Study On Heat Radiation Critical Distance Of Full Surface Fire

The storage tanks in the tank farm have the characteristics of large volume,concentrated distribution,inflammable and explosive,etc.Leakage or explosion accident will bring huge losses to personal and property safety.The strong heat radiation effect of a burning tank will cause harm to ordinary personnel and firefighters.At the same time,it is very easy to ignite adjacent tanks and cause large-area tank farm fires.This study of the thermal response and failure mode of adjacent tanks is great significance for crowd evacuation,fire rescue and tank spacing settings under the fire conditions of a full-surface pool.Therefore,the main research results are as follows:(1)Introduce the combustion mechanism and flame model of the tank full surface fire,simulate and analyze the change of the flame inclination of the full surface fire,introduce the thermal response mechanism and model of adjacent tanks,and use the PyroSim software to simulate the thermal response of adjacent tanks in the environment of the tank full surface fire.The results show that regardless of the tank spacing and wind speed,the temperature of the tank top of the adjacent tank is significantly higher than the temperature of the tank wall,and the temperature at the junction of the tank top and the tank wall on the side of the burning tank is the highest.The connection between the tank top and the tank wall is the weakest link of the adjacent tank in the fire environment of the tank pool.(2)Based on the research results of flame thermal radiation damage and the thermal radiation flux damage criterion,the critical thermal radiation flux value of ordinary personnel and firefighters in the tank area was clarified,the critical radiation damage distance model of tank full surface fire radiation was constructed,and the atmospheric stability was simulated and analyzed with the help of PHAST software.Air humidity,wind speed and tank diameter affect the radiation damage distance of ordinary personnel and firefighters.The results show that air humidity,wind speed and tank equivalent diameter will all have a significant impact on the radiation damage distance,but atmospheric stability has an impact on the tank pool.The fire radiation damage distance has basically no effect,so the leeward distance of ordinary personnel under the most unfavorable conditions is regarded as the critical thermal radiation damage distance,and the crosswind distance of firefighters'thermal radiation damage is taken as the thermal radiation critical damage distance.(3)Analyze the failure form and mechanism of adjacent tanks,and build an tank full surface fire radiation critical failure distance model on this basis,study the changes in the radiation failure distance of adjacent tanks under different factors.The results show that the 10000m3 fixed-roof gasoline storage tank will explosion when the fire separation distance is less than or equal to the fire separation distance specified in "Code for Design of Petroleum Depots"(GB 50074-2014).As the distance between tanks is between 0.6D and 0.74D,long-term thermal radiation will cause adjacent tanks failure.It can be seen that the failure mode of adjacent tanks is determined by the nature of the storage medium in the tank,the thermodynamic properties of the tank material,and the tank spacing.The leeward distance under adverse conditions is regarded as the critical failure distance.(4)Taking a warehouse chemical enterprise in Qingdao as an example,the thermal radiation damage distance and failure distance of gasoline tanks with capacities of 13000m3,6500m3 and 1500m3 in the tank area are analyzed.The actual fire separation distances of the three tanks are in line with the standard distance(0.4D),but the simulated distance exceeds the standard distance(0.4D),and the ratios of the critical failure distance to the equivalent diameter are 0.76D,0.82D and 0.97D.The results show that adjacent tanks will be in a failure state under the most unfavorable conditions.The ratio of the failure distance to the diameter of the tank increases as the diameter of the tank decreases.Therefore,the setting of the tank spacing should refer to the most unfavorable gas phase conditions and the nature of the storage medium to determine the safe spacing.At the same time,emergency spraying should be installed in the tanks roof and the use of thermal insulation materials to reduce the impact of thermal radiation on the tank.