The petrochemical plant is characterized by continuity and complexity of technological process. The arrangement of the plant is highly dense, with crisscross pipes, dense and dazzling. In spite of the intricacies of petrochemical installations, I consider towers, furnaces, tanks, tanks, pumps, and pipelines as the basic elements of the petrochemical installations. Due to the different production factors such as production materials and product process requirements, the process parameters of petrochemical plant are also very different. The following devices are mainly analyzed here:
(1) Evaporation and distillation units
Evaporation and distillation unit is an important unit of petrochemical production, application is very extensive, evaporation is in the liquid surface gasification phenomenon, is the most simple process in petrochemical production, general pressure is not big, the temperature is not high, the relative risk is lesser, distillation by every components of the boiling point of the liquid mixture to separate the liquid, the mixture separation process for the operation of the pure components. Distillation is divided into batch distillation and continuous distillation according to the operation method; According to pressure points can be divided into atmospheric distillation (general distillation), vacuum distillation (vacuum distillation), pressure distillation (high pressure distillation), special distillation four kinds. The process is raw materials → heating → evaporation → fractionation → condensation → different products
The main equipment used for distillation is called a distillation column. According to the tray structure (internal structure), the distillation column can be divided into packed column, sieve column, floating valve column, cangue tower, tongue tower, sentinel tower and pipe tower and other forms of tower. For the sake of economic benefit and safety setting, atmospheric distillation and vacuum distillation are combined and carried on continuously in petroleum industry.
The working temperature of atmospheric tower is generally around 370℃. For example, crude oil with working pressure of 0.2MPa → heat exchanger and heating furnace to 360 ~ 370℃→ Atmospheric tower → gasoline, kerosene and diesel are separated.
Vacuum tower, temperature 420℃, vacuum height 700 ~ 720mmHg (distillation unit)
Main fire hazards of distillation unit: first, it is caused by fire explosion by heating too much or heating with open flame. Secondly, corrosion of tower wall and tray makes flammable liquid or steam escape. 3. Accidents caused by welding of inlet and outlet material pipelines, damage of sealing device, leakage of burning liquid or steam; Fourth, the material condenses and clogs the pipeline, which increases the pressure inside the tower and causes the explosion. Five is the vacuum distillation due to the internal pressure is lower than the normal pressure, such as equipment seal is not good easy to suck and air and there is the risk of fire or explosion.
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