The partial oxidation of methane (POM) is an attractive route for syngas production. However, Ni-based catalysts often suffer from deactivation due to carbon deposition, metal sintering, and unstable metal–support interactions. In this study, the influence of zirconia (ZrO2) source and selected oxide promoters on the performance of Ni/ZrO2 catalysts in POM was investigated. A series of 5 wt.% Ni catalysts were prepared using ZrO2 supports from five commercial sources with different crystalline phases and textural properties. The best-performing support was further modified by co-impregnation with 10 wt.% Al2O3, TiO2, and Y2O3. The catalysts were characterized using physicochemical techniques and evaluated in a fixed-bed reactor at 600°C under CH4/O2 = 2.0 (GHSV = 14,400 mL·g−1·h−1). Raman spectroscopy and transmission electron microscopy were used to examine carbon deposition on spent catalysts. The results showed that the crystalline phase and textural properties of ZrO2 influenced the catalytic performance. Among the unpromoted catalysts, Ni supported on DK-type monoclinic ZrO2 exhibited the highest CH4 conversion (52.2%) and H2 yield (51.4%), which was associated with improved Ni accessibility and moderate metal–support interactions. The introduction of oxide promoters further enhanced the activity, with Y-promoted Ni/ZrO2 achieving the highest performance (60% CH4 conversion and 58.2% H2 yield). XPS and H2-TPR analyses suggested an increased contribution of interfacial Ni–O–Zr species together with enhanced reducibility for the Y-promoted catalyst. These results indicate that both the ZrO2 source and promoter type influence the balance between Ni dispersion, reducibility, and catalytic performance in POM.
Macroscopic convection is severely limited in low-permeability reservoirs, and aqueous-phase chemical reactions are frequently neglected in existing CO2 miscible flooding models. To address these gaps, this study develops a diffusion–reaction coupled model that simultaneously tracks five distinguishable components—CO2, oil, miscible mixture, carbonic acid, and water—and couples the reversible CO2–water–carbonic acid reaction with multiphase mass transfer. A water-saturation-dependent dynamic diffusion coefficient is introduced to characterize spatial variations in effective diffusion capacity. Numerical results show that all concentration fronts advance at a t scaling, confirming diffusion-dominated transport consistent with analytical solutions and pore-scale simulations. The dynamic diffusion coefficient improves the continuity and spatial stability of the miscible front and broadens the effective oil mobilization range. The reversible CO2–water–carbonic acid reaction buffers local concentration gradients, producing a cooperative “diffusion–reaction buffering–rediffusion” migration pattern; it acts as an internal regulator rather than replacing diffusion as the dominant mechanism. Validation against analytical solutions, literature trends, and mass conservation confirms the model’s physical consistency. This framework offers a theoretical basis for mechanistic studies and parameter optimization of CO2 miscible flooding in low-permeability and tight reservoirs.
The efficiency and durability of a membrane are closely linked to the fiber extraction process. This study aimed to conduct a comparative analysis of membranes made from Ronier fibers extracted using various methods (mechanical and chemical treatments with acid and alkali). Fibers extracted by these three methods were examined for extraction yield, absorption capacity, and breaking force. A hydrodynamic evaluation in a filtration pilot plant was carried out to characterize the membranes in terms of porosity, permeability, and membrane resistance. Filtration tests of a 20-NTU suspension were conducted to assess the efficiency of the membranes. The results revealed fiber extraction yields of around 5.40%, 11.90%, and 9.90%, breaking forces of 6 N, 10 N, and 12 N, and absorption rates of 90%, 60%, and 70%, respectively, for mechanical, alkaline, and acidic extraction processes. The hydrodynamic characteristics of the three membranes showed porosities of 0.50, 0.35, and 0.45, and permeabilities of 0.416∗10−5, 1.75∗10−5, and 1.25∗10−5 m3/s.m2⋅Pa, respectively, for mechanical, alkaline, and acidic extraction processes. For the three membranes, the residual turbidities after filtration were established at 7.50, 1.50, and 2.30 NTU, respectively. Based on this preliminary study, the results highlight the strong potential of the sodium hydroxide–treated membrane in water treatment, particularly due to its improved clarity compared to other membranes.
