Abstract The article discusses radial mixing in a Horizontal Aerated Tubular Reactor (HATR). The study aimed to experimentally investigate mixing in HATR by determining mixing time, liquid circulation time, and Peclet number values, which measure the ratio of advective to diffusive transport rates. The experimental setup included a transparent tube for observing fluid mixing and a color tracer was used for visualizing mixing. Mixing and circulation times were determined using non-intrusive optical method. The experimentally determined circulation time was in the range of 3÷6.5 s, and the mixing time was in the range of 5÷20 s. The results suggested that fluid flow structure in HATR was closer to plug flow rather than ideal mixing, as indicated by high Peclet numbers (20÷45).

Abstract The main challenge in using Zeolit Alam Lampung (ZAL) as a catalyst lies in controlling its acidic nature which is influenced by the content of alkali metals, alkaline earth metals, transition metals, and Si/Al ratio. Controlling by reducing and adding metals with higher acidity is necessary. This research involved two stages: ZAL Swelling formation followed by adding Cu, Ni, and Fe metals to make a Cu-Ni-Fe/ZAL Swelling catalyst. The acid distribution analysis using the NH 3 -TPD profile test showed that the Cu-Ni-Fe/ZAL swelling catalyst exhibited higher Lewis-type acidity and more uniform distribution compared to Brønsted acid. The addition of Cu, Ni, and Fe metals can modify the acidity strength of ZAL Swelling to form Cu-Ni-Fe/ZAL Swelling catalysts with Lewis and Brønsted sites at lower temperatures (120–550 °C) compared to ZAL Swelling (120–750 °C). This gives an idea about the optimization of the arrangement of Lewis and Bronsted acid sites to present amphoteric features.

Abstract Citronellyl acetate is a crucial component of flavor and fragrance in the food, cosmetic, and pharmaceutical sectors. In non-aqueous media, it can be successfully produced via lipase catalysis. This study focuses on the lipase-catalyzed trans-esterification of citronellol alcohol with geranyl acetate ester in a non-aqueous medium to produce citronellyl acetate. For the synthesis of citronellyl acetate, crude acetone powders isolated from several plant seedlings of black cumin, fenugreek, coriander, flax, and rape seed were examined for lipase activity. Black cumin seedling lipase had the highest level of citronella acetate production with a yield of 76.32% in 72 h of reaction time. To assess the impact of different reaction parameters on citronellyl acetate production in organic solvents, hexane was chosen as the best solvent, and black cumin seedling lipase was selected as the best biocatalyst. The highest conversion yield of ester (76.32%) was found when 0.25 M of geraniol acetate and 0.25 M of citronellol reacted at 41 oC after 72 h in the presence of 0.25 g of seedling lipase enzyme in n-hexane. It has been determined that crude black cumin seedling lipase is inexpensive yet effective and has the potential to be used industrially for the synthesis of terpene esters.

Abstract The preparation of composite metal oxide to attain high efficiency in removing phenol from wastewater has a great concern. In the present study, the focus would be on adopting antimony-tin oxide coating onto graphite substrates instead of titanium; besides the effect of SbCl 3 concentration on the SnO2-Sb 2 O 3 composite would be examined. The performance of this composite electrode as the working electrode in the removal of phenol by sonoelectrochemical oxidation will be studied. The antimony-tin dioxide composite electrode was prepared by cathodic deposition with SnCl 2 . 2H 2 O solution in a mixture of HNO 3 and NaNO 3 , with different concentrations of SbCl 3 . The SnO 2 -Sb 2 O 3 deposit layer’s structure and morphology were examined and the 4 g/l SbCl 3 gave the more crystallized with nanoscale electrodeposition. The highest removal of phenol was 100% at a temperature of 30 o C, with a current density (CD) of 25 mA/cm 2 .

Abstract This study focused on investigating the heat transfer and flow dynamics of a catalyst granule within a pilot calciner, employing both numerical modeling and computational fluid dynamics. The research comprised two primary components: (1) Simulation of the gas flow within the pilot calciner using the Eulerian–Eulerian approach, treating gases and catalyst particles as distinct phases – gas and granular. The model, encapsulating both heat transfer and flow processes, was developed in Fluent software version 16.0. Its accuracy was confirmed against empirical data from a pilot-scale calciner unit. (2) Subsequent to validation, the model was utilized to examine the distribution characteristics within the flow field, including the temperature profiles of gas and particles, the vector velocity field of the gas across different phases, and the overall heat transfer coefficient. This investigation aims to enhance the understanding of the complex heat transfer and flow dynamics in calciners, facilitating the optimization of operational parameters, performance, and structure of pilot-scale equipment. Furthermore, it provides foundational data pertinent to the future exploration of real-world industrial applications.

