O_2/CO_2气氛下煤种对燃煤PM_(2.5)形成的影响

采用管式炉和荷电低压撞击器(electrical low pressure-impactor,ELPI)研究了4种煤粉在O2/CO2条件下燃烧后生成的PM2.5排放特性,并对空气和O2/CO2气氛下PM2.5的排放特性进行了比较。结果表明:不同煤粉在O2/CO2气氛下燃烧后,所产生的PM2.5质量浓度均呈双峰分布,峰值分别在0.1和2μm左右;S在亚微米颗粒上明显富集,而在超微米颗粒上含量相对较少;K和Na在亚微米颗粒上含量比在超微米颗粒上高一些;Si和Ca在亚微米颗粒上含量相对较少,而在超微米颗粒上含量相对较多;Fe在亚微米和超微米颗粒上含量相当。分析认为,不同煤粉中组分形式和含量的不同,影响了煤粉燃烧后PM2.5形成的过程,造成PM2.5排放特性的不同。从PM2.5的粒径分布、元素分布和形貌分析可知,和空气气氛相比,O2/CO2气氛不影响PM2.5的生成机制,但影响其粒径分布。     

O2/CO2气氛下痕量元素的赋存和迁移特性

在管式炉中进行徐州烟煤的燃烧实验。通过改变燃烧气氛,用电感耦合质谱分析仪(inductively coupled plasma- mass spectrometry,ICP-MS)研究O2/CO2燃烧方式下O2含量及温度对煤中As、Cr、Pb等痕量元素赋存、迁移特性的影响,并在相同的氧浓度下研究CO2浓度对痕量元素排放的影响。结果表明：痕量元素及其化合物的熔点、沸点等物理性质对元素挥发影响很大;较之常规燃烧方式,O2含量的变化并没有改变As、Cr、Pb、Ni等痕量元素在底灰中的含量随温度升高而降低的总体规律;随着燃烧气氛中O2含量的升高,Cr、Ni在底灰中的含量有所降低,而As、Pb在底灰中明显富集;随着温度升高,燃烧气氛对As在底灰中富集的影响逐渐减弱;此外,在相同的O2含量下,CO2含量越高,As在底灰中的含量越低,因为高浓度的CO2在一定程度上抑制了更易挥发的次氧化物或单质的生成。     

商业V2O5-WO3/TiO2催化剂SCR脱硝过程中PM2.5的排放特性及影响因素研究

针对V2O5-WO3/Ti O2商用催化剂,采用电称低压冲击器(ELPI)、PM10/PM2.5采样器、X-射线衍射(XRD)、场发射扫描电镜-能谱分析(FSEM-EDX)等对SCR烟气脱硝中形成的细颗粒粒径分布、形貌、元素及物相组成进行了测试分析,并研究了烟气组分及反应条件对SCR脱硝系统出口细颗粒物性的影响。结果表明,SCR脱硝过程中会形成不少亚微米级颗粒,主要成分为硫酸铵以及硫酸氢氨,晶型呈块状。细颗粒生成量随反应温度的升高和NH3/NO摩尔比的增加而增加,在脱硝效率较高时,颗粒物形成量也趋于增多;烟气中SO2、H2O和O2浓度的增加均会导致细颗粒物形成量的增加。导致细颗粒物产生的主要原因可归结于催化剂的活性组分对SO2的氧化以及SCR脱硝反应中NH3的逃逸。     

黄铁矿燃烧时亚微米颗粒物的生成特性

将纯黄铁矿在O2/N2与O2/CO2条件下进行沉降炉燃烧实验,采用低压撞击器(dekati low pressure impactor,DLPI)收集燃烧生成的亚微米颗粒物(PM1),并获得质量粒径分布。利用X射线荧光能谱仪(X-ray fluorescence,XRF)和配备了能谱仪的环境扫描电子显微镜(scanning electron microscope equipped with energy dispersive X-ray spectrometer,SEM- EDS)对PM1的物化特性进行深入表征,研究黄铁矿在不同燃烧气氛下所生成的PM1的质量粒径分布、浓度、元素组成、形貌和成分特性。研究结果表明,黄铁矿燃烧对PM1的生成具有重要贡献。相同O2浓度时,相比于O2/N2燃烧条件,O2/CO2燃烧条件下黄铁矿燃烧过程中PM1的生成量与峰值粒径均减小。在O2/N2或O2/CO2燃烧条件下,随着O2浓度的增加,PM1的生成量与峰值粒径呈增大趋势。PM1的组成主要以S元素为主。在O2/N2燃烧条件下,O2浓度对不同含S化合物的分布具有重要影响,在低O2浓度下,PM1中的S元素主要以S单质的形式存在,而在高O2浓度下,PM1中的S元素主要以硫酸或硫酸盐的形式存在。     

