不同粒径煤粉在空气和O2/CO2下燃烧NO生成特性

采用水平管式炉,研究了不同粒径组合的煤粉在不同气氛和温度条件下燃烧过程中的NO释放特性,结果表明:O2/CO2下NO排放量比O2/N2气氛下NO排放量低,温度升高会使NO排放峰值提前,在常规粒径煤粉中添加超细粒径煤粉能够降低NO排放量,且温度越低效果越明显.     

O_2/CO_2燃煤锅炉燃烧过程的数值模拟

O2/CO2燃烧技术应用于燃煤锅炉是捕获和储存CO2的有效方法之一。高浓度、高比热值CO2的存在对煤粉的着火特性和锅炉炉内的温度场分布有重要影响。利用Fluent流体力学软件,以300MW煤粉锅炉为物理模型,对比煤粉锅炉在O2/CO2与空气下炉内温度场分布的差异,分析含氧浓度、二次风温度对锅炉炉内温度场的影响。结果表明:煤粉在O2/CO2比空气气氛下着火有所延迟,火焰中心位置升高,炉内的整体温度偏低,燃烧稳定性差;随富氧程度和二次风温的增加,煤粉燃烧与火焰传播特性改善,当O2/CO2体积比为29/71时炉内温度水平提高较快,与空气助燃条件下炉内温度分布接近。     

300MW燃煤锅炉在O_2/CO_2气氛下NO_x排放的数值模拟

针对300 MW机组配用的四角切圆燃烧煤粉锅炉,结合O2/CO2燃烧技术特点,运用数值模拟的方法,探索四角切圆燃烧煤粉锅炉运行中NOx生成规律及影响因素。结果分析表明:O2/CO2燃烧技术能够使得烟气中CO2浓度达到90%以上,能够方便的回收和封存CO2,以减少温室效应;O2/CO2燃烧技术能够使用劣质煤,燃料范围广泛;O2/CO2气氛下NOx排放量明显减少。     

O_2/CO_2气氛下煤粉燃烧特性模拟研究

针对煤粉燃烧器燃烧工况,采用Fluent软件,探索辐射模型、气氛和煤粉粒径对煤粉燃烧过程的影响及污染物生成情况。结果表明:采用DO+WSGG模型时,煤粉的燃烧温度有所降低;跟空气气氛相比O_2/CO_2气氛下煤粉的燃烧温度降低,NO的量也降低;氧浓度增大,煤粉燃烧的温度峰值增加;随着超细煤粉混合比的增加,燃烧高温区而向前移。     

CeO2-Co3O4 Catalysts for CO Oxidation

CeO2-Co3O4 catalysts for low-temperature CO oxidation were prepared by a co-precipitation method. In combination with the characterization methods of N2 adsorption/desorption, XRD, temperature-programmed reduction （TPR）, and FT-IR, the influence of the cerium content on the catalytic performance of CeO2-Co3O4 was investigated. The results indicate that the prepared CeO2-Co3O4 catalysts exhibit a better activity than that of pure CeO2 or pure Co3O4. The catalyst with the Ce/Co atomic ratio 1 ： 16 exhibits the best activity, which converts 77% of CO at room temperature and completely oxidizes CO at 45 ℃.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3：Eu^3＋ phosphor

The Gd2O2CO3：Eu^3＋ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet （VUV） region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer （CT） of Gd^3＋-O2^- were observed for Gd2O2CO3：Eu^3＋. Under 172 nm excitation, Gd2O2CO3：Eu^3＋ exhibited strong red emission with good color purity, indicating Eu^3＋ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3：Eu^3＋ was （x=0.652, y=0.345）. The photoluminescence quenching concentration of Eu^3＋ excited by 172 nm for Gd2O2CO3：Eu^3＋ was about 5%. Gd2O2CO3：Eu^3＋ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

CeO2和La2O3对高炉喷吹煤粉燃烧过程的影响

在模拟高炉喷吹的条件下,对添加CeO2 和La2O3的混合煤粉进行了燃烧试验,考察了稀土氧化物对高炉喷吹煤粉燃烧过程的影响,并探讨了其助燃作用机理.     

