Simultaneous removal of SO2 and NO X with ammonia absorbent in a packed column

Catalytic oxidation of NO followed by simultaneous removal of SO₂ and NO _X with ammonia is a promising method for control of coal-fired flue gas pollutants. We investigated simultaneous absorption of SO₂ and NO _X in a packed column with ammonia, and found that SO₂ and NO _X could promote absorption with each other in the process of simultaneous removal SO₂ and NO _X . The removal efficiency of SO₂ and NO _X was, respectively, about 98% and 70.9% at pH 5.5, temperature 323.15 K, SO₂ concentration 1,800×10^?6, NO _X concentration 400×10^?6 and ${{m_{NO_2 } } \mathord{\left/ {\vphantom {{m_{NO_2 } } {m_{NO} }}} \right. \kern-0em} {m_{NO} }}$ in our experimental system. The experimental results also show that the formation of sulfite oxidized by reacting with dissolved NO₂ and the molar ratio of sulfite to total sulfur is more than 0.8 in the solution. Accordingly, the energy consumption for sulfite oxidation would be greatly reduced in the process of simultaneous desulfurization and denitrification with ammonia.     

Hydrophobic cotton fabric coated by a thin nanoparticulate plasma film

The audio frequency (AC) plasma of some kind of fluorocarbon chemical was applied to deposit a nanoparticulate hydrophobic film onto a cotton fabric surface. The measurement of the video contact angle showed that the superhydrophobicity of the cotton fabric was obtained with a treatment of only 30 s. The softness, water retention, moisture regain, color retention, abrasion, friction, and permeability were thoroughly investigated by a standard method that compared the fabric with a commercial Scotchgard‐protector‐sprayed cotton fabric. The results showed that the textile performances of the plasma‐coated fabric were superior to those of Scotchgard‐sprayed samples, except for the moisture regain, which was almost the same. A post‐treatment at a high temperature was conducive to increasing the hydrophobicity and the recovery of the water repellency of the plasma‐coated fabric after it was washed. Atomic force microscopy images and time‐of‐flight secondary‐ion mass spectra of plasma thin films on silicon wafers indicated that some physical and chemical changes took place during the post‐treatment process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1473–1481, 2003     

低温等离子体协同填料床吸附净化甲醇废水

采用低温等离子体协同填料床吸附强化氧化降解高浓度甲醇废水。研究表明单独采用4A分子筛、陶粒、陶瓷Rasching环和γ-Al₂O₃不同填料均可吸附废水中甲醇,但较易达到吸附饱和,其中4A分子筛的吸附速率和平衡吸附量优于其他3种填料。单独采用多针板式介质阻挡放电低温等离子体技术,化学需氧量（COD）降解率随放电时间和放电电压增加而增大。采用低温等离子体协同填料降解甲醇废水优于单一净化过程,协同初始阶段以吸附为主,随放电时间延长以等离子体降解反应为主,液相和填料吸附的甲醇同时被等离子体活性基团逐渐氧化降解,最大降解率达90%以上。单独填料吸附过程符合准二级吸附动力学方程。低温等离子体对COD降解反应级数随污染物浓度降低和反应时间延长逐渐增大。低温等离子体协同填料吸附对降解过程相互影响,等离子体活性基团对液相和固相吸附的污染物都有一定的活化作用。填料的吸附作用和等离子体氧化作用会不断改变液相中的污染物浓度与·OH浓度比值,降解过程宏观反应动力学级数随着液相中甲醇浓度降低而逐渐增大。     

SO2对钙基吸收剂吸收NO的作用机理

针对低温条件下SO2对Ca(OH)2吸收NO的影响进行了实验研究,分析了烟气中O2和H2O对SO2促进Ca(OH)2吸收NO的影响。实验结果表明,当烟气不含SO2时,Ca(OH)2对NO基本无吸收作用;烟气中SO2的存在对NO吸收具有促进作用。H2O和O2对SO2促进NO吸收有显著影响;当烟气不含O2时,即使大量的SO2被吸收,NO吸收效率仍较低;只有SO2与O2和H2O共存才能促进NO吸收。脱硫产物CaSO3对NO无氧化作用;NO、H2O和SO2未在吸收剂表面产生可分解释放NO2的大分子中间配合物。分析认为在脱硫过程中产生了可以促进NO与O2反应的非稳定中间活性组分。     

