Fire risk and Countermeasures of atmospheric and v

2022-10-22
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The fire risk and Countermeasures of atmospheric and vacuum distillation unit in chemical production

atmospheric and vacuum distillation unit, because it is in a significant link in chemical production, the materials are flammable and explosive, and the working environment is closed high temperature and high pressure, which has a greater risk of fire and explosion. Therefore, it is necessary to strengthen the research on its fire risk and take reliable fire safety measures

I. process part

1 The atmospheric and vacuum distillation unit is mainly composed of electric desalting of crude oil, atmospheric and vacuum distillation, refining of straight run products, four injection corrosion prevention, etc. Generally, it mainly produces gasoline, kerosene, diesel, wax oil, vacuum residue and a small amount of light hydrocarbons, and most of its products are raw materials for secondary processing devices

2. Main equipment (3.5mt/d):

the decompression tower has a diameter of 6.4m, a height of 54m, a volume of about 1100m3, a design pressure of 0.005MPa, and a feeding temperature of 400 ℃. The tower body is made of composite steel plate with a wall thickness of 16-20mm

II. Fire risk analysis:

the fire risk of the device belongs to class A. Parts prone to catastrophic accidents: heating furnace, primary distillation tower, atmospheric tower, vacuum tower, fractionation tower

1. Materials and products

(1) raw oil and wax oil: low spontaneous combustion point (about 240 ℃)

(2) gasoline, liquid hydrocarbon, dry gas: low flash point, flammable and explosive

(32. Structural principle) hydrogen sulfide (H2S): liquid hydrocarbon and dry gas contain% H2S. H2S is colorless, with rotten egg odor at low concentration, but no odor at high concentration. Extremely flammable, self ignition point 2. The short chain of isooctyl acrylate is suspended at the top 60 ℃. Explosion limit; 4.0-46.0 (v%) highly toxic, with strong neurotoxicity and strong irritating toxicity to mucosa. Invasion route; Inhaled and absorbed through skin. Exposure to high concentration (1000mg/m3) can lead to electric shock death, and the toxicity grade is huge

(4) there is a small amount of CO in the flue gas of the heating furnace, which is a colorless and odorless gas. Inhalation will cause poisoning, manifested as headache, dizziness, nausea, tinnitus, dizziness and other symptoms

(5) medium pressure steam: 3.5Mpa, temperature 440 ℃, it is colorless after leakage, which is easy to cause personnel scalding and injury by filling hot water into mineral water bottles

2. Process

(1) atmospheric and vacuum distillation unit has the typical characteristics of high temperature and high pressure in petrochemical industry, and the operating temperature is as high as 396 ℃

(2) high temperature oil and gas (350 ℃), leakage and smoking at the sealing part of the equipment. The vacuum residue leaks, and a fire occurs due to the spontaneous combustion of oil products; Diesel, gasoline, rich gas and other parts leak, and the oil gas and air are easy to form mixed explosive gases. After the accident, it is easy to expand and spread, and the development speed is fast

(3) the medium is gasoline, liquefied gas and dry gas Department: when leakage occurs, a very thick gas smell can be smelled around. Liquid outflow can be seen in gasoline, and ice can be seen in liquefied gas, and the sound of air flow can be heard in dry gas. Except for serious leakage caused by equipment and pipeline explosion, the development speed is generally slow after the accident. When a serious accident occurs, due to the leakage of a large amount of gasoline, liquefied gas or dry gas, a large number of light hydrocarbons sink to the ground and rapidly diffuse, forming an area of explosive gas. After the accident, it develops rapidly and has great potential danger

(4) atmospheric and vacuum distillation is a reaction carried out under high temperature conditions. Improper control of the temperature of the feed heating furnace will cause and even more damage to the first furnace tube

(5) sour gas (H2S), sour water, dry gas and liquid hydrocarbon in the unit contain high concentration of H2S, which is easy to cause personnel poisoning

3. Equipment hazard

(1) due to the miscellaneous sources of coking raw materials, the sulfur content of raw materials is high; The increase of sulfur in raw materials accelerates the corrosion of high-temperature and high-pressure parts of the equipment. In particular, the heating furnace feed line, coke tower gas line, fractionator bottom extraction line, and some high-temperature heavy oil lines

(2) when the oil and gas temperature of the vacuum tower reaches more than 380 ℃, illegal operation, perforation of the vacuum furnace tube, equipment corrosion, etc. occur in production, so that a large amount of air is sucked into the vacuum tower, which may cause fire and even explosion accidents in the vacuum tower

(3) high temperature and high pressure may cause various brittle failures, resulting in leakage of hazard sources

(4) high temperature and high pressure equipment and flange seal leakage, resulting in leakage of hazard sources

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