Simulation study of pressure swing adsorption to purify helium using zeolite 13X

A two-bed pressure swing adsorption system on a commercial type of zeolite 13X adsorbent has been studied numerically over a wide range of operating conditions to helium separation from gaseous mixture. The model includes energy, mass and momentum balances. The coupled partial differential equations are solved using fully implicit forth order Rung-Kutta scheme in the simulation. The effects of adsorption step pressure, adsorption step time and feed flow rate on the helium purity and recovery were investigated. Results shown that as the adsorption step pressure increases the helium purity will be increased. In addition, the helium recovery increases, and the helium purity decreases when the feed flow rate increases. Finally, the simulation results indicated a very good agreement with some current literature experimental work.

Simulation Study of Pressure Swing Adsorption to Purify Helium Using Zeolite 13X

A two-bed pressure swing adsorption system on a commercial type of zeolite 13X adsorbent has been studied numerically over a wide range of operating conditions to helium separation from gaseous mixture. The model includes energy, mass and momentum balances. The coupled partial differential equations are solved using fully implicit forth order Rung-Kutta scheme in the simulation. The effects of adsorption step pressure, adsorption step time and feed flow rate on the helium purity and recovery were investigated. Results shown that as the adsorption step pressure increases the helium purity will be increased. In addition, the helium recovery increases, and the helium purity decreases when the feed flow rate increases. Finally, the simulation results indicated a very good agreement with some current literature experimentally work.

Dynamic Study of VSA and TSA Processes for VOCs Removal from Air

Volatile organic compounds are air pollutants that necessitate to be eliminated for health and environment concerns. In the present paper, two VOCs, that is, dichloromethane and acetone are recovered by adsorption on activated carbon from a nitrogen gas stream. Experimental adsorption isotherms of the two VOCs are determined at three different temperatures 298, 313, and 323 K by the dynamic column breakthrough method. The dynamic mathematical model succeeds to predict satisfactorily the experimental breakthrough curves for pure VOCs and different binary mixtures for various conditions. Thus, the validated dynamic mathematical model has been used as a simulation tool for optimization purposes of VSA and TSA processes in order to achieve the highest performances under the given constraints. The effects of the adsorption step duration, the vacuum pressure, and the desorption temperature on the recovery of dichloromethane and acetone have been studied. A recovery of 100% of the two VOCs could be attained. However, the adsorption step duration should be determined precisely so as not to affect the recovery and alter the quality of air being purified due to the breakthrough of VOCs. The vacuum pressure and the desorption temperature should be carefully chosen in order to both reduce the energy consumption and shorten the purge step duration. Regeneration by hot nitrogen stream seems to be more efficient than regeneration by reducing pressure.

Chlorate adsorption from chlor-alkali plant brine stream

Chlorates are present in the brine stream purged from chlor-alkali plants. Tests were conducted using activated carbon from coconut shell, coal or palm kernel shell to adsorb chlorate. The results show varying levels of adsorption with reduction ranging between 1.3 g/L and 1.8 g/L. This was higher than the chlorate generation rate of that plant, recorded at 1.22 g/L, indicating that chlorate can be adequately removed by adsorption using activated carbon. Coconut based activated carbon exhibited the best adsorption of chlorate of the three types of activated carbon tested. Introducing an adsorption step prior to purging of the brine will be able to reduce chlorate content in the brine stream. The best location for introducing the adsorption step was identified to be after dechlorination of the brine and before resaturation. Introduction of such an adsorption step will enable complete recovery of the brine and prevent brine purging, which in turn will result in less release of chlorides and chlorates to the environment.

Lump Kinetic Analysis of Syngas Composition Effect on Fischer-Tropsch Synthesis over Cobalt and Cobalt-Rhenium Alumina Supported Catalyst

<p>This study investigated lump kinetic analysis of Fischer-Tropsch synthesis over Cobalt and Cobalt-Rhenium Alumina supported catalyst (Co/γ-Al₂O₃ and Co-Re/γ-Al₂O₃) at 20 bars and 483 K using feed gas with molar H₂/CO ratios of 1.0 to 2.1. Syngas with H₂/CO molar ratio of 1.0 represents syngas characteristic derived from biomass, while the 2.1 molar ratio syngas derived from coal. Rhenium was used as the promoter for the cobalt catalyst. Isothermal Langmuir adsorption mechanism was used to build kinetic model. Existing kinetic model of Fischer-Tropsch synthesis over cobalt alumina supported catalysts only valid for operating pressure less than 10 bar. CO insertion mechanism with hydrogenation step of catalyst-adsorbed CO by catalyst-adsorbed H component as the rate-limiting step is valid for operating condition in this research. Higher H₂/CO ratio makes faster hydrogenation step and less-product dominated in the associative CO adsorption step and dissociative H₂ adsorption equilibrium step. Kinetic constant for hydrogenation step increases 73-421% in syngas with 2.1 H₂/CO molar ratio compared to condition with 1.0 H₂/CO molar ratio. Faster hydrogenation step (with higher kinetic constant) results in higher reactant conversion. Equilibrium constant for associative CO adsorption and dissociative H₂ adsorption step decreases 53-94% and 13-82%, respectively, in syngas with higher H₂/CO molar ratio. Less product dominated reactant adsorption step (lower equilibrium constant for CO and H₂ adsorption step) gives higher CH₄ product selectivity, which occurred on 2.1 molar ratio of syngas. Rhenium (Re) metal on cobalt catalyst with composition 0.05%Re-12%Co/γ-Al₂O₃ only gives effect as structural promoter, which only increases reactant conversion with the same product selectivity. Copyright © 2016 BCREC GROUP. All rights reserved</p><p class="HistoryArticleBCREC"><em>Received: 10^th November 2015; Revised: 10^th February 2016; Accepted: 16^th February 2016</em></p><p><strong>How to Cite</strong>: Tristantini, D., Suwignjo, R.K. (2016). Lump Kinetic Analysis of Syngas Composition Effect on Fischer-Tropsch Synthesis over Cobalt and Cobalt-Rhenium Alumina Supported Catalyst.<em> Bulletin of Chemical Reaction Engineering &amp; Catalysis</em>, 11 (1): 84-92. (doi:10.9767/bcrec.11.1.424.84-92)</p><p><strong>Permalink/DOI</strong>: <a href="http://dx.doi.org/10.9767/bcrec.11.1.424.84-92">http://dx.doi.org/10.9767/bcrec.11.1.424.84-92</a></p>

Modeling the Adsorption Step during Hydrogen Purification in Gas Treatment Application

The present work is interested in modeling the adsorption step for the process of Pressure Swing Adsorption (PSA) for hydrogen purification. This work aims at modeling the adsorption of one or more compounds in a mixture at different pressures ranging from 8 to 20 bars at ambient temperature. The flow was presented by the piston model with an axial dispersion. The equilibrium isotherm was expressed by the Langmuir model for the mono-component adsorption and the model of Langmuir extended for the multi-component adsorption. Moreover, two models of kinetic transfer between the gaseous and solid phases were considered, the first-order model based on the approximation of the Linear Driving Force (LDF) and a sophisticated model which is the Surface Diffusion model (SD). As a first step, the CH4/H2 mixture adsorption on activated carbon was studied. In a second step, the adsorption of CH4/CO2/H2 on activated carbon and of CH4/N2/H2 on a 5A° molecular sieve was studied taking into consideration an interaction parameter for the extended Langmuir model. The simulation results obtained after the resolution of the equations of the model in a developed program, compared with the experimental results from previous works, show a rather satisfactory agreement on the level of stoichiometric time and kinetic mass transfer.