抗坏血酸对Fe2+/H2O2体系氧化NO的促进作用

采用实验方法研究了低成本环境友好型添加剂抗坏血酸(AA)对Fe²⁺/H₂O₂体系氧化NO气体及其对体系内H₂O₂分解的影响,分析了AA对体系氧化NO能力及H₂O₂分解的影响机制。研究结果表明:AA通过加速Fe³⁺向Fe²⁺的转化而促进Fe²⁺/H₂O₂体系对NO的氧化。[AA]₀:[Fe²⁺]₀对体系氧化NO的能力及H₂O₂的分解具有重要影响。综合考虑NO氧化脱除量及H₂O₂消耗量,合理的[AA]₀:[Fe²⁺]₀为1/3~1/2。AA的分次添加方式可大幅度提升体系氧化NO气体的能力。研究结果可望为发展基于H₂O₂为氧化剂的烟气NO绿色氧化技术提供理论基础。     

不同尺寸反应器内H2O2热分解氧化NO特性与氧化产物分析

采用实验方法研究了不同尺寸滴管炉反应器内H₂O₂热分解氧化NO特性。对比了不同H₂O₂蒸发条件对NO氧化率的影响规律。分析了气体温度、H₂O₂溶液浓度、H₂O₂：NO摩尔比、NO初始浓度及气体流量对NO氧化率的影响。检测了氧化产物并分析了产物的生成路径。结果表明：H₂O₂的快速蒸发是其热分解氧化NO的前提。减小H₂O₂液滴尺寸或液膜厚度可加速H₂O₂蒸发与分解,提高NO氧化率,扩宽NO氧化的温度范围。保证蒸发速率可削弱H₂O₂浓度对NO氧化率的影响。当H₂O₂：NO < 10时,NO氧化率随H₂O₂：NO的增加而增加;当H₂O₂：NO>10时,NO氧化率几乎不随H₂O₂：NO变化。H₂O₂热分解对于较高浓度的NO具有更高的氧化效率。H₂O₂热分解氧化NO的主要产物为NO₂。HO₂·直接将NO氧化为NO₂,·OH则先将NO转化为HONO,然后进一步氧化为NO₂。     

二乙烯三胺五亚甲基膦酸/Fenton体系氧化脱除NO

针对当前Fenton氧化法脱除燃煤烟气中NO的过程中H₂O₂大量无效分解生成氧气的缺点,本文采用二乙烯三胺五亚甲基膦酸(DTPMPA)/Fenton系统进行氧化脱除NO的实验研究。结果表明：该系统在NO脱除效率为95.1%的情况下,H₂O₂无效分解占比降低至15.5%。DTPMPA浓度的增加抑制了H₂O₂无效分解,其浓度较低时促进NO脱除而浓度较高时抑制NO脱除;H₂O₂及Fe²⁺浓度的增加均对NO脱除及H₂O₂无效分解有一定的促进作用,但二者浓度过高时亦均对脱除NO有一定抑制作用;降低反应温度对NO脱除影响较小,但会削弱H₂O₂无效分解;SO₂对NO的脱除及H₂O₂无效分解影响甚小。电子自旋共振技术和淬灭剂添加实验结果表明：DTPMPA的...     

Fe2+/H2O2体系内各种自由基在氧化NO中的作用

Fe²⁺/H₂O₂体系可分解产生多种氧化性自由基, 主要包括O₂^-·、·OH和HO₂·。本文实验研究了O₂^-·、·OH及HO₂·在Fe²⁺/H₂O₂体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O₂^-·对NO气体的氧化作用不明显;·OH及HO₂·是该体系氧化NO气体的主要活性物质, 其中·OH的氧化作用更大。加快自由基的生成速率可以增强Fe²⁺/H₂O₂体系对NO气体的氧化能力, 但O₂的生成速率同时加快。只有少量·OH及HO₂·参与NO的氧化, ·OH与HO₂·之间的快速反应是Fe²⁺/H₂O₂体系氧化NO过程中H₂O₂利用率低的主要原因。     

