Volume 20, Issue 9

This work was aimed at optimizing the adsorbent mass and contact time and evaluating the performance of two-stage batch adsorber of NaOH-activated coconut shell carbon for methylene blue removal. To decrease the dye concentration from 1000 to 89.4 mg/L at any effluent volumes, the two-stage adsorber displays a small mass saving of 0.33% because of the high adsorbent affinity towards methylene blue at 1.80 L/mg. Meanwhile, the contact time can be minimized by 97.6% as opposed to that in one-stage adsorber. The sensitivity analysis of affinity on mass minimization shows a significant saving of 28.5% when the affinity is reduced to 0.01 L/mg. The response surface methodology was used to optimize the two-stage absorber for methylene blue removal, wherein the most significant parameter is the contact time.

Tri-reforming process of methane has been considered as an important chemical process for syngas production. The aim of this study is modeling and optimization of methane Tri-reforming slurry bubble column reactor (SBCR). A one-dimensional heterogeneous model with plug flow pattern for gas phase and an axial dispersion pattern for liquid-solid suspension has been developed for modeling of SBCR. differential evolution (DE) approach has been used for the optimization of Tri-reforming slurry reactor operating conditions. The effect of operating parameters such as inlet temperature, the ratios of O 2 /CH 4 , H 2 O/CH 4 , and CO 2 /CH 4 on the temperature of gas, methane conversion, hydrogen production, and H 2 /Co ratio in the output of reactor are investigated. Methane conversion, hydrogen yield, and H 2 /Co ratio in optimization conditions were obtained 92%, 1.81, and 1.76, respectively. The results suggest that employment this type of reactor could be feasible and beneficial.

Since the heat transfer coefficient of supercritical carbon dioxide (S-CO 2 ) is approximately 1/2–2/3 of traditional steam boiler, the S-CO 2 boiler structure, cooling wall arrangement and combustion system is different from traditional boiler configuration. This paper takes a 1000 MW S-CO 2 coal-fired boiler with partial expansion furnace and partial flow strategy arrangement for cooling wall as research object, the coal combustion and NO x generation characteristics in the furnace were numerically examined with the flue gas recirculation rate of 0–35%. The calculation results show that under staged combustion, the flue gas recirculation increases the ignition temperature of the pulverized coal and reduces the combustion temperature. And the expansion of the upper furnace further reduces gas temperature. Besides, as the flue gas recirculation rate increases, the gas temperature decreases. The flue gas recirculation may lower the production of NO x in the main combustion zone, and reduce the production of NO x further in the expansion zone. The average NO x concentration at the outlet decreases from 439 to 365 ppm when the flue gas recirculation rate increases from 0 to 27%. While the flue gas recirculation rate increases from 27% to 35%, the average NO x concentration is not changed obviously.

Taylor finger is characterized by a single elongated air bubble that grows upward during the drainage of liquid from closed top vertical tubes. The characteristic of the Taylor finger is similar to the Taylor bubble commonly observed in gas–liquid two-phase flow. During the upward growth of the Taylor finger, liquid from the tube drains as a thin film around it. The exact prediction of film thickness is important in several engineering designs and process calculations such as the design of contacting devices, two-phase flow through porous media, boiling in tubes, and monolith reactors. The present study proposes an experimental technique to estimate the thickness of the draining liquid film. Based on experiments an empirical model has been proposed for non-dimensional film thickness in the inviscid region. The proposed model agrees well with the experimental data and equation proposed in published literatures (Davies, R. M., and G. Taylor. 1950. “The Mechanics of Large Bubbles Rising Through Extended Liquids and Through Liquids in Tubes.” Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 200, 375–90; Dukler, A. E., and J. Fabre. 1994. “Gas-Liquid Slug Flow.” Multiphase Science and Technology 8: 1–4; Fabre, J., and A. Liné. 1992. “Modeling of Two-Phase Slug Flow.” Annual Review of Fluid Mechanics 24: 21–46).

The vortex cavitation technology shows a great development potential for antibiotic wastewater treatment. We have designed a novel swirling vortex cavitator for tetracycline degradation in aqueous solution. By Computational Fluid Dynamics (CFD) simulation using ANSYS CFX flow field calculation software, it was found that the vortex cavitator could form a low-pressure area far lower than the saturated vapor pressure at experimental temperature, resulting in generation of obvious vortex cavitation effect, which also proved by the concentration of hydroxyl radical of 4.58 μmol/L measured by methylene blue method. Moreover, the tetracycline degradation process may be mainly caused by the oxidation of hydroxyl radicals. The batch experiments results showed when the degradation time was 30 min, the vortex cavitator had a good degradation ability of tetracycline in pH range of 5.0–9.0. The degradation efficiency of 2.0 mg/L tetracycline solution was 76.45% within 50 min at pH 7.0. The possible intermediate products of tetracycline were determined by HPLC-MS Spectrometry. A series of reactions including hydroxylation, decarbonylation and C–N bond cleavage, ring-opening, and removing two methyl groups in the carbon atom ring, occur during the degradation.

