Volume 22, Issue 7

The adoption of biofuels as an energy source has experienced a substantial increase, exceeding the consumption of fossil fuels. The shift can be ascribed to the availability of renewable resources for energy production and the ecological advantages linked to their utilisation. Nevertheless, due to its intricate characteristics, the process of producing ethanol fuel from biomass poses difficulties in terms of administration, enhancement, and forecasting future results. To tackle these difficulties, it is crucial to utilise modelling techniques like artificial intelligence (AI) to create, oversee, and improve bioethanol production procedures. Artificial Neural Networks (ANN) is a prominent AI technique that offers significant advantages for modelling bioethanol production systems’ pretreatment, fermentation, and conversion stages. They are highly flexible and accurate, making them particularly well-suited. This study thoroughly examines several artificial intelligence techniques used in bioethanol production, specifically focusing on research published in the past ten years. The analysis emphasises the importance of using AI methods to address the complexities of bioethanol production and shows their role in enhancing efficiency and sustainability in the biofuel industry.

Thermal crosslinking of polyimides is a relevant methodology to increase their chemical resistance. This reaction is induced by heating after polymerization. Although this reaction is considered a viable route to modify polyimides, there is controversy over the specific temperature for the reaction. To contribute to the knowledge of crosslinked structures, we performed a differential scanning calorimetric (DSC) and solubility test studies on a series of polyimides with different molar ratios of carboxylic acid groups. With 3,5-diaminobenzoic acid (DABA) as a source of carboxylic acid groups, the copolyimides were synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4ʹ-hexafluoropropylidenebis( p -phenylenoxy)dianiline (6FPA) to form blocks of 6FDA:6FPA (n) and 6FDA:DABA (m) from m  = 0–100 %. Flat films were prepared at 50 ± 3 µm with polyimides. In the thermogram of the flat films, a heat absorption zone associated with the decarboxylation reaction was identified with an endothermic minimum at 260 °C, which was assigned to the crosslinking temperature. Furthermore, heating time was varied for 3–36 h to determine the insolubility of the thermally crosslinked polyimide; from 24 h of heating the polyimide were insoluble. The polyimides were thoroughly characterized by ATR-FTIR, 1 H NMR, TGA, SEM, the fractional free volume (FFV) was determined by the Bondi’s group contribution method and solubility to different organic solvents. The FFV of crosslinked polyimides increases relative to pristine polyimides by 2 % for those with higher DABA content and 40 % for those with lower DABA content. Finally, also the glass transition temperature increases in the crosslinked polyimides relative to the pristine ones from 280 °C for the lowest DABA content to 402 °C for the highest DABA content, demonstrating the increase in the thermal resistance of the structure.

The Laval nozzle is an important component of the supersonic cyclone to achieve the change of gas–liquid two-phase, and the condensation characteristics of the Laval nozzle have an important influence on the separation performance of the supersonic cyclone. In this work, the effect of inlet water vapor mass fraction on the condensation characteristics in the Laval nozzle was investigated using numerical simulation and experimental methods by establishing a three-dimensional numerical model of air-water vapor supersonic condensation flow. The flow field structures in the Laval nozzle under different inlet water vapor mass fractions were investigated, including Mach number, pressure, and temperature and the effects of the inlet water vapor mass fraction on the liquefaction characteristics in the Laval nozzle were investigated. In addition, the droplet distribution in the Laval nozzle were also tested by a particle image velocimetry (PIV) experimental system. The comparison of simulation and experimental results indicates that the numerical model established in this work can effectively describe the real flow situation in the Laval nozzle. The results show that the inlet water vapor mass fraction has a little effect on the flow field structure in the Laval nozzle, and has the significant impact on the water vapor condensation characteristics. With increasing the inlet steam mass fraction from 5 % to 12.5 %, the nucleation rate, droplet number, and separation efficiency in the Laval nozzle increase to 4.05 × 10 21  kg −1  s −1 , 3.67 × 10 14  kg −1 , and 79.4 %, respectively, and when further increasing the inlet steam mass fraction to 15 %, these parameters decrease.

This study aimed to investigate the performance of the thin layer nanostructures of Co/Al 2 O 3 –ZrO 2 in the dry reforming of methane (DRM) in a microchannel reactor. The nanostructures were prepared via utilizing the thermal evaporation method. Reactor tests were carried out at various coating times of 2, 3, and 4 min and temperatures of 700, 750, and 800 °C with a feed flow rate of 10 ml/min and a 1:1:8 ratio of helium, carbon dioxide, and methane. Also, grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) were used to identify catalyst features. According to the obtained results, the highest percentage of conversion in all samples was observed at 800 °C. The results of the reactor tests also revealed that the activity of catalyst layers highly depends on coating time. The findings demonstrated that raising deposition time improves the distribution of particle size and catalyst loading. Considering the nanostructure of Co/Al 2 O 3 –ZrO 2 , the sample undergoing 4 min coating time yielded the highest amount of primary methane conversion (89.3 %), primary carbon dioxide conversion (92.4 %), and H 2 /CO molar ratio (0.91). The stability test of the catalyst layers for 28 h at the optimum condition ( P  = 1 atm, T  = 800 °C, t  = 4 min deposition time, CH 4 /CO 2  = 1, and GHSV = 48,000 mL g −1  h −1 ) showed that the catalysts prepared by this method had a good stability.

