Monthly Archives: September 2023

Computational Fluid Dynamics Simulation of a Membrane Contactor for CO2 Separation: Two Types of Membrane Evaluation

Posted on 20 September 2023 by

Two different types of hollow-fiber membrane contactors were applied for separation of CO₂ from a gas stream using monoethanolamine absorbent, followed by numerical investigation. A model was proposed by solving velocity and mass transfer equations using Comsol software which was validated by experimental data. The effect of different parameters on CO₂ absorption was investigated.

Abstract

Two different types of hollow-fiber membrane contactors were used for CO₂ separation from the gas stream with monoethanolamine (MEA) absorbent and numerically investigated. After the model validation with experimental data, CO₂ removal efficiency, MEA concentration, and pressure drop variation were examined under different conditions by variation of some effective parameters such as gas stream velocity, absorption solution velocity, membrane porosity, and membrane tortuosity. Membrane tortuosity and porosity enhancement led to light decrease and light increase in CO₂ removal efficiency, respectively, but gas stream velocity enhancement significantly reduced the CO₂ removal efficiency.

Editorial Board: Chem. Eng. Technol. 10/2023

Posted on 20 September 2023 by Wiley: Chemical Engineering & Technology: Table of Contents

Chemical Engineering &Technology, Volume 46, Issue 10, Page 1980-1980, October 2023.

Effect of Mg/Al Oxides Supports on CaO Sorbents Prepared by Wet‐Mixing Synthesis for CO2 Capture

Posted on 20 September 2023 by nXiaolei Qi, nCong Luo, nHuizhe Wu, nGuang Wang, nTong Luon

Calcium looping sorbents incorporated with MgO, Ca₃Al₂O₆, and MgAl₂O₄ supports were prepared by wet-mixing synthesis and analyzed for their CO₂ capture performances during the 30 cycles of carbonation/calcination reactions. At a 7:3 mass ratio of CaO to support oxides, the MgAl₂O₄ mixed support showed the best CO₂ capture performance.

Abstract

Calcium looping is one of the effective methods for post-combustion CO₂ capture. A key issue is choosing the appropriate supports to synthesize effective calcium-based sorbents. In this study, calcium looping sorbents incorporated with MgO, Ca₃Al₂O₆, and MgAl₂O₄ supports were prepared by wet-mixing synthesis. Characterizations were made to determine the cyclic CO₂ capture capacity, crystalline structure, porosity, and morphological changes of the sorbents over multiple cycles. The results showed that, at the mass ratio of CaO to support oxides of 7:3, the MgAl₂O₄ mixed support showed better CO₂ capture performance than the MgO and Ca₃Al₂O₆ supports. Moreover, the sorbent showed a porous and fluffy microstructure with a high specific surface area, making it a suitable candidate for cyclic CO₂ capture.

Positioning a Measurement System for Determining the Mixing Quality in Biogas Digesters

Posted on 20 September 2023 by nBernhard Huber, nGeorg Johann Krebs, nLingga Aksara Putra, nMatthias Gaderern

Proposals for positioning local flow speed sensors around the circumference of a vertical biogas digester to monitor the mixing process are provided. The installation locations are selected based on a high correlation between flow velocity at the point of installation and a corresponding global mixing parameter. This approach is demonstrated for three different types of agitators.

Abstract

Mixing quality in agricultural biogas plants is crucial for nutrition supply to the microorganisms and needs to be ensured by an energy-efficient mixing strategy. Various approaches have been proposed to determine the mixing quality in biogas digesters. Among them are magnetic-inductive or force sensors brought into vertical digesters through the concrete wall. This article presents an approach to locating these sensors effectively around the circumference of the digester to avoid positioning in dead zones and maximize information quality regarding flow and mixing behavior. Particle image velocimetry is used to measure flow fields in a transparent model digester. Finally, optimum measurement locations considering three widely used agitator geometries are suggested.

Properties and Phase Behavior of Water‐Tween‐Kerosene Microemulsions and Prediction of Their Viscosity

Posted on 20 September 2023 by nMonireh Zolfaghari, nMasoud Nasiri, nAli Haghighi Asln

Water-Tween-kerosene microemulsions were prepared by a titration method and characterized by droplet size, electrical conductivity, and viscosity measurements. Water-in-oil, oil-in-water, and bicontinuous Winsor IV microemulsions were obtained. A new equation to predict microemulsion viscosity as a function of the ratio of the dispersed-phase fraction to surfactant fraction is proposed.

Abstract

Microemulsion systems are of interest to researchers due to their low energy requirements and thermodynamic stability in a wide range of applications, including enhanced oil recovery, gas absorption, drug delivery, and chemical reaction environments. In this research, the viscosity of microemulsions was characterized and then predicted. Tween 20 and Tween 80 were used as surfactants and n-butanol as co-surfactant. Different types of prepared Winsor microemulsions were described using the phase diagram and then were evaluated regarding their viscosity, particle size, and electrical conductivity. The mean droplet size and viscosity of the microemulsion were 8–200 nm and 10.4–39.1 cp, respectively. Finally, a new equation is suggested to predict microemulsion viscosity as a function of the ratio of the dispersed phase fraction to the surfactant fraction.

Sulfur Transformation during Coal Pyrolysis with Char Heat Carrier

Posted on 20 September 2023 by nQinhui Wang, nChengdong Ying, nRuiyue Zhang, nJianmeng Cenn

Based on a realized coal polygeneration technology, the effects of temperature, char heat carrier (CHC)/coal mass ratio, and CHC production temperature on sulfur transformation during coal pyrolysis with char as heat carrier were evaluated in a fluidized-bed reactor. The sulfur content in three-phase pyrolysis products was determined, including gaseous sulfur and the variation of sulfur forms in the mixed-char.

