Analysis Of Factors Affecting Operation Of Alkylation Plant And Countermeasures

In recent years,the international community has paid increasing attention to the issue of environmental protection and energy shortages.The petrochemical industry is facing unprecedented shocks.Refinery enterprises must respond to environmental protection policies and achieve full utilization of resources.Alkylated oil is an important clean gasoline component in the petroleum refining industry.It is a kind of saturated alkane product,mainly isooctane,produced by the addition reaction of isobutane and butene under the catalysis of strong acid.Alkylation units can convert refinery liquefied petroleum gas into high-quality and clean alkylated oil.In addition,with the acceleration of upgrading of oil products in recent years,the market demand for alkylated oil will increase.Based on the production of 200,000 tons/year of alkylated oil,this paper uses the mixed carbon four of a refinery in Yan'an as raw materials to conduct a detailed study on the sulfuric acid alkylation process,and analyzes the components and impurities in the raw material composition.The operating pressure,number of trays,feed position,reflux ratio,production volume and other influencing factors in the pretreatment process and product fractionation process,as well as the influencing factors such as temperature and acid run-off in the alkylation reaction process,are deeply analyzed.On this basis,we propose a dual optimization strategy to improve the production process and realize the process and products,The external standard method and the normalization method are used to analyze the raw material composition of the alkylation production device though experiments,and the Aspen Plus process simulation software is used to optimize the entire process to obtain the best product quality and the best production process.Based on process characteristics and material properties,appropriate unit modules and physical property methods were selected.Among them,BWR-LS was selected for the hydrocarbon phase mixture,and ELECNRTL was selected for the acid-hydrocarbon mixed phase.Then a preliminary simulation of the entire process flow was carried out,and though continuous debugging,the results showed that the process had converged and a higher quality alkylate oil was obtained.The paper conducted optimization analysis of each section of the process and paid special emphasis on sensitivity analysis of the light-hydrocarbon removal tower,n-butane removal tower and isobutane removal tower.After the raw material is pretreated by the light hydrocarbon removal tower,it basically does not contain components below C₃.The mass fractions of dimethyl ether and butadiene are reduced to 5.26mg/L and 69.8mg/L obviously;after the optimization design of the alkylation reaction section,the reactor temperature is stable at about 10?,the reactor pressure is 1.5?2MPa,and the mass flow rate of circulating isobutane is 7.33×10³kg/h,which meets the design requirements.The optimum operating parameters of the column after optimization are as follows:the number of trays is 20,the liquid feed on the 10th tray,the reflux ratio is 1.7,and the recovery rate at the top of the column is 76kmol/h.The optimal operating parameters of the deisobutane tower are that the number of theoretical plates is 100,the position of the feed plate is the 60th,the reflux ratio is2.09,and the output at the top of the tower is 453.11 kmol/h.Based on the optimization of each section,the whole process was simulated again,and the final alkylated oil output was2.66×10⁴kg/h,of which trimethylpentane accounted for 92%and dimethyl hexane accounted for 3.95%.The research octane number(RON)is 95.7,and the motor octane number(MON)is 96.2.Based on the annual operating hours of 8,500 hours,the design scale of this process alkylated oil is 226,000 tons/year.