O2/CO2气氛煤粉燃烧特性试验研究

O2/CO2燃烧技术是一种可分离回收CO2的新型燃烧技术，其燃烧机理与常规空气气氛燃烧存在着较大的差异。为此，该文在热重分析仪上进行了模拟空气气氛及不同O2浓度(j(O2)=21%、30%、40%、80%)的O2/CO2气氛下3种不同品质煤粉(龙岩无烟煤、贵州烟煤、元宝山褐煤)的燃烧特性试验，确定了3种煤粉的燃烧特征参数及综合燃烧性能指数。试验结果表明，O2/CO2气氛下煤粉的燃烧分布曲线与O2/N2气氛下有明显不同，相同O2浓度的条件下，O2/CO2气氛下煤粉燃烧速率低，燃尽时间长。在O2/CO2气氛下随着O2浓度的增加，燃烧DTG曲线向低温区偏移，着火温度及燃尽温度降低，燃尽时间缩短，煤粉综合燃烧特性指数增大，表明提高O2浓度可改善O2/CO2气氛下煤粉的燃烧特性。     

O2/CO2气氛下碳酸钙颗粒分解特性模拟研究

结合传质传热和化学动力学原理,首先描述了碳酸钙颗粒在O2/CO2气氛下煅烧情况,模拟结果与实验结果比较吻合,在此基础上模拟分析了碳酸钙颗粒在不同CO2浓度下的转化率和比表面积、孔隙率变化情况。     

加压O2/CO2气氛下煤粉着火特性的实验研究

研究了加压O2/CO2气氛下压力、氧浓度、煤焦结构和煤种等因素对大同烟煤和神火无烟煤着火特性的影响,并采用可燃性指数和综合燃烧特性指数评价不同压力下煤的着火和燃烧特性。加压热重实验结果表明,压力从0.1MPa升高至2MPa,着火温度先降低后升高,在1MPa下着火温度最低,燃烧特性最佳。在常压和加压条件下,提高氧浓度均可加快煤的着火。在常压下,随氧浓度提高,着火温度下降的幅度较小,但在加压时,较高氧浓度会改变着火模式,着火温度降低明显。扫描电镜分析显示加压促进煤在脱挥发分过程的破碎,提高碳氧反应速率,降低着火温度。煤的着火与煤种有关,挥发分含量较高的煤,其着火越容易。结果反映了加压富氧燃烧比常压富氧燃烧更有优越性。     

负载型K2CO3/Al2O3吸收剂鼓泡床吸收CO2特性及数值模拟

利用负载型K2CO3/Al2O3吸收剂吸收燃煤电厂烟气中的CO2是一种较好的CO2减排方法。在小型鼓泡床试验台上对K2CO3/Al2O3吸收剂吸收CO2的特性进行了研究。结果表明,K2CO3/Al2O3吸收剂具有良好的CO2吸收性能,吸收剂转化率超过70%,在反应开始3min内CO2的脱除率达到了100%。基于K-L鼓泡床两相模型建立了负载型K2CO3/Al2O3吸收剂鼓泡床吸收CO2的数学模型,化学反应源项采用了颗粒缩核模型。CO2脱除率和K2CO3/Al2O3吸收剂转化率的模拟值与试验值较吻合,同时模型给出反应气体在气泡相和乳化相中的浓度分布,揭示了反应器某些细节特征。利用所建立的模型对试验系统进行了分析计算,结果表明,增加CO2浓度不利于提高CO2脱除率。增加流化数,气泡速度和直径均迅速增大,CO2脱除率迅速降低。增加床料量有利于提高CO2脱除率。模型的预测结果具备一定的合理性和准确性,为开展相应的试验研究和系统设计提供了基础数据。     

Ni0.6Zn0.4Fe2O4铁氧体纳米晶与微米晶300MHz～2GHz的磁导率比较

用水热法制备了平均晶粒尺寸为40 nm的Ni0.6Zn0.4Fe2O4铁氧体八面体颗粒,同时采用溶胶-凝胶高温烧结法合成Ni0.6Zn0.4Fe2O4微米晶颗粒。用矢量网络分析仪测试了铁氧体/石蜡混合材料在300MHz~2GHz频段的复磁导率和复介电常数。实验结果表明Ni0.6Zn0.4Fe2O4铁氧体纳米晶粒样品与微米晶样品相比具有更高的磁导率(实部r在3.3～1.65之间,磁导率虚部r在1.1左右)、更大的磁损耗以及更优异的微波吸收特性。     