Abstract Rising energy prices have increased the popularity of many renewable energy sources including heat pumps. In the case of ground heat pumps research related to the analysis of the operation and selection of ground heat exchangers as a heat source are insufficient. With this in mind, on the operation of the horizontal slinky coil heat exchanger research work has been undertaken. As a research tool, the Computational Fluid Dynamics has been used. To check the adequacy of the CFD model, a validation of the model was carried out using the results of research on a real heat exchanger. Comparison was made: values of ground temperatures, outlet temperatures from the exchanger, and heat flux exchanged by the heat exchanger. In the opinion of the authors, the validation of the CFD model was successful.

Abstract In this study, HCl and H2SO4 were used to compare the best conditions for producing glucosamine from the dry chitin of shrimp shells. The results showed that for HCl hydrolysis, the most favored conditions were 12 M, 80 °C, 2 hours, and a chitin-to-acid volume ratio of 1:20, whereas, for H2SO4 hydrolysis, the most favored conditions were 6 M, 90 °C, 5 hours, and a chitin to acid volume ratio of 1:20. HCl produced pured glucosamine with a higher yield than H2SO4. Additionally, our findings indicated that glucosamine could be detected using a UV detector with a weak signal, whereas we recommended using an RI detector for a comparably stronger signal. Our production maximum yield of 283.9 ± 13.8 mg Gln g−1 chitin from HCl hydrolysis was comparable to that of other studies, with a comparison between using HCl and H2SO4 being highlighted.

Abstract The purpose of this study was to investigate the impact of process parameters such as interfacial tension, type of surfactants, and their concentration on simple oil-in-water dispersion. Explored systems were prepared with 5% liquid paraffin oil and aqueous phase with emulsifiers Tween 40 of concentrations from 0.008325 mM to 0.025 mM and Tween 80 with concentrations ranging from 0.00375 mM to 0.011 mM. All systems were characterized in terms of their density and interfacial tension. In the next step analysis of droplet size distributions and mean droplet diameter was performed. The results showed that the size of paraffin droplets decreased as the concentration of surfactants grew. This trend is accompanied by decrease in the interfacial tension between phases. The correlation between mean drop size and the energy input and physical properties of both liquids was developed. The last step provides scientific evidence for the formulation of stable droplets of liquid paraffin.

Abstract The stable transportation of pulverized coal in the vertical pipe is significant for the operation of the gasifier. There are few studies on the flow characteristics and flow pattern transition of particles in vertical pipes with small diameters. This paper has modeled and analyzed the flow characteristic of powder in dense-phase pneumatic conveying through 25 mm vertical pipe using CFD. Firstly, the grid independence is verified to determine the optimal mesh size. Then, the influences of different solid loading ratios (SLRs) and conveying velocities on particle flow characteristics, flow stability, and flow pattern transition are investigated. The results show that the flow pattern in the vertical pipe changes from annular flow to uniform flow at high SLR and low conveying velocity. Moreover, the evolution regulation of resistance characteristics under different conveying velocities is further revealed. Considering the conveying stability and economic benefit, the most suitable conveying velocity is 6 m/s.

Abstract The present study aimed to prepare hydrogel based on polyvinyl alcohol (PVA) and gelatin (Ge) and characterization of PVA/Ge hydrogel for their potential use as a sustained drug delivery system. Polyvinyl Alcohol (PVA) and-Gelatin (Ge) were cross-linked using glutaraldehyde (GA) as a crosslinking agent and hydrochloric acid (HCl) as a catalyst. Different feed polymer ratio and crosslinking agent concentration were used to prepare a series of PVA/Ge hydrogels. The obtained PVA/Ge hydrogels were investigated for dynamic and equilibrium swelling studies. The effect of polymers ratio, degree of crosslinking and pH of the medium on swelling of PVA/Ge hydrogels was investigated. Furthermore, the values of diffusion coefficient (D), volume fraction, polymer-solvent interaction parameter, molecular weight between crosslink and crosslink density were calculated. For swelling studies, 0.05M USP phosphate buffer solutions of different pH (1.2, 5.5, 6.5 and 7.5) were used. For the drug release study, ciprofloxacin HCl was loaded into selected samples as a model drug. The release of drug from these samples was performed for 12 hours in USP phosphate buffers of pH 1.2, 5.5 and 7.5. The release data from these samples were fitted into various kinetic models like zero order, first order, Higuchi and Peppas models to investigate the release mechanism. It was found that by varying the composition of PVA/Ge hydrogel and GA concentration, a significant difference was observed in drug release kinetics. FTIR spectroscopy and X-ray diffraction were used for the characterization of hydrogels. PVA/Ge hydrogel showed sustained release of the model drug at various pH values suggesting its potential use as a sustained drug delivery system.