Quantitative risk assessment of sour gas transmission pipelines using CFD

Sour gas is more dangerous than sweet gas because of its hydrogen sulfide contents, so it requires more safety considerations. The safety aspects of long pipelines for transportation of sour gas have been always of concern because of the potential populated area, high pressure and presence of toxic compounds of pipelines. In this study, the risk assessment studies have been done for sour gas transport pipeline using a combination of CFD method and dose-response model. Three different release cases include small, medium and large size hole were studied and two different angles were considered for gas jet outlet, horizontal and 45° angle from the horizon. The individual risk was determined for ten points on the ground surface in the vicinity of pipeline with 10 m gap distance. Probability and fatality diagrams were obtained in each case. Results show individual risk can be neglected in the case 45° angle from the horizon. The value of risk at 10 m distance from the pipeline was approximately 3.2 times more than the risk value at 100 m distance. As a case study, a real gas transmission pipeline is investigated in the adjacent area which is categorized in accordance to its assigned individual risk. The case study is a sour gas transmission pipeline that is placed in south of Iran. In this study, minimum individual risk of 8.27537 E−06 (yr−1) is determined at 100 m distance to pipeline, so it can be concluded that for this pipeline, safe distance is more than 100 m.