纳米TiO2催化燃烧固硫的实验研究

通过纳米TiO2催化CaO燃烧后粉煤灰的成分分析和燃烧烟气中SO2含量的测定确定固硫效果,探讨了纳米TiO2添加量、Ca/S摩尔比、不同条件制备的纳米TiO2及燃烧温度对分析纯CaO固硫的影响,比较了纳米TiO2对不同煤种以及不同钙基固硫剂的固硫效果,并对反应产物进行了X射线衍射和扫描电镜分析.结果表明,纳米TiO2与CaO共同作用时,纳米TiO2最佳的添加量为8%;在Ca/S摩尔比为2、燃烧温度为850℃时纳米TiO2催化分析纯和工业纯CaO固硫效率达87.8%和60.3%,比不添加纳米TiO2时增加13.4%和29.6%.纳米TiO2对不同煤种燃烧时CaO固硫有较好地催化作用,能够促进SO2转化成SO3的本征反应,同时增加煤灰的孔尺寸,促进二氧化硫的扩散从而提高CaO的固硫效果.     

纳米TiO2催化燃烧固硫的实验研究

通过纳米TiO₂催化CaO燃烧后粉煤灰的成分分析和燃烧烟气中SO₂含量的测定确定固硫效果,探讨了纳米TiO₂添加量、Ca/S摩尔比、不同条件制备的纳米TiO₂及燃烧温度对分析纯CaO固硫的影响,比较了纳米TiO₂对不同煤种以及不同钙基固硫剂的固硫效果,并对反应产物进行了X射线衍射和扫描电镜分析.结果表明,纳米TiO₂与CaO共同作用时,纳米TiO₂最佳的添加量为8%;在Ca/S摩尔比为2、燃烧温度为850℃时纳米TiO₂催化分析纯和工业纯CaO固硫效率达87.8%和60.3%,比不添加纳米TiO₂时增加13.4%和29.6%.纳米TiO₂对不同煤种燃烧时CaO固硫有较好地催化作用,能够促进SO₂转化成SO₃的本征反应,同时增加煤灰的孔尺寸,促进二氧化硫的扩散从而提高CaO的固硫效果.     

添加剂CeO_2对煤粉燃烧中钙基固硫的影响

针对内蒙古某火电厂用煤,以CaCO3为固硫剂,CeO2为固硫添加剂,进行了箱式电阻炉定温固硫实验,分析了温度、钙硫比、添加剂CeO2对燃煤固硫率的影响;热重法分析了固硫添加剂CeO2对煤炭燃烧性能的影响。结果表明:加入CeO2低温下(850℃、950℃)促进了燃煤固硫,提高了燃煤固硫率,而在高温下(1 050℃),催化作用导致固硫剂表面孔隙迅速堵塞,降低产物层扩散控制阶段反应速率,抑制了固硫过程的进行;CeO2催化了煤炭挥发份和固定碳的燃烧,降低了固硫煤着火点温度和燃尽温度,改善了煤的燃烧性能;揭示了添加剂CeO2催化固硫和催化燃烧的作用机理。     

添加剂影响CaO固硫反应活性的动力学分析

采用热分析法研究了Al₂O₃、Fe₂O₃和MnCO₃作为添加剂对CaO固硫反应过程的影响,用等效粒子模型对固硫反应过程进行表征,求得了其固硫反应动力学参数.结果表明:MnCO₃与Fe₂O₃对CaO固硫反应的作用机理相同,能提高固硫反应速率常数、产物层有效扩散系数和钙的转化率.通过计算等动力学温度、活化能大小可以判断添加剂对固硫反应活性影响的趋势,但不能准确衡量添加剂对固硫反应活性的贡献;对应温度下的反应速率常数和产物层有效扩散系数更能准确反映添加剂对固硫反应的影响大小.非化学计量金属氧化物通过高温下氧离子、金属离子较强的扩散特性来催化固硫表面化学反应和促进产物层扩散反应.根据不同添加剂的作用机理和对固硫反应的不同控制阶段的影响规律,针对添加剂发挥作用的温度特性和化学反应计量关系复合掺入添加剂,可进一步提高固硫剂转化率.     

