Simulation & Optimization On Atmospheric-vacuum Distillation Unit

In 2006, the capacity expansion adaptive revamping of atmospheric and vacuum distillation unit No.2 in CNPC Urumqi refinery had been made, of which the capacity of process crude oil had been increased to 3,500,000 tons per year. The unit remains running stable now. However, some problems still exist when we make analysis to the Engler curve of the main products, such as low separation precision of product and high fraction of light residual oil. In order to obtain high yield of light oil and the stripping rate of crude oil, several studies have been made as follows:1) After scientific and rational programming, based on calibration data of atmospheric and vacuum distillation unit No.2 in CNPC Urumqi refinery, the simulation flowsheet of crude unit was established .2) Large number of simulation was made with five kinds of property methods commonly recommended for refining process. Based on the simulation results error analysis under different property method, an optimal method was obtained.3) Sensitivity analysis to the key factors, such as operating pressure, feed temperature and flow rate of stripping steam, affecting on feed stream Vaporization ratio or the stripping rate of crude oil was done with Sensitivity analysis tools on Aspen Plus software. The simulation results demonstrated the crude oil stripping rate can be increased 6.8 centigrade if the optimal adjustment project were used. The optimal target has been obtained in the viewpoint of the stripping rate and economic maximization.4) Taken primary tower, atmospheric tower and vacuum tower feed location as the variables; the optimal process was obtained to maximize economic benefit by use optimization tools on Aspen Plus software.5) It was proposed two improved process schemes that "two flash tower-atmospheric tower-Vacuum Tower" and "two flash tower-atmospheric tower-two vacuum tower". The two improved schemes were also simulated on Aspen Plus and compared the simulation results with the original process scheme in the viewpoint of the stripping rate and energy consumption.