Aerosol and Air Quality Research
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社團法人台灣氣膠研究學會,正常發行
選擇卷期
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Electrical forces can be applied to enhance fabric filters' ability to remove fine particles. To this end, we developed an experimental apparatus consisting of a conventional wire-tube particle precharger and fibrous filters positioned in a generated reversed external electric field. The charging and collection processes were separately accomplished in two stages, and we evaluated the device's ability to filter filtration-charged particles with a diameter of ≤ 2.5 μm. This device exhibited a higher electric field strength, higher collection efficiency, lower pressure drop, and lower electric potential than conventional devices due to the positioning of the wire and grounded electrodes close to the bag and the repulsion of the charged particles by the reversed electric field. When the face velocity was 2.5 m min^(-1), the collection efficiency for the charged particles with the reversed electric field was 8.4% and 64.4% higher than the efficiencies for the charged and uncharged particles, respectively, without the field. The charged particles also displayed a pressure drop when the field was applied that was 10% lower and 5% higher than those of the uncharged and charged particles, respectively, when the field was absent. A negative direct current supply was necessary to direct the deposition of the charged particles, and neither a spark discharge nor a back corona was observed while using the reversed-electric-field apparatus, which, according to our results, enables the removal of filtration-charged particles at face velocities beyond the usual range.
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In this study, a series of rare earth monosubstituted Dawson-type polyoxometalates were synthesized for highly effective removal of hydrogen sulfide (H_2S). The unused, used and regenerated polyoxometalates were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results confirmed that K_(17)[Pr(P_2Mo_(17)O_(61))_2] could maintain a complete Dawson-type structure even after absorption and regeneration. H_2S absorption study showed that K_(17)[Pr(P_2Mo_(17)O_(61))_2] had the remarkable desulfurization and regeneration capabilities. Optimization experiments showed that K_(17)[Pr(P_2Mo_(17)O_(61))_2] under the condition of low H_2S concentration or high dosage of K_(17)[Pr(P_2Mo_(17)O_(61))_2] had the ideal desulfurization performance. An appropriate temperature of 25°C is necessary for high removal efficiency. The optimum pH value for desulfurization is 6.8. The desulfurization product was proved to be SO_4^(2-).
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Ionic liquids and heteropoly compounds have been found to be effective systems for H_2S removal due to their unique properties. This study, which investigated the absorption kinetics of these new systems, continues our earlier research. Specifically, the macro kinetic characteristics of the H_2S absorption for three systems, viz., a [Bmim]_3PMo_(12)O_(40)/BmimCl solution, an aqueous solution of peroxo phosphomolybdic acid and an aqueous solution of CuH_2PMo_(11)VO_(40), were determined using a gas-liquid reaction cell. The gas and liquid phase mass transfer coefficients were measured, and the activation energy was calculated. The H_2S absorption for the [Bmim]_3PMo_(12)O_(40)/BmimCl solution can be expressed as a macro kinetic equation: N_(H2S) = 6.6 × 10^(-2)∙[exp(-1064/T)]∙C_(H2S)^(1.120)∙C_([Bmim]3PMo12O40)^(0.099). For the aqueous solutions of peroxo phosphomolybdic acid and CuH_2PMo_(11)VO_(40), the absorption can be expressed as N_(H2S) = 2.68 × 10^(-6)∙[exp(-790/T)]∙C_(H2S)^(0.252)∙C_(PHPMo)^(0.131) and N_(H2S) = 1.02 × 10^(-6)∙[exp(607/T)]∙C_(H2S)^(0.510)∙C_(CuH2PMo11VO40)^(0.431), respectively.
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With the implementation of ultra-low emission systems in coal-fired power plants in China, the emission of sulfur trioxide (SO_3) has become an important issue in pollution control. However, systematic research and evaluation of SO_3 control routes based on the existing ultra-low emission systems are still lacking. We assigned 148 coal-fired power plants to four categories based on their ultra-low emission control routes and selected a representative power plant from each category for comprehensive field testing. The results indicated great variability in the synergistic SO_3 removal capability of different air pollution control devices and routes, resulting in removal efficiencies that ranged from 27% to 94%. Control Route 1, which lacked both a low-low temperature electrostatic precipitator (LLTESP) and a wet electrostatic precipitator (WESP), exhibited the lowest removal efficiency. The two routes equipped with either an LLTESP or a WESP (Control Routes 2 and 3) reduced the SO_3 concentration in the flue gas produced by medium-sulfur-coal combustion to below 10 mg m^(-3), whereas Control Route 4, which utilized both an LLTESP and a WESP, reduced the SO_3 concentration to below 5 mg m^(-3). Furthermore, sampling the emissions of the 148 power plants revealed that only 14% of the power plants complied with the 5 mg m^(-3) standard for SO_3, although 44% and 64% of them complied with the 10 mg m^(-3) and the 20 mg m^(-3) standard, respectively. Our study evaluated the control routes within the context of the whole process, which can guide subsequent research and engineering practices.
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This work proposed and optimized a three-stage membrane process for CO_2 separation. The results of this study revealed that the membrane technology is a suitable process for the CO_2 separation in a higher concentration. In addition, the MATLAB was used to simulate and obtain the optimal operational parameters for a three-stage membrane process. This work established a partial cycle and recovered the CO_2 from the permeation side of second-stage membrane that enhance a higher purity CO_2 gas stream. The results of this study indicated that when the CO_2 concentration was higher than 50% and at a flow rate of 100000 Nm^3 d^(-1), the CO_2 separation could be achieved at the optimal operation condition. Under the conditions that the membrane areas were 2400, 3800, and 1800 m^2 for the first-, second-, and third-stage membrane, respectively and the operational pressure at first- and third stage membrane were 3.0 and 2.5 MPa, respectively, the CO_2 separation fraction was higher than 90% and CH_4 loss rate was lower than 5%. The results of this study have a high potential for the practical application.
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Chemical adsorption is a mature post-combustion technology for CO_2 capture from large-scale power plants. At present, the traditional monoethanola mine (MEA) absorbent has a few drawbacks, including a low absorption rate, solvent degradation, and high energy consumption, which can restrict the development of absorption technology. Therefore, the application of hydroxyethyl ethylenediamine (AEE) has attracted increasing attention in recent years. In the past, the absorbent performance test was usually measured for a single use, where changes in the performance were rarely mentioned after several absorbent cycles. In the current work, the absorption and desorption performance of AEE absorbents at different concentrations for multiple cycles are investigated. The experimental results indicate that (1) 10 wt% AEE has a higher absorption rate; (2) 20 wt% AEE has a higher absorption, desorption rate, and degree of regeneration, but has higher energy consumption. (3) When the temperature reaches about 85℃, the desorption rate of three different concentrations reaches the highest level, and the desorption rate increases significantly with increases in the solution concentration. (4) After several cycles, the desorption rate and energy consumption of AEE solutions are always keep a great state, so the AEE solution can be used repeatedly.