Simulation Study Of Delayed Coking Unit And Optimization Of The Energy System

Energy consumption has increased dramatically resulting in the tight energy supply, sogovernments and enterprises begin to attach importance to energy conservation. Delayedcoking process is one of the most important processes converting heavy oil to light oils. It hasattracted much attention due to its low investment and simple process. Meanwhile, delayedcoking technology can obtain higher economic benefits because its yield of light oils is higherthan others. As the crude oil processed in the refinery is getting heavier and heavier andenergy-saving situation is extremely critical, it is of great significance to save energy andreduce consumption of the oil refining enterprises, especially the delayed coking unit.Taking a delayed coking device of domestic petrochemical enterprise for an engineeringexample, the raw materials, products, process flowsheet of delayed coking and thedevelopment trend are briefly introduced in this paper. According to the operation parameters,product properties, etc of the delayed coking unit provided by the refinery, Aspen Plussimulation model is established for the main fractionator and absorption stabilization systemwith simulation strategy for delayed coking process, such as the component prediction of thereaction oil and gases, the selection of thermodynamic methods in vapor-liquid equilibriumcalculation, the estimation of tray efficiencies and the simplified model built for simulatingthe desuperheating section of the main fractionating column, etc. Through the analysis ofsimulation results, the deviation of simulation value and measured value is within the errorrange, which shows that the simulation model is accurate, the calculation results is reliableand can be used for energy system analysis.The energy sysytem of the delayed coking unit is analyzed according to the measures forimproving energy consumption in typical delayed coking process. The results shows that thedevice has made full use of the internal heat matching, reduced the use of utilities and recycled the low temperature heat of gasoline and diesel products. Therefore, mainly the heatexchanger network of the delayed coking unit is optimized. The paper first provides a briefintroduction to the pinch technology and its application in the heat exchange network designand optimization. The streams data of the main fractionator and absorption stabilizationsystem is extracted into the pinch analysis software, Aspen Energy Analyzer. Pinchtechnology is applied to the delayed coking unit for pinch analysis and energy diagnosis, theheat exchanges contrary to pinch rules are eliminated and the heat load loop and path in theimproved heat exchange network are broken to obtain the final heat exchanger network. Heatexchanger design and rating software HTRI is used for designing new or modified heatexchangers. The energy cost savings and the investment are calculated, results show that thepayback period is less than three months. Therefore, the pinch technology for delayed cokingprocess is very important to reduce the energy consumption and improve the economic profits,which can provide guidance for energy conservation of same refinery units.