Effect Of Regeneration Temperature Research Articles

The effect of regeneration temperature on the adsorptive properties of Na-ETS-4 zeotype in successive adsorption/desorption cycles

In view of the sensitivity of Na-ETS-4 zeotype to temperature, the effect of regeneration temperature on its adsorptive performance was investigated in this work. Adsorption isotherms and uptake kinetics of nitrogen and methane were measured after applying a heat treatment at temperatures of 100, 135, and 165 ◦C along with vacuum as thermal activation. Increasing the initial activation temperature in the 100–165 ◦C range led to an increase in adsorption capacity due to the intra-pore water removal. At 100 kPa, methane uptake increased from 0.2 to 0.35 mol/kg and nitrogen uptake increased from 0.07 to 0.16 mol/kg. By applying successive regenerations at 100 and 135 ◦C, the equilibrium/kinetic adsorption properties did not change. However, by successive regeneration of the adsorbent at 165 ◦C, the equilibrium capacity (for methane from 0.35 to 0.1, for nitrogen from 0.16 to 0.1 mol/kg at 100 kPa) and diffusion time constant parameter (for methane from 0.02 to 7.16 × 10−5 s−1) decreased gradually. Also, structural changes of Na-ETS-4 under successive high-temperature (i.e., 165 ◦C) regeneration were studied by XRD. A gradual reduction of Na-ETS-4 crystallinity was revealed after each regeneration at 165 ◦C. However, Na-ETS-4 showed stable adsorption performance when using only vacuum as regeneration method.

Experimental Investigation of Sorption-Enhanced CO2 Hydrogenation to Methanol

In this work, we investigate experimentally the use of zeolite 13X as an efficient water sorbent in the sorption-enhanced CO2 hydrogenation reaction over Cu/ZnO/Al2O3 under different operating conditions and over multiple reaction–regeneration cycles. Introduction of the solid sorbent along with the catalyst in the reactor leads to a prominent increase in the CO2 conversion and CH3OH yield. As the reaction proceeds, the sorbent gradually becomes saturated, the enhancement effect reduces, and the system eventually reaches the same steady state as with catalyst only. The CH3OH yield increase is higher than that of the CO2 conversion, indicating preferential enhancement of methanol production. This can be attributed to the partial co-adsorption of both methanol and water on zeolite 13X. The effects of reaction and regeneration temperature on the activity, product distribution, enhancement degree, and recyclability are also examined. The highest sorption enhancement occurs at 225 °C, with the methanol yield increasing by 115% compared to the conventional process. The cyclic stability is investigated by consecutive reaction–regeneration cycles. The correlation between activity reduction and textural properties of both the catalyst and sorbent as well as the zeolite’s ability to regenerate are explored. To that end, the effect of regeneration temperature on the products’ desorption is also examined.

Numerical study on effects of hydrothermal aging to composite regeneration in CeO2-based catalyzed diesel particulate filter

The effects of hydrothermal aging on the performance of CeO2-based catalyzed diesel particulate filter (CDPF) was numerically investigated in this study based on a zero-dimensional model using the plug flow reactor in which a chemical reaction kinetic mechanism was established and validated by the simulated gas environment experiment. The effects of regeneration temperature, O2 concentration in the ultimate emission conditions, the ratio of NO2 in NOx (α) and the ratio of NOx to soot (β) on catalyst deactivation temperature and soot oxidation rate were investigated with fresh and hydrothermal aging CeO2-based CDPF. The results show that hydrothermal aging of CeO2-based catalysts raises the regeneration temperature from 613 to 783 K and shifts the soot catalytic combustion reaction path from complete to incomplete oxidation. Soot oxidation rate of fresh catalyst first increases rapidly at 516 K and then starts to slow down gradually at 633 K, but for hydrothermal aging catalysts, are 601 K and 789 K, respectively. With O2 concentration increased from 1.5 mol/m3 to 5.5 mol/m3, the catalyst deactivation of fresh and hydrothermal aging catalyst increased from 609 K to 602 K, 791 K to 818 K, respectively. The increase in α and β leads to an increase in soot oxidation rate and a decrease in regeneration temperature. The deactivation temperature of catalyst is increased in higher α (1.0) and lower β (0.1), which the highest is 821 K. Synergistic mechanisms of NOx, regeneration temperature, and hydrothermal aging effects on soot catalytic combustion in CeO2-based CDPF are revealed deeply with the help of zero-dimensional model.

