Effect Of Adsorption Pressure Research Articles

Application of Response Surface Methodology (RSM) For Optimization of Hydrogen Sulphide Adsorption Using Coconut Shell Activated Carbon Xerogel: Effect of Adsorption Pressure and Hydrogen Sulphide Flowrate

Application of Response Surface Methodology (RSM) For Optimization of Hydrogen Sulphide Adsorption Using Coconut Shell Activated Carbon Xerogel: Effect of Adsorption Pressure and Hydrogen Sulphide Flowrate

Simulation of integrated novel PSA/EHP/C process for high-pressure hydrogen recovery from Coke Oven Gas

This paper introduces a novel Coke Oven Gas (COG) hydrogen purification/compression system based on the technologies of Pressure Swing Adsorption (PSA) and Electrochemical Hydrogen Purification and Compression (EHP/C). As the EHP/C tolerates O2, N2 and CH4 impurities, PSA can be utilized solely for CO and CO2 removal (other COG impurities were not considered in this work). A relaxation of PSA hydrogen purity could significantly enhance its recovery rate. In this study, the suitability of traditional hydrogen PSA as part of the hybrid PSA/EHP/C approach was investigated. Aspen Adsorption and Matlab were used to model the PSA and EHP/C systems, respectively. The effect of adsorption pressure, purge-to-feed-ratio (P/F-ratio) and adsorption time within cycle on PSA performance is reported. This study found that breakthrough of non-detrimental components is typically accompanied with poisonous CO. Hence, the CO removal with traditional H2-PSA resulted into high purity product. In a two-bed PSA, 36.3% of hydrogen was recovered at 99.9988% purity and 0.18 ppm CO. Subsequently, as a result, the EHP/C purification capability was merely utilized, but polished this hydrogen to >99.999% purity. Simultaneously, hydrogen was isothermally compressed to 20 MPa, consuming a marginal 2.42 kWh/kg. Compared to mechanical compression, this is 31.6% more energy efficient. Recovering hydrogen from by-product COG was found to save 0.5 kg CO2/kg H2 compared to hydrogen produced from natural gas. Conventional hydrogen PSA, utilizing 70% Activated Carbon and 30% Molecular Sieve 5A, was found not to be effective to target the removal of CO specifically. To increase synergy between PSA and EHP/C, the PSA requires adequate design and operation using appropriate adsorbents and cycle steps to target elimination of CO. An increased EHP/C catalyst tolerance for CO also contributes to higher flexibility.

Modelling and simulation of two-bed PSA process for separating H2 from methane steam reforming

Abstract Methane steam reforming is the main hydrogen production method in the industry. The product of methane steam reforming contains H2, CH4, CO and CO2 and is then purified by pressure swing adsorption (PSA) technology. In this study, a layered two-bed PSA process was designed theoretically to purify H2 from methane steam reforming off gas. The effects of adsorption pressure, adsorption time and purge-to-feed ratio (P/F ratio) on process performance were investigated to design a PSA process with more than 99.95% purity and 80% recovery. Since the feed composition of the PSA process changes with the upstream process, the effect of the feed composition on the process performance was discussed as well. The result showed that the increase of CH4 concentration, which was the weakest adsorbate, would have a negative impact on product purity.

Artificial neural network based optimization for hydrogen purification performance of pressure swing adsorption

A pressure swing adsorption (PSA) cycle model is implemented on Aspen Adsorption platform and is applied for simulating the PSA procedures of ternary-component gas mixture with molar fraction of H2/CO2/CO = 0.68/0.27/0.05 on Cu-BTC adsorbent bed. The simulation results of breakthrough curves and PSA cycle performance fit well with the experimental data from literature. The effects of adsorption pressure, product flow rate and adsorption time on the PSA system performance are further studied. Increasing adsorption pressure increases hydrogen purity and decreases hydrogen recovery, while prolonging adsorption time and reducing product flow rate raise hydrogen recovery and lower hydrogen purity. Then an artificial neural network (ANN) model is built for predicting PSA system performance and further optimizing the operation parameters of the PSA cycle. The performance data obtained from the Aspen model is used to train ANN model. The trained ANN model has good capability to predict the hydrogen purification performance of PSA cycle with reasonable accuracy and considerable speed. Based on the ANN model, an optimization is realized for finding optimal parameters of PSA cycle. This research shows that it is feasible to find optimal operation parameters of PSA cycle by the optimization algorithm based on the ANN model which was trained on the data produced from Aspen model.

