Research On The New Process And Optimization Of The Fractionation System Of Kerosene-diesel Hydrocracking Unit Based On Ejector And Light Naphtha Absorption Process

With the rapid development of large-scale refining and chemical integration projects,oil products are gradually transforming into chemical products.Kerosene-diesel hydrocracking units are being paid more and more attention due to their rich production of light and heavy naphtha,which can provide raw materials for the ethylene and aromatics industry.However,the fractionation system has high energy consumption due to the large amounts of products,many distillation towers,absorption and stablizaiton system.Therectfore,this paper developed a new fractionation process.It extracts a strand of light naphtha from the upper part of the hydrogen sulfide removal tower to replace the circulating heavy naphtha as the absorber of the absorption tower,which greatly reduces the capacity of the absorption and stablizaiton system.Besides,the lost static pressure energy of the cold low-fraction oil is recovered by the ejector to inhale and compress the top gas from the hydrogen sulfide removal tower,which can lower the pressure of the hydrogen sulfide removal tower,and keeps the pressure of the absorption tower unchanged at the same time,thereby reduce the energy consumption of the hydrogen sulfide removal tower and replace the diesel product heat to produce 1.0 MPag steam.The calculation of a 3.6 million tons/year kerosene-diesel hydrocracking fractionation system shows that the new process saves 276.4Nm³/h of heating furnace gas,a decrease of 11.6%,produces more 1.0MPag steam by 9.7t/h,recovers 41.4KW pressure energy of cold and low oil.The economic efficiency increase is 28.376 million yuan per year.Furthermore,a research method of multi-variable,single-objective operation optimization of chemical unit based on simulation data is developed.It uses the COM server which comes from PRO/?to connect PRO/?with Excel.Then the PRO/?data can be input and read in Excel sheet,GA algorithm code and the code to ensure PRO/?operate automatically and rightly can be written in the Excel VBA code editor,thereby integrating the simulation function of PRO/?,the data processing function of Excel and the global optimization function of GA,to realize multi-variable automatic optimization under the Excel interface.Finally,it is applied in a new process of the fractionation system of a 3.6 million tons/year kerosene-diesel hydrocracking unit.In this application,this paper regards the operating pressure of cold and low oil separation tank(x₁),the operating pressure of hydrogen sulfide removal tower(x₂)and the flow rate of circulation heavy naphtha absorbent(x₃)as independently adjustable operating variables,with the minimum energy consumption of the system as the objective function and under the condition of meeting the constraints of product yield and quality.In addition,with the use of the methods of ejector's structure design and optimization based on CFD and after the calculations of GA,it is found that when X=(1863,423.9,6.7),the total energy consumption of the system is the smallest,which is 2866×10⁴kcal/h.Compared the operation condition X=(1700,512.0,8.0)of the new process,the heating furnace gas consumption is reduced by 102m³/h,the recovery of the cold and low oil pressure energy is increased by 28.3KW,the 1.0MPag steam output remains unchanged at 9.7t/h,the economic efficiency is increased by 2.725 million yuan per year.The efficiency of the gas-gas ejector is increased by 8.6 percentage points,which has an increase of47.3%.And when compares with the old process,The process after GA optimization can save31.101 million yuan per year.It shows that the chemical unit operation optimization method established in this paper is effective and feasible,and it is suitable for the multi-variable,single-objective operation optimization study of all chemical units that can be simulated.