Study on regeneration characteristics of choline chloride-monoethanolamine deep eutectic solvent after capturing CO2 from biogas

Choline chloride-monoethanolamine deep eutectic solvent (ChCl-MEA DES) can deeply remove CO2 from biogas. This study focused on regeneration of ChCl-MEA DES after CO2 capture. The effects of regeneration temperature, time and water content on CO2 absorption capacity, absorption rate and CO2/CH4 absorption selectivity after regeneration were evaluated. The addition of HZSM-5 catalyst during regeneration further promoted regeneration efficiency. FTIR and NMR indicated that carbamates were formed after absorption, and water made it easier for the amino group to react with CO2 to form carbamates. The highest regeneration percentage of absorbent was up to 99.89%, and the CO2 absorption capacity even didn’t decrease significantly after 8 cycles. The ideal regeneration energy consumption in the experiment was also evaluated. This research provided a valuable reference for the application of this absorbent in CO2 purification of biogas.

Equilibrium and thermodynamic study of trichloroethylene adsorption on activated carbon in a fluidized bed and its thermal regeneration

AbstractVolatile organic compounds (VOC), used as solvents in industries, are major sources of air pollution. Trichloroethylene (TCE) is a chlorinated VOC widely used in industries. TCE vapours are toxic in nature and adversely affect human health and the surrounding environment when exposed over the threshold limit value for a long duration. Adsorption of TCE vapours using activated carbon as an adsorbent in a fluidized bed and its thermal regeneration is a viable, effective, and economic technology for its separation from air. However, before designing such a system, the equilibrium and thermodynamic study of the adsorption of TCE vapour on activated carbon is important. In this study, the dynamic adsorption of TCE vapour was carried out in a fluidized bed using nitrogen as the carrier gas. The effect of operating conditions, including particle size of activated carbon (212–710 μm), flowrate of nitrogen (carrier gas), adsorption temperature (303–353 K), and the concentration of TCE vapour in nitrogen at the inlet (25–85 mg/L) on the adsorption capacity of TCE on the fluidized bed of activated carbon, was examined. The experimental results obtained were analyzed using the Langmuir and Freundlich adsorption isotherms. The thermodynamic study showed that the adsorption of TCE was spontaneous, exothermic, and physical in nature. The effect of regeneration temperature and purge gas flowrate on the renewal of used activated carbon was also studied.

Study of gas and particulate emission characteristics during the fast regeneration period of DPF

Based on the diesel particulate filter (DPF) regeneration test bench and the particulate loading device, the effects of regeneration temperature and flow rate on the gas and particulate emissions during the fast regeneration period of the DPF are explored. The results show that the fast regeneration period is usually easy to occur during the DPF active regeneration process, which leads to the fast increase of the internal temperature of the DPF substrate. During the fast regeneration process, the gas and particulate emissions in the regeneration process are mainly concentrated in this period, accounting for 45.8%–83.2% and 61%–84% of the total emissions respectively. With the increase of the regeneration temperature, the proportion of gas emissions during the fast regeneration period decreases, while the proportion of particulate emissions remains essentially unchanged. Increasing the regeneration temperature does not significantly improve the regeneration efficiency in the fast regeneration period. With the increase of the flow rate, both the proportion of gas and particulate emissions decrease, and the DPF regeneration is inhabited. On the other hand, after the fast regeneration period, DPF regeneration enters the slow regeneration stage, the economy of input energy for the DPF regeneration gradually decreases. Controlling active DPF regeneration needs to take into account the impact of fast regeneration period on emission and input energy, together with the effect of regeneration temperature and flow rate.

