Fixed Bed Method Research Articles

The amine-functionalized alumina captures CO2 directly from the ambient air in the rotating adsorption bed

Global warming presents formidable challenges, prompting the exploration of Direct Air Capture (DAC) as a promising solution. This study employed the ultrasonic impregnation method to load polyethyleneimine (PEI) onto cost-effective millimeter-sized spherical γ-Al2O3 microspheres, thereby preparing an efficient amine-modified adsorbent. Characterization reveals a uniform dispersion of PEI, resulting in an adsorbent with an effective pore structure, enhancing CO2 diffusion. The adsorption experiment combines DAC with high gravity technology, best conditions at a PEI load of 16.37%, high gravity factor of 2.67, and gas flow rate of 30 L/min. Under these conditions, an impressive adsorption capacity of 41.75 mg/g was achieved, marking an increase of 12.11 mg/g compared to the traditional fixed-bed method. The amine efficiency also reaches 0.25. The Freundlich model outperforms the Langmuir model in fitting isotherm curves, suggesting that the experimental data align with the characteristics of a heterogeneous surface and multilayer adsorption. The fitting results of kinetic models further show that RAB's adsorption rate constant has a significantly better fitting value compared to traditional fixed bed methods. The research provides valuable insights for the application and development of DAC technology, enabling new possibilities for future carbon capture and emission reduction efforts.

Numerical Simulation of Downdraft Biomass Gasifier With Computational Fluid Dynamic

World energy demand has resulted in a surge in renewable energy needs. One of them is biomass. The gasification process takes place in a reactor called a gasifier, and the most effective way is to implement the Fixed Bed method on the downdraft gasifier. The process was executed in a downdraft gasifier because of the gas-making process without stopping the ignition and producing a small amount of tar. The biomass raw material used in this study is wood pellets because of their abundant availability in Indonesia. This research discussed numerical simulations for downdraft gasifier by utilizing wood pellet biomass as a raw material. The simulation technique is computational fluid dynamic with the DPM (Discrete Phase Model) because it can predict the experiment result details more precisely. The simulation results have shown that the convergence rate got better with the longer process iteration time. The simulation results were close to 100% in real-scale laboratory research results.

L-Ascorbic Acid-g-Polyaniline Mesoporous Silica Nanocomposite for Efficient Removal of Crystal Violet: A Batch and Fixed Bed Breakthrough Studies.

In the present study, mesoporous silica nanoparticles (MSNs) synthesized through sol–gel process and calcined at 600 °C were further surface functionalized by a copolymer chain of L-ascorbic acid (AS) and polyaniline (PAni) by in situ free radical oxidative polymerization reaction. The surface modification of MSNs by AS-g-PAni was confirmed by using various analytical techniques, namely FTIR, XRD, SEM–EDX, TEM and AFM. The composition of AS-g-PAni@MS was found to be composed of C (52.53%), N (20.30%), O (25.69%) and Si (1.49%), with 26.42 nm as the particle size. Further, it was applied for the adsorption of crystal violet (CV) dye under batch, as well as fixed bed method. RSM–BBD was taken into consideration, to optimize the various operational parameters effecting the adsorption through batch method. To explore maximum efficiency of the material, it was further subjected to adsorption of CV under fixed bed method, using the variable bed heights of 3.7, 5.4 and 8.1 cm. Based on high value of regression coefficient (R2) and low value of RMSE given as (0.99, 0.02) for 3.7 cm, (0.99, 0.03), the breakthrough data were very well defined by the Thomas model, with optimum concurrence of stoichiometric adsorption capacity values. The external mass transfer equilibrium data were well fitted by the Langmuir model, with maximum monolayer adsorption capacity of 88.42 mg g−1 at 303 K, 92.51 mg g−1 at 313 K, 107.41 mg g−1 at 313 K and 113.25 mg g−1 at 333 K. The uptake of CV by AS-g-PAni@MS was well defined by pseudo second order model with rate constant K2 = 0.003 L mg–1 min–1 for 50 and 0.003 L mg–1 min–1 for 60 mg L–1 CV. The adsorption reaction was endothermic with enthalpy (ΔH) value of 3.62 KJ mol−1 and highly efficient for treatment of CV-contaminated water for more the five consecutive cycles.

