ChemEngineering

Thermal effects of adsorption and desorption, leading to temperature fluctuations and losses of adsorption storage systems capacity in the processes of gas charging and discharging, are the main obstacle to the wide practical application of adsorbed natural gas (ANG) technology. This work presents a numerical simulation of heat and mass transfer processes under various cyclic operation modes of a full-scale adsorption storage tank with various thermal control systems. The high-density monolithic adsorbent KS-HAM, obtained on the basis of industrial activated carbon KS-HA, was used as the adsorption material. The phase composition, surface morphology, and porous structure of the sorbents were studied. The adsorption of methane on the KS-HA adsorbent was measured. It is shown that increasing the duration of charging leads to obtaining additional capacity of the ANG system; however, the final efficiency and benefit at the end of the charging–discharging cycle are determined by the efficiency of the thermal control system and the gas-discharging mode. It has been shown that the presence of a finned thermal control system allows for charging the adsorption storage tank 3–8 times faster and provides an 8–24% greater amount of gas discharged at the discharging stage compared to the ANG system without fins. Full article

This paper presents a plantwide control strategy for optimizing a pressure-swing azeotropic distillation process used in tetrahydrofuran dehydration. Leveraging Skogestad’s methodology, this strategy focused on two distillation columns: a low-pressure column for water recovery at 20 psia and a high-pressure column that achieved 0.99 molar fraction purity of tetrahydrofuran at 115 psia. This study identified critical control variables through plant analysis by implementing PI controllers in the regulatory control layer to stabilize flows and pressures. In the supervisory control layer, a PI controller combined with MIMO MPC effectively enhanced the product purity and reduced the energy consumption by 36%. Stable inlet and outlet flow conditions (100 lbmol/hr inlet, 29.59 lbmol/hr outlet) were maintained without compromising the equipment integrity. The operational ranges for the process included variations in the tetrahydrofuran mole fraction from 0.25 to 0.35 at the inlet, which demonstrated a robust performance across perturbations. These achievements signify significant advancements in process efficiency and sustainability, offering substantial reductions in energy usage while ensuring consistent high purity levels in tetrahydrofuran production. The developed control structure sets a new standard for efficient azeotropic distillation processes, with implications for enhancing operational performance across industrial applications. Full article

Sustainability requirements must be met by the appropriate selection of efficient and environmentally friendly materials and processes. We present materials obtained via all-in-water methods: first, few-layer graphene (FLG)–polyvinyl alcohol (PVA) colloids and then electrospun PVA-FLG fibers. The effects of the FLG concentration, and indirectly of ultrasound, are reflected via the modification of the structural and physical properties, including the microstructure, viscosity, thermal degradation and mechanical properties, of colloids and fiber mats. The primary results are highly encouraging for further optimization and the development of conductive, and mechanically resistant, materials. Full article

The thermal decomposition of a heat-not-burn (HNB) tobacco at four temperatures (250–400 °C) was studied via thermogravimetric analysis (TGA) and Multi-shot pyrolizer experiments (Py-GC/MS), and the effect of four potential additives, USY Beta and beta zeolites and Silica Lovel 6000 and SBA-15 silicates at three concentrations (5, 15 and 25% w/w) under an inert and oxidative atmosphere was analyzed. Different techniques were applied showing that the presence of the additives modifies the decomposition processes (TGA). Py-GC/MS showed that these tobaccos generate large amounts of Nicotine and Glycerine. Acid compounds are the most abundant compounds under an inert atmosphere, while Oxygenated compounds predominate under an oxidative atmosphere. In both atmospheres, Furans and Aromatics present in a significant abundance at high temperatures. The additives used reduce both the number and the concentration of most of the compounds generated, especially at high temperatures and concentrations. Moreover, SBA-15 shows good aptitudes to reduce the formation of some individual compounds included in the FDA’s HPHC list, such as Acetone and Acetaldehyde. Finally, smoking experiments corroborated that all additives produce marked reductions in TPM, i.e., the majority fraction obtained, and in practically all the compounds generated. Phenol, a toxicant compound that was detected in a significant amount, is also markedly reduced. SBA-15 is the material that presents a major reduction in the TPM and the principal compounds generated. These results may be of great interest for further reducing the toxicity of smoking this type of heat-not-burn tobacco product. Full article