Effect of bed void volume on pressure vacuum swing adsorption for air separation

The effects of a poorly packed bed on the pressure vacuum swing adsorption (PVSA) process were in- vestigated experimentally and theoretically by a five-step two-bed PVSA system. At first, the adsorption dynamics of a zeolite LiX bed for air separation (78 mol% N2, 21 mol% O2 and 1 mol% Ar) was studied at various adsorption pressures and flow rates. In breakthrough results, the effect of adsorption pressure on variations in bed temperature was greater than that of the feed flow rate. A combined roll-up of Ar and O2 by N2 propagation was observed and the roll-up plateau reached about 4 mol%. The fluid dynamic behavior of the poorly packed bed was simulated at each step in the PVSA process. The pressure and velocity profiles in the non-isobaric steps were clearly different from those of a normally packed bed. The two-bed PVSA process using one poorly packed bed with additional 1% void volume in feed end of bed could produce a purity of 92.3 mol% O2 from air, which was almost 1% purity lower than the PVSA with normal two beds. Even small asymmetry between beds, due to poor bed packing, could greatly reduce the product purity in the PVSA process.

Hydrogen recovery from Tehran refinery off-gas using pressure swing adsorption, gas absorption and membrane separation technologies: Simulation and economic evaluation

Hydrogen recovery from Tehran refinery off-gas was studied using simulation of PSA (pressure swing adsorption), gas absorption processes and modeling as well as simulation of polymeric membrane process. Simulation of PSA process resulted in a product with purity of 0.994 and recovery of 0.789. In this process, mole fraction profiles of all components along the adsorption bed were investigated. Furthermore, the effect of adsorption pressure on hydrogen recovery and purity was examined. By simulation of one-stage membrane process using co-current model, a hydrogen purity of 0.983 and recovery of 0.95 were obtained for stage cut of 0.7. Also, flow rates and mole fractions were investigated both in permeate and retentate. Then, effects of pressure ratio and membrane area on product purity and recovery were studied. In the simulation of the gas absorption process, gasoline was used as a solvent and product with hydrogen purity of 0.95 and recovery of 0.942 was obtained. Also, the effects of solvent flow rate, absorption temperature, and pressure on product purity and recovery were studied. Finally, these three processes were compared economically. The results showed that the PSA process with total cost of US$ 1.29 per 1 kg recovered H2 is more economical than the other two processes (feed flow rate of 115.99 kmol/h with H2 purity of 72.4 mol%).

Impact of Process Parameters on Oxygen-Bearing Low Concentration Coal Mine Methane Enrichment by Proportion Pressure Swing Adsorption

Conventional PSA methods with a single adsorbent can result in an explosive CH4 concentration of 5 to 15%, making low concentration coal mine methane (LCCMM) or risky in terms of safety at a concentration of 30%. Proportion Pressure Swing Adsorption (PPSA) is a new and safer enrichment method suggested for LCCMM enrichment that uses a mixture of active carbon (AC) and carbon molecular sieves (CMS) as adsorbents. The effect of adsorption Pressure, adsorption time and bed length on the PPSA process were investigated to verify the feasibility of this method. The experiment results show that the methane concentration in desorption gas and the oxygen concentration in exhaust gas increased and decreased, respectively, with an increase in adsorption pressure or bed length. And the methane concentration in desorption gas is increased with the adsorption time expanding, but the recovery of methane is reduced. So the methane concentration in desorption gas can be increased to more than 30% and the oxygen concentration in exhaust gas be decrease to less than 12% by increasing the adsorption pressure or lengthening the bed.

Air Separation by a Small-Scale Two-Bed Medical O2 Pressure Swing Adsorption

A small-scale two-bed six-step pressure swing adsorption (PSA) process using zeolite 13X was performed to provide oxygen-enriched air in the medical system. The binary mixture N2/O2 (79/21 vol %) was used for PSA experiments. Cyclic behaviors of the PSA process were investigated from unsteady- to steady-state conditions. Also, effects of various operating parameters on the PSA performance such as the P/F ratio, adsorption pressure, feed flow rate, and adsorption step time were investigated experimentally under the nonisothermal condition. The effect of the P/F ratio was noticeably changed according to the adsorption pressure and feed flow rate conditions. The higher the adsorption pressure, the slower the increasing rate of purity and the higher the decreasing rate of recovery. However, as the adsorption pressure became higher, the effect of the P/F ratio on the O2 purity became smaller. Furthermore, the effect of adsorption pressure on the O2 purity and recovery was diminished gradually to the increase of the P/F ratio. The feed flow rate also had a strong effect on the O2 purity. As for the product purity, the low feed flow rate began to lose its advantage with an increase in the P/F ratio. The recovery and productivity at a high feed flow rate was higher than those at a low feed rate even under the high product purity region. The dominant operating factor to determine the O2 purity was changed from the adsorption pressure to the feed flow rate as the P/F ratio was changed from low to high values. The modified linear driving force (LDF) model similar to a solid-diffusion model predicted the transition behavior of the cyclic process better than the LDF model.

