Calculation And Simulation Of Crude Oil Distillation Process

Crude oil is an extremely complex mixture. Consequently, it must be processed so that many useful products can be obtained. Crude oil distillation is a process in which heating, fraction, and cooling methods are used to divide petroleum into different distillate fractions on the basis of the requirements of raw materials and downstream processing equipments. Generally, preprocessing, atmospheric distillation and vacuum distillation are included in the process.The crude oil distillation device whose processing capacity is 5 million tons per year was investigated and the design of atmospheric column was accomplished with Visual Basic according to the principles of crude oil distillation. And then, the primary and atmospheric columns were simulated by Aspen Plus simulation software according to the flow rates of petroleum fractions and the heat duties of pumparounds obtained by Visual Basic. Finally, the heat duties of pumparounds were calculated by calling Aspen Plus with Visual Basic on the basis of the principles of vacuum column design. Vacuum column was simulated in accordance with the data. The researches done in the paper are as following:ⅰ. MESH model was established according to the principles of distillation.ⅱ. Based on cumulative weight yield, volume yield and cutting scheme, three distillation curves of petroleum fractions were obtained.ⅲ. Densities of petroleum fractions were got on the basis of the density curve, and relative densities at 15.6℃were also calculated.iv. Average boiling points, molecular weights, characterization factors, true and pseudo critical constants, focus pressures, focus temperatures and acentric factors were computed from ASTM curves of each petroleum fraction.ⅴ. Enthalpies of petroleum fractions at certain pressure and temperature were obtained by enthalpy formulas.ⅵ. The number of stages in every section was selected according to the experience, and the temperatures, liquid and vapor flow rates were calculated through material balance and energy balance. Four-variable iteration was applied to calculate the temperatures at the top of column, in No.1, No.2 and No.3 side lines simultaneously. Once each temperature was changed, the residual energy would be recalculated and the energy in the column would be redistributed. Consequently, the results obtained by Visual Basic are more accurate than hand calculation. ⅶ. Based on the flow rates of petroleum fractions and the heat duties of pumpaounds in atmospheric column calculated by Visual Basic, primary and atmospheric columns were simulated by Aspen Plus simulation software.ⅷ. As to the design of vacuum column, the flow rates of the petroleum fractions at the top of column and in the side lines were obtained according to the cutting range. And then, the numbers of stages at each column section were selected on the basis of experience. After that, the heat duties at the top cycle and of the pumparouds were calculated by programming which were considered as the critical input data and were input into Aspen Plus. Finally, the distribution of temperature, liquid and vapor flow rates on each stage were obtained by Aspen Plus simulation software.In brief, when designing the process of crude oil distillation, accomplish the simulation by programming with Visual Basic firstly to obtain the critical process parameters, such as the flow rates of petroleum fractions, the temperature at vaporization section, the temperature in the heating furnace, heat duties of pumparounds, and so on. And then input the data into Aspen Plus, and run the simulation to get the temperatures, liquid and vapor flow rates on each stage.