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  • Articles  (15)
  • pressure swing adsorption  (15)
  • Springer  (15)
  • 1995-1999  (15)
  • 1945-1949
  • Process Engineering, Biotechnology, Nutrition Technology  (15)
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  • Articles  (15)
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  • Springer  (15)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 1 (1995), S. 153-164 
    ISSN: 1572-8757
    Keywords: bulk separation ; pressure swing adsorption ; radial flow chromatography ; air separation ; oxygen enrichment ; zeolite 5A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new PSA process has been proposed and experimentally verified. This process was operated with a radial flow geometry under a cycle time less than 30 seconds. It has been showed that enriched oxygen could be produced when air was fed inward. The same system showed virtually no separation effect if the feed direction was reversed. The change of separation efficiency upon flow reversal was most significant when small adsorbent particles were employed. A ø 200×75 mm annular packing with 3 µm particles of zeolite 5A was able to produce 60% purity oxygen from air. The effect of flow direction on system performance confirmed the importance of flow resistance distribution. In radial flow geometry, most of the flow resistance was located near the center of the disk. The relative small pressure gradient at the feed end enabled a better absorbent utilization during the inward feed step, and a more effective desorption during the vent step. The same principle could be extended to other geometric configurations.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 1 (1995), S. 203-211 
    ISSN: 1572-8757
    Keywords: simulation ; pressure swing adsorption ; fixed bed system ; bulk separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Effects of variable feed composition on the performance of a pressure swing adsorption process are analyzed by simulation. Two scenarios are considered. The first, “increasing impurity,” case considers low impurity concentration in the feed followed by high impurity concentration in the feed. The second, “decreasing impurity,” case considers high impurity concentration in the feed followed by low impurity concentration in the feed. These results are compared against a case which has an impurity concentration in the feed at an average of the high and the low impurity concentrations. Simulations show that the increasing impurity scenario is expected to perform better, and the decreasing impurity scenario is expected to perform worse than the average feed concentration case.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 1 (1995), S. 313-320 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; air separation ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A novel rapid pressure swing adsorption (RPSA) process is described for production of 25–50% oxygen enriched air. The embodiment consists of one or more pairs of adsorbent layers contained in a single adsorption vessel. The layers undergo simultaneous pressurization-adsorption and simultaneous depressurization-purge steps. A total cycle time of 6–20 seconds is used. The process yields a very large specific oxygen production rate and a reasonable oxygen recovery for production of 20–50 mole% oxygen enriched gas. It is demonstrated by a simple mathematical model of isothermal single adsorbate pressure swing ad(de)sorption concept on a single adsorbent particle that the specific production rate of a PSA process cannot be indefinitely increased by reducing the cycle time of operation when adsorbate mass transfer resistances are finite.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 1 (1995), S. 321-333 
    ISSN: 1572-8757
    Keywords: processes and applications—bulk separation ; simulation ; pressure swing adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Gas separation of a binary gas mixture by various pressure swing adsorption (PSA) cycles was studied by a numerical simulation in order to provide a guidance in selecting PSA cycles. PSA cycles considered in this study are 3, 4-step cycles for production of only one component and a cycle with pressure equalization for production of a light component. 4 and 5-step cycles for simultaneous production of both components of a binary gas mixture are also considered. Separation of a CH4/CO2 gas mixture with zeolite 5A was chosen as a case study. Performances of cycles were examined and compared in view of purity, recovery and productivity. Their relative advantages were discussed. Inclusion of a purging step to a 3-step cycle for production of only one component improves a cycle performance. Further performance improvement of a cycle for production of a light component can be achieved by employing pressure equalization. Sircar's 4-step cycle with a recycle of effluent shows the best performance in view of purity and recovery among cycles for simultaneous production of both components.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 2 (1996), S. 111-119 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; bulk separation ; experiments ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The piston-driven ultra rapid pressure swing adsorption (URPSA) equipment was developed and oxygen enrichment from air was examined as an example. The adsorbent bed is directly connected to the cylinder where a piston moves at high frequency. Thus pressurization and depressurization in the bed are driven by mechanical piston motion, which can achieve far more rapid cycles compared with the conventional pressure swing operation using valves. The cycle time is usually on the order of seconds or sub seconds. Oxygen enrichment from air up to about 60% or higher of oxygen concentration was achieved by small-scale equipment using zeolite 5A with a oxygen production capacity of 100 Nm3-product gas/m3-zeolite/hr, which is about ten times larger than those of commercialized PSAs for this purpose. A simplified numerical model describing the mass transfer taking place in URPSA was developed. The model could simulate fairly well the air separation characteristics in terms of oxygen concentration, oxygen production capacity and oxygen yield. The proposed model helps in the understanding of the basic nature of URPSA and possible applications. This novel PSA is promising as a compact yet high-capacity PSA to be utilized in a wide variety of applications.
