Mechanism Study On The Temperature Runaway Of Ethylene Epoxidation Reaction

Ethylene epoxidation reactor, carrying out reacting gas-solid catalytic reaction, is a kind of important chemical machinery. In recent years, temperature runaway was occurreds frequently in domestic fixed-bed reactors. Temperature runaway may be results in catalyst burnout, carbon deposition on tube walls, tube and housing damages and device shutdown, and even lead to serious explosion accidents. Temperature runaway reactor is mainly caused by abnormal conditions. When the heat released from exothermic reaction in reactor could not be removed timely, a great quantity of heat will accumulations localized in reactor bed, the temperature will rising sharply, and then the temperature runaway. A lot of manpower and material resources are necessary to deal with temperature runaway. Therefore, preventing temperature runaway is particularly important in the ethylene epoxidation process. According to the condition, the dissertation analyse the ethylene epoxidation reaction system by the HAZOP, focuses on the mechanism study of temperature runaway of the ethylene epoxidation reactor and the cause analysis of the temperature runaway of the reactor. It is shown that, the cause of ethylene epoxidation reactor temperature runaway may be related to the reactor feed flow rate, feed temperature, the cooling medium temperature, the catalyst distribution, and other factors. These parameter deviations could be analyzed qualitatively by HAZOP analysis, but could not be provided to the effect on the temperature of the system accurately. So the quantitative analysis will be necessary. Based on the homogeneous two-dimensional mathematical model of ethylene epoxidation reaction, the quantitative analysis and the verification of HAZOP analysis result were made from the aspect of operating parameters. Analysis shows that:if the feed flow rate is too small or the feed temperature is too high or cooling medium temperature is too high, the reactor temperature rise sharply and runaway. Meanwhile, the quantitative analysis and the verification of HAZOP analysis were made from the aspect of catalysts and reactor design by the simulation of the fixed bed reactor using the CFD software. The results showed that, the reactor pressure drop is reduced with the increase of the void ratio, and increased with increases in catalyst rotation angle and the gas inlet velocity. The heat transfer effect gets better with the decreases of the void ratio and inlet velocity and the increase of the catalysts rotation angle. According to the HAZOP analysis of ethylene epoxidation reaction system, and the quantitative analysis and the verification of HAZOP analysis by the homogeneous two-dimensional mathematical model and CFD software. The dissertation study on the mechanism and the cause of ethylene epoxidation reactor temperature runaway, and effect of multi-parameter coupling on ethylene epoxidation reaction system. The study provides a theoretical basis for the fixed-bed reactor intrinsically safe design, ensuring production safety, and avoiding the accidents.