Pressure Swing Adsorption (PSA) is a gas separation technology. In 1960, C. W. SKARSTROM of the United States first obtained a patent for PSA molecular sieve oxygen generation. Subsequently, countries such as the UK, Germany, and Japan conducted extensive experimental research. In 1970, UCC (Union Carbide Corporation) of the United States first achieved industrialization and has long held a leading position in the development and application of PSA technology. In competition with traditional separation methods, the PSA method has been continuously improved and perfected, thus achieving rapid development.
The PSA nitrogen generation system uses air as raw material and utilizes a highly efficient and selective solid adsorbent (carbon molecular sieve) to selectively adsorb nitrogen and oxygen, separating them from the air. The separation effect of carbon molecular sieve on nitrogen and oxygen is mainly based on the different diffusion rates of these two gas molecules within the carbon molecular sieve. Smaller diameter gas molecules (oxygen) diffuse faster and enter the solid phase of the molecular sieve in greater quantities. In this way, nitrogen enrichment can be obtained in the gas phase. After approximately 2 minutes, the adsorption of oxygen by the molecular sieve reaches equilibrium. Based on the characteristic that the adsorption capacity of carbon molecular sieve varies under different pressures, the pressure is reduced to desorb oxygen molecules from the carbon molecular sieve; this process is called regeneration. Pressure swing adsorption (PSA) typically uses two towers in parallel, alternating between pressurized adsorption and depressurized regeneration to obtain a continuous nitrogen supply.
A complete nitrogen production system includes: air compressor (set) — compressed air purification components — air storage tank — PSA nitrogen generator — nitrogen buffer tank — nitrogen storage tank (low pressure) — nitrogen booster system — nitrogen storage tank (high pressure).
Selecting a nitrogen generator involves many issues. First, thorough market research is necessary to determine the specific model and specifications (nitrogen production capacity, nitrogen purity, outlet pressure, and dew point, etc.). A comprehensive comparative analysis of the performance and characteristics of nitrogen generators should be conducted, and the correct selection should be made based on the local working environment.
When inspecting the nitrogen generator, the operator should pay attention to the following aspects:
The air compressor (group) provides the required compressed air for the PSA pressure swing adsorption nitrogen generator. Its flow rate, pressure and other requirements are determined according to the gas consumption of the PSA pressure swing adsorption nitrogen generator. The efficiency (consumption) of the PSA pressure swing adsorption unit will be mainly determined by the molecular sieve performance, process flow and adsorber structure. The air compressor should meet the following requirements:
In practical use, daily checks of the air compressor include: operating temperature (≤ 105℃), working pressure (0.8～1.0MPa), water pressure (0.3～0.6MPa), etc. Monthly checks include oil level, whether there is leakage at pipeline connections, etc. Quarterly maintenance includes cleaning the intake filter, cleaning the air filter element, checking the connectors, etc. Annual maintenance is performed by INGERSOLL RAND professional engineers in accordance with the Ingersoll RAND product "Maintenance Manual". In daily use, the maintenance recommendations and priorities in the manual should be followed:
When the equipment has a general fault, the person in charge of the equipment should troubleshoot it according to the troubleshooting guidance in the manual. If the fault cannot be troubleshooted, please contact INGESOLL RAND professional engineers for assistance. The main factor affecting the performance of an air compressor is temperature, and the main factors influencing temperature (under constant pressure and flow rate) include season, water temperature, and water quality. This equipment's cooling water pipes are designed to use tap water with inlet and outlet diameters of 40mm, with a water consumption of approximately 9t/h directly discharged. Without water recycling, this would be a significant waste. Recycling the cooling water for secondary use would also require substantial financial investment (the local water hardness is between 380 and 410 mg/L). Summer is the most challenging time for air compressors, and it also serves as a test of the suitability of the initial choice of cooler type. In PSA (Pressure Swing Adsorption) nitrogen generators, the air compressor incurs the highest investment in equipment maintenance and upkeep. Thorough market research and planning are essential before choosing this type of nitrogen generation method.
include: ensuring the condensate and wastewater discharged from the refrigerated dryer are unobstructed; and checking the coolant pressure (0.3～0.6 MPa) and compressed air pressure (＜1.0MPa) are normal. Maintenance includes regularly blowing the radiator (especially in spring and summer to prevent heat dissipation issues), cleaning the drain outlet, and regularly (generally every 12 months) replacing the three filters (models: 3-stage filter XF3-44, 7-stage filter XF7-44, 9-stage filter XF9-44). The selection, installation method, installation location, and season of the refrigerated dryer all have a certain impact on its oil and water removal performance.
The activity of the activated carbon and alumina in the adsorber is directly related to the air quality of the compressor and the oil and water removal performance of the refrigerated dryer. Generally, depending on the equipment's usage, the activated carbon and alumina should be replaced every 3-5 years.
The carbon molecular sieve is the core of the pressure swing adsorption nitrogen generator. Its performance indicators include: hardness, nitrogen production (Nm3/T-h), recovery rate (N2/Air)%, and packing density. During use, prevent overheating from affecting the adsorption effect and strong airflow impact from causing molecular sieve pulverization.
Return the instrument to the manufacturer annually for testing and calibration of the sensor probes according to the instruction manual. Check and investigate any abnormalities found during routine maintenance.
as product storage equipment, should undergo monthly self-inspections and annual self-inspections. Outsourced flaw detection by the Technical Supervision Bureau should be conducted every 3 years. After 6 years, when the design service life is reached, continued use or scrapping should be determined based on the inspection results.
Maintenance and upkeep are essential for ensuring the normal operation of the PSA nitrogen generator. As a public utility equipment, the stable operation of the PSA nitrogen generator is a prerequisite and guarantee for the unit's industrial experiments. Timely maintenance and upkeep of each unit can prevent malfunctions, extend equipment life, and improve energy efficiency.
