Avaliação da Separação do Oxigênio a partir do Ar por Pressure/Swing Adsorption

Abstract

The coronavirus (COVID-19), which caused a pandemic scenario, has increased the demand for high purity oxygen throughout the world health system. This gas can be obtained from air by adsorption-based separation processes. For small-scale production, Pressure Swing Adsorption (PSA) or Vacuum Swing Adsorption (VSA) units are normally used, due to their shorter cycle time, simplified operation and possibility of operation in ambient temperature. This work aimed to implement a mathematical model to simulate PSA/VSA units to obtain high purity O2 (90 – 95%) and to study the influence of different operational parameters on the process performance. To obtain breakthrough experimental data, PSA/VSA operation and model validation, a laboratory-scale PSA/VSA unit packed with commercial zeolite (Z10-05-03) provided by ZEOCHEM© was used. Equilibrium isotherms of pure O2 and N2 were obtained at 288, 298 and 313 K for the pressure range of 0 to 3 bar. Single and multicomponent breakthrough curves were obtained at 298 K. A mathematical-phenomenological model combining mass, energy and momentum balances was implemented and solved using gPROMS software. The simulated data of breakthrough and variation of pressure, temperature and purity along the PSA/VSA processes showed a good agreement with the data obtained experimentally. From the validated model, different operational conditions were evaluated for the VSA process, with the following conditions being implemented in the unit: adsorption time of 7.5 s; adsorption and desorption pressure of 1.5 and 0.1 bar, respectively; flow rate of 1 Standard Liters per Minute (SLPM), achieving a purity of approximately 94%. Furthermore, through the simulations, it was possible to observe that increasing the duration of the adsorption step has a negative influence on the O2 purity obtained. However, it has a positive effect on process recovery and productivity. The incorporation of the equalization stage into the operating cycle represented gains of 18.9 and 14.5% in process recovery for PSA and VSA operations, respectively. The increase in dead volume at the unit had a negative influence on purity, productivity and recovery, and this effect was observed in both operations.