喷氨同时脱除NO和NO2过程的化学动力学模拟

本文采用化学动力学模拟的方法，对广泛应用于燃煤锅炉的喷氨脱硝技术进行了研究，首次发现在燃煤锅炉的烟气中喷入氨气不仅可以降低ＮＯｘ的排放量，而且可以同时降低Ｎ２Ｏ的排放量，文中还就喷氨初期的烟气温度、烟气中的含氧量和水分、ＮＯ和Ｎ２Ｏ的初始浓度，烟气中的ＣＯ含量以及喷氨量对喷氨同时脱除ＮＯ２和Ｎ２Ｏ效果的影响进行了计算分析，确定了喷氨同时脱除ＮＯ和Ｎ２Ｏ的最佳条件，对喷氨过程听化学反应机理进行了分析     

Fe2+EDTA溶液络合-铁还原脱除烟气中NO

提出了“Fe2 螯合剂络合-铁粉还原-酸吸收”回收法脱除烟气中NO的新工艺,重点研究了模拟烟气中O2体积分数对NO络合量的影响,以及铁粉用量、铁粉粒径、搅拌速度对NO脱除效率的影响,确定了最佳的铁粉脱氮工艺条件,并对铁粉和铁屑的脱氮效果进行了比较。结果表明,烟气中O2的体积分数从0%增加到4.2%,NO络合量下降90.2%;NO脱除效率随铁粉用量和反应器搅拌速度的增加而增加,随铁粉粒径的增加而降低;过程的最佳工艺参数为,铁粉用量0.8g,铁粉粒径≤0.077mm,搅拌速度900r·min-1,在此条件下,对O2体积分数为5%的模拟烟气在搅拌反应器中可取得90%以上的NO脱除效率;用铁粉在1台搅拌反应器中取得的NO脱除效率和用铁屑在2个鼓泡反应器串联时所取得的效率相当。     

Fe2+EDTA液相对NO的络合作用

对Fe~(2 )EDTA溶液络合NO过程的影响因素的探讨,是“液相络合-铁还原-酸吸收”回收法脱除烟气中NOx技术研究的基础。用鼓泡反应器和模拟烟气,在实验室研究了Fe2 EDTA溶液络合NO的过程,探讨了Fe2 EDTA溶液络合NO过程的影响因素,以及该过程的反应平衡常数。结果表明:Fe2 EDTA溶液对NO的络合能力随时间延长而减弱;Fe2 EDTA溶液对NO的络合容量随着烟气中O2含量的增加和络合温度的升高而降低,随络合液中Fe2 EDTA浓度增加而呈直线增加;pH值为8左右时,Fe2 EDTA溶液对NO的络合容量最大;Fe2 EDTA溶液络合NO的反应平衡常数在实验条件下为105~106L·mol-1数量级,其值随温度升高而降低。     

凹凸棒石负载CuO催化剂脱除气态Hg~0

利用固定床反应器在模拟烟气条件下研究了凹凸棒石(PG)负载CuO催化剂(CuO/PG)对气态Hg~0的脱除.考察了CuO负载量、反应温度、烟气成分、SO_2浓度以及空速等对CuO/PG脱除Hg~0的影响,并利用逐级化学提取和程序升温脱附实验分析了CuO/PG上吸附Hg的形态.结果表明,CuO/PG对Hg~0具有较高的脱除能力,明显高于载体PG,且随CuO负载量的增加而增强(1%—8%);在150—250℃温度范围内,温度升高,CuO/PG对Hg~0的脱除能力降低;HCl对CuO/PG脱除Hg~0具有显著的促进作用,O2具有促进作用,H2O和SO_2具有抑制作用,NO的作用不明显;在6000—15000 h~(-1)空速范围内,空速降低,CuO/PG表现出了更好的脱除Hg~0的能力.逐级化学提取和程序升温脱附实验结果证实,CuO/PG对Hg~0的脱除是吸附和催化氧化的共同作用,Hg~0被氧化为Hg~(2+)的化合物并吸附在CuO/PG上.     