Fixed-bed reactors are widely employed in chemical processes because of their operational stability and high catalyst-loading capacity. However, their performance is often constrained by complex flow behavior within the packed bed. In this study, particle-resolved computational fluid dynamics was coupled with the discrete element method to construct fixed-bed reactor structures comprising spherical particles. The effects of the bed-to-particle diameter ratio (N), bed height-to-diameter ratio (H), and standard deviation of the particle-size distribution (STD) on the flow characteristics were systematically investigated. High-precision three-dimensional numerical simulations were conducted to elucidate the formation mechanism of the flow nonuniformity within the packed bed. Further, response surface methodology was employed to develop predictive models for the dimensionless variance. The results indicate that increasing N and reducing STD are crucial to flow uniformity enhancement. Overall, this study provides a theoretical basis and quantitative data support for the structural design and optimization of fixed-bed reactors.
Arsenic is a carcinogenic metalloid prevalent in groundwater, predominantly as As (III), the most toxic and recalcitrant species. This study evaluates a hybrid strategy coupling hydrodynamic cavitation (HC) oxidation of As (III) to As (V) with subsequent adsorption on FeCl3-modified activated carbon. HC oxidation followed a pseudo-first-order kinetic model (k = 3.02 × 10−2 min−1; R2 = 0.9754), with optimal conditions of 4 bar inlet pressure and pH 4. Adsorption equilibria were described by the Langmuir model for commercial carbon (CC), qmax = 1.99 mg·g−1, and by the Freundlich model for modified commercial carbon (MCC), KF = 0.49055 (mg·g−1) (L mg−1)1/n. Kinetics for both adsorbents were best fitted by the pseudo-first-order model (k1 = 0.08876 min−1 for CC and 0.1674 min−1 for MCC). The integrated process, HC pre-oxidation followed by MCC adsorption, improved arsenic removal by 34.68% relative to conventional adsorption. Findings support HC-assisted oxidation coupled with adsorption on Fe-modified carbon as an efficient, eco-friendly, and cost-effective option for treating waters with elevated As (III)/As (V) levels.
Paracetamol (PCM) is extensively used for the treatment of various diseases and is frequently released into aquatic environments, resulting in considerable environmental concerns. In the current study, UV, UV/H 2 O 2 , and photo‐Fenton approaches were applied for the degradation of PCM. The removal of PCM (10 mg/L) was achieved to be 11.2% by UV alone, after 60 min of irradiation. However, the UV/H 2 O 2 system degraded 91.4% of PCM after 60 min at pH 6.0, demonstrating that the combination of UV and H 2 O 2 (5 mM) significantly improved the removal efficiency of PCM. Moreover, the addition of Fe 2+ (1 mg/L) to the UV/H 2 O 2 system further enhanced the degradation of PCM, obtaining 100% removal at pH 3 after 45 min of reaction. The UV/H 2 O 2 process showed higher efficiency at 6.0 than at pH 3.0 and 11.0, as evident by the respective k obs values of 0.0331, 0.0437, and 0.0279 min −1 .However, compared to pH 6.0, the UV/H 2 O 2 /Fe 2+ process showed greater reactivity at pH 3.0. Additionally, nitrate, chloride, bicarbonate, and carbonate ions slightly impeded the removal of PCM in both processes. Furthermore, the TOC removal for UV/H₂O₂ and photo‐Fenton techniques was measured to be 65.3 and 83.5%, respectively, after 180 min. In addition, the total cost for the UV/H 2 O 2 process for one order removal (90% removal) of PCM was calculated to be 1.43 $ m −3 . Moreover, two degradation products (DPs) of PCM were identified using GC/MS analysis. The computational investigation was performed for toxicological measurements of identified DPs. The current work showed that PCM could be effectively degraded and mineralized using both UV/H 2 O 2 and photo‐Fenton techniques.
This study develops steady‐state and dynamic models of a CO 2 cryogenic separation process using Aspen HYSYS, focusing on control and operational robustness. The sensitive tray in the purification tower is identified using slope and sensitivity criteria, and PID controllers are applied with parameters tuned by empirical and relay autotuning. A representative steady‐state period shows that key variables, including flow rates, air release, liquefier cold load, reboiler heat load, subcooler cold load, CO 2 recovery, and outlet temperatures, remain constant for up to 5 h, confirming stable operation. Dynamic performance is analyzed under typical disturbances, including a 10% increase in feed flow rate, a 2% increase in feed CO 2 content, and a 10°C increase in feed temperature. Results indicate that increasing feed flow rate causes the strongest system‐wide transients and the largest impact on energy consumption. A 2% increase in CO 2 content has minimal effects, while feed temperature mainly affects condenser/reboiler thermal behavior. This work establishes an integrated framework for steady‐state validation, sensitive‐tray identification, disturbance‐response analysis, and energy sensitivity assessment, providing valuable guidance for CO 2 cryogenic separation units.