臭氧氧化结合硫代硫酸钠溶液喷淋同时脱硫脱硝

采用臭氧氧化结合湿法喷淋硫代硫酸钠溶液的方法开展模拟烟气同时脱硫脱硝实验研究。结果表明,采用臭氧氧化结合Na₂S₂O₃-NaOH溶液湿法喷淋可以实现NO_x和SO₂协同脱除:在O₃/NO摩尔比为1.1～1.2时,溶液中Na₂S₂O₃浓度的增加会提高系统的NO_x脱除效率,烟气中SO₂的存在会促进NO_x的脱除,当SO₂浓度为1030 mg·m^-3、2.0%Na₂S₂O₃溶液作为喷淋液时可实现较高的SO₂脱除效率,同时NO_x脱除效率可达70%以上;喷淋液pH在2.5～9范围内变化时提高浆液pH有利于NO_x的脱除,当pH 9时脱硝效率可达75%。180 min连续同时脱硫脱硝实验结果表明,硫代硫酸钠可有效促进NO_x的脱除,并实现SO₂较高的脱除效率,同时可实现系统同时脱硫脱硝连续稳定运行,喷淋吸收后烟气中NO_x的主要转化产物为NO₂^-, 该方法作为一种有效的同时脱硫脱硝技术,具有一定的工业应用推广前景。     

Fe2+/H2O2体系O2生成路径

掌握Fe²⁺/H₂O₂体系O₂的生成路径,可为避免H₂O₂无效分解,开发经济高效的Fe²⁺/H₂O₂体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe²⁺/H₂O₂体系内各种自由基对O₂生成速率的影响,进而确定O₂的生成路径。结果表明:Fe²⁺/H₂O₂体系内不会产生大量O₂^-·,O₂^-·不是生成O₂的主要反应物质;O₂^-·被全部捕获后,体系中仍产生大量O₂^-·,但此时无O₂生成,证明生成O₂的反应由·OH和HO₂·两种自由基直接参与。分析认为反应·OH+HO₂·-H₂O+O₂是体系内O₂生成的主要路径。控制Fe²⁺/H₂O₂体系定向生成·OH,抑制HO₂·的产生,是提高Fe²⁺/H₂O₂体系中H₂O₂利用率的有效手段。     

基于α-FeOOH催化H2O2蒸气的低温烟气脱硝实验

针铁矿是分布广泛、储量丰富的铁氧化物,其主要成分为α-羟基氧化铁（α-FeOOH）。为了探究针铁矿在催化H₂O₂烟气脱硝反应中的性能,本文通过沉淀-水解法制备了α-FeOOH,并在自行搭建的实验台上开展了α-FeOOH催化H₂O₂的低温烟气脱硝实验研究,深入分析了H₂O₂流量、H₂O₂浓度、汽化温度、反应温度和共存气体浓度等工况参数对脱硝性能的影响。采用离子色谱（IC）分析了单独脱硝反应和同时脱硫脱硝反应后的含氧酸成分,结合各项表征分析技术考察了催化剂反应前后的理化特性和稳定性。实验结果显示,随着汽化温度和反应温度的升高,NO的脱除效率先增加后降低;增加H₂O₂浓度对脱硝效率有明显的促进作用。当汽化温度为140℃、反应温度为160℃时,以2.5mL/h注入10mol/L的H₂O₂脱硝效率达到80%。当SO₂浓度为1000μL/L时,脱硝效率提高至86.4%。离子色谱分析结果显示,单独脱硝反应和同时脱硫脱硝反应后含氧酸产物为HNO₃和H₂SO₄。反应前后催化剂的表征结果显示,α-FeOOH在脱硝反应后依然具有良好的稳定性,显示出针铁矿在低温烟气脱硝工艺中的潜在应用前景。     

钙镁氧化物及氢氧化物脱除SO3协同防治催化剂低温失活

在实验室中试台架上,开展了Ca(OH)₂、CaO、Mg(OH)₂和MgO四种碱基吸附剂粉体喷射脱除烟气SO₃的实验,研究了碱基吸附剂脱除烟气SO₃的影响因素,探究了碱基吸附剂脱除SO₃技术对选择性催化还原（SCR）催化剂硫酸氢铵失活温度的影响。采用比表面积法（BET）、傅里叶红外光谱（FTIR）等手段对吸附剂进行表征,以判断吸附产物和吸附机理。结果显示：碱基氢氧化物吸附剂的SO₃脱除效果优于碱基氧化物吸附剂;Mg基吸附剂优于Ca基吸附剂;当烟气中SO₃浓度为35μL/L时,Mg(OH)₂含量为600mg/m³时具有最高的SO₃脱除效率,达到95%左右。对低温失活后的SCR催化剂进行FTIR表征证实了催化剂表面硫酸氢铵的生成。此外,通过碱基吸附剂降低烟气中SO₃浓度后,SCR催化剂在低温时的失活得到了显著缓解,可明显降低SCR催化剂的硫酸氢铵失活温度约20℃,有助于挖掘机组调峰深度。     

