Enhanced photocatalytic oxidation of SO2 on TiO2 surface by Na2CO3 modification

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.cej.2018.05.128 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/The effects of Na2CO3 on the photocatalytic oxidation (PCO) of SO2 with UV irradiated TiO2 (P25) were studied using a fixed bed reactor. Na2CO3 was loaded onto P25 using a wet coating method. The PCO efficiency for SO2 with P25 was enhanced by 1.6 and 10.6 times using 0.05 M and 0.2 M Na2CO3 modified P25, respectively. The enhancement of the photocatalytic activity of P25 by Na2CO3 was observed only with the presence of water vapor. Low temperature (113 K) electron spinning resonance (ESR) analysis showed that Na2CO3 promoted the photoinduced electron-hole separation by trapping valance band holes and forming carbonate radicals (CO3−). The ESR spin trapping analyses showed a remarkable increase in the intensity of [DMPO-OH] adducts with the addition of Na2CO3. This increase phenomena indicates that more reactive species were formed on the P25 surface. The deposited Na2CO3 inhibited the recombination of electron-hole pairs and promoted the generation of hydroxyl radicals (OH), most likely through the photo-reduction of O2 adsorbed by the conduction band electrons. The generated •OH radicals reacted with SO2 rapidly and improved the PCO effectiveness of P25.National Key Research and Development Program of China ["2017YFB0603903"

FEDSM2002-31221 EFFECT OF TURBULENCE ON DRAG FORCE IN GAS-PARTICLE TWO-PHASE FLOW

ABSTRACT Effect of turbulence on drag force in gas-particle two-phase flow had been investigated using numerical simulation. In order to select an accurate turbulence model, some promising models, such as standard k-ε model, RNG k-ε model and Realizable k-ε model, had been examined through calculating the flow over a backward-facing step. RNG k-ε model performing better than others had been used to simulate the turbulence flow over a spherical particle. In computation, the turbulence intensity was ranged from 10% to 80%, and the turbulence length scale from 10 -5 m to 4m. Results show that the turbulence length scale had a small effect on the drag force, except at small length scale. Comparing with the drag on a particle in laminar flow, the turbulence intensity enhances it comparatively, especially at small particle Reynolds numbers, which differs from the previous publications

Moisture Adsorption Properties of Dried Lignite

Moisture adsorption properties of dried lignite were investigated experimentally and mathematically. Three kinds of lignite (Hailaer, Huolinhe, and Indonesia) with different water contents were tested with a machine that maintained a constant temperature and relative humidity. The obtained experimental adsorption data were applied to the Guggenheim, Anderson, and de Boer (GAB), modified Guggenheim, Anderson, and de Boer (MGAB), modified Oswin (MO), modified Henderson (MH), and modified Freundlich (MF) isotherm equations to test their applicability to dried lignite. The order of best fit of adsorption across the entire temperature and relative humidity range was MF > MGAB > GAB > MH > MO. On the basis of the experimental data, the MF equation was modified to consider the effect of the initial moisture content of dried lignite on the equilibrium water. The critical temperature and relative humidity values were obtained with the modified MF equation, which was then used to determine the moisture adsorption occurrence for the dried lignite with a specific moisture content under different environmental conditions. Shanghai and Guangzhou were the target-user locations of the dried lignite. The critical water content values were obtained to avoid the moisture adsorption. These values provided the theoretical guidelines for the target control of the lignite drying process and storage conditions

Enhancement of Mass Transfer between Flue Gas and Slurry in the Wet Flue Gas Desulfurization Spray Tower

This paper presents an enhancement method to improve the desulfurization performance of wet flue gas desulfurization (WFGD) by adding a flow pattern controlling (FPC) device in the spraying tower. The FPC device is characterized by a modular design and composed of FPC units that are fixed under the spraying layers of the desulfurization tower. Two kinds of FPC units, each with a different scale, are designed (i.e., unit A and unit B). The effects of the FPC unit and operational parameters on the desulfurization process are determined by experimentation. The experiments show that the FPC unit significantly improves the desulfurization performance compared to the common spraying column without an aperture plate. The flow regime significantly changes and large amounts of bubbles develop above the perforated plate in the FPC unit, which is beneficial to enhance gas–liquid mass transfer. The design style and structural parameters of the FPC unit both significantly influence the desulfurization performance. According to the results, optimal desulfurization performance is achieved with four holes and an aperture ratio of 0.65 for unit B. For <i>L</i>/<i>G</i> = 10 L/m³, the desulfurization efficiency of unit B reaches 77% (approximately 22% increase) with a pressure increase of 370 Pa. The relationship between the operational parameters and the different scale units is investigated under different test conditions. In addition, the results show that the range of improvement with the perforated plate is related to the gas–liquid flow regime in the unit. Finally, we attempt to build an empirical correlation formula of each influence factor on desulfurization efficiency and pressure drop based on the experimental results