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1.
A strong ionization dielectric barrier discharge was used to produce a high concentration of reactive oxygen species that were then injected into a simulated flue gas in a duct to remove SO2 by oxidation. Sulfuric acid (H2SO4) was produced through the following two reactions: (1) O3 oxidation of SO2–SO3, which then reacted with H2O to produce H2SO4; and (2) reaction of O2 + with H2O to produce ·OH radicals, which then rapidly and non-selectively oxidized SO2–H2SO4. When the molar ratio of reactive oxygen species to SO2 was 4:1, the SO2 removal efficiency was 94.6%, the energy consumption per cubic meter of flue gas was 13.3 Wh/m3, the concentration of recovered H2SO4 was 4.53 g/l, and the H2SO4 recovery efficiency was 28.8%. The H2O volume fraction in the simulated flue gas affected the SO2 removal efficiency, whereas the O2 and CO2 volume fractions did not. These results prove that oxidation by reactive oxygen species is a feasible method for flue gas desulfurization.  相似文献   

2.
Current gas ionization discharge techniques used in the removal of NOx from waste gases require large plasma sources, have high energy consumption, and may feature low NOx removal rates. We develop a system to generate reactive oxygen species through a strong ionization discharge, which is injected into a flow of simulated waste gas. The relative proportions and temperatures of input gases were controlled and the rate of consumption by reactive species was monitored. HNO3 oxidization products of NOx were also collected and measured. The molar ratio of reactive oxygen species to NO was optimized to improve the rate of NOx removal. A input gas temperature of 58–60 °C was also found to be optimal. The O2 volume fraction has almost no influence on NOx removal, while H2O volume fractions above 6 %, gave rise to NOx removal rates of 97.2 %. The present study addresses disadvantages of current gas ionization discharge and requires no catalyst, reducing agent or oxidant.  相似文献   

3.
Plasma–liquid interaction has already been a hotspot in the research field of plasma medicine. Aqueous reactive oxygen species (ROS) generated in this process are widely accepted playing a crucial role in plasma biomedical effects. In this paper, chemistry pathways among various aqueous ROS induced by He + O2 plasmas are investigated by a numerical model. Simulation results show that these aqueous ROS can be classified into two groups according to their production ways: the group of species including O, 1O2 and e directly produced in plasma, and the other group of species including O2 ?, H2O2, O3, etc. produced by liquid reactions. A key reaction chain of e → O2 ? → HO2(→ HO2 ?) → H2O2 is found to be important in the plasma-induced liquid chemistry. Furthermore, impacts of changes in plasma and solution conditions on aqueous ROS concentrations are studied as well. It is found that changes in plasma conditions (O2 ratio in the discharge gas/power density) can globally influence the concentrations of almost every aqueous ROS, while conditions changes of the treated liquid (pH/dissolved oxygen) only partially influence the concentrations of some specific species including O2 ?/HO2, O3 ?/HO3 and H2O2. The revelations of the liquid chemistry pathways and the dependence of ROS dosage on the treatment conditions offer a better understanding on the plasma–liquid interactions, as well as provide optimized dosage control approaches for biomedical applications.  相似文献   

4.
By utilizing a fully floating double electrical probe system, the conductivity of a linear atmospheric pressure plasma jet, utilizing nitrogen as process gas, was measured. The floating probe makes it possible to measure currents in the nanoamp range, in an environment where capacitive coupling of the probes to the powered electrodes is on the order of several kilovolts. Using a chemical kinetic model, the production of reactive nitrogen oxide and hydrogen-containing species through admixture of ambient humid air is determined and compared to the measured gas conductivity. The chemical kinetic model predicts an enhanced diffusion coefficient for admixture of O2 and H2O from ambient air of 2.7 cm2 s?1, compared to a literature value of 0.21 cm2 s?1, which is attributed to rapid mixing between the plasma jets and the surrounding air. The dominant charge carriers contributing to the conductivity, aside from electrons, are NO+, NO2 ? and NO3 ?. Upon admixture of O2 and H2O, the dominant neutral products formed in the N2 plasma jet are O, NO and N2O, while O2(1Δg) singlet oxygen is the only dominant excited species.  相似文献   

