Flow Optimization For Atmosphere And Vacuum Distillation Unit Based On Thermodynamic Analysis

Energy is the material base of human activity and doubtlessly saving energy is also a significant issue met with academia and industry societies. Crude distillation is so energy intensive that it reportedly requires up to 20-30% of the total that of the whole refinery. Presently, the energy conservation measures for this distillation unit are spontaneously directed to improving the energy recovery, which becomes more and more difficult along with the progress and maturity of technology in this respect. Therefore, further energy saving lies in diging latent capacity from process energy supply through process optimization. To make the whole thing worse, crudes and their features for more and more refinery distillation unit have been changed, sometimes from heavy to light. Thus, designing process scheme based on experience can hardly reach a satisfying result. In this regard, this work focuses its attention on thermodynamic analyses, screening and combination or development of two schemes individually for light and heavy cases. The whole work started with field investigation of two running atmospheric and vacuum distillation units, with their feeding, heavy and light respectively.First, operational data from the spot were collected and processed. Then Aspen Plus platform was applied to these 2 operative modes. The simulation results describing the original flowsheet were in good accordance with the plant data, which provided datasets to thermodynamic analysis. Furthermore, the new distillation curve was deduced by plant data. And the clustering analysis of three kinds of crude was done to examine the close or distant relationships among them. This indicates that the revised distillation curve obtained is in proper range.Then based on in-depth analysis on pre-distillation unit, atmosphere distillation unit and vacuum distillation, only the schemes of pre-distillation unit were changed aiming at revamp device, and various schemes of three units were used to carry out the permutation and combination for new device. The optimum process flows, evaluated by exergy analyses, orthogonal testing method and R software, were proposed aiming at crude with different property.After the accomplishment of the process level optimization, Column Grand Composite Curve (CGCC), sensitivity analysis and off-line optimization were applied to optimize the column inner to reach a sound completion. In all, a system analysis and fully optimization on this issue is made based on a mass of field data under thermodynamic principles. This approach and its results can gave reference to researches about energy analyses on similar units, as well as guidance to industrial practice on process optimization.