Gas hydrate inhibition using chemicals has been under continuous investigation, and several modelling studies have been published since its inception. Since it is not always feasible to conduct experimental research, it is especially crucial to forecast the conditions under which gas hydrates may form and dissociate in the presence of chemical inhibitors. As a result, a reliable forecasting tool is vital. This article provides an exhaustive review of various modelling methodologies in the context of gas hydrate chemical inhibition. The key aspects of empirical models, thermodynamic models, kinetic models, artificial intelligence-based models and quantum chemistry-based models are presented. Critical analysis of each modelling approach has been performed, highlighting strengths, limitations, and areas where further investigations are still crucial. Rapid progress has been made with respect to gas hydrate modelling approaches in the context of chemical inhibition; however, further research is still vital to bridge the gaps that have been identified in this review. Potential improvements to existing models have been proposed, particularly in terms of integrating experimental data and utilizing hybrid approaches, which could serve as valuable future directions for the field. Full article

This research delved into the energetic properties of catalysts synthesized from residual sludge from the textile, galvanic, and tannery industries. The experimental process consisted of an initial heat treatment to activate their catalytic properties and a thermal analysis employing differential scanning calorimetry (DSC). This technique permitted the investigation of the materials’ thermal behavior as a function of temperature, ranging from 142 to 550 °C, effectively controlling the heating rates and pressure conditions. The data gathered were the input for constructing specific heat models through polynomial regression employing the least squares method. These models were subsequently used to estimate variations in the enthalpy and entropy for both the sludge and catalysts through integration. Third-degree polynomials primarily characterized the specific heat models that accurately represented the samples’ thermal behavior, considering variations in their physicochemical properties that influenced it. The catalysts derived from residual sludge from the textile industry exhibited the models with the most robust statistical fit. Concurrently, the catalysts from the galvanic industry displayed noteworthy similarities with the bibliographic data across various temperature points. The mathematical models determined the specific heat (Cp) as a function of temperature, which, in turn, was used to estimate the enthalpy and entropy variations in the sludge and catalysts under study. The highest enthalpy value corresponded to the sludge and catalyst obtained from the tannery industry, with a Cp of 5.60 J/g-K at 603 K and 2.45 J/g-K at 445.6 K. Finally, the third-degree polynomials showed the best mathematical models since (1) they considered the variations in the physicochemical properties that intervened in the behavior of Cp as a function of temperature; (2) they presented a better statistical fit; and (3) they showed consistency with the existing information in the literature for the textile industry and the galvanic industries. Full article

In recent decades, the global use of ashes derived from agro-industrial by-products, such as oil palm kernel shells, which are widely cultivated in Colombia and other tropical regions of the world, has increased. However, the application of these ashes in engineering remains limited due to their heterogeneity and variability. This study utilized scanning electron microscopy (SEM) to assess the influence of calcination temperatures, ranging from 500 °C to 1000 °C, as well as the physical processes of cutting, grinding, and crushing, on the silica content of the studied ashes. Specifically, the sample labeled M18A-c-m-T600°C-t1.5h-tr1h, which was subjected to a calcination temperature of 600 °C and underwent cutting and grinding before calcination, followed by post-calcination crushing, exhibited the highest silica concentration. Complementary techniques such as X-ray fluorescence (XRF) and X-ray diffraction (XRD), were applied to this sample to evaluate its feasibility as an additive or partial replacement for cement in concrete. XRF analysis revealed a composition of 71.24% SiO₂, 9.39% Al₂O₃, and 2.65% Fe₂O₃, thus, meeting the minimum oxide content established by ASTM C 618 for the classification as a pozzolanic material. Furthermore, XRD analysis confirmed that the sample M18A-c-m-T600°C-t1.5h-tr1h is in an amorphous state, which is the only state in which silica can chemically react with calcium hydroxide resulting from the hydration reactions of cement, forming stable cementitious products with strong mechanical properties. Full article