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  • 6
    Electronic Resource
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    Adsorption 2 (1996), S. 323-326 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; air separation ; zeolite ; rapid cycle ; heat integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The capital and energy costs of production of oxygen enriched air by a rapid pressure swing adsorption (RPSA) process can be reduced by decoupling the air drying and the air separation duties of the process. Integration of the oxygen-RPSA process with an enhanced combustion application system allows thermal swing adsorption drying of air feed to the RPSA process. The air separation process then can be run using an ad(de)sorption pressure envelope of 2:1 atmospheres, which significantly reduces the cost and energy of operation of the air compressor.
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  • 7
    Electronic Resource
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    Springer
    Adsorption 2 (1996), S. 299-309 
    ISSN: 1572-8757
    Keywords: intraparticle convection ; intraparticle diffusion ; pressure swing adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The importance of intraparticle convection during and after the pressurization step of a pressure swing adsorption process is assessed by considering a single, cylindrical, closed-end pore with adsorptive walls exposed to a binary mixture of an adsorbable component and an inert gas. Gas-phase mass transfer is comprised of pore diffusion and convection, and surface diffusion occurs in the adsorbed phase. Concentration, velocity, and flux profiles are obtained inside the pore both during and after pressurization. Solutions are obtained analytically for the limiting cases of no adsorption, no diffusion, and no inert gas. Complete solutions of the material balance equations are obtained by orthogonal collocation. The pressurization rate, the adsorptive capacity of the pore wall, and the gas-phase mole fraction are varied over a wide range to study the relative importance of convection and diffusion under different conditions. Results show that convection makes a large contribution to transport in the pore except when the adsorbable component has a small mole fraction.
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  • 8
    Electronic Resource
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    Adsorption 3 (1996), S. 127-136 
    ISSN: 1572-8757
    Keywords: intraparticle convection ; intraparticle mass transfer ; pressure swing adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The importance of adsorption induced convection in the macropores of a bidisperse adsorbent particle is studied for a step change in mole fraction or total pressure at the surface of the particle. Material balance equations for a binary gas mixture are written for both the macropores and the macropores with allowance for convection in the macropores, which is described by Darcy's law. The coupled set o1' partial differential equations is solved by orthogonal collocation. The enhancement in mass transfer as a result of convection is assessed by comparing the fractional uptake curves obtained with and without allowance for convection. Both equilibrium-based and kinetic-based separation processes are considered. The effect of the presence of convection in determining the controlling diffusional resistance (macropore or micropore) is also examined. Due to inclusion of convection no single non-dimensional group alone can determine the relative importance of macropore and micropore resistances. Results show that convection can significantly affect the performance of an equilibrium-based macropore diffusion controlled process and that the enhancement in mass transfer is more for a particle with a high value of Darcy permeability.
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  • 9
    Electronic Resource
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    Adsorption 3 (1996), S. 151-163 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; environmental ; activated carbon ; simulation ; factorial design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A two-level fractional factorial study was performed by computer simulation on the periodic state process performance of a pressure swing adsorption-solvent vapor recovery process (PSA-SVR). The goal was to investigate factor (parameter) interaction effects on the process performance, i.e., interaction effects that cannot be ascertained from the conventional “one-at-a-time” approach. Effects of seven factors, i.e., the purge to feed ratio, pressure level, pressure ratio, heat transfer coefficient, feed concentration, feed volumetric flow rate and bed length to diameter ratio, on the process performance were investigated. The results were judged in terms of the light product purity, heavy product enrichment (and relative enrichment) and recovery, and bed capacity factor. Only the purge to feed ratio, pressure ratio, and feed concentration had significant effects on the benzene vapor enrichment (and relative enrichment); and no two-factor and higher interactions were observed. The light product purity was affected by all seven factors; and the relative importance of the effect of each factor depended on the levels of the other factors, i.e., significant two-factor interaction effects existed. Two-factor interaction effects also existed on the benzene vapor recovery, although the effects of all seven factors and their interactions were relatively small. The bed capacity factor was affected mainly by the purge to feed ratio, the heat transfer coefficient and the feed concentration; two factor and higher order interaction effects were insignificant. Overall, this study demonstrated the utility of fractional factorial design for revealing factor interactions and their effects on the performance of a PSA-SVR process.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Adsorption 4 (1998), S. 149-158 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; gas separation ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In a multi-bed pressure swing adsorption (PSA) process, cycle steps with gas flow transferring from one bed to another such as equalization, purge, etc. are generally practiced to enhance the product recovery. However, if the flows for the connected beds in these steps are not balanced, the PSA process may not operate in a symmetrical manner. In the modeling of the PSA process, most of the simulations consider only one bed and assume that the rest of the beds would behave in a same way. In order to assess the impact of bed symmetry on the PSA performance, a new PSA model capable of studying bed symmetry in a two-bed system is developed. Experimental results from this paper show that uneven equalization flow can result in a lower product purity and a peculiar purity curve at different equalization levels. This phenomenon can be successfully predicted by this model. Simulation results also show that in large-scale PSA units, asymmetrical operation can cause drastically different temperature profiles in different adsorbers and hence a much lower performance. This paper demonstrates the importance of maintaining operation symmetry in PSA processes.
