Band 23, Heft 3

In this study, the wall effect of the reaction tube on the hydrodynamic behavior of a fluidized nanoparticle agglomerate is examined with varying fractal dimension and agglomerate-to-tube radius ratio at intermediate Reynolds numbers from 1 to 40. A radially varying permeability model is adopted to account for the porous, hierarchical and fractal structure nature of the fluidized nanoparticle agglomerates. Simulation results reveal that the wall forces more fluid to flow through the agglomerate, and a fluid velocity peak inside the agglomerate is observed in most cases. The fluid flow inside agglomerates is significantly affected by the Reynolds number and fractal dimension, nevertheless, the wall constrains the deformation of streamlines. The fluid passes through the agglomerate almost parallel to the wall, and the wake in the rear region of an agglomerate is depressed, with no flow separation observed. The wall effect brings in additional drag for the agglomerate, and the drag coefficient decreases with the Reynolds number and increases with the radius ratio.

To enhance nylon-6,6 continuous polymerization process, the comprehensive process models under four existing industrial reactor strategies and two newly proposed reactor strategies are developed and partially validated by plant data. On the basis of controlling water vapor and hexamethylenediamine (HMDA) evaporation, the comparative evaluations are conducted for these reactor strategies. The DuPont tower reactor strategy implements HMDA reflux of distillation to achieve a closer ratio of amine end groups to carboxyl end groups (1:1), and further developed multi-stage reactor strategy can improve the utilization of recovered HMDA. The proposed new process intensification strategy, i.e., employing gradient pressure reduction along with tower reactor height, increases water volatilization by 27.2 % and HMDA volatilization by 0.6 %, thereby facilitating the growth of polymer chains. Compared to other strategies, the gradient pressure reduction strategy can better control over the polymerization reaction and improve adaptability to different residence time.

In this study, a novel top-side composite blowing technique is proposed to address the limitation of a large number of mixing dead zones in the near-wall zone of top-blown metallurgical reactors. The bubble behaviour and melt pool mixing characteristics in the multiphase flow reactor under this technique were systematically investigated by using the VOF method. The research findings indicate that top-blowing and side-blowing bubbles interact with each other, undergoing a series of dynamic processes including expansion, deformation, fragmentation, and fusion. These processes ultimately lead to the formation of a unique flow mixing pattern characterized by central depression and an undulating, rotating liquid surface. The flow pattern can be further divided into distinct zones: the surface zone, the top-blowing momentum zone, the momentum-interaction zone, the side-blowing momentum zone, and the low-speed perturbation zone. With the increase of the side blowing angle, the small-scale bubbles increase, and the gas-liquid contact surface area increases, which is conducive to the enhancement of the reaction rate. When the side blowing angle is 15° and the side blowing speed is 58 m/s, the wall shear pressure decreases by 6 % and 25.13 % compared with that of 40 m/s and 72 m/s, respectively. Under this operating condition, the gas content in the molten pool reaches its maximum, achieving efficient gas mixing of viscous fluids and extending the service life of the reactor. This study provides theoretical basis and enhanced mechanism guidance for the optimisation of top-side composite blowing technology.