喷淋鼓泡塔内氨水对烟气中As2O3的吸收特性

喷淋鼓泡塔内的反应是典型的气液两相流,为研究喷淋鼓泡内氨水对烟气中As₂O₃吸收特性,探索新型喷淋鼓泡技术的污染物一体化控制潜力,以空气和SO₂为模拟烟气,利用喷淋鼓泡吸收塔研究了液气比、浸液深度、氨水质量浓度、SO₂质量浓度对氨水吸收气相As₂O₃的影响。研究表明：氨水对As₂O₃的吸收效率随液气比增加先增大后趋于平缓;浸液深度增大,氨水吸收As₂O₃的效率降低;As₂O₃与氨水中OH^-作用生成的AsO₃^3-溶于氨水实现氨水对As₂O₃的吸收,氨水吸收As₂O₃的效率随氨水质量浓度的增大先上升后下降;碱性环境下,SO₂与NH₃作用生成SO₃^2-的水解增加了溶液中OH^-,促进了氨水对As₂O₃的吸收,又因SO₃^2-水解产生HSO₃^-电离出H⁺对部分OH^-中和以及NH₃挥发等因素,促进作用表现为吸收效率随SO₂质量浓度的增加先上升后下降。在氨水质量浓度为0.07%、SO₂质量浓度为525mg/m³、液气比10L/m³、浸液深度5cm时吸收效率达到最大82%。     

添加剂CH3COONH4对介质阻挡-电晕放电耦合法脱除NO、SO2的影响

采用自行研究设计的介质阻挡-电晕放电等离子体反应装置在模拟烟气中进行NO、SO₂的脱除研究。考察了O₂、CO₂、水蒸气等气体组分对脱除NO、SO₂的影响,并进一步探讨了添加剂CH₃COONH₄对脱除NO、SO₂的影响及作用机理。实验结果表明：O₂、CO₂和水蒸气浓度的增加对NO脱除有抑制作用,而引入CH₃COONH₄后,这些抑制作用会被减弱,使NO的脱除率得到大幅度提升,但这些抑制作用不会完全消除。在引入CH₃COONH₄后,气体组分和输入电流的变化对脱除SO₂的影响不明显,SO₂脱除率可达到94%左右。在N₂/O₂/CO₂/H₂O/NO/SO₂体系中加入0.27%的CH₃COONH₄后,NO初始浓度不变的条件下,SO₂含量较少时,对NO的脱除影响不明显,随着SO₂浓度的增加,NO的脱除率不断下降,增加CH₃COONH₄的添加量可消除SO₂的影响;另一方面,在SO₂初始浓度恒定的条件下,随着NO含量的增加,SO₂的脱除率保持在94%左右。在N₂/O₂/CO₂/H₂O/NO/SO₂体系中加入0.51%的CH₃COONH₄后,输入电流2.5A时,NO的脱除率达到72%。     

介质阻挡放电中气体成分对NOx脱除的影响

利用介质阻挡放电(DBD)产生低温等离子体进行烟气的脱硝实验,研究了在乙烯存在的条件下,温度和其他烟气成分对NO_x脱除率的影响。结果表明:随着温度的升高,NO脱除速率增快;模拟烟气中加入CO₂,在能量密度较低时,CO₂作为电负性分子会降低自由基的生成,导致NO的脱除率降低,随着能量密度的升高,CO₂对NO脱除的影响减小;模拟烟气中加入水后可以产生更多的OH、HO₂等自由基,促进NO的氧化;SO₂的加入会与自由基O反应,使初始反应中O与C₂H₄的反应速率减弱,从而影响了NO的氧化速率,但O₃、HO₂等强氧化自由基会优先与NO反应,因此SO₂的加入不会影响NO最终的脱除率。     

