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1.
齐震  孙也  樊星  朱天乐 《环境科学学报》2014,34(12):3133-3137
分别采用Na Cl O2和Na2SO3溶液作为氧化液和吸收液,在自行设计的鼓泡塔反应系统进行了液相氧化-吸收脱除模拟烟气NOx的研究,考察了气相SO2浓度、Na Cl O2和Na2SO3投加量以及p H值等因素对NO氧化和NOx脱除的影响.结果表明,SO2会优先于NO与氧化剂反应,从而增大氧化剂消耗量.偏酸性条件有利于NO氧化,但酸性太强会导致Na Cl O2分解为Cl O2逸出.碱性吸收液对NO几乎不具吸收脱除效果,但共存NO2能促进NO的吸收脱除.SO2对NO2吸收脱除具有促进作用.  相似文献   

2.
基于碳捕集的富氧燃煤烟气联合脱硫脱硝试验研究   总被引:1,自引:0,他引:1  
富氧燃煤烟气压缩液化CO2的高压低温工况为NO氧化为易溶于水的NO2提供了十分有利的条件.基于小型高压吸收试验装置,采用配制的富氧燃煤模拟烟气,在高压常温下进行了NO、SO2、O2与H2O的吸收反应试验.根据反应前后的气液产物分析,测定了不同组分比例与不同压力下混合气体中NO与SO2的转化率.NO氧化与吸收试验表明,NO转化为HNO3的比率随压力升高而增加,在0.5 ~2 MPa之间增加很快,在2 ~3 MPa之间增速趋丁平缓,压力达3 MPa以上时,90%以上的NO均转化为稀硝酸,且初始NO浓度越高,NO的转化率越大.混合气体中同时存在5O2与NO的联合吸收试验发现,只有少量的NO转化成了NO3-,SO2向H2SO4的转化率随压力升高而增加,初始SO2浓度越大,转化率越高.分析表明,SO2与NO同时存在时SO2先行转化为SO3,NO充当了催化剂,但SO2转化为SO3的一次转化率小于35%,反应酸液产物的多次循环能使SO2的转化率达到90%以上.建议的工艺流程中需采用两座吸收反应塔顺序脱除SO2与NO并回收稀酸溶液,有望在富氧燃煤发电捕集CO2系统中降低脱硫脱硝成本,部分地弥补富氧燃烧机组发电成本的增加.  相似文献   

3.
Wet scrubbing combined with ozone oxidation has become a promising technology for simultaneous removal of SO2 and NOx in exhaust gas. In this paper, a new 20-species, 76-step detailed kinetic mechanism was proposed between O3 and NOx. The concentration of N2O5 was measured using an in-situ IR spectrometer. The numerical evaluation results kept good pace with both the public experiment results and our experiment results. Key reaction parameters for the generation of NO2 and N2O5 during the NO ozonation process were investigated by a numerical simulation method. The effect of temperature on producing NO2 was found to be negligible. To produce NO2, the optimal residence time was 1.25 sec and the molar ratio of O3/NO about 1. For the generation of N2O5, the residence time should be about 8 sec while the temperature of the exhaust gas should be strictly controlled and the molar ratio of O3/NO about 1.75. This study provided detailed investigations on the reaction parameters of ozonation of NOx by a numerical simulation method, and the results obtained should be helpful for the design and optimization of ozone oxidation combined with the wet flue gas desulfurization methods (WFGD) method for the removal of NOx.  相似文献   

4.
A photochemistry coupled computational fluid dynamics (CFD) based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario (solar radiation affections in nighttime, daytime, and sun-rise/set), wind speed, building aspect ratio (building-height-to-street-width), and dispersion of reactive gases, specifically nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and O3. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of O3 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.  相似文献   

5.
Despite the heterogeneous reaction of sulfur dioxide (SO2) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO3) combined with NO2 and acetic acid to investigate their effects on the heterogeneous reaction of SO2 on CaCO3 particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO2 or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO2 and SO2 that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO2 that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO2 with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.  相似文献   

