Background:
Mercaptans are the highly flammable and malodorous natural gas odorants in the urban gas distribution network and are used to detect gas leakage. Exposure to high concentrations of this substance has deleterious impacts on human health.
Objectives:
The purpose of this study was to determine the hazard distance and to examine the consequences of fire and the distribution of Mercaptans spills in its containing station in a specific provincial gas company.
Methods:
Modeling scenarios were defined based on the valid existing events and related consequences with respect to the gas pressure reducing station. To determine the safe distances of hazardous areas, applicable data and criteria were used in accordance with total GS SF 253. These criteria include the amount of flammable radiation in the event of Mercaptan fire, the amount of LFL (low flammable level) Mercaptan distribution, and the distribution rate of various concentrations of Mercaptan (0.5, 10 and 100 ppm). Subsequently, modeling was performed using input parameters and via Process hazard analysis software Tools (PHAS) software. Finally, the consequence evaluation of scenario occurrence and hazard distance were identified through the modeling results.
Results:
The distribution and pool fire caused by Mercaptan spill from containers were considered as the worst scenario at the respective gas station. Results from the modeling indicated a large distance distribution (3997 m) from the concentration of 0.5 ppm of Mercaptan (concentration of respiratory tract burning threshold) in case of a spill. Furthermore, according to the results of modeling in the event of a fire, the maximum radiation distance is 4.7 kW/m² in the 10/D climate class, which extends up to 28 meters.
Conclusions:
Given the distribution of Mercaptan at long distances and the proximity of gas pressure reduction stations of the respective gas company to the residential and medical facilities, it is strongly recommended that the location of these barrels be moved away from residential areas.
Keywords:Consequence Analysis,Hazard Distance,Mercaptan Spill,Gas Pressure Reducing Station,PHAST