介质阻挡放电脱硫脱硝过程特性

氮氧化物和硫氧化物在介质阻挡放电(DBD)反应器中的脱除率与很多因素有关,如氧气含量、相对湿度和烟气中SO_2的初始浓度等。本文通过改变SO_2初始浓度、氧气含量和相对湿度来研究脱除氮氧化物和硫氧化物过程中的反应机理。结果发现,在N_2/SO_2/NO体系中SO_2初始浓度在较大范围内变化对NO和SO_2的脱除率影响很小;而N_2/NO/SO_2/H_2O体系中相对湿度的增加对SO_2的脱除的影响较NO的影响大,增加烟气中相对湿度能明显减少SO_2在烟气中的浓度;N_2/NO/SO_2/O_2体系中氧气的增加对SO_2的脱除效率影响不明显,但能促进NO氧化成NO_2或者其他的氮氧化物,同时,在一定的条件下,也能加速NO的生成。探讨NO和SO_2的反应机理,发现SO_2的反应主要与OH和水合电子有关,而NO的反应与O、N等活性基相关。     

Removal of NO and SO2 by pulsed corona discharge process

Overall examination was made on the removal of NO and SO₂, by pulsed corona discharge process. The mechanism for the removal of NO was found to largely depend on the gas composition. In the absence of oxygen, most of the NO removed was reduced to N₂; on the other hand, oxidation of NO to NO₂ was dominant in the presence of oxygen even when the content was low. Water vapor was an important ingredient for the oxidation of NO₂, to nitric acid rather than that of NO to NO₂. The removal of NO only slightly increased with the concentration of ammonia while the effect of ammonia on the removal of SO₂ was very significant. The energy density (power delivered/feed gas flow rate) can be a measure for the degree of removal of NO. Regardless of the applied voltage and the flow rate of the feed gas stream, the amount of NO removed was identical at the same energy density. The production of N₂O increased with the pulse repetition rate, and the presence of NH₃ and SO₂ enhanced it. Byproducts generated from propene used as additive were identified and analyzed. The main byproducts other than carbon oxides were found to be ethane and formaldehyde, but their concentrations were negligibly small.     

Simultaneous removal of SO2 and NO by sodium chlorite solution in wetted-wall column

The effect of feeding rate of NaClO₂ solution, inlet SO₂ and NO concentration, [NaClO₂]/[SO₂+NO] molar ratio (η), L/G ratio and, solution pH on the simultaneous removal of SO_x/NO_x has been investigated in a wetted-wall column. Both SO_x and NO_x removal efficiencies are enhanced with the increasing feeding rate of NaClO₂ solution and attain a steady state. NO_x removal efficiency increases with increasing SO₂ concentration, but SO_x removal remains unaffected with increasing NO concentration. In an acidic medium, DeSO_x and DeNO_x efficiency increased with increasing [NaClO₂]/[SO₂+NO_x] molar ratio and attained a steady state. NO_x removal starts only after the complete removal of SO_x. The excess of NaClO₂ does not enhance NO_x removal efficiency. Solution pH does not affect the DeSO_x and DeNO_x efficiency. The maximum SO_x and NO_x removal efficiencies achieved at the typical operating conditions of commercialized FGD processes are about 100 and 67%, respectively.     