The ongoing anthropogenic climate crisis necessitates a reassessment of numerous technical domains, including the energy sector. An alternative to conventional fuel cells is provided by photo fuel cells, which possess at least one photoactive electrode (e.g., TiO₂). However, it should be noted that such fuel cells are often constrained in terms of the range of potential fuels that can be utilized. Considering prior research on the distinctive photochemistry of europium, it was hypothesized hypothesis that a photocell based on the photo-oxidation of diverse organic compounds by trivalent europium might be theoretically feasible. As demonstrated in multiple experiments, it is feasible to construct and operate a fuel cell utilizing these diverse, straightforward substrates. In this context, peak powers of up to 14 μW have already been observed with the fuel cell described. It is noteworthy that an average electrical power of up to 6.28 μW was observed over a period of 168 h (7 days). Furthermore, it was demonstrated that simple alcohols (ethanol) could be completely oxidized with trivalent europium under suitable conditions. From various studies with different ethanol concentrations, it could be seen that a certain amount of water was needed to break down simple alcohols and organic compounds in general. Full article

Redox flow batteries (RFBs), with distinct characteristics that are suited for grid-scale applications, stand at the forefront of potential energy solutions. However, progress in RFB technology is often impeded by their prohibitive cost and the limited availability of essential research and development test cells. Addressing this bottleneck, we present herein an open-source device tailored for RFB laboratory research. Our proposed device significantly lowers the financial barriers to research and enhances the accessibility of vital equipment for RFB studies. Employing innovative fabrication methods such as laser cutting, 3D printing, and CNC machining, a versatile and efficient flow cell has been designed and fabricated. Furthermore, our open laboratory research equipment comprises the Opensens potentiostat, charge/discharge testing devices, peristaltic pumps, and inexpensive rotating electrodes. Every individual element contributes significantly to the establishment of an all-encompassing experimental configuration that is both economical and efficient, thereby facilitating expedited progress in RFB research and development. Full article

The rheological properties and sedimentation phenomena in fruit purees are of particular importance for the food industry and product acceptance by consumers. The aim of this study was to correlate the phase separation with the underlying mechanisms. First, the influence of soluble solids content and temperature on the flow properties of peach puree was determined. Furthermore, considering the fruit puree matrix as a colloidal dispersion, the sedimentation rate, particle size and zeta potential were also determined. The peach puree samples exhibited pseudoplastic behavior, which was effectively described by the power law model. Both the flow consistency coefficient and apparent viscosity increased as the concentration rose. On the contrary, viscosity decreased as temperature increased. In addition, there was no significant effect of temperature on the flow behavior index. Low zeta potential values resulted in sedimentation as expressed by the phase separation index, and the highest sedimentation rate was observed for the sample with the lowest sucrose content. Full article

Heavy metal pollution is a worldwide and stringent concern following many decades of industrialization and intensive mining without (in some cases) consideration for environmental protection. This review aims to identify the existing and emerging techniques for heavy metals (HM) removal/recycling from water and wastewater, with an emphasis on cobalt. Unlike many other heavy metals, cobalt has not been considered a detrimental element for the environment and human beings until recently. Thus, several methods and applicable techniques were evaluated to identify the best treatment approaches applicable to cobalt-polluted water and wastewater. The most feasible depollution methods adapted to the source, environment, and economic conditions were investigated and concluded. The operations and processes presented in this paper are conventional and innovative as well, including precipitation, membrane separation, with emphasis on ultrafiltration (UF) and nanofiltration (NF), but also reverse osmosis/forward osmosis (RO/FO), sorption/chemisorption processes, flotation/mechanical separation operations combined with coagulation/flocculation, photocatalysis, and electrochemical processes. For each one, depending on the frequency of use, physicochemical mechanisms and optimal operational conditions were identified to carry out successful cobalt removal and recovery from aqueous environments. Full article

Due to the complex relationship between various parameters affecting gas holdup in bubble column reactors, a unique correlation for gas holdup does not exist. The available correlations proposed in the literature for gas holdup prediction in aqueous alcohol solutions in bubble columns fail to predict gas holdup over a wide range of conditions. Therefore, based on around 1000 data points from the previous studies, an empirical correlation and a trained model were derived using the dimensionless numbers Reynolds, Froude, Eötvös to Morton ratio, and alcohol carbon number. The predictions were compared to experiments with different water–alcohol mediums at various concentrations to validate the correlation and trained model, and a good agreement was observed. However, the ML model was predicting more accurately, and it was indicated that the Reynolds number had the most significant impact on gas holdup, followed by the Eötvös to Morton ratio. Full article