Experiment and Mechanism Analysis of Desulfurization with a MgO-Based Desulfurizer Fixed Bed Method.

To reduce the cost of the current commercial desulfurization and eliminate effluents, the MgO-based desulfurizer fixed bed desulfurization tests were carried out in a dry environment. By means of X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, the absorption effects of the MgO-based desulfurizer on SO2 were thoroughly investigated. Physical and chemical analyses show that most of the SO2 diffused on the desulfurizer surface was oxidized into sulfate and some SO2 entered the inner hole and the microhole of the desulfurizer. The technology was applied to sintering flue gas and achieved 97% stable desulfurization at low temperatures, which indicates that the MgO-based desulfurizer has obvious industrial competitive advantages.

Fixed-bed gasification and pyrolysis of organic fraction of MSW blended with coal samples

Buildup of vast quantities of municipal solid waste (MSW) including refuse derived fuel, organic fraction around the urban areas has negative environmental consequences. Gasification and pyrolysis of municipal solid waste could be an attractive option to utilize or convert to a valuable product. This study investigates the thermochemical properties of refuse derived fuel (RDF), organic fraction of MSW (Org MSW) and coal samples. Along with proximate and elemental analysis, calorific values were provided for RDF, MSW organic fraction, and coal samples. This followed by the thermogravimetric analysis of the same samples. In addition, Org MSW MSW and coal samples were blended in a proportion of 0.5/0.5 and 0.25/0.75 and then thermally treated in horizontal tube furnace both under air and inert gases to investigate the pyrolysis and gasification processes. TGA tests revealed that volatile content from Org MSW and RDF begin to be emitted at temperatures above 180-200 °C. Org MSW and RDF lose all their volatile contents at 500 °C and 700 °C. Pyrolysis experiments revealed that below 500 °C mostly tars are formed from Org MSW. Organic MSW and coal 0.5/0.5 blends yielded higher methane concentrations than coal or MSW alone, reaching 35-37 % at 800 °C. It could be concluded that both fixed bed and thermogravimetric method analysis have provided a good result to investigate the gasification and pyrolysis processes.

Batch and Fixed Bed Comparative Study on the Dye Bio-Sorption Properties of Cedrus Libani (Elizabeth Leaf) on Methylene Blue, Bismarck Brown Y and Indigo Dye

The adsorption properties of Cedrus libani (Elizabeth leaf) on methylene blue dye, Bismarck brown Y dye and indigo dye was studied using both the batch process and fixed bed methods. This was done in order to compare the effectiveness of each of the methods over each other in the adsorption process. The biomass was characterized using the scanning electron microscope (SEM) as well as the Fourier Transform Infrared Spectroscope (FTIR) before and after adsorption in order to determine the functional groups responsible for the adsorption. The amount of dye adsorbed per unit mass of the biomass (q e ) was calculated and found to be dependent on contact time, pH, biomass dose, biomass particle size, dye concentration, dissolved sodium and calcium salts and temperature. Optimal pH of 2 was determined for the adsorption of Bismarck brown Y dye and indigo dye while pH of 4 was determined for methylene blue dye. The q e value for the fixed bed adsorption was determined to be 12.98mg/g compared to the 11.28mg/g for the batch process using methylene blue dye. This indicates a better adsorption in the fixed bed technique over the batch process. However, the q e values fluctuated using the Bismarck brown Y and indigo dyes. Generally, the results show a better adsorption in the fixed bed technique over the batch process. Indigo dye was found to be the least adsorbed, while methylene blue dye was the most adsorbed. The adsorption pattern was fitted for Langmuir adsorption isotherm model.

