In addition to oxygen and nitrogen, there are also small amounts of gases such as water vapor, carbon dioxide, acetylene, and other hydrocarbons in the air, as well as small amounts of solid impurities such as dust.
The water vapor content in each cubic meter of air is about 4-40g/m3 (depending on the region and climate), the carbon dioxide content is about 0.6-0.9g/m3, the acetylene content is about 0.01-0.1cm3/m3 (the content can reach 0.05-1cm3/m3 near acetylene stations and chemical plants), the content of solid impurities such as dust is generally 0.005-0.15g/m3, and can reach as high as 0.6-0.9g/m3 near metallurgical plants. Although the content of these impurities in each cubic meter of air is not high, due to the large air separation equipment processing tens of thousands or even hundreds of thousands of cubic meters of air per hour, the total amount brought into the air separation equipment per hour is still considerable. Taking a 60000 m3/h oxygen concentrator as an example, the amount of water brought into the air compressor with the air is about 11 tons per hour. After passing through the air cooler and nitrogen water precooler, a large part of the water will precipitate. Nevertheless, there is still 2000kg of water brought into the air separation equipment every hour. The amount of dust inhaled with the air every day can reach 50-100kg, or even more.
These impurities are harmful to the air separation equipment. As the air cools, the frozen water and carbon dioxide deposit in the low-temperature heat exchanger, turbine expander, or distillation tower, which will block channels, pipelines, and valves; The accumulation of acetylene in liquid oxygen poses a risk of explosion; Dust can wear out running machinery. In order to ensure the long-term safe and reliable operation of the air separation equipment, specialized purification equipment must be installed to remove these impurities.
