This research examines the stagnation-point flow of a micropolar fluid flowing past a porous, stretching or contracting flat plate, incorporating velocity and thermal slip boundary conditions. The governing partial differential equations are converted into corresponding ordinary differential equations by employing similarity transformations, which are subsequently evaluated numerically by applying a shooting technique. The influence of principal physical parameters on the distributions of velocity, microrotation, and temperature is explored and depicted through graphical representations. Furthermore, computed results for the wall shear stress coefficient and the heat transfer rate across a range of parameter values are provided in tabular format.
Bioethanol is an extremely important raw material on the world market that is used in various industries. The purification processes most commonly used in modern biorefineries include distillation for ethanol extraction, followed by zeolite adsorption for bioethanol dehydration. Both processes are very energy-intensive. Membrane separation processes have significant potential to replace both steps in bioethanol production, which could significantly lower operating costs and reduce production costs. This paper describes the implementation of pervaporation and vapour permeation in the bioethanol dehydration process. The aim is to increase the ethanol concentration from 96% vol. at the outlet of the distillation column to over 99% vol. by using hydrophilic membranes that are able to selectively pass water molecules and thus remove them from the bioethanol. Based on the existing literature, the study determines the optimal process parameters such as temperature, pressure, flow rate, and pressure on the permeate side. Furthermore, the performance of different organic, inorganic, and composite membranes is presented, and the maintenance of these parameters, as well as the decreasing performance of the materials during prolonged use, is discussed.
Biodiesel is a key fuel for a zero-carbon future. Enzymatic synthesis using renewable materials can make it even more environmentally friendly. However, high enzyme costs and limited reuse hinder its economic feasibility. This study assessed the techno-economic and environmental performance of different processes for ethyl ester biodiesel production. The scenarios evaluated include: transesterification of soybean degummed oil using free and immobilized Eversa Transform 2.0, chemical alkaline catalysis of soybean oil, and transesterification of waste oil using ET. The main metrics were net present value and global warming potential. Results showed that the free enzyme outperformed the immobilized enzyme economically. However, chemical catalysis had an NPV nearly double that of the best free enzyme option. Sensitivity analysis revealed that enzyme cost and reuse rate were critical to net present value. Transesterification of waste oil with enzyme reuse had the lowest GWP (4.21 g CO2eq/MJ), making it the most environmentally favorable scenario. While life cycle assessment indicated lower global warming potential for enzymatic catalysis, further study is needed on emissions from enzymes. Depending on the enzyme and reuse rate, chemical catalysis might result in lower overall emissions. Integration with the biorefinery makes large-scale enzymatic biodiesel production economically viable and with low CO2eq emissions.
This study presents the design and implementation of a Model Reference Adaptive Controller (MRAC) using the Massachusetts Institute of Technology (MIT) rule for a pH neutralization process in a continuous reactor. The inherent nonlinearity of acid-base reactions makes conventional Proportional-Integral-Derivative (PID) control insufficient in handling rapid pH variations. To address this, an adaptive control strategy was proposed, allowing the system to dynamically adjust control parameters based on real-time deviations from the reference model. The adaptation gain (gamma) played a critical role in system stability and performance, with simulations and experimental results confirming that gamma = 0.025 yielded optimal response characteristics. Higher adaptation gains accelerated convergence but introduced oscillations, while lower values slowed the response. MATLAB/Simulink simulations and real-time experimental validation demonstrated that MRAC effectively stabilized the system, achieving faster settling time and improved tracking performance compared to PID control. The findings suggest that MRAC with the MIT rule is a viable alternative for complex nonlinear processes, offering improved robustness against disturbances and set-point variations. Further enhancements, including the Normalized MIT rule and polynomial modeling, could further refine the controller's effectiveness in industrial applications.
This study investigates the potential of Taraxacum officinale (TO) root extract as an environmentally friendly corrosion inhibitor for two types of steel, TH-550 and TS-275, in an acidic environment. The corrosion inhibition was assessed by monitoring the weight loss of steel samples over a 72-hour immersion period four different solutions: blank 4% HCl solution and 4% HCl solutions containing 0.5, 1.0, and 1.5 g/L of TO root extract. The inhibitor efficiency, calculated from weight loss data, ranged from 70% to 89%. Surface analysis of the steel samples, conducted after 24 hours of immersion, revealed the formation of a uniform protective film on the steel exposed to the inhibited solutions, while samples the blank acidic solution showed significant corrosion. Fourier-transform infrared spectroscopy analysis identified key metal-complexing functional groups in the TO root extract, including aromatic C-H, C-O, C=O, and O-H, which are likely responsible for the interaction with the steel surface. Potentiodynamic polarization measurements indicated that the TO root extract acts as an anodic corrosion inhibitor, with the ability to cover up to 88% of the steel surface. Electrochemical impedance spectroscopy, in combination with polarization and weight loss results, demonstrated that the inhibitor efficiency of the TO root extract increases with concentration.