UV/H2O2氧化联合CaO吸收脱除NO的传质-反应动力学

在实验室规模的光化学反应器中,基于实验研究﹑动力学理论以及双膜理论,研究了UV/H₂O₂氧化联合CaO吸收(UV/H₂O₂-CaO工艺)脱除燃煤烟气中NO的传质-反应动力学。分析了NO吸收的传质-反应过程,明确了NO吸收过程的主要控制步骤和强化措施,测定了关键的动力学参数,推导了NO吸收过程的理论模型。结果表明:在实验范围内,NO吸收速率随着NO浓度的增加几乎呈线性增加。随着H₂O₂浓度和CaO浓度的增加,NO的吸收速率均呈现先增加后变缓的趋势。UV/H₂O₂-CaO工艺脱除NO是一个拟一级快速反应过程,强化气相主体扰动﹑增加气液接触面积和提高NO分压可有效提高NO的吸收速率。NO吸收速率方程的计算值和实验值具有较好的一致性。     

Removal of elemental mercury from simulated coal-combustion flue gas using a SiO2–TiO2 nanocomposite

A novel silica–titania (SiO₂–TiO₂) nanocomposite has been developed to effectively capture elemental mercury (Hg⁰) under UV irradiation. Previous studies under room conditions showed over 99% Hg⁰ removal efficiency using this nanocomposite. In this work, the performance of the nanocomposite on Hg⁰ removal was tested in simulated coal-fired power plant flue gas, where water vapor concentration is much higher and various acid gases, such as HCl, SO₂, and NO_x, are present. Experiments were carried out in a fix-bed reactor operated at 135 °C with a baseline gas mixture containing 4% O₂, 12% CO₂, and 8% H₂O balanced with N₂. Results of Hg speciation data at the reactor outlet demonstrated that Hg⁰ was photocatalytically oxidized and captured on the nanocomposite. The removal efficiency of Hg⁰ was found to be significantly affected by the flue gas components. Increased water vapor concentration inhibited Hg⁰ capture, due to the competitive adsorption of water vapor. Both HCl and SO₂ promoted the oxidation of Hg⁰ to Hg(II), resulting in higher removal efficiencies. NO was found to have a dramatic inhibitory effect on Hg⁰ removal, very likely due to the scavenging of hydroxyl radicals by NO. The effect of NO₂ was found to be insignificant. Hg removal in flue gases simulating low rank coal combustion products was found to be less than that from high rank coals, possibly due to the higher H₂O concentration and lower HCl and SO₂ concentrations of the low rank coals. It is essential, however, to minimize the adverse effect of NO to improve the overall performance of the SiO₂–TiO₂ nanocomposite.     

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     

Simultaneous Removal of NO and SO2 from Flue Gas by UV/H2O2/CaO

The effects of several influencing factors (CaO and H₂O₂ concentration, gas flow, solution temperature, NO, SO₂, O₂ and CO₂ concentration) on the simultaneous removal of NO and SO₂ from flue gas by using a UV/H₂O₂/CaO process were studied. In addition, the anions in the liquid phase were measured by ion chromatography and the material balances for NO and SO₂ were calculated. It was found that, under all experimental conditions, this process achieved a SO₂ removal efficiency of 100 %. With the increase in CaO concentration, NO removal efficiency first increased and then remained almost unchanged. With the increase in H₂O₂ concentration, NO removal efficiency increased but the changes gradually became smaller. NO removal efficiency greatly decreased with increasing gas flow, NO concentration and CO₂ concentration. Slightly increasing the solution temperature and SO₂ concentration reduced NO removal efficiency. Increasing O₂ concentration can promote the removal of NO. The anions in the liquid phase were mainly SO₄^2– and NO₃^–. Most of the low valence nitrogen elements in NO and the low valence sulfur elements in SO₂ transformed into the high valence nitrogen element in NO₃^– and the high sulfur element in SO₄^2–.     

活性焦汞吸附特性及动力学机理分析

通过固态吸附剂汞吸附效能测定系统进行了太西活性焦吸附单质汞的实验,考察单质汞Hg⁰入口浓度和温度对太西活性焦脱汞性能的影响并探讨了吸附机理。结果表明:在CO₂/N₂/O₂/NO/Hg⁰体系中,不同Hg⁰入口浓度获得的汞脱除效率曲线相似,脱除效率随Hg⁰入口浓度增大而增加;变入口浓度工况下,汞的吸附全过程遵循准二级动力学反应模型,该吸附过程以化学吸附为主;在反应温度从403 K升高到423 K的过程中,系统发生了化学吸附或者化学反应,423 K可作为活性焦的最佳除汞温度;Bangham方程可对变温工况下活性焦脱除单质汞的吸附过程进行准确描述,并获得不同温度下活性焦脱汞的吸附速率常数存在k_423K>k_463K>k_403K的关系。     

