Canadian Journal of Chemical Engineering最新文献

In the realm of chemical processing, particularly at the industrial scale, safety is of utmost importance. A predominant factor causing accidents within the chemical industry is runaway phenomena, primarily initiated by uncontrolled exothermic reactions. This review critically examines the often-overlooked decomposition mechanisms as a significant contributor to thermal energy release, necessitating a comprehensive revision and understanding of both experimental and theoretical strategies for assessing thermal degradation. Key to this discourse is the explication of calorimetry as the principal experimental technique, alongside ab initio quantum chemistry simulations as a robust theoretical framework for quantifying the most relevant properties. However, more than mere cognisance of these methodologies is required for a meticulous thermal stability assessment. The review emphasizes identifying and quantifying fundamental parameters through experimental and theoretical investigations. Only upon acquiring these parameters, including kinetic, thermodynamic, onset, and peak characteristics of the exothermic decomposition reactions, can one effectively mitigate risks and hazards in designing and optimizing chemical processes and apparatus. Furthermore, this review delineates qualitative and quantitative methodologies for hazard assessment, proffering strategies for estimating safe operational conditions and sizing relief devices. The paper culminates in exploring future trajectories in thermal stability assessments, focusing on emerging applications in lithium-ion batteries, electrolyzers, electrified reactors, ionic liquids, artificial intelligence and machine learning approaches. Thus, the paper underlines the evolving landscape of thermal risk management in contemporary and future chemical industries.

The optimization of operating parameters for the simulated moving bed (SMB) is complex. A parameter optimization method for the SMB system was proposed based on the improved multi-objective sand cat swarm optimization (IMOSCSO) algorithm. The multi-objective sand cat swarm optimization (MOSCSO) algorithm integrated the update and selection mechanism of the repository in the multi-objective algorithm. Three strategies were proposed to improve the traditional MOSCSO algorithm for increased population diversity, global search capability, and convergence speed. First, the cubic chaotic map was used to initialize the population, which improved the uniformity of the population distribution. Second, including a variable spiral search strategy in the prey search phase enabled the sand cat swarm to explore more search paths to adjust its position. Third, the convergence speed was enhanced by incorporating the alert mechanism of the sparrow search algorithm. The improved algorithm was tested with standard test functions. The IMOSCSO algorithm outperformed other algorithms in terms of convergence and accuracy. Finally, the IMOSCSO algorithm optimized the system parameters of the SMB, demonstrating its practical applications.

In this work, the performances of a nonlinear dynamic industrial process are examined using grey-box (GB) models. To understand the dynamics of the system, the transient state is targeted. A white-box (WB) model holds the prevailing knowledge using some assumptions. The performance of this model is limited. Artificial neural network (ANN) and support vector regression (SVR), which are techniques employed in numerous chemical engineering applications, are employed to construct the associated black-box (BB) models. GA is used to optimize the SVR parameters. Dimensional and range extrapolations of different manipulated inputs, feed concentrations, feed temperatures, and cooling temperatures of the GB model and BB model are discussed. The different inputs extrapolation has different results because each input's effectiveness in the system is different. The results are compared, and the best model is suggested among the models, ANN, SVR, first principle (FP)-ANN serial structure, FP-ANN parallel structure, FP-SVR serial structure, and FP-SVR parallel structure.

The effect of organic and inorganic compounds, commonly present in the mineralogy of crude oil and/or added in the washing processes of extracted crude, on the removal efficiency of emulsified oils present in waste washing waters was investigated by means of flocculation. Approximately 90% of the emulsified oil could be removed using an anionic flocculant, providing a residual turbidity below 100 NTU. The yield depended on the nature of the organic and inorganic components present. The higher the chain length of the main organic component, the greater the flocculant concentration required to remove the oil. Several components had an effect of emulsification (e.g., octane, decane), some of which rendered de-oiling process completely ineffective (e.g., naphthenic acids). Aliphatics were the most difficult to eliminate, requiring flocculant levels in the 200–300 ppm range. This is in contrast to 75–100 ppm levels which were required to remove bi- and poly-cyclic aromatics. Heavy oils were more difficult to remove than light oils. There was a strong effect of the pH of the aqueous phase. The optimum was pH = 2.0. Virtually all inorganic compounds reduced the efficiency of removing oil from water when spiked at 1%. The only exception was sodium carbonate which acted as a de-emulsifier. Monovalent salts have a minor effect on de-oiling, with efficiencies remaining at 80%. Divalent chlorides reduced the de-oiling efficiency to 70% while sulphates had a more severe influence. The de-oiling efficiency was lowered substantially with the addition of clays, zinc, cadmium, ferric oxide, calcium carbonate, and dibenyhlthiophene.

