Optimization Of Grade Transition For The Slurry High Density Polyethylene Process

There are some shortages in Chinese polyethylene production, such as unstable grade transition, wasting a lot of time and producing a huge amount of off-specification product and so on. It wastes a lot of human work and raw material, which seriously impacts on our polyethylene products market, and reduces the international competitiveness of polyethylene. To solve the above problems and satisfy the customer's demand for product with various qualities, this paper uses the HOSTALEN slurry high density polyethylene production process of BASELL of a petrochemical company as an example, forcing on the research of grade transition problems of high density polyethylene production process. The main research jobs are as follows:First, analyze the polyethylene production process and polyethylene grade transition process respectively on switching modes, influencing factors, switch targets and switching strategies, and demonstrate the significance of the subject.Second, research the impact of reactor pressure, temperature, ratio of hydrogen to ethylene and ratio of 1-butene to ethylene to the polymerization of HOSTALEN slurry process and production plant. Then do some research of soft sensor to the performance parameters of polyethylene, analyzing the relation between performance parameters and operating variables affecting.Third, according to the slurry process conditions and catalyst features, list the reaction mechanism equations of high-density polyethylene, and obtain the dynamic model of HDPE. Afterwards, do some pretreatment for the data collected from the plant as data fusion, detection and treatment of abnormal data and data mean filtering. Then use the data treated to regress the parameters of the dynamic models, and obtain the semi-empirical and semi-mechanism models of melt index and density. At last, do a verification of the models.Finally, establish the optimal objective function of the slurry HDPE grade transition process, and use iterative dynamic programming algorithm to resolve the objective function to obtain the trajectories of both operating variables and quality target of product, such as polymerization temperature, ratio of hydrogen to ethylene, ratio of 1-butene to ethylene, melt index, density and so on. Then calculate the transition time and the amount of off-specification product.