Plasma Jet and Dielectric Barrier Discharge Treatment of Wheat Seeds

Plasma Chemistry and Plasma Processing - Low-temperature plasma treatment of wheat seeds was performed by a plasma jet and dielectric barrier discharge, both at atmospheric pressure. The influence...     

介质阻挡放电等离子体甲烷部分氧化重整制氢

在自制的介质阻挡放电等离子体重整制氢装置上进行了甲烷部分氧化重整制氢的实验研究. 本文研究了氧碳(O/C)摩尔比, 进气流量, 放电间隙, 放电区间长度, 填充物的直径、形状和材料, 放电电压和放电频率对甲烷转化率、氢产率和产物的选择性(H₂、CO和CO₂)的影响. 实验结果表明: 放电区域的参数对甲烷转化率有较大的影响. 甲烷转化率随着放电区域长度的增大而增大, 当放电区域长度从5 cm增大到20 cm时, 甲烷转化率从6.87%增大到22.26%, 增大率为224%. 同时, 放电区域的填充物对产氢效果有较大的影响. 当反应器填充颗粒时, 甲烷转化率比无填充物时高. 选择适当介电常数的填充物具有巨大的实际工程意义. 另外, 氢产率和氢气的选择性随着放电频率的增大而增大, 当放电频率从1.5 kHz 增大到7.0 kHz 时, 氢产率从1.10%增大到9.49%, 氢气的选择性从21.18%增大到30.06%. 实验结果将对碳氢燃料等离子体重整制氢的车载应用提供实验依据.     

Flue Gas Desulfurization by Dielectric Barrier Discharge

There are many problems with flue gas desulfurization by traditional gas ionization discharge, including the large size of the plasma source, high energy consumption, and the need for a traditional desulfurization method. This paper introduces oxidization of SO₂ to sulfuric acid (H₂SO₄) in a duct by reactive oxygen species (O₂ ⁺, O₃) produced by strong ionization dielectric barrier discharge. The entire plasma reaction process is completed within the duct without the use of absorbents, catalysts, or large plasma source. The reactive oxygen species O₂ ⁺ reacts with gaseous H₂O in the flue gas to generate ·OH radicals, which can oxidize trace amounts of SO₂ in large volumes of the flue gas to produce H₂SO₄. Sulfuric acid is also produced by O₃ oxidation of SO₂ to SO₃, and SO₃ reacting with gaseous H₂O in the flue gas. Experimental results showed that with a gas temperature of 22 °C and reactive oxygen species injection rate of 0.84 mg/L, the SO₂ removal rate was 81.4 %, and the SO₄ ^2? concentration in the recovered liquid H₂SO₄ reached 53.8 g/L.     

TiOx Films Deposited by Plasma Enhanced Chemical Vapour Deposition Method in Atmospheric Dielectric Barrier Discharge Plasma

The plasma enhanced chemical vapour deposition method applying atmospheric dielectric barrier discharge (ADBD) plasma was used for TiO_x thin films deposition employing titanium (IV) isopropoxide and oxygen as reactants, and argon as a working gas. ADBD was operated in the filamentary mode. The films were deposited on glass. The films?? chemical composition, surface topography, wettability and aging were analysed, particularly the dependence between precursor and reactant concentration in the discharge atmosphere and its impact on TiO_x films properties. Titanium in films near the surface area was oxidized, the dominating species being TiO₂ and substoichiometric titanium oxides. The films exhibited contamination with carbon, as a result of atmospheric oxygen and carbon dioxide reactions with radicals in films. No relevant difference of the film surface due to oxygen concentration inside the reactor was determined. The films were hydrophilic immediately after deposition, afterwards their wettability diminished, due to chemical reactions of the film surface and chemical groups involved in the atmosphere.     