Abstract

To investigate sulfur transformation during coal pyrolysis with char heat carrier (CHC), the effects of temperature, CHC/coal, and CHC production temperature were explored in a fluidized bed. The yield rates of sulfur in H₂S () and Y _COS elevated with temperature. and Y _char-S decreased, and temperature showed no significant effect on Y _tar-S. CHC inhibited sulfur transformation to the gas phase. More H₂S and COS were fixed in mixed-char in form of CaS by CHC, resulting in the increase of Y _char-S. CHC was favorable for CH₃SH decomposition. The inhibitory effect was enhanced with increasing CHC/coal. Higher production temperature inhibited the sulfur fixation capacity of CHC. CHC enhanced the decomposition of pyrite, organic sulfur, sulfate, and the yield of sulfide in mixed-char.

Supercritical Methanol and Ethanol Solubility Estimation by Using Molecular Dynamics Simulation

Posted on 20 September 2023 by nHojatollah Moradi, nHedayat Azizpour, nParissa Khadiv-Parsi, nReyhane Ghorbani Nian

The solubility of supercritical methanol and ethanol was studied by molecular dynamics simulation. Increasing the pressure and density improved the solubility parameter, while the solubility decreased with increasing temperature at constant pressure. The solubility of supercritical methanol is independent of the molecule count and improving the density enhances the methanol and ethanol solubility.

Abstract

Solubility plays a crucial role in arranging extraction operations. Among solvents, supercritical methanol and ethanol have distinct extraction applications; thus, investigating their solubility parameters is crucial. This study investigates the solubility parameters of supercritical methanol and ethanol using molecular dynamics simulation at variable temperatures and pressures. The predicted solubility parameters for the solvents match the theoretical data. In this case, the root mean square error values for supercritical methanol and sub-/supercritical ethanol were 0.6934 and 1.0643, respectively. To realize the electrostatic and van der Waals interactions, the Ewald and atom-based summation methods were used, respectively. Also, this study shows that improving the density linearly enhances the solubility.

Zr‐Based Metal‐Organic Framework UiO‐66/Ultem® 1000 Membranes for Effective CO2/H2 Separation

Posted on 20 September 2023 by

Mixed-matrix membranes (MMMs) with polyetherimide as a continuous polymeric matrix phase and UiO-66 nanofillers as dispersed inorganic phase were synthesized and tested for H₂/CO₂ gas separation. MMMs containing metal-organic framework nanoparticles revealed excellent H₂ permeability and H₂/CO₂ separation factor. A new pathway is offered for producing high-performance, eco-friendly, and cost-effective MMMs.

Abstract

Mixed-matrix membranes (MMMs) using UiO-66 nanofillers as dispersing inorganic phase and polyetherimide (PEI) as continuous polymeric matrix were synthesized. Different UiO-66 loadings of 10, 20, and 30 wt % were applied. The morphology and UiO-66 dispersion over the prepared MMMs were examined. Gas separation measurements were performed for H₂/CO₂ gas mixture to evaluate the influence of UiO-66 on the separation yield of resulting membranes. When compared with pristine PEI membranes, MMMs containing metal-organic framework (MOF) nanoparticles revealed superior H₂ permeability and H₂/CO₂ separation factor, e.g., maximum permeability values of 14.6 and 5.5 Barrer were observed for H₂ and CO₂ at a filler loading of 10 wt % and an applied pressure of 4.0 bar.

Modeling and Simulation of a Zeolite Heat Storage with Binderless Zeolites

Posted on 20 September 2023 by nStefan Rönsch, nJohanna Eichler, nStefan Schmidtn

To support the development of zeolite heat storage systems in the future, in this work, a simulation model was developed and validated with help of a laboratory plant. The model was especially adapted to binderless zeolites of type NaY as heat storage material.

Abstract

Zeolite heat storages are one measure to contribute to the German Climate Change Act and reduce greenhouse gas emissions in the heating sector. However, due to the challenging process engineering, those storages did not reach a commercial breakthrough yet. To overcome this obstacle, intensive process simulation work is required. Thereby, the simulation models have to pay attention to recent innovations regarding the zeolite synthesis. One of those innovations is the preparation of binderless zeolites. Behind this background, it was achieved by the present work to develop and validate a simulation model for zeolite-based heat storage processes using binderless zeolites of type NaY.

Particle Size Distribution Model Fitting and Goodness‐of‐Fit Evaluation

Posted on 20 September 2023 by

Six mathematical models were selected for the fitting and regression of the particle size distribution (PSD) of (α,Z)-2-amino-α-(methoxyimino)-4-thiazole-ethanethioic acid S-2-benzothiazolyl ester (MAEM). The goodness-of-fit was evaluated by comparing the evaluation indexes. Selected models were compared for the PSD of MAEM produced under two different stirring speeds. FBRM monitored the particle number trends on a lab scale.

Abstract

Six mathematical models were selected for the fitting and regression of the particle size distribution (PSD) of (α,Z)-2-amino-α-(methoxyimino)-4-thiazole-ethanethioic acid S-2-benzothiazolyl ester (MAEM). The goodness-of-fit was evaluated by comparing the evaluation indexes such as R ², Akaike's information criterion (AIC), and root mean square error (RMSE). The top three selected models were further applied and compared for the PSD of MAEM produced under two different stirring speeds with distinct differences in regression coefficients. In addition, FBRM monitored the particle number trends on a lab scale under these stirring speeds. Finally, a feasible reaction mechanism was presented in which the dissolution of reactants was the rate-controlling step which could explain the significant influence on stirring speed.