Cryogenic air separation and PSA (pressure swing adsorption) are two mainstream air separation technologies, which are suitable for gas supply with different scales and demands.
In principle, the cryogenic air separation utilizes the difference in boiling point of oxygen and nitrogen, and requires rectification and separation after compression, purification and deep freezing liquefaction. The air needs to be cooled to below - 180 ℃. The system is complex and the startup is slow, which takes several hours to 24 hours; PSA, based on the adsorption selectivity of molecular sieve to oxygen and nitrogen, is subject to pressure adsorption and pressure reduction desorption cycle separation under normal temperature, without deep cooling. It only takes a few minutes to half an hour for startup and shutdown.
In terms of performance, cryogenic air separation has obvious advantages, oxygen purity can reach more than 99.5%, high purity nitrogen and argon can be co-produced, single unit capacity can reach thousands of Nm ³/h, suitable for large-scale continuous production; The upper limit of PSA purity is low, most oxygen is 90% - 95%, argon is difficult to produce, and the capacity is concentrated in hundreds of Nm ³/h, which is suitable for small and medium-sized intermittent demand.
For economical efficiency and operation&maintenance, the initial investment of cryogenic air separation is high, the infrastructure construction period is long, and professional team maintenance is required, but the energy consumption for large-scale operation is low; PSA is skid-mounted and modularized, with low investment, fast installation, simple operation and maintenance and unattended operation. Small and medium-sized energy efficiency is better.
Cryogenic air separation is applicable to high purity requirements of large industry, and PSA is applicable to medium and small scale flexible energy consumption scenarios. The model selection shall be comprehensively judged based on purity, capacity and budget.