O2/CO2和O2/N2气氛下不同煤种的热解与燃烧试验研究

采用热重-质谱联用仪分别研究了3种煤在O2/N2和O2/CO2气氛下的热解和燃烧特性.结果表明,与N2气氛相比,CO2气氛下煤粉的热解过程可分为水分的蒸发、挥发分的释放以及较高温度下煤焦与CO2的气化反应;随燃烧气氛中氧浓度的增加,煤粉的TG-DTG曲线移向低温区,着火温度和燃尽温度降低,煤粉综合燃烧特性指数增大;在相同的燃烧气氛及氧浓度下,PRB次烟煤的着火温度和燃尽温度明显低于Illinois烟煤和Utah烟煤.     

氢氧等离子体合成过氧化氢过程的能效研究

为提高氢氧等离子体合成H2O2技术的能量效率,通过分析放电过程的反应器能效及电源能量注入效率,确定了影响合成总能效的主要因素。考察了反应器电极间距、电源放电频率及注入功率对反应器能效和电源能量注入效率的影响。发现减小电极间距、提高放电频率和注入功率有利于提高反应器能效,但不利于提高电源能量注入效率。本研究中可以得到150 gH2O2/kWh的反应器能效,但由于较低的电源能量注入效率,致使合成H2O2的总能效不超过9 gH2O2/kWh。因此,提高等离子体法合成H2O2过程的总能效,不仅需要设计高能效的等离子体反应器,还需为反应器负载开发适配的电源,而后者是提升该技术能量效率的关键。     

Electron-Ion Transport in ZrO2-Y2O3-CeO2 Ceramics

Simultaneous conduction of oxide ions and electrons in solid ceramic systems provides the capability for oxygen transport under a concentration gradient without the need for an externally applied electric field. In the present study, ionic transference numbers have been measured in the ZrO₂-5.8%Y₂O₃-10%CeO₂ system by open circuit Emf measurements involving different metal/metal oxide electrodes. In order to correlate the ionic transference number with grain size, high-density ceramic discs of different grain sizes (50 nm–5 m) were prepared by sintering pressed powders at various temperatures and times. Hydrothermal synthesis was used to prepare nanocrystalline powders of the above material with uniform crystallite size (10 nm) and chemistry. Emf measurements on the samples suggested both ionic and electronic transport, the ionic transference number decreasing with increase in the grain size. This observation was attributed to an increase in the amount of continuous crystalline grain boundary phase in the ceramics as the grain size increased. The presence of crystalline silicate and zirconate phases in the grain boundary region was confirmed by electron microscopic imaging combined with microanalysis. In the large grain (5 m) ceramics, the ionic transference number decreased linearly with temperature. As the grain size decreased, a maximum occurred in the ionic transference number vs. temperature curve. This maximum became more pronounced at smaller grain sizes. Better grain-grain contact and the doping effect of trivalent Ce in the grain boundary core are proposed to explain this observation.     

RuO_2-IrO_2-TiO_2析氧催化剂的制备工艺

以Ti N、RuCl3和H2IrCl6为原料,用真空浸渍-热分解法制备了RuO2-IrO2-Ti O2,研究了煅烧温度和n(Ru+Ir)∶n(Ti)对产物的影响。XRD分析表明:Ti N在高温煅烧时氧化生成金红石型Ti O2,RuO2、IrO2和Ti O2以固溶体的形式存在。CV、阳极极化曲线和EIS测试表明:RuO2-IrO2-Ti O2的最佳煅烧温度为400℃,随着n(Ru+Ir)∶n(Ti)的提高,催化剂的活性增强;在相同电位下,RuO2-IrO2-Ti O2的电流密度大于IrO2,可用作固体聚合物电解质(SPE)水电解催化剂。     

富氧火焰原子吸收光谱法测定铅钙锡合金中的锡

采用富氧火焰 (Air—C2 H2 —O2 )原子吸收光谱法直接测定铅钙锡合金中 0 1%以上的锡。对仪器工作条件、测定体系酸度、共存离子干扰等作了研究。方法准确度高 ,结果重现性好     