Hydrogen has the potential to decarbonize the energy and industrial sectors in the future, mainly if it is generated by water electrolysis. The proton-exchange membrane water electrolysis (PEMWE) system is regarded as a propitious technology to produce green hydrogen from water using power supplied by renewable energy sources. It offers many benefits, such as high performance, high proton conductibility, quick response, compact size, and low working temperature. Many conceptual and functional parameters influence the effectiveness of PEM, including temperature, pressure of anode and cathode regions, water content and wideness of the layer, and cathode and anode exchange current density. In addition, the anodic half-reaction (known as the oxygen evolution reaction (OER)) and cathodic half-reaction (known as the hydrogen evolution reaction (HER)) perform an important function in the development of PEMWE. The current study aims to present these parameters and discuss their impacts on the performance of PEM. Also, the PEM efficiency is presented. The different methods used to enhance the scattering of OER electrocatalysts and minimize catalyst loading to minimize the price of PEMWE are also highlighted. Moreover, the alternative noble metals that could be used as electrocatalysts in HER and OER to minimize the cost of PEM are reviewed and presented. Full article

This study presents an integrated approach that combines the Levenberg–Marquardt (LM) and Luus–Jaakola (LJ) algorithms to enhance parameter estimation for various applications. The LM algorithm, known for its precision in solving non-linear least squares problems, is effectively paired with the LJ algorithm, a robust stochastic optimization method, to improve accuracy and computational efficiency. This hybrid LM-LJ methodology is demonstrated through several case studies, including the optimization of MESH equations in distillation processes, modeling controlled diffusion in biopolymer films, and analyzing heat and mass transfer during the drying of cylindrical quince slices. By overcoming the convergence issues typical of gradient-based methods and performing global searches without initial parameter bounds, this approach effectively handles complex models and closely aligns simulation results with experimental data. These capabilities highlight the versatility of this approach in engineering and environmental modeling, significantly enhancing parameter estimation in systems governed by differential equations. Full article

Using amine-based solutions is a mature method for CO₂ capture. This study simulates this process at Technology Centre Mongstad (TCM) using a rate-based model in Aspen Plus. The main purpose is to develop a rigorous model for TCM and find the operation limits, maximum utilization capacity, and maximum achievable CO₂ removal efficiency at the plant. The model accuracy is verified by using different scenarios from the test campaign reports at TCM with three main configurations: Combined Heat and Power flue gas, Refinery Residue Fluid Catalytic Cracker flue gas, and cold rich-solvent bypass. The deviation between the experimental data and simulation results is compared. The model shows better accuracy with more detailed input data and accurate practical parameters. The verified model is used with all the TCM configurations to simulate the plant. Aspen Exchanger Design and Rating is also used to design real heat exchangers. To avoid flooding, the maximum gas flow to the absorber column is 52,000 Sm³/h. There is a maximum reboiler duty of 8.4 and 3.4 MW for the Residue Fluid Catalytic Cracker and the Combined Heat and Power flue gas strippers, respectively. The optimum operating condition to achieve a CO₂ removal efficiency of 90% after amine lean loading adjustment, using maximum gas flow, both strippers, and 15% rich-solvent bypass, gives a total specific reboiler duty of 3.0 MJ/kgCO₂. By using a maximum amine flow rate of 230 ton/h, a CO₂ removal efficiency of 98% can be achieved. The optimum modification gives a bypass fraction of 19% and a specific reboiler duty of 3.63 MJ/kgCO₂. Full article

The advanced quality control of the raw mix remains a priority for the cement industry, particularly in recent years, where large quantities of alternative fuels and raw materials are used in clinker production, aiming to reduce the CO₂ footprint. This study presents an adaptive control system with a variable sampling period for regulating raw mix quality in the raw mill (RM) output in a process with four independent inputs and four outputs: the lime saturation factor (LSF), silica modulus (SM), alumina modulus (AM), and SO₃. The three pillars of the system are (1) mill dynamics calculation using exclusively industrial data, (2) the design of the controllers to meet robustness criteria, and (3) performance enhancement through simulators. Our technique periodically adjusts the gains of the controllers based on the mill’s dynamic parameters, which are computed from raw mix laboratory analyses. The presented results correspond to more than 14,000 h of mill operation. The standard deviation of the LSF at the mill outlet ranged from 1.5 to 3, which is equivalent to 1 to 2 standard deviations of LSF reproducibility. The standard deviation of the other moduli was close to the corresponding reproducibility of each. The presented adaptive gain-scheduling controller for LSF can be applicable to a broad range of raw meal grinding systems. Full article