The current study focused on utilizing an advanced modeling technique to create a one-dimensional model to analyze the full-cycle calculation of a compression ignition (CI) engine fuelled with a biodiesel blend to explore its performance and emission characteristics. The developed model is to solve the equations that govern conservation of energy and mass, which is used to find the rapid changes of gas exchange and combustion process as a function of crank angle degree. The combustion chamber was created as a one-dimensional model by simulation software, comprising two distinct zones: burned and unburned gases. Heat release and emission predictions were derived using simplified reaction mechanisms. The developed combustion model was integrated as a sub-model within the cylinder element of the one-dimensional solver, enabling the exchange of critical parameters such as cylinder pressure, mass fraction burned, and heat release rate at each crank-angle increment. The work focused on comparing the peak pressure, heat release rate, oxides of nitrogen, smoke, carbon monoxide, and brake specific fuel consumption of the created model with those of the results obtained from the experimental engine. By comparing the theoretical and experimental results, it was inferred that the theoretical model resulted in comparatively higher peak pressure (41%), higher heat release rate (10.38%), lower carbon monoxide (31%), and lower brake specific fuel consumption (4.7%) than that of the experimental engine for the biodiesel blend. The results of the current study showcased the feasibility of utilizing biodiesel in CI engines with better characteristics, which address the sustainable development goals.
The acidic by-products produced during fermentation can cause a drop in pH, which in turn affects the microorganisms' growth and the product's formation. In order to keep pH at the desired level, process control becomes necessary. The aim of this study is to develop a predictive model for pH behavior during the fermentation of Clostridium acetobutylicum through dynamic analysis and system identification. The First Order Plus Dead Time (FOPDT) model and the second-order Autoregressive Moving Average with Exogenous (ARMAX) model were the two approaches that were compared. While the FOPDT model was used to derive the PID controller parameters through transient analysis, the Smith and linear regression methods, the ARMAX model—identified with the Recursive Least Squares (RLS) method—was chosen for its better accuracy in capturing input-output dynamics. PID tuning was done with the Cohen-Coon method. The simulation results showed that setpoint tracking was successfully done, and the ARMAX model provided a more accurate representation of the system. The optimized PID controller recorded the minimum Integral of Squared Error (ISE) value of 50.82. This study points out effective modeling and control strategies for the production of stable pH during fermentation, thus providing very useful knowledge for other bioprocesses that require precise control.
Erratum to: Synthesis and Characterization of Activated Carbon Produced from Hazelnut Peels by Chemical Activation DOI: 10.2298/CICEQ240807005K Chemical Industry and Chemical Engineering Quarterly 32 (1) (2026) 15–24 Semaa Ibraheem Khaleel University of Mosul, College of Petroleum and Mining Engineering, Department of Petroleum and Refining Engineering, Mosul, Iraq The Editorial Office of Chemical Industry and Chemical Engineering Quarterly strives to ensure the accuracy of all published content. However, it has come to our attention that, due to an unfortunate error, the correct highlights of the above-mentioned article were replaced by incorrect ones. The correct highlights, appearing on page 15, should read as follows: • Activated carbon was prepared from Corylus avellana peels and polymeric waste materials. • Chemical activation was employed in the preparation process. • The properties of the obtained products are superior to those of commercial coal. The Editorial Office sincerely apologizes to the authors and readers for this error and for any inconvenience it may have caused. Link to the corrected article 10.2298/CICEQ240807005K
Electrochemical machining is a non-traditional machining process, especially for difficult-to-cut materials. An electrolyte was prepared with ethylene glycol (EG) 30 vol% and distilled water 70 vol% as a solution with the combination of $\ce{NaNO3}$, and stainless steel electrodes coated with polyvinyl acetate (PVA) and commercially available ceramic paste. Inconel 718 was used as a workpiece material in this study. $L_9$ orthogonal array (OA) experiments are conducted for both sodium nitrate ($\ce{NaNO3}$) and EG+$\ce{NaNO3}$ electrolyte. The process parameters are optimized using Preference Ranking Organisation Method of Enrichment Evaluation (PROMETHEE II) and Artificial Neural Network (ANN). According to the multi-criteria decision-making method, the optimal parameter combination of both electrolytes is stainless steel electrode at 9 V, 70% duty cycle, $28 \, g \cdot L^{-1}$ electrolyte concentration and ceramic coated electrode at 13 V, 80% duty cycle, $28 \, g \cdot L^{-1}$ electrolyte concentration. The results of PROMETHEE II were verified using the developed ANN architecture. ECM performance was significantly improved by adding EG to the sodium nitrate electrolyte. EG significantly improved the material removal efficiency by increasing the average machining rate (MR) by 69.70%. Concurrently, the diametral overcut (DOC) dropped by roughly 27.4%, indicating a significant improvement in dimensional accuracy. Only a slight rise of about 1.6% was seen in the surface corrosion factor (SCF), indicating that the addition of EG has no negative effects on surface integrity.