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  • 11
    ISSN: 1572-8757
    Keywords: heat effects ; pressure swing adsorption ; temperature swing adsorption ; multicomponent mass transport ; dusty-gas model ; boundary conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A detailed model for nonisothermal sorption of multicomponent mixtures in a single sorbent particle (monodisperse or bidisperse with negligible intracrystalline mass transport limitations) under pressure swing conditions is developed in this study. The dusty-gas model is used to describe the coupling of the molar fluxes, the temperature, the partial pressures and the partial pressure gradients of the components in the pore space of the particle. The variations of the temperature are described by an energy equation in which both convective and conductive modes of heat transport are accounted for. No limitations are imposed on the number of the components in the mixture and on the type of the adsorption isotherm. The model is applied in the investigation of the industrially important air-zeolite 5A system. Two cases with respect to the surrounding gas phase are examined: infinite environment, which is representative for single particle experiments, and finite environment, which is representative for the situation in packed bed adsorbers. It is found that in an infinite environment the external and internal temperature gradients are equally important while in a finite environment the external heat transport limitations are negligible. It is concluded that in modeling the nonisothermal operation of adsorption processes occurring in packed beds it is not necessary to allow for the temperature differences between the gas phase and the surface of the adsorbing particles. Furthermore, if the temperature gradients within the particles can be neglected, only a single temperature equation is needed to describe the energy transport in the bed.
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  • 12
    Electronic Resource
    Electronic Resource
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    Adsorption 4 (1998), S. 337-344 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; mathematical models ; numerical simulation ; finite difference ; adaptive time stepping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Three different finite-difference routines were compared for solving the nonlinear, coupled, partial differential and algebraic equations that describe pressure swing adsorption processes. A successive substitution method (SS), a block LU decomposition procedure (BLUD), and the method of lines approach with adaptive time stepping (DASSL) were used to simulate and compare the computation times required to reach the periodic state for two different PSA systems: PSA-air drying and PSA-solvent vapor recovery. For both systems, the results showed that DASSL was nearly twice as fast as BLUD, whereas SS was nearly an order of magnitude slower than BLUD. DASSL and BLUD were also very robust and accurate, as nearly identical bed profiles were obtained from both methods under both transient and periodic state conditions.
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  • 13
    ISSN: 1572-8757
    Keywords: materials ; synthesis techniques ; biochemical ; pressure swing adsorption ; characterization of properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Corn grits have been tested as a desiccant in a pressure swing adsorption (PSA) system to produce dry air. Two sizes of unmodified corn grits were tested in the PSA system: 2.16 and 0.978 mm in diameter, which dried moist air to dew points of −42°C and −69°C, respectively. A modification technology has been developed for the corn grits that gives an increase in the operational adsorptive capacity in a pressure swing adsorption system, so that they remove as much moisture from air as molecular sieves at the same conditions. After modification, 2.16 mm corn grits dry moist air to a −56°C dew point and the 0.978 mm corn grits dry air to a −80°C dew point. The modification process creates surface modifications on the corn grits apparently making more adsorption sites easily available. The modification procedure increases the specific surface area of the grits and possibly decreases the crystallinity, which would make more hydroxyl groups available for adsorption of water. Possible applications of using corn grits in the pressure swing adsorption system include industrial gas dryers, sorptive cooling air conditioners, and recycling equipment for industrial solvents.
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  • 14
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    Adsorption 5 (1999), S. 193-197 
    ISSN: 1572-8757
    Keywords: adsorption equilibrium ; lattice theory ; pressure swing adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new multicomponent equilibrium relation is proposed for engineering applications. This relation is based on a lattice model for mixtures of unequally sized molecules. An approximation is introduced for loading-dependent enthalies of adsorption that simplifies the energy balance in fixed-bed models and allows efficient solution of the equation set in process simulations. Comparisons are made with nonideal binary data in the literature.
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  • 15
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    Adsorption 5 (1999), S. 245-259 
    ISSN: 1572-8757
    Keywords: pressure swing adsorption ; equilibrium model ; analytical solution ; optimum co-current depressurization pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Five-step PSA cycles consisting of pressurization with product, adsorption, co-current depressurization, blowdown, and purge steps have been analyzed with equilibrium model assuming uncoupled linear isotherms and isothermal condition. Unlike the previous models, the proposed model is not restricted to the operating conditions that ensure a complete shock transition of concentration profile at the end of the high pressure adsorption step. The operating conditions could have two classifications: one is utilizing the column completely before blowdown, and the other is not. As the selectivity increases, it is more difficult to utilize the column completely before the blowdown step. There is an optimum co-current depressurization pressure which maximizes the recovery at the given extent of purge. The optimum co-current depressurization pressure decreases as the purge quantity decreases. On the less selective adsorbent, the recovery at the optimum co-current depressurization pressure increases with the decrease of purge quantity without much sacrifice of the throughput. But, on the highly selective adsorbent, there is an extent of purge and corresponding value of cocurrent depressurization pressure below which the recovery is not greatly improved while the throughput decreases rapidly, which limits the number of pressure equalization steps can be included.
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