Plasma Reactivity and Plasma-Surface Interactions During Treatment of Toluene by a Dielectric Barrier Discharge

Toluene removal is investigated in filamentary plasmas produced in N₂ and in N₂/O₂ mixtures by a pulse high voltage energised DBD. Influence of the oxygen percentage (lower than 10%) and of the temperature (lower than 350°C) is examined. Toluene is removed in N₂ through collisions with electrons and nitrogen excited states. The removal efficiency is a few higher in N₂/O₂. It increases when the temperature increases for N₂ and N₂/O₂. Both H- and O-atoms play an important role in toluene removal because H can readily recombine with O to form OH, which is much more reactive with toluene than O. H follows from dissociation of toluene and of hydrogenated by-products by electron collisions. Detection of cyanhidric acid, acetylene, formaldehyde, and methyl nitrate strengthens that dissociation processes, to produce H and CH₃, must be taken into account in kinetic analysis. Formation and treatment of deposits are also analysed.     

Plasma-Aided Cotton Bioscouring: Dielectric Barrier Discharge Versus Low-Pressure Oxygen Plasma

The hydrophobic cuticle of the cotton fiber has formed a natural barrier for pectinase to catalyze its substrates (pectins beneath the cuticle), thus resulting in an insufficient scouring for cotton. Two plasma-based treatments, dielectric barrier discharge (DBD) at atmospheric pressure and cold oxygen plasma at low pressure in a vacuum system, were used as the pretreatments prior to cotton bioscouring, aiming at increasing the accessibility of pectinases to the pectic substances on the cotton fiber. The effects of different processing parameters of DBD and oxygen plasmas on the wettability, whiteness and burst strength of pectinase-scoured cotton were determined and compared. Although both of the pretreatments could enhance cotton bioscouring, DBD might be more suitable for current bioscouring due to its continuous processing mode and lower requirements to the equipment.     

甲烷参与下催化剂填充型介质阻挡放电等离子体脱除NOx

 将In/HZSM-5催化剂填充于介质阻挡放电反应器中,考察了甲烷参与下NOx的脱除及其脱除产物. 结果表明,在200～350 ℃间,等离子体与催化剂共同作用时NOx的转化率明显高于等离子体或催化剂单独作用时NOx的转化率. 在0.03%NO-0.05%CH4-2%O2-97.92%N2,空速7200 h-1和300 ℃的条件下,单纯等离子体、单纯催化剂和二者共同作用下NOx的转化率分别为24%,25%和65%. 甲烷参与下等离子体和催化剂共同作用时,在催化剂表面没有硝酸盐或亚硝酸盐生成,仅有少量副产物N2O生成. 由此可以推断,NOx脱除的主要产物为N2. 低于300 ℃时,NOx的脱除以分解途径为主,甲烷的作用主要是抑制放电条件下NOx生成的副反应; 在300～350 ℃间,甲烷作为还原剂被等离子体和催化剂协同活化,NOx的脱除以还原途径为主. 采用催化剂填充型介质阻挡放电反应器,可在非常宽的温度区间实现NOx的脱除.     

A Dielectric Barrier Discharge Plasma Degrades Proteins to Peptides by Cleaving the Peptide Bond

Plasma Chemistry and Plasma Processing - Effects of atmospheric pressure plasmas on proteins are studied to assess the quality of plasma decontamination and to gain insights into plasma-triggered...     

Fuel Oil Pyrolysis Initiated by Propane-Butane-Oxygen Flame

The parameters of fuel oil pyrolysis initiated by propane-butane-oxygen flame were studied as influenced by the temperature in the pyrolysis zone, time of the fuel oil contact with the initiating flame, and fuel oil feed rate. The experimental data on thermal and flame-initiated fuel oil pyrolysis were compared.     

Oxidative Conversion of PFC via Plasma Processing with Dielectric Barrier Discharges

Perfluorocompounds (PFCs) have been extensively used as plasma etching andchemical vapor deposition (CVD) gases for semiconductor manufacturingprocesses. PFCs have significant effects on the global warming and havevery long atmospheric lifetimes. Laboratory-scale experiments were performedto evaluate the effectiveness of CF4 conversion by using dielectric barrierdischarges (DBD). The results of this study revealed that the removalefficiency of CF₄ increased with application of higher voltage, gas residence time, oxygen content, and frequency. Combined plasma catalysis(CPC) is an innovative way for abatement of PFC and experimental results indicated that combining plasma with catalysts could effectively remove CF4. Products were analyzed by Fourier transform–infrared spectroscopy (FT–IR) and the major products of the CF4 processing with DBD were CO2, COF2, and CO, when O was included in the discharge process. Preliminary results indicated that as high as 65.9% of CF4 was decomposed with CPC operated at 15 kV, 240 Hz for the gas stream containing 300 ppmv CF₄,20% by volume O₂, and 40% by volume Ar, with N₂ as thecarrier gas.     