6.
Studies of fly-ash composition identified the presence of calcium and sulphur, indicating their potential role as sources of calcium sulphate. Residual acidity (particularly for oil fly ash) suggested the possibility of enhanced chemical reaction, and the presence of transition metals, probably as oxides, might accelerate the oxidation of SO2 to SO42−. Exposure tests in a laboratory-based rig simulating dry deposition on Portland and Monks Park limestone, either seeded or unseeded with fly-ash particulate material or transition metal oxide catalysts, were carried out using an SO2-containing environment at 95% r.h. Enhanced sulphation of these seeded limestones due to the above factors was minimal; at high loadings of fly ash, there was even evidence of masking the limestone surface, reducing sulphation. However, pure CaCO3 powder in the exposure rig showed increases in sulphation when seeded with metal oxide catalysts. Thus the limestones examined contained sufficient inherent catalysts for the oxidation of SO2 to SO42− to proceed at such a rate that external catalysts were superfluous. This implies that dissolution rate of SO2 in moisture films controls the availability of species for reaction with these carbonate-based stones and that fly ash deposited from the atmosphere does not enhance the reaction.  相似文献   

7.
Four different types of carbonaceous material (active carbon, graphitized carbon black, source samples from a power plant and from an urban heating boiler) were exposed to synthetic gas mixtures of SO2 and SO2 + NO2 in sub-ppm ranges at two different relative humidities (60 and 90% r.h.). The interaction of SO2 and NO2 with the carbonaceous materials led to sulfate and to three other products: NO, HONO and NO2. Formation of NO and NO2 was observed only on active carbon while the other three materials yielded HONO. It was also found that NO2 enhances the deposition of SO2 only on the source sample from the power plant at 60% r.h., whereas the material from the urban heating boiler had no effect both at low and high r.h. The results obtained show that no general statements on the effect of NO2 on the heterogeneous reaction of SO2 on these carbonaceous materials can be made and also that NO2 reactions in the presence of SO2 on carbon-containing surfaces should be considered as a source for the production of HONO in the urban environment.  相似文献   

8.
Two chamber-based methods for measurement of emission of NO from soil have been compared. One method measured NO by conversion to NO2 with a CrO3 converter and NO2 detection by luminol chemiluminescence. The other technique detects NO directly via NO/ozone chemiluminescence. The techniques were tested with a glass manifold system by addition of NO and other trace gases into a flowing zero air gas stream; water vapor was also added to the carrier gas in some cases. A second set of tests involved the simultaneous determination of NO concentrations from a chamber placed over the soil. Finally, flux measurements were made independently from common plots and from different plots within the same field. The luminol system was unaffected by the presence of ammonia, methylamine, acetonitrile and nitrous oxide, but had a lower response to NO in the presence of water vapor. The decrease was 7% at a relative humidity of 50%, and about 3% at a relative humidity of 23%. The NO/ozone chemiluminescence system was not influenced by any of the species doped into the gas stream. The simultaneous chamber data also showed a decreased response from the luminol system that was consistent with the humidity effect observed in the manifold tests. The average of independently measured flux values from common plots agreed reasonably well. However, the overall site mean flux determined by the luminol system was 74% of that of the NO/ozone system due to a larger data set from the luminol system. This comparison demonstrates that flux spatial heterogeneity can overwhelm analytical uncertainties, and that large sample sizes are needed to accurately characterize field fluxes.  相似文献   

