Band 19, Heft 1

Formaldehyde is one of the vital chemicals produced by industries, transports, and domestic products. Formaldehyde emissions adversely affect human health and it is well known for causing irritation and nasal tumors. The major aim of the modern indoor formaldehyde control study is in view of energy capacity, product selectivity, security, and durability for efficient removal of formaldehyde. The two important methods to control this harmful chemical in the indoor environments are photocatalytic oxidation and catalytic oxidation with noble metals and transition metal oxides. By harmonizing different traditional photocatalytic and catalytic oxidation technologies that have been evolved already, here we give a review of previously developed efforts to degrade indoor formaldehyde. The major concern in this article is based on getting the degradation of formaldehyde at ambient temperature. In this article, different aspects of these two methods with their merits and demerits are discussed. The possible effects of operating parameters like preparation methods, support, the effect of light intensity in photocatalytic oxidation, relative humidity, etc. have been discussed comprehensively.

Gas-liquid volumetric liquid-phase mass transfer coefficient ( k L a ) was studied in a slurry bubble column at the conditions mimicking Fischer–Tropsch synthesis. To avoid the hydrodynamic disturbances due to the gas switching, oxygen enriched air dynamic absorption method was used. Influence of reactor models (CSTR, ADM and RCFD) on the volumetric mass transfer coefficient was investigated. Effect of operating pressure, superficial gas velocity and solids loading were investigated. From the reactor models investigated, it is recommended to use ADM model for k L a study. If the CSTR model is used, applicability of the model should be checked. With increase in the superficial gas velocity and operating pressure, volumetric liquid-phase mass transfer coefficient increases, while it decreases with the solids loading corroborating with the literature.

In order to study the process of Fe 3 O 4 reduction by melt electro-deoxidation. Electrochemical method was used to analyze the reduction mechanism of Fe 3 O 4 in NaCl-CaCl 2 melts. The effects of cell voltage and time on the product were discussed through constant cell voltage electrolysis. The results showed: (1) The reduction of solid Fe 3 O 4 to metallic Fe is a two-step process for obtaining electrons. (2) The transformation process (600 min, 0–1.0 V) of the electrolysis products with the increase of the cell voltage is as follows: Fe 3 O 4 → FeO → FeO + Fe → Fe. (3) The intermediate product Ca 2 Fe 2 O 5 was formed (2.0 V, 10–300 min), which inhibited the deoxygenation process in the early stage of the reaction. When the electrolysis time exceeds 60 min, the main reaction is the reduction of Ca 2 Fe 2 O 5 to Fe.

The influences of loose gas on gas-solid flows in a large-scale circulating fluidized bed (CFB) gasification reactor were investigated using full-loop numerical simulation. The two-fluid model was coupled with the QC-energy minimization in multi-scale theory (EMMS) gas-solid drag model to simulate the fluidization in the CFB reactor. Effects of the loose gas flow rate, Q , on the solid mass circulation rate and the cyclone separation efficiency were analyzed. The study found different effects depending on Q : First, the particles in the loop seal and the standpipe tended to become more densely packed with decreasing loose gas flow rate, leading to the reduction in the overall circulation rate. The minimum Q that can affect the solid mass circulation rate is about 2.5% of the fluidized gas flow rate. Second, the sealing gas capability of the particles is enhanced as the loose gas flow rate decreases, which reduces the gas leakage into the cyclones and improves their separation efficiency. The best loose gas flow rates are equal to 2.5% of the fluidized gas flow rate at the various supply positions. In addition, the cyclone separation efficiency is correlated with the gas leakage to predict the separation efficiency during industrial operation.

Traditional methods for measuring the residence time distribution (RTD) of particles in a fluidized bed are complex and time-consuming. To this regard, the present work proposes a new measurement method with remarkable efficiency based on digital image analysis. The dyed tracers are recognized in the images of the samples due to the difference of colors from bed materials. The HSV and the well-known RGB color space were employed to distinguish the tracers. By enhancing the Saturation and the Value in HSV and adjusting the gray range of images, the recognition error is effectively reduced. Then the pixels representing the tracers are distinguished, based on which the concentration of the tracers and RTD are measured. The efficiency, accuracy and repeatability of the method were validated by RTD measurements experiments. The method is also fit for distinguishing the target particles from multi-component systems consisting of particles of different colors.

CO 2 hydrate-based desalination (CHBD) has been developing for decades to meet the global demands of decreasing carbon dioxide (CO 2 ) emissions. In this work, the CO 2 was captured from the simulated flue gas which consists of 18.30 mol% carbon dioxide and 81.70 mol% nitrogen in the presence of tetra-n-butyl ammonium bromide (TBAB) + cyclopentane (CP) + glucoamylase. Then the phase equilibrium data of CO 2 hydrate were measured by the method of isochoric pressure-search. Among the seven cases with same concentration of TBAB (0.29 mol%) and CP (5.00 vol%) and different glucoamylase proportions (ranging from 0.00 to 20.00 wt%), the optimum concentration of glucoamylase in the mixed promoters was 3.00 wt%. The phase equilibrium data was calculated by the modified van der Waals–Platteeuw (vdW–P) model with a modification of vapor pressure of water in the empty hydrate lattice. The Peng–Robinson equation of state was used to calculate the fugacity of gas. The maximum average absolute deviation was 4.09% between the calculated results and the experimental results. It revealed that the calculated results were in good agreement with the experimental results.

The reaction of isopropyl alcohol with acetic acid was carried out in an isothermal batch reactor in presence of solid resin catalyst to produce isopropyl acetate and water. A novel solid resin catalyst Indion 140 was used in the present study. The temperature of reaction mixture was maintained in the range of 333.15 – 363.15 K. The effects of reaction temperature, catalyst loading, mole ratio, size of catalyst, agitation speed were investigated on acetic acid conversion. Further, pseudo-homogeneous kinetic model was developed for the catalyzed reaction. The forward reaction rate constants and activation energies were determined from the Arrhenius plot. The forward and backward activation energies are found to 53,459 J/mol and 54,748 J/mol, respectively. The heat of reaction is −1.289 kJ/mol with Indion 140 catalyst. The mathematical equation was developed for frequency factor as function of the catalyst loading and found that it follows a linear relationship between frequency factor and catalyst loading. The simulations were performed for pseudo homogeneous kinetic model and found that the model is able to predict the experimental data very well. The developed kinetic equation is useful for the simulation of a reactive distillation column for the synthesis of isopropyl acetate.