Photochemical Removal of Gaseous Elemental Mercury in a Dielectric Barrier Discharge Plasma Reactor

The plasma process has the potential to serve as a low cost mercury oxidation technology that will facilitate elemental mercury removal in a downstream of Flue Gas Desulfurization system. The performance of the main gas constituents, such as H₂O, O₂ and HCl on elemental mercury oxidation under plasma atmosphere was investigated in simulated flue gas. Experiments were carried out in a dielectric barrier discharge reactor operated at 140?°C. Photochemical effects of nanocrystalline titania on oxidation of elemental mercury were also tested. The results indicated that both H₂O and O₂ promote the oxidation of elemental mercury significantly. Active radicals generated by ionization, such as O, O₂ and OH, play the crucial roles in oxidation process. The presence of HCl in N2/O2 stream in plasma system is a very effective way of oxidizing elemental mercury, the nearly complete oxidation of elemental mercury was observed by 4?kV of applied voltage only. The best photocatalytic activity of anatase TiO₂ which was calcined at 600?°C was found in our tests. Compared with the plasma process alone, the oxidation efficiency increased 18.7?C26.3?% with the addition of photocatalyst.     

Dielectric Barrier Discharge for Ammonia Production

The leading after-treatment technology for NOx removal process in Diesel engines for stationary and mobile applications is the selective catalytic reduction of oxides of nitrogen [NOx] by ammonia [NH₃]. A novel non-thermal plasma electrode with a needle array in a dielectric barrier discharge reactor, powered by a high frequency neon transformer, is used for the thermal decomposition of solid urea [(NH₂)CO(NH₂)] to produce ammonia. The thermolysis of urea produces iso-cyanic acid [HNCO] as a byproduct, besides ammonia, which can react with water in the gas phase, thus giving carbon dioxide and more ammonia. The presence of water fed before and/or after the plasma reactor was studied to assess its effect on the amount of produced ammonia. Results clearly showed that water fed to the entrance of the reactor can efficiently promote the reaction of iso-cyanic acid to produce ammonia and this result can be improved when air is used as carrier gas for 115 V of input voltage to a neon transformer and with a gas flow rate of 4 L/min.     

Measurement of Ozone Production in Non-thermal Plasma Actuator Using Surface Dielectric Barrier Discharge

Plasma actuators for flow control are intensively studied, but the production of ozone by the surface dielectric barrier discharge used in the actuators has never been quantified. Since ozone is harmful to human health, it is important to quantify its production for an application of this type of actuator on a land vehicle. This paper describes an experimental study to measure the concentration of ozone produced by an actuator with different parameters: amplitude and frequency of the applied high voltage, and the electrode configuration (shape, spacing and length). The results show that, under our experimental conditions, the production of ozone is directly proportional to the power dissipation. The production rate was measured at 21 g/kWh. Although the rate is much lower than that of an industrial ozonizer, it is still far from being negligible and should be taken into account for the future application of these actuators.     

Oxidation of Elemental Mercury by Active Species Generated From a Surface Dielectric Barrier Discharge Plasma Reactor

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.     

Study of SO2 Removal Using Non-thermal Plasma Induced by Dielectric Barrier Discharge (DBD)

Dielectric Barrier Discharge (DBD) non-thermal plasma reactors built with three different dielectric materials for SO₂ removal were studied. The discharge characteristics of the three dielectrics, namely glass, Teflon, and glass fiber-based epoxy resin, were analyzed using Lissajous figures. From the Lissajous figures, the transition charge and energy deposition for each dielectric material were determined. When both the discharge characteristics and mechanical processability were considered, glass fiber-based epoxy resin was regarded as the best dielectric barrier among the three for DBD plasma reactors. A multi-cell DBD reactor built with glass fiber-based epoxy resin was used for treating air stream containing SO₂. SO₂ % removal decreased with increasing initial SO₂ concentration in a biphasic fashion. SO₂ removal was greatly improved by adding NH₃ into the air stream. Raising the relative humidity of the air stream also helped SO₂ removal. A SEM (scanning electron microscope) test illustrated some changes in surface morphology of Teflon and glass fiber-based epoxy resin.     

