Band 23, Heft 1

The resource utilization of steel slag (SS) represents a critical strategy for integrating environmental protection with sustainable industrial development. In this study, SS was employed as an inorganic filler to investigate the effects of SS particle size and proportion on rigid polyurethane foam (RPUF). Optimal RPUF/SS composites were achieved with an 800-mesh particle size and a 50 % addition ratio. Additionally, the impact of modified SS on the performance of RPUF was examined. The findings indicated a 17.2 % enhancement in thermal insulation properties and a substantial improvement in flame retardancy, evidenced by a 5.7-fold increase in char yield. Despite a reduction in compressive strength, the practical applicability of the composites was not compromised. The performance of the composites was found to be independent of the specific surface area of SS but was significantly influenced by the type of modifier employed (phosphoric acid, formic acid, and silane coupling agents KH550, KH560, KH570). The modification of SS with appropriate agents is essential for enhancing the performance of RPUF/SS composites and for realizing high-value resource utilization of SS in the polyurethane industry.

Hydrogen (H 2 ) and ammonia (NH 3 ) are highly promising carbon-free fuels and can mitigate the greenhouse effect threat. The laminar combustion characteristics of ethylene (C 2 H 4 ) doped with H 2 and NH 3 were numerically calculated at large doping proportion (0–50 %), initial temperatures (T u  = 300–400 K), and initial pressures (P u  = 0.1–1.0 MPa) by using the Chemkin/Premix Code. The equivalence ratio ( Φ ) ranged from 0.75 to 1.5. Laminar burning velocities (LBVs), adiabatic flame temperatures (AFTs), net heat release rates (NHRRs), temperature sensitivity analysis (TSA), mole fractions of radicals of H, O, OH and intermediates of C 2 H 2 , NO, NO 2 , the rate of production (ROP) and the reaction pathways were studied in this research. The results showed that H 2 promoted the increase of C 2 H 4 /air LBVs, AFTs and NHRRs, while NH 3 had the contrary effects. R1 (H + O 2  <=> H + OH) had the largest positive sensitivity coefficient more than 0.3. Through the analysis of TSA and ROP, R146 (C 2 H 3  + H <=> C 2 H 2  + H 2 ) was the main reaction to product C 2 H 2 , and C 2 H 2 could be effectively inhibited after doping NH 3 . Additionally, the mole fraction of NO decreased as H 2 increased but increased with the increase of NH 3 . The peak NO 2 located much closer to the nozzle inlet after doping H 2 and NH 3 , and R392 (NO + HO 2  <=> NO 2  + OH) was the main reaction linked NO and NO 2 . The reaction pathway showed the effect of NH 3 on reducing CO 2 was stronger than that of H 2 .

Desalination is a crucial process in addressing the global water scarcity crisis. Among the various techniques available, pervaporation has emerged as a promising method due to its energy efficiency and high separation performance. The purpose of this research was to create a polyethersulfone (PES) membranes with high permeability and enhanced hydrophilicity. The membranes for pervaporation (PV) desalination were prepared using the phase inversion technique. PES membranes were fabricated from different concentrations while maintaining constant preparation conditions. These membranes were characterized using Zeta potential analysis, Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (X-ray), atomic force microscope (AFM) and thermogravimetric analysis (TGA). A permeate flux of 0.05 L/m 2  h and rejection percentage of 91 % were observed using PES 8 membrane from feed concentration 7,090 ppm. Reusability of PES membranes were tested our three cycles for desalination. The model equation was derived for salt rejection using the Box-Behnken model of response surface methodology (RSM). However, the experimental study revealed that the model suited the data perfectly. This study highlights the excellent potential of these PES membranes for treating salt solutions.

The ever-growing energy demand necessitates the deployment of renewable alternatives as fossil fuel reserves diminish. The biodiesel generated from these non-edible feedstocks, such as Karanja, and Jatropha oils, offers an environmental alternative without affecting food security. Transesterification process (using methanol as solvent and sodium hydroxide (NaOH) catalyst) was used to prepare biodiesel. The stainless steel, mild steel, and cast iron materials were immersed in Karanja oil biodiesel blends (B80 and B90) and commercial diesel for 1872 h at 37 °C to critically examine the corrosion behavior with their comparison analysis. It was unveiled that biodiesel is more prone to corrosion than diesel fuel under comparable identical conditions. The corrosion rates determined by weight loss measurements in biodiesel were found to range from 0.0173 mm/year to 0.0194 mm/year for stainless steel, 0.03076 mm/year to 0.03232 mm/year for mild steel, and from 0.0505 mm/year to 0.0528 mm/year for cast iron, as compared to 0.009 mm/year for stainless steel, 0.015 mm/year for mild steel, and 0.017 mm/year respectively for cast iron in diesel. The intense severe melting of biodiesel as compared to diesel samples can be determined by employing the SEM analysis at 200X and 400X magnification scales. Hence, this study has underscored the significance of selecting the appropriate corrosion resistant materials that are suitable for the continued prolonged storage and utilization or application biodiesel.

