Oxygen, an important industrial gas, is widely used in iron and steel manufacturing, non-ferrous metallurgy, chemical industry, furnace & kiln energy saving, environmental protection (wastewater treatment, waste burning, etc.), glass manufacturing, paper making, medical treatment and other industries. Vacuum pressure swing adsorption oxygen generation plant (abbreviated to VPSA oxygen plant) is to adsorb nitrogen, carbon dioxide, moisture and other impurities in the air selectively using special VPSA molecular sieve, after which oxygen is enriched and released. The molecular sieve is desorbed under a vacuum condition when it's saturated, thus generating enriched oxygen in cycles.

1. PSA/VPSA Oxygen Generation Processing Steps of PKU PIONEER

As shown above, the oxygen production system of PKU PIONEER mainly consists of Roots blower, water cooler, Roots vacuum pump, adsorption vessel, buffer tank, valve system, etc. Vacuum pressure swing adsorption (VPSA) oxygen system generally separates and enriches oxygen through the steps shown above.

In the VPSA oxygen generating (VPSA-O2) process, the blower allows the air to enter the adsorber of the VPSA O2 unit under pressure. Then adsorption of nitrogen, carbon dioxide, water vapor and other components in the air takes place in the adsorber, and oxygen streams through the adsorbent with a small amount of rare gases, thus realizing the separation of oxygen and nitrogen. The saturated adsorbent is vacuumized to desorbe the impurities , and regenerate the adsorbent. The whole oxygen production system is controlled by PLC (programmable logic controller) and DCS (data control system), and the program controlling valves are cyclically switched to ensure constant oxygen generation. In one cycle, each adsorber needs to go through five steps, i.e., adsorption, depressurization, desorption, purging and repressurization.

1.Adsorption

After removing the mechanical impurities through the filter, the air enters the adsorber through the Roots blower. The adsorbent bed selectively adsorbs N2, H2O, CO2 and hydrocarbons from the pressurized air when it goes through the adsorbent while O2 is enriched and discharged out of the adsorber through its outlet. Part of the oxygen produced by this step is sent to the buffer tank, and the other part is reserved for the next step to purge and repressurize the low-pressure adsorption tower.

2.Depressurization

After adsorption at a high pressure, the pressure falls to a lower level and a proportion of the adsorbed components will be desorbed. Along the outlet of the adsorber A, the enriched oxygen is fed into adsorber B which is in the repressurization step to boost its pressure.

3.Vacuum Desorption

In order to desorb the impurities as much as possible, the adsorber needs to be evacuated and depressurized, that is, a vacuum pump is applied to further evacuate the adsorption vessel to lower the partial pressure of the impurities for them to be desorbed, and then discharged out of the vessel through the pump to realize the adsorbent regeneration.

4.Purging

For more thorough desorption of impurities in the adsorption vessel, at the end of the vacuum desorption step, a small amount of product oxygen is introduced from another high-pressure adsorber to purge the adsorbent. At this time, the partial pressure of oxygen rises while impurities’ is further reduced, resulting in more complete regeneration of the adsorbent however, which is more conducive to the next cycle of adsorption.

5.Repressurization

Once the adsorbent is regenerated, the pressure in the vessel is relatively low. To quickly recover to the adsorption pressure, it is necessary to introduce enriched oxygen released from another adsorber in the pressure reducing step to lift the pressure. At the end of the repressurization step, pressure in the adsorption vessel reaches the level required by the adsorption and is ready for the next cycle.

2. Advantages & Features of PSA Oxygen Production Process of PKU PIONEER

As the leader of PSA gas separation technology in China, PKU PIONEER has been committed to R&D in this field for over 20 years. Combining advanced process design and reasonable & reliable supplementary devices with the independently developed high-efficiency lithium-based adsorbent PU-8 and special radial-flow distribution technology, we has ensured high energy efficiency and low consumption of the VPSA-O2 system, thus providing product oxygen at a lower cost.

★High Oxygen Adsorbent Performance

The new high-efficiency air separation molecular sieve-PU-8, developed and manufactured by PKU PIONEER independently, has a high nitrogen-oxygen separation coefficient (2-5 times that of traditional oxygen-generating molecular sieves) and nitrogen adsorption capacity. With superior dynamic performance, it enables our oxygen units to have less molecular sieve loading amount and longer service life (more than 20 projects kept running for over 10 years continuously).

★ Radial Adsorber Design

PKU PIONEER has developed the unique radial airflow distribution for adsorbent bed, which is propitious to better performance of the adsorbent. Meanwhile, it also helps to improve adsorbent efficiency by reducing the dead volume, thereby greatly lowering the power consumption. The PSA oxygen generation technology of PKU PIONEER has been in the top over the globe.

★ High Oxygen Yield

The oxygen yield of PKU PIONEER is over 20% higher than that of the conventional VPSA oxygen production systems. Under the premise of the same oxygen capacity, less amount of air to be treated and nitrogen to be desorbed reduce the load on the blower and vacuum pump.

★ Low Energy Consumption

Given the product oxygen purity is 100%, the power consumption is as low as ≤0.32kwh/Nm3, which is 10-20% lower than the domestic similar units. So substantial operating costs can be saved.

★ Highly Automated

The instrument system, controlled by a host computer, has a perfect safety monitoring and alarming system. The operating software, developed by PKU PIONEER, allows fully automatic program-controlled operation and unattended operation.

★ Professional Technical Services

PKU PIONEER provides customers with professional process design, package & delivery, on-site installation, free technical training and other services.

★ Environmentally Friendly & Pollution-Free

The exhaust gas discharged by the oxygen generating device is mostly polynitrogen air, which does not contain any harmful substances or cause environmental pollution.

So far, PKU PIONEER has provided oxygen plants for more than 300 customers worldwide, widely used in blast furnace oxygen-enriched combustion, electric furnace steelmaking, nonferrous metallurgy, glass furnace combustion, ozone wastewater treatment, pulp bleaching, hazardous waste treatment and other industries. With remarkable advantages of lower power consumption (10-30%), easy operation, swift start-up and shut-down (less than 30 minutes), small footprint, simple maintenance, low civil engineering & installation costs, high automation, high long-term operation reliability, etc., all the projects received unanimous recognition of the customers. We always upholds the brand connotation of "professionalism, integrity, high quality and efficiency" and strives for technological innovation, energy conservation and environmental protection to provide professional & sincere services and create maximum benefits for every client.