Adsorption equilibria of rhodium acetylacetonate with MCM-41, MSU-H, and HMS silica substrates in supercritical carbon dioxide for preparing catalytic mesoporous materials

Adsorption isotherms of rhodium(III) acetylacetonate (Rh(acac)3) in supercritical carbon dioxide (scCO2) with methanol co-solvent for three types of mesoporous silica (MCM-41, MSU-H, and HMS) at 313–353K and at 15.0MPa were measured using a fixed bed method. The measured adsorption equilibria varied among the adsorbent substrates and depended on the specific surface area and pore structure of the adsorbents. The amount of adsorbed Rh(acac)3 increased with increasing temperature owing to strong effects of the CO2 density. Fitting parameters determined from correlation of the data with the Dubinin-Astakhov (DA) equation demonstrated that the interaction of the precursor for the adsorbents, CO2 density and pore structure of adsorbents were dominant factors in the adsorption equilibria of metal precursors in scCO2. The impregnation of Rh on the silica supports by a batch method in scCO2 could be characterized by the DA equation for which Eprec showed correlation with impregnated Rh particle size and W0,prec showed correlation with Rh loading amount. The DA equation is useful for characterizing adsorption equilibria in mesoporous materials with scCO2 systems and allows estimation of conditions required for impregnating metals into mesoporous silica substrates.

Adsorption equilibria of volatile organic compounds on various adsorbents in supercritical carbon dioxide: Measurement and analysis by the Dubinin-Astakhov equation

Adsorption equilibria of VOCs (toluene, acetone, n-hexane) on various adsorbents (activated carbon, mesoporous carbon, mesoporous silica, and zeolite) in supercritical carbon dioxide were studied. The amount of adsorbed VOC on the adsorbents in supercritical carbon dioxide was measured by a fixed bed method at temperatures from 313 to 353 K and pressures from 4.2 to 15.0 MPa. The measured adsorption equilibria were strongly dependent on VOC species, adsorbent properties and CO2 density, and could be correlated by using the DA (Dubinin-Astakhov) equation. Two fitting parameters determined with the equation provided quantitative information on adsorption phenomena of VOCs on the adsorbents in considerations of the VOCs affinity to the adsorbents, CO2 density, and properties of the adsorbents.

Measurement and prediction of desorption behavior of five volatile organic compounds (acetone, n-hexane, methanol, toluene, and n-decane) from activated carbon for supercritical carbon dioxide regeneration

Measurement and prediction of desorption behavior of five volatile organic compounds (VOCs) (acetone, n-hexane, methanol, toluene, and n-decane) from activated carbon by using supercritical carbon dioxide regeneration were studied. Measurements of the desorption behavior were performed with a fixed bed method at temperatures from 313 to 353K and pressures from 10.0 to 15.0MPa. The measured desorption rates varied greatly for each VOC, which could be attributed to differences in two properties, affinity of VOCs for activated carbon and the volatility of VOCs. The measured desorption rates increased with increasing pressure and decreasing temperature, which could be explained by increasing CO2 density. A kinetic model was applied to correlate the desorption behavior. The model demonstrated satisfactory correlations of the desorption behavior with only one fitting parameter. Generalization of the fitting parameter to predict the desorption behavior were also investigated. The proposed prediction model could roughly represent the desorption behavior of VOCs over a wide range of supercritical carbon dioxide conditions.

VOCs (acetone, toluene, and n-hexane) adsorption equilibria on mesoporous silica (MCM-41) over a wide range of supercritical carbon dioxide conditions: Experimental and theoretical approach by the Dubinin–Astakhov equation

Adsorption equilibria of three volatile organic compounds (VOCs) (acetone, toluene, and n-hexane) on mesoporous silica (MCM-41) were investigated over a wide range of supercritical and pressurized carbon dioxide conditions. Measurements of the adsorption equilibria were performed with a fixed bed method at temperatures from 313 to 353K and pressures from 4.2 to 15.0MPa. The measured adsorption equilibria strongly depended on properties of VOCs, which could be explained by the affinity between the adsorbent and adsorbate. The Dubinin–Astakhov equation demonstrated satisfactory correlations of the adsorption equilibria within 10% of average relative deviation. Two fitting parameters determined with the equation provided quantitative information on adsorption phenomena in considerations of the VOCs affinity to the adsorbents, CO2 density, and pore structure of adsorbents.

