碱性氢氧化物消除NH4Cl积灰特性实验研究

通过模拟燃煤电厂中NH₄Cl氛围,研究NH₄Cl如何影响飞灰沉积引起受热面热流密度变化. 实验采用竖式炉系统模拟锅炉尾部烟道,油循环系统控制温度,探针收集积灰,实时监测探针内外表面温度,获得探针受热面热流密度,将NaOH,Mg(OH)₂,Ca(OH)₂作为脱除剂,研究3种碱性氢氧化物对烟气中NH₄Cl的脱除效果. 研究发现,NH₄Cl对灰分的黏附能力较弱,受热面热流密度降低主要由NH₄Cl析出形成的沉积层引起. 在3种脱除剂中,Ca(OH)₂能够改善探针顶部热流密度降低,将热流密度降低率缩小到3.61%;NaOH能够改善探针底部热流密度降低,将降低率缩小到6.46%;Mg(OH)₂虽然能够减少探针顶部热流密度降低,但会引起探针底部热流密度降低加剧.     

MoS2/硼掺杂石墨烯的电化学析氢和储锂性能

为了研发高效低成本的析氢反应(HER)电催化剂和高性能的电化学储锂电极材料,通过一步水热法制备MoS₂/硼掺杂石墨烯（MoS₂/BG）复合材料. 结果表明,少堆积MoS₂纳米片均匀地分散在硼掺杂石墨烯上,并具有较多的无序结构和扩大的层间距. 作为析氢反应电催化剂,MoS₂/BG复合材料表现出较高的电催化活性和较低的Tafel斜率（46.3 mV/dec）;作为电化学储锂电极材料,MoS₂/BG复合材料表现出优异的电化学储锂性能,可逆比容量为1 205 mA·h/g,并具有稳定的循环性能和显著增强的高倍率特性. MoS₂/BG复合材料电化学性能优异是由于硼掺杂改变石墨烯的电子性质和表面特性,以及无序结构较多的弱堆积MoS₂层均匀地分散在硼掺杂石墨烯表面,增加电催化析氢反应的活性位点和电化学储锂能力,降低电极反应的电子转移阻抗,增强电极反应的动力学性能.     

Temperature dependence on reaction of CaCO3 and SO2 in O2/CO2 coal combustion

The temperature dependence on the reaction of desulfurization reagent CaCO₃ and SO₂ in O₂/CO₂ coal combustion was investigated by thermogravimetric analysis, X-ray diffraction measurement and pore structure analysis. The results show that the conversion of the reaction of CaCO₃ and SO₂ in air is higher at 500–1 100 °C and lower at 1 200 °C compared with that in O₂/CO₂ atmosphere. The conversion can be increased by increasing the concentration of SO₂, which causes the inhibition of CaSO₄ decomposition and shifting of the reaction equilibrium toward the products. XRD analysis of the product shows that the reaction mechanism of CaCO₃ and SO₂ differs with temperature in O₂/CO₂ atmosphere, i.e. CaCO₃ directly reacts with SO₂ at 500 °C and CaO from CaCO₃ decomposition reacts with SO₂ at 1 000 °C. The pore analysis of the products indicates that the maximum specific surface area of the products accounts for the highest conversion at 1 100 °C in O₂/CO₂ atmosphere. The results reveal that the effect of the atmosphere on the conversion is temperature dependence.     

采用动网格技术的煤粉-玉米秸秆掺烧飞灰沉积数值模拟

为了研究煤粉和生物质掺烧形成飞灰的结渣特性,采用基于动网格技术的计算流体动力学（CFD）模型对煤粉-玉米秸秆掺烧积灰结渣实验（玉米秸秆掺比分别为0、5%和10%）进行数值模拟. 模拟过程中考虑灰渣导热系数和灰渣表面温度的变化,并将模拟结果和实验结果进行比较. 模拟结果表明：飞灰撞击质量流率随沉积进行而减小,这是因为沉积物引起的动网格变化影响探针附近流场;3种工况下飞灰在探针表面的最终沉积效率分别为75%、80%和87%,说明了玉米秸秆掺烧形成飞灰的易结渣倾向;灰渣实时形貌在动网格执行下得以实现. 在换热特性方面,灰渣表面温度和热流密度的模拟值和实验值较为接近;3种工况下0~100 min热流密度降低率分别为52.13%、46.96%和53.25%.     

Pr掺杂对V2O5-MoO3/TiO2催化剂NH3-SCR反应活性的影响

考察不同V₂O₅负载量、O₂体积分数、NO体积分数、SO₂体积分数、H₂O体积分数、n（NH₃）/n（NO）、空速和在线加热再生等因素对浸渍法制备的V₂O₅-WO₃/TiO₂催化剂低温NO转化率的影响.综合分析,选定V₂O₅最佳负载质量分数为3%,当反应温度为160℃时,NO转化率为93.7%.110~320℃时,N₂选择性大于98%,SO₂氧化率低于1.0%.NO转化率随O₂体积分数增加而明显上升,随入口NO体积分数增加而有不同程度下降,但NO_x去除量逐渐提高.n（NH₃）/n（NO）≤ 1时,催化剂最优活性约等于各自n（NH₃）/n（NO）,n（NH₃）/n（NO）>1对催化剂活性没有明显提升.增大空速,催化剂高活性温区变窄,活性呈现不同程度的下降.表征结果表明,在含有SO₂和H₂O的选择性催化还原法（selective catalytic reduction,SCR）反应后,催化剂比表面积和孔容减小,活性组分流失,且沉积了包含NH₄⁺和SO₄^2-的副反应产物.热再生过程中催化剂延缓硫酸铵盐分解,导致催化剂抗中毒能力变差,活性难以恢复.

