燃煤电站SCR烟气脱硝还原剂尿素热解热源的选择

介绍了燃煤电站SCR尿素热解工艺,结合当前燃料价格,通过工程案例计算,对比了各种尿素热解热源的运行费用。计算结果表明,高温蒸汽加热方案的运行费用最省,但在实际应用中受到相关条件的限制;在一定条件下,燃气加热与电加热方案是工程的优选技术方案。     

草酸浸取废SCR催化剂制备光催化剂

采用草酸浸取废SCR催化剂,得到钛钨粉,制备Bi₂WO₆/钛钨粉复合光催化剂,考察了其对罗丹明B的光催化降解性能。制备光催化剂的优化工艺条件为：采用聚乙烯吡咯烷酮为表面活性剂,n（Bi₂WO₆）∶n（钛钨粉）=2∶1,前驱液pH为5,水热反应时间为18 h。在此条件下制备的光催化剂在可见光下降解罗丹明B,反应 60 min,罗丹明B降解率达94.30%。表征结果显示：钛钨粉小颗粒散落在Bi₂WO₆片表面,为光催化反应提供了更多的活性位点;Bi₂WO₆和钛钨粉两者结合可提高光生电子和空穴的分离效率,进而提高催化剂的光催化活性。Bi₂WO₆/钛钨粉光催化剂对罗丹明 B 的降解符合一级反应动力学规律。     

SCR烟气脱硝工艺的设计特点

选择性催化还原法(SCR)是目前国际上处理火电厂氮氧化物的最主要方法.本文从SCR工艺的原理出发,介绍了与德国STEULER公司在烟气脱硝技术方面合作的相关运行工艺.     

江苏省环保资金事前补助金额校正优化研究--以江苏省燃煤发电机组SCR脱硝工程为例

江苏省环保专项资金一般根据专家经验对项目核定后进行事前补助,事后开展针对项目财务支出的合规性评价,但忽视了专家核定补助金额是否合理。根据近3年江苏省燃煤发电机组SCR脱硝工艺典型项目审计报告,分析了项目审计核定支出额与专家核定支出额的规模(100 MW级及以下、300 MW级、600 MW级及以上)差异、区域(苏南、苏中、苏北)差异及其影响因素,发现100 MW级及以下机组环保资金审计核定支出额显著高于专家核定补助额,在剔除100 MW级及以下机组后,苏南地区项目环保资金审计核定支出额显著高于专家核定补助额,基于此提出了项目补助费用校正优化建议,为环保资金科学分配、提高财政资金支出效率提供了理论依据。     

Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3

Fe203 particle catalysts were experimentally studied in the low temperature selective catalytic reduction （SCR） of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe203 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270℃, and more than 95% NO conversion was obtained at 180℃ when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and 02 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180℃. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.     

制备条件对低温NH_3-SCR脱硝催化剂Mn-Ce/TiO_2结构与性能的影响

采用溶胶凝胶法制备了Mn-Ce/TiO2催化剂,以NH3为还原剂,通过程序升温反应考察其选择性催化还原NO的催化性能.同时,着重探讨了焙烧温度、焙烧时间、活性物质负载量及Mn、Ce负载比例对催化剂结构和性能的影响,并用BET、XRD等对催化剂进行了表征.结果表明,活性组分负载量由0增至20%时,NO转化率随着负载量的增加而提高,当(Mn+Ce)质量分数为20%,催化剂活性最高,此后随着活性组分负载量的增加,NO转化率明显下降;Mn与Ce的负载比例为0.85∶0.15时,催化剂比表面积最大,为112.31m2·g-1;焙烧温度500℃时催化剂晶相均为TiO2锐钛矿型结构,焙烧温度升高至600℃,催化剂晶相为TiO2锐钛矿型和金红石型混合结构,且催化剂比表面积急剧减小;焙烧时间对催化剂晶相结构影响不大,焙烧时间为5h时,Mn-Ce/TiO2的脱硝性能最好.     

汽车尾气净化催化剂Ag/SAPO-34选择性催化还原NO

评价了Ag/SAPO-34分子筛催化剂选择性还原NO的活性,并运用漫反射红外光谱原位研究NO在Ag/SAPO-34催化剂上的选择性催化还原机理.结果表明Ag/SAPO-34有良好的低温活性,在氧气浓度为3.6%和温度为573K～673K时NO还原成N2的转化率达70%;催化剂活性随C3H6浓度的增加而升高,随空速的增加而稍有下降.基于漫反射红外光谱,认为反应机理为:NO、丙烯和氧反应,在Ag/SAPO-34催化剂上生成吸附的有机-氮氧化物,再由这些吸附物种分解成N₂,催化还原的关键是形成有机-氮氧化物中间体.氧的作用是充分促进丙烯活化以及增加NO_x吸附态含量,并且氧的存在是有效产生一系列中间物不可缺少的条件.     

Effect of manufacturing methods of AgCl/Al2O3 catalyst on selective catalytic reduction of NOx

The AgCl/Al2O3 catalyst has potential for use in the selective catalytic reduction (SCR) of NOx. A compound hydrocarbon, following oxygenation is used as a type of reducing agent. In this experiment, the AgCl/Al2O3 catalyst was produced by four different methods, and the differences among their reduction catalysis of NOx were compared. Ethanol was used as a type of reducing agent. X-ray diffraction analysis was performed to study the crystalline structure and scanning electron microscope and transmission electron microscope (TEM) were applied to determine the microindentation. The results indicated that, in the range of 350–400°C, there was no significant difference on the NOx reduction rate; however, there was dispersion at high and low temperature ranges. The size of the AgCl particles was about 20–100 nm.     

Regulated emission characteristics of in-use LNG and diesel semi-trailer towing vehicles under real driving conditions using PEMS

On-road driving emissions of six liquefied natural gas(LNG) and diesel semi-trailer towing vehicles(STTVs) which met China Emission Standard IV and V were tested using Portable Emission Measurement System(PEMS) in northern China.Emission characteristics of these vehicles under real driving conditions were analyzed and proved that on-road emissions of heavy-duty vehicles(HDVs) were underestimated in the past.There were large differences among LNG and diesel vehicles, which also existed between China V vehicles and China IV vehicles.Emission factors showed the highest level under real driving conditions, which probably be caused by frequent acceleration, deceleration, and start-stop.NOx emission factors ranged from 2.855 to 20.939 g/km based on distance-traveled and 6.719–90.557 g/kg based on fuel consumption during whole tests, which were much higher than previous researches on chassis dynamometer.It was inferred from tests that the fuel consumption rate of the test vehicles had a strong correlation with NOx emission, and the exhaust temperature also affected the efficiency of Selected Catalytic Reduction(SCR) aftertreatment system, thus changing the NOx emission greatly.THC emission factors of LNG vehicles were 2.012–10.636 g/km, which were much higher than that of diesel vehicles(0.029–0.185 g/km).Unburned CH_4 may be an important reason for this phenomenon.Further on-road emission tests, especially CH_4 emission test should be carried out in subsequent research.In addition, the Particulate Number(PN) emission factors of diesel vehicles were at a very high level during whole tests, and Diesel Particulate Filter(DPF)should be installed to reduce PN emission.     

选择催化还原（SCR）脱硝技术的特征

选择性催化还原（SCR）技术是目前燃煤电厂应用最多且最成熟的烟气脱硝技术。本文介绍了SCR烟气脱硝技术的特征,对影响SCR法脱硝效率的多种因素进行了简要分析。