to perform process simulation. First of all, crude oil is cutting into several pseudo components which act as input of flash tower according to its true boiling points data. Secondly, proper module unit and convergence method are selected, and simulation models and process parameters are regulated subsequently. At last, process simulation of flash tower, atmospheric tower and vacuum tower are calculated in turn. The simulation results show good agreement with the rating data. Creditable results of flow simulation provide optimization with firm foundation.In the process of atmosphere-vacuum distillation unit simulation, the author consults many data and finds most researchers ignored to add heat exchangers to bring the flash tower, atmospheric tower and vacuum tower into a unified whole. Therefore this paper adds all the heat exchangers that have been used to provide more accurate data for the optimization of the heat exchanger network.According to the pinch theory, if cooling utility is used up the pinch, heating utility is used down the pinch or the heat exehange streams across the pinch, there will be double loss in the utility. By means of improving the streams match properly, we can decrease the consumption of the utility in the heat exchanger network.This paper uses system energy synthetical analysis technology to analyse the whole heat exchanger network. Then we gradually understand the unit's currnet energy consumption situation and find the"pinch"of the plant's heat exchanger network. We find how to solve the problem using pinch technology. Firstly, we set up the heat exchanger network's model of minimized annual cost. Secondly, we find where the pinch is and make sure the appropriate heat exchanger network. Finally, we optimize the process flow, existing equipments and energy recovery using calculated datas.The retrofit heat exchanger network obtained, where there is a little modification involved, has basically maintained the present installment situation. All the exsting equipments are completely reused and only three heat exchangers should be added. Moreover the end temperature of the crude oil is remarkably enhanced. Thus the paper has guidance meaning for practical manufacture.