Combined optimization of vacuum distillation and lube oil processes for energy savings
Lube type vacuum distillation units in refinery complexes are continuous processes and have several side streams such as vacuum gas oil (VGO), including light vacuum gas oil (LVGO), medium vacuum gas oil (MVGO) and heavy vacuum gas oil (HVGO), which feed to lube oil plants as crude materials. Generally, lube type vacuum distillation units can shut down some side streams selectively, which are characterized as operating modes and results in different energy consumption level. There are some storage tanks for the three vacuum side streams in refinery complexes. On the other hand, lube oil units have several operating modes. Each operating mode processes a kind of VGO from vacuum distillation units, and lube oil units can not process the three vacuum side streams simultaneously. Each operating mode of lube oil units results in different products. So, it is important for energy savings and reducing the production costs of lube oils that how to optimize the production periods and capacity of each operating mode under the constraints of the lube oil markets, the price of crude materials, energy costs of each operating mode, the storage space of VGO and other operating costs. Firstly, the energy consumption level of each operating mode of lube type vacuum distillation process is investigated in this paper. Each operating mode of lube type vacuum distillation process results in different energy consumption. Three operating modes of vacuum distillation process are proposed. First, LVGO is in operating and MVGO and HVGO shut down. Second, LVGO and MVGO are in operating, and HVGO shuts down. Third, the three vacuum side streams are all in operating. Crude distillation curve is introduced to predict the energy consumption level of each operating mode of vacuum distillation process according to the properties of crude oils and VGO. Process simulation is also employed to model each operating mode to correct energy consumption level predicted by crude distillation curve. Secondly, a mixed integer linear programming (MILP) model optimizing vacuum distillation and lube oil processes simultaneously is presented for energy savings in this paper. The objective of the presented model is to minimize the production costs which include material costs, energy costs, inventory costs and fixed operating costs, and to optimize the production periods and capacity of each operating mode, material stream flow and inventory level of VGO. The proposed model involves material balance constraints, energy consumption constraints of each operating mode, inventory level constraints, and so on. Thirdly, the presented model has been applied to a refinery complex in North China to demonstrate their performance. The optimal results are profitable and operable, and specific energy consumption is reduced. Finally, some important conclusions have been drawn.
Optimization Energy MILP Model Lube oil
B.J.Zhang Q.L.Chen
The Key Laboratory of Enhanced Heat Transfer and Energy Conservation,Ministry of Education,South China University of Technology,Guangzhou 510640,China
国际会议
西安
英文
2007-08-15（万方平台首次上网日期，不代表论文的发表时间）