The plate heat exchanger is one of the smallest and most efficient heat exchangers on the market. This experiment aims to assess the performance of eutectic solvent-water as a base fluid in a plate heat exchanger. For this study, silicon oxide (SiO2) nanoparticles are synthesized from sugar bagasse and rice husk, using the sol-gel method. SiO2 nanoparticles were used in various ratios (0.15 vol.%, 0.3 vol.%, 0.45 vol.%, 0.6 vol.%, and 0.75 vol.%) in a base fluid (15 vol.% eutectic solvent and 85 vol. % water) to prepare a nanofluid. At three different temperatures, such as 323 and 343 K, with varying flowrates (2-8 L/min) and varying nanoparticle concentrations (0.15% to 0.75%), heat transfer studies were performed, and the results are presented. There was a notable enhancement in the overall heat transfer coefficient by the combination of SiO2 nanoparticles and an eutectic solvent-water-based fluid. It was noted that utilizing the SiO2/eutectic solvent-water nanofluid could significantly reduce the temperature gradient in the heat exchanger and improve its performance. The maximum overall heat transfer coefficient noted was 3162.5 W/m2K at 0.6% volume fraction of nanoparticles, with a flow rate of 8 L/min at a temperature of 343 K.
The greener technologies, such as radiation treatment, are gaining worldwide fame due to their promising role in reducing effluent pollution. For the current study, two sources of catechin-based natural colorant in binary form have been appraised for cotton using a statistical approach. Dyeing variables were selected through central composite design under response surface methodology and at dyeing conditions, pre, post, and meta mordanting using eco-friendly anchors. It has been found that 25 mL of the binary extract of pH 9, having 2 g/100 mL of salt at 80°C for 55 minutes after microwave (MW) treatment up to 4 min, has given an excellent yield (K/S = 2.48). Using 1.5% of tannic acid (TA) before dyeing of cotton has given excellent colour strength up to 4.11 K/S, whereas using myrobalan extraction (2%) after dyeing of cotton with binary extract has given better yield (K/S = 2.85) with good colorfastness. It is concluded that a statistical approach in combination with the MW treatment should be used to explore the coloring behavior of plant dyes for cotton under selected conditions, and the addition of eco-friendly additives (mordants) should be used to get colorfast shades.
Electrochemical machining is an important process for fabricating difficult-to-cut materials. Itis a much more advantageous process for creating excellentsurface quality on a wide range of conductive materials. In this research, the electrode (cathode) is coated with less resistive palladium material through a sputtering process, and sodium electrolyte is added with 10 gl-1 ascorbic acid to improve Local electrolysis and reduce the sludge generation. The process parameters, specifically electrolyte concentration, machining voltage, duty cycle, and frequency, were varied on machining rate and overcut using the L27 orthogonal array experimental plan. & Eacute;Limination Et Choix Traduisant la REalit & eacute; (ELECTRE) is employed to find a suitable solution. Based on the ELECTREmethod, the best factor combination is 29 g L-1 electrolyte concentration, 12 V, 70% duty cycle, and 80 Hz frequency. The analysis of variance shows that machining voltage and electrolyte concentration are the considerable factors, with contribution percentages of 43.93% and 23.34%, respectively. As per the mean effect plot, the optimal combination is 29 g L-1 electrolyte concentration, 12 V, 90% duty cycle, and 80 Hz frequency.