Thermoelectricity of p-Fe2O3-SO3-SiO2-others and n-Fe2O3-SiO2-CuO-others

Thermoelectric minerals have been found at Loei Province, in the northeastern part of Thailand. Local mineral specimens were prepared in the powders and bulk solids form by crushing, calcination and annealing, pressure and sintering, cutting and polishing. Mineral samples were used to analyze the composition and phase, determine the thermoelectric property and efficiency, design and construct a thermoelectric generator. Chemical composition and phase identification of powder samples were analyzed by the x-ray fluorescence (XRF) and x-ray diffraction (XRD), respectively. XRF and XRD results indicated that the mineral samples comprised the SO₃-CaO-SiO₂-others, Fe₂O₃-SO₃-SiO₂-others, Fe₂O₃-SiO₂-others and Fe₂O₃-SiO₂-CuO-others. From the thermoelectric property and efficiency determinations, the p-SO₃-CaO-SiO₂-others, p-Fe₂O₃-SO₃-SiO₂-others, n-Fe₂O₃-SiO₂-others and n-Fe₂O₃-SiO₂-CuO-others bulks were found to exhibit the thermoelectric figure of merit in orders of 10^?14, 10^?11, 10^?14 and 10^?13 K^?1, respectively. A fabricated thermoelectric generator made from ten pairs of p-Fe₂O₃-SO₃-SiO₂-others and n-Fe₂O₃-SiO₂-CuO-others legs that can be provided the open circuit voltage and short circuit current up to 48.30 mV and 0.14 μA for a temperature difference of 39.80 K at room temperature, respectively. While the internal resistance decreased and reached a value of 665 kΩ.     

Mixed Hydroxide Precursors for La2Ti2O7 and Nd2Ti2O7 by Homogeneous Precipitation

Feasibility of formation of stoichiometric precursors of either M₂ (TiO)₂(C₂O₄)₅ 4H₂O (M = La and Nd) or coprecipitated hydroxides of M(OH)₃+TiO(OH)₂ was investigated by two solution routes at different pH values. Composition of precipitates obtained at pH = 7.0 by coprecipitation method starting from La or Nd nitrates and potassium titanyl oxalate corresponded to a physical mixture of La or Nd(C₂O₄)₃ 9.5H₂O and TiO(OH)₂7·H₂O which on thermal decomposition did not yield phase pure M₂Ti₂O₇. However, precipitation from La or Nd nitrates and titanium tertrachloride by urea hydrolysis yielded homogeneous mixture of hydroxides of La or Nd and Ti, which on pyrolysis at 950°C yielded phase pure La₂Ti₂O₇ and Nd₂Ti₂O₇. Use of potassium titanyl oxalate as precursor for Ti, led to selective precipitation of La or Nd oxalate even at pH as low as 0.1 leading to sequential precipitation of La or Nd oxalate followed by Ti hydroxide at pH = 3.0. The resultant precipitate on pyrolysis underwent typical solid-state reaction.     

pH-MnO_2电极电位与MnO_2活性

本文对用于电池的MnO_2进行电化学评价,测定不同产地锰矿的pH—电极电位关系,每个样品的模拟制作,锌—锰干电池并测定共放电容量,通过比较放电容量和MnO_2的电极电位,从而对MnO_2进行活性评价。     

过氧化氢钝化工艺的改进

传统的过氧化氢钝化工艺较难掌握，钝化条件比较苛刻，钝化效果一般，还容易出现一种褐色不明附着物。经过大量试验研究，对过氧化氢钝化工艺进行了改进，钝化效果明显提高。     

Large motors for zone 2 and division 2

The safety of people working in either in division 2 or zone 2 hazardous (classified) locations and the protection of the facility is a prime concern. Worldwide, local authorities having jurisdiction mandate the codes and/or standards necessary to assure safety and protection. Two parallel approaches, North American NEC/CEC and international IEC systems, address the requirements of equipment installed in these locations. While essentially equal, the two systems are not interchangeable, and it is the obligation of the purchaser to advice which code is appropriate for the installation. It is also the responsibility of the purchaser or user to satisfy requirements of the LAHJ. A quick summary is provided in the "Summary of NEC, CEC, and IEC Requirements." NEC/CEC codes allow the manufacturer design leeway in the safe construction of motors and generators. These machines have a documented history of successful, incident free, operation for over 100 years.The machines made to the IEC EX "n" standard have the same consideration for the occurrence of arcing or sparking and include supplementary requirements for design, construction, and validation testing. The machines designed for division 2 hazardous area meeting the North American requirements of NEC/CEC may not be sufficient to comply with the mandates of IEC-regulated zone 2 hazardous area use. The machines designed and authenticated per IEC 60079-15 are suited to meet all the requirements of NEC, CEC, and IEC for zone 2 use.