To adapt to the increasing proportion of new energy power generation capacity, coal power must transition from its traditional role as the primary power source to serving as a fundamental backup and system regulation energy source. The circulating fluidized bed technology is known for its wide range of load regulation capabilities; however, emissions of pollutants during load regulation can exhibit significant variability. This study utilized Aspen Plus software to develop a circulating fluidized bed combustion model based on a gas-solid fluid dynamics model, an equivalent coal pyrolysis model, and a multi-phase macroscopic combustion reaction dynamics model of pyrolysis products. This model was used to predict both the temperature distribution within the furnace chamber and the distribution of pollutant concentrations. Predictions of pollutant emissions from 100 % load to 30 % load of the circulating fluidized bed were explored under the original combustion condition and 5 % proportion of recirculated flue gas. Under the primary combustion condition, the emission concentration of NO x showed a decreasing and then increasing trend with decreasing load, while the concentration of nitrous oxide, in contrast to NO x , showed an increasing and then decreasing trend. The effect of recirculated flue gas on pollutant emissions was not significant at reduced loads. This study aims to provide technical support and theoretical guidance for the management of pollutant emissions from the deep peak regulation of actual circulating fluidized beds.

In 2015, the participants of the Paris Agreement collectively acknowledged the urgent need for immediate actions to decarbonize their national economies, with the aim of mitigating the adverse impacts of climate change. There is a call for policymakers to step up efforts to significantly reduce greenhouse gas (GHG) emissions in all economic sectors, with a focus on prioritizing options that can deliver substantial emission cuts. Some industry and transport subsectors present significant challenges in terms of technical and economic feasibility. Viable solutions for these sectors, known as “hard-to-abate” sectors, are limited. Green hydrogen has emerged as a promising alternative that is gaining increasing attention. It is poised to play a crucial role in transitioning towards a more sustainable future. There is a growing interest in green hydrogen among researchers, institutions, and nations, all committed to advancing its development, improving efficiency, and reducing costs. This paper explores the concept of green hydrogen, particularly its production processes that rely on renewable energy sources in Uruguay. It demonstrates the significant potential for green hydrogen production, facilitating the transition from fossil fuels to clean energy and promoting environmental sustainability through the widely accepted electrolysis process. Uruguay currently boasts a high percentage of renewable electricity generation (reaching 97 % in 2020). To support this further, there is a need to increase renewable energy capacity, which would impact the energy prices. The cost of energy accounts for more than 40 % of the levelized cost of hydrogen (LCOH) in all studied scenarios. Additionally, optimizing the costs associated with electrolysers, which can exceed 30 % of the LCOH in polymer electrolyte membrane (PEM) electrolysis, is crucial. This optimization is essential for positioning the country as a net exporter of green hydrogen. The range of LCOH values calculated in the different scenarios is between 2.11 USD/kg H 2 and 4.12 USD/kg H 2 . According to updated specialized literature, achieving LCOH values under USD 1.4/kg H 2 is essential for this goal.

The degradation of two textile dye molecules was studied using photochemical processes, both in the absence and presence of light. Various methods were employed, including photolysis/UV, combined H 2 O 2 /UV photolysis, Fe 2+ /UV treatment, Photo-Fenton/UV at 350 nm and Photo-Fenton with solar irradiation. The decolorization efficiency of dyes in aqueous solution was evaluated for two specific dyes: Bromothymol Blue (BTB) and Methyl Green (MG). These experiments were carried out in batch mode. The results demonstrated a synergy between light irradiation and the presence of Fenton’s reagents, such as hydrogen peroxide and divalent iron. In addition, it was demonstrated that direct solar irradiation can be used without specific devices to achieve high efficiency at low cost. In the first part, we checked the impact of the various operating parameters. Reaction efficiencies were compared for the same system in the dark and under the assistance of an artificial or solar light source. In the second part, we studied the parameters of the Photo-Fenton process, such as the initial pH of the solution, the initial concentrations of oxidant, iron catalyst, and dye under irradiation from either light source. Whereas the mere photolysis without Fenton’s reagents allowed decolorization yields below 26 %, addition of the oxidant (H 2 O 2 ) or the catalyst (Fe(II) species amplified the treatment efficiency. However, the presence of both H 2 O 2 and Fe(II) under light irradiation was shown synergetic with yields ranging from 72 to 85 % depending on the dye worked and the light source: because of its broader spectrum in the UV domain, solar irradiation led to the highest decolorization yields. The above results were obtained for well-defined proportions of dye and reagents: for a 20 mg/l dye solution, Fe(II) catalyst concentration equal to 10 −3  M, peroxide concentration of 5.10 −2  M and a pH of 3. These conditions allowed optimal production of OH · radicals, allowing high efficiency in systems using solar irradiation.

