Volume 22, Issue 8

The current study presents a fundamental understanding of the behavior of different-sized hydrogen bubbles rising in a new slag – metal system featured with a thick upper slag layer and ever-changing slag thickness and slag physical properties in the H 2 -based smelting process, based on newly developed CLSVOF model simulations. The evolution of bubble shape, bubble rising velocity, and the formation, collapse and detachment of metal liquid film wrapped on the bubble are predicted. The results show that decreasing the slag layer thickness or the slag viscosity delays the detachment of the metal liquid film from the bubble, increases the bubble rising velocity in the metal layer, but make no difference to the bubble terminal rising velocity in the slag layer. As a result, the bubble has shorter rising time in the bath with a higher slag viscosity. The resistance of the slag – metal interface to the bubble decreases with the increase of the bubble diameter, and small bubble therefore passes through the interface more slowly than the large one. In addition, the bubble shape evolution and bubble breakup in the slag layer are complicated with the increase of the slag thickness, bubble diameter and slag viscosity.

In the steel industry, blast furnace gas (BFG) is huge with complex components. The existence of hydrogen sulfide (H 2 S) in the BFG can produce sulfur dioxide (SO 2 ) after combustion, which will increase the source of SO 2 pollution and make the desulphurization more difficult, to be threat to people health. At present, the removal of H 2 S by dry adsorption with modified activated carbon adsorbent is a high-precision and low-cost desulphurization method. However, the effect of complex gas components in BFG on the adsorption of H 2 S by activated carbon adsorbent is not sufficient. Based on the fixed bed adsorbent evaluation system, a new type of highly efficient copper-cerium oxide (Cu–Ce–O) modified activated carbon H 2 S adsorbent was developed. And the effects of carbon monoxide (CO), carbon dioxide (CO 2 ), hydrogen (H 2 ), oxygen (O 2 ), sulfur dioxide and hydrogen chloride (HCl) in BFG on the desulfurization activity of adsorbents were investigated. The results showed that the performance of H 2 S removal decreased in the presence of CO, CO 2 , HCl and SO 2 , and improved in the presence of H 2 and O 2 . Other parameters were also studied which might influence the process. The application of modified activated carbon adsorbent in simulated BFG is basically stable. According to the fitting results of adsorption kinetics for the five adsorption models, as the atmosphere becomes BFG from N 2 , pore diffusion becomes the main adsorption form. However, the effects of internal diffusion, chemical adsorption and external mass transfer decreased. The Bangham model is the most suitable model to describe H 2 S adsorption process.

The present study assessed the capability of Tetradesmus sp . NITD18, a green algal strain collected from the run-off water of a gas producing industry at Durgapur, for removing p -nitrophenol (PNP) from synthetic wastewater. The maximum removal efficiency of 59.64 ± 0.30 % was observed at an initial PNP concentration of 5 mg/L, initial pH 7, inoculum size of 15 % (v/v), and an incubation period of 15 days. The effect of pH (7–12) and inoculum sizes (5–15 %) on the removal of PNP using the test strain was assessed by varying these parameters judiciously. The results suggested that the Tetradesmus sp. NITD18 strain has considerable potential for PNP removal from wastewater.

A comprehensive understanding of the flow regime transition is a prerequisite for designing and operating the rotating drum, especially when dealing with non-spherical particles. In this study, the multi-sphere method was used to construct cylindrical particles. The optimal number of spherical elements for particles with different aspect ratios was determined in terms of kinetic energy, rotational kinetic energy, collision number, collision force, deformation and angle of repose. And the effects of filling rate, rotational speed and particle size on the macro- and micro-behavior of cylindrical particles were systematically investigated. The results show that when the aspect ratio of cylindrical particle is 2, 3 and 4, the optimal number of spherical elements are 5, 8, and 10, respectively. Four flow structures, namely rolling, cascading, cataracting and centrifuging, were identified with the increase of the rotation speed, but the transition boundary from rolling to cascading is not clear due to the irregular particle shape. Three flow structures, namely slipping, transition, and cascading, were identified with the increase of the filling degree. The transition diagram of flow regime was established. The results show that the aspect ratio has a great influence on the flow transition from slipping to cascading regime. The area covered by the transition flow regime expands as the aspect ratio increases, necessitating a greater filling degree to achieve a stable rolling flow regime.