5.
In this work, ethylene epoxidation was investigated in a dielectric barrier discharge jet (DBDJ) with a separate ethylene/oxygen feed under oxygen lean conditions. The ethylene (C2H4) stream was directly injected behind the plasma zone in order to reduce all undesired reactions, including C2H4 cracking and further reactions, while the oxygen (O2) balanced with argon was fed through the plasma zone totally to maximize the formation of active oxygen species. The effects of various operating parameters, such as total feed flow rate, O2/C2H4 feed molar ratio, applied voltage, input frequency, and C2H4 feed position on the ethylene epoxidation activity, were investigated to determine the optimum operating conditions for this new DBDJ system. The highest ethylene oxide (EO) selectivity (55.2 %) and yield (27.6 %), as well as the lowest power consumption (3.3 × 10?21 and 6.0 × 10?21 Ws/molecule C2H4 converted and EO produced, respectively) were obtained at a total feed flow rate of 1,625 cm3/min (corresponding to a residence time of 0.022 s), an O2/C2H4 feed molar ratio of 0.25:1, an applied voltage of 9 kV, an input frequency of 300 Hz, and a C2H4 feed position of 3 mm behind the plasma zone. The superior activity of the ethylene epoxidation in the DBDJ system resulted from a small reaction volume as well as a separate ethylene/oxygen feed.  相似文献   

6.
The absolute yields of gaseous oxyfluorides SOF2, SO2F2, and SOF4 from negative, point-plane corona discharges in pressurized gas mixtures of SF6 with O2 and H2O enriched with18O2 and H2 18O have been measured using a gas chromatograph-mass spectrometer. The predominant SF6 oxidation mechanisms have been revealed from a determination of the relative18O and16O isotope content of the observed oxyfluoride by-product. The results are consistent with previously proposed production mechanisms and indicate that SOF2 and SO2F2 derive oxygen predominantly from H2O and O2, respectively, in slow, gas-phase reactions involving SF4, SF3, and SF2 that occur outside of the discharge region. The species SOF4 derives oxygen from both H2O and O2 through fast reactions in the active discharge region involving free radicals or ions such as OH and O, with SF5 and SF4.  相似文献   

7.
The Co-modified CeO2-TiO2 catalyst prepared by facile co-precipitation was used for efficient elemental mercury oxidation in flue gas. Results indicated that Co doping greatly enhanced the activity and SO2 resistance of the CeO2-TiO2 catalyst. In the presence of 5% O2, 500 ppm NO, 800 ppm SO2 and 3% H2O at 200 °C, the Hg0 removal efficiency of CeCo3/Ti could maintain at about 87% for a relatively long time. Characterizations of catalysts (BET, XRD, Raman spectroscopy, TEM, H2-TPR, O2-TPD, XPS, TG-MS and SO2-DRIFTS) were carried out to reveal the mechanism of Co modification on the redox ability, SO2 resistance and resultant mercury oxidation removal performance of catalyst. It was found that an interaction of Ce with Co promoted the dispersion of CeO2, increased chemisorbed oxygen concentration, and improved the oxygen storage capacity and the reducibility of catalyst, which was beneficial to the improvement of Hg0 oxidation removal. Hg0 would adsorb onto the catalyst and react with surface active oxygen species replenished by gas-phase O2 to be oxidized via Mars-Maessen mechanism. SO2 consumed the surface active oxygen species and resulted in the reduction of Ce4+ to Ce3+, which induced the deactivation of catalyst. The introduced Co in CeO2-TiO2 catalyst exerted the function of protecting Ce4+ from being poisoned by SO2 and thus promoted the sulfur resistance and Hg0 removal performance of the catalyst in the presence of SO2.  相似文献   

