Quantitative Risk Analysis Method In Petrochemical Unit Production Process Based On Consequence Simulation

Petrochemical units, especially typical pressure equipment, usually work under extreme conditions such as high temperature, high pressure and in a hydrogen environment. Due to a large amount of poisonous, harmful flammable and explosive materials exist in the production process, a leakage failure of the equipment can easily result in a poison, fire or explosion accident, which may develop into serious consequences.With dangerousness and complexity in petrochemical units, only if we combine qualitative analysis with quantitative analysis can we obtain good risk analysis result with low cost. Risk will not be quantitative by qualitative analysis alone while a lot of time and energy will be wasted with no pertinence if we adopt quantitative analysis only. As a result, this paper utilize not only HAZOP analysis and bow-tie model, but also consequence quantitative calculation to conduct qualitative risk analysis for the entire unit and quantitative analysis for the partial equipment. Furthermore, this paper puts forward a quantitative risk analysis method for accident prevention in petrochemical unit production process based on consequence simulation which contain four main steps.Firstly, a HAZOP analysis should be conducted for the whole unit to identify all the potential leakage risks and indicate nodes or devices with high risk level by contrasting and analyzing the HAZOP reports. Secondly, based on the analysis result, bow-tie model containing coupling relationships of factors obtained from equipment and effects to other equipment could be established. Equipment failure rate and incident occurrence rate could be calculated to estimate the leakage likelihood. Thirdly, constructing consequence quantitative calculation models to calculate consequences of accident in bow-tie model. Fatalities, the influence range injuries, economic loss, environmental pollution, etc., can be estimated. The effect of the factors, including leakage source height, diameter of leakage whole, wind speed, on leakage incident consequence has been studied. Severity could be obtained and finally the risk rank can be calculated according to the risk matrix established according to the likelihood and severity.Residue hydrocracking unit has been taken as an example to express the method application. It turned out that applying the method can not only improve accuracy of risk analysis, but also specify the cause of the accident to a certain device, technological parameter, flange, safety valve, control loop etc., which has a certain degree of engineering application value in providing method and technique basis for equipment fault monitoring, early warning and ensure the safety of device for a long period of time.