Chemical Engineering & Technology最新文献

Ellipticity has a significant impact on the flow and heat transfer performance of microchannel heat exchangers (MHEs) with elliptical concave cavities. In this study, five types of MHEs with different elliptical concave cavities (ellipticities of 0.4, 0.6, 0.8, 1.0, and 1.2) were designed. The influence of ellipticity on the flow and heat transfer performance of MHEs was numerically investigated using ANSYS Fluent 21.0 R1. Moreover, MHEs with corresponding elliptical concave cavities structures were processed and manufactured, and then an experimental platform was designed and built for experimental verification. The results showed that the fluid velocity distribution in MHEs with elliptical concave cavities was symmetrical, and the formation of secondary flow in the elliptical concave cavities led to the continuous destruction and reconstruction of the flow and thermal boundary layer in the microchannel, which is conducive to mass and heat transfer in the MHEs with elliptical concave cavities. The inlet and outlet pressure drop of MHEs with elliptical concave cavities increased as the inlet flow rate increased. At the same inlet flow rate, the inlet and outlet pressure drop of the MHE with elliptical concave cavities first increased and then decreased with increasing ellipticity. At an ellipticity of 1.0, the inlet and outlet of MHE exhibited the lowest pressure drop indicating that the MHE with an ellipticity of 1.0 featured the highest pressure drop performance. The cold-water outlet temperature of the MHEs with elliptical concave cavities first decreased and then increased as the inlet flow rate increased. At the same inlet flow rate, the cold-water outlet temperature of the MHEs with elliptical concave cavities first increased and then decreased with increasing ellipticity, while the hot-water outlet temperature of the MHEs first decreased and then increased with increasing flow rate. This indicated that the MHE with an ellipticity of 1.0 exhibited excellent heat transfer performance.

Water coloring has the properties of resistance to mutagenic, toxic, aggressive, carcinogenic, destructive, strong light and unstable oxidation and air pollution and has serious effects on environmental systems and human health. Because of its severe toxicity, methylene blue (MB) can cause cancer, mutagenesis, and teratogenic consequences in people as well as enter the food chain. The main objective of this investigation is to study the modeling and the optimization parameters of MB adsorption using a low-cost adsorbent Fe₃O₄. The parameters evaluated for adsorption are the adsorbent dosage, pH, contact time, and temperature using the response surface methodology. The principal variables affecting MB removal were pH (3–11), catalyst dosage (0.01–0.3 g), contact duration (10–180 min), and temperature (25–55 °C). To select an experimental domain, a preliminary study was performed first. The results showed that at pH 10, 1.4 g L⁻¹ Fe₃O₄-nanoparticles (NPs) had the highest removal efficiency of cationic dye MB (20 ppm) from aqueous solutions by batch adsorption technique. The pseudo-second-order (PSO) kinetic models and the Langmuir isotherm provided the best fit for the adoption of MB. The adsorption process was exothermic and spontaneous, according to thermodynamics studies. To determine the effect of the investigated variables and their interaction on the adsorption process, a Box–Behnken design was used. A second-order polynomial equation was used to model the experimental results. The experimental findings were consistent with the suggested model as demonstrated by the high value of the determination coefficient. The performance of the model equation verified the experimental observation with just a slight divergence, and the values acquired from the experiment and model predictions were found to be in suitable agreement. According to the numerical optimization, 98.61 % is the optimal elimination efficiency for MB adsorption. These results suggest that an adsorption process utilizing Fe₃O₄ NPs is efficient in environmental remediation.

The curcumin-malic acid-aspartic acid polymer (PCMA) as a new water treatment agent was prepared by solid phase synthesis of curcumin, malic acid and aspartic acid. The static scale inhibition experiments showed that PCMA can inhibit CaCO₃ and CaSO₄ scale formation by 100.0 % and had excellent scale inhibition effect under various experimental conditions. The mechanism of action of PCMA was obtained by X-ray diffraction, scanning electron microscope and molecular dynamics simulation. Electrochemical test showed that PCMA is an anodic corrosion inhibitor that achieves 93.1 % corrosion inhibition by forming a protective film on the surface of Q235 carbon steel. Besides, fluorescence spectra proved that PCMA has stable fluorescence intensity.

Effects of nanoparticle and steam injection on the extraction of Iranian American Petroleum Institute (API) 14 heavy oil from a model porous medium at temperatures of 110, 150, and 200 °C were investigated. Nanoparticle content was 1 %, 3 %, and 5 %, and injection flow rates were 0.018, 0.036 and 0.072 mL h⁻¹. In short-term injection, increasing the injection temperature to 200 °C and the flow rate to 0.072 mL h⁻¹ resulted in the highest recovery. In the mid-term injection, the highest recovery factor was at a temperature of 150 °C and flow rate of 0.036 mL h⁻¹, while the results of the long-term injection predicted a non-monotonic effect of flow rate. The effect of alumina content on the recovery factor is less than that of temperature and flow rate. Interestingly, alumina content also has non-monotonic effects on the recovery factor.