CO2+O2地浸采铀中CaCO3沉淀堵塞条件模拟

CO2+O2地浸工艺是我国第三代铀矿采冶技术,地浸过程中溶浸液与含矿层矿物反应后,在将铀从矿石中浸出的同时,由于地下水矿化度增高又会产生化学沉淀,导致含矿层堵塞。CaCO3沉淀是CO2+O2地浸采铀过程中含矿层堵塞的重要原因。根据内蒙古纳岭沟铀矿CO2+O2浸铀过程中浸出液化学成分数据,通过水文地球化学模拟,对含矿层堵塞的水文地球化学条件进行了系统研究。结果表明,CaCO3沉淀是造成CO2+O2地浸中含矿层化学堵塞的重要原因。当溶浸液pH>6.5时,CaCO3将发生沉淀,溶浸液的pH、HCO3-浓度、Ca2+浓度是影响CaCO3沉淀的主要因素,过高的pH与HCO3-浓度、Ca2+浓度都会造成CaCO3沉淀的产生。根据模拟结果获得了不产生CaCO3沉淀条件下pH、HCO3-浓度、Ca2+浓度三者之间的关系,并由此认为,维持溶浸液较低的Ca2+浓度与较低的pH是预防与缓解CaCO3沉淀堵塞的有效途径。     

复合催化剂TiO2/Fe2O3的制备及其光催化性能

以Fe2O3和TiCl4为原料,通过水解法制备Fe2O3/TiO2包覆型复合光催化剂,并用XRD、SEM进行表征。以甲基橙为模型污染物,比较了Fe2O3、TiO2和TiO2/Fe2O3的光催化活性,确定了Fe2O3和TiO2的最佳配比,同时探讨了反应机理。     

光催化功能Fe_2O_3/TiO_2陶瓷的制备及其光降解特性

以九水硝酸铁和硫酸钛为原料,利用共沉淀法合成了Fe2O3/TiO2混合粉体,粉体压制成型的素坯经过高温烧结制备Fe2O3/TiO2陶瓷。通过XRD、SEM分析Fe2O3/TiO2多孔陶瓷的物相和微观结构,并通过对甲基蓝溶液(浓度为25mg/L)的降解研究其光催化性能和循环使用性能。结果表明:紫外和可见光条件下,该陶瓷第一次使用时对甲基蓝溶液的最大降解率分别是80%和94%,循环使用三次后,最大降解率分别仅下降16%和17%。所制备的Fe2O3/TiO2陶瓷具有良好的光催化性能和循环使用性能,且利于收集,可以广泛应用于污水处理。     

Effect of Fe2O3 Loading Amount on Catalytic Properties of Monolithic Fe2O3/Ce0.67Zr0.33O2 -Al2O3 Catalyst for Methane Combustion

Ce0.67Zr0.33O2-Al2O3 solid solution was prepared by the co-precipitation method. Fe2O3-based catalysts supported on the solid solution were obtained by the impregnation method. The article revealed that the optimal loading amount of Fe2O3 on Ce0.67Zr0.33 O2-Al2O3 in our experimental condition for catalytic combustion of methane was 8% （ mass fraction）. The prepared catalysts were characterized by BET, TPR, XRD analyses, and their catalytic activity was investigated after being calcined at 873 K and after being aged in water gas at 1273 K. When the loading amount of Fe203 was 8% （ mass fraction）, the catalyst held the highest activity, and the best temperature speciality and thermal stability. The complete-conversion temperature of methane for fresh and aged sample was 788 and 838 K, respectively. The range between the light-off temperature and the complete-conversion temperature was only 15 K. The characterization results of XRD indicated that Fe2O3 was well dispersed on the Ce0.67Zr0.33O2-Al2O3 matrix. The results of BET and TPR were in good harmony with the catalytic activity results.     

High thermal stable gold catalyst supported on La2O3 doped Fe2O3 for low-temperature CO oxidation

La2O3 doped Fe2O3 support was prepared by co-precipitation method,and gold was loaded by deposition-precipitation.Thermal stability of gold catalyst was enhanced considerably by La2O3 doping.Even when calcined at 500 oC for 12 h,the catalyst doped with La2O3 could convert 90% of CO at 28.9 oC,while the catalyst without La2O3 doping achieved 90% CO conversion at 43.5 oC.Characterization techniques,such as N2 adsorption-desorption,X-ray diffraction(XRD),transmission electron microscopic(TEM) and thermogravime...     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3:Eu3+ phosphor

The Gd2O2CO3:Eu3 with type-II structure phosphor was successfully synthesized via flux method at 400℃ and their photoluminescence properties in vacuum ultraviolet (VUV) region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO32- host absorption and charge transfer (CT) of Gd3 -O2- were observed for Gd2O2CO3:Eu3 . Under 172 nm excitation, Gd2O2CO3:Eu3 exhibited strong red emission with good color purity, indicating Eu3 ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3:Eu3 was (x=0.652, y=0.345). The photoluminescence quenching concentration of Eu3 excited by 172 nm for Gd2O2CO3:Eu3 was about 5%. Gd2O2CO3:Eu3 would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

