Refinery fire characteristics

One, burning fierce
After a fire in a refinery, the burning speed of the material is very fast. Often within a short period of time, the entire installation area and the entire workshop may become a sea of ​​fire and the combustion is very fierce. Most of the materials combusted by fires in the refinery are flammable gases, flammable flammable liquids, and are under high temperature and high pressure. If a dripping leak encounters a fire source, it will instantly form a large-scale fire and it is difficult to fire and rescue . For example, in a flammable flammable liquid fire, the spreading speed of the flame along the surface of the burning liquid can reach 0.5-2m/s. It can be seen that the spreading speed is very fast and the burning is extremely violent.
Second, explosive destructive
(I) Chemical Explosion of Combustible Gases
Due to the running, running, dripping, and leakage of the production equipment, combustible gas or flammable flammable liquids and other materials are leaked from the joints of pipelines, valves, towers, and cauldrons, and their combustible vapors and air form a mixed gas. When it reaches the explosion limit, a chemical explosion occurs when it encounters a fire source. The explosion power is very large. That is, the shock wave and high heat generated during the explosion will destroy the production equipment, causing the fire to quickly spread and expand, sometimes causing casualties.
★ Case 1: At 21:30 on June 27, 1997, in the Eastern Chemical Plant of Beijing Chemical Industry Group Co., Ltd. in Tongzhou District, southeast of Beijing, when filling light diesel oil, the wrong valve was opened, resulting in a spill of naphtha full of cans. In the event of an explosion caused by a fire, 9 people were killed and 39 were injured. The direct economic loss was 117 million yuan.
★ Case 2: On the afternoon of March 5th, 1998, the LPG LPG management office of Xi'an Gas Company had a local failure of the upper flange seal of the discharge valve at the storage capacity of 400 cubic meters at the bottom of the 11th storage tank, causing a large amount of LPG. Leakage reached the explosion limit in the irrigation area and caused a chemical explosion.
(b) Physical Explosion of Equipment There have been instances of physical explosions and fires in production facilities of oil refineries. The explosion of high-temperature and high-pressure equipment usually results from the volume expansion of flammable gas or liquid materials inside the device. If the operation is mistaken, the device is overheated and overpressured. In the event of a fire, the reaction device is roasted by high-temperature flames for a long time. The temperature inside the device rises and the pressure increases. When the internal pressure exceeds the compressive strength of the production device, a physical explosion occurs in the production device, which promotes the spread of the fire or causes a chemical explosion. The damage is very serious.
At 21:30 on June 27, 1997, the Eastern Chemical Plant of Beijing Chemical Industry Group Co., Ltd., located in Tongzhou District, southeast of Beijing, caused a chemical explosion fire due to an accidental operation, causing a physical explosion on the north side of the V09561B ethylene ball can and burning the tank. There were 17, 19,257 tons of storage materials, and part of the tank frame, meters, cables, bridges, and buildings. Nine people were killed and 39 were injured.
(III) Equipment Negative pressure explosion In the normal production operation of the oil refinery, the residual pressure in the vacuum tower is mostly 1 to 4 kPa. The flanges and the vent valves connected to the tower are damaged if not tight or are ignited by the fire grill. When an explosive gas is blown into the tower, it may explode, causing great difficulty and danger to the rescue work. When fighting a fire cooling production device, or taking measures such as venting, diversion, etc., attention should be paid to the pressure change inside the production device, and no negative pressure should be generated to trigger the explosion of the production device.
(4) The explosion caused by improper fire extinguishing measures In the process of fighting a fire in an oil refinery, when the production device is under ultra-high temperature, high pressure, low temperature, low pressure, or negative pressure, sudden cooling may cause the production device to burst due to temperature difference and cause explosion. If negative pressure occurs inside the production equipment when process measures such as diversion or venting are adopted, chemical explosion inside the production equipment may also occur due to “tempering”, which increases fire damage and personnel casualties.
