Volume 21, Issue 8

The fluid in the reactor can be poorly mixed, so an eccentric impeller is proposed to improve the fluid mixing efficiency. In this investigation, numerical simulations and cadmium removal experiments for the purification of zinc sulfate solution were conducted. The effect of eccentric impellers on the purification efficiency was discussed. The mechanism of the effect of concentric and eccentric arrangement of stirring impellers on mixing in the stirred tank was elucidated. The results showed that the average axial velocity of the eccentric impeller stirring system (EIS) was 131.52% of that of the concentric stirring system (CS) and 134.23% of that of the eccentric stirring system (ES). In the purification and removal of cadmium in the zinc hydrometallurgy experiment, unit ion purification energy was introduced to quantify the energy consumed for each 1% of Cd2+ removed. The eccentric impeller shortens the reaction time by 40% and reduces the reaction energy consumption by 31.8% compared to the non-eccentric impeller. Compared to CS and ES, EIS disrupts the periodicity of fluid flow and facilitates the destruction of isolated mixing regions. EIS can enhance mechanical stirring to improve purification efficiency.

A novel interconnected screw reactor was proposed to convert biomass to bio-oil and bio-char in this study. This reactor is expected to achieve direct heating of pyrolysis feedstocks and increase the reactor processing capacity through the recycling of biochar between the inner and outer screw. Here, we simulated the biomass particle flow and reaction process in this interconnected reactor by an extended discrete element method (DEM), the effect of char circulation on the reactor temperature distribution and the product yields are investigated. The results show that the char circulation increased the heating rate of biomass. At the inner and outer screw speed of 10 rpm and 1 rpm, the char circulation can reach 5.15 kg/h and the average temperature of biomass under the char circulation is about 30 °C higher than that without char circulation. The reaction simulation results show that at 500 °C, the yield of char, bio-oil and non-condensable gas are 18.9%, 40.6% and 40.5% respectively. The predicted product yields of char, bio-oil and non-condensable gas are also in good agreement with the experimental measurements.

The poor mixing caused by zinc powder deposition in purification process is a serious problem which can’t be avoided in treatment of zinc-containing solid waste. Here, to enhance the purification efficiency of zinc-containing solid waste treatment reactor, two kinds of multi-blade combined stirring systems are compared with single layer four straight-blade and double-layer straight-blade (DFB) stirring systems which are traditionally chosen by industry. This study simulated and explored the flow field characteristics and purification effects of these four kinds of stirred-tank reactor, further proposes the unit ion purification energy (UIPE) as a criterion for purification energy consumption and effect evaluation. The results show that multi-blade combined (MBC) stirring system enhances axial flow by 12.56% in water. Meanwhile it effectively inhibits the growth of isolated mixing region which scope has decreased by 56.25%. In high viscosity Carboxymethylcellulose sodium solution, the fluid axial speed can be increased by up to 1407 times with MBC. MBC can increase the purification rate by 24.79% while the UIPE decreases by 29.45% compared with DFB which is used in industrial purification process. MBC paddle has exhibited a wide range of fluid viscosity applicability and axial velocity improvement effect. The improvement increases collisions between the impurity particles and the zinc powder particles, which increased rate of substitution reactions. The application of MBC solves the purification problem in the process of treating zinc-containing solid waste.

Many of the modern refineries are founded on converting/upgrading the heavy bases of low value to lighter products by higher added value like gasoline, jet fuel and diesel fuel. In this work, some process configurations in heavy refinery cracking, converting and treating are technically and economically evaluated. In this purpose, four process configurations for refinery plants are suggested. These processes are evaluated and analyzed to obtain the most optimal configurations with the aim of achieving the most valuable refinery products. The difference of the processes is in heavy residue conversion and processing. These processes are included the Asphalt Air Blowing Unit (AABU, Type 1), Delayed Coker Unit (DCU, Type 2), Heavy Residue Hydro-Conversion (HRH, Type 3) and Solvent De-Asphalting (SDA, Type 4). The units are common in mentioned refineries cases and just ABU, HCU, DCU, HRH and SDA are different. In economic consideration, the payout period is considered as one of the standard methods of assessing the economic projects and economically estimating them. As results, the highest rate of gasoline is recorded in the refinery type of DCU unit and the highest amount of LPG/C4/C3, kerosene and gasoline production observed in refinery type of HRH unit. The construction of refinery with ABU unit has minimum investment (980 million $) and highest rate of return (19.4).

In this article, the Eulerian–Eulerian TFM model is used to simulate the fluidization of the synthesis process of organosilicon monomers. A new method for analyzing the gas-solid fluidization characteristics is proposed by combining the gas-solid two-phase flow evolution formula with the parameters such as particle concentration and bed voidage. On this basis, the fluidization characteristics of silicon powder particles at constant velocity and variable velocity are compared, and the fluidization characteristics of silicon powder particles with different particle sizes under five sets of variable velocity are discussed. The simulation results show that compared with constant velocity, the mean bed voidage is 0.55 when silicon particles adopt variable velocity, which can not only keep silicon particles fully fluidized but also improve the problem of poor gas-solid contact. For silicon particles with particle diameters of 300.1–515 μm, variable velocity fluidization has the advantages of uniform bed distribution and sufficient gas-solid fluidization. In the five groups of variable velocity function, when the inlet gas velocity and time are the quadratic functions of the opening upward, the fluctuation of pressure fluctuation is small, and the maximum fluctuation range of particle solid phase distribution is only 0.13, indicating that the heat and mass transfer efficiency between silicon particles is better, the gas-solid mixing is sufficient, and the gas-solid fluidization quality is better.

