The demand for high-purity oxygen in fields such as healthcare, industry, and environmental protection is continuously rising worldwide. In the scenario of large-scale continuous oxygen supply, Cryogenic Air Separation and VPSA (vacuum Pressure swing adsorption) have become the two most representative technical approaches.
This article will conduct a deep comparison of the two from five core dimensions, providing professional references for technology selection in different scenarios. As a provider of on-site oxygen generation equipment solutions, Fullcryo will also present the practical application of its technology in this article.
The core logic of the deep cryogenic air separation oxygen generation technology is to separate different gases in the air based on their boiling point differences. This process requires cooling the air to below -180 ℃, then liquefying it and sending it into the distillation column. After multiple evaporation and condensation fractionation processes, high-purity gases such as oxygen, nitrogen and argon are finally separated.
The specific process can be divided into four steps: air compression → impurity purification → cryogenic liquefaction → distillation separation. The entire system needs to maintain a strict cryogenic environment to ensure the stable progress of the fractionation process.
VPSA is an upgraded form of pressure swing adsorption (PSA) technology. The core technology takes advantage of the difference in adsorption capacity of solid adsorbents (such as molecular sieves) for oxygen and nitrogen. Under normal or low pressure conditions, the adsorbent preferentially adsorbs nitrogen, thereby obtaining high-concentration oxygen. Subsequently, the adsorbent is regenerated by vacuuming, completing the process of cyclic separation.
Compared with traditional PSA, VPSA adopts vacuum desorption. This upgrade has reduced energy consumption and increased gas production, making it more suitable for medium and large-scale continuous oxygen usage scenarios and becoming the mainstream choice for industrial oxygen-enrichment applications.
The on-site oxygen supply system for cryogenic air separation can stably produce oxygen with a purity of ≥99%, and in some scenarios, it can even achieve gas separation of higher purity. Apart from gaseous oxygen, its greatest advantage lies in the direct production of various products such as liquid oxygen, liquid nitrogen and liquid argon, which can meet diversified demands.
Fullcryo’s cryogenic air separation oxygen equipment mainly focuses on customized EPC projects, featuring high start-up capacity. Despite its relatively high power consumption, it can support the construction of large-scale industrial gas plants and meet the demands of large-scale gas production.
The purity of oxygen produced by VPSA technology is usually between 80% and 94%, and it can be adjusted according to demand. It is mainly supplied directly to the site in gaseous form. Although liquid oxygen can theoretically be obtained through compression liquefaction, it is not commonly seen in practical applications.
Fullcryo offers a wide range of VPSA oxygen generators with production capacities ranging from 200Nm³/h to 6500Nm³/h, which can precisely match the on-site gaseous oxygen demands of different scales.
Cryogenic air separation, with its advantages of high purity, high production capacity and multi-gas co-production, has become the preferred choice for heavy industrial scenarios. Typical applications include the following:
Steel smelting: Based on Fullcryo’s service project experience, most of the smelting processes in the steel industry, such as blast furnace aeration, converter oxygen blowing, and steel water decarburization, require continuous high-flow oxygen supply (≥5000Nm³/h). Large-scale cryogenic air separation oxygen plants can be stably supported.
Liquefied gas suppliers: To ensure a stable supply of gases, many suppliers need to continuously produce, store and transport gas products such as liquid oxygen, liquid nitrogen and liquid argon. The construction of a cryogenic air separation oxygen plant helps optimize the production capacity of gas suppliers.
Aerospace: As a high-tech industry, many rocket and airaircraft related technologies have extremely strict requirements for gas purity, relying on oxygen combustion and ultra-high-purity nitrogen packaging (purity ≥99.999%). Only cryogenic air separation technology can meet these requirements.
Petrochemicals and chemical industry: Processes such as oil refining cracking and hydrogen-oxygen combustion require stable co-production of multiple gases. The regional centralized gas supply in chemical industrial parks also favors its scale advantages.
The VPSA system, featuring low energy consumption and strong economy, is suitable for medium and large-scale on-site centralized oxygen supply scenarios. Its core application fields are as follows:
In the metallurgical industry, processes such as combustion in blast furnaces for ironmaking, oxygen-enriched desulfurization in converters, and oxygen injection for heating and combustion assistance in blast furnaces require a continuous supply of medium-purity oxygen.
Environmental protection and power: The desulfurization and denitrification reactors (SDS) and ozone oxidation reactors in thermal power plants, as well as the ozone oxygen supply systems in municipal sewage and waste incineration plants, are all compatible with the high-efficiency characteristics of VPSA on-site oxygen generation.
In the medical field, oxygen supply centers of urban regional medical alliances and large hospitals with a daily oxygen supply of over 1,500 Nm³ have an urgent need for the stable gas production and low-cost advantages of VPSA.
During the operation stage, the cryogenic air separation oxygen plant consumes a large amount of electricity for compression and refrigeration, but its unit gas energy consumption cost can demonstrate competitiveness under an extremely large production capacity scale. However, the system has extremely high requirements for stable operation. The distillation column needs to operate continuously and has poor adaptability to start-stop and load fluctuations.
In terms of maintenance, cryogenic oxygen plants are highly complex and require professional operation and maintenance teams. The costs of cold box insulation maintenance and core component inspection are high, and the cost of purchasing spare parts is also considerable.
The energy consumption of the VPSA on-site oxygen generation equipment is mainly concentrated in the fan, vacuum pump and control system. The overall energy consumption is significantly lower than that of the cryogenic oxygen plant, with only a slight increase in energy consumption when the purity is improved. The maintenance of the VPSA oxygen production equipment is relatively simple, mainly involving the replacement of molecular sieves and the inspection and repair of valves and vacuum pumps.
In addition, VPSA has a stronger adaptability to load fluctuations and can flexibly adjust output according to oxygen demand, further reducing ineffective energy consumption.
Has the required oxygen purity reached ≥99%? Or is 80% to 94% sufficient?
Is gaseous oxygen only needed, or must it be accompanied by liquid products or multi-gas co-production?
Is the hourly/daily oxygen supply demand medium to large (200-6500Nm³/h) or super large (≥5000Nm³/h)?
Are there any strict restrictions on the preliminary budget and construction period?
Is the operation mode 24/7 continuous and stable operation, or does it require frequent load adjustment?
Is the site space sufficient to support heavy civil engineering works?
cryogenic oxygen plants: those that require ultra-high purity oxygen, liquid products or multi-gas co-production, and have an extremely large production capacity scale, can accept a long construction period and high initial investment, and pursue long-term stable operation.
VPSA oxygen unit : Medium-purity gaseous oxygen is required, with a production capacity ranging from 200 to 6500Nm³/h. Cost control and rapid commissioning are emphasized, and there is a certain demand for load adjustment.
Fullcryo has been deeply engaged in the field of on-site oxygen production, providing customized EPC projects for cryogenic oxygen plants to support large-scale gas production in heavy industrial scenarios such as steel and petrochemicals. We also supply multiple models of VPSA oxygen generators to meet the efficient oxygen supply demands in fields such as metallurgy, environmental protection, and medical care. No matter what the scenario is, it can rely on its technological accumulation to obtain suitable solutions.
If you need to further clarify the technical selection or understand the details of the equipment, you can contact Fullcryo at any time for professional support.