This paper focuses on designing an advanced control scheme tailored for largescale industrial processes, where controllers must maintain effective performance despite significant disturbances and setpoint changes. The primary focus of the proposed RTD-A controller is on robust disturbance rejection. RTD-A possesses the benefits of both conventional PID and MPC control schemes. As model-based methods face challenges in addressing increasingly complex processes, data-driven techniques have gained popularity in industrial system monitoring due to their ability to handle unknown physical models. In this work, both the first-principle and transfer function models of the CSTH system are developed using real-time data and represented as a multi-input, multi-output (MIMO) system. PID, MPC, and RTD-A controllers are then applied to regulate the temperatures of the two tanks. The performance of these controllers is carefully examined using integral performance criteria and the time domain analysis to accurately assess their dynamic behavior and control precision. The results demonstrate that the RTD-A controller exhibits superior performance in mitigating disturbances. The RTD-A control strategy exhibits outstanding performance with near-zero overshoot (0% in servo and about 0.05% in regulatory responses) and stable settling times close to 430-440 seconds in both tanks. Although MPC and PID controllers offer quicker responses, their greater overshoot and longer settling times establish RTD-A as the preferred method for achieving reliable, precise, and safe control in industrial processes.
This article presents the architecture and functional principle of an advisory-based product configurator. The program is used to create new and modify similar product configurations and is intended for users without in-depth expertise in technical fields. Due to its architecture, the configurator is designed to utilise the knowledge stored in the knowledge database. The selection is based on a combination of fuzzy inference rules and mapping techniques. Knowledge regarding the product is captured by using component-based matrices. The possibility of adding new knowledge and new rules is also provided. All this enables the configurator to link customer requirements and offers the possibility of selecting one or more products. In addition, it evaluates possible product variants based on the parameters specified by the user. The graphical representation of the results obtained includes the product technical documentation as well as a matrix representation of all the selected components andmodules. The functional principle and evaluation of the product selection are demonstrated using a case study of a chiller for installation in an industrial plant. During the selection and evaluation of the chiller, better system performance is achieved with a chiller that has a water-based condenser.
The aim of this study is to optimize the drying conditions for yellow carrots by investigating the effects of varying infrared (IR) power levels on drying kinetics. Following drying tests at IR power levels of 38, 50, 62, 74, and 88 W, the initial moisture content of carrot slices (6.95 kg water/kg dry matter) was decreased to 0.11 kg water/kg dry matter. Drying times ranged from 300 minutes at 38 W to 110 minutes at 88 W, demonstrating an inverse relationship between IR power and drying duration. Higher IR power levels accelerated the drying rate by enhancing energy transfer, which promoted moisture removal efficiency. Effective diffusion coefficients, calculated as ranging from 7.73x10-10 to 2.21x10-9 m2/s for the power levels of 38 W to 88 W, indicate an increase in moisture migration with higher power. The processs'energy requirements were reflected in the activation energy for moisture diffusion (1.967kW/kg). The Midilli and Kucuk model offered the best fit for characterizing the drying behaviour, and statistical analysis validated the model's correctness. These findings provide valuable insights for optimizing IR drying conditions to enhance the efficiency and quality ofyellow carrot drying processes.
This study examines the combustion and performance of avocado waste peel biodiesel (AWPB) combined with graphene oxide nanoplates (GONPs) as a substitute fuel for diesel engines. It also aims to assess the impact of engine combustion and performance while considering the feasibility of employing waste materials in fuel generation. The test fuels diesel, AWPB, AWPB+GONPs 50 ppm, and AWPB+GONPs 100 ppm were evaluated. The results showed that-cylinder pressure in AWPB decreased by approximately 3.6% compared to diesel, while the heat release rate (HRR) increased notably in the AWPB+GONPs 100 ppm blend. Additionally, diesel exhibited higher ignition delay (ID) and combustion duration (CD) than all biodiesel blends. The addition GONPs in AWPB led to a 5.98% increase in brake thermal efficiency (BTE) and a 30.12% reduction in brake-specific energy consumption (BSEC) compared diesel. However, diesel still demonstrated higher engine torque, indicated mean effective pressure (IMEP), and air-fuel ratio (A/Fratio) relative to biodiesel fuels, whereas AWPB showed a higher exhaust gas temperature (EGT). These findings suggest that avocado peel biodiesel, when enhanced with GONPs, is a viable and cleaner alternative to conventional diesel, offering improved combustion efficiency and reduced energy consumption.
