Study On Leak Simulation Of Non-methane Hydrocarbons In Tank Aera And Distribution Of Photo Ionization Detector

Storage tanks are storage equipment used extensively in the petrochemical industry.Non-methane hydrocarbons(NMHC)emissions from storage tanks not only cause oil loss,but also pollute the environment and even endanger human health.At present,there are few studies on the leakage and diffusion of NMHC in the inner floating roof tank area,and many accidents are caused by the failure to effectively monitor NMHC.The study of NMHC leakage diffusion simulation and monitoring in the tank area can not only predict the diffusion path and influence range of pollutants,but also facilitate the effective monitoring of NMHC.Therefore,thesis conducts a leakage simulation for a petrochemical floating roof tank in Yunnan,studies the diffusion law of NMHC and its distribution in the tank area,and based on this,the design the control of the photo ionization detector(PID)of the tank area NMHC is carried out to achieve the effective monitoring of NMHC.The main work and conclusions are as follows:Through the simulation of the consequences of tank accidents in different leakage scenarios,the simulation results showed that after the hazardous chemical leakage accident reaches steady state,the hazard distance,evacuation distance were positively correlated with the size of the hole and atmospheric stability,negatively related to the height of the hole and the level of wind speed.Phast,Fluent and Aloha had their applicable scenarios and limitations in hazardous chemicals accidents.By comparing Phast,Fluent and classical diffusion formulas,the calculated and measured values of the large breathing leakage diffusion in the fixed top tank at the same condition,it was found that the error between the result of the classical diffusion formula and the measured value was the largest.The simulation results of Phast were more accurate within lm from the storage tank,however,when the distance from the tank is greater than lm,and the simulation results of Fluent and Phast were not much different.Compared to Fluent,Phast did not consider the effect of obstacles on NMHC distribution.Therefore,the simulation results of Fluent were used to distribute the PID,and the monitoring peak can be adjusted according to the diffusion law obtained from the Phast-based tank breathing leakage study.Phast was used to simulate the leakage of gasoline tanks.The simulation results showed that when the tank leakage reacheed steady state,the NMHC concentration distribution in the tank area was linearly related to the distance.The closer to the tank,the higher the NMHC concentration was.At the same wind speed,the NMHC concentration at the same distance from the downwind direction of the tank was positively correlated with atmospheric stability.At the same atmospheric stability,the NMHC concentration at the same distance from the tank was negatively correlated with the wind speed.Fluent was used to simulate the leakage of gasoline tanks.The simulation results showed that when the tank area was affected by the southwest wind or the northeast wind,under the condition of only one tank with large breathing leakage,the center position of the top of the tank should be monitored.Under the condition of small breathing leakage in the gasoline tank area,the NMHC concentration value at the center of the top of the tank,near the downwind direction of the last row of tanks and 26m of the wind direction under the last row of storage tanks should be monitored.When the tank area was affected by the south wind or the east wind,in the case of only one tank with large breathing leakage,the PID sensor should be installed near the downwind direction of the tank.In the case of small breathing leaks in the gasoline tank area,the NMHC concentration value at the center of the tank top of the No.5 tank and near the wind direction of the last row of tanks should be monitored.When the tank area was affected by the west wind or the north wind,in the case of only one tank with large breathing leakage,the PID sensor should be installed near the wind direction of the tank.Under the condition of small breathing leakage in the gasoline tank area,the center position of the tank top of No.2 tank and the concentration of NMHC near the wind direction of the tank farthest from the wind inlet should be monitored.NVhen the tank area was affected by the northwest wind or southeast wind,PID sensors should be installed at the first row of tanks under the wind direction of 12m and the seeond row of tanks at a wind direction of 10m.Under the eondition of small breathing leakage in the gasoline tank area,the concentration of NMHC at 10m of the wind direction under the last row of storage tanks should be monitored.