Performance analysis of a novel double stage multifunctional open absorption heat pump system: An industrial moist flue gas heat recovery application

Rising industrial energy consumption and waste heat in moist flue gas exhausts are the key scientific issues. A potential hybrid system with efficient heat recovery technology can fulfill the industrial energy demand for dehumidification, heating and cooling applications by utilizing the waste latent heat. The main objective of this study is to present a multifunctional hybrid system for double stage open absorption cycle to recover the latent heat from the exhaust moist flue gas for heating and to dehumidify the ambient humid air for cooling applications by operating at low-grade heat source. The validated thermodynamic models for energy and exergy analysis are developed for its performance optimization and to conduct a comparison with single stage system. The operating inlet parameters are varied to analyze the performance of both systems. The parametric study results showed that the double stage system can operate for a wider moist gas humidity range such as 0.054–0.2 kg/kg at lower regeneration heat source of 96.3℃ with varying thermal performance of 1.24–2.39 as compared to the single stage system which operates for 0.118–0.2 kg/kg and at 112.3–153.8℃. Furthermore, this hybrid system is capable to provide heating effect of 280.1 kW at thermal performance of 1.73 and 9.85 kW cooling capacity while operating at 113.7℃ heat source temperature. The thermal performance of system is related to the operating pressure in low pressure generator and can be increased 8–11% when pressure is increased from 25 kPa to 35 kPa. However, the cooling capacity is found to be sensitive only to the absorbers and the dew point cooler. The exergy performance results indicate that the exergy efficiency of double stage system is 3–16% higher as compared to single stage with effect of regeneration temperature and varies from 46.2 to 58.63%. Moreover, the highest exergy destruction is found to be in regenerators which accounts for about 49–51% of overall destructed exergy.

Conventional regeneration of spent activated carbon from brewer’s spent grain

This work studied conventional regeneration of saturated activated carbon using muffle furnace. The activated carbon was prepared from brewer’s spent grain using carbonization and chemical activation with potassium hydroxide. It was saturated with methylene blue dye and regenerated using muffle furnace. Effect of 30% hydrogen peroxide (H202 ) as an oxidant in the regeneration process was studied. Adsorption – regeneration process was studied for six cycles. Regeneration condition was optimized using central composite design (CCD). Effect of regeneration temperature and time on the adsorptive capacity of regenerated carbon was studied for one cycle. Adsorptive capacity and regeneration efficiency were found to decrease with increase in the number of cycles. 30% H202 had a tremendous effect on the adsorptive capacity of the regenerated carbon. The adsorptive capacity increased as the temperature grew from 200°C to 500°C, but dropped after being raised to 6,000°C. Adsorptive capacity increased from 10 minutes to 30 minutes, but declined to 50 minutes. The Quadratic model was used to regenerate a long network of electronics devices. In this experiment, the parameters were exactly what were required for optimal adsorption: temperature of 537.76 degrees Celsius, time of 29.34 minutes, and an initial dye concentration of 100mg/L with estimated adsorptive capacity of 54.2827mg/L. This was an extremely small mistake of 0.02 percent following validation.

Research on Energy-Saving Experimental of Critical Dehumidification of Combined Drying by Dehumidification Wheel and Heat Pump

In order to further decrease the energy consumption of desiccant wheel dehumidification, the drying medium circulation characteristics of a system combining heat pump drying with desiccant wheel dehumidification were investigated. Moreover, the critical dehumidification conversion mechanism was studied. The analysis of the heat pump hot air circulation system demonstrated that the heat pump system has the best dehumidification efficiency. Through the analysis of the system combining heat pump drying with desiccant wheel dehumidification, the critical conversion point was determined. The critical dehumidification mechanism was further verified using an online temperature and humidity measurement system. To investigate the effect of the critical point on energy consumption and drying quality and develop a drying model, response surface experiments were performed based on the effects of regeneration temperature, drying temperature, and conversion point relative humidity on rehydration, color difference, and specific moisture extraction rate (SMER). The optimal conversion point humidity was determined to be about 46% RH, which was slightly different from the test optimization value of 45.6% RH. In addition, comprehensive optimization and experimental verification of the influencing factors were conducted. The results demonstrated that the R2 values of the three models were greater than 0.98, and the experimental factors had a significant effect on drying quality and energy consumption. When the regeneration temperature was 96°C, the drying temperature was 53°C, the relative humidity of the conversion point was 46%, the color difference was 46.3, the rehydration ratio was 5.75, and the SMER was 1.62 kg/kW·h.