As fossil fuels are depleting rapidly, biodiesel has turned out to be a sustainable and prominent eco-friendly alternative for global energy demands across transportation, industrial, agricultural, and marine sectors. To contribute to this alternative, this study focused on producing biodiesel from mustard seeds, where the extracted oil from mustard seeds underwent transesterification, with an emphasis on optimizing process parameters. The effects of various reaction conditions, including methanol-to-oil ratio, catalyst amount, temperature, and reaction time on biodiesel yields, were investigated, and the optimal conditions for maximum yield were determined. The maximum biodiesel yield of 93% was achieved with a 6:1 methanol-to-oil molar ratio, 1.5 g KOH catalyst, 60°C reaction temperature, and 2-h reaction time. Also, several physicochemical properties such as viscosity, density, boiling point, calorific value, and cetane number were evaluated and compared with ASTM D6751 (biodiesel) and ASTM D975 (diesel) standards. The biodiesel exhibited a density ranging from 878 to 883 kg/m3, a viscosity of 5.4–6.5 mm2/s, a flash point between 142°C and 145°C, a boiling point from 232°C to 234°C, and a cetane number between 59 and 61. Even though the biodiesel’s calorific value (39–40 MJ/kg) was marginally lower than that of diesel (42–46 MJ/kg), the biodiesel met most ASTM D6751 specifications. These findings suggest that biodiesel produced from mustard oil represents a promising opportunity as an alternative fuel or blend for fossil fuels.
A study of the reaction kinetics was performed for the transesterification of linseed oil (LSO) using a clay-derived catalyst doped with barium chloride (CD-BaCl). Various analytical techniques, including XRD, SEM, BET, XRF, and FTIR, were employed to evaluate the catalyst's structural, surface, and chemical characteristics. The fatty acid methyl ester (FAME) profile of the resulting products was obtained via gas chromatography-mass spectrometry (GC-MS). Kinetic trials were conducted at three temperatures-40, 50, and 60 degrees C-under fixed optimal parameters: a methanol-to-oil ratio of 10:1, 4 degrees wt% catalyst, 300 rpm stirring speed, and a two-hour reaction period. Two mechanistic models-Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW)-were applied to interpret the kinetic data. The LHHW model provided the closest fit to the experimental results for the CD-BaCl catalyst, yielding an R2 value of 0.9428 and a residual variance of 6.32 & times; 10-12 at 60 degrees C. The rate-controlling step was determined to be the surface interaction between adsorbed triglyceride molecules and adsorbed methanol. Raising the reaction temperature accelerated the process, suggesting an endothermic nature. The activation energy and pre-exponential factor were calculated to be 9.07 kJ mol-1 and 3.36 h-1, respectively, both below the boiling point of methanol. Model validation showed excellent consistency between predicted and observed values, supporting the reliability of the proposed kinetic framework. The novelty of this work lies in the synthesis and kinetic evaluation of a BaCl2-impregnated clay catalyst for LSO transesterification, which exhibited effective performance under mild conditions and an unusually low activation energy, indicating a diminished energy barrier and improved surface reactivity. The kinetic analysis confirms that the reaction follows the LHHW pathway with surface reaction as the limiting step, providing fresh mechanistic understanding of acidic clay-based heterogeneous catalysts and demonstrating strong alignment between model predictions and experimental findings.
The growing demand for sustainable and eco-friendly alternatives to petroleum-based lubricants has prompted interest in plant-derived oils as a potential raw material for the synthesis of biolubricants. This study explores the utilization of microwave-assisted Soxhlet extraction (MASE) for the efficient recovery of oil from the three species of Brassica carinata seeds "Tesfa," "S-67," and "Holeta-1." Their physicochemical properties, fatty acid profiles, and functional groups were evaluated, alongside testing for stability and storage conditions for biolubricant application. MASE demonstrated efficient oil recovery, with yields varying between 33.4% and 44.5%, influenced by microwave power, extraction duration, and solvent-to-solid ratios. Among the varieties, Tesfa and S-67 exhibited marked sensitivity to these parameters, whereas Holeta-1 displayed consistent performance under varying conditions. Compositional analysis revealed high carbon content (75.50%-76.10%), minimal nitrogen, and notable unsaturation levels. Erucic acid (42.17%-44.17%) and oleic acid (13.33%-26.97%) dominated the fatty acid profiles, aligning with traits desirable for lubricant formulation. FTIR and GC-MS analysis confirmed the presence of ester groups and unsaturated hydrocarbons, emphasizing their suitability for biolubricant synthesis. Stability assessments highlighted Holeta-1's superior resistance to oxidative degradation, while Tesfa and S-67 required controlled storage conditions to mitigate temperature and light-induced breakdown. These findings highlight the potential of Brassica carinata seed oils as sustainable feedstocks for biolubricant production, with tailored processing strategies required to enhance their performance and stability for industrial applications.