MnO2/H2SO4溶液同时脱硫脱硝实验

采用MnO2/H2SO4溶液作为吸收液,以Fe3+作为催化剂在自制的鼓泡反应器内,对模拟烟气进行同时脱硫脱硝的实验研究,主要考察MnO2浓度、Fe3+浓度、pH值、反应温度、NO浓度、SO2浓度、氧含量、烟气流量等因素对SO2和NO脱除效率的影响.实验结果表明,MnO2浓度、Fe3+浓度、烟气流量、反应温度、NO浓度、SO2浓度对脱硝率影响显著,pH值、氧含量对脱硝率影响不大.在整个实验范围内脱硫效率总是保持在98%以上,脱硝效率最高达到70.9%.     

煤中汞在电厂烟气中的排放特征

为了解燃煤电厂烟气中汞的排放特征,选择江苏省5个地区的7家燃煤电厂,基于美国EPA 30B方法进行现场采样,分析煤中汞含量、机组容量和不同处理设施等对烟气中汞排放的影响。结果表明,煤中汞含量与电厂烟气中汞排放浓度的相关性不强,不起决定性作用;机组容量与烟气中汞排放浓度呈极显著负指数关系(P0.01)。采用循环流化床锅炉燃烧方式且配置静电除尘器的电厂烟气中汞的脱除效率(98.9%)明显高于煤粉炉配置静电除尘器和石灰石-石膏湿法脱硫装置的脱除效率(67.5%~81.6%)。循环流化床并配置静电除尘器装置对电厂烟气中汞的脱除更有利。     

废水生物脱氮中N_2O和NO_x的产生和作用

废水生物脱氮中N2O和NOx来源于硝化、反硝化、厌氧氨氧化和化学反硝化等过程.电子受体和供体浓度、pH、缓冲剂类型、有机负荷、微生物种类及其相互作用等都会影响这些气态中间产物的产生.NO2能够氧化氨和强化好氧和厌氧氨氧化,NO能够阻止C2H2对好氧氨氧化活性的抑制,两者对好氧氨氧化活性的恢复至关重要.所有这些表明,废水生物脱氮的气态中间产物N2O和NOx在氮的生物转化中具有重要的正面作用,甚至必不可少.基于NO2曝气技术和Brocadiaanammoxidans与Nitrosomonas协同作用的废水生物脱氮新技术开发是今后一段时间的重要研究方向.图4参35     

气相色谱同时测定NO、CO、N_2O、CO_2

开展了用气相色谱法同时测定NO、CO、N_2O和CO_2四个组份的分析方法研究。采用501型气相色谱仪,经改装以5分子筛分离,热导及火焰光度检测。对N_2气氛中的NO、CO、N_2O和CO_2四组份得出了准确的定量分析结果。测量下限范围是:CO是150ppm,CO_2是450ppm,N_2O是550ppm。NO是50ppm—2％。本方法具有一些明显的优点。     

石灰氮对设施菜地土壤N_2O排放的影响

为了研究石灰氮对设施菜地土壤N_2O排放的影响,观测了施用尿素、石灰氮、半量尿素与半量石灰氮混施和对照等4个处理设施菜地土壤N_2O排放以及土壤中氮素变化.结果表明,施用石灰氮能显著降低设施菜地土壤N_2O排放量,对照、施用尿素、施用石灰氮和半量尿素与半量石灰氮混施的N_2O累积排放量分别为4135.80μg·kg~(-1)、5794.25μg·kg~(-1)、1957.03μg·kg~(-1)和4341.31μg·kg~(-1),施用尿素的N_2O累积排放量比对照增加了40.1%,施用石灰氮、半量尿素与半量石灰氮混施比施用尿素分别减少了66.2%和25.1%的N_2O排放量,半量尿素与半量石灰氮混施的N_2O累积排放量与对照的差异不显著(P0.05).尿素处理的N_2O排放系数为0.17%,而石灰氮处理和半量尿素与半量石灰氮混施处理的N_2O排放系数则分别减少至0.06%和0.13%.由此表明,施用石灰氮是减少设施菜地土壤N_2O排放的一项有效措施.     