     

海洋大气区氯离子在混凝土中的沉积与传输行为研究综述

海洋大气区氯离子对钢筋混凝土的侵蚀行为可分为两个阶段,首先,氯离子在风力作用下附着在混凝土表面,其次,从混凝土表面向混凝土内部侵蚀。基于海洋大气区氯离子对混凝土侵蚀的全过程,对已有研究进行归纳总结,阐述了各影响因素对沉积过程的影响规律。其中,海水含盐量、风速、暴露时间与混凝土氯离子沉积量呈正相关关系,距海岸距离与混凝土氯离子沉积量呈负相关关系;论述了各影响因素对传输过程的影响规律,水灰比越大、暴露时间越长、温度越高、内外湿度梯度越大、碳化越严重越容易形成对流区。目前,针对海洋大气区氯离子在混凝土中沉积和传输行为开展研究多基于单因素,多因素耦合作用下的沉积和传输行为尚需进一步研究。     

固体酸SO42-／TiO2-La2O3催化合成乙酸正丁酯

采用低温（-15℃）陈化法制备SO42-/TiO2-La2O3稀土掺杂固体酸（STL）,用于催化合成乙酸正丁酯,研究醇酸摩尔比、反应时间、催化剂用量等因素对酯化率的影响。结果表明：当n（正丁醇）：n（乙酸）=1．5：L,反应时间为2h,催化剂用量占反应物总质量的1．4％时,乙酸正丁酯的酯化率可达99．5％。     

Preparation and structure characteristics of nano-Bi2O3 powders with mixed crystal structure

The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi(NO3)3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi(NO3)3 reacts at 90℃ for 2 h, the Bi203 powders with 60 nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi^3 to O^2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.     

ALD淀积温度对HfO2高k栅介质材料特性的影响

采用原子层淀积方法,在不同生长温度下制备了HfO2高k栅介质薄膜,研究了生长温度对HfO2薄膜特性的影响.实验结果表明,HfO2薄膜的生长速率受生长温度的影响很大,在高温区将随着温度的上升而增大,而在低温区将随着温度的降低而增大.通过分析HfO2薄膜的C-V特性发现,不同生长温度下淀积的HfO2薄膜的介电常数和氧化层缺陷数量都有很大区别,过高和过低的生长温度都将增加HfO2薄膜中的原生缺陷,其中,280℃～310℃区间生长的HfO2薄膜中的缺陷最少.     

Mn-Ce/AC催化剂低温NH3选择性催化还原NO的性能

采用浸渍法制备了一系列Mn-Ce/AC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.结果表明,氨氮比和空速对Mn-Ce/AC催化剂的催化活性有一定的影响.n(NH3)∶ n(NO)=1∶1,空速为2000h-1时活性最佳,在反应温度接近90℃时NO脱除率达到90％,在120～250℃温度范围内,能保持99％以上的高脱除率.Mn-Ce/AC催化剂抗水和抗硫性能良好,在相对较高的温度下,催化剂仍能保持高的脱硝性能;低浓度的SO2对催化剂脱硝性能影响不大,但当SO2浓度上升到1 500 μL/L时,NO的最高脱除率只有70％.     

Electrolysis expansion performance of semigraphitic cathode in [K3AlF6/Na3AlF6]-AlF3-Al2O3 bath system

The electrolysis expansion of semigraphitic cathode in [K₃AlF₆/Na₃AlF₆]-AlF₃-Al₂O₃ bath system was tested by self-made modified Rapoport apparatus. A mathematical model was introduced to discuss the effects of α _CR (cryolite ratio) and β _KR (elpasolite content divided by the total amount of elpasolite and sodium cryolite) on performance of cathode electrolysis expansion. The results show that K and Na (potassium and sodium) penetrate into the cathode together and have an obvious influence on the performance of cathode electrolysis expansion. The electrolysis expansion and K/Na penetration rate increase with the increase of α _CR. When α _CR=1.9 and β _KR=0.5, the electrolysis expansion is the highest, which is 3.95%; and when α _CR=1.4 and β _KR=0.1, the electrolysis expansion is the lowest, which is 1.28%. But the effect of β _KR is correlative with α _CR. When α _CR=1.6 and 1.9, with the increase of β _KR, the electrolysis expansion and K/Na penetration rate increase. However, when α _CR=1.4, the electrolysis expansion and K/Na penetration rate firstly increase and then decrease with the increase of β _KR. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China