The agriculture and agri-food sectors produce substantial amounts of plant-based waste. This waste presents an identifiable research opportunity to develop methods for effectively eliminating and managing it in order to promote zero-waste and circular economies. Plant-based waste and by-products are acknowledged as valuable sources of bioactive compounds, including cellulose fibers. Direct application of these fibers in non-food sectors such as textiles can reduce the environmental impact of secondary raw materials. This review aims to provide an overview of novel concepts and modern technologies for efficiently utilizing plant-based waste and by-products from the agricultural and agro-industrial sectors to extract fibers for a variety of final applications, including the fashion industry. Two major routes are identified to produce cellulose fibers: the extraction and purification of natural cellulose fibers and the extraction and purification of cellulose pulp that is further processed into manmade cellulosic fibers. Scalability of experimental results at the laboratory or pilot level is a major barrier, so it is critical to develop closed-loop processes, apply standardization protocols, and conduct life cycle assessments and techno-economic analyses to facilitate large-scale implementation. Full article

Although the most promising applications of ionogels require their contact with aqueous media, few data are available on the stability of ionogels upon exposure to water. In this paper, a simple, easy-to-setup and precise method is presented, which was developed based on the continuous conductivity measurements of an aqueous phase, to study the washout of imidazolium ionic liquids (IL) from various silica-based ionogels immersed in water. The accuracy of the method was verified using HPLC, its reproducibility was confirmed, and its systematic errors were estimated. The experimental data show the rapid and almost complete (>90% in 5 h) washout of the hydrophilic IL (1-butyl-3-methylimidazolium dicyanamide) from the TMOS-derived silica ionogel. To lower the rate and degree of washout, several approaches were analysed, including decreasing IL content in ionogels, using ionogels in a monolithic form instead of a powder, constructing ionogels by gelation of silica in an ionic liquid, ageing ionogels after sol–gel synthesis and constructing ionogels from both hydrophobic IL and hydrophobic silica. All these approaches inhibited IL washout; the lowest level of washout achieved was ~14% in 24 h. Insights into the ionogels’ structure and composition, using complementary methods (XRD, TGA, FTIR, SEM, NMR and nitrogen adsorption), revealed the washout mechanism, which was shown to be governed by three main processes: the diffusion of (1) IL and (2) water, and (3) IL dissolution in water. Washout was shown to follow pseudo-second-order kinetics, with the kinetic constants being in the range of 0.007–0.154 mol⁻¹·s⁻¹. Full article

Agro-industries produce over 2 billion tons of agricultural waste annually, including by-products like bagasse, molasses, seeds, stems, leaves, straw, and shells. The use of agro-industrial waste is a way to reduce the impact of industrial processes on the environment. The pea pod is a biomass with a high concentration of cellulose, hemicellulose and some lignin; therefore, it can be used to produce platform chemicals by means of a hydrothermal process. There is limited research on the hydrolysis of pea biomass, but it has been shown to obtain high yields. This study analyzed the effectiveness and selectivity of the hydrothermal process using pea pod biomass with a particle size of 0.5 mm at 180 °C for one hour. A 500 mL reactor was used, with a biomass-to-acid solution ratio of 1:20. The concentration of the acid solution was 0.02 M. The concentrations of sugar, formic acid, levulinic acid, HMF, and furfural produced were measured. Among the catalysts studied, adipic acid catalysis showed the highest yield of 65.16%, with 37.09% of sugar, 16.37% of formic acid, and 11.71% of levulinic acid. On the other hand, the catalysts with chloroacetic acid, butyric acid, anthranilic acid, and phthalic acid were less effective but demonstrated selectivity for sugar production, proving that the liquid phase obtained using the catalyst with those acids can be used as carbon sources for a fermentation process. In general, when comparing the process with or without the use of a catalyst, it is observed that with a catalyst in the reaction, the amount of HMF and furfural produced is reduced and the selectivity with respect to sugar production is increased. Full article