This study investigates the impact of low-temperature top-lit updraft reactor chamber size on GNSBC yield and properties. For this study, the volumes of carbonization chamber (2,364, 2,013, 1,468, and 970 cm 3 ) in a biomass-fueled TLUD biomass gasifier were varied, and the resulting biochar was analyzed using SEM, EDX, and FTIR. The novelty of this work lies in its investigation of the unexplored impact of carbonization reactor compartment size on groundnut shell biochar properties and yield, driven by the need to optimize biochar production efficiency and support sustainable waste management practices. The results showed that carbonization chamber size variation significantly affected GNSBC yield, with an initial increase followed by diminishing returns. An increase in the carbonization compartment size led to decreased carbonization duration, increased carbonization temperature, increased porosity, and decreased oxygen content. SEM analysis revealed consistent amorphous and multi-layered morphological features across BC samples, while EDX analysis confirmed high carbon content in the samples. FTIR spectroscopy confirmed the presence of oxygenated functional groups suitable for pollutant adsorption, supporting GNSBC’s role in environmental remediation and industrial processes. This research contributes to optimizing biochar production efficiency, advancing circular economy goals, and sustainable waste management practices.

The development of cost-effective and highly efficient biochar-based catalysts is essential for the catalytic steam reforming process of bio-oil. In this study, pickling peanut shell biochar was used to prepare biochar-supported Ni/Co monometallic catalyst and biochar-supported nickel-Co bimetallic catalyst through the impregnation method. The catalytic effect of these catalysts on acetic acid (a bio-oil model compound) steam reforming was investigated. It was found that Co could enhance the dispersion of metal particles. The catalyst exhibited the best catalytic effect and significantly improved resistance to carbon deposition with a loading of 8 wt% and a Ni-to-Co ratio of 6:2. At the temperature of 600 °C and the S / C ratio of 3, the selectivity of H 2 reached 84.48 %, and the conversion of acetic acid reached 95.49 %. A synergistic effect was observed between Ni and Co, leading to increased metal dispersion, enhanced reducibility, and a higher number of active centers. Co facilitates water dissociation and promotes the oxidation of C–H and mobile O, resulting in a faster decarbonization rate. The effective utilization of biochar-based catalysts and the rational utilization of bio-oil contribute to the timely achievement of carbon emission reduction targets.

2,4-Dinitrotoluene (2,4-DNT) is a broadly applied nitroaromatic compound with multiple applications, and its simple production has resulted in its extensive utilization in producing explosives, dyes, and rubber. This substance is hazardous and induces genetic mutations in humans, fish, and microorganisms. Thus, this research was done to assess the effectiveness of the three-dimensional electro-Fenton (3D/EF) process employing magnetic activated carbon particle electrodes (GAC/Fe 3 O 4 ) in eliminating 2,4-dinitrotoluene from water-based solutions. In this experimental investigation, Fe 3 O 4 nanoparticles were created using the chemical co-precipitation technique. The G/β-PbO 2 anode was fabricated by electrochemically depositing PbO 2 layers on graphite sheets. G/β-PbO 2 and stainless steel were utilized as the anode and cathode, respectively. The structure, particle size, and properties of the GAC/Fe 3 O 4 nanocomposite were analyzed using FESEM, XRD, and EDX. The morphology of the G/β-PbO 2 electrode was also examined using SEM. The Taguchi experimental design method was employed to identify the optimal conditions. The outcomes demonstrated that higher reaction time and current density, as well as lower pH and pollutant concentration, resulted in improved 3D/EF efficiency. Accordingly, the optimum values of parmeters were identified to be a concentration of 2,4-DNT = 50 mg/L, pH = 3, electrolysis time = 100 min, and current density = 8 mA/cm 2 . With these parameters, the degradation efficiency of 2,4-DNT through the examined system was 98.42 %, alongside removal efficiencies of 84.69 % for COD and 79.67 % for TOC. Additionally, the results indicated an increase in the average oxidation state (AOS) (from 1.27 to 1.95) and carbon oxidation state (COS) (from 1.27 to 2.75) in the 3D/EF process, along with a decrease in the COD/TOC ratio (from 1.81 to 1.36), indicating the effectiveness of the 3D/EF system in enhancing the biodegradability of 2,4-DNT. Overall, the combined 3D/EF process with a G/β-PbO 2 anode has relatively high efficiency in degrading solutions containing DNT and can be considered a viable treatment option for wastewater containing substances such as 2,4-DNT.