间隙灌溉和控释肥施用耦合措施对稻麦轮作系统土壤微生物群落丰度的影响

间隙灌溉模式下控释肥施用可减缓稻麦轮作系统CH_4和N_2O排放交互排放效应,从而降低综合温室效应,然而有关间隙灌溉和控释肥施用耦合措施对稻麦轮作系统土壤微生物的影响鲜有研究。通过采集稻麦轮作系统田间原位试验新鲜土样,采用核酸定量技术研究间隙灌溉和控释肥施用耦合措施下稻麦轮作系统土壤微生物群落丰度的变化,以探讨此耦合措施降低稻麦轮作系统降低CH_4和N_2O排放的微生物机理。结果发现,除古菌外,稻季土壤细菌、产甲烷菌、甲烷氧化菌、氨氧化菌和反硝化菌群落丰度均高于麦季;间隙灌溉显著影响稻田产甲烷菌、甲烷氧化菌、氨氧化菌和反硝化菌数量的季节变化;与尿素相比,施用控释肥增加了稻麦轮作系统细菌、古菌和产甲烷菌数量,降低了甲烷氧化菌、氨氧化菌、反硝化菌数量。稻季CH_4和N_2O的排放量与土壤微生物丰度之间存在显著相关性:CH_4排放量与古菌、产甲烷菌和甲烷氧化菌数量均呈极显著正相关关系(P0.01),而与氨氧化菌数量呈显著负相关关系(P0.05);N_2O排放量与氨氧化菌、甲烷氧化菌、nirK型和nosZ型反硝化菌数量均呈显著正相关关系(P0.05),而与nir S型反硝化菌无显著相关性。研究表明,间隙灌溉和控释肥施用耦合措施通过影响稻麦轮作系统相关功能微生物的群落丰度进而减缓CH_4和N_2O气体的交互排放效应。     

Enhancing the efficiency of nitrogen removing bacterial population to a wide range of C:N ratio (1.5:1 to 14:1) for simultaneous C & N removal

• Simultaneous C & N removal in Methammox occurs at wide C:N ratio. • Biological Nitrogen Removal at wide C:N ratio of 1.5:1 to 14:1 is not reported. • Ammonia removal shifted from mixotrophy to heterotrophy at high C:N ratio. • Acetogenic population compensated for ammonia oxidizers at high C:N ratio. • Methanogens increase the plasticity of nitrogen removers at high C:N ratio. High C:N ratio in the wastewater limits biological nitrogen removal (BNR), especially in anammox based technologies. The present study attempts to improve the COD tolerance of the BNR process by associating methanogens with nitrogen removing bacterial (NRB) populations. The new microbial system coined as ‘Methammox’, was investigated for simultaneous removal of COD (C) and ammonia (N) at C:N ratio 1.5:1 to 14:1. The ammonia removal rate (11.5 mg N/g VSS/d) and the COD removal rates (70.6 mg O/g VSS/d) of Methammox was close to that of the NRB (11.1 mg N/g VSS/d) and the methanogenic populations (77.9 mg O/g VSS/d), respectively. The activities established that these two populations existed simultaneously and independently in ‘Methammox’. Further studies in biofilm reactor fetched a balanced COD and ammonia removal (55%–60%) at a low C:N ratio (≤2:1) and high C:N ratio (≥9:1). The population abundance of methanogens was reasonably constant, but the nitrogen removal shifted from mixotrophy to heterotrophy as the C:N ratio shifted from low (C:N≤2:1) to high (C:N≥9:1). The reduced autotrophic NRB (ammonia- and nitrite-oxidizing bacteria and Anammox) population at a high C:N ratio was compensated by the fermentative group that could carry out denitrification heterotrophically. The functional plasticity of the Methammox system to adjust to a broad C:N ratio opens new frontiers in biological nitrogen removal of high COD containing wastewaters.     

