Activated carbon was impregnated with different concentrations of SnCl2.2H2O. Unimpregnated and impregnated activated carbons were analysed by means of physical adsorption and XPS and were tested for CO gas adsorption in a PSA system. The adsorption isotherms of N2 at 77 K were measured and showed a Type I isotherm indicating microporous carbon for all the samples. The surface area, pore volume and pore size distribution were reduced with impregnation. XPS analysis showed an increase in the intensity of Sn3d peak with impregnation. The impregnated activated carbon showed a very good adsorption ability of CO gas compared to the unimpregnated sample. The adsorptive species responsible for CO gas adsorption was confirmed to be SnO2 instead of SnO due to the former’s comparative thermodynamic stability. 相似文献
Huge amounts of global warming gas emissions have prompted interest in the recovery of H2 from off-gases in the iron and steel industries. Pressure swing adsorption (PSA) processes with layered beds packed with zeolite 5A and activated carbon were applied for H2 recovery from coal gas with relatively low H2 concentrations (H2/CO2/CH4/CO/N2; 38/50/1/1/10 vol.%). Breakthrough curves in the layered bed showed behavior results between the zeolite 5A bed and the activated carbon bed. The bed with the higher zeolite ratio produced H2 of higher purity in the PSA operation, but recovery loss became more significant with its increasing ratio. The variation of purity and recovery by operating variables were more significant in the two-bed PSA process than they were in the four-bed PSA process. The purity in the two-bed PSA varied asymptotically according to P/F ratio in the range of 0.1–0.3, while purity variation in the four-bed PSA process was almost linear. The zeolite layer in the two-bed PSA process worked as a separator of N2, while that in the four-bed PSA process worked as a purifier of N2. The four-bed PSA process could produce H2 with a purity of 96–99.5% and a recovery of 71–85% with N2 as the major impurity. The dynamics of the breakthrough and H2 PSA processes were studied using a non-isothermal dynamic model. 相似文献
An experimental study was performed for the recovery of CO2 from flue gas of the electric power plant by pressure swing adsorption process. Activated carbon was used as an adsorbent.
The equilibrium adsorption isotherms of pure component and breakthrough curves of their mixture (CO2 : N2 : O2=17 : 79 : 4 vol%) were measured. Pressure equalization step and product purge step were added to basic 4-step PSA for the
recovery of strong adsorbates. Through investigation of the effects of each step and total feed rate, highly concentrated
CO2 could be obtained by increasing the adsorption time, product purge time, and evacuation time simultaneously with full pressure-equalization.
Based on the basic results, the 3-bed, 8-step PSA cycle with the pressure equalization and product purge step was organized.
Maximum product purity of CO2 was 99.8% and recovery was 34%. 相似文献
A pressure swing adsorption (PSA) process for separating CO from a COCO2N2 mixture is proposed. The adsorbent used in this process is active carbon supported copper, which has been developed by this laboratory. By cycling the pressure of a bed of this adsorbent between ambient pressure and 20–30 Torr at room temperature, high purity CO can be obtained from the COCO2N2 gas mixture with a high recovery. The CO product purity depends crucially on the step of CO cocurrent purge after adsorption in the cycle and the regeneration of sorbent. 相似文献
Abstract Bulk separation of a five-component mixture simulating coal gasification products was performed by pressure swing adsorption (PSA) using activated carbon. The PSA cycle consisted of four commercially used steps: (I) pressurization with H2, (II) adsorption, (III) blowdown, and (IV) evacuation. Using this cycle, four products were obtained with a single PSA unit: H2 (over 99.7% purity), CO, CH4, and acid gas (CO2 + H2S). The first three products contained less than 0.001% H2S, and the acid gas was suitable for sulfur recovery. A mathematical model incorporating equilibrium adsorption of mixture and mass transfer resistance (of CO2) was found capable of simulating all steps of the PSA cycle. The model simulation results were in fair agreement with the experimental data. A fundamental understanding of the dynamics of the cyclic process was gained through the model. 相似文献
The performance of pressure swing adsorption (PSA), membrane separation, and gas absorption systems for H2 recovery from refinery off‐gas stream was studied by simulation‐based data. The PSA process was simulated using adsorbents of silica gel and activated carbon for removing heavy and light hydrocarbons. The mole fraction profiles of all components and the relationship between hydrogen purity and recovery as a function of feed pressure were examined. The solution‐diffusion model was applied for modeling and simulation of a one‐stage membrane process. The gas absorption process with a tower tray was simulated at sub‐zero temperature and the correlation between hydrogen purity and recovery as a function of tower pressure and temperature was evaluated at different solvent flow rates. 相似文献
Hydrogen was recovered and purified from coal gasification-produced syngas using two kinds of hybrid processes: a pressure swing adsorption (PSA)-membrane system (a PSA unit followed by a membrane separation unit) and a membrane-PSA system (a membrane separation unit followed by a PSA unit). The PSA operational parameters were adjusted to control the product purity and the membrane operational parameters were adjusted to control the hydrogen recovery so that both a pure hydrogen product (>99.9%) and a high recovery (>90%) were obtained simultaneously. The hybrid hydrogen purification processes were simulated using HYSYS and the processes were evaluated in terms of hydrogen product purity and hydrogen recovery. For comparison, a PSA process and a membrane separation process were also used individually for hydrogen purification. Neither process alone produced high purity hydrogen with a high recovery. The PSA-membrane hybrid process produced hydrogen that was 99.98% pure with a recovery of 91.71%, whereas the membrane-PSA hybrid process produced hydrogen that was 99.99% pure with a recovery of 91.71%. The PSA-membrane hybrid process achieved higher total H2 recoveries than the membrane-PSA hybrid process under the same H2 recovery of membrane separation unit. Meanwhile, the membrane-PSA hybrid process achieved a higher total H2 recovery (97.06%) than PSA-membrane hybrid process (94.35%) at the same H2 concentration of PSA feed gas (62.57%).