煤粉固硫燃烧的动力学研究

采用新汶、阳泉原煤作为实验用煤,选择Ca（OH）2作为主固硫剂,考察了Ca／S的变化对燃煤固硫燃烧特性以及动力学参数的影响,采用碳酸盐、氯化物和氢氧化物3大系列化学试剂作为添加剂,在Ca／S为1.5的条件下,考察了它们对Ca（OH）2固硫能力的影响,以及固硫煤粉的燃烧特性和动力学参数的变化,实验表明：1）碳酸钾添加剂的助固硫作用明显,将固硫率提高了14％左右;2）固硫剂Ca（OH）2的加入使Arrhenius曲线斜率增大,明显提高了燃烧反应的活化能;3）随着Ca／S的增加,原煤的着火点和结束点、活化能有逐渐增大的趋势;4）添加剂对原煤燃烧特性的影响并不显著,但对活化能的影响却十分明显,添加剂的加入有效地降低了燃烧反应的活化能。     

固硫煤和普通煤对SO2污染和健康危害的对比研究

探讨固硫煤与普通煤燃烧造成室内SO2污染及对健康的危害作用.将家兔分别喂养在燃烧固硫煤、普通煤和不烧煤的环境中连续观察90d,每天监测室内环境中SO2、CO的浓度;实验各时期测定家兔LYS含量和血清中SOD、GSH-PX、SA浓度.结果:固硫煤组SO224h平均浓度(2.68mg/m3)明显低于普通煤组(13.04mg/m3),但CO水平两组间无明显差异.实验90d后与实验前的GSH-PX值的差值比较,普通煤＞空白对照组＞固硫煤组,普通煤和固硫煤组间的差别有显著性意义(p＜0.05);SOD、SA、LYS值在实验期有所变化,但各组间的差别无显著性意义 (p＞0.05).结论:提示燃煤煤烟中SO2能影响生物体内SOD、GSH-PX、LYS、SA的浓度变化,燃烧固硫煤能明显降低SO2的污染,故使用固硫煤可减少燃煤煤烟对健康的危害.     

化学链燃烧中钙基载氧体CaSO4再生的氧化反应机理

在热重和红外联用进行等温实验的基础上,探讨了氧体积分数为10%、20%,970～1150℃温度范围内化学链燃烧过程中钙基载氧体再生(CaS)的氧化特性.结果显示,CaS氧化的直接产物主要为CaSO4,只有在诱导期生成极少量CaO和SO2;但CaSO4与CaS还可进一步反应,生成更多CaO和SO2.通过对氧气浓度和温度的实验条件改变,研究了CaSO4的转化率、转化速率,并辅以SO2析出速率分析,获得了CaSO4相对于CaO的瞬时选择性、CaSO4的收率和反应选择率.结果表明,钙基载氧体CaSO4再生过程氧化反应的适宜条件为温度970～1000℃以及较高的氧气气氛,这不仅可以抑制SO2的排放量从而得到较高的反应选择率,同时反应过程也具有较高的转化速率.     

型煤催化固硫的研究

本试验发现Fe_2O_3对型煤固硫有催化作用,当型煤中Fe_2O_3含量在6‰时,固硫率最高,比在同等条件下不加Fe_2O_3时约增加10%左右。在温度小于500℃时,固硫率和Fe_2O_3关系曲线只出现极大值,大于500℃时,则同时出现极大极小值。它的催化固硫动力学行为比较复杂,温度小于500℃,Fe_2O_3含量小于6‰时,它起催化作用;Fe_2O_3含量大于6‰时,它与CaO形成固熔体,因而影响了活性。型煤催化固硫率的高低主要取决于温度低于470℃这一阶段,提高型煤固硫率的关键是要求型煤在500℃之前升温速度不能太快,为此可设计一型煤预热装置,此装置温度控制在470℃以下,型煤在装置中停留时间不超过半小时。Fe_2O_3的加入主要加快了CaO+SO_2→CaSO_3这一主反应的速度,并对硫的最后形态CaSO_4起一定稳定作用。     

Pd/CeZr/TiO2/Al2O3蜂窝状金属丝网催化剂选择催化还原NOX

采用溶胶-凝胶法和浸渍法制备了Pd/CeZr/TiO2Al2O3蜂窝状金属丝网催化剂,并将其应用于在富氧条件下以丙烯选择催化还原NOx的研究.利用扫描电镜(SEM)分析了钛酸四丁酯的含量以及涂敷次数对TiO2涂层的影响,系统地考察了Pd含量、氧气浓度和空速对蜂窝状金属丝网催化剂催化性能的影响.实验结果表明,采用钛酸四丁酯的含量为20.0%的溶胶,涂敷2次,可以在金属丝网载体上氧化铝涂层表面获得均匀、无皲裂的TiO2涂层;Pd含量在0.23%～1.06%的范围内, NOx的转化率随Pd含量的增加而减小, Pd含量为0.23%时, NOx表现最高的NOx转化率;反应气体中氧气浓度从1.5%增加到6.0%, NOx的转化率随氧气浓度的增加而增大,当氧气浓度高于6.0%, NOx的转化率则随氧气浓度的增加而迅速减小; NOx的转化率随着空速的增加而降低,在高温条件下空速对转化率的影响要大于在低温条件下.     

