At present, there are various forms and types of air separation equipment produced in our country. There are devices for producing gas oxygen and nitrogen, and also devices for producing liquid oxygen and nitrogen. But in terms of basic process, there are mainly four kinds, which are high pressure, medium pressure, high and low pressure and full and low pressure process. The production scale of air separation plant in our country has been only 20 m from the early stage3/H (oxygen) oxygen generator, developed to now has a production of 20000 m3/h、30000 m3/H and 50000 m3/H (oxygen) capacity of large air separation plant.
Basic System
The air separation plant is a large complex system, which mainly consists of the following subsystems: power System, purification system, refrigeration system, heat exchange system, rectification system, product delivery system, liquid storage system and control system, etc.
Power System: mainly refers to raw material air compressor. The air separation equipment obtains oxygen, nitrogen and other products through low temperature separation, which is essentially completed through energy conversion. And the energy of the unit is mainly input by the raw material air compressor. Accordingly, most of the total energy consumption required by air separation is the energy consumption of raw material air compressor.
Purification system: it consists of air precooling system (air cooling system) and molecular sieve purification system (purification system. The air temperature of the compressed raw material is relatively high, and the air precooling system reduces the air temperature through contact heat exchange, and at the same time, it can wash the acid substances and other harmful impurities in it. The molecular sieve purification system further removes the moisture, carbon dioxide, acetylene, propylene, propylene, nitrous oxide and other substances harmful to the operation of the air separation plant.
Refrigeration system: the air separation plant is cooled through expansion, and the refrigeration of the whole air separation plant strictly follows the classic refrigeration cycle. However, the commonly mentioned air separation refrigeration equipment only refers to: expansion machine.
Heat exchange system: the heat balance of air separation plant is completed through refrigeration system and heat exchange system. With the development of technology, the current heat exchanger mainly uses aluminum plate warped heat exchanger.
Rectification system: the core of air separation equipment and the important equipment to realize low temperature separation. High and low pressure two-stage rectification is usually adopted. As long as it is composed of low pressure Tower, medium pressure Tower and condensing evaporator.
Product delivery system: the oxygen and nitrogen produced by the air separation plant need a certain pressure to meet the use of the follow-up system. As long as it is composed of different specifications of oxygen compressor and nitrogen compressor.
Liquid storage system: the air separation plant can produce certain liquid oxygen, liquid nitrogen and other products, and enter the liquid storage system for use when needed. As long as it is composed of different specifications of storage tank, low temperature liquid pump and carburetor.
Control System: large air separation plants all adopt computer distributed control system, which can realize automatic control.
From the perspective of technological process, the air separation plant can be divided into five basic systems:
Impurity purification system: It purifies mechanical impurities, moisture, carbon dioxide, acetylene and so on mixed in the air mainly through devices such as air filters and molecular sieve absorbers.
Air cooling and liquefaction system: it is mainly composed of air compressor, heat exchanger, expansion machine and air throttle, etc., which plays the role of deeply freezing air.
Air rectification system: the main components are distillation tower (upper and lower towers), condensing evaporator, supercooler, liquid air and liquid nitrogen throttle valve. It plays the role of separating various components in the air.
Heating blow-off system: use the method of heating blow-off to regenerate the purification system.
Instrument Control System: control the whole process through various instruments.