CSTR operations entailing high nonlinearity and complexity such as multiple input and output steady-states present a real challenge to chemical engineers and process designers. The input multiplicity in chemical reactions leads to control probems such as process instability and low efficiency. Therefore, it is of critical importance to predict and avoid the multiplicity regions during reactor operation. Since the bifurcation analysis of biochemical processes with nonideal mixing has been carried out by the authors in the previous publication (Yang, C. Y., D. C. Tsai, and Y. S. Chien. 2021. “The Strategy Developed for High Conversion and the Multiplicity Problems of Biochemical Reaction in a Real CSTR with Cholette’s Model.” International Journal of Chemical Reactor Engineering 19: 1245–70), the goal of the present work is to use Sturm’s method, Routh stability criteria and the discriminator roots method with the tangent analysis method to derive the input multiplicity conditions in substrate inhibition in a real CSTR based on Chollete’s model. Four kinetic schemes are used in the analysis as examples to show that all three methods can precisely obtain the bifurcation starting point for the input multiplicity. In addition to the multiple input steady-states, the start-up diagram obtained by the discriminator root method is of critical importance to avoid operating in the input multiplicity regions.

Many studies of the photocatalytic oxidation process investigated on the removal efficiency and other variables of the input and output photoreactor. In the laboratory scale, it’s impossible, examination of the removal efficiency details, such as mass and energy transfer with air flow rate. Also, experimental methods request time consumption and money. For this reason, the simulation method can be used. The aim of this study was to prove that the validation of modeling approach in the photocatalytic oxidation process in the removal of toluene from air. Investigation of bed surface morphology, with FESEM, BET and TGA, shows acceptable monotonous of TiO 2 nanoparticles on the ss plate. Furthermore, it was observed good adherence of nanoparticles on it. Experimental results on photocatalytic bed surface exhibited in the toluene concentration range of 10–40 ppm and flow rate of 2–5 l/min, with increasing flow and decreasing concentration, removal efficiency increased. The optimum removal point was 59% and 25 g/m 3  min for 3.75 ppm and 5.61 l/min. For bed surface performance, the correlation between experimental results and simulation data was obtained 98%. According to the results, the photocatalytic oxidation process performed well for removal of low concentration of toluene from air. In addition, the obtained simulation method eliminated the random factors which can be affected by photocatalytic bed surface and it can show dependence of results based on reality.

In this work, the process parameters of batch hydrothermal liquefaction of kitchen residue were optimized with the yield of bio-oil as reference, including reaction temperature, residence time and initial pressure. According to the experimental results, the bio-oil yield of kitchen residue was the highest (39.73%) under the reaction conditions of 6 MPa, 300 °C and 30 min. The elemental content and components of bio-oil were characterized by organic element analyzer and gas chromatography/mass spectrometer. The surface and structural properties of biochar were detected and analyzed by Fourier transform infrared spectrometer, scanning electron microscope and surface area and porosity analyzer.

In order to seek efficient resource utilization, the carbonization of agricultural and forestry wastes through microwave pyrolysis technology is an important research hotspot to develop value-added products. The main objective is to produce value-added biochar through microwave pyrolysis of peanut shell in this study. The product yields, functional groups, and biochar HHVs caused by pyrolysis temperature (400, 450, 500, 550, and 600 °C), microwave power (350, 450, 550, 650, and 750 W), and residence time (10, 20, 30, 40, and 50 min) were investigated, and the energy recovery efficiencies were evaluated. It was obtained that the biochar yield declined monotonously within the range of 45.3–86.0 wt% with the enhancement of pyrolysis temperature, microwave power, or residence time. The pyrolysis temperature of 400 °C, microwave power of 350 W, and residence time of 10 min generated the maximum biochar yield (86.0 wt%). The value-added biochar was obtained with high HHV (20.15–31.02 MJ/kg) and abundant oxygen-contained functional groups (C–O bonds and C=O bonds). The maximum energy recovery efficiency during the whole process reached 97.96%. The results indicated that the peanut shell could reach high biochar yield through microwave pyrolysis, and potentially be transformed into value-added products with high energy recovery efficiency.

A type of MCM-41 supported dual imidazolium ionic liquids have been synthesized and efficiently used as catalysts in the sustainable chemical conversion of CO 2 and epoxides into cyclic carbonates. It was shown that the highest efficiency was achieved in the cycloaddition of a variety of epoxides and CO 2 in the presence of the MCM-41@DILSCN solid catalyst under mild conditions. More interestingly, the catalyst was stable, very active, robust, and displayed good recyclability without significant loss of catalytic activity after six consecutive cycles during the process. Overall, the present protocol of synthesizing cyclic carbonates under solvent free conditions using MCM-41@DILSCN is promising for industrial applications.