Pub Date : 2024-04-09DOI: 10.1007/s10450-024-00443-0
Gabriel Jesus de Almeida Henrique, Antônio Eurico Belo Torres, Diana Cristina Silva de Azevedo, Rafael Barbosa Rios, Moisés Bastos-Neto
This study aimed to evaluate the production of high purity oxygen (90–95%) through experiments in a PSA/VSA unit and develop a mathematical model to describe the dynamic behavior of the process. Different operational parameters and the dead volume were investigated for their impact on process performance. The experiments used a laboratory-scale unit filled with beads of a commercial LiX zeolite to obtain breakthrough and PSA/VSA data for model validation. Equilibrium isotherms of pure oxygen and nitrogen were measured 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. Synthetic air (grade 5.0 purity, excluding argon) with a composition of 20% (± 0.5%) O2 and 80% (± 0.5%) N2 was used in the PSA/VSA experiments. A novel approach was developed using the mathematical model designed to simulate PSA/VSA cycles to account for the dead volume effects commonly found in units of this type. The model was implemented and solved using gPROMS® software. The simulation data matched well with the experimental data, accurately representing histories of concentration, pressure, temperature, and purity variations during the process. The validated model revealed optimal operating conditions for a VSA unit: 7.5 s adsorption time, 1.5 bar adsorption pressure, 0.1 bar desorption pressure, and a flow rate of 1 SLPM, producing a purity of approximately 94% and a recovery of about 20%. Increasing the adsorption duration negatively affected the oxygen purity but positively influenced process recovery and productivity. Adding an equalization stage improved process recovery by 18.9% for PSA and 14.5% for VSA. Additionally, increased dead volume in the column had adverse effects on purity, productivity, and recovery for both PSA and VSA units.
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Pub Date : 2024-04-08DOI: 10.1007/s10450-024-00456-9
Bruna Thaisa Martins Ferreira, Vitor Anthony Duarte, Leonardo Hadlich de Oliveira, Washington Luiz Félix Santos, Pedro Augusto Arroyo
H2S and CO2 are considered two main impurities of natural gas and biogas. These impurities must be removed in order to achieve economic and environmental restrictions. Adsorption is a promising technology studied to achieve this goal. Among alternative adsorbents studied to capture H2S and CO2, porous aromatic frameworks (PAFs) had shown potential application because of suitable selectivity and remarkable adsorption capacity. However, H2S and CO2 adsorption/desorption data on PAF-30 are still scarce in literature. Thus, in this work, H2S (up to 2.5 bar) and CO2 and CH4 (up to 50 bar) adsorption/desorption isotherms on PAF-30 were determined at 293, 303 and 313 K for the first time in literature. PAF-30 was synthesized and characterized by XRD, FTIR, 13C-NMR, Ar and CO2 physisorption, SEM, TEM, TGA and DSC analyzes. Then, adsorption isotherms were determined gravimetrically. Experimental data were modelled with Jensen-Seaton equation. The results indicated that PAF-30 presents adsorption capacities in the order H2S > CO2 > CH4. Adsorption/desorption branches do not match for systems studied, due to a hysteresis effect. Adsorption capacity decreases with temperature, indicating that physisorption is the main phenomenon observed. Experimental data were represented by Jensen-Seaton model. Thermodynamic analysis showed that all systems are exothermic and spontaneous. Working capacities obtained indicate that temperature reduces the performance for gas purification and that H2S systems are affected by hysteresis loop. Moreover, cyclic adsorption results show that PAF-30 has potential to be applied and further studied in PSA simulations for H2S and CO2 capture under high-pressure conditions.