H<sub>2</sub>O<sub>2</sub> production technology with slurry reactor

Hydrogen peroxide is mainly produced by anthraquinone method in the world. The research progress and the development of anthraquinone method is summarized. The production technology using slurry reactor developed by Sinopec Research Institute of Petroleum Processing (RIPP) is briefly introduced. In China, the replacing of fixed bed method by fluidized bed method is a developing trend and the major breakthrough for the production technology of hydrogen peroxide.

A kinetic study of organic compounds (acetone, toluene, n-hexane and n-decane) adsorption behavior on activated carbon under supercritical carbon dioxide conditions at temperature from 313 to 353 K and at pressure from 4.2 to 15.0 MPa

Adsorption kinetics of four volatile organic compounds (VOCs) (acetone, toluene, n-hexane and n-decane) on activated carbon under supercritical carbon dioxide (scCO2) conditions was studied. Breakthrough curve measurements of VOCs in scCO2 were performed with a fixed bed method for activated carbon (ca. mean particles diameter: 100μm, specific surface area: 1300m2/g and mean pore diameter: 0.687nm, respectively). The measured breakthrough curves could be correlated with a kinetic model by using only one fitting parameter (effective diffusion coefficient in pore) within 10% of average relative deviation. The determined effective diffusion coefficient decreased with decreasing temperatures and increasing pressures at all conditions. Additionally, a generalized model of the determined effective diffusion coefficients was developed, and the proposed model could satisfactorily describe temperature and pressure dependence at all VOCs conditions.

Temperature-Swing Adsorption Process of Au(III) Ions Using Poly(N-isopropylacrylamide) Hydrogel Beads Prepared by Sedimentation Polymerization Combined with Two-Fluid Atomization

The temperature-swing adsorption (TSA) process—the control of the adsorption and desorption behavior of metal ions by changing the temperature—improves metal separation to reduce the consumption of chemicals and save energy. The TSA of Au(III) ions onto the thermosensitive poly(N-isopropylacrylamide) hydrogel (NIPA hydrogel) was successfully conducted in our previous study. This study focuses on a continuous process for the TSA of Au(III) ions from a solution onto NIPA hydrogel beads using the fixed bed method. Monodisperse hydrogel beads, which were approximately 1 mm in diameter, were prepared using a production method combining sedimentation polymerization and two-fluid atomization. The Au(III) adsorption properties on hydrogel beads, such as its isotherms and kinetics, were evaluated and analyzed. The continuous TSA featuring adsorption at 34 °C and desorption at 10 °C was demonstrated, and the associated breakthrough curve was successfully predicted by a mathematical analysis.

Measurements and Dubinin–Astakhov correlation of adsorption equilibria of toluene, acetone, n-hexane, n-decane and methanol solutes in supercritical carbon dioxide on activated carbon at temperature from 313 to 353 K and at pressure from 4.2 to 15.0 MPa

Adsorption equilibria of five volatile organic compounds (VOCs) (toluene, acetone, n-hexane, n-decane and methanol) on activated carbon in supercritical carbon dioxide were studied. Measurements were performed with a fixed bed method for activated carbon fine particles (ca. 74–147μm diameter), a specific surface area at 1300m2/g and a mean pore diameter, micropore volume of 0.687nm and 0.441cm3/g, respectively. Characteristic adsorption isotherms varied greatly for each VOC that can be attributed to differences in two interactions, VOC and activated carbon, VOC and supercritical carbon dioxide in the bulk phase, respectively. Adsorption amount of each VOC increased with increasing temperature and decreasing pressure. Adsorption isotherm equilibria could be correlated with the Dubinin–Astakhov equation using two parameters within 6.5% of average relative deviation. The parameters of the Dubinin–Astakhov equation were found to be a function of the chemical species, carbon dioxide density and VOC molar volume. These results indicate a possibility of developing a predictive model for the adsorption equilibria.

