Industrial gases are essential raw materials for industries such as petroleum, steel, chemical, medical, food, metallurgy, and electronics, and they play an important role in my country's economy. Air separation units are very important unit operations for industrial gas production. NEWTEK Group optimizes and improves the processes of traditional air separation units by combining Six Sigma management methods and chemical process simulation, and provides OEM air separation units in response to the shortcomings of high unit energy consumption and insufficient output of traditional air separation Plant.
The process of cryogenic distillation air separation consists of the following four parts: air compression, expansion machine refrigeration; purification of impurities, moisture, etc. in the air; air cooling and liquefaction through heat exchangers; air distillation and separation in distillation towers; low-temperature product recovery of cold capacity. Different products are designed and produced, and the equipment and implementation methods used in each part are also different, forming different processes.
Cryogenic Distillation - OEM Air Separation Plant Process
1. Classification according to operating pressure
2. Classification by expanded gas
3. Classification by purification method
4. Classification by separation method
5. Classification by output size
1. Classification according to operating pressure
According to the classification of operating pressure, cryogenic distillation air separation can be divided into high-pressure process, medium-pressure process, and full low-pressure process. The high-pressure process usually has an operating pressure of 10~20MPa. No expander is required during operation. Refrigeration relies on throttling effect, which is simple and convenient, but only suitable for small oxygen or nitrogen devices; the operating pressure of the medium-pressure process is usually 1~5MPa, with large unit cooling loss, and expansion machine refrigeration and throttling refrigeration are required during operation; the operating pressure of the full low-pressure process is usually 0.5~0.6MPa. This process has low unit energy consumption and is the most widely used.
2. Classification by expanded gas
According to the classification of expanded gas, the cryogenic distillation air separation unit can be divided into the expanded air process and the expanded nitrogen process. In the expanded air process, the expanded air enters the upper tower, which will affect the distillation of the upper tower; in the expanded nitrogen process, the expanded nitrogen will reduce the reflux liquid of the upper tower, which will also affect the distillation of the upper tower. The expanded air process and the expanded nitrogen process have their own advantages and disadvantages.
3. Classification by purification method
According to the classification of purification method, the cryogenic distillation air separation unit can be divided into the freezing purification process and the molecular sieve adsorption purification process. In the freezing purification process, the air enters the heat exchanger after cooling, and impurities such as H2O and CO2 will freeze and precipitate in the channel of the heat exchanger. After a period of time, the channel is switched, and the frozen impurities are taken away by the refluxed dirty nitrogen gas. In this process, the heat exchanger channel switches frequently, the startup operation is relatively complicated, and the technical requirements are high. The operation cycle is about one year. After one year, the heat exchanger will be severely blocked and the whole plant must be heated and defrosted; in the molecular sieve adsorption purification process, the impurities in the air have been purified by the adsorber before entering the main heat exchanger. The molecular sieve adsorber switches between each other for a long period of time, which can greatly simplify the operation. The operation cycle exceeds two years and is increasingly widely used.
4. Classification by separation method
Cryogenic distillation air separation relies on the distillation process in the distillation tower. According to the separation method, cryogenic distillation air separation can be divided into single high product process (nitrogen or oxygen), double high product process (nitrogen and oxygen), argon product process (nitrogen, oxygen, argon) and full extraction process (nitrogen, oxygen, argon and other rare gases).
5. Classification by output size
Based on the output size, cryogenic distillation air separation units can be divided into small air separation units, medium air separation units and large air separation units. The output of small air separation units is less than 1000Nm3/h; the output of medium air separation units is between 1000 and 10000Nm3/h; the output of large air separation units is greater than 10000m3/h.
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