To deal with the notorious shuttle behavior and sluggish conversion of lithium polysulfides (LiPSs), heteroatoms doping and defects creating are practical strategies for improving capture and catalytic conversion of LiPSs. In this work, O doped porous carbon materials (OPC) with a 3D hierarchical structure, consisting of 2–4 μm carbon sheets decorated with macrospores of 0.2–0.4 μm, was fabricated with MgO template. It is found that the increasing the carbonization temperature and the amount of MgO will make OPC rich in oxygen functional groups and defect sites. Electrochemical measures show that the OPC 12–800 achieves reversible capacity (an initial discharge specific capacity of 1448.4 mAh g −1 at current density of 0.1 C) and cycling performance (717.7 mAh g −1 at 2 C over 200 cycles). The excellent electrochemical performance is attributed to the hierarchical porous structure, abundant C–O/C=O and defects, which effectively adsorbs polysulfides and promote faster redox reaction of LiPSs. This study provides an alternative to improve the performance of carbon materials as host of Li–S batteries by regulating the types of oxygen-containing functional groups and defects on carbon surface.

Recently, many studies are dealing with developments of Metal-Organic Frameworks (MOFs), especially MIL-53(Al), which shows high thermal and mechanical stability. Among these, optimizing the synthesis condition of MIL-53(Al) to obtain appropriate characteristics has attracted much attention in academia and the industry. Here, the effect of synthesis time and ligand to metal molar ratio on the hydrothermal synthesis of MIL-53(Al) are pursued. The synthesized MIL-53(Al) samples are characterized by X-ray diffraction (XRD), the Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), thermal gravimetric analysis (TGA), and nitrogen adsorption-desorption technique (BET). The present study shows that MIL-53(Al) can be conventionally synthesized with a high yield within a shorter reaction time than the previous studies. Furthermore, the catalytic activity of the optimized MIL-53(Al) in the pure and Mn-doped form is studied in a methanol dehydration reaction. It is thus inferred that this popular MOF in the Mn/MIL-53(Al) form has a high activity and DME selectivity during methanol conversion. Our present results confirm the merits of employing the MIL-53(Al) as a catalyst in methanol to DME conversion, which can be an avenue for the practical application of acidic catalyst.

In the process of immobilizing the enzyme, the overflow of enzyme and the decrease of enzyme activity are very serious. In order to improve the stable binding between enzyme and carrier, a kind of porous magnetic chitosan microsphere with appropriate pore size was successfully prepared by adjusting the size of pore-forming agent in this paper. The rough porous structure is favorable for the adsorption of enzyme and the catalytic action of enzyme on substrate. The results showed that when the pore size of the microspheres was at 790.15 ± 250.91 nm, the protein loading and enzyme activity of GOD could be increased effectively, which could reach 58.28 ± 2.64 mg/g and 16.93 ± 0.14 U, respectively. The co-immobilization of CAT and GOD eliminated the harmful by-product H 2 O 2 in time and effectively solved the problem of continuous deactivation of GOD in the reaction process. When the mass ratio of PMCSM/GOD/CAT was 100/6.02/10.96 (mg/mg/mg), the relative enzyme activity of GOD reached the highest (133.32 ± 0.68%). The thermal stability and pH stability of the enzyme were greatly improved after co-immobilization. The relative enzyme activity of PMCSM@GOD@CAT was 57.27 ± 3.04% at 60 °C, while that of free GOD was only 28.76 ± 4.10%. The relative enzyme activity of PMCSM@GOD@CAT was above 63% at pH 5–10, while the relative enzyme activity of free GOD was only 4.98 ± 0.72% at pH 10. The yield of sodium gluconate from 50 mL 250 mg/mL glucose catalyzed by PMCSM@GOD@CAT loading 60.2 mg GOD was 96.19 ± 0.79% at pH 6.0 and 30 °C, and the reaction lasted 6 h. The relative enzyme activity of PMCSM@GOD@CAT remained 69.77 ± 0.78% after repeated use for 10 times. After 30 days of storage, PMCSM@GOD@CAT maintained its initial activity of 76.52 ± 1.41%. The immobilized process studied in this paper provides a theoretical basis for the production of sodium gluconate by double enzyme directly catalyzing and lays a certain foundation for the application of immobilized enzyme in the future chemical industry and food industry.

Scale-up studies of fluidized beds are important for numerous fields. Fluidization in a multi-ring inclined nozzle spout-fluid bed (MRIN spout-fluid bed) is one of the most critical factors that affect the coating efficiency and uniformity of tri-structural isotropic (TRISO) nuclear particles in the fluidized bed chemical vapor deposition (FB-CVD) process. In this work, the flow pattern similarity principle was proposed to scale up a specially designed spout-fluid bed, which was aimed at maintaining the gas-solid contact efficiency, and was validated by electrical capacitance tomography (ECT) measurements. First, the traditional ECT method was developed for the specially designed MRIN spout-fluid bed according to the filling method. Then, the reconstruction algorithms were updated using the alternating direction multiplier method (ADMM) by introducing optimization constraints. The fluidization laws were investigated for different superficial gas velocities and distributor structures. We found that the gas distributor structure affected the merge point of the jets, which played an essential role in fluidization pattern changes. The statistically-based coefficient of variation (Cv) was proposed to distinguish the different flow patterns. Multi-ring spouting was then selected as a typical flow pattern for good fluidization and mixing, where the Cv ranged from 0.25 to 0.65. Then, the optimal design principles for the enlarged spout-fluid bed gas distributor were obtained. We determined that a smaller nozzle diameter (0.71 d 0 ), larger nozzle spacing (1.12 x 0 ), and slightly inclined angle (1.50 θ 0 ) could improve fluidization, and that nozzle spacing was the most important factor. This study may be beneficial for the industrial design of the FB-CVD process and for the fabrication of high-density nuclear fuel particles. Additionally, it could be presented to a more general audience for scaling-up fluidized beds with a complex distributor, which would be beneficial for the fluidization research community.