In this investigation, the principles of non-equilibrium thermodynamics are employed to investigate the implications of geometric parameters on engine performance and exhaust back pressure in catalytic converters. The effects of components utilized for engine exhaust management on exhaust back pressure and anomalous engine operation have been extensively studied. This study explores how the geometric parameters of catalytic converters influence back pressure in the exhaust manifold through a detailed numerical analysis. Five models of catalytic converter with different geometric parameters at the inlet section, outlet section, inlet cone angle, outlet cone angle, and porous zone were tested to determine the variations in back pressure. For the monolith, a porous region is used where inertia and viscosity are defined by Darcy’s law, and discrete channel simulation is performed using the “Reynolds-average Naiver-Stokes (RANS) equations”, k-ω turbulence model, and a pressure-based solver. The numerical findings revealed that back pressure increased by up to 15 % with the rise in exhaust gas velocity from 0 to 25 m/s. Among the five models, the optimal configuration reduced back pressure by approximately 20 % compared to the baseline model, primarily due to adjustments in the length of the porous zone and conical sections. The outcomes demonstrate that the back pressure rises as the velocity of exhaust gas rises, and the optimization of configurations is determined by the design of the porous zone and conical sections. The findings prove that the efficiency of catalytic converters is considerably enhanced through the role of transport processes of mass, momentum, and energy, as variations in geometric configurations have a substantial effect on back pressure. Ultimately, this research offers valuable insights that could lead to the development of more efficient catalytic converters, thereby enhancing the control of automotive emissions and sustainable environmental practices. Key contributions of this study include a systematic evaluation of back pressure variations across multiple geometries, offering a pathway for enhanced engine performance and reduced environmental impact. The results have practical implications in improving design methodologies for catalytic converters, with potential applications in real-world automotive manufacturing.

Stirred bioreactor has been widely used in biopharmaceutical field, and it is particularly important to understand the culture environment of animal cells in stirred bioreactor. This study, utilizing Computational Fluid Dynamics (CFD) in conjunction with the Population Balance Model (PBM), explores the effect of various operational conditions and impeller combinations (downward-pumping elephant ear impeller (EED) combined with a concave disc turbine impeller (CBDT), dual downward-pumping elephant ear impellers (EED-EED), and a combination of downward-pumping (EED) and upward-pumping (EEU) elephant ear impellers) on bioreactor performance, with the goal of developing a stirred bioreactor suited for animal cell culture. The findings reveal that increasing the stirring rate significantly enhances fluid circulation within the bioreactor, leading to an increase in gas holdup. Enhanced stirring rate and aeration not only facilitate bubble dispersion but also result in a significantly higher gas holdup in the lower part of the bioreactor compared to the upper part. Moreover, higher stirring rate also lead to larger bubble diameters. At the highest stirring rate, the maximum hydrodynamic stress in the bioreactor reaches 16 Pa, while the Kolmogorov length scale is smaller at high stirring rate. The EED-EEU demonstrates effective gas dispersion with uniform bubble distribution and minimal hydrodynamic stress; the EED-EED combination, while offering the best bubble dispersion, is associated with larger bubble diameters and higher hydrodynamic stress.