8.
Mercury emission from coal combustion has been the fourth biggest pollutant in China, following the dusts, SO2 and NOX. The technology of non-thermal plasma has been widely studied for oxidizing gaseous elemental mercury at low temperature. In this paper, a new method of combining non-thermal plasma with calcium oxide was proposed to remove elemental mercury from simulated flue gas. The effects of non-thermal plasma, input energy, combination mode of plasma and calcium oxide on Hg0 removal were investigated in a wire-cylinder non-thermal plasma reactor, whose energy was supplied by a high voltage alternating current power. The peak voltage and energy of the non-thermal plasma were measured by an oscilloscope and a high voltage probe (1000:1). The results showed that most of Hg0 was converted to oxidized mercury in simulated flue gas by non-thermal plasma treatment. The Hg0 removal efficiency of CaO was improved remarkably strengthened by the non-thermal plasma, which was closely related to input energy, and the maximum mercury removal efficiency was about 80 % at an optimal input energy. Through temperature-programmed decomposition and desorption and energy dispersive spectroscopy analysis, the majority of mercury species on CaO surface were Hg2O and HgO3 rather than HgO. Therefore, it can be concluded that O3 plays an important role in Hg0 oxidation under the condition of non-thermal plasma.  相似文献   

9.
A surface dielectric barrier discharge plasma reactor was employed to study Hg0 oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg0 oxidation efficiency and 13.7 μg kJ?1 of energy yield were obtained under a specific energy density (SED) of 7.9 J L?1. Increasing SED was beneficial for Hg0 oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg0 oxidation efficiency, but higher amount of Hg0 oxidation. Water vapor inhibited Hg0 oxidation because the generation of O3 was suppressed. The presence of NO remarkably restrained Hg0 oxidation, while SO2 showed little effect on Hg0 oxidation. Roles of active species in Hg0 oxidation were examined under different gas atmospheres (O2 and air), indicating that O3 played an important role in Hg0 oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.  相似文献   

10.
以蜂窝状陶瓷为载体,采用溶胶凝胶法和浸渍法制备了不同Fe/Ag负载量的Fe-Ag/Al_2O_3催化剂。以C_3H_6为还原剂,在模拟烟气条件下和200-700℃范围内,程序控温的陶瓷管流动反应器上进行了催化还原NO的性能评估。结果表明,7.2Fe/1.9Ag/20Al_2O_3/CM在500和550℃时催化C_3H_6还原NO的脱硝效率分别超过90%和达到100%。铁离子能有效地提高Ag/20Al_2O_3/CM催化剂抵抗烟气中的SO_2和H_2O的能力。结果表明,当烟气中含有体积分数为0.02%的SO2和8%的H_2O时,在500℃时7.2Fe/1.9Ag/20Al_2O_3/CM催化C_3H_6还原NO的脱硝效率不受影响,在6 h的连续实验中保持90%的脱硝效率而没有下降。而未经铁离子修饰的2Ag/20Al_2O_3/CM的催化活性则受烟气中的SO2和H_2O影响很大,0.02%的SO2和8%的H_2O分别使2Ag/20Al_2O_3/CM在500℃时催化C_3H_6还原NO的脱硝效率迅速从70%分别下降至46%和25%。XRD和SEM表征结果表明,经铁离子修饰后的7.2Fe/1.9Ag/20Al_2O_3/CM催化剂中,形成了AgFeO_2以及Fe~(3+),催化剂表面变得疏松多孔,形成以Fe_3O_4为主的针状和片状晶体。H_2-TPR结果表明,7.2Fe/1.9Ag/20Al_2O_3/CM比Ag/20Al_2O_3/CM在更宽的温度范围内具有更好的还原特性。吡啶吸附红外光谱(Py-FTIR)实验结果显示,Fe增加了催化剂表面的Lewis酸性位。  相似文献   