Selective reduction of NO by photo-SCR with ammonia in an annular fixed-film photoreactor

Gaseous NO was photocatalytically reduced at room temperature by photo-assisted selective catalytic reduction (photo-SCR) with ammonia over TiO₂ in this study. NO reduction efficiency and N₂ selectivity were determined from gases composition at the outlet stream of photoreactor. Effect of operating conditions, e.g. light intensity and inlet concentrations of ammonia and oxygen, on the NO reduction efficiency and N₂ selectivity were discussed to determine the feasible operating condition for photocatalytic reduction of NO. Experimental results showed that selective catalytic reduction of NO with ammonia over TiO₂ in the presence of oxygen was a spontaneous reaction in dark. The photoirradiation on the TiO₂ surface caused remarkable photocatalytic reduction of NO to form N₂, NO₂, and N₂O under 254 nm UV illuminations, while almost 90% of N₂ selectivity was achieved in this study. The ammonia and oxygen molecules played the roles of reductant and oxidant for NO reduction and active sites regeneration, respectively. The reduction of NO was found to be increased with the increase of inlet ammonia and oxygen concentrations until specific concentrations because of the limited active sites on the surface of TiO₂. The kinetic model proposed in this study can be used to reasonably describe the reaction mechanism of photo-SCR.     

以工业级TiO2为载体负载不同助催化剂V2O5基脱氮催化剂的性能

在工业级TiO2载体上,通过浸渍法负载V2O5,WO3和MoO3等活性物质,制备不同V2O5基的烟气脱氮催化剂．在固定床反应器中测试DeNOx活性,研究不同的助催化剂(WO3和MoO3)对该类型催化剂DeNOx活性的影响,结果表明,在三元催化剂中,V2O5是主活性物质,MoO3和WO3是助催化剂,此外,V2O5-MoO3／TiO2的脱氮效率高于V2O5-WO3／TiO2,但N2O的生成量较大。     

碳源与底物对不同层次土壤产生N2O能力的影响

底层土壤的反硝化作用是土壤排放N_2O的重要来源,同时也是影响浅层地下水硝酸盐含量的重要因素.通过一系列室内培养试验.研究了一种农用土壤不同土层在碳源和NO_3含量不同情况下产生N_2O的能力。结果表明,试验用土壤的不同土层均具有进行反硝化作用产生N_2O的能力.底层土壤产生N_2O的能力大于根区土壤:单独添加葡萄糖、NO_3或同时添加葡萄糖和NO_3.对土壤N_2O和CO_2释放的影响与土壤层次和观测时间有关;向土壤添加葡萄糖和NO_3,各个土层释放N_2O的能力均显著提高;从产生N_2O和CO_2能力的角度而言,不同层次土壤的微生物区系间存在较大差异。采用短期(24h之内)饱和泥浆好气培养法,可以区分土壤微生物区系在产生N_2O方面的差异。     

Electricity-driven ammonia oxidation and acetate production in microbial electrosynthesis systems

• MES was constructed for simultaneous ammonia removal and acetate production. • Energy consumption was different for total nitrogen and ammonia nitrogen removal. • Energy consumption for acetate production was about 0.04 kWh/g. • Nitrate accumulation explained the difference of energy consumption. • Transport of ammonia and acetate across the membrane deteriorated the performance. Microbial electrosynthesis (MES) is an emerging technology for producing chemicals, and coupling MES to anodic waste oxidation can simultaneously increase the competitiveness and allow additional functions to be explored. In this study, MES was used for the simultaneous removal of ammonia from synthetic urine and production of acetate from CO₂. Using graphite anode, 83.2%±5.3% ammonia removal and 28.4%±9.9% total nitrogen removal was achieved, with an energy consumption of 1.32 kWh/g N for total nitrogen removal, 0.45 kWh/g N for ammonia nitrogen removal, and 0.044 kWh/g for acetate production. Using boron-doped diamond (BDD) anode, 70.9%±12.1% ammonia removal and 51.5%±11.8% total nitrogen removal was obtained, with an energy consumption of 0.84 kWh/g N for total nitrogen removal, 0.61 kWh/g N for ammonia nitrogen removal, and 0.043 kWh/g for acetate production. A difference in nitrate accumulation explained the difference of total nitrogen removal efficiencies. Transport of ammonia and acetate across the membrane deteriorated the performance of MES. These results are important for the development of novel electricity-driven technologies for chemical production and pollution removal.     