9.
A novel ferruginous active absorbent, prepared by fly ash, industrial lime and the additive Fe(VI), was introduced for synchronous abatement of binary mixtures of SO2–NOx from simulated coal-fired flue gas. The synergistic action of various factors on the absorption of SO2 and NOx was investigated. The results show that a strong synergistic effect exists between Fe(VI) dose and reaction temperature for the desulfurization. It was observed that in the denitration process, the synergy of Fe(VI) dose and Ca/(S + N) had the most significant impact on the removal of NO, followed by the synergy of Fe(VI) and reaction temperature, and then the synergy of reaction temperature and flue gas humidity. A scanning electron microscope(SEM) and an accessory X-ray energy spectrometer(EDS)were used to observe the surface characteristics of the raw and spent absorbent as well as fly ash. A reaction mechanism was proposed based on chemical analysis of sulfur and nitrogen species concentrations in the spent absorbent. The Gibbs free energy, equilibrium constants and partial pressures of the SO2–NOx binary system were determined by thermodynamics.  相似文献   

10.
The reaction between NH3 and SO2 in thin water films was studied with a focus on the formation of sulfate. The reactions were conducted at 5 and 60% relative humidities or partial pressure of water vapor and at 0.04, 0.16 or 0.20 atm O2 for temperatures between 20 and 50°C using a flow reactor and static flask reactors. In the presence of water vapor, the oxidation of SO2 to sulfate was observed only when NH3 was present. The product was primarily (NH4)2SO4. Conversion of as much as 81% of the SO2 to sulfate was observed after 10 min of reaction when the initial concentrations of SO2 and NH3 were 1 ppm and the relative humidity was 60%. Conversion was only 1–3% when NH3 and/or water vapor were absent from the system. The surface of the reactor was found to influence the reaction by providing a place for a film of liquid water to form, and for the first several hours of reaction in the film, th e rate of sulfate formation was observed to be faster than oxidation in liquid water. In general, these results suggest that thin water films on environmental surfaces play a greater role in the deposition of atmospheric gases and the accumulation of their reaction products on surfaces than previously considered.  相似文献   

11.
A novel ferruginous active absorbent, prepared by fly ash, industrial lime and the additive Fe(VI), was introduced for synchronous abatement of binary mixtures of SO2–NOx from simulated coal-fired flue gas. The synergistic action of various factors on the absorption of SO2 and NOx was investigated. The results show that a strong synergistic effect exists between Fe(VI) dose and reaction temperature for the desulfurization. It was observed that in the denitration process, the synergy of Fe(VI) dose and Ca/(S + N) had the most significant impact on the removal of NO, followed by the synergy of Fe(VI) and reaction temperature, and then the synergy of reaction temperature and flue gas humidity. A scanning electron microscope (SEM) and an accessory X-ray energy spectrometer (EDS) were used to observe the surface characteristics of the raw and spent absorbent as well as fly ash. A reaction mechanism was proposed based on chemical analysis of sulfur and nitrogen species concentrations in the spent absorbent. The Gibbs free energy, equilibrium constants and partial pressures of the SO2–NOx binary system were determined by thermodynamics.  相似文献   

12.
Stone material from the corroding surface of buildings generally released nitric oxide with rates of 0.42–4.2 ng NON h−1 g−1 d.w. despite their large range of moisture, pH and content of ammonium, nitrite and nitrate. The net release rates of NO were independent of the NO mixing ratio of the atmosphere up to 1 ppmv NO. Whereas NO2 was taken up by all stones tested, uptake of NO was only observed in one out of five types of stone. NO release rates were highest at the stone surface and rapidly decreased in depth lower than 1 cm. NO release persisted for up to >3 months after the stone sample was removed from the building. NO was mainly produced during the biogenic oxidation of ammonium to nitrate at the stone surface which was probably due to endolithic nitrifying bacteria. Chemical decomposition of nitrite to NO and NO2 was only observed under acidic conditions.  相似文献   

