Optimization Of Heat Exchanger Network For Atmospheric-Vacuum Distillation Unit In Refinery

With the rapid development of society,efficient use of energy has become the focus of the governments and enterprises.The pinch technique theoretically derives the minimum energy demand,provides direction and limit for the design of heat exchanger network and effectively guarantees the establishment of the heat exchanger network with maximum energy recovery,which has made great contributions in the fields of energy saving and emission reduction.The use of pinch technique for energy system integration to improve the overall energy utilization efficiency of the refinery is of great significance to China's refining industry and sustainable economic development.In the refining industry,the atmospheric-vacuum distillation unit consumes a lot of energy,and the level of energy conservation directly affects the economic benefits and market competitiveness of refining enterprises.Therefore,energy saving is studied for this unit in this paper.By evaluating and weighing the annual capital cost target and annual operating cost target under different pinch temperature differences,the pinch temperature difference with the best economic benefit can be selected for the heat exchanger network.However,the capital cost target of a complex heat exchanger network is difficult to calculate accurately.Therefore,this paper studies how to improve the accuracy of capital cost target calculation by constructing a calculation model.The calculation model both considers the difference of the heat transfer coefficients of the streams and the difference of the cost equations of the heat exchange units.The results show that the accuracy of the calculation model is better than the accuracy of Aspen Energy Analyzer,which is beneficial to improve the calculation accuracy of the optimal pinch temperature difference.Process simulation software reproduces the actual production process,facilitating production optimization and technical reform.Therefore,this paper will carry out the whole process simulation of the atmospheric-vacuum distillation unit in Aspen HYSYS,and call Aspen EDR to strictly design each heat exchanger to improve the process simulation accuracy.After the process simulation has been completed,the data is extracted to the Aspen Energy Analyzer.Then the energy usage of atmospheric-vacuum distillation unit is quickly diagnosed and the utility target is obtained.The structure of the heat exchanger network of the atmospheric-vacuum distillation unit is very complicated and there are many possibilities for the selection of the retrofit.In this paper the heat transfer across the pinch is reduced by rationally rearranging the heat exchange unit,adding the heat exchange unit and increasing the heat exchange unit area,which is based on pinch technique,thus reducing the energy consumption of atmospheric-vacuum distillation unit.According to the principle of minimum modification and taking into account the energy saving potential of the unit,the optimal retrofit is determined.After the retrofit,the temperature of the crude oil into the atmospheric column furnace is increased from 287.3? to 315.0?.By economic analysis of the optimization scenario,the result shows that the heat exchanger network optimization has achieved good economic benefits: the investment cost is only 42.55 million yuan,and the annual operating cost can be saved by 64.85 million yuan,and the investment recovery period is 0.6561 years.The study results in this paper have certain reference and guiding significance for the optimization and retrofit of the same type of unit.