Leakage Risk Assessment Method For The Sulfur Recovery Unit And Its Application

Sulfur recovery unit is one of the most important units in an oil refining enterprise. HAZOP analysis result showed that the leakage of H2S and liquid ammonia causing fire and toxic accident are the two mainly potential severity risk in the sulfur recovery unit. According to the risk matrix in SINOPEC HAZOP analysis standard can acquire that the highest risk level of the leakage of H2S is E1 grade and the leakage of ammonia is C1 grade. However, the qualitative analysis of HAZOP is mainly based on the experience of experts leading to excess subjective factors for the analysis results.In order to better assess and determine the risk of fire, explosion and poisoning caused by leakage in the sulfur recovery unit and assist enterprises to take effective measures to avoid economic losses, casualties, and reduce costs, This paper puts forward a leakage risk assessment method for the sulfur recovery unit. The relationship among personnel, process, equipment, chemicals, instrumentation & control and other multiple factors and influence mechanism in complex process could be identified according to the process of sulfur recovery unit and report of hazard and operability analysis. Bow-tie models of the leakage risk in important nodes in the sulfur recovery unit could be established respectively. Based on probability calculation of multi-factor model, the probability of potential risk of fire and toxic accident caused by H2S and liquid ammonia leakage in sulfur recovery unit under the complex condition could be determined. H2S diffusion concentration, ammonia burning upper and lower limits near leak source could be calculated by PHAST software based on Gaussian diffusion model. The combustion area of the unit and the risk severity could be determined.The calculation result could be used to validate and quantify leakage risk of sulfur recovery unit. A sulfur recovery unit auxiliary system for emergency rescue based on risk analysis could be established after applying risk assessment on the unit which will provide technical support for operating personnel of the unit to find, analysis, process and solve the problem at the first time.This research results in this article will provide technical method basis for the detection and monitoring important risk area of sulfur recovery unit and the concentration distribution of flammable and toxic gas of its internal surrounding equipment. It will contribute to take effective measures to prevent leakage of sulfur recovery unit. The method has a broad application prospect.