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.     

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.     

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.     

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.     

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.     

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     

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.     

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...     

Reaction of SO2 and NO2 with polymers

A number of polymers have been exposed to SO₂ and NO₂ gas under various conditions. Chain scission, crosslinking reactions, and changes in infrared spectra have been noted. All polymers suffer some deterioration, which may be considerable with exposure over long periods of time. Elastomers form a separate group, being appreciably more susceptible to these gases than saturated polymers; however, they are still more sensitive to ozone.     

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.     

Removal of Hg0 from containing‐SO2/NO flue gas by ultraviolet/H2O2 process in a novel photochemical reactor

A novel photochemical spray reactor is first developed and is used to remove Hg⁰ and simultaneously remove Hg⁰/SO₂/NO from flue gas by ultraviolet (UV)/H₂O₂ process. The effects of several parameters (UV wavelength, UV power, H₂O₂ concentration, Hg⁰ inlet concentration, solution temperature, liquid–gas ratio, solution pH, SO₂ concentration, NO concentration, and O₂ concentration) on removal of Hg⁰ by UV/H₂O₂ process were investigated. Removal mechanism of Hg⁰ is proposed and simultaneous removal of Hg⁰, NO, and SO₂ is also studied. The results show that the parameters, UV wavelength, UV power, H₂O₂ concentration, liquid–gas ratio, solution pH, and O₂ concentration, have significant impact on removal of Hg⁰. However, the parameters, Hg⁰ inlet concentration, solution temperature, SO₂ concentration, and NO concentration, only have small effect on removal of Hg⁰. Hg²⁺ is the final product of Hg⁰ removal, and Hg⁰ is mainly removed by oxidations of H₂O₂, ·OH, · O, O₃, and photoexcitation of UV. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2275–2285, 2014     

Engineered TiO2 and SiO2‐TiO2 films on silica‐coated glass for increased thin film durability under abrasive conditions

Thin films durability is critical to retain its performance in real life applications. For automotive glass, further factors such as haze appearance developed under abrasive conditions become relevant to ensure the driver's visibility. Macroscopic abrasion resistance tests of TiO₂/SiO₂ and SiO₂–TiO₂/SiO₂ thin films on soda‐lime silica (SLS) glass were performed according to an American standard for safety grazing. The purpose of this, was to increase the top active film durability in a bilayer system by understanding how film thickness and top film composition influence abrasion performance. In order to achieve this understanding, three approaches were considered: (a) determination of the influence of TiO₂ top film thickness, (b) replacement of the TiO₂ top film by SiO₂–TiO₂ films, and (c) determination of the influence of SiO₂–TiO₂ film thickness. Results showed that thinner top TiO₂ film thickness leads to SiO₂/TiO₂ bilayers with lower haze value and improved abrasion resistance. It was also found that SiO₂ addition to TiO₂ top film composition promotes the thin film adhesion and sample durability against abrasive wear. Friction coefficient and micro‐hardness measurements support the abrasion results. Factors contributing to the improvement of the lifetime performance of TiO₂ and SiO₂–TiO₂ thin films were identified.     

Novel method for removal of NO x and SO2 by sustainable electrochemical process using Ag(I)/Ag(II) redox mediator

The objective of this work was to develop a process for removal of industrial waste gases like NO, NO₂ and SO₂ by electrochemically generated Ag(I)/Ag(II) redox mediator system in aqueous nitric acid medium. 100% removal efficiencies were achieved in these studies for removal of NO _x and SO₂ with Ag(II) ions in room temperature and atmospheric pressure. This Ag(I)/Ag(II) redox mediator system can be regenerated continuously during the scrubbing process.     