Superimposition of oscillatory flow over the axial flow is expected to further enhance the mixing phenomenon based on the limited reported literature. A detailed study on the physics of such superimposed flows will be useful to widen the scope of application of static mixers with superimposed oscillatory flow in continuous modes of operation for several purposes. The flow behaviour of a water–vinyl acetate system in a milli-channel with static internals is studied under the laminar flow regime using computational fluid dynamics (CFD) as a tool. A CFD model is developed and validated with reported literature on a Kenics static mixer. The effect of oscillatory flow superimposed over the axial flow in a milli-channel is studied for Re_n = 5 and Re_o = 20–65. Residence time distribution (RTD) studies have been carried out and compared numerically for two different geometries, (1) tube without an internal and (2) tube with internals, for two different velocities, (1) net axial velocity and (2) superimposed oscillatory velocity. Results of these RTD studies indicate a sharp distribution in the channel with static internals having superimposed oscillatory flow followed by the channel with static internals with net axial velocity and then a tube without an internal. It is also found that Péclet number (Pe) for static internals with oscillatory flow > net axial flow > tube without an internal (736 > 641 > 315). Further, velocity magnitude, pressure, and Q-criterion are discussed in detail to understand fluid flow behaviour in the milli-channel. From this research, it is understood that superimposing oscillatory flow along with static internals resulted in enhanced mixing when compared with a tube with no internal.

This study investigated biosurfactant production by the bacterial strain of P. aeruginosa gi |KP 163922| for a free and immobilized cells system using waste engine oil (WEO) as a substrate. The polyurethane foam (PUF) cubes (1 cm × 1 cm × 1 cm) were used as carriers for the immobilization. The batch experiments were performed in Erlenmeyer flasks and monitored at every 24-h interval for both cell systems. The microbial population was counted using the plate count method, and the hydrocarbon degradation percentage was calculated to evaluate the bacterial activity. Surface tension was measured at regular intervals to ensure the presence of biosurfactants. The maximum reduction was 37 and 35 mN/m in a free and immobilized cells system. Immobilization of cells using PUF was found to be efficient in supporting bacterial growth, and after 48 h of incubation, the growth was 2.5 (±0.58) × 10¹¹ CFU/mL. The chemical characterization using Fourier transform infrared (FTIR) spectroscopy confirmed the obtained product as rhamnolipid. Crude biosurfactant yield was found to be maximum in the case of the immobilized system, which was approximately 18 g/L. Scanning electron micrographs (SEM) of the used PUF cubes showed the strong adherence of biofilm to the cube surface and the potential of its reuse in multiple cycles. Gas chromatography–mass spectrometry (GC–MS) analysis confirms that the immobilized strain of P. aeruginosa exhibited superior biodegradation capabilities compared to free cells. Specifically, it was capable of reducing the concentration of polyaromatic hydrocarbons and converting more significant aliphatic compounds into metabolic byproducts such as alkanes, alkenes, cycloalkanes, and carbonyl groups.