Comparison of MIL-101(Cr) metal-organic framework and 13X zeolite monoliths for CO2 capture

Abstract A comparative study was conducted to determine the pore properties and adsorptive performance of monoliths containing either the MIL-101(Cr) metal-organic framework or 13X zeolite for carbon dioxide (CO2) capture. Although there have been a great deal of previous work on CO2 adsorption onto zeolites and MOFs, there has been far fewer studies on structured adsorbents such as monoliths. The results indicate that MIL-101(Cr) monoliths have 1.3 times higher porosity than 13X zeolite monoliths. Increasing CO2 partial pressure in the gas mixture shortens breakthrough and equilibrium times and increases the breakthrough and equilibrium adsorption capacities of CO2. MIL-101(Cr) monoliths show better mass transfer of CO2 in the adsorbent bed with shorter breakthrough and equilibrium times of about 20% and 35%, respectively, than 13X zeolite monoliths. The adsorption capacity of CO2 on MIL-101(Cr) monoliths is higher by about 37% (based on weight in mmol/g) at breakthrough and slightly lower by about 7% at equilibrium when compared to 13X zeolite monoliths. MIL-101(Cr) monoliths were found to be 1.5 times more efficient for CO2 adsorption than 13X zeolite monoliths. The effects of regeneration temperature after CO2 adsorption on MIL-101(Cr) and 13X zeolite monoliths were studied and results showed an increase in CO2 adsorption capacity as the regeneration temperature was increased. In summary, the study showed MIL-101(Cr) monoliths have better CO2 adsorption properties than 13X zeolite monoliths.

Enhanced CO2 sorption capacity of amine-tethered fly ash residues derived from co-firing of coal and biomass blends

Co-firing of coal and biomass blends provides a promising route for clean energy utilization with high efficiency and mitigated pollutants emission. However, the technology meets an important challenge in effective utilization of the co-firing fly ashes. Efforts have been made to valorize the co-firing fly ash residues as potential CO2 sorbents. To achieve enhanced CO2 sorption performance, the samples were modified with tetraethylenepentamine (TEPA). Effects of amine loading, CO2 sorption temperature, initial CO2 concentration and gas flow rate on CO2 sorption behaviors of the amine-tethered sorbents were investigated. The desired sorbent with 25% TEPA loading presented the highest CO2 sorption capacity of 1.19 mmol CO2/g when tested under 60 °C and 15%CO2 with a total gas flow rate of 1200 ml min−1. The effects of regeneration temperature and ramping rate on sorbent regeneration performance were demonstrated. The maximum sorbent regeneration efficiency of 97.2% was achieved under the regeneration condition of 110 °C and 5 °C min−1. CO2 sorption capacity of the amine-tethered sorbent kept stable within 5 repeated cycles. These findings indicate that the amine-tethered sorbent could be a good candidate for on-site CO2 capture from flue gas in co-firing power plants.

Investigation of CO2Absorption Kinetics and Desorption Performance in Aqueous 1-(2-Aminoethyl)-3-methylimidazolium Bromine Solution

The absorption rate and absorption amount of CO2 were determined at different 1-(2-aminoethyl)-3-methylimidazolium bromine ([Aemim][Br]) concentrations, absorption temperatures, and CO2 content in order to optimize operational conditions in our study. Meanwhile, the effects of regeneration temperature, regeneration time, and regeneration circles on the regeneration efficiency of CO2 saturated [Aemim][Br] solution were discussed, respectively. On the basis of these experiments, the kinetic data (i.e., in terms of the pseudo-first-order rate constant (kov), the second-order reaction rate constant (k2) and heat of CO2 absorption was calculated at 303 K as [Aemim][Br] concentration varied from 0.1 to 2.0 mol·L–1. The result showed that the process of CO2 absorption was a fast pseudo-first-order reaction regime. According to the kinetic data at 293–323 K, the activation energy of reaction was calculated by the Arrhenius equation, and the second-order reaction rate constant can be expressed as follows: k2 = 1.9...