Third, the reburning
When extinguishing, pay special attention to the repeatability of burning and explosion of materials. If the fire is extinguished, the flammable liquid overflows and the immediate recurrence of the flammable liquid is encountered. When the oil vapor and air are mixed to form an explosive gas, a strong explosion will occur in the event of an open flame or high temperature, which will cause the entire fire site to rekindle: After a fire is extinguished, if thermal cracking gas, liquefied petroleum gas, or hydrogen continues to leak and diffuse, it will instantly explode in the event of an open flame or high temperature waiting for a fire source to cause the entire fire site to reignite.
Fourth, the fire flow
In the event of a fire at a refinery, due to the presence of a large amount of flammable liquid material in the pipeline inside the production plant, once the container is destroyed, the flammable liquid material is ejected from the top to the bottom of the container and flows from the top to the bottom along the ground. The inflow into the ditch runs downstream, resulting in a situation in which the development of the fire is crisscrossed by vertical, horizontal, and open ditch and underdrain, which brings about an extremely complicated situation to the rescue work.
Fifth, the flame floating
When a fire occurs in a production plant of a refinery, due to the requirements of the production process, many links are operated at high temperature and high pressure, so that the gasified combustible gas is strongly ejected from the orifice or crack of the container under the action of high pressure. The torch-type floats in space, with flames of several meters or even more than ten meters, drifting higher and longer, and directly grilling production equipment and building components. Heat radiation also threatens the safety of firefighters.
★ Case 3: In June 2000, Daqing Oilfield Refinery, a thermal oil pump house, caused a large area of ​​rogue fire due to leakage of oil, due to the buoyancy of the flame. A fire broke out in the vacuum tower 50 meters away.
Six, explosive burst reentrant
When the refinery is in the process of production, for some reason, the combustible gas leaks out and spreads into the space, or the flammable flammable liquid flows and evaporates a large amount of flammable gas. If there is an open flame or a hot object, the ignition source is ignited or exploded. At that time, the flame will rapidly rekindle in the opposite direction. Especially when the fire is extinguished, if the source of combustible materials (gas, liquid) is not cut off, even if the fire is extinguished, there may be re-emergence and re-explosion. Combustible gas flow and liquid flow are reversed in the opposite direction. If this happens, people in the zone will be injured by shock waves, burning, and lack of oxygen.
Seven, multi-point fire source
The production facility of the refinery is exposed to flames and high-temperature roasting. Multiple cracks are prone to breakage. Combustible gas or flammable flammable liquids are combusted from the damaged parts of vessels (towers, kettles, furnaces, pipes, etc.) and burned to form multiple fire points. The source of the fire is high, low, distant, and relatively close. When fighting a fire, if there are multi-directional and multi-point fire sources on the fire, special attention must be paid to timing and the effect of fire suppression when extinguishing a fire. Otherwise, multiple ignition sources will have been extinguished, and only one point has not been extinguished, which will also lead to a full-scale explosion or re-ignition. Therefore, when studying the countermeasures for fire suppression in refineries, special attention should be paid to the characteristics of multiple sources of fire.
At 21:30 on June 27, 1997, in the early days of the fire at the Dongfang Chemical Plant, 10 vertical and 5 ball type gas cylinders in the entire irrigation area were violently burned due to the comminuted explosion of spherical tanks, and they were ejected due to explosive debris. The plant area forms several fire points centered on the irrigation area:
(1) 1 000 m3 pilot plant in an acrylic plant located 800 m west of the tank area.
(2) The 200-meter pipe gallery fire on the northwest side of the tank area;
(3) Several fire spots such as high-voltage lines and warehouses are located 400 meters to the south of the tank area.
Eight, fire three-dimensional
(a) The three-dimensional diffusion of combustible gas is lighter than that of air. Combustible gas flows from floor holes and ventilation ducts from the bottom up. The combustible gas that is heavier than air diffuses from top to bottom. When it encounters fire or high temperature, it can be fired. Form a three-dimensional fire.