Focusing on improving the performance of the hydrogen (H 2 )-based direct reduction shaft furnace (HSF), the current work was undertaken to evaluate the potential benefits of an operation featuring nitrogen (N 2 ) mixing in feed gas using a computational fluid dynamics (CFD) model that describes the in-furnace gas-solid countercurrent reactive flows. A set of simulation cases was carried out under different N 2 flow rates and top pressures. Variation in the latter operating parameter was conducted with the intent to mitigate the issue of H 2 dilution caused by N 2 mixing. The results showed that the in-furnace thermochemical state deteriorates if the N 2 flow rate is inadequate. The state is gradually improved by increasing the N 2 flow rate as more sensible heat is delivered into the process, thereby resulting in better degrees of solid reduction and H 2 utilization. An increase in the top pressure gives rise to higher gas density that enhances the driving force and thus facilitates the reduction reaction. A higher solid reduction degree is consequently achieved by elevating the top pressure. When the top pressure exceeds 5.0 atm, however, the increase in solid reduction degree becomes marginal, while the energy required for compressing the feed gas continues to rise linearly.

The cobalt electrodeposition from a leaching containing cathode-powdery of spent laptop lithium-ion batteries (LIBs) of different commercial brands, collected from local laptop repair shops, was investigated. Citric acid (0.14 M) and hydrazine (0.1 M) were employed as complexing and reducing agents in the leaching during 24 h. Cobalt, manganese and nickel concentrations in the leachate, obtained by the flame method in an atomic absorption spectrometer, are reported. A rotating cylindrical electrode reactor which consists of a rotating open bottom as cathode and a static outer cylindrical as anode was employed. The numerical flow patterns and cathode velocities that induce the presence of Taylor vortices inside and/or outside the cathode were investigated. RANS equations with the standard k−ε turbulence model and enhanced wall treatment was used. Electrical power measurements were performed to validate simulations. Cyclic voltammetry experiments with synthetic solutions were applied to determine the reduction potential of cobalt (found in −1.2 V vs SCE). Subsequently, electrolysis experiments were carried out at predetermined cathode speeds (50, 75, and 125 rpm), imposing a working cathodic potential of −1.2 V versus SCE during 12 h. Experimental results indicate that the best cobalt recovery rates and current efficiency coincide with the presence of Taylor vortices both inside and outside the cathode, i.e., at 50 rpm. The peak performance in cobalt recovery and current efficiency was recorded at 49 % and 47.3 %, respectively. Finally, the deposits obtained from each electrolysis test were removed from the cathode and analyzed via energy dispersive spectroscopy. The range of purity of Co obtained in the electrodeposit film were between 56.75 % and 74.8 %.

In this study, the catalytic reduction of CO 2 into formic acid was investigated over a Ni/Al 2 O 3 catalyst synthesized by wet-impregnation technique. The CO 2 hydrogenation reaction was performed in a slurry reactor in the temperature range of 100–300 °C and at an autogenerated pressure. The Na 2 CO 3 was used as a CO 2 source, and hydrazine hydrate was used as a hydrogen source. The effect of reaction temperature, catalyst metal loading (5–15 wt%), and catalyst amount were optimized for the higher yield of formic acid. The catalyst was very selective to formic acid, and a very high formic acid selectivity of ∼99 % was achieved in the presence of 10 wt% Ni/Al 2 O 3 catalyst at a much lower reaction temperature of 250 °C. The obtained formic acid yield was ∼53.5 %. The result demonstrated that the Ni/Al 2 O 3 catalyst developed was very promising for the selective hydrogenation of CO 2 molecules to formic acid via the in situ  hydrogenation from hydrazine hydrate.

The slag-metal interface serves as a crucial locus for both chemical reactions and the adsorption of inclusions during secondary refining. This study first comprehensively reviews the methods of inclusions removal and then establishes a cold-state experiment using a water-oil system to reappear the phenomenon of slag-metal dispersion and inclusion adsorption. The distribution of slag droplets under varying slag volumes is analyzed in terms of the effect of bottom blow rates. Simultaneously, the volumetric fraction of oxygen on the slag-eye surface is analyzed. The result proved that the increase in oil layer thickness or the gas flow rate increase the volume of entrained oil. The dimensionless depth of entrained droplets was positively associated with gas flow rate or oil thickness. The dimensionless depth of “large droplets” and “small droplets” was in the range of 0–25 % and 0–60 %, respectively. Moreover, analysis of the gas composition above the slag-eye in a water-oil system is used to determine the degree of secondary oxidation. The oxygen volume fraction over the surface of the slag-eye decreases with the increase of gas flow rate. The oxygen volume fraction over the surface of the slag-eye is 1.51 % when the gas flow rate is 9 L/min.