Research On The Intrinsic Safety Design Of Ethylene Epoxidation Reactor

Ethylene oxide/ethylene glycol plant is the plant mainly used to produce organic chemical products ethylene oxide and ethylene glycol in the modern chemical industry. The fixed bed reactor, carrying out epoxidation reaction, is the main reactor in the ethylene oxide/ethylene glycol plant. Temperature runaway accident often occurs in the reactor, burning catalysts, leading to the reaction tube and shell damaged, plant shutdown, even seriously causing fire and explosion accidents, which cause heavy losses to countries, society and companies. The most fundamental method to prevent accidents is eliminating or controlling the potential risks in design phase to achieve the intrinsic safety of the plant. Based on the traditional engineering design method, the intrinsic safety engineering design method was proposed. Firstly, the method of Hazard and Operability Analysis (HAZOP) was used to research the risk in the ethylene oxide/ethylene glycol plant, identifying the potential risks and the reasons for causing these risks, forecasting the possible consequences, thus the corresponding suggestions and measures were put forward to prevent the spread of the risks. Secondly, according to HAZOP analysis results, the numerical simulation method of FLUENT software was utilized to quantitatively research the reasons for causing temperature runaway of the ethylene epoxidation reactor, to provide technology basis for the design of fixed bed reactor and catalyst, also setting safe operation conditions for the reactor. Finally, based on above research results, the intrinsic safety engineering design database of the plant was established to assist the intrinsic safety design, and could be utilized to provide theoretical guidance for the intrinsic safety design of the reactor, and the main contents are as follows:(1) The method of HAZOP analysis was used for qualitatively analyzing the ethylene oxide/ethylene glycol plant, identifying the potential risks, mainly analyzing the possible problems in the ethylene epoxidation reactor. Then the reason for causing temperature runaway of the reactor, the severity of consequence, the occurrence frequency of accident and the evaluation of risk rank are focused on, and the suggestions and measures were put forward to prevent accidents or control the consequence severity.(2) To quantitatively provide guidance for the intrinsic safety design experience of the reactor, the fluid flow and heat transfer of different catalyst arrangements in the fixed bed reactor are numerical simulated by FLUENT in this paper, and then the effects of the gas inlet velocity on bed pressure drop and wall heat transfer coefficient were analyzed under different void fraction. The simulation results has showed that on the basis of meeting process conditions and production requirements, the conclusion can be obtained that appropriate void fraction and the rotation angle of catalyst should be chosen for the design of ethylene epoxidation reactor, also the smaller gas inlet velocity should be chosen on operation to prevent the temperature runaway accident so that ensure the intrinsic safety of the reactor to realize the reactor run safely and stably.(3) The HAZOP analysis results of the ethylene oxide/ethylene glycol plant are summarized to classify the equipments. Then based on the combination of HAZOP analysis and FLUENT simulation results, a visual intrinsic safety engineering design database interface was established to achieve sharing and accumulation of the experience, so as to provide guidance for the intrinsic safety design of the reactor.