水处理固体废物用作燃煤锅炉炉内脱硫的机理与实验

对水处理固体废物用作燃煤锅炉炉内脱硫添加剂的机理与实验研究表明 ,水处理固体废物用作炉内燃煤脱硫添加剂时生成一些可以有效地催化脱硫反应 ,以及减缓高温下 Ca SO4分解速度 ,使燃煤脱硫过程的最佳脱硫温度更加接近煤燃烧温度 ,提高燃煤脱硫效率的物质 ,如 Fe2 O3、Si O2 、Al2 O3、K+、Na+等 ;并使得脱硫反应温度更加接近煤燃烧温度 ;当脱硫反应温度在 870～ 92 0℃、脱硫剂与水处理固体废物的重量比为 1∶ 1、Ca/S=2 .0等条件满足时 ,可以得到燃煤脱硫的最佳效果     

Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier

Chemical looping combustion （CLC） of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier （OC） was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi （LZ） bituminous coal, was performed in a thermogravimetric analyzer （TGA）-Fourier transform infrared （FT-IR） spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFeaO40C was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn304 or Fe203, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe304 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4.     

纳米TiO2添加剂对DMDF发动机大负荷燃烧及PM排放影响的试验研究

在一台电控增压中冷四缸柴油机的进气道上加装一套电控喷射装置,使其运行柴油/甲醇双燃料(DMDF)模式.研究了甲醇中Ti O_2添加剂的添加量及同一添加剂添加量在不同甲醇分散系喷射量时对发动机大负荷工况的燃烧和颗粒物(PM)排放的影响.结果表明,在甲醇中添加适量(30和100 mg·kg~(-1))的纳米Ti O_2能够使爆发压力升高,对燃烧有一定的促进作用,但添加过量(100 mg·kg~(-1))会对燃烧产生不利影响.加入纳米Ti O_2后,干炭烟烟度排放和积聚态颗粒数明显降低,在添加剂添加量为1000 mg·kg~(-1)时,最大降幅分别达到26.8%和29.4%,而核态颗粒物排放变化不大.在相同添加剂添加量下,增加甲醇分散系替代率R_m会使放热始点后移,放热更加集中,爆发压力增大,干炭烟烟度和颗粒物排放均大幅度降低.在添加剂添加量为100 mg·kg~(-1)时,与R_m=10%相比,R_m=40%时爆发压力增加0.94 MPa,放热率峰值增加53.5%,烟度、核态颗粒数、积聚态颗粒数和颗粒物总数的降幅分别达66.9%、42.3%、67.0%和58.0%.     

The oxycoal process with cryogenic oxygen supply

Due to its large reserves, coal is expected to continue to play an important role in the future. However, specific and absolute CO₂ emissions are among the highest when burning coal for power generation. Therefore, the capture of CO₂ from power plants may contribute significantly in reducing global CO₂ emissions. This review deals with the oxyfuel process, where pure oxygen is used for burning coal, resulting in a flue gas with high CO₂ concentrations. After further conditioning, the highly concentrated CO₂ is compressed and transported in the liquid state to, for example, geological storages. The enormous oxygen demand is generated in an air-separation unit by a cryogenic process, which is the only available state-of-the-art technology. The generation of oxygen and the purification and liquefaction of the CO₂-enriched flue gas consumes significant auxiliary power. Therefore, the overall net efficiency is expected to be lowered by 8 to 12 percentage points, corresponding to a 21 to 36% increase in fuel consumption. Oxygen combustion is associated with higher temperatures compared with conventional air combustion. Both the fuel properties as well as limitations of steam and metal temperatures of the various heat exchanger sections of the steam generator require a moderation of the temperatures during combustion and in the subsequent heat-transfer sections. This is done by means of flue gas recirculation. The interdependencies among fuel properties, the amount and the temperature of the recycled flue gas, and the resulting oxygen concentration in the combustion atmosphere are investigated. Expected effects of the modified flue gas composition in comparison with the air-fired case are studied theoretically and experimentally. The different atmosphere resulting from oxygen-fired combustion gives rise to various questions related to firing, in particular, with regard to the combustion mechanism, pollutant reduction, the risk of corrosion, and the properties of the fly ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO₂ concentration was found, as expected. However, the H₂S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO₂ and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO₂ liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO₂ capture rate. Furthermore, the impurity of the liquefied CO₂ is affected as well. Since the requirements on the liquid CO₂ with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.     