Fixation of nitrogen oxides (NOx) in air onto granular activated carbon impregnated with chemicals was attempted to improve removal efficiency of NOx by activated carbon adsorption. Nitric oxide (NO) and nitrogen dioxide (NO2), were tried to remove by a flow test. Fixed-bed adsorption breakthrough curves were obtained when some kinds of carbon were
used. The amount adsorbed of NO2 changed with the amount and kinds of metallic salts impregnated. Chemicals-impregnated carbons were prepared from a commercial
activated carbon. Among obtained carbons, the one which showed the highest selectivity for NOx was chosen, and its performance with the change in humidity was determined. Removal mechanism of NO2 was estimated, and the carbon impregnated with potassium hydroxide was found to be superior to any other carbon tested. The
amount of the adsorbed NO and that produced by the reduction of NO2 were determined from the breakthrough curves. 相似文献
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%). 相似文献
The production of high purity hydrogen (99.99+%) at reduced cost is an important and sought target. This work is focused on the separation of hydrogen from a five component mixture (H2/CO2/CH4/CO/N2) by pressure swing adsorption. A complete mathematical model that describes the dynamic behaviour of a PSA unit is presented. This model is applied in the study of the behaviour of both single column and four columns PSA processes with layered activated carbon/zeolite beds and with an eight steps cycle. In the single column simulation, a 99.9994% purity hydrogen stream is attained at the end of the feed step for a process hydrogen recovery of 51.84% and a productivity of . The multicolumn simulation predicts a hydrogen recovery and purity, respectively, of 52.11% and 99.9958%. The influence of feed flow rate, purge to feed ratio and lengths of both adsorbent layers on the system performance is assessed. It is shown that the introduction of the zeolite layer improves both the purity and recovery of the process. Reduced models are formulated based on the sequential identification of controlling resistances in the complete model. The predictions of the reduced models are evaluated by comparing their results with those obtained from the complete model. It is shown that the model that merely takes into account the micropore resistance (described by the LDF model) and assumes thermal equilibrium only between the gas and solid phases satisfactorily predicts the behaviour of the pressure swing adsorption unit. 相似文献
Abstract Hydrogen is the energy carrier of the future and could be employed in stationary sources for energy production. Commercial sources of hydrogen are actually operating employing the steam reforming of hydrocarbons, normally methane. Separation of hydrogen from other gases is performed by Pressure Swing Adsorption (PSA) units where recovery of high‐purity hydrogen does not exceed 80%. In this work we report adsorption equilibrium and kinetics of five pure gases present in off‐gases from steam reforming of methane for hydrogen production (H2, CO2, CH4, CO and N2). Adsorption equilibrium data were collected in activated carbon at 303, 323, and 343 K between 0‐22 bar and was fitted to a Virial isotherm model. Carbon dioxide is the most adsorbed gas followed by methane, carbon monoxide, nitrogen, and hydrogen. This adsorbent is suitable for selective removal of CO2 and CH4. Diffusion of all the gases studied was controlled by micropore resistances. Binary (H2‐CO2) and ternary (H2‐CO2‐CH4) breakthrough curves are also reported to describe the behavior of the mixtures in a fixed‐bed column. With the data reported it is possible to completely design a PSA unit for hydrogen purification from steam reforming natural gas in a wide range of pressures. 相似文献
Abstract Hydrogen separation by the four-bed PSA process using layered beds of activated carbon and zeolite 5A was investigated experimentally and theoretically to recover high purity H2 from steam methane reforming off-gas. The recovery increased with increasing the residence time at given product purity because of the contact time between the impurities and the adsorbents is increased. The difference of increasing the recovery became smaller with increasing the residence time and then the recovery was not increased after 43.6 seconds of the residence time. The minimum residence time exists to obtain the maximum recovery at desired product purity (99.999%+). 相似文献