The consumption of vegetables generates a lot of waste, allowing their use as biomass. biosorbent based on turnip leaves were prepared; they were processed in the raw state (TL) and activated with H 3 PO 4 (TLA), and then tested to remove the Crystal Violet dye CV from aqueous solutions. Adsorbents were characterized using (FTIR), (SEM), (XRD), (TGA) and pH PZC , revealing that the functional groups OH, C-H, C=O and C-O-C were mainly responsible for the adsorption of CV. Scanning electron microscope (SEM) imaging revealed cellulose fibers with a multicellular structure initially linked to lignin and hemicellulose, which dissociated after chemical treatment, XRD analysis confirmed the amorphous nature of the structure, attributed to the presence of lignin and hemicellulose. The kinetic study showed that the best suited models to describe the experimental data were the pseudo-second-order (PSO) model for TLA and TL. The analysis of the adsorption isotherms using different models showed that they followed the Sips isotherm with a maximum adsorption capacity (qmax) of 635.54 mg/g for TL and 621.76 mg/g for TLA. The optimal conditions were found to be an adsorbent mass of 20 mg, a temperature of 25 °C. and a concentration of 10 mg/L with respective contact times of 150 min for TL and 120 min for TLA, leading to elimination yields of 92.60 % and 97.56 %. The mechanism of adsorption of the CV dye using TL and TLA could be explained by electrostatic interactions between the negatively charged surface of TL and TLA and the positively charged group of the CV dye. A thermodynamic study was carried out on the process of adsorption of the CV dye from aqueous solutions using activated and raw turnip leaves which revealed that this process was exothermic and spontaneous due to the approximate values of ΔH (−25.26 for TL and −20.69 for TLA) and ΔG. The predictive capacity of the multi-component adsorption system was studied using a Support Vector Machine (SVM) model. Two SVM approaches were developed and compared. The first model involved the use of the SVM method with an integrated optimization algorithm, while the second model used a more recent and efficient method, the Dragonfly (DA) algorithm, in conjunction with the SVM method. The evaluation of the accuracy of the models was carried out using three commonly used statistical measures: the mean squared error (RMSE), the coefficient of determination (R2) and the correlation coefficient (R). The data included five important variables, from 136 observations: the weight of the turnip leaves (TL or TLA), the initial concentration (c 0  in mg/L), the dose of foliar waste (in mg/L), the time (in minutes) and the final concentration (Cf). The programming was carried out using the MATLAB software. The results demonstrated that the DA-SVM model optimized with an RBF-Gaussian kernel function had an excellent prediction ability, with an R2 of 0.997, an R of 0.998 and an RMSE of 1.0809.

This study explores the esterification of acetic acid with n -butanol using methanesulfonic acid (MSA) as a homogenous catalyst. The experiments were conducted in a batch reactor, kinetic study has been done using an ideal concentration-based model, and an activity-based model. The activity coefficients for species taking part in the reaction are estimated through the UNIFAC model. The effect of various operating variables including temperature (60–90 °C), reactant molar ratio of n -butanol to acetic acid (1–3), and catalyst loading of (0.5–1.5 wt%) on acetic acid conversion was investigated. Both the kinetic models are able to predict the conversion with high accuracy ( R 2  = 0.99). The conversion of acetic acid has been mapped in terms of electrochemical parameters using electrochemical impedance spectroscopy (EIS). A constant phase element (CPE) coupled with diffusion model has been used for ascertaining the impedance parameters. The impedance parameters obtained on fitting the equivalent circuit have been used for developing a fuzzy inference system (FIS) based on Takagi and Sugeno’s approach. The developed FIS exhibits a higher degree of accuracy in predicting the acetic acid conversion/reaction yield. The results obtained through the developed FIS indicated its use as a soft sensor in esterification industries.

Life can’t sustain without water. Sustainable development goal (SDG-6) emphasizes on access of suitable quality water to all. The amount of available freshwater on earth is very low and declining further. Human health, life quality and environment can be severely affected by the rising water scarcity. Desalination is the most widely adopted method to meet the global water demand. However, the adverse environmental impacts of existing desalination techniques necessitate the quest of sustainable methods. Solar distillation can be used for production of drinking water in a sustainable and economic manner. The current work evaluates and compares the performance of a small size single and a double slope solar still under similar climatic conditions. Both the stills are made of galvanized iron sheet and basin area is 0.36 m 2 . The productivity of single slope solar still (SSSS) and double slope solar still (DSSS) are found to be 2.58 L/m 2 and 3.19 L/m 2 respectively. The water yield of double slope solar still is observed to be 23.7 % higher than that of single slope solar still. Hence, the double slope solar still is observed to exhibit better performance.