13.
A parameterization scheme taking into account the episodical nature of rainout and incloud chemical transformation has been tested in a 2-D channel model. In the liquid phase many soluble gases are observed in concentrations never experienced in the gas phase. The effects on the trace gases SO2 and hydrogen peroxide, when they are modified by clouds and precipitation, are studied. When incloud interaction of SO2 and hydrogen peroxide is taken into consideration, calculated hydrogen peroxide profiles are brought closer to observed distributions. The effect of varying the time periods between cloud and rain events is tested. The impact on the formation and destruction of tropospheric ozone is also discussed.  相似文献   

14.
The iron and steel industry is not only an important foundation of the national economy, but also the largest source of industrial air pollution. Due to the current status of emissions in the iron and steel industry, ultra-low pollutant emission control technology has been researched and developed. Liquid-phase proportion control technology has been developed for magnesian fluxed pellets, and a blast furnace smelting demonstration project has been established to use a high proportion of fluxed pellets (80%) for the first time in China to realize source emission reduction of SO2 and NOx. Based on the characteristics of high NOx concentrations and the coexistence of multiple pollutants in coke oven flue gas, low-NOx combustion coupled with multi-pollutant cooperative control technology with activated carbon was developed to achieve efficient removal of multiple pollutants and resource utilization of sulfur. Based on the characteristics of co-existing multiple pollutants in pellet flue gas, selective non-catalytic reduction (SNCR) coupled with ozone oxidation and spray drying adsorption (SDA) was developed, which significantly reduces the operating cost of the system. In the light of the high humidity and high alkalinity in flue gas, filter materials with high humidity resistance and corrosion resistance were manufactured, and an integrated pre-charged bag dust collector device was developed, which realized ultra-low emission of fine particles and reduced filtration resistance and energy consumption in the system. Through source emission reduction, process control and end-treatment technologies, five demonstration projects were built, providing a full set of technical solutions for ultra-low emissions of dust, SO2, NOx, SO3, mercury and other pollutants, and offering technical support for the green development of the iron and steel industry.  相似文献   

15.
Oxidation-absorption technology is a key step for NOx removal from low-temperature gas. Under the condition of low O3 concentration (O3/NO molar ratio = 0.6), F-TiO2 (F-TiO2), which is cheap and environmentally friendly, has been prepared as ozonation catalysts for NO oxidation. Catalytic activity tests performed at 120°C showed that the NO oxidation efficiency of F-TiO2 samples was higher than that of TiO2 (about 43.7%), and the NO oxidation efficiency of F-TiO2-0.15 was the highest, which was 65.3%. Combined with physicochemical characteristics of catalysts and the analysis of active species, it was found that there was a synergistic effect between F sites and oxygen vacancies on F-TiO2, which could accelerate the transformation of monomolecular O3 into multi-molecule singlet oxygen (1O2), thus promoting the selective oxidation of NO to NO2. The oxidation reaction of NO on F-TiO2-0.15 follows the Eley-Rideal mechanism, that is, gaseous NO reacts with adsorbed O3 and finally form NO2.  相似文献   

16.
北京大气气溶胶部分无机组分及相关气体的浓度变化   总被引:20,自引:4,他引:16  
利用SJAC-MOBIC在2000-05~2000-09的3个采样时段测量了北京大气中的气溶胶SO42-、NO3-、NO2-、Cl-及相关气体组分,得出了这些污染组分的逐时变化.结果表明气溶胶Cl-、NO2-、NO3-及气体HCl、HNO2和HNO3有明显的变化规律,SO2和气溶胶SO42-的变化取决于SO2的排放,SO42-的峰值一般比SO2的峰值晚2h左右.  相似文献   

