Application Fields of Pressure Swing Adsorption (PSA)
At present, pressure swing adsorption gas separation technology is widely used in the recovery and extraction of H2, CO2, CO, and vinyl chloride rectification tail gas.
1. Recovery & Purification of H2.
Normally, during the application of this technology, the pressure should be controlled in the range of 0.8~2.5MPa, which is used to adsorb the gas in the product.
At first, gas adsorption needs to be completed using two beds, one of which is used as a gas regeneration bed, and the other bed is used as a gas adsorption bed. After a period of adsorption, they alternate with each other. As the pressure rises, the gas in the dead space gradually disappears.
At present, this method is applied to solve the problem of multi-bed pressure swing adsorption, and the product energy and components are obtained from it after pressure release and pressure equalization treatment.
In practical application, by increasing the number of pressure equalization applications, the product recovery rate is improved, and the H2 recovery rate ranges from 75% to 80%. In order to meet the demand for H2 extraction, it is necessary to adjust the gas recovery process according to the number of product production and processing beds.
From the perspective of program control, my country has successfully developed H2 extraction programs under different parameter specifications, which support the switching of gas extraction with different parameter specifications. The H2 recovery rate exceeds 90%, and the purity is as high as 99.9%.
2. Recovery & Production of CO2.
Among many gases, CO2 is a kind of gas with strong adsorption capacity, and there are many residues in the adsorption bed, which is difficult to remove. Therefore, it is necessary to recover and extract CO2.
The emergence of pressure swing adsorption technology has opened up a new path for CO2 extraction research, extracting CO2 from synthesis gas. In general, the dry detachment method and the wet detachment method are used to extract gas. The former has lower energy consumption and takes a long time to develop, while the latter has a longer development time and the technology is mature.
In order to solve the problem of CO2 extraction, the United States took the lead in using gas separation technology to separate CO2 from synthesis gas. The entire gas separation process starts with the conversion of hydrocarbons, and after conversion treatment, different fractions of gas are obtained, and then CO2 is extracted from it to make its purity reach 99.4%. On this basis, increase the purity of H2, and when it reaches 99.9%, mix nitrogen and hydrogen at a ratio of 1:3, and adopt compression treatment to obtain ammonia.
The CO2 recovery rate of this process is 94%, and the H2 recovery rate is 95%, marking the progress of decarbonization technology research.
3. Recovery & Purification of CO.
CO is one of the products of many industrial developments in our country, and it pollutes the air environment seriously. CO recovery is a necessary part of industrial production.
In order to deal with this problem, the idea of gas conversion is often used to remove CO gas. This treatment method is too costly. Considering the problem of cost control, the method of purifying gas is used instead of gas conversion.
At present, the most widely used gas extraction technology is pressure swing adsorption technology, which is divided into two-stage method and one-stage method. Among them, the one-stage method has high gas extraction purity and low energy consumption, which has become one of the main treatment processes for CO purification. The application principle of the one-stage method: CO adsorbent is selected as the gas purification treatment material to directly separate the gas, which simplifies the operation steps and facilitates the rapid separation of the gas.
In practical applications, copper salts are added to the surface of adsorbents such as alumina and molecular sieves, and CO is extracted from the mixed gas under complexation. At present, this gas treatment process is gradually mature, and it is widely used in CO gas separation.
4. Recovery of Vinyl Chloride.
The rectification tail gas is recovered by controlling the pressure to extract the vinyl chloride rectification tail gas. As the pressure increases, the tail gas recovery rate increases.
Pressure swing adsorption technology will become the core technology of gas separation, expand the application coverage, make breakthroughs in process flow, and simplify the recovery and extraction processes of different types of gases according to different gas properties.
In addition, there will also be a breakthrough in the adsorption performance, selecting substances with strong adsorption properties to replace the original adsorption substances, so as to increase the molecular screening ability and improve the gas purity. Judging from the current development situation, it is possible for the gas purity to reach 99.999% in future technology applications.
Therefore, the application and development of pressure swing adsorption technology can help more fields to deal with gas separation problems, and has a good application prospect.