Simultaneous removal of SO2 and NO by low cost sorbent-catalysts prepared by lime, fly ash and industrial waste materials

The potential of the sorbent-catalysts prepared from three low cost materials, i.e., the lime, fly ash and some industrial waste material containing iron oxide, have been investigated for simultaneous removal of SO₂ and NO _x from flue gas in the temperature range 700–850 °C. NH₃ was chosen as the reducing agent for NO reduction in this study. Experimental results showed that SO₂ and NO could be simultaneously removed efficiently in the absence of O₂ at the temperature window of 700–800 °C. The effect of product layer generated from SO₂ removal on NO removal was not obvious. NO removal efficiency was strongly inhibited by O₂, which was attributed to the partial oxidation of NH₃ to NO over the sorbent-catalysts in the presence of oxygen. Neither NO₂ nor N₂O by-product was detected both in the absence and presence of O₂. Three routes were suggested to overcome the negative effect of O₂. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

SO2-Assisted Simultaneous Reduction of SO2 and NO by CO on SnO2-TiO2 Solid Solution

Sn_0.5Ti_0.5O₂ shows excellent catalytic performance both for the CO-SO₂ reaction and the CO-SO₂-NO reaction. At 350 ° C, 525 ppm SO₂/520 ppm NO/2085 ppm CO, SV = 3000 h^-1, the conversion of SO₂ is nearly complete in the CO-SO₂ reaction and above 89% in the CO-SO₂-NO reaction; NO conversion is above 98% in the latter reaction. The selectivities of S and N₂ are both close to 100%. SO₂ shows a significant promoting effect on the activity of the Sn_0.5Ti_0.5O₂ catalyst for NO reduction by CO. Combining transient response experiments, catalytic tests and TPD results, we propose a SO₂-assisted NO-CO reaction concept. The existence of a surface sulfur species, which was formed during the CO-SO₂ or CO-SO₂-NO reaction, is proved by XPS analysis. It is the active site for NO reduction in the CO-SO₂-NO reaction, and through which SO₂ accomplishes its promoter role. On the basis of the results obtained, the SO₂-assisted redox mechanism of simultaneous reduction of SO₂ and NO by CO is proposed.     

Simultaneous removal of NO and SO2 using aqueous peroxymonosulfate with coactivation of Cu2+/Fe3+ and high temperature

A novel process on simultaneous removal of NO and SO₂ using aqueous peroxymonosulfate (PMS) with synergic activation of Cu²⁺/Fe³⁺ and high temperature in an impinging stream reactor is developed for the first time. Effects of PMS concentration, Cu²⁺/Fe³⁺ concentration, reaction temperature, solution pH, flue gas flow, liquid–gas ratio, gas components, and inorganic ions on NO/SO₂ removals were investigated. Active species and products were determined by electron spin resonance spectroscopy and ion chromatography. Removal pathways of NO/SO₂ were revealed, and mass transfer‐reaction kinetics of NO removal was studied. The optimal experimental conditions are obtained. H₂SO₄ and HNO₃ are the main products. It is found that there is a clear synergy between Cu²⁺/Fe³⁺ and high temperature for activating PMS. and ·OH are found to be the main oxidants for NO removal. NO removals belong to pseudo‐first fast reactions in the two investigated oxidation systems. Besides, the kinetic parameters are also measured. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1287–1302, 2017     

Microwave effect in removal process of NO by electron beam irradiation and quantitative prediction of the removed NO

A flow process with electron beam (EB) irradiation carried out the removal of NO in air by adding microwave (MW) to improve the removal efficiency of NO. The EB irradiation combined with MW irradiation was very effective in the range of NO removal efficiency of 70–80% and reduced required doses up to more than 30%, compared to the flow process without MW. On the other hand, MW irradiation was unlikely to affect the NO removal above 90% of removal efficiency. In addition, MW effect appeared definitely in the dose ranges of 8–24 kGy, whereas the effect became minor below 8 kGy and above 24 kGy. This study found that MW irradiation can play an auxiliary role in NO removal with EB irradiation and the effect of MW on the NO removal is based on an intrinsic kinetic to the exclusion of a thermal effect. The concentrations of removed NO could be linearly correlated as ΔC=k[NO] _o +k _o . Where, k was proportional to dose and ko could be related to k _o /D ⁿ =aD+b, giving n value of 0.7 without MW irradiation and 0.4 with MW irradiation, respectively.