The separation/concentration of SF6, a strong greenhouse gas, of 1.3% in N2 was investigated using pressure-temperature swing adsorption (PTSA) with activated carbon. To screen an effective adsorbent
to be used for PTSA, adsorption isotherms on the selected adsorbents were obtained. Among the studied adsorbents, AC-1, a
coconut-shell based commercial activated carbon, showed the largest adsorption amount of 3.5 mmol-SF6/g-carbon at 303.65 K and 3 atm and the highest selectivity among the adsorbents tested. Its adsorption isotherm was well
fit into Langmuir-Freundlich model. Before feasibility test of PTSA, a series of experiments were performed to investigate
the effect of operating parameters including adsorption pressure, feed flow rate, desorption temperature and evacuation time
on the PTSA performance using the 3-step PTSA cycle (pressurization, adsorption and regeneration-recovery). As the adsorption
pressure, desorption temperature and evacuation time were increased, respectively, purity and recovery increased. Increasing
the feed flow rate resulted in low purity and recovery. The maximum purity of 19.5% and recovery of 50.1% were obtained with
adsorption pressure of 2.5 atm, desorption temperature of 200 °C and evacuation of 1 hour. 相似文献
Air purification and vapor recovery by pressure swing adsorption (PSA) were experimentally investigated using the silicalite-DMMP-air system. The results from several cyclic steady-state PSA runs were compared at constant throughput with those from a previous study on the BPL activated carbon-DMMP-air system. The performance of BPL activated carbon was superior to that of silicalite because it demonstrated complete cleanup of the product effluent when starting from a saturated column, whereas, at similar process conditions, silicalite was able to cleanup only a portion of the product effluent. Nevertheless, both silicalite and BPL activated carbon respectively demonstrated enrichments (Ye/Yf) of 12 and 15 using only moderate vacuum. However, there were significant differences in the shapes of the cyclic steady-state product and exhaust profiles which were attributed to differences in the 1) mass transfer rates, 2) adsorption capacities, or 3) possibly shapes of the adsorption isotherms. 相似文献
Equilibrium adsorption and desorption isotherm data at room temperature are reported for cyanogen chloride and hydrogen cyanide vapors on BPL grade activated carbon, ASC whetlerite and several ASB impregnated carbons. Isotherm data have been analyzed in terms of the Dubinin-Polanyi equation. The experimental affinity coefficients (βex) for the vapors, with respect to chloroform, were determined from the slope of the Dubinin-Polanyi plot. The relative adsorptive capabilities of the adsorbents were assessed by comparing the theoretical affinity coefficient (βth) with βex · βth was estimated assuming that physical adsorption is the dominant adsorption process. Cyanogen chloride shows about 20% higher adsorption than predicted on BPL activated carbon and about 30% higher than predicted on the ASB impregnated carbons. Hydrogen cyanide shows about 30% higher adsorption than predicted on BPL activated carbon and about 45% higher adsorption than predicted on the ASB impregnated carbons. In the case of ASC whetlerite, the adsorption of both vapors was much greater than predicted and the isotherms displayed a levelling-off trend in the low pressure region indicating strong retention through chemisorptive interactions. No unique βex could be determined from the original isotherms. An attempt was made to separate the chemisorption contribution from the total adsorption, and thus assess βex for the physical adsorption contribution. 相似文献
An efficient design for pressure swing adsorption (PSA) operations is introduced for CO2 capture in the pre-combustion process to improve H2 recovery and CO2 purity at a low energy consumption. The proposed PSA sequence increases the H2 recovery by introducing a purge step which uses a recycle of CO2-rich stream and a pressure equalizing step. The H2 recovery from the syngas can be increased over 98% by providing a sufficient purge flow of 48.8% of the initial syngas feeding rate. The bed size (375m3/(kmol CO2/s)) and the energy consumption for the compression of recycled CO2-rich gas (6 kW/(mol CO2/s)) are much smaller than those of other PSA processes that have a CO2 compression system to increase the product purity and recovery. 相似文献