Growing global energy demands and the urgent need to cut greenhouse gas emissions have amplified interest in biodiesel, yet its widespread adoption often conflicts with food resources. This study targets a more sustainable biodiesel production pathway by converting palm oil mill effluent (POME) oil-a prevalent industry by-product-using lipase Eversa Transform 2.0 immobilized onto octyl-functionalized silica via adsorption hydrophobic interaction. The immobilized enzyme demonstrated high catalytic activity (0.6 0.6 +/- 0.04 U & centerdot;mg-1) and achieved a notable fatty acid methyl ester (FAME) yield of 81% +/- 6% under optimized conditions (6%-wt catalyst, 1:7 oil-to-methanol molar ratio, 3-step methanol addition, 24 h at 40 degrees C). Stepwise methanol addition improved conversion by minimizing lipase inhibition. Biodiesel produced met key national fuel standards, including density, viscosity, and free glycerol content. These findings highlight the potential of hydrophobic octyl-functionalized silica support-immobilized lipase for efficient biodiesel synthesis from industrial waste oils. The system offers a promising approach for green fuel production, combining high performance with waste valorization in support of sustainable energy goals.
Concrete, as a building material, is strong and durable. However, under the influence of aggressive environmental factors, it can undergo corrosion and destruction. Water, in the form of precipitation and groundwater, is one such medium that can have a negative impact on concrete. Water is a weak solution of salts, acids, and bases, and it can lead to the deterioration of concrete structures. To prevent the negative effects of water on concrete, various additives are used. These additives help to increase the resistance of concrete to moisture. Among these additives, organosilicon-based compounds are particularly effective. They have unique physicochemical properties and are economical to produce. However, the exact mechanism of their action is not fully understood. The aim of this research is to investigate the effect of a specific type of hydrophobic additive on the physical and mechanical properties of concrete. This additive is based on polymethylethoxysiloxane-polyethylene glycol (PMEOS-PEG) and silica sol in ethyl cellulose (silicasol). The results of the study will help to better understand the role of these additives in improving the durability of concrete structures under water-related conditions. PMEOS-PEG has been shown to increase the mobility of the solvent mixture and also slightly increase the latency. Silicasol, on the other hand, does not affect mobility and has a significant retarding effect. The introduction of PMEOS-PEG hydrophobizer increases the strength of mixtures by 50%, when using Portland cement grade CEM II/A-S 42.5 N, and by 20% in mixtures with unmodified Portland cement CEM I 42.5 N. Silicasol's addition does not alter the strength characteristics of cement-sand mixtures. There is a slight tendency toward a decrease when using CEM I 42.5 N. The water impermeability of concrete samples using PMEOS-PEG and silicasol at a dosage of 0.7% increases from W6 (without additives) to W12 and W8, respectively.
This study investigates dimethyl carbonate (DMC) as a polar aprotic cosolvent in the direct ethanolysis of oil palm empty fruit bunches (OPEFB) to produce ethyl levulinate. Among several tested cosolvents, DMC significantly improved selectivity and suppressed humin formation, thereby increasing ethyl levulinate yield from 18.69% to 24.49% under relatively mild conditions (140 degrees C, 90 min). Product characterization by GC-MS and FTIR revealed the formation of furan-derived intermediates and humin-type polymers, supporting a reaction network involving hydroxymethylfurfural (HMF) and ethoxymethylfurfural (EMF) intermediates. The results suggest that DMC modifies the reaction microenvironment by regulating solvent polarity and water activity, thereby stabilizing reactive intermediates and redirecting carbon flow toward levulinate esters. This work provides useful insights into solvent-engineering strategies for the selective conversion of lignocellulosic biomass.