转炉喷吹CO2+O2混合气体基础研究

通过对转炉喷吹CO_2+O_2混合气体的热力学分析,结合实验室模拟转炉吹炼末期喷吹CO_2+O_2实验结果,探讨了在顶吹转炉中应用CO_2+O_2进行脱碳抑氧的可行性。得出结论,混合气体中CO_2比例增大,碳氧积降低,枪位对碳氧积的影响减弱,但回磷量增加,当CO_2比例增大到CO_2:O_2=1:1时,顶吹转炉碳氧积可控制在0.23×10-6~0.25×10-6,平均回磷量0.001%,混合气体中CO_2最大理论比例可增加到79.1%。     

新型CeO2-Fe2O3联合催化剂用于催化CO还原NO

采用3种不同的方法合成新型的以Fe₂O₃颗粒为载体的Ce-Fe复合氧化物催化剂,探究不同制备方式的复合氧化物催化剂的催化CO还原NO性能,并通过X射线衍射(XRD)、拉曼光谱(Raman)、氢气-程序升温还原(H2-TPR)、X射线光电子能谱(XPS)表征来对催化剂进行探究。结果证明Ce-Fe复合氧化物具有较高的催化活性,硝酸水热法Ce-Fe复合氧化物在900℃时脱硝率可达到99%以上。XRD中显示硝酸水热样品中CeO₂峰向高角度偏移,并且晶格常数变小。Raman结果说明硝酸水热样品CeO₂的振动峰向左大幅度偏移,结合XRD说明硝酸水热法可以形成Ce-O-Fe固溶体。H2-TPR说明氧化还原性:硝酸水热法>硝酸浸渍法>普通浸渍法。XPS结果说明硝酸水热法形成的Ce-O-Fe固溶体可以促进Fe³⁺向Fe²⁺、晶格氧向吸附氧的转换,这体现出复合催化剂Ce、Fe之间的联合作用。在整个反应过程中Fe₂O₃作为载体可以提供大量晶格氧,Ce-O-Fe固溶体的存在决定了复合催化剂的高催化活性。     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

CO2+O2地浸采铀强化浸出试验研究

新疆蒙其古尔铀矿床CO2+O2地浸采铀工艺中,铀浓度与HCO3-呈显著的正相关关系,但经过浸出初期后,提高CO2加入量不能有效提升体系HCO3-浓度,而对多数地浸单元的矿化条件而言,HCO3-浓度也尚未达最佳浸出需求。为此在该矿床某采区,采用补加碳酸氢铵和提高CO2加入量相配合的工艺,开展了强化浸出试验。结果表明,强化浸出效果显著,该采区浸出液中HCO3-从850 mg/L提升至1 200 mg/L,单孔铀浓度提升1.73~44.33 mg/L,集合样铀浓度提升8 mg/L。将pH调控在6.2~6.3和降低O2加入量稳定SO42-浓度,能避免强化浸出过程中发生碳酸钙和硫酸钙的沉淀,抽、注流量也并未受到影响。该强化浸出技术在多采区应用取得了良好的浸出效果和经济效益,是对该矿床CO2+O2浸出工艺的进一步优化。     

Catalytic Decomposition of CFC-12 over Solid Superacid Mo2O3/ZrO2

Catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor and oxygen was studied over a series of solid superacids, Mo2O3/ZrO2, that had different ZrO2 content by using a fixed-bed reactor. CO2 and CClF3 were the main products and no CO was detected as by-product. The decomposition activity of solid superacid largely depended on the content of ZrO2 and the calcination temperatures of Mo2O3/ZrO2. The optimal calcination temperature and content of ZrO2 for preparing Mo2O3/ZrO2 with the highest activity for catalytic decomposition of CFC-12 were 450°C and 20–40% by weight, respectively. Adopting a low concentration of oxygen and CFC-12 together with a high concentration of water vapor was preferable for having the high conversion efficiency of CFC-12 and the selectivity for CO2. The catalytic activity of Mo2O3/ZrO2 remained steady for 100?h in continuous operation.     

ICP-AES法测定锆英砂、电熔脱硅锆中Fe_2O_3、Al_2O_3、TiO_2、Cr_2O_3的质量分数

为测定锆英砂、电熔脱硅锆中Fe_2O_3、Al_2O_3、TiO_2、Cr_2O_3的含量,研究了用无水碳酸钠、无水碳酸钾、四硼酸钠混合熔剂熔融试样,在一定酸度下,用锫基体打底绘制工作曲线,将溶液雾化导入ICP,同时测定Fe_2O_3,Al_2O_3,TiO_2,Cr_2O_3发射光强度,计算各元素的质量分数。经实践该方法可操作性强,测量精确,可及时指导生产。