Radial flow rapid pressure swing adsorption

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.     

Study on Pressure Swing Adsorption Removing C2^＋ from Natural Gas as Raw Material for Thermal Chlorination

The experimental investigation demonstrates that a setisfactory can be expected for pressure swing adsorption (PSA) purification of natural gas as raw material for thermal chlorination process.Using hh-4 molecular sieve as adsorbent for removing C2^ components,the suitable adsorption pressure is 0.4-0.45 MPa,desorption vacuum is 0.08-0.09 MPa and circulation time is 20-21 min.     

Adsorption Calculations Using the Film Model Approximation for Intraparticle Mass Transfer

An approximate rate equation based on a film-model representation of diffusional mass transfer has been developed to describe the kinetics of multicomponent adsorption. The model describes mass transfer as a pseudo-steady state diffusion process through a flat film of thickness equal to one fifth of the particle radius. The flux relationships are integrated across the film yielding analytical expressions for the rate of mass transfer in a multicomponent adsorption system. The usefulness of the film model approximation is tested by carrying out calculations for three different practical adsorption systems: the adsorption of n-pentane and n-heptane mixtures on NaCaA zeolite discussed by Marutovsky and Bülow (1987); the adsorption of air in molecular sieve RS-10 discussed by Farooq et al. (1993); and the separation of air in a kinetically-controlled nitrogen PSA process discussed by Farooq and Ruthven (1990) and Sundaram and Yang (1998). In each case, the film model approximation predicts the expected trends accounting for the coupling of diffusion fluxes in the adsorbed phase.     

Fractional factorial design study of a pressure swing adsorption-solvent vapor recovery process

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.Nomenclature BCF bed capacity factor, % - b, b ₀ isotherm parameters, m³/(mol K^0.5) - C _pg gas phase heat capacity, kJ/(kg K) - C _ps solid phase heat capacity, kJ/(kg K) - E enrichment - E _I ideal enrichment - E _R relative enrichment - H heat transfer coefficient, kJ/m² s K) - H heat of adsorption, kJ/mol - k number of factors, or mass transfer coefficient, l/s - l number of levels - L bed length, m - LD bed length to diameter ratio - PF purge to feed ratio - P _H adsorption high pressure, kPa - P _L desorption pressure, kPA - PL pressure level, represented byP _I - PR pressure ratio - q amount adsorbed, mol/kg - q ^xx equilibrium amount adsorbed, mol/kg - q ^xx _j equilibrium amount adsorbed at the feed conditions, mol/kg - r _b bed radius, m - R solvent vapor recovery, % or gas constant, m³ (mole K) - T temperature, K - T ₀ ambient temperature, K - t time, s - u interstitial velocity, m/s - VF volumetric feed flow rate, m³ STP/s - YF feed mole fraction - Y _p light product mole fraction - z axial coordinate, m Greek Symbols _g gas phase density, kg/m³ - _s solid phase density, kg/m³ - bed void fraction     

Air Separation by Carbon Molecular Sieves

The separation of nitrogen from air on a carbon molecular sieve is achieved by a difference in the adsorption kinetics of oxygen and nitrogen. Assuming the oxygen is adsorbed under equilibrium conditions, a simplified analysis is developed for determining the process performance. As expected, a good agreement is observed between the simplified and full analysis for long cycle times, but for short cycle times, neglecting the oxygen adsorption kinetics leads to erroneous purity predictions. Also, the effect of the adsorption/desorption rate constants on the performance of the pressure swing adsorption process is analyzed, and it is found to be a function of the adsorption/desorption step length. Good agreement between the numerical simulation and experimental results is observed over a wide range of product purities.     

Capture of CO2 from high humidity flue gas by vacuum swing adsorption with zeolite 13X

Capture of CO₂ from flue gas streams using adsorption processes must deal with the prospect of high humidity streams containing bulk CO₂ as well as other impurities such as SO _x , NO _x , etc. Most studies to date have ignored this aspect of CO₂ capture. In this study, we have experimentally examined the capture of CO₂ from a 12% synthetic flue gas stream at a relative humidity of 95% at 30 °C. A 13X adsorbent was used and the migration of the water and its subsequent impact on capture performance was evaluated. Binary breakthrough of CO₂/water vapor was performed and indicated a significant effect of water on CO₂ adsorption capacity, as expected. Cyclic experiments indicate that the water zone migrates a quarter of the way into the column and stabilizes its position so that CO₂ capture is still possible although decreased. The formation of a water zone creates a “cold spot” which has implications for the system performance. The recovery of CO₂ dropped from 78.5% to 60% when moving from dry to wet flue gas while the productivity dropped by 22%. Although the concentration of water leaving the bed under vacuum was 27%(vol), the low vacuum pressure prevented condensation of water in this stream. However, the vacuum pump acted as a condenser and separator to remove bulk water. An important consequence of the presence of a water zone was to elevate the vacuum level thereby reducing CO₂ working capacity. Thus although there is a detrimental effect of water on CO₂ capture, long term recovery of CO₂ is still possible in a single VSA process. Pre-drying of the flue gas steam is not required. However, careful consideration of the impact of water and accommodation thereof must be made particularly when the feed stream temperature increases resulting in higher feed water concentration.     

航天测量船船摇数据特性分析

简要介绍了远望号航天测量船船摇数据，分析了船摇数据对船载外测数据的影响，重点对船摇数据的一些基本规律和特性进行了初步分析。     

Impact of Pore Size and Defects on the Selective Adsorption of Acetylene in Alkyne-Functionalized Nickel(II)-Pyrazolate-Based MOFs

C₂H₂/CO₂ separation is a highly challenging process as a consequence of their similar physicochemical properties. In this work we have explored, by static and dynamic gas sorption techniques and computational modelling, the suitability of a series of two isoreticular robust Ni(II)pyrazolate-based MOFs, bearing alkyne moieties on the ligand backbones, for C₂H₂/CO₂ separation. The results are consistent with high adsorption capacity and selectivity of the essayed systems towards C₂H₂ molecules. Furthermore, a post-synthetic treatment with KOH ethanolic solution gives rise to linker vacancy defects and incorporation of extraframework potassium ions. Creation of defects is responsible for increased adsorption capacity for both gases, however, strong interactions of the cluster basic sites and extraframework potassium cations with CO₂ molecules are responsible for a lowering of C₂H₂ over CO₂ selectivity.     

Separation of H2O/CO2 Mixtures with Layered Adsorption Method for Greenhouse Gas Control

Multiple-layered vacuum swing adsorption technique was used and investigated in order to effectively keep the feed gas that flows into zeolite 13X zone being dry and keep the CAPEX down(not adding pre-treatment equipment). Activated carbon fiber(ACF) and alumina CDX were laid at the lower parts of the column as pre-layers to selectively adsorb moisture. Zeolite 13X was laid on the top of those two adsorbents as the main layer to capture CO₂. Systematic cyclic experiments show that water vapor was successfully contained within the ACF and CDX layers at cyclic steady states. It was also found that ultimate vacuum pressure played a decisive factor for stabilizing the water front, and achieving good CO₂ purity and recovery. The findings also reveal the pathway for large-scale CO₂ capture process.