In petrochemical industries, hydrogen production as an energy carrier from fossil fuels is inevitable with the carbon footprint contribution. Catalytic conversion of methane into hydrocarbons comes with technological challenges and the sensitivity of the catalysts used. Therefore, this study investigated catalytic pyrolysis of methane with different metals (Fe, W, and Mo) supported on activated carbon (AC). The catalysts were obtained by the incipient wetness impregnation technique, characterized, and tested for methane pyrolysis in a custom-made stainless-steel fixed-bed reactor at a temperature of 750 degrees C and pressure of 1 atm for 4 h. The most effective catalyst tested was the 5.4 wt. % tri-metallic/support (Fe-W-Mo/AC) system with a high surface area of 1001.1 m2/g. Under the same operating conditions and 0.00767 moles of methane (CH4) fed, 8.6%CH4 conversion, C2 hydrocarbons (23.9%), hydrogen (36.4%), and coke (39.6%) was achieved. This suggests that producing hydrogen via methane pyrolysis presents a carbon-neutral economy that is a viable alternative to fossil fuels. Hence, exploring the potential of using Fe-W-Mo/AC tri-metallic catalysts for subsequent process optimization and technoeconomic analysis of methane pyrolysis into hydrogen and valuable product distribution is a viable option.
The power consumption of impellers is a fundamental parameter for the design, operation, and scale-up of stirred vessels. While numerous power correlations have been reported for various impellers in cylindrical tanks, no correlation has been established for crescent-shaped impellers commonly used in round-bottom flasks at the laboratory scale. In this study, a power correlation for crescent-shaped impellers installed in round-bottom flasks was developed, with particular attention to the effect of impeller mounting position. Power measurements were conducted using six crescent-shaped impellers of different geometries under various liquid heights without baffles. To examine the influence of impeller clearance from the vessel bottom, additional experiments were performed using paddle and Rushton turbine impellers installed at different vertical positions in a flat-bottom cylindrical vessel. The results revealed that, even under laminar flow conditions, the power number increased significantly when the impeller was installed near the vessel bottom. This increase was attributed to the interaction between the impeller and the laminar boundary layer formed on the vessel bottom. Based on these findings, the existing correlation proposed by Kamei et al. was modified. The turbulent term was adjusted, and the laminar power number was multiplied by a factor of 1.4 to account for bottom installation with minimal clearance. The modified correlation successfully correlated the experimental data for crescent-shaped impellers over the Reynolds number range of 1 < Re < 10,000, with an average error of 10%. This correlation enables power-based scale-up of laboratory-scale mixing operations using round-bottom flasks to industrial stirred vessels.
Additive consumption during NOx removal via NO2 absorption into aqueous solutions remains a critical challenge for sustainable flue gas cleaning and minimizing process waste. While sulfite additives are widely used to enhance NO2 absorption rates, their effectiveness is severely compromised under aerobic conditions due to rapid oxidation of sulfite to sulfate via a NO2-induced radical chain mechanism. This not only reduces the process efficiency but also leads to excessive additive consumption and waste formation. Thiosulfate, acting as a radical scavenger, offers strategies to mitigate these undesired side reactions by interrupting the radical chain mechanism. In the present study, sulfite and thiosulfate consumption were systematically investigated under aerobic and anaerobic conditions in a laboratory-scale NO2 scrubber for NO2 concentrations ranging from 50 to 200 ppm and additive concentrations between 0 and 10 mM sulfite and 0-3 mM thiosulfate. The novelty of this work lies in the development of a comprehensive kinetic model that predicts absorption efficiency as well as additive consumption across varying operating conditions. Unlike previous empirical approaches, this model provides mechanistic insights into the interplay between absorption reactions and side reactions, enabling good estimations of additive requirements and their effective contribution to the NO2 removal process. The strong agreement between modeled and experimental data highlights its robustness and applicability. This modeling framework represents a step toward optimizing additive usage in flue gas cleaning, reducing chemical waste, and improving the sustainability of industrial flue gas cleaning processes.
This study presents a leakage-aware machine learning framework for predicting minimum horizontal stress (sigma hmin) using structured geomechanical and fracture-related parameters. A dataset comprising 21,499 records from approximately 200 horizontal wells in the Marcellus Shale was preprocessed using a strictly leakage-controlled pipeline, including feature refinement, outlier capping, and training-fold-based transformations. Three ensemble models-random forest (RF), gradient boosting regressor (GBR), and extreme gradient boosting (XGBoost)-along with a stacking regressor and artificial neural network (ANN), were evaluated using root mean squared error (RMSE), mean absolute error (MAE), and coefficient of determination (R2). The RF model achieved the best baseline performance (RMSE = 6.5846, R2 = 0.9988), while gradient boosting showed improved performance after tuning (RMSE approximate to 6.59). The stacking model delivered competitive results (RMSE = 7.4963), whereas the ANN showed lower performance (RMSE = 55.5008), indicating limited suitability for structured tabular data. A scenario-based evaluation using Nigerian reservoir data demonstrated reasonable pr3332edictive consistency but was not treated as external validation due to data limitations. The results confirm that leakage-aware ensemble learning provides a robust and physically consistent approach for predicting minimum horizontal stress, with potential application in reservoir characterization and hydraulic fracturing design.