(ii) Flammable flammable liquids Flows of flammable flammable liquids are usually diverted from up and down longitudinal flow or from platform to ground to lateral flow diffusion. Wherever flammable flammable liquid materials flow, the fire will rapidly develop. Wherever there is a lot of room for combustion, sometimes the point of fire is up to 100 meters. It is very difficult to fight this kind of three-dimensional fire.
★ Case 4: In November 1999, at Karamay Oilfield Refinery in Xinjiang, the booster valve of the vacuum tower was broken by a strong wind, and the high-temperature oil flowed out from the booster valve. When the oil was combusted from the air, it flowed down from the tower. Top-down flow of fire, and caused ground fire, a typical three-dimensional fire.
Nine, fire hazard
In the event of a fire at a refinery, the hazards are particularly severe. The main hazards are explosion, scorching, poisoning, and corrosion. The fire will instantly expand, and the production equipment and building components will be destroyed and broken, deformed or collapsed, causing severe damage. Economic losses caused even heavy casualties and political influence.
X. Constraints on natural conditions
The production plant area (workshop) of the refinery is mostly an open-air type building, that is, the production equipment of the entire process is exposed to the "light day day". Once a fire occurs, the direction of the flame, the direction of the combustion products, and the direction of heat radiation, etc. The impact of wind and wind (or the difference in elevation between terrains) is particularly significant when there is a fire in the case of windy weather. The impact is even more pronounced. It even affects the parking position of fire fighting vehicles in the fire fighting plan, and even affects the fire extinguishing agent. The direction, distance, and effectiveness of fire fighting and the combat operations and personal safety of firefighters.
★ Case 5: At 9:55 on August 12, 1989, No. 5 oil tank of the first phase of the Huangdao oil depot of the China National Petroleum Corporation’s Shengli Oil Company was caught in a fire due to a lightning strike. During the fire extinguishing process, sudden changes in wind direction occurred. Caused the sudden explosion of the No. 4 crude oil tank, and exploded the top half-meter-thick cement layer at the top of the tank to high altitude. The flames formed a massive fireball and mushroomed into the sky. Thirteen officers and men of the Qingdao Detachment heroically sacrificed and 66 officers and soldiers were injured. Eight fire engines and one commander were withdrawn from the fire.
XI. Difficulties in combat operations
When fighting an oil refinery fire, the fire characteristics determine the fire fighting action of the refinery is very arduous and dangerous. First, the number of access roads for ascending is low and narrow; second, there are many fire sources and they are high from the ground; third, intense heat radiation and toxic fumes seriously affect the fighting actions of the combatants; and fourth, the noise on the fire is particularly strong, directing It is very difficult; Fifth, during the process of extinguishing, explosions may occur at any time, threatening the safety of the combatants.
XII. Exhaustion of fire fighting and rescue equipment
When a fire occurs during a production operation of a refinery, a large number of fire extinguishing and fire fighting equipment are needed, and the amount of equipment used in the fire extinguishing process is several times or more than ten times the amount of the loss when fighting a fire.
1. The scale of the fire is large, resulting in high consumption of fire extinguishing agents;
2. The pressure of the water pump is high, and the consumption of water and other equipment is large;
3. Oil pollution, equipment consumption.
★ Case 6: At 3:20 am on March 30, 1986, the raw material tank farm of Linyuan Refinery, China Petroleum & Chemical Corporation, was cracked due to the rupture of the No. 21 wax tank, and a large amount of high-temperature oil was leaked. Flowing around, the burning area reached 20,400 square meters. After receiving the alarm, the Daqing Fire Control Detachment dispatched ten public security fire brigades and five enterprise full-time fire brigades, altogether forty-four fire engines and 38 aircraft. In the production of large-scale water tankers, 259 combatants participated in the war, sharing 89.5 tons of foam and 9866 tons of water. The actual water consumption exceeds 10,000 tons. The direct economic loss was 1,133,451 yuan, and the indirect economic loss was 2,246,950 yuan.