Calcium oxalate (CaOx) crystallization is a common phenomenon that contributes to various kidney disorders and stone formation, as well as the formation of scale in industrial processes. The inhibition of CaOx is an area of intense scientific interest in the field of materials science due to its relevance to biomineralization. The present study investigated the effects of pectin (PE) and sodium alginate (SA), two natural polymers, on the growth of CaOx crystals using a batch crystallization method in aqueous solutions at 37 °C with different concentrations (0.5, 1, 5, and 10 ppm). The results of the study showed that both PE and SA were effective inhibitors of CaOx crystal growth, with the highest inhibition observed at a concentration of 10 ppm, reaching 80 %. PE did not significantly affect the size of the crystals, while SA reduced their size as the concentration increased. These findings contribute to our understanding of the potential of natural polymers as non-toxic inhibitors of CaOx crystal growth.

A highly stable and electrochemically active porous molybdenum carbide (PMC) has been synthesized from agricultural waste by carburization of bagasse under inert conditions. The surface area and porous structure of the resulting PMCs can be tuned by varying the synthesis conditions. The PMCs obtained have been characterized via XRD, XPS, SEM, and gas physisorption techniques. The final PMC materials are highly crystalline with nanoscale porosity and with an active surface area of up to 717 m².g⁻¹. This work unlocks a promising avenue for developing highly active electrochemical nanomaterials using green synthesis, potentially eliminating the need for noble metals. The results demonstrate a six-fold increase in the electrochemical signal.

The selection of adsorbents is critical for developing an adsorption unit. In this study, a activated carbon fibers (ACF) and a granular-activated carbon (GAC) were evaluated in dynamic toluene adsorption to determine their benefits and limitations. A variety of physicochemical approaches were used to characterize the samples. Adsorption under varied circumstances demonstrated that ACF has a larger adsorption capacity and a longer saturation time than GAC. The Langmuir isotherm suited equilibrium data well. Thermodynamic characteristics showed that adsorption was spontaneous and exothermic. The adsorption kinetics were found to be dominated by the pseudo-first-order model, with GAC having a greater sorption rate. Thermal regeneration appeared to be more favorable for ACF.

Converting the abundant biomass resources in nature into fine chemicals can not only reduce carbon emissions but also effectively deal with the depletion of fossil energy, which is of strategic significance for sustainable development. In this paper, by optimizing the content of bimetallic components, highly active co-doped Co₁Cu₃ bimetallic silicate was designed and synthesized. After reduction, a highly dispersed and stable Co₁Cu₃/SiO₂ catalyst was obtained, which was used to catalyze the aqueous phase hydrogenation of furfural (FFR) to cyclopentanone (CPO). Compared with the traditional supported catalyst, the Co₁Cu₃/SiO₂-ammonia evaporation (AE)-300 catalyst prepared by AE has the best performance. Under the optimal reaction conditions, the conversion of FFR was as high as 95.1 % and the selectivity of CPO was 88.6 %. This high activity can be attributed to the formation of highly dispersed and uniform metal active sites with low content of Co. At the same time, the formation of flocculent silicate enhances the synergism between CoCu and SiO₂ support and increases the specific surface area of the catalyst. In addition, the experimental results show that the reaction carbon balance will be destroyed with the high concentration of FFR solution.

Nowadays, due to the lack of drinking water and the increase in global demand, desalination by reverse osmosis (RO) has been developed. In this regard, activities have been carried out to increase water flux and salt removal, which are important indicators in this process, including membrane modification by loading nanoparticles (NPs). Process simulation plays an important role in reducing laboratory costs, improving efficiency, and investigating operational parameters in more detail. This is an important factor that leads us to process simulation. The simulation of the RO process by thin-film composite membranes modified with nanoporous titanate (mNTs) NPs has been conducted using COMSOL software. The performance of this process was checked by loading different amounts of mNTs with the desired membrane. The results revealed that by adding 0.01 w % of mNTs to the membrane composition, the performance of the process was improved in that the initial water flux through the membrane increased by about 95.4 %, while the salt rejection remained nearby 98 % and did not decrease much. Finally, to validate and expand the simulation results, the model outcomes were compared with experimental data, and the mean relative error for water flux and salt removal percentage was 1.15 % and 0.83 %, respectively.

The impact of radial dispersion of both heat and mass on the behavior of cooled fixed-bed reactors was explored using a two-dimensional reactor model. This study accounted for dispersion through an effective radial thermal conductivity (λ_rad) and a radial dispersion coefficient of mass (D_rad), with Fischer–Tropsch synthesis serving as an illustrative process example. Under moderate reaction conditions and hence still rather gentle radial temperature profiles, the effect of mass dispersion on reactor performance was found to be minimal, even if disregarded (D_rad = 0), whereas dispersion of heat (λ_rad) always significantly impacts reactor behavior. Nevertheless, for precise thermal runaway predictions by a reactor model, incorporating mass dispersion by a realistic D_rad value is essential.