电子能量对沿面介质阻挡放电等离子体化学产物的影响

基于光电倍增管研制了一套无触发信号的双通道光学探测系统, 并组装了测试样机, 实现了对沿面介质阻挡放电(SDBD)等离子体约化电场的测量, 进而通过BOLSIG+软件获得了电子能量. 采用原位紫外吸收光谱和傅里叶变换红外光谱, 研究了SDBD等离子体在不同电压和频率下的化学产物的浓度变化, 并结合空气等离子体化学反应揭示了产物相互作用的微观机理. 结果表明, 电子能量能够改变电子碰撞反应的速率系数, 调控化学反应的源头活性粒子的浓度, 进而影响到化学产物的生成和猝灭.     

高频介质阻挡放电烟气脱硫研究

采用高频介质阻挡放电的方式产生低温等离子体,研究在不加入NH₃的情况下流动态SO₂的去除情况.实验表明,在输入电压为12 kV,SO₂浓度为5400 mg/m³,气体流量为0.36 m³/h,相对湿度为55%时,脱硫率可达到70%以上;水气的存在对SO₂的去除有较大的促进作用,升高电压和增加O₂量对脱硫率的促进作用有限.对实验结果进行了解释,并提出了反应机理.     

Air Atmospheric Dielectric Barrier Discharge Plasma Induced Germination and Growth Enhancement of Wheat Seed

Air atmospheric dielectric barrier discharge plasma (DBD) was attempted to pretreat wheat seed to improve its germination and growth in this study. The effects of the DBD plasma treatment on the wheat seed germination, seedling growth, osmotic-adjustment products, lipid peroxidation level, and antioxidant enzymes activity were investigated. The experimental results showed that the DBD plasma treatment with an appropriate time scale could promote the wheat seed germination and seedling growth. The germination potential, germination rate, germination index, and vigor index increased by 26.7, 9.1, 16.9, and 46.9% after 7 min’s DBD plasma treatment, respectively; the root length, shoot length, fresh weight, and dry weight of the seedlings also increased after the DBD plasma treatment. The osmotic-adjustment products, proline and soluble sugar contents, in the wheat seedlings were significantly enhanced after the DBD plasma treatment with an appropriate time scale, while the malondialdehyde content decreased. Moreover, the activities of superoxide dismutase and peroxidase also increased after the DBD plasma treatment. The DBD plasma treatment led to etching effect on the wheat seed coat, resulting in the improvement of its water absorption capacity.     

Deposition of Gold Nanoparticles on Polypropylene Nonwoven Pretreated by Dielectric Barrier Discharge and Diffuse Coplanar Surface Barrier Discharge

The aim of this study was to examine and compare the potentials of two different ambient air plasma treatments: volume dielectric barrier discharge and diffuse coplanar surface barrier discharge, for the activation of polypropylene (PP) nonwovens surface. This was done in order to enhance the deposition of gold nanoparticles (AuNPs) onto PP surface. AuNPs were attached onto PP surface from colloidal solution prepared without stabilizers. Scanning electron microscopy, atomic force microscopy, attenuated total reflection-Fourier transform infrared spectroscopy, water absorption, and AuNPs uptake were used to assess the surface changes due to the plasma treatment, and to evaluate the durability of the achieved treatment effects. Finally, as a very important aspiration of the research, antibacterial activity of AuNPs loaded PP nonwovens against pathogens Staphylococcus aureus and Escherichia coli was evaluated in vitro. The plasma modified PP nonwovens have highly improved wetting and sorption properties. The PP nonwovens loaded with 17–62 mg/kg AuNPs exhibit antibacterial activity against tested pathogens. Surprisingly, this activity was enhanced by the first sample rinsing.     

Plasma Polymerization in a Nitrogen/Ethanol Dielectric Barrier Discharge: A Parameter Study

Plasma Chemistry and Plasma Processing - Plasma polymerization experiments are typically conducted by sustaining a non-thermal plasma in a gas flow containing monomer molecules. Recently, it was...