Development Of PSA Oxygen Adsorbent And Optimization Of Process Performance For Low-pressure Environments In Plateau Regions

High-altitude and low-pressure environments influence the nitrogen-oxygen separation performance of oxygen adsorbents and oxygen production during pressure swing adsorption(PSA).Consequently,achieving the desired oxygen production flow rate and concentration of oxygen production equipment in plateau regions is challenging.Furthermore,the oxygen demand of people dwelling in high-altitude areas cannot be satisfied,negatively affecting their physical and mental health.To this end,the present study developed an oxygen adsorbent with high nitrogen-oxygen separation performance and optimized PSA oxygen production in high-altitude and low-pressure environments.This study focused on applying oxygen adsorbents in high-altitude and lowpressure environments.First,the high-altitude adaptability modification of LiLSX adsorbents was investigated.Based on the liquid-phase exchange method,metal-ion modification experiments were conducted on Li-LSX adsorbents.Five modified oxygen adsorbents were obtained:AgLi-LSX,CaLi-LSX,ZnLi-LSX,CuLi-LSX,and FeLi-LSX.Furthermore,this study analyzed the effects of effective adsorption sites,average specific surface area,average pore volume,and cumulative pore volume per unit material with micropores on the nitrogenoxygen separation performance of the five modified adsorbents.The results indicated that the primary and secondary factors affecting the nitrogen-oxygen adsorption separation performance of the adsorbents were the number of effective adsorption sites,cumulative pore volume per unit material with micropores,average specific surface area,and average pore volume.Modifying Li-LSX with a small amount of Ag+increased the number of effective adsorption sites and the average specific surface area and average pore volume of the adsorbent.Furthermore,the nitrogen-oxygen separation coefficient of the adsorbent increased under high-altitude and low-pressure conditions.An experimental dual-bed PSA oxygen production device,based on the improved Skarstrom two-bed cycle oxygen production method,was constructed.The influence of each process parameter on the device’s oxygen production performance was systematically investigated under different oxygen production flow rates and operating conditions.Accordingly,a strategy for adjusting the process parameters was established to improve the device’s oxygen production performance at different oxygen production flow rates over a wide range.When the ratio of the oxygen-production flow rate to oxygen-production adsorbent dosage(Qp)is less than 2.00 SLPM/kg,the influence of excessive oxygen adsorption(EOA)can be eliminated by increasing the purging flow rate and reducing the adsorption pressure,thereby enhancing oxygen production during the process.Furthermore,the energy consumption of the device can be reduced by reducing the feed flow rate.When Qp≥2.00 SLPM/kg,the breakthrough of nitrogen(N2 breakthrough)is weakened,and the oxygen-enriched product gas can be retained by reducing the purging flow rate and increasing the adsorption pressure,thereby enhancing oxygen recovery.Finally,the cost-effectiveness of oxygen production can be improved by suitably increasing the feed flow rate.Using a PSA oxygen production equipment designed for high altitudes,the effects of the process parameters on the oxygen production performance of the equipment at different altitudes(50,2810,3080,3550,4140,and 4540 m)were systematically investigated.In addition,the variations of the process parameters with altitude were analyzed.With increasing altitude,adsorption and equalization times increased,increasing the ratio PH/PL.In addition,the feed flow rate increased,weakening the adverse effects of the decrease in gas source capacity and increasing the oxygen concentration and oxygen productivity of the equipment.Moreover,the purging time and purging flow rate decreased,lowering the P/F and saving the enriched oxygen product gas.Consequently,the recovery increased while the energy consumption per unit of produced oxygen decreased.Additionally,the oxygen production efficiency curve of the equipment varied with altitude,similar to the curve of environmental pressure ratio,and it can be used to evaluate the oxygen production performance of the equipment at different altitudes.Finally,the applicability of the oxygen production system study at different altitudes on the highland site was investigated to optimize the energy efficiency of the system.The influence of oxygen production flow rate on the oxygen production performance in the low-pressure environment of the plateau was explored.Furthermore,strategies for optimizing and adjusting process parameters were developed to improve the performance of the oxygen production system in low-pressure environments.The adverse effects of EOA were weakened or eliminated by increasing P/F and decreasing PH/PL at low oxygen production flow rates.At high oxygen production flow rates,the adverse effects of N2 breakthrough were weakened by an increase in P/F and PH/PL,thereby improving the oxygen production performance of the system over a wide range of oxygenproduction flow rate variations in low-pressure environments.Moreover,the energy consumption of the oxygen production system was reduced,resulting in an optimal balance of the energy efficiency of the oxygen production system.This study provides a theoretical and technical framework for developing high-nitrogen oxygen adsorbents with desirable separation performance in highaltitude low-pressure environments.