Process optimization of spent catalyst regeneration under microwave and ultrasonic spray-assisted

In this work, the activated carbon loaded with zinc acetate dihydrate and used for catalyst in the polyvinyl alcohol and adhesive production process, was regenerated by microwave heating under ultrasonic spray atmosphere to recover the adsorption capacity of the spent catalyst. The effects of regeneration temperature, regeneration time and water mist flow rate on the adsorption ability of methylene blue (MB) and yield of activated carbon were researched systematically. The experiment results indicated that a promising adsorption capability via ultrasonic spray regeneration was developed for the spent catalyst, corresponding to Brunauer-Emmett-Teller (BET) surface area of 1263m2/g and total pore volume of 1.28mL/g under optimum conditions. The spent catalyst was also regenerated under the CO2 and N2 atmosphere, which indicated that the better pore structure was obtained under ultrasonic spray conditions. The physico-chemical properties of the activated carbon were measured by N2 adsorption, Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). The results showed that the chemical groups of activated carbons changed after regeneration and before and the spent catalyst can be regenerated commendably by microwave and ultrasonic spray-assisted.

In Situ Preparation and Regeneration Behaviors of Zinc Oxide/Red Clay Desulfurization Sorbents

High-temperature gas desulfurization is an efficient and environmentally friendly process for syngas cleanup. The present study investigated the in situ preparation of a zinc oxide/red clay desulfurization sorbent and its desulfurization–regeneration behavior in O2/N2 atmospheres. The effects of regeneration temperature, space velocity, and O2 concentration on the regeneration behaviors of ZnO/red clay sorbents were also investigated. The surface and structural properties of the sorbents before and after regeneration were characterized by thermogravimetric–differential scanning calorimetry, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, elemental mapping, and N2 adsorption–desorption analyses. According to the results, the highest regeneration rate was achieved under the conditions of 6 vol % O2 and a space velocity of 3000 h–1 at 650 °C. After four cycles of desulfurization–regeneration experiments, the breakthrough time of the regenerated sorbents reduced by 18.7% and...

NOx abatement from stationary emission sources by photo-assisted SCR: Lab-scale to pilot-scale studies

In developing a higher activity for NOx abatement from stationary emission sources, photo-assisted selective catalytic reduction (photo-SCR) was systematically investigated over TiO2 supported on a spherical α-Al2O3/γ-Al2O3. The formation of NO2 was virtually suppressed in the reaction temperature range of 110–200°C. The NOx removal efficiencies of TiO2/γ-Al2O3 photocatalyst at 120°C for real flue gas (in pilot-scale photoreactor) and simulated flue gas (in lab-scale photoreactor) were 68–75% and 43.5%, respectively, in the presence of reducing reagent (C4H10). SEM and XPS techniques revealed that sulfur temporarily occupied the active sites of the photocatalyst, causing deactivation. Spent TiO2/γ-Al2O3 photocatalyst was regenerated via desulfurization by either air or hydrogen at 400–500°C. The effects of regeneration temperature and regeneration time on the photocatalytic activity are methodically investigated, demonstrating that using hydrogen at 500°C in 1h could completely regenerate the spent photocatalyst.

Effect of regeneration temperature on adsorption equilibria and mass diffusivity of zeolite 13x-water pair

The adsorption equilibrium and mass diffusivity of zeolite 13X-water pair for different adsorption and regeneration temperatures were determined by a homemade volumetric system. The isotherms of the zeolite 13X-water pair were obtained by collecting pressure versus time data and applying ideal gas law. The effective diffusivity of the pair was calculated by using long term analytical solution of mass diffusivity based on Fick's law.The experimental study showed that the adsorption capacity of zeolite 13X-water pair was 23% (kg/kg), 21% (kg/kg) and 19% (kg/kg) when the adsorption temperature was 35, 45 and 60 °C respectively for the desorption temperature of 90 °C. Furthermore, the adsorption capacity increased from 22% (kg/kg) to 24% (kg/kg) when the desorption temperature was increased from 90 °C to 150 °C. It was observed that the present adsorption equilibrium results were compatible with the reported results in the literature.The mass diffusivity of the pair was found in the range of 4 × 10−9–6 × 10−8 m2/s for the long time period when the initial adsorptive pressure was 2000 Pa. The effective mass diffusivity depends on concentration and it was decreased with increasing adsorbate concentration.

