Fire prevention of the hottest liquid hydrocarbon

2022-10-03
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Fire prevention in liquid hydrocarbon tank farm

liquid hydrocarbons, in addition to liquefied petroleum gas, also include liquefied ethane, ethylene, propane, butadiene, natural gas, etc. in order to facilitate storage and transportation, these substances must be reduced in temperature under normal pressure or increased in pressure under normal temperature to become liquid. Under normal temperature and pressure, its explosion limit is less than 10%. It is a flammable gas, which can form an explosive mixture with air. In case of heat source and open fire, it has the risk of ignition and explosion. It is a class a fire hazardous substance

I. fire risk analysis

the tank farm has always been the focus of fire and explosion prevention in petrochemical enterprises, and the liquid hydrocarbon spherical tank farm is the top priority of fire prevention. If the management is not in place and the existing hidden dangers of accidents are not eliminated in time, fire and explosion accidents may occur, endangering production and human life safety, and causing huge losses to the enterprise. The factors that cause the fire and explosion of liquid hydrocarbon storage tanks include static electricity, lightning strike, misoperation, equipment failure, illegal hot work, leakage, external factors (power failure, water, gas, steam), etc., specifically:

1. Flammable and explosive gases, such as liquid fossil oil and gas, and the selection and assembly of suitable fixtures and clamping blocks. When small hole injection occurs, high-level static electricity will be generated due to the fast flow rate, which has been proved by practice, The electrostatic potential generated by liquefied petroleum gas during high-speed injection is as high as 9000v, especially when there are other particulate substances in the gas, its electrostatic risk is greater. When the charged body is close to the uncharged or low electrostatic potential object, as long as the potential difference reaches more than 300V, electrostatic discharge will occur and sparks will be generated. When the spark energy exceeds 0.3mJ, it is enough to ignite LPG within the limit of explosion concentration, causing combustion and explosion. 199 [transmission system] adopts precision reducer transmission. On February 26, 2008, the liquefied petroleum gas tank area of the storage and transportation branch of Jiangxi Jiujiang Petrochemical Complex was emptied and deflagration, which was caused by the high-speed injection of a large amount of liquefied petroleum gas at the end plate of 805.2 feed pipe, the accumulation of static electricity, and the discharge of sparks, which ignited the mixture of liquefied petroleum gas and air

2 ﹐ if the lightning protection device is struck by lightning due to the neglect of management, resulting in the reduction of lightning protection effect and loss of function, it will cause power failure in the distribution room, all electrical equipment will stop running, the combustible gas alarm facilities are out of control, and the fire electric pump cannot be started. In case of a fire in the storage tank, if the electrical equipment is not repaired in time, it cannot meet the requirements of fire water consumption and pressure, because the water supply of fire sprinkler cooling system and fire water monitor is generally supplied by industrial water

3. If the equipment fails, such as the refrigerator in the butadiene tank farm fails and stops running, the temperature in the butadiene tank will rise, resulting in butadiene polymerization. If the compressor in the low-temperature tank farm fails, the temperature in the ethylene tank will rise, and the pressure at the bottom of the tank will rise, resulting in overpressure of the spherical tank, which is easy to cause deformation and ductile fracture of the spherical tank

4. Fire caused by misoperation of liquid hydrocarbon spherical tanks. We have the world's best businessmen and the world's most popular university disasters. The most typical is the "88.10.22" Xiaoliangshan liquefied petroleum gas vicious deflagration accident, which killed 26 people and burned 15 people. The cause of the accident was that the operator opened the downstream valve of the dehydration package without closing the upstream valve of the spherical tank dehydration package when opening the valve dehydration operation of a LPG spherical tank. Under pressure, the water and LPG were discharged together, and the liquefied petroleum gas diffused outward and accumulated, causing deflagration when encountering the fire source

5. The accidents caused by the leakage of liquefied hydrocarbon storage tank are the most frequent in liquefied hydrocarbon tank farm, mainly including: (1) the gasket of tank valve is damaged and cracks appear, causing leakage; (2) The liquid level gauge and pressure gauge are damaged; (3) Pipeline rupture; (4) The tank weld is broken; (5) Compressor damage and other reasons. It can be seen from the Xi'an big bang accident on March 5th, 1998 that the cause of the accident was that the bottom valve of a 400m3 spherical tank in the liquefied petroleum gas Management Office of Xi'an gas company was worn and leaked, and the uncontrollable leakage caused the explosion of two 400m3 spherical tanks. The fire lasted 37 hours, 33 people were injured and 11 people died. Since liquid hydrocarbon spherical tanks are more dangerous than ordinary oil tanks, the operating conditions are harsh, and overheating, overpressure, out of control liquid level and material leakage are not allowed. Otherwise, due to its special nature, materials will leak from the valve. Once the leakage is difficult to control, a vicious fire like the "98.3.5" LPG explosion in Xi'an will occur, as well as the tightening of preferential policies for traditional fuel vehicles and the relaxation of new energy vehicle policies

II. Preventive countermeasures

liquefied hydrocarbon itself is relatively dangerous. Coupled with the centralized layout of multiple storage tanks, it is difficult to put out the fire and explosion once it is on fire, which will cause serious consequences. There are countless fire accidents caused by this reason. We should learn a lesson from them and prevent them from burning

1. Plane layout of spherical tank farm

(1) liquefied hydrocarbon spherical tanks should be arranged in the open air with good ventilation and away from open flames or sparks. At the same time, it should avoid minefields, seismic zones and areas vulnerable to floods. The fire separation between spherical tank areas should not be less than the provisions of Table 1:

Table 1 fire separation between spherical tanks

note: (1) d is the diameter of the larger tank in two adjacent tanks, M. (2) When the above ground horizontal tanks are arranged in rows, the fire separation between rows shall not be less than half the length of the longest horizontal tank, and shall not be less than 6m

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