施氮水平对小麦-玉米轮作体系氨挥发与氧化亚氮排放的影响

试验采用密闭室间歇通气法研究华北平原冬小麦（Triticum aestivum Linneaus）-夏玉米（Zea mays Linneaus）轮作体系在不同施氮水平下农田氨挥发和N2O排放。结果表明：冬小麦季和夏玉米季的氨挥发速率与N2O排放通量呈现出季节性动态变化,且随着施氮量的增加而增加,均在施肥后第2~3天出现峰值。玉米季氨挥发量和N2O排放量均高于小麦季,分别占整个轮作周期气态损失的53.5%~68.9%和54.7%~82.3%。轮作体系中氨挥发净损失量（以N计）为4.28~31.31 kg.hm-2,占施氮量的3.17%~5.80%;N2O净排放损失量（以N计）为50.95~1051.03 g.hm-2,占施氮量的比例为0.04%~0.23%。因此,施氮量是影响冬小麦-夏玉米轮作体系气态损失重要因素,且夏玉米季是控制控制气态损失的关键时期。     

硝化反硝化过程中N_2O释放影响因素

结合N2O的产生机理,分析温度、含水率、NO2--N和底物质量浓度、pH和碱度、O2以及基质等因素对N2O释放的影响,试图探讨不同因素对N2O释放的影响规律,以期对生化过程中N2O的控制提供理论和技术支持。N2O的释放是温度、含水率、C/N、O2浓度、反应底物质量浓度、基质以及传输过程交互作用的结果。含水率、C/N、基质及温度等可通过不同途径影响溶解氧的质量浓度而影响N2O释放量;pH、NO2--N、NH3-N及温度等通过影响硝化、反硝化细菌的活性或对各阶段酶的抑制作用而影响N2O释放;土壤利用类型、植被种类、污水脱氮过程各参数等,会间接影响硝化和反硝化过程从而影响N2O的释放。     

电子束脱除烟道气中硫和氮过程的计算机模拟

电子束干法脱硫脱硝的技术可以同时去除烟道气中的NOx与SO2。根据该处理方法建立脱除NOx和SO2的化学反应机理，并使用计算机模拟的方法，考察体系温度、辐照剂量和氨浓度与去除效率的关系。     

ZrO2负载过渡金属氧化物催化剂对CO＋NO（O2）反应的影响

本文运用固定床微反技术考察了Ｃｕ,Ｆｅ,Ｍｎ,Ｃｒ,Ｃｏ和Ｎｉ负载（ＺｒＯ２载体）氧化物对ＣＯ＋ＮＯ（Ｏ２）反应的催化活性。研究了ＮＯ和ＣＯ在不同比例时,催化剂对Ｎ２Ｏ和Ｎ２生成的影响。结果表明,在ＮＯ＋ＣＯ反应中,ＮＯ和ＣＯ的比例对催化剂活性和Ｎ２Ｏ,Ｎ２生成均有明显的影响,ＣｕＯｘ／ＺｒＯ２催化剂的活性最高;Ｎ２Ｏ是ＮＯ＋ＣＯ反应的中间产物,低温或ＮＯ过量时有利于生成Ｎ２Ｏ,高温或ＮＯ不足时有