Hydrogen production through anaerobic fermentation has gained prominence among researchers as a promising ecological route, capable of combining the treatment of highly polluting waste with the generation of a clean fuel. Hydrogen is considered a strategic energy carrier for the transition and restructuring of the global energy matrix, as it is a renewable source free of carbon emissions. The present study aimed to conduct a critical and systematic review to analyze the main advances related to the use of anaerobic fermentation for hydrogen production and the importance of integration between biochemical pathways, addressing the parameters that influence its efficiency, the types of substrates and inoculum used, pretreatment conditions, the influence of optimized microbial strains on hydrogen production, types of reactors employed, and the technical, economic, environmental challenges associated with this biotechnological route, and main perspectives for future studies. Although still at an early stage, the feasibility of this technology has been demonstrated through various studies. It is observed that maximizing production is strongly linked to the precise control of operational variables, such as pH, temperature, hydraulic retention time, and the appropriate proportion of essential nutrients, especially carbon and nitrogen, which are fundamental for microbial growth and development in the system. Furthermore, the choice of substrates rich in organic matter with high carbohydrate content and the appropriate selection of inoculum, whether natural cultures or modified strains, aligned with the conditions of the fermentation process, are of great importance. The use of pretreatments also proves essential for the elimination of undesirable microorganisms, contributing to increased process efficiency. Thus, it is concluded that, despite its potential, anaerobic fermentation for hydrogen production still requires significant advances in research and large-scale system development. With the improvement of the techniques involved, optimization of genetically modified strains, and integration of production processes, this approach can establish itself as a sustainable alternative for energy recovery from waste, contributing significantly to sustainable development through the transition to a cleaner and more resilient global energy matrix.
In stirred tank reactors, vortices are currently predicted using an outdated dimensionless baffle index that does not correspond to state of the art in science and technology. However, it is extremely important to know when a vortex occurs because they have various advantages and disadvantages. For this reason, knowledge about vortices, especially in reactor systems with baffles, is of great importance to the production and process industry. In order to close this significant knowledge gap, this study presents comprehensive and detailed results from experiments conducted on a laboratory scale of 110 mm for the evaluation, prediction, or prevention of vortices in a Reynolds number ranging from 1,000 to 45,000, as well as providing a definition of vortices for the first time. For the investigations, two single-stage radial stirrers, the Rushton turbine and the curved-blade impeller, with varying numbers of baffles between zero and six, and different baffle geometries (rectangular, cylindrical, and triangular) are analyzed in water. The power consumption, vortex characteristics, and influence of the baffled state are examined. The vortices present are detected using MATLAB macros and described mathematically with a fourth-degree polynomial function. The obtained vortex shape (depth, width, and volume) is presented as a mathematical relationship. Furthermore, this study provides, for the first time, dimensionless values for vortex depth, width, and volume. These dimensionless values can be used as design rules, assistance, or recommendation. This allows more accurate predictions about vortices in large reactors in order to simplify the design and better positioning of internal installations to make stirred tank reactors more economical and sustainable in the future.
This study develops steady-state and dynamic models of a CO2 cryogenic separation process using Aspen HYSYS, focusing on control and operational robustness. The sensitive tray in the purification tower is identified using slope and sensitivity criteria, and PID controllers are applied with parameters tuned by empirical and relay autotuning. A representative steady-state period shows that key variables, including flow rates, air release, liquefier cold load, reboiler heat load, subcooler cold load, CO2 recovery, and outlet temperatures, remain constant for up to 5 h, confirming stable operation. Dynamic performance is analyzed under typical disturbances, including a 10% increase in feed flow rate, a 2% increase in feed CO2 content, and a 10 degrees C increase in feed temperature. Results indicate that increasing feed flow rate causes the strongest system-wide transients and the largest impact on energy consumption. A 2% increase in CO2 content has minimal effects, while feed temperature mainly affects condenser/reboiler thermal behavior. This work establishes an integrated framework for steady-state validation, sensitive-tray identification, disturbance-response analysis, and energy sensitivity assessment, providing valuable guidance for CO2 cryogenic separation units.