TiO2-V2O5纳米纤维光催化氧化烟气中的Hg0

对静电纺丝法制备的TiO₂和TiO₂-V₂O₅纳米纤维进行光催化脱除模拟烟气中Hg⁰的研究。对纳米纤维进行了SEM、TEM、XRD、BET和UV-Vis检测。结果表明TiO₂-V₂O₅纳米纤维为锐钛矿,V₂O₅高度分散在TiO₂中。纤维直径在200 nm左右,由粒径为10 nm左右的微粒组成。掺杂V₂O₅后,纤维的吸光范围扩大,在可见光范围内的吸光度比纯TiO₂时有了很大提高。实验研究了不同光照条件、V₂O₅的掺杂量和循环次数对脱汞的影响,分析了TiO₂-V₂O₅催化脱汞的机理。当V₂O₅的质量含量为3%时,TiO₂-V₂O₅在可见光下的脱汞率可达到66%,比纯TiO₂时的7%有了显著提高;纤维的脱汞性能稳定,多次循环后紫外光和可见光下的脱汞率仍分别保持在80%和65%左右。电子的跃迁和电子、空穴的快速分离是TiO₂-V₂O₅在可见光下脱汞率提高的主要原因。     

Advanced Oxidative Removal of Nitric Oxide from Flue Gas by Homogeneous Photo‐Fenton in a Photochemical Reactor

In this work, advanced oxidation removal of nitric oxide (NO) from flue gas by homogeneous Photo‐Fenton was investigated in a photochemical reactor and the effects of several influencing factors on NO removal were evaluated. The gas‐liquid reaction products were determined. The reaction pathways of NO removal are also preliminarily discussed. It was found that with the increase of Fe²⁺ concentration, NO removal efficiency first increased and then decreased. Increasing H₂O₂ concentration and UV radiation intensity greatly increased NO removal efficiency, but the growth rates gradually became smaller. NO removal efficiency greatly reduced with the increase of gas flow and NO concentration, and only slightly decreased with the increase of solution temperature, but significantly increased with the increase of initial solution pH value. The main anion product in the liquid phase was NO₃^–. With respect to removal of NO using homogeneous Photo‐Fenton, ·OH oxidation was the main reaction pathway, and H₂O₂ oxidation was the secondary reaction pathway.     

亚硝酸盐对聚磷菌反硝化除磷代谢及N2O产生的影响

以乙酸钠/丙酸交替为碳源的强化生物除磷(enhance biological phosphorus removal, EBPR)系统为研究对象,母反应器内种泥在厌氧/好氧的运行条件下已培养340 d,聚磷菌富集纯度达到92%±3%,考察了不同浓度亚硝酸盐氮(44.64、70.3、94.33、112.36 mg NO₂^--N·L^-1)为电子受体对聚磷菌缺氧吸磷代谢的影响。结果表明,从未经缺氧驯化的高纯度聚磷菌也可以进行反硝化除磷代谢。在缺氧反应过程中NO₂^--N还原速率、PO₄^3--P吸收速率、PHA降解速率随着亚硝酸浓度升高呈下降趋势,但是在初始亚硝酸盐氮浓度最高为112.36 mg NO₂^--N·L^-1条件下,代谢并未停止,此时亚硝酸盐还原速率与磷酸盐吸收速率仍可以分别达到2.61 mg NO₂^--N·(g MLSS)^-1·h^-1和3.0 mg PO₄^3--P·(g MLSS)^-1·h^-1。聚磷菌在以细胞内PHA作为碳源以NO₂^--N作为电子受体反硝化除磷代谢过程中,由于初始亚硝酸盐的抑制作用使NO₂^--N还原速率大于N₂O还原速率,从而产生大量的N₂O积累。初始投加NO₂^--N浓度为44.64、70.3、94.33、112.36 mg NO₂^--N·L^-1时,产生的N₂O占TN的比例分别为63.5%、49.0%、30.2%、24.0%。在底物充足的条件下,代谢中积累的N₂O可以通过延长缺氧搅拌时间,使其转化为N₂。