Reversibility Studies of Clay Hydration Degree in its Natural and Composite Condition

In this work, the regeneration of desiccant compounds materials was studied after of its adsorption capacity. Also, reuse of the materials was evaluated after progressive regenerations. For this, the effect of regeneration temperature on adsorption capacity of the desiccant compounds materials was analyzed. For the tests adsorption of water a certain amount of dry sample was placed in a desiccator at 98% RH and 298K, until reach the time of equilibrium, in which the final weight was recorded. In order to check the reversibility of the process re-adsorption studies were performed with water. To do this, before starting the second adsorption cycle, the same portion of sample was dried again to release the adsorbed water (drying temperatures: 343K and 373K). Later was proceeded similarly to first adsorption cycle. After to this procedure was reiterated 5 times the test results showed no significant decrease in the efficiency of the material when the samples were regenerated at 373K. In this way, was possible to maintain approximately constant the hygroscopic characteristics of the material. From the results it was determined that the optimum temperature of drying for the regeneration process is to the corresponding to 373K since at this temperature the rate of desorption of water is facilitated, which allows to adapt the material in order to initiate an new cycle, being in evidence a good behavior of the material in reversibility

Deactivation of supported skeletal Ni catalyst and effect of regeneration temperature on its catalytic performance

Deactivation and regeneration of supported skeletal Ni catalyst applied to hydrogenation of indene and styrene in fixed-bed reactor were investigated. The significant aggregation of skeletal Ni and formation of coke precursors were the main reasons for deactivation of catalyst. Furthermore, TG-DTA, XRD, SEM, BET and H2-TPR were utilized to characterize the regenerated catalysts and calcining the spent catalysts in air at 550°C for 3h and then reducing in H2 at 450°C for 3h under 240h−1 (GHSV) could recover its activity according to hydrogenation evaluation results.

Direct CO2 capture from ambient air using K2CO3/Y2O3 composite sorbent

Carbonate–bicarbonate looping was tested for direct CO2 capture from air using a composite sorbent K2CO3/Y2O3. The phase composition, the porous structure and the texture of the composite sorbent were characterized by means of X-ray diffraction, mercury intrusion and scanning electron microscopy methods. The thermal properties of the sorbent were additionally studied by X-ray diffraction in situ and thermogravimetry methods. CO2 absorption from air and desorption experiments were performed in a continuous-flow system. The effect of regeneration temperature on CO2 uptake was investigated. It was shown that CO2 absorption uptake from air is about 28mg (CO2)/g in temperature swing absorption cycles within regeneration temperature range of 150–250°C. However, the increase of the regeneration temperature up to 300°C results in gradual decrease of the absorption uptake down to 10mg (CO2)/g. The XRD pattern of the cycled sample contains a set of reflections that cannot be assigned to any known potassium- or yttrium-containing crystalline phase. The new phase, which is thermally stable up to 460°C, accumulates potassium ions and is, probably, responsible for the sorbent capacity decay.

Experimental investigation on a one-rotor two-stage desiccant cooling/heating system driven by solar air collectors

A solar driven one-rotor two-stage desiccant co[oling/heating system is experimentally investigated. It consists primarily of a 5 kW desiccant cooling system and 15 m2 of solar air collectors. The desiccant cooling/heating system uses solar thermal energy to regenerate desiccant wheel in summer, and to produce hot air for space heating in winter. In summer, the outlet temperature of solar air collectors is about 60–100 °C. For the solar driven one-rotor two-stage desiccant cooling system, the moisture removal can reach 8–9 g/kg and supply air condition is about 22 °C and 60% RH. Experimental results indicated that the average thermal COP in cooling cycle is 0.95 in hot and humid climate conditions. The solar COP of system is about 0.45 when thermal efficiency of collector is 50%. This suggested that the system could convert more than 40% of the received solar radiant intensity to cooling power in sunny days. In addition, the effect of regeneration temperature on the system performance is studied. It was found that average of temperature difference between ambient and room can reach 13 °C for space heating in winter. Coupled with desiccant cooling system, solar air collectors can realize year-round running.