17.
The role of the gaseous pollutants, HCl and SO2, has been investigated in a laboratory-based atmospheric flow rig. Using an HCl level of 25 ppm at a pollutant bulk presentation rate 10 times that found typically outdoors, a degradation acceleration factor of about 20 times was obtained, together with realistic degradation products. HCl was found to be a more reactive gas than SO2, which was also studied at the 25 ppm level. This may be due either to factors involved in the adsorption of the gases on to the stone surfaces, or the extensive solubility of HCl, or the requirement of an extra step in the conversion of SO2 to sulphate, which would limit the overall reaction rate. The soluble degradation product CaCl2 is readily washed off the stone allowing continuous reaction, while the relatively insoluble CaSO4.2H2O can remain on, or in the stone surface regions and may inhibit or affect further reaction with SO2.The reaction of limestone with HCl gas is mass-transport limited and greater material losses arise in locations of higher HCl concentration and deposition velocity, i.e. a close-to-source effect is highlighted due to its high solubility and reactivity, but the HCl concentration is, of course, generally about one-fiftieth of that of SO2 outdoors. For SO2, with lower solubility and a necessary oxidation stage to form SO42−, comparatively high deposition velocities are applicable more widely from the source. The consequences include a widespread formation of relatively insoluble CaSO4.2H2O and consequent crust development.  相似文献   

18.
大气污染物垂直梯度自动监测系统的研制   总被引:1,自引:0,他引:1  
设计的大气污染物垂直梯度自动监测系统是用 2个电磁阀实现 3个高度的气体采样 ,依靠分析仪器自身的抽气泵将气体样品通过聚四氟乙烯管抽入各分析仪器进行测量 ,并用一台微机和一块 AD/DA转换板实施对电磁阀的控制和数据采集 .现场观测实验表明 ,对于 25m长的采样管清洗时间可设置 1 min,而采样管长度间的差异不会导致测量 O3、SO2、NO和 NO2 小时平均浓度存在显著性差异 .  相似文献   

19.
黄立维  松田仁树 《环境科学》2006,27(10):1941-1945
采用非热等离子体结合催化或现场化学吸收的2种方法来去除气流中的NOx.结果表明,非热等离子体结合催化,反应器内的CuO催化剂能有效地促进NO的还原反应;相对于催化还原NO而言,脉冲电晕作用下能有效地降低NO催化还原的反应温度.当催化剂为CuO,脉冲电压为18kV,反应温度为200℃,还原剂为1%CO及NO进口浓度为719 mg/m3条件下,NO的去除率达到了100%.非热等离子体结合现场化学吸收方法,是一种在常温下从气流中净化氮氧化物的有效方法,NO的去除率远远高于反应器内没有吸收剂的情况.可以认为反应器内的Ca(OH)2吸收剂通过与NO的氧化产物NO2或NO3的吸收反应促进了NO的去除.当反应器内有Ca(OH)2吸收剂存在时,在脉冲电压为18kV,O2浓度为2%及NO进口浓度为1 050 mg/m3条件下,NO的去除率达到了100%.  相似文献   

20.
臭氧降解水中苯并三唑反应动力学及效能研究   总被引:5,自引:2,他引:3  
陈忠林  蔡金玲  沈吉敏  董霖 《环境科学》2009,30(4):1044-1049
对臭氧氧化去除水中痕量苯并三唑(BTri)的反应动力学、效能及其影响因素进行了实验研究.结果表明,臭氧分子与BTri直接反应速率常数k3=20.18 L·(mol·s)-1,臭氧与BTri反应的表观反应速率常数KBTri随pH值的不同而有显著差异,当pH值由6.63增加到7.83时,表观反应速率常数由63.42 L·(mol·s)-1提高至582.69 L·(mol·s)-1,增加约8倍.单独臭氧化可以有效地去除水体中痕量BTri,最终去除率可达85%;随着水体pH值的增加及水体温度的升高,BTri的反应速率大幅度提高;自然水体中常见阴离子NO-3、SO2-4、Cl-对臭氧化去除BTri的去除率及反应速率无明显影响;羟基自由基(·OH)抑制剂叔丁醇对臭氧氧化去除BTri有一定的抑制作用,说明·OH也对臭氧氧化去除BTri有一定的贡献,表明臭氧化去除BTri的过程为O3直接氧化及·OH间接氧化共同作用的结果.  相似文献   

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