Band 22, Heft 5

The rigid-flexible impeller (RF impeller) was used in the mixing process of viscoplastic fluid, and the mixing performance of RF impeller was explored by using numerical simulation and experimental analysis. Results indicated that RF impeller could reduce the power consumption ( P ) and demonstrate the advantage of energy-saving compared with Rushton turbine (RT). RF impeller demonstrated a more pronounced force coupling effect between the impeller and surrounding fluid, and exhibited superior adaptability in the flow field compared with RT. Meanwhile, the utilization of RF impeller can effectively enhance the expansion of high velocity region, expand the cavern zone, and decrease the mixing efficiency number while maintaining constant P compared with RT, and the size of high velocity region and cavern zone could be increased with an increase in impeller speed. Moreover, the cavern structure was obtained through the visualization experiment, and the results were similar to that in the simulation. The findings suggested that incorporating rigid-flexible combination structure design of impeller blades could effectively expand the cavern zone, reduce the stagnant zone, and enhance the mixing efficiency in the viscoplastic fluid mixing process.

In this study, the emission and performance characteristics of single-cylinder diesel engines were tested using various biodiesel blends prepared by mixing diesel with mango seed oil biodiesel (MSOB). Furthermore, the effect of n -amyl and n -hexanol alcohol additions on the performance and emission results of manufactured biodiesel blends is investigated and compared with diesel fuel. On the other hand, a hybrid deep neural network (DNN) based on the manta ray foraging optimization (MRFO) method is developed to forecast ideal biodiesel blends in order to reduce emissions from diesel engines while improving performance. The optimal brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) for this study were 32.3916 % for 75 % diesel + 20 % MSOB + 5 % n -hexanol fuel and 0.0453 kg/kWh for 75 % diesel + 20 % MSOB + 5 % n -amyl fuel, respectively. The optimal emissions from the test engine were 0.1034 % CO from 60 % diesel + 20 % MSOB + 20 % n -hexanol and 28.886 ppm HC from 75 % diesel + 20 % MSOB + 5 % n -hexanol fuel. The optimal smoke and NO x levels are achieved with a blend of 60 % diesel, 20 % MSOB, 5 % n-amyl, and 5 % n -hexane. Moreover, the developed DNN-MRFO achieved 0.9979, 0.9992 and 0.9975 overall regression coefficients during training, validation and testing. The root mean square error (RMSE) of DNN-MRFO also ranges from 0.019 to 0.032.

Chlorophyll from peppermint ( mentha spicata ) was evaluated as a natural dye sensitizer in TiO 2 solar cells. The final photoconversion efficiency depended on the solvent used as chlorophyll dispersant and the technique used to sensitize the mesoporous TiO 2 film. Evaluated sensitization techniques included pipetting, immersion, and electrophoresis. Best solar cell performance was obtained using methanol as solvent simultaneously with electrophoresis. A short circuit current density ( J sc ) of 0.174 mA/cm 2 and an open circuit voltage ( V oc ) of 0.508 V were obtained. The photoconversion efficiency reached 0.39 %. However, sensitizing by the pipetting technique allowed a photoconversion efficiency of 0.35 % with better reproducibility.

Ni-incorporated Mg–Al type hydrotalcite-like catalytic materials were synthesized following impregnation and co-precipitation routes, and their catalytic performances were compared in the dry-reforming reaction of methane. The effects of Ru impregnation on the catalytic performance of Ni-incorporated Mg–Al were also investigated. Results showed that the catalytic performance of the Ni-incorporated Mg–Al type catalyst (NiMgAlO), which was prepared by the co-precipitation route, was highly stable during dry-reforming reaction tests performed at 600 °C, extending up to 24 h. The fractional conversion of CO 2 (0.42) was higher than the fractional conversion of CH 4 (0.29) due to the contribution of the reverse water gas shift reaction. However, the contribution of the reverse water gas shift reaction to the product distribution was much less with the catalyst prepared following the impregnation route (Ni@MgAlO). This difference was shown to be mainly due to the state of the nickel in the catalyst structures. Ni-impregnated Ca–Al type hydrotalcite-like catalyst (Ni@CaAlO) was also synthesized and tested in dry reforming of methane. Results obtained with the Ni-impregnated Ca–Al type catalyst showed some changes in its structure and the formation of some CaCO 3 during the dry reforming reaction. The comparison of the performances of Ni-impregnated Mg–Al and Ca–Al type catalysts showed a higher amount of coke on the surface of Ni@CaAlO than Ni@MgAlO. It was also concluded that significant coke minimization and highly stable catalytic performance could be achieved by the impregnation of 1 % Ru to the NiMgAlO catalyst. The amount of coke deposited on the catalyst decreased from about 30 % to less than 5 %, by Ru impregnation. The decrease of the surface area of the Ru-impregnated catalyst was also only about 3 % after 240 min of reaction time.

Chemical looping hydrogen generation represents a viable technology for high-purity hydrogen production and CO 2 capture. Moving bed reactors are considered effective for this process, but the high cost of experiments and the complexity of the biomass gas reaction have hindered the development of hydrogen generation from biomass gas.This investigation employs Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) to simulate gas-solid phase distribution and reactions within a moving bed fuel reactor, aiming to amplify biomass gas and oxygen carrier conversion rates. Findings indicate that enhancing particle flux rate and reaction temperature substantially increases the conversion efficiency of both biomass gas and oxygen carrier. Notably, achieving complete CH 4 conversion presents significant challenges in biomass gasification, with CH 4 conversion dictating the requisite bed height for total biomass gas conversion. Furthermore, the gas-phase equilibrium conversion rate of Fe 3 O 4 to FeO delineates the operational limit within the moving bed. Under full reaction conditions of biomass gas, the oxygen carrier’s maximum achievable conversion ranges between 29.2  and 31.6 % at 850 °C. These insights substantially advance the application of biomass gas in the chemical looping domain and inform future design and operational strategies for reactors.