Adsorption, Co-adsorption, and Reactions of Sulfur Compounds, Aromatics, Olefins over Ce-Exchanged Y Zeolite

Adsorption, coadsorption, and reactions of sulfur compounds, olefins, and aromatics over Ce-exchanged Y zeolite (CeY) have been studied by N2 adsorption, intelligent gravimetric analyzers (IGA), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FT-IR), frequency response (FR) techniques, and batch and fixed bed methods. The coadsorption of olefins can effectively contribute to the alkylation and oligomerization reactions of thiophene and further decrease the desulfurization performance of CeY. The influence of aromatics on the desulfurization performance of CeY can be related to the competitive adsorption/diffusion processes between sulfur compounds and aromatics. The diffusion process is the rate-controlling step for benzene, and the sorption process is the rate-controlling step for thiophene. Thiophene molecules can be preferentially adsorbed onto the Lewis acid sites by direct interaction between sulfur on sulfur compounds and the Ce ion (S–M bond formation) or π-complexation, but the S–M bond interactions play a more dominant role than π-complexation in the CeY/sulfur compounds system.

PHYSICAL CHARACTERISTICS OF FLY ASH NANO PARTICLES AS BACKFILL ON THE RADIOACTIVE WASTE REPOSITORY

Characterization of fly ash nano particles as backfilled material candidate in the radioactive waste repository has been done. The objective of this research is to determine the permeability (K) and migration rate (Vr) of uranium in the backfilled material of fly ash, zeolite, and zeolite + fly ash mixtures. The experiment was carried out by the fixed bed method in a column contains fly ash, or zeolite, or zeolite+fly ash mixtures. It was filled with the saturated water and was flown by uranyl nitrate solution of 500 ppm as the simulated uranium. The uranium effluents was sampled in every 15 minutes and it was analyzed using spectrometer. The concentration of which represented as Ct and by using concentration profile of Co/Ct, then Vr of uranium in the backfilled material can be determined. The experiment result showed that ≤ 38 mm of fly ash particles sizes could improve the characteristic feature of 196 mm of zeolite sizes as backfilled material with the decreasing permeability values from Kzeolite = 4.06x10-3 cm/s to Kzeolite+fly ash = 5.00x10-5 cm/s and the decreasing of the migration rate from Vr zeolite = 1.65x10-4 cm/s to Vr zeolite+fly ash = 2.91x10-6 cm/second. Keywords: fly ash, zeolite, backfill materials, uranium migration, radioactive waste repository

THE USE OF FLY ASH AND ZEOLITE MIXTURE AS BACKFILL MATERIAL IN THE RADIOACTIVE WASTE REPOSITORY

An investigation of the contribution of fly ash in the fly ash-zeolite mixture as the backfill material on the shallow land burial of radioactive waste has been done. The experiment objective is to know the effect of zeolite particle size and fly ash-zeolite weight ratio on physical properties such as permeability (K) and dispersion characteristic such as effective dispersion coefficient (De) in the fly ash-zeolite form as backfill material. The experiment was carried out by the fixed bed method in the column filled by the fly ash-zeolite mixture with a fly ash-to-zeolite weight percent ratio of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 in the water saturated condition flown by uranyl nitrate solution at concentration (Co) of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, data effective dispersion coefficient (De) in the backfill material were determined. The experiment data showed that -400 mesh fly ash and -70+80 mesh zeolite on fly ash-to-zeolite with weight percent ratio of 40/60 with K = 5.00x10-5cm/second and De = 1.11.10-5 cm2/second can be used as backfill material. Keywords: backfill material, fly ash, radioactive waste, zeolite

DISPERSION AND SORPTION CHARACTERISTICS OF URANIUM IN THE ZEOLITE-QUARTZ MIXTURE AS BACKFILL MATERIAL IN THE RADIOACTIVE WASTE REPOSITORY