The present study numerically assesses the influence of solid loading on the performance of gas-solid cyclones equipped with spiral guide vanes (SGVs) featuring 0.5 to 3 turns. Numerical simulations utilize the Reynolds Stress Model (RSM) alongside the Eulerian-Lagrangian particle tracking scheme to separate solid particles ranging from 0.1 to 8 μm. The performance of these SGV-equipped cyclones is compared against conventional cyclones with either roughened cone surfaces (C.R series) or smooth cone surfaces (C series). The results demonstrate that the maximum pressure drop occurs in cyclone C5 with a 2.5-turn SGV. It is found that introducing 1-mm roughness on the cone surface reduces the pressure drop compared to the same design with a smooth cone surface. For instance, the pressure drop of cyclone C5 is about 60 % greater than that of cyclone C.R5. The results indicate that the collection efficiency of SGV-based cyclones for 0.1-μm solid particles ranges from 25 % to 48 %, while conventional cyclones achieve only 4 %, highlighting the significant impact of SGVs on collection efficiency. When the solid loading is 5 %, the cyclone with 0.5-, 1-, 1.5-, 2-, 2.5-, and 3-turn SGVs and smooth cone wall can collect 50 % of the particles with diameters of 0.49, 0.23, 0.2, 0.18, 0.14, and 0.13 µm, respectively. In contrast, the conventional cyclone can collect 50 % of particles with a diameter of 1.24 µm. It is concluded that increasing solid loading enables all cyclone designs to collect smaller particles.

Reasonable gas flow distribution can greatly enhance the reduction performance of the shaft furnace. Key parameters such as burden voidage, pellet size, gas inlet diameter, and gas inlet angle directly govern gas-solid contact and reactant uniformity. In this work, the voidage inside the shaft furnace with different pellet sizes was calculated by DEM method, and the effects of operating parameters and conditions such as pellet size, gas inlet diameter and gas inlet angle on the reduction performance of the shaft furnace were analyzed by CFD method. It was shown that the voidage increase with the increase of pellet size and shaft furnace height, and the range of voidage for 9–15 mm particles increased from 0.20–0.42 to 0.29–0.48. Smaller pellets (9 mm) achieved superior reduction efficiency, yielding a maximum Fe mass fraction of 82.9 % at the solid outlet, whereas larger pellets (15 mm) suffered from internal diffusion limitations (Fe mass fraction: 60.4 %). Enlarging the gas inlet diameter significantly enhanced reduction reaction, with Fe mass fraction rising from 70.8 % (0.2 m) to 90.8 % (0.4 m). In contrast, gas inlet angle variations exhibited negligible influence (<2 % change in component distributions). This work provides a theoretical basis for optimizing the operating parameters of the shaft furnace and improving the reduction efficiency.

This study focuses on reducing heat losses in residential buildings, specifically in the climatic conditions of Ranchi, India. The analysis emphasizes the use of Expanded Polystyrene as an insulating material to address challenges associated with high thermal distribution rates in building envelopes. High thermal distribution in building envelopes and inefficient thermal systems are the primary drivers of increased energy consumption. Thermal distribution of the building envelope contributes to high energy consumption which shield the internal environment from exterior factors such as heating, cooling, humidity, rain, wind, snow, light, noise and air pollution depending on the location. In the month of June, average thermal flows reached 4.9 W/m 2 for walls and 18.6 W/m 2 for roofs due to higher ambient temperatures and solar irradiance. During winter, heat dispersion was reduced to 2.5 W/m 2 for walls and 1.7 W/m 2 for roofs, demonstrating the insulating efficiency of Expanded Polystyrene compared to conventional materials. This study demonstrates that Expanded Polystyrene significantly reduces heat losses by 90 % in roofs and 47 % in walls compared to conventional structures without insulation, showcasing its efficiency as an insulating material. Its application in real-world residential buildings can lead to substantial energy savings and improved thermal comfort, making it a practical solution for energy-efficient construction.