This paper introduces a novel process for decomposing N 2 O through interstage cooling utilizing a heat pipe heat exchanger. The reactor design involves segmenting the fixed bed reactor into multiple layers and integrating heat pipe heat exchangers between these layers to efficiently dissipate the high heat generated by the upper fixed bed reactor. This innovative approach facilitates the direct decomposition of N 2 O feedgas with high concentrations, obviating the need for gas dilution. The study conducted in this paper employed Fluent and ASPEN PLUS to investigate N 2 O decomposition with interstage cooling using heat pipe heat exchangers, as well as decomposition after dilution. A comparison between the two methods was made based on catalyst dosage, temperature uniformity, and reactor energy consumption. The results demonstrate that the proposed method for N 2 O decomposition via interstage cooling with a heat pipe heat exchanger is a viable option, offering the desired temperature control and enhanced efficiency. Furthermore, this reactor design effectively reduces both catalyst usage and energy consumption, providing substantial advantages over traditional approaches.

The hydrodynamics of a conical spouted bed was simulated utilizing the Eulerian–Eulerian Two-Fluid Model (TFM) incorporating a kinetic theory of granular flows. The simulations were confirmed with experimental data. To accurately examine the pyrolysis process, the hydrodynamics of the solid bed as well as the heat transfer inside it were analysed separately by considering a precise synthetic model. The effects of gas velocity, particle size, bed length, and temperature were thoroughly investigated. The results indicated that the amount of relative standard deviation increases with an increase in the inlet velocity into the bed. This amount of deviation at the inlet velocity (0.6 m/s for tar and gas flow to its maximum value of 9.1 and 9.4) is not desirable in product production and should be modified so that the amount of gas flow increases and the tar produced reaches the minimum possible amount. Also, the graphs of the relative standard deviation in terms of temperature indicate that the increase in temperature from 730 to 950 K is associated with a relatively smaller fluctuation of the relative standard deviation so that at the temperature of 730 K, it is 7.2 % for tar and 6.4 % for gas flow, while at temperature of 950 K, it is 6.5 % for wire and 6.8 % for gas flow. Finally, the results determined that small-diameter particles have a more significant fountain height and also higher velocity in the spout section.

When the airlift bioreactor is applied to the field of industrial fermentation, there is a common problem of low mixing and flow efficiency due to its simple structure. In order to expand the application of airlift bioreactor in the field of industrial fermentation, a new type of airlift bioreactor with three-dimensional bumps in the draft tube has been designed to enhance the mixing and flow of gas-liquid two-phase in the reactor. In order to determine the specific influence of the three-dimensional bumps on the internal flow field of the reactor, and to provide technical reference for the improvement of the structure of the airlift bioreactor, in this paper, the CFD simulation of this type of bioreactor is carried out. Based on the Euler multiphase flow, the Realizable k-ε model was used to analyze the flow field of the reactor with average gas-liquid flow linear velocity and temperature as parameters. The results show that under certain conditions, the three-dimensional bumps inside the draft tube can effectively accelerate the gas-liquid two-phase flow and better promotes the mixing of pig manure fermentation broth and air.

In response to the observed phenomenon of poor fluid mixing within the reactor, this study proposes a novel mixing method to enhance fluid mixing efficiency. In this study, numerical simulation and purification tests were carried out for the purification of zinc sulfate solution. Numerical simulations were conducted to compare the effects of variable-speed stirring and uniform-speed stirring on mixing efficiency, considering both momentum transfer process and mass transfer process. The purification test further demonstrated a significant improvement in the reaction rate under variable-speed stirring, as evidenced by the analysis of purification efficiency and microscopic morphology. It was elaborated that the enhancement mechanism of variable-speed stirring involved disrupting the periodic order structure in the tank, leading to the generation of a multi-scale vortex that increased stirring kinetic energy to form a shear force. This force contributed to reducing the velocity slip between the impurity ions and zinc particles, consequently decreasing reaction time and enhancing purification rate. The results indicated that sinusoidal stirring yielded the most effective mixing. When implemented in practical production settings, it enhanced dimensionless mixing efficiency by 24.83 % compared to the homogeneous stirring system. Additionally, it reduced reaction time by 15.47 % and decreased mixing energy per unit volume by 32.38 %, while simultaneously lowering energy consumption by 24.77 %.

This study is focused on elucidating the potential effectiveness of degradation as a method to eliminate dyes from aqueous systems. Specifically, it delves into the influence of ultrasound energy on the degradation kinetics of a dye. The research findings underscore the notable impact of ultrasound energy in accelerating the reaction rate constant ( k p ), with the degradation kinetics exhibiting a conformity to first-order kinetics. An integral aspect of the study involves the establishment of a robust relationship between time and concentration by integrating the equation governing the degradation of the dye. Additionally, the determination of the rate constant, derived from the gradients of the graphs, attests to the model’s fitting accuracy. Intriguingly, the outcomes of this analysis reveal no discernible structural changes in the dye. The accuracy of the model is further underscored by the establishment of linear relations derived from experimental data. Summarily, this kinetic study provides invaluable insights into the multifaceted impact of ultrasound energy and the Fe 2 O 3 catalytic influence on both the degradation kinetics of the dye. The comprehensive nature of the investigation enhances our understanding of the intricate processes involved, contributing significantly to the broader field of water treatment and dye removal from aqueous environments.