Simultaneous removal of SO2, NO and particulate by pilot-scale scrubber system

SO _x and NO _x have both previously been identified as primary precursors of acid rain, and thus the abatement of SO _x and NO _x emissions constitutes a major target in the field of air pollution control. In this study, the efficacy of a pilot-scale scrubber was evaluated with regard to the simultaneous removal of SO₂, NO and particulate with wet catalysts. The removal efficiencies of particulate were measured to be 83, 92 and 97% with catalyst flux of 0.5, 0.8 and 1.5 L/min, respectively. The average removal efficiencies of particulate with different nozzles were approximately 94 and 90% with FF6.5 (5/8 in.) and 14 W (1.0 in.) nozzles, respectively. At least 96–98% of particulate and SO₂ were removed, regardless of the stage number of reactor. In a one-stage scrubber, 83.3% removal efficiency of NO was achieved after 48 hours; however, the two-stage scrubber achieved an NO removal efficiency of 95.7%. Regardless of the liquid-gas ratio, SO₂ and particulate were removed effectively, whereas NO was removed about 84% and 74% under liquid-gas ratio conditions of 39.32 L/m³ and 27.52 L/m³, respectively. In experiments using STS and P.P. pall ring as packing material, particulate and SO₂ removal efficiency values in excess of 98% were achieved; however, NO removal was correlated with the different packing materials tested in this study. With the above optimum operation conditions, even after 20 hours, the removal efficiency for NO stayed at 95% or higher, the removal efficiency for SO₂ stayed at 97% or higher, and the removal efficiency for particulate stayed at 92% or higher. In accordance, then, with the above results, it appears that this process might be utilized in scrubber systems, as well as systems designed to simultaneously remove particulate, SO₂ and NO from flue gas.     

NOx removal by non-thermal plasma at low temperatures with amino groups additives

NOx removal from flue gas using direct current (DC) narrow pulsed discharge-induced non-thermal plasma (NTP) was experimentally investigated. Factors such as additives, NOx initial concentrations, residence time, reaction temperatures inside the NTP reactor, and so on were investigated to evaluate their effects on NOx removal efficiencies. The focus was on the effects of additives containing amino groups. The results showed that H₂O addition enhanced NOx removal, NH₃ could further increase the NOx removal efficiencies under the same conditions without an obvious NH₃ slip, and N₂H₄ was the most effective additive by reducing NO _x to N₂. X-Ray diffraction (XRD) analysis of the products collected from the NTP reactor demonstrated that NOx removal inside the NTP reactor was mainly based on NOx oxidation when ammonia or H₂O was used as an additive, while NOx removal was mainly based on NOx reduction with the N₂H₄ additive.     

Preparation of TiO2 thin films on glass beads by a rotating plasma reactor

We experimentally coated the TiO₂ thin films on the glass beads by a rotating cylindrical plasma chemical vapor deposition (PCVD) process. The precursors for the thin films were generated by the plasma reactions, and they deposited on the glass beads to become the grains on the films. The TiO₂ thin films grow more quickly on the glass beads by increasing the reactor pressure, or the rotation speed of the reactor. As the applied power increases, the thickness of the thin films on the glass beads decreases. As the thickness of the TiO₂ thin films increases, the uniformity of the TiO₂ thin films decreases due to the deposition of larger grains or due to the increase of crack size. The rotating cylindrical PCVD process can be a good method to prepare the particles coated with metal or organic-doped thin films for highly functionalized materials.     

NTP转化C3H6/NO/N2气氛中NO及发射光谱分析

利用介质阻挡放电产生低温等离子体转化C₃H₆/NO/N₂气氛中NO,结合发射光谱诊断法研究了碳氢化合物C₃H₆对NO转化的影响。研究结果表明,随着放电功率的升高,NO转化率先升高后逐渐趋于平缓,NO₂浓度持续降低,N₂O浓度呈先升高后降低趋势,NO主要被还原为N₂;相同放电功率下,随着C₃H₆初始浓度升高,NO_x转化率和N₂O浓度升高、NO₂浓度降低;添加C₃H₆会降低N₂第二正带系和NO-γ带的发射光谱强度,产生CN自由基的激发跃迁谱线,影响NO的化学反应机制,同时生成了棕黄色的聚合物。     