成都市PM10中碳质气溶胶长期来源特点

大气颗粒物中包含多种组分的气溶胶,其中碳质气溶胶由于对人体健康、能见度有较大影响,已受到越来越多的关注.为研究碳质气溶胶的长期变化规律,采集了成都市2009—2013年的PM₁₀样品,对其中所含的无机元素、水溶性离子及碳组分分别进行测定,并使用“PMF（正定矩阵因子分解法）-比值”模型分别对PM₁₀和所含的碳质气溶胶的来源进行分析.结果表明,1月、2月、5月和12月的碳质气溶胶浓度较高,其中1月、2月和12月的OC/EC（有机碳与元素碳质量浓度之比）较高,并且PMF-比值模型计算结果也显示冬季SOC增多,表明冬季可能有更多的二次有机碳（SOC）生成;5月的char-EC/soot-EC（二者质量浓度之比,其中char-EC=EC1-OP,soot-EC=EC2+EC3,它们可更好地区分源类）较高,K含量也较高,表明可能有更多的生物质燃烧排放.PM₁₀解析共发现6类源,依次为地壳扬尘（26.5%）、二次硫酸盐（25.1%）、燃煤&生物质燃烧混合源（17.3%）、二次硝酸盐&二次有机碳混合源（12.3%）、机动车源（11.8%）和水泥尘源（7.0%）;碳质气溶胶解析发现,OC主要来源依次为机动车源（38.2%）、燃煤&生物质燃烧混合源（33.1%）和二次有机碳（25.3%）,char-EC的主要来源是燃煤&生物质燃烧混合源和机动车源,分别占50.5%和45.4%,soot-EC则主要受机动车影响（达73.2%）.研究显示,成都市PM₁₀主要来自于地壳扬尘、二次生成和燃煤&生物质燃烧,而碳质气溶胶主要来自于机动车、燃煤&生物质燃烧.      

流化床中RDF焚烧时CO、SO2和HCl的生成

在非均匀布风流化床中进行了垃圾衍生燃料(RDF)与煤的混烧试验，测量了H2O、CO、CO2、NO、N2O、HCl、SO2等污染物质的排放特性．结果表明与单纯燃烧RDF相比，混烧时的CO生成量大大下降；SO2生成浓度较低，而HCl的生成量比单纯烧煤时明显增加．     

上转换发光剂掺杂纳米TiO2的制备及可见光降解乙基紫的研究

合成了一种新型含有稀土金属Er的上转换发光剂40CdF₂·60BaF₂·1.6Er₂O₃,此上转换发光剂在488 nm可见光的激发下,产生了5个波长均小于387 nm的上转换紫外光发射峰.采用超声波分散的方法制备出了上转换发光剂掺杂的纳米TiO₂可见光光催化剂.利用X-射线衍射(XRD)及透射电镜(TEM)对催化剂进行了表征.以乙基紫染料为研究对象,研究了在(三基色灯下发出的)可见光的照射下该可见光光催化剂的催化降解性能,并与未掺杂的纳米TiO₂粉末的催化性能进行了对比.结果表明,作为掺杂成分的上转换发光剂可有效地将可见光转化为紫外光并被纳米TiO₂粉末吸收利用,在可见光照射12.0 h后乙基紫降解率达到了99.68%,大大高于未掺杂纳米TiO2时的降解率.     

Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst

CeO2–TiO2composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5–WO3/CeO2–TiO2catalysts for the selective catalytic reduction（SCR） of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV–Vis,Raman and XPS techniques. The results showed that the catalytic activity of V2O5–WO3/TiO2 was greatly enhanced by Ce doping（molar ratio of Ce/Ti = 1/10） in the TiO2 support.The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning.     

纳米TiO2对底泥中汞释放及活化的影响

为了研究纳米TiO2对底泥汞的释放及活化的影响,采用模拟淹水实验,分析纳米TiO2对底泥和上覆水中总汞和甲基汞浓度的影响,并结合底泥中各形态汞的变化情况探讨纳米TiO2对汞的迁移转化的影响.结果表明,纳米TiO2可促进底泥中汞的释放,导致更多的汞释放到水中,与对照相比,4g·kg-1纳米TiO2导致上覆水中总汞浓度最高时上升91.32%,最终土壤汞的释放量增加约10%,主要原因是纳米TiO2可促进氧化态汞的溶解,这可能会提高水体汞污染的风险.此外,在本实验条件下,短期内纳米TiO2可能降低了底泥甲基汞的形成和释放,但长期淹水后没有明显的影响.总体来看,纳米TiO2对底泥汞释放和转化的影响随浓度升高而增大.因此,随着底泥或土壤中纳米TiO2含量的升高,其对汞的地球化学循环过程的影响可能加剧.     

Density functional and experimental study of NO/O2 on zigzag char

In this paper, quantum chemistry computation (density functional theory) of multi-air-staged combustion was investigated in combination with experiment. It was found that the presence of oxygen in the combustion environment has a great influence on the surface chemistry of coal char. In the reaction pathway, the ring-opening reaction happens first, and is followed by NO adsorption. Afterwards, the ring-closure reaction takes place, leaving the nitrogen atom trapped in the inner char molecule. This reaction route effectively inhibits NO formation and achieves the aim of controlling NO emissions. In the staged combustion experiments, the consumption of O₂/NO was accompanied by an increase in the CO₂ concentration. The quantum chemistry computation successfully interprets the recent experimental trends displayed in multi-air-staged combustion.