CO₂, a predominant anthropogenic greenhouse gas, emerges as a primary factor in climate change due to the increasing utilization of fossil fuels, necessitating immediate efforts for the development and implementation of strategies like carbon capture and storage (CCS) to mitigate emissions, considering the ongoing dependence on unsustainable energy and transportation resources. The research endeavours to meet the critical requirement for effective CO₂ capture through the exploration of novel sorbent materials, with a specific focus on molecularly precise nanoclusters (NCs), aiming to enhance understanding of the catalytic mechanisms in CO₂ reduction and design stable, high-performance sorbents with controllable properties. Advancing the field, the study delves into the synthesis and examination of molecularly precise nanoclusters (NCs), an emerging domain in nanoscience, with a particular emphasis on well-defined nanoclusters like thiolate-protected Au, Ag, and Cu NCs. This strategy provides a distinctive foundation for attaining atomic-level understanding of electrocatalytic CO₂ reduction mechanisms, offering a more precise and customized synthesis to overcome challenges associated with polydispersity in conventional nanoparticles. The study highlights the exceptional catalytic activity of specific Au NCs like Au₂₅ in converting CO₂ to CO. It surpasses thermodynamic limits. The study also investigates the influence of surface properties, electrostatic, and steric stability on preventing nanocluster aggregation. It emphasizes the potential of molecularly precise nanoclusters as catalysts for CO₂ reduction. Additionally, it suggests avenues for advanced sorbent development with improved performance and stability.

In this study, the simplified version of statistical associating fluid theory (SAFT) equation of state (EOS) developed by Fu and Sandler is modified by replacing the dispersion term of this EOS with the Haghtalab–Mazloumi equation. This new SAFT-based EOS has three adjustable parameters for non-associating compounds and five adjustable parameters for associating compounds. The adjustable parameters of the new EOS are obtained by simultaneously fitting vapour pressures and liquid densities of pure substances. The new EOS shows better results in correlating vapour pressure and saturated liquid densities than SSAFT EOS for a selection of non-associating and associating substances. Then, by using proper mixing rules, the new EOS is extended for mixtures. Both self-associating and cross associating binary mixtures are used to test the capability of the new EOS in vapour–liquid equilibrium (VLE) calculations, and the results demonstrate good accuracy of the new EOS.

The main goal of this proposal is to present a class of nonlinear controllers for regulation and set point changes in continuous chemical reactors. The proposed control law has in its mathematical structure a proportional term of the regulation error to provide closed-loop stability and a sinusoidal term, which can compensate for the nonlinearities of the plant. The closed-loop stability of the plant is demonstrated via Lyapunov analysis, which reveals an asymptotic convergence of the control output to the required set points. Furthermore, the analysis of the regulation error's dynamic under the considered assumptions leads us to conclude that exponential stability is also reached. The controller is implemented via numerical experiments in two examples to generalize the applicability of the proposed approach by considering continuous stirred-tank reactors models. The first case considers autocatalytic chemical oscillatory reactions that induce chaotic behaviour. For the second case, a process of acetone, butanol, and ethanol (ABE) fermentation through Clostridium acetobutylicum is considered. The proposed strategy shows an adequate performance because it can reach the required set point without long time settings and overshoot. A comparison with a smooth sliding-mode and a standard proportional-integral (PI) controller indicates the advantages of the proposed control approach.

Sodium polyacrylate (PAAS), a macromolecule surfactant, was employed in the synthesis of polyvinyl butyral (PVB) using a deep eutectic solvent (DES) as the catalyst. Contrasting with traditional low molecular weight surfactants, scanning electron microscopy (SEM) analysis has confirmed that PAAS enhanced the uniformity of PVB granules while minimizing PAAS residuals, facilitating the production of films with superior transparency and resistance to yellowing. Investigations into the effects of varying molecular weights, dosages of PAAS, and aging times on the properties of PVB revealed that an increase in PAAS molecular weight correspondingly raised the acetal degree (AD) of PVB without affecting the molecular weight of PVB itself. Furthermore, yhe dosage of PAAS significantly impacted the properties of PVB, whereas aging time exhibits minimal influence on the AD of PVB. ¹H-NMR analysis indicated that the structural stability of PVB is due to the dominance of meso acetal isomers, which improved its mechanical properties when synthesized with PAAS3 (molecular weight 60,000 g/mol), containing 91.5% hexamethylene cycloacetal. Notably, compared to PVB synthesized using sodium dodecyl sulphate (SDS), PVB synthesized with PAAS3 exhibits superior mechanical properties, with significantly improved tensile strength and elongation. This phenomenon is further elucidated by SEM images. A comparison between the optimized self-made PVB and commercial PVB shows that the self-made PVB performs better, highlighting the critical role of macromolecular PAAS in enhancing the structure and mechanical properties of PVB.