Enhancement mechanism of SO2 removal with calcium hydroxide in the presence of NO2

The enhancement mechanism of SO₂ removal by the presence of NO₂ under low temperature and humid conditions was studied in a fixed bed reactor system. The presence of NO₂ in the flue gas can enhance SO₂ removal. The interaction between SO₂ and NO₂ in gas phase could not explain the effect of NO₂ on SO₂ removal under low-temperature and humid conditions. When Ca(NO₃)₂ and Ca(NO₂)2 as additive were added on the surface of sorbent, the desulfurization activity of sorbent decreased. However, the sorbent pretreated by NO₂ for a moment has higher SO₂ removal. The oxidization of SO₃²⁻ to SO₄²⁻ and the evolution of sorbent surface structure in the presence of NO₂ can explain the enhancement of SO₂ removal by the presence of NO₂. HSO₃⁻ and SO₃⁻ reacted with NO₂ to form sulfate, which can accelerate the hydrolysis of SO₂. The reaction between NO₂ and Ca(OH)₂ can make the unreacted sorbet under the SO₂ removal product exposed to the reactant gas.     

活性焦联合脱硫脱硝工艺试验研究

为了开发活性焦联合脱硫脱硝工艺,选取一种商用活性焦在微型反应器上进行NH3对NO、SO2脱除影响及NO和SO2脱除交互影响试验,提出了活性焦联合脱硫脱硝工艺路线,并在实验室搭建的模拟装置上进行了工艺路线的模拟试验验证。结果表明,活性焦脱硝是低温SCR反应,NH3的存在使SO2吸附量提高约18%,说明NH3与SO2发生化学反应,有利于SO2脱除,但生成的硫铵会降低工业装置的稳定性;当活性焦无吸附NH3时,NO对SO2脱除无影响,当活性焦吸附NH3时,通入NO前后,SO2出口体积分数由0.15%降至0.13%左右,说明NO对SO2脱除有促进作用;通入SO2气体后,NO出口体积分数由0.045%迅速增至0.065%,说明SO2与NO争抢NH3,不利于脱硝。通过工艺路线模拟试验发现,当联合脱硫脱硝空速为400 h-1时,脱硫效率≥95%,脱硝效率≥70%,验证了活性焦联合脱硫脱硝工艺的可行性。     

Hydrophobic hybrid inorganic-organic thin film prepared by sol-gel process for glass protection and strengthening applications

Hybrid systems based on 3-trimethoxysilyl propyl methacrylate, tetramethylorthosilicate, and methyl methacrylate were developed for moisture protection and strengthening of glass objects. The hydrophobic behavior of the hybrid was obtained by adding different fluorinated precursors to the hybrid solution. Experimental results show that among different fluorinated percursors, 1H,1H,2H,2H-perfluorooctyl trichlorosilane gives the best results, increasing the water contact angle up to 100° and decreasing the free surface energy. Coated glasses exhibit higher strength (more than 50%) than uncoated glasses. The strengthening was interpreted in terms of a healing mechanism. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2387–2393, 1997     

Mn/Cu-BTC催化剂同时脱硫脱硝实验研究

通过水热合成法制得金属有机骨架材料Cu-BTC,采用浸渍法将金属氧化物（Fe、Mn、Ce、Co、Mo）负载在Cu-BTC上得到复合催化剂（X/Cu-BTC）并用于同时脱除模拟烟气中的SO₂和NO。采用N₂物理吸附（BET）、X射线衍射分析（XRD）、热重分析（TG）以及扫描电镜（SEM）等方法对催化剂进行表征。表征结果显示MnO_x的负载使得催化剂的比表面积、孔体积下降,负载前后催化剂的结构保持不变。同时考察了不同金属氧化物负载Cu-BTC同时脱硫脱硝的效果：Mn/Cu-BTC的脱硝最佳,其次为Ce/Cu-BTC。最后对MnO_x与CeO_x的负载量进行了考察,10% Mn/Cu-BTC与10% Ce/Cu-BTC为最佳负载量。在250℃,空速为10000h^-1时,10% Mn/Cu-BTC的脱硫和脱硝效率分别为100%和88%,10% Ce/Cu-BTC的脱硫和脱硝效率分别为100%和75%,表明Mn/Cu-BTC催化剂对于SO₂和NO具有良好的同时脱除效果。     