11.
Acetone, hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) are easily to produce triacetone triperoxide (TATP), which is an organic peroxide and a hazardous material. The aim of this study was to analyze the thermal hazard of various fire-extinguishing reagents mixed with TATP. Various functions of fire-extinguishing reagents may have different extent of reactions with TATP. Differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG) were used to detect the thermal hazard and to evaluate the effect of fire-extinguishing reagents mixed with TATP under fire condition. TATP decomposed rapidly and final decomposition was calculated before 200 °C. Therefore, heat of decomposition (ΔH d) of TATP was evaluated to be 2,500 J g?1 by DSC under 2 °C min?1 of heating rate. H2O2, acetone, and H2SO4 should not be mixed in a wastewater drum. TATP decomposed at 50 °C by DSC using O2 of reaction gas that is an exothermic reaction and can decompose a large amount of heat. Therefore, TATP was applied to assess thermal pyrolysis by DSC employing N2 of reaction gas that can analyze an endothermic reaction. Mass loss percentage of TATP was evaluated to be 100 % when the ambient temperature exceeds 110 °C by TG using O2 or N2 of reaction gas.  相似文献   

12.
This paper presents the development of a model framework for plasma-biofilm and plasma-tissue interactions that can link molecular simulation of plasma chemistry to functions at a cell population level or a tissue level. This is aided with a reactive penetration model for mass transfer of highly transient plasma species across the gas–liquid boundary and a panel of electrical and thermal thresholds considering pain sensation, protein denaturation and lethal electric currents. Application of this model reveals a number of previously little known findings, for example the penetration of plasma chemistry into highly hydrated biofilms is about 10–20 μm deep for low-power He–O2 plasma and this is closely correlated to the penetration of liquid-phase plasma chemistry dominated by O2 ?, H2O2, and HO2 or O2 ?, H2O2, and O3. Optimization by manipulating liquid-phase chemistry is expected to improve the penetration depth to 40–50 μm. For direct plasma treatment of skin tissues at radio frequencies, the key tolerance issue is thermal injuries even with a tissue temperature <50 °C and these can lead to induction of pain and protein denaturation at a small discharge density of 8–15 mA/cm2 over few tens of seconds. These and other results presented offer opportunities to improve plasma-biofilm and plasma-tissue interactions. The model framework reported may be further extended and can be used to non-biomedical applications of low-temperature plasmas.  相似文献   

13.
The Co–Mn/Ti–Ce catalyst prepared by sol–gel and impregnation method was evaluated for catalytic oxidation of Hg0 in the simulated flue gas compared with Co/TiO2 and Co–Mn/TiO2. The results showed that Co–Mn/Ti–Ce catalyst exhibited higher catalytic activity (around 93% Hg0 removal efficiency in the temperature of 150 °C with 6% O2, 400 ppm NO, 200 ppm SO2 and 3% H2O) than Co/TiO2 and Co–Mn/TiO2. Based on the characterization results of N2 adsorption–desorption, XRD, UV–Vis, XPS, H2-TPR and Hg-TPD, it could be concluded that the lower band gap, better reducibility and mercury adsorption capability and the presence of Co3+/Co2+, Mn4+/Mn3+ and Ce4+/Ce3+ redox couples as well as surface oxygen species contributed to the excellent Hg0 oxidation removal performance. In addition, well dispersion of active components and a synergetic effect among Co, Mn and Ce species might improve the activity further. A Mars–Maessen mechanism is thought to be involved in the Hg0 oxidation. The lattice oxygen derived from MnO x or CoO x would react with adsorbed Hg0 to form HgO and the consumption of lattice oxygen could be replenished by O2. For Co–Mn/Ti–Ce, MnO x?1 could be alternatively reoxidized by the lattice oxygen derived from adjacent CoO x and CeO x which is beneficial to the Hg0 oxidation.  相似文献   

