Study On Fire Extinguishing Technology Of Large Floating Roof Oil Tank With Fine Water Mist And Nitrogen

With the rapid development of economy and society,people's demand for energy is increasing.At present,China's oil consumption ranks second in the world,and the problem of oil reserve come out.The floating roof tank is favored by most enterprises because it is not easy to explode,burn and has lower evaporation loss than other oil tank.Considering the economic problem,the storage volume of floating roof tank also tends to be designed in a large scale that refers to an oil tank which has capacity more than 10×10~4m~3..Once the tank volume increase,corresponding fire control system need to be more strict.Because it will increase the potential dangers.Once it explores,it will cause immeasurable harm and loss to people's personal safety and social property.This paper aims to analyze the shortcomings and loopholes of the existing tank wall foam extinguishing system and come up with a new type of fire extinguishing system—water mist and nitrogen explosion extinguishing system.The system theory is to inlet a certain amount of nitrogen into the sealing ring of the floating roof tank,so that the concentration of oil and gas can be reduced and be lower than the limit concentration of explosion,which often uses 1%as the reference standard.If there is an accident in the sealing ring,the water mist spray nozzle can be opened in time to extinguish the fire.The author made a series of experiments on the effect of water mist extinguishing.Experiment indicates:when the pressure is between 0Mpa and 2.0Mpa,the water mist radius increases with the increase of pressure;when the pressure exceeds 2.0Mpa,the water mist radius changes little with pressure.The results show that the combined fire extinguishing effect is better when the pressure reaches 2.0Mpa.Study the effect of water mist on oil fire under different wind speed.The effect of different wind speed on the fire extinguishing effect was obtained.Water mist extinguishing effect is inversely proportional to wind speed.When the wind speed is at 0m/s~1.7m/s,the sprinkler head pressure is adjusted to 2.0Mpa,and the extinguishing effect is the best.When the wind speed is at 1.7m/s~3.8m/s,the sprinkler pressure is adjusted to 4.1Mpa,and the extinguishing effect was better.Using the Fluent software to simulate the nitrogen inerting process in the sealing ring,it concludes that the nitrogen inerting has a certain fireproof effect.Set up the oil tank model and its sealing ring model by pyrosim software,simulated fire inside the sealing ring and apply a fine mist spray to process the experiment.Compared from temperature field,oxygen concentration,flue gas rate and heat release rateb,it concludes that water mist has better control on the fire and has better effect on fire extinguishing and fire cooling.Finally,in combination with the actual and in accordance with the existing specifications,the nitrogen gas pipeline and the water mist pipeline are arranged on the floating roof tank,and some parameters are calculated.The new fire protection system designed is applied to the actual project.