Long-term stability of a horizontally-aligned carbon nanotube field emission cathode coated with a metallic glass thin film

A horizontally-aligned carbon nanotube (HACNT) field emission cathode was coated with a metallic glass thin film (MGTF) to improve the stability of the field emission properties. HACNT field emission cathodes have previously been fabricated on glass substrates using composite plating and crack-formation techniques. A carbon nanotubes/nickel (CNTs/Ni) composite film is deposited onto a glass substrate at 80 °C by the composite plating technique alone. Cracks are then formed in the CNT/Ni composite film during 30 min heating at 300 °C, and HACNTs are exposed in the cracks. The field emission properties of the HACNT field emission cathode show a low turn-on electric field E_on of about 2.3 V/μm, a low threshold electric field E_th of about 4.7 V/μm at an emission current density of 1 mA/cm², and a stability time of 78 h. The degradation of the HACNT field emission cathode is prevented by using a MGTF-coating technique and superior long-term stability (i.e. >125 h, with 5 nm MGTF; >270 h, with 10 nm MGTF) for the MGTF/HACNT field emission cathode is achieved.     

非热等离子体烟气脱硝中的二氧化硫、氨和温度的效应

非热等离子体烟气脱硝的主要问题是能耗偏高,然而适当设置烟气的条件参数,有可能尽量地降低能耗.其中烟气所含SO₂和外加NH₃产生的降低能耗或提高脱硝率的效果被广泛关注.本文采用CSTR模型,对非热等离子体烟气脱硝的化学反应过程进行数学模拟.从原理上证实了SO₂和外加NH₃产生的增效不是SO₂的贡献,而是外加NH₃的效果,同时,讨论了温度的效应.本研究为燃煤电厂烟气净化流程中的非热等离子体脱硝段的设置及调质剂的使用提供理论参考.     

填料塔同时吸收高浓度SO2和NO2生成亚硝酰硫酸的研究

为了解决染料行业生产过程中磺化和硝化产生的高浓度硫氧化物(主要为SO2)和氮氧化物(主要为NO2)废气所造成的大气污染,采用填料塔反应器同时吸收SO2和NO2,并生成亚硝酰硫酸的工艺,并对优化的工艺条件进行深入的分析.主要考察了吸收液的构成(浓硫酸和浓硝酸)与浓度、气体流速、污染物浓度和吸收时间等参数对吸收效率和体积传...     

Synthesis of AlN nanopowder coated with a thin layer of C,using a thermal plasma reactor

High-purity nanocrystalline aluminum nitride powders were synthesized by using a 12?kW non-transferred arc plasma. The synthesis was conducted in a versatile, new designed, one-chamber thermal plasma reactor (TPR). The novel experimental assembly incorporated better working conditions like: high temperature gradient between the crucible and reactor's wall, and high super-saturation of the system by nitrogen and carbon. Thermodynamic modelling of the synthesis was conducted in order to achieve the best conditions for AlN formation. In this study, aluminum discs of Al 1100 were used as precursor material and pure nitrogen was the only gas used as reagent and plasmogenic gas.Nanopowders collected from reactor's wall were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-Ray diffraction (XRD). Synthesized h-AlN nano-powders were found to be free of oxides and aluminum metal. A thin carbon-layer around the particles was detected. TEM results indicated that the carbon-layer was around 5 and 10?nm. This outcome could make a significant difference with other synthesis reported in the literature since the occurrence of the carbon-layer, could delay AlN oxidation, prevent hydration, and could avoid the agglomeration of the particles.