This study employs density functionaltheory (DFT) to quantify the electron donor-acceptor properties and polarizability of organic iron(II) salts as reducing agents in indigo dyeing processes. The potential of some iron(II) salts to serve as environmentally friendly alternatives to the ecologically harmful sodium dithionite in the indigo dyeing process was investigated. A comparative analysis assessed the redox potential of reduced indigo and the color strength of dyed fabrics. Experimental results identified iron(II) gluconate as the most efficient, yielding superior color intensity. Theoretical calculations using B3LYP/LANL2DZ confirmed the superior electron-donating ability of iron(II) gluconate compared to the other iron(II) salts. The indigo reduction ability with the iron(II) salts was evaluated on the basis ofcomplexation energies. The theoretical thermodynamic study reveals that the indigo-iron(II) gluconate complex is the most thermodynamically stable, requiring less energy input for its formation compared to the other complexes. Iron(II) salts-to-indigo electron donations in the complexes studied have been revealed by Mulliken charge analysis. These findings highlight the efficiency of DFT-based approaches in accurately predicting the reducing capacity ofiron(II) salts and their suitability as eco-friendly alternatives in indigo dyeing applications.
The traditional kombucha beverage is produced through the metabolic activity of the microorganisms present in the kombucha culture on sweetened black tea at room temperature. The aim of this study was to investigate the influence of cross-flow microfiltration on the quality of the produced beverage. The produced beverage was microfiltered to assess the effect of cross-flow microfiltration on its quality. The quality characteristics examined included pH, total acidity, total soluble solids, turbidity, organic acids, in vitro antioxidant potential, and vitamin C as an antioxidant compound. The operational parameters of the process were transmembrane pressure (0.2, 0.6, and 1 bar) and feed flow rate (30, 90, and 150 Lh-1). The maximum permeate flux was achieved at the highest feed flow rates and transmembrane pressures. Microfiltration maintained (pH, total acidity, total soluble solids, lactic, formic, and oxalic acid), improved (turbidity and acetic acid), but also declined (malonic acid, vitamin C, and antioxidant potential), the quality of the traditional beverage. After the microfiltration, turbidity was reduced by 7-9 times, and the content of acetic acid amounted to around 1.20 g/L. The lowering of acetic acid content indicated the inhibition of acid buildup. Values of the coefficient of retention for all of the examined quality parameters, except turbidity, suggested that the overall influence of microfiltration was moderate.
This study focused on producing a natural bio-coagulant from moringa seeds. Moringa seed extract is a natural coagulant for the treatment of water containing suspended solids and colloids and is obtained through grinding, oil extraction, protein extraction from the solids using 2 M NaCl solution, protein separation by centrifugation followed by filtration. This study investigated the production and use of bio-coagulants. Parameters investigated when producing the bio-coagulant include the effects of temperature on the removal of moisture content in the moringa seeds, the type of solvent on the oil yield, and varying the volume of n-hexane for oil extraction. Parameters investigated when using the bio-coagulant include the effect of dosage of bio-coagulant on pH and turbidity removal efficiency, and the performance of the bio-coagulant at low, medium, and high turbidity levels. The optimum temperature and time obtained by drying the moringa seeds was at 100oC for 30 min and the highest oil yield obtained was 31% when using n-hexane as the solvent. Turbidity removal efficiency went up to 96.4% when using 50 mg/L of the bio-coagulant at a pH of 6.1. High turbidity removal was achieved at low bio-coagulant dosages which was regarded as a breakthrough finding for this research.
This study explores the degradation of polyurethane (PU) using deep eutectic solvents (DES) combined with ultrasonic irradiation, aiming to develop sustainable recycling techniques for PU waste. DES, formed from choline chloride and urea, possesses environmentally friendly properties such as low toxicity and high solubility, making it suitable for chemical recycling. Degradation experiments were conducted at elevated temperatures (130-150 degrees C), both with and without ultrasonic assistance. The technique of GPC is applied to determine the molecular weight of raw PU and the degradation product. The structures of DES, PU, and its degradation products were analysed using FTIR and NMR. The results indicate that the application of ultrasonics significantly enhances the degradation rate at approximately 5.20% from 58.51 +/- 0.04% to 63.71 +/- 0.03% ata constant temperature of 150 degrees C. This improvement is attributed to cavitation-induced effects, which facilitate polymer chain breakdown. Molecular transformations were confirmed through the presence of NH3 groups resulting from the break of the PU structure to form o-toluidine, as identified by NMR. Reaction pathways were established through structural analysis of both raw PU and its degradation products. These findings demonstrate the potential of ultrasonic-assisted DES in advancing chemical recycling strategies for PU, addressing environmental concerns related to persistent PU waste, and promoting sustainable waste management practices.