This study investigated phenolic compounds (PC), chemical oxygen demand (COD) and total carbon organic total (TOC) removal from olive mill wastewater OMW via activated persulfate oxidation. Persulfate (PS, S 2 O 8 2 − ${\mathrm{S}}_{2}{\mathrm{O}}_{8}^{2-}$ ) was activated by thermal and transition metal to form sulfate radical ( S O 4 · − $\mathrm{S}{\mathrm{O}}_{4}^{{\cdot}-}$ ). A mathematical model was developed, and the process variables, namely oxidant dose (0.05 and 0.1 g L −1 ), type of catalyst (Fe 2+ , Cu 2+ ), time of treatment (5 and 20 min) and temperature (25 and 45 °C) and their interaction were examined using a full factorial design methodology 2 4 . The results indicated that activation methods are efficient for reduction of PC and COD in OMW. Under conditions maximizing responses, there was a considerable increase in PC, COD and TOC removal (44.73 %, 62.39 % and 95.13 % respectively). The correlation coefficient values of the polynomial model were found to be 90 % (CP removal) and 86 % (COD removal). The predicted values obtained using the response functions agreed well with the experimental data.

Water injection for absorbing corrosive gases NH 3 , HCl and H 2 S is a widely employed method to mitigate the risk of ammonium salt corrosion in the hydrogenation units. To ensure the efficient prevention of ammonium salt corrosion, a numerical model integrating the hydrodynamics of gas–liquid and the reaction of interphase mass transfer was built based on Euler–Lagrange method in this work. The flow and mass transfer characteristics of complex multi-component system in water injection pipeline were investigated, and the correlation between process operating conditions and gas removal performance was analyzed. The results reveal that the removal efficiencies of corrosive gases in pipeline are influenced by the characteristics of gas–liquid flow and mass transfer, with HCl showing higher removal efficiency compared to NH 3 and H 2 S. Furthermore, the increasing flow rate of water injection, the reducing corrosive medium content and the decreasing droplet diameter have a positive impact on the removal efficiencies of corrosive gases, while the impact of gas-flow velocity on the removal efficiencies of corrosive gases primarily depends on the residence time of droplets. These results have important theoretical value and engineering guiding significance for intensifying the process of water injection in hydrogenation units.

Acidic gases such as H 2 S and CO 2 are generated in the refineries during coal gasification. These pollutant gases need to be treated before releasing to the atmosphere. Conventionally, H 2 S gas is treated by Claus process in which H 2 S is converted to elemental S and H 2 O, in presence of O 2 at ∼1,200 K. In the present energy scenarios, hydrogen has got importance as a source of clean fuel for industrial application. The H 2 S generated in the refineries can be a potential precursor of hydrogen. If this hydrogen can be obtained by thermal decomposition of H 2 S, that can increase the overall economic value of the H 2 S containing streams and the produced hydrogen can be used for hydrocracking and hydro-treating in refineries, as well as to synthesize value-added products for chemical industries. However, H 2 S thermal decomposition is an endothermic and equilibrium limited reaction (equilibrium conversion is only ∼15 % at 1,000 K), requiring a very high temperature (∼1,500 K) to achieve even a conversion of greater than 40 %. Packed Bed Catalytic Membrane Reactor (PBCMR) for thermal decomposition of H 2 S can be a potential technology augmentation and process intensification to increase this equilibrium conversion. In this work, modeling and experimental studies of H 2 S thermal decomposition using in-house designed & developed PBCMR have been carried out. The modeling studies were validated with experimental data. Clay-alumina ceramic tubular membrane (L: 250 mm; OD: 12 mm; thickness: 2 mm) was fabricated using extrusion process having an average membrane pore size of ∼1 μm and with a porosity of ∼20 %. Pt (2 %) coated alumina extrudes were used as catalyst to accelerate the reaction kinetics. Experimental studies showed that H 2 S to hydrogen conversion of ∼90 % is achieved using PBCMR at ∼1,523 K, compared to only ∼40 % conversion in a conventional packed bed tubular reactor (without membrane). Modelling studies were carried out to study the influence of operating parameters such as, reactor wall temperature, feed temperature, pressure and feed velocity. Studies showed that reactor wall temperature is having the most dominant effect on H 2 S conversion, which is confirmed by experimental findings. The studies offer useful insights into the application of PBCMR technology for management of waste gas stream containing H 2 S and recovery of hydrogen.