14.
In order to investigate the gas‐phase mechanisms of the acid catalyzed degradation of ascorbic acid (AA) to furan, we undertook a mass spectrometric (ESI/TQ/MS) and theoretical investigation at the B3LYP/6‐31 + G(d,p) level of theory. The gaseous reactant species, the protonated AA, [C6H8O6]H+, were generated by electrospray ionization of a 10?3 M H2O/CH3OH (1 : 1) AA solution. In order to structurally characterize the gaseous [C6H8O6]H+ ionic reactants, we estimated the proton affinity and the gas‐phase basicity of AA by the extended Cooks's kinetic method and by computational methods at the B3LYP/6‐31 + G(d,p) level of theory. As expected, computational results identify the carbonyl oxygen atom (O2) of AA as the preferred protonation site. From the experimental proton affinity of 875.0 ± 12 kJ mol?1 and protonation entropy ΔSp 108.9 ± 2 J mol?1 K?1, a gas‐phase basicity value of AA of 842.5 ± 12 kJ mol?1 at 298 K was obtained, which is in agreement with the value issuing from quantum mechanical computations. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
The oxidation of Fe2+ in uranium leaching solutions with gaseous mixture of SO2 and air has been studied. The variables studied include H2SO4 concentration, temperature, SO2 concentration and time. The oxidation rate was founded to increase greatly with an increase in the solution temperature. The almost total oxidation of Fe2+ is readily achieved at 95 °C. By appropriately adjusting the temperature of solution and SO2/O2 in the gas, oxidation of ferrous ion and generation of sulphuric acid can be carried out. It was founded that solutions produced by such oxidation processing are very suitable for the uranium ore leaching.  相似文献   

16.
The chemical interaction between non-thermal plasma species and aqueous solutions is considered in the case of discharges in humid air burning over aqueous solutions with emphasis on the oxidizing and acidic effects resulting from formed peroxynitrite ONOO? and derived species, such as transient nitrite and stable HNO3. The oxidizing properties are mainly attributed to the systems ONOO?/ONOOH [E°(ONOOH/NO2) = 2.05 V/SHE], ·OH/H2O [E°(·OH/H2O) = 2.38 V/SHE] and to the matching dimer system H2O2/H2O [E°(H2O2/H2O) = 1.68 V/SHE]. ONOOH tentatively splits into reactive species, e.g., nitronium NO+ and nitrosonium NO 2 + cations. NO+ which also results from both ionization of ·NO and the presence of HNO2 in acidic medium, is involved in the amine diazotation/nitrosation degradation processes. NO 2 + requires a sensibly higher energy than NO+ to form and is considered with the nitration and the degradation of aromatic molecules. Such chemical properties are especially important for organic waste degradation and bacterial inactivation. The kinetic aspect is also considered as an immediate consequence of exposing an aqueous container to the discharge. The relevant chemical effects in the liquid result from direct and delayed exposure conditions. The so called delayed conditions involve both post-discharge (after switching off the discharge) and plasma activated water. An electrochemical model is proposed with special interest devoted to the chemical mechanism of bacterial inactivation under direct or delayed plasma conditions.  相似文献   

17.
BAO  Jingjing  YANG  Linjun  YAN  Jinpei 《中国化学》2009,27(11):2242-2248
The demercurization performance of wet flue gas desulfurization (WFGD) system was investigated by measuring mercury concentrations at the inlet and outlet of WFGD system with a QM201H mercury analyzer. The selected desulfurizer included NH3·H2O, NaOH, Na2CO3, Ca(OH)2 and CaCO3. The influences of adding oxidant and coagulant such as KMnO4, Fenton reagent, K2S2O8/CuSO4 and Na2S into desulfurization solutions were also studied. The results show that elemental mercury is the main component of gaseous mercury in coal‐fired flue gas, and the proportion of oxidized mercury is less than 36%. Oxidized mercury could be removed by WFGD system efficiently, and the removal efficiency could amount to 81.1%–92.6%. However, the concentration of elemental mercury slightly increased at the outlet of WFGD as a result of its insolubility and re‐emission. Therefore, the removal efficiency of gaseous mercury is only 13.3%–18.3%. The mercury removal efficiency of WFGD system increased with increasing the liquid‐gas ratio. In addition, adding KMnO4, Fenton reagent, K2S2O8/CuSO4 and Na2S into desulfurization solutions could increase the mercury removal efficiency obviously. Various additives have different effects, and Na2S is demonstrated to be the most efficient, in which a mercury removal efficiency of 67.2% can be reached.  相似文献   

