Effect Of PSA Oxygen Production Process Adjustment On Oxygen Production Effect Under Plateau Environment

Abstract:

Based on the improved cyclic PSA oxygen production process, a PSA oxygen production experimental device with adjustable process parameters was established. The effects of adsorption time, pressure equalization time, cleaning time and product gas flow rate on oxygen production performance in plateau areas were experimentally studied and theoretically analyzed. The results show that appropriately extending the adsorption time is conducive to increasing the adsorption pressure and improving the product gas performance, but too long adsorption time will cause the molecular sieve bed to penetrate, resulting in a sharp drop in the oxygen content (volume fraction) of the product gas; prolonging the pressure equalization time to a certain extent increases the adsorption pressure, thereby improving the product gas performance; the oxygen production effect is better under low cleaning time, and too long cleaning time will not further improve the purity of the product gas, but will lead to a large amount of high-purity gas waste; high product gas flow rate helps to eliminate the accumulation of high-purity product gas at the top of the adsorption tower and prevent oxygen from reflux to the mass transfer area. The research results will provide theoretical guidance for the optimization of PSA oxygen production effect in high-altitude areas and its practical application operation.

Optimization ideas for PSA oxygen production process in plateau areas

With the increase of altitude, atmospheric pressure decreases, and the exhaust volume of the compressor also decreases accordingly. At this time, the adsorption time is extended to increase the working pressure in the adsorption tower, improve the efficiency of the oxygen-producing molecular sieve, and obtain a larger nitrogen adsorption amount, which can achieve the effect of increasing the product oxygen content and oxygen production. The higher the altitude, the lower the corresponding pressure in the adsorption tower at the end of the adsorption process, and the lower the initial pressure obtained by the adsorption tower in the pressure equalization step after decompression and desorption. By appropriately extending the pressure equalization time, more pressure-equalizing gas can enter the adsorption tower, increase the initial adsorption pressure, and the corresponding oxygen molecular sieve nitrogen adsorption amount will increase accordingly, and the product oxygen content index will also increase. It should be noted that the pressure equalization time cannot be extended indefinitely. If it is too long, nitrogen will escape from the saturated oxygen molecular sieve and enter the desorption-completed adsorption tower. With the increase of altitude, the lower the desorption ambient pressure, the higher the desorption degree of the adsorption tower, and the demand for cleaning gas will decrease at this time. The cleaning volume should be gradually reduced as the altitude increases. The reduced cleaning volume is discharged as product gas, which is beneficial to increase the oxygen production and oxygen content. The corresponding maximum pressure of the adsorption tower will increase with the reduction of the cleaning volume, which is beneficial to the improvement of the product oxygen content and the oxygen production efficiency of the molecular sieve. Under the operating conditions of low product gas flow, the amount of oxygen accumulated on the top of the bed can be released by increasing the cleaning gas flow, which can slow down the adverse effects of oxygen backmixing; the adsorption pressure can be reduced by reducing the pressure equalization gas flow, which can slow down the accumulation of oxygen in the bed; the gas supply device with lower energy consumption can be replaced to appropriately reduce the intake flow and reduce production costs. Under the operating conditions of high product gas flow, the regeneration effect of the bed can be improved by increasing the cleaning gas flow.

Conclusion

NEWTEK's R&D team studied the influence of different process parameters (adsorption time, pressure equalization time, cleaning time and product gas flow) of oxygen production on the oxygen production effect under plateau environment, and summarized the optimization and adjustment methods of the oxygen production system, which can provide important references for the optimization direction and adjustment strategy of plateau oxygen production process, and the following main conclusions were drawn.
(1) With the change of altitude, there is an optimal adsorption time parameter. If the adsorption time is too short, the oxygen production efficiency of the molecular sieve will decrease. If the adsorption time is too long, the adsorption tower will be penetrated by nitrogen.
(2) If the pressure equalization time is too short, the initial pressure of the adsorption tower will be reduced, affecting the final adsorption amount of nitrogen by the molecular sieve. If the pressure equalization time is too long, ammonia in the mass transfer saturation zone of the molecular sieve adsorption layer will be desorbed and enter the adsorption tower that has just been desorbed, resulting in a decrease in oxygen production content.
(3) At the same altitude, the product oxygen content first increases and then decreases with the cleaning time. There is an optimal cleaning time. The higher the altitude, the lower the desorption pressure, the higher the desorption degree of the oxygen-producing molecular sieve, and the shorter the required optimal cleaning time.
(4) The optimal product gas oxygen flow rate decreases with increasing altitude. At the same altitude, when the product oxygen flow rate is low, the high-content oxygen accumulated at the top of the tower cannot be discharged in time, resulting in a high oxygen partial pressure in the upper mass transfer zone of the adsorption tower, which inhibits the adsorption of nitrogen by the oxygen-producing molecular sieve; when the product oxygen flow rate is too large, ammonia will penetrate the adsorption bed, causing the product oxygen content to drop sharply.