The experiment of sorption and dispersion characteristics of uranium in the zeolite-quartz mixture as candidate of raw material of backfill material in the radioactive waste repository has been performed. The objective is to know the effect of zeolite and quartz grain size on the zeolite-to-quartz weight ratio that gives porosity (ε), permeability (K), and dispersivity (α) of uranium in the zeolite-quartz mixture as backfill material. The experiment was carried out by fixed bed method in the column filled by the zeolite-quartz mixture with zeolite-to-quartz weight percent ratio of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 wt. % in the water saturated condition flowed by uranyl nitrate solution of 500 ppm concentration (Co) as uranium simulation which was leached from immobilized radioactive waste in the repository. The concentration of uranium in the effluents represented as Ct were analyzed by spectrophotometer Corning Colorimeter 253 every 15 minutes, then using Co and Ct uranium dispersivity (α) in the backfill material was determined. The experiment data shown that 0.196 mm particle size of zeolite and 0.116 mm particle size of quartz on the zeolite-to-quartz weight ratio of 60/40 wt. % with ε = 0.678, K = 3.345x10-4 cm/second, and α = 0.759 cm can be proposed as candidate of raw material of backfill material in the radioactive waste repository. Keywords: backfill material, quartz, radioactive waste, zeolite

BENTONITE-QUARTZ SAND AS THE BACKFILL MATERIALS ON THE RADIOACTIVE WASTE REPOSITORY

An investigation of the contribution of quartz sand in the bentonite mixture as the backfill materials on the shallow land burial of radioactive waste has been done. The experiment objective is to determine the effect of quartz sand in a bentonite mixture with bentonite particle sizes of -20+40, -40+60, and -60+80 mesh on the retardation factor and the uranium dispersion in the simulation of uranium migration in the backfill materials. The experiment was carried out by the fixed bed method in the column filled by the bentonite mixture with a bentonite-to-quartz sand weight percent ratio of 0/100, 25/75, 50/50, 75/25, and 100/0 on the water saturated condition flown by uranyl nitrate solution at concentration (Co) of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, retardation factor (R) and dispersivity () were determined. The experiment data showed that the bentonite of -60+80 mesh and the quartz sand of -20+40 mesh on bentonite-to-quartz sand with weight percent ratio of 50/50 gave the highest retardation factor and dispersivity of 18.37 and 0.0363 cm, respectively. Keywords: bentonite, quartz sand, backfill materials, radioactive waste

Hydrogenation to products with IV below 1

AbstractThe hydrogenation of fatty acids (FA) or fatty acid methyl esters (FAME) is a fundamental process to manufacture basic oleochemicals, like stabilizers and surfactants. These kinds of oleochemicals are used in downstream processes, to obtain products which are easily bio‐degradable, non‐irritant to the skin, and equipped with other favourable characteristics. In principle the FA or FAME are hydrogenated in a reactor under pressure, higher temperature and in the presence of a metallic catalyst, such as nickel or palladium. The process can be controlled in a desired direction by appropriate choice of these parameters to get a product with different degrees of saturation, melting properties and colour. The commonly used process nowadays is a batch process. The hydrogenation reaction is carried out in a loop or stirred reactor, in the presence of a suspended catalyst. After the reaction the catalyst must be removed from the product by an elaborate and time‐consuming filtration. This leads to higher consumption of catalyst. Another concern is that Ni‐soaps can be formed during the process leading to deactivation of catalyst and the presence of nickel in the final product. Therefore the fixed bed method was developed to eliminate these disadvantages. A pilot plant was constructed in which the catalyst is fixed on a carrier matrix and filled into the reactor and a test run was carried out with FA from tallow and FAME from palm oil. The iodine value of < 0.1 in hydrogenated FAME was achieved as required by the industry for the production of surfactants. In the fixed bed hydrogenation for ME nickel catalyst and for FA a palladium catalyst is used. Furthermore catalyst is reused, its consumption is reduced and the formation of byproducts is minimized. The process is characterized by a high reliability, feed flexibility, easy control and high yield.