Oxygen Liquid Plant

The basic principle of air separation is to liquefy air by cryogenic distillation, and then separate it according to the different boiling points of each component.

The two-stage distillation tower can obtain pure nitrogen and pure oxygen at the top and bottom of the upper tower at the same time; liquid oxygen and liquid nitrogen can also be drawn from the main condenser and the evaporation side respectively.

The air separation in the tower is divided into two stages: the air is pre-separated in the lower tower to obtain liquid nitrogen and enrich liquid oxygen; the oxygen-enriched liquid air is sent to the upper tower for distillation to obtain pure oxygen and pure nitrogen.

The upper tower is divided into two sections: the upper part is the oxygen distillation zone with liquid air feed as the boundary, and the rising gas is fractionated to recover the oxygen component and purify the nitrogen; the lower part is the nitrogen distillation zone, which separates the liquid nitrogen component and improves the purity of liquid oxygen.

The entire distillation process is carried out in an extremely low temperature environment, and high-purity separation is gradually achieved by using the difference in boiling points of each component. The upper and lower tower stages are designed in series to effectively improve energy utilization efficiency. Advanced distillation control technology ensures stable product quality.

• Air compression: The air is compressed to 0.5~0.7MPa by an air compressor.
• Precooling: The air is cooled to 5℃~10℃ in the precooler and the water is separated.
• Purification: Residual water, carbon dioxide and hydrocarbons are removed by the molecular sieve purifier.
• Air expansion: The air expands in the expander to achieve self-cooling and provide the required refrigeration capacity for the system.
• Heat exchange: The air exchanges heat with the reflux from oxygen, nitrogen and impurity nitrogen in the main heat exchanger of the distillation tower, and is cooled close to the liquefaction temperature, while heating these refluxes to room temperature.
• Throttling cooling: Nitrogen cools the throttled liquid air and liquid nitrogen before entering the bottom cooler.
• Distillation: The air is distilled and separated in the distillation tower, and the product nitrogen is obtained from the top of the upper tower, and the pure oxygen is obtained from the bottom of the upper tower.
• Product processing: The separated oxygen and nitrogen are further purified, compressed and stored, and output as the final product.

In air separation units, liquid oxygen pipelines are mainly distributed from the outlet of the cold box to the liquid oxygen tank and the liquid oxygen loading pump. Usually there are a. straight pipes arranged on the pipe gallery; b. pipes and pipe fittings connected to the pipe mouths of equipment and pumps; c. liquid oxygen manifolds and other main pipeline forms.

Combining the above different pipe section forms, we considered a. outer jacket insulation (CR); b. vacuum jacket pipe insulation (CV) two insulation options for liquid oxygen pipeline insulation selection