18.
H3OLa(SO4)2 · 3 H2O: A New Acidic Sulfate of the Rare Earth Elements Colorless single crystals of H3OLa(SO4)2 · 3 H2O have been obtained by the reaction of La2O3 and sulfuric acid (80% H2SO4) at 150 °C. In the crystal structure (monoclinic, P21/c, Z = 4, a = 1119.5(5), b = 693.3(2), c = 1357.4(4) pm, β = 110.94(4)°) La3+ is ninefold coordinated by oxygen atoms which belong to five SO4 ions and three H2O molecules. One of sulfate groups acts as a bidentate ligand. Hydrogen bonding is observed with H2O molecules as donors and acceptors. Furthermore, strong hydrogen bonds are formed between the H3O+ ions and oxygen atoms of the SO42– groups.  相似文献   

19.
MnxOy/SBA-15 catalysts were prepared via the impregnation method and utilized for toluene removal in dielectric barrier discharge plasma at atmospheric pressure and room temperature. The catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and O2 temperature-programmed desorption methods. The characterization results indicated that manganese loading did not influence the 2D-hexagonal mesoporous structure of SBA-15. The catalyst had various oxidation states of manganese (Mn2+, Mn3+, and Mn4+), with Mn3+ being the dominant oxidation state. Toluene removal was investigated in the environment of pure N2 and 80 % N2 + 20 % O2 plasma, showing that the toluene removal efficiency and CO2 selectivity were noticeably increased by MnxOy/SBA-15, especially in the presence of 5 % Mn/SBA-15. This activity was closely related to the high dispersion of 5 % Mn on SBA-15 and the lowest reduction temperature exhibited by this catalyst. Mn loading increased the yield of CO2 in the N2 plasma and promoted the deep oxidation of toluene. During toluene oxidation, oxygen exchange might follow a pathway, wherein bulk oxygen was released from the MnxOy/SBA-15 surface; gas-phase O2 subsequently filled up the vacancies created on the oxide. Each of the manganese oxidation states played an important role; Mn2O3 was considered as a bridge for oxygen exchange between the gas phase and the catalyst, and Mn3O4 mediated transfer of oxygen between the catalyst and toluene.  相似文献   

20.
The removal of hydrogen sulfide and dust simultaneously by the DC corona discharge plasma with a wire-cylinder reactor was studied at atmospheric pressure and room temperature. The outlet gases were analyzed by Fourier Transform Infrared. Chemical compositions of the dust collected from ground electrode were analyzed by X-ray fluorescence. The results showed that the DC corona discharge is effective in removing H2S and dust simultaneously. The best H2S conversion was gained with the 2 cm discharge gap. The lower inlet H2S concentration, the higher conversion efficiency was gained at any specific input energy (SIE), while the energy yield was on the contrary. The removal efficiency of H2S decreased gradually as oxygen concentration increased, which means that the H2S decomposition mainly depends on direct electron collisions or short-living species, such as·O, ·OH radicals in the non-thermal plasma. At the initial stage, the conversion efficiency of H2S increased with the increasing of relative humidity, but later decreased while the relative humidity keep increasing with the same SIE. Existing of dust can not only reduce the energy consumption of H2S conversion and improve the removal efficiency, but also inhibit the yield of SO2 for it can further react with some compounds in the dust. With the discharge gap of 2 cm, inlet H2S concentration of 2400 ppm, O2 Of 0.5 %, relative humidity of 41 %, dust content of 4000 ± 5 % mg/m3 and SIE of 600 J/L, the H2S conversion reached 98.8 %, and the dust removal efficiency was close to 100 %.  相似文献   

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