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The purified compressed air enters the tower and exchanges heat with the reflux gas in the main heat exchanger. It is gradually cooled into saturated air with a small amount of liquefaction, and then enters the lower tower for distillation. Distillation is the process of obtaining pure oxygen and nitrogen through multiple partial evaporation and partial condensation in a fractionator using different boiling points of oxygen and nitrogen. The function of the lower fractionation tower is to produce liquid air and liquid nitrogen. The main condenser evaporator is used to evaporate liquid oxygen and condense gas nitrogen at different pressures under low pressure, while the upper fractionation tower is used to obtain product oxygen and nitrogen.

The equipment adopts the principle of deep freezing separation, and the process of molecular sieve adsorption at room temperature and reflux expansion refrigeration for oxygen and nitrogen production is selected. After passing through an air filter to remove dust and other mechanical impurities, the raw air enters a screw air compressor and is pressurized to 1.2MPa. The compressed air passes through an air cooler and enters an air precooling unit to cool to 5-8 ℃. The water is removed in a water separator and then enters a molecular sieve purifier to remove moisture, CO2, acetylene, and other hydrocarbons. The purifier consists of two adsorbers; One working, the other regenerating (automatic switching of the system). The regenerated gas is the dirty nitrogen discharged from the cold box, which is pressurized by an expansion mechanism driven fan and heated by an electric heater. The switching cycle of the purifier is 8 hours.

The temperature of the air exiting the purifier increases due to the adsorption heat of the molecular sieve. The purified air enters the cold box and exchanges heat with the returning dirty nitrogen, nitrogen, and oxygen in the main heat exchanger. It is cooled to the liquefaction temperature, with a small amount of air being liquefied. Then it enters the bottom of the lower tower, and the air rises one by one through the sieve tray, exchanging heat and mass with the reflux liquid nitrogen from the condenser at the top of the tower. As a result, liquid air is obtained at the bottom of the tower, and high-purity nitrogen is obtained at the top of the tower.

The liquid air is cooled and throttled by the subcooler before entering the middle of the upper tower as the reflux liquid for the distillation tower. The nitrogen at the top of the tower is completely condensed into liquid nitrogen, except for some being extracted as products. Most of it is used as reflux liquid for distillation, and a small amount is extracted as liquid products, which are discharged from the cold box through a liquid storage tank. After the product nitrogen is heated to room temperature through the main heat exchanger and air, it is output to the user as a product.

In the condensation evaporator, liquid oxygen is evaporated into oxygen, which is mostly used as the rising steam of the upper tower. After being rectified with the liquid air falling from the top of the tower through block by block sieve trays, the top becomes dirty nitrogen gas and the bottom is pure oxygen. The product oxygen is extracted from the bottom of the condenser evaporator, pressurized by a liquid oxygen pump, and then enters the oxygen heat exchanger to exchange heat with the air. After reheating to room temperature, it goes to the filling device to fill the bottle. If a small amount of liquid oxygen product is needed, it can be directly extracted from the bottom of the condenser evaporator.

Equipment use: Oxygen is a colorless, odorless, odorless, and non-toxic gas at room temperature and pressure. The content of oxygen in the air is 20.95% by volume, with a density of 1.429kg/m3 under standard conditions, which is slightly heavier than air. The standard boiling point of oxygen is 90.2k. Liquid oxygen is a sky blue, easily flowing liquid. Mixing oxygen with a certain proportion of combustible gases (such as acetylene, hydrogen, etc.) can form explosive mixtures; Oxygen also has a strong combustion supporting effect. The higher the concentration of oxygen, the more intense the combustion becomes. If pressurized oxygen and liquid oxygen are encountered, the situation becomes even more severe. Liquid oxygen cools to 54.8k and turns into snowy solid oxygen. Oxygen has relatively active chemical properties and can be used as a combustion gas. For example, in the metallurgical industry, it is commonly used for steelmaking, ironmaking, combustion, welding, cutting, and medical purposes, and liquid oxygen is used as rocket fuel for launch.

The product can be directly extracted from the bottom of the condensing evaporator.

The equipment is designed based on the principles of long-term stable and reliable operation, energy conservation, and simple and convenient operation and maintenance. The following advantages.

*High purity and very stable oxygen

*This process is a new development and design, and our company is able to apply this technology maturely.

*Good safety - the external compression process uses oxygen to compress in the form of gas at room temperature, while the internal compression process uses liquid oxygen to compress in the form of liquid at low temperature. The internal compression process has higher safety performance

*The startup time is short, and users can stop midway according to their actual needs. After heating, the time from starting the expander to producing qualified products is within 12 hours.