Adsorption Characteristics of Hydrogen Mixtures in a Layered Bed: Binary, Ternary, and Five-Component Mixtures

Adsorption characteristics in a layered bed packed with activated carbon and zeolite 5A were studied experimentally and theoretically through the breakthrough experiments of binary (H2/CO, H2/CH4, H2/CO2), ternary (H2/CH4/CO), and five-component (H2/CH4/CO/N2/CO2) systems. The effects of adsorption pressure, feed flow rate, and carbon-to-zeolite ratio on the breakthrough curve in a layered bed were observed. Breakthrough curves in all of the mixtures showed tailing due to temperature variance in the bed by the heat of adsorption. In the layered bed, each mixture showed the specific characteristics of concentration and temperature wave fronts in each layer. Although the amount of impurity in a ternary mixture is larger than that in a binary mixture, the breakthrough time and elongation depending on the adsorption pressure and flow rate showed an intermediate value between the results of the H2/CO and H2/CH4 mixtures, and the tailing was not much different from those in these binary systems. Also, the roll-...

Effect of adsorption pressure on methane purity during PSA separations of CH 4/N 2 mixtures

Computer simulations have been carried out to study the performance of a two-bed PSA system for the separation of methane and nitrogen. The concentration of CH 4 in the low-pressure product has been assessed in terms of the adsorption pressure, CH 4 content in the feed gas and the cycle length. This concentration is found to exhibit a distinct maximum with respect to the pressure of the adsorption step. The occurrence of the maximum is attributed to selectivity varying with pressure, which, in turn, results from the nonlinearity of the CH 4 and N 2 adsorption isotherms. If linear isotherms are assumed, as is the case in simplified solutions, no such maximum is observed and the model fails to predict the crucial characteristics of the system.

Separation of Hydrogen Mixtures by a Two-Bed Pressure Swing Adsorption Process Using Zeolite 5A

A study on a two-bed six-step pressure swing adsorption (PSA) process using zeolite 5A was performed experimentally and theoretically for bulk separation of H2/CO and H2/CH4 systems (70/30 vol %) as major components in coke oven gas. When the pressure is cycled between 1 and 11 atm at ambient temperatures, 70% H2 in the feed could be concentrated to 99.99% in the product with a recovery of 75.87% in the H2/CO mixture and 80.38% in the H2/CH4 mixture. The effects of adsorption pressure, P/F ratio, adsorption/purge step time, and pressure equalization step time were investigated experimentally. If the product end of an adsorption bed was not contaminated during the adsorption and depressurizing pressure equalization steps, elongation of both the adsorption and purge steps gave good adsorbent productivity and recovery without any decrease in purity. Certain elongations of step time in the pressure equalization step resulted in a better performance of a PSA process. When the H2 mole fraction of effluent stream during the pressure equalization step was not high, the initial H2 purity of the adsorption step was not good because of the contamination of the product end section. These results were analyzed by a mathematical model incorporating heat and momentum balances.

Production of High-Purity Nitrogen from Air by Pressure Swing Adsorption on Zeolite X

Abstract A PSA air separation process for the production of high purity nitrogen is studied experimentally and theoretically. The experimental apparatus is composed of three columns filled with zeolite X. The PSA cycle consists of six steps: pressurization with air, adsorption, recovery, null, high pressure purge with product nitrogen, and desorption. The nitrogen purity analyzed between 95.0 and 99.992%. The effects of adsorption pressure and reflux ratio on the PSA performance are studied experimentally. The productivity is 2.8 NL/(kg·min) and the recovery is 55% at a nitrogen purity of 99.99% and an adsorption pressure of 800 mmHg. The experimental results are compared with the theoretical model, and the effects of the recovery step and the operating variables on the performance are studied theoretically. The recovery step makes the PSA performance favorable, especially in the high product purity region above 99%.