Alcohol-based biofuels, including butanol and ethanol, have garnered heightened attention due to an impending global demand for sustainable transportation fuels. Nevertheless, the potential of propanol, an additional alcohol-based fuel, has not been completely evaluated, particularly in comparison to its counterparts. In this investigation, the environmental and performance characteristics of propanol, ethanol, and butanol are compared when blended with gasohol. This study conducts a comprehensive comparison of the environmental and performance characteristics of propanol, ethanol, and butanol blends when combined with gasohol. Key areas of focus include engine performance, fuel stability, and emissions profiles (CO, NOx, HC, and CO 2 ). Experimental analyses, encompassing varying blend ratios (BR), engine speeds, and compression ratios, reveal that optimized propanol-gasohol blends significantly reduce greenhouse gas and pollutant emissions while enhancing engine efficiency compared to ethanol and butanol blends. Optimized blend ratios exhibit the potential to reduce emissions while additionally enhancing engine efficiency, thereby facilitating the development of further sustainable and environmentally friendly fuel alternatives. These findings reveal potential biofuel strategies for the transportation sector that are designed to mitigate its environmental implications. The optimized propanol-gasohol blends achieved a 15 % reduction in CO 2 emissions, 10 % reduction in NOx emissions, and 12 % reduction in HC emissions, while improving engine performance metrics such as combustion efficiency. This study’s originality lies in its comprehensive evaluation of propanol as a fuel additive, addressing gaps in the literature related to its emissions, engine performance, and optimization. Unlike ethanol and butanol, propanol’s unique properties, including improved emission reductions and compatibility, were systematically investigated under varied operating conditions. These findings provide new perspectives on sustainable fuel development.

Hydrometallurgical processes are considered essential for recovering zinc resources from electric arc furnace dust (EAFD). The precipitation of zinc is crucial to the entire hydrometallurgical process, as it impacts both the quality of zinc products and the efficiency of the process. This study investigated the zinc precipitation process from ammonia–ammonium bicarbonate leached solutions using acetic acid as a precipitant. The variation in alkalinity and total ammonia during zinc recovery was studied, and the properties of the zinc-precipitating products were systematically analyzed. Zinc could be quantitatively precipitated from purified EAFD leachate using acetic acid, achieving up to 85 % zinc recovery as high-grade hydrozincite (Ζn 5 (CO 3 ) 2 (OH) 6 ). During the process, the alkalinity concentration decreased continuously with increasing precipitant addition, while the total ammonia concentration decreased to a certain value and then remained constant. High-grade zinc-precipitating products of Ζn 5 (CO 3 ) 2 (OH) 6 were obtained, characterized by needle-and-whisker crystal morphology. The zinc precipitate could thermally decompose to ZnO within the temperature range of 200–300 °C. These results provide valuable parameters for the industrial treatment of EAFD.

In microfluidic systems, micromixers are of utmost importance for achieving efficient mixing. However, current micromixers still have deficiencies in mixing efficiency, which restricts their widespread application in fields such as biotechnology, chemical synthesis, and environmental analysis. This paper focuses on the influence of variable-angle baffles on the mixing efficiency of micromixers. By altering the geometric configurations of baffles, the mixing efficiency of solutions is enhanced. Specifically, the impacts of baffle direction, quantity, and height are explored. Additionally, groups of three baffles are utilized to investigate the effect of staggered heights on mixing. Through COMSOL simulations, it is found that the 45-degree structural baffle is highly conducive to solution mixing. An increment in baffle number prolongs the fluid mixing path, thereby augmenting the efficiency. Similarly, a rise in baffle height intensifies the fluid disturbance and elevates the mixing efficiency. Notably, setting a group of baffles to 0.15–0.05–0.1 mm is particularly advantageous for enhancing the mixing efficiency, as this configuration optimizes the fluid flow regime and promotes chaotic convection, thus significantly improving the micromixer’s performance.

One of the disadvantages of methanol synthesis water-cooled quasi-isothermal reactors is the high energy consumption to produce saturated steam. This study proposes two novel configurations for plate exchanger methanol synthesis reactors with axial-radial flow to minimize energy consumption and maximize methanol production. These configurations are compared via three-dimensional computational fluid dynamics. There are two sets of plates in the plate reactors to cool the gas in the reactor’s shell, which are named inner and outer plates. In novel configuration 1 (NC1), the outer plates are omitted, the first radial part has been considered an adiabatic bed, and the second quasi-isothermal. In novel configuration 2 (NC2), the fresh feed stream has been passed through outer plates for preheating rather than using saturated steam. The benefit of these configurations are reduction of water consumption by 50 % and also energy saving for steam generation. Moreover, methanol production is raised by 3 % in NC1 rather than in conventional configuration. Also, preheating of inlet feed in NC2 leads to an increase of 2 % in methanol. The superior configuration is NC2, although, in NC1, methanol production is higher; also, some hot spot points would have emerged in the middle of the reactor.