Category Archives: Chemical Engineering & Technology

Continuous Generation of Gas‐Water Slugs with Improved Size Uniformity at a Tunable Scale

Posted on 20 September 2023 by nMingyao Mou, nLoren dela Rosa, nJethrine H. Mugumya, nMo Jiangn

The slug flow tubular reactor is a promising continuous manufacturing or next-generation approach that can address problems in the traditional tank-based batch reactor, such as batch-to-batch variation and scale-up difficulties. The study shows how to control the parameters of a slug flow reactor and how to scale up a process without changing the reactor itself.

Abstract

Slug flow has received increased interest due to the slugs serving as individual microreactors for enhanced process efficiency and product quality. In this study, slugs were continuously generated in various scales and sizes, with slug size uniformity studied by in-line imaging. Different strategies of gas flow control and slug scale-up were evaluated regarding the slug size distribution. With modified gas flow control, the slug uniformity was improved significantly. Slug flow can also be scaled up without sacrificing slug size uniformity, either by increasing the reservoir feeding volume or the flow rate. The type of gas used (air and nitrogen) to generate slugs does not affect the slug size uniformity. A narrow slug size distribution can improve the particle size distribution and, hence, lead to better product quality.

Thermodynamics of Textile Dyes Partitioning in Alcohol‐Based Aqueous Two‐Phase Systems

Posted on 20 September 2023 by

Aqueous two-phase systems (ATPSs) have potential applications in the recovery of residual dyes in wastewater, which pose a threat to human health and the environment. This work determined the partition coefficients and thermodynamic transfer parameters of Remazol textile dyes in alcohol-salt-water ATPSs. It highlighted that ATPS is a promising route for removing dyes from contaminated wastewaters.

Abstract

The aim of this work was a complete thermodynamic study on the partitioning of Remazol Yellow l, Remazol Brilliant Blue, and Remazol Red dyes in isopropyl alcohol + sodium phosphate + water aqueous two-phase systems at different temperatures. The free energy change of transfer, enthalpy change of transfer, and entropy change of transfer were evaluated. The effects of the structure of the dye, tie line length, and temperature on the partitioning were studied. The results indicate that these aqueous two-phase systems have high capacity to extract the dyes from aqueous matrices to the organic phase of these systems and are an interesting alternative to effluent treatment process.

Environmental Impact Improvement of Chitosan‐Based Mixed‐Matrix Membranes Manufacture for CO2 Gas Separation by Life Cycle Assessment

Posted on 20 September 2023 by

Post-combustion technologies are essential to reduce CO₂ emissions. CO₂ separation from flue gases by membranes has advantages over other methods. Membranes must be robust, with a high CO₂ permeation flux and reduced environmental impact manufacture. Life cycle assessment is applied to compare environmental impacts of the membrane manufacture based on chitosan and fossil fuels with the same CO₂ permeation flux.

Abstract

The environmental impacts of the manufacture of chitosan (CS) and polymeric poly(1-trimethylsilyl-1-propyne) (PTMSP) mixed-matrix membranes (MMMs) for CO₂ separation by life cycle assessment (LCA) are compared. An ionic liquid of non-reported toxicity is used in CS membranes to enhance the mechanical strength, and different fillers are used to increase mechanical and functional properties: ETS-10, ZIF-8, HKUST-1, and Zeolite A. Results with the same CO₂ permeation flux indicate that ETS-10/IL-CS is the membrane manufacture with highest impacts due to its lower permeability. When comparing impacts with same permeation areas, the polymeric one is the membrane with highest impacts. Biopolymer and polymer manufacture are the components with highest contribution to the total environmental impacts of each membrane. To decrease all their impacts below fossil polymer membrane for the same CO₂ permeation flux, CS membranes permeabilities should be improved by a numerical factor of 1000, 100, and 2 for the ETS-10, ZIF-8, and HKUST-1/IL-CS MMMs, respectively.

Controllability and Energy‐Saving Ability of the Dividing‐Wall Column for Batch Distillation

Posted on 20 September 2023 by

The controllability and energy-saving ability of the dividing wall column for batch distillation (batch DWC) was proved. The performances of temperature control were slightly better than those of composition control. The batch DWC outperforms the other batch configurations in terms of distillation time and energy loss.

Abstract

The batch distillation is significant and flexible to separate liquid mixtures. However, it is usually energy intensive. The dividing-wall column (DWC) is a promising and practical energy-saving process intensification technology. The DWC for batch distillation (batch DWC) to separate benzene, toluene, and xylene mixtures was examined with composition and temperature control structures to verify its controllability. Besides, the batch DWC outperforms the conventional single-column batch distillation and middle-vessel batch distillation in terms of distillation time and energy consumption under the same conditions. In terms of more practical temperature control results, the batch DWC saves 63 % of energy compared with the conventional single-column batch distillation and 47 % of energy compared with the middle-vessel batch distillation.

Numerical Study on the Granular Flow and Heat Transfer of a Calcium Looping CO2 Capture System

Posted on 20 September 2023 by nShih-Hao Chou, nYi-Shun Chen, nShu-San Hsiau, nShang-Yu Liun

Calcium looping is a promising process for carbon dioxide removal. The flow and heat transfer processes of the granular sorbent in a calcium looping CO₂ capture system and the effects of the operating parameters on calcination efficiency and transport properties were studied. Both the rotation speed and the inclination angle significantly influence the dynamic properties of the granular matter.

Abstract

The calcium looping process has become a promising technology for reducing carbon dioxide emissions because of its lower energy consumption compared with other methods. A three-dimensional multifluid model based on the kinetic theory was employed to study the movement of granules in the calciner. The results demonstrated that an increase in the rotation speed and inclination angle of the calciner led to a decrease in the residence time of the particles. Simultaneously, the probability of the particles being heated was reduced. Insufficiently calcined particles reduce the carbon capture capacity in the next cycle; therefore, suitable operating conditions and mechanism designs are very important.

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.

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.

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.

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.

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.