Particle characteristics of a stable fluidized bed aerosol generator

An aerosol generator consisting of a vibrating system for feeding dust into a fluidized bed was developed and tested to determine its dust output characteristics. The dust feed unit can produce 0–40 g min⁻¹ of coal dust and shows constant output up to 3 h operation durations. These correspond to mass concentrations of 0–101 g m⁻³ of coal particles for an air flowrate of 395 l min⁻¹ through the aerosol generator. The aerosolized coal particles show constant particle size distribution with time for up to h of testing under varied operation parameters. The normalized particle size distribution remains almost identical for a given feed material for a range of dust loadings. The time required to reach steady state aerosol generation is negligible for the sizes of coal particles used in this investigation.     

氨法浸出锌冶金渣尘提锌工艺及动力学研究

锌冶金渣尘作为一种重要的锌二次资源,来源广、储量大、具有较高的综合回收利用价值。以NH₃-CH₃COONH₄-H₂O为浸出体系,考察粒度、反应时间、搅拌速度、液固比、总氨浓度、NH₃与NH₄⁺物质的量比和温度对锌浸出率的影响,结果表明：控制浸出温度为25 ℃、总氨浓度为5 mol/L、液固体积质量比为5 mL/g、n（NH₃）/n（NH₄⁺）=1:1、搅拌速度为300 r/min、浸出时间为60 min,在此条件下锌的浸出率可达84%。含锌冶金渣尘浸出动力学分析显示,浸出反应表观活化能为22.66 kJ/mol,锌浸出过程的浸出速率受固体膜层扩散及界面化学反应共同控制,并获得了浸出锌的动力学速率方程。     

Sintering of Fine Oxide Powders: I, Microstructural Evolution

Microstructural evolution during sintering has been investigated using fine powders of CeO₂ and Y₂O₃ with excellent sinterability. A universal pore size distribution, normalized by particle size, has been determined and found to be a function of density only. Microstructure evolves toward the universal distribution, with or without densification, signifying homogenization at all stages. This may even involve the elimination of supercritical pores, at low densities, which are otherwise thermodynamically not sinterable. Theoretical justification for these observations is made by using a network model with a random, but spatially homogeneous, distribution of spherical particles. Final microstructure after full density is reached is also found to evolve toward a universal steady state of grain shape/grain size distribution regardless of initial state.     

碳酸氢铵溶液中偏钒酸铵的冷却结晶

针对钒渣空白焙烧-铵化浸出新工艺产生的浸出液,在对NH₄HCO₃-NH₄VO₃-H₂O溶解度数据进行分析的基础上,采用冷却结晶分离方法分离溶液中偏钒酸铵。采用程序控温冷却方式考察了碳酸氢铵浓度、降温速率、搅拌速率、晶种添加量等因素对偏钒酸铵从70℃冷却结晶至40℃时结晶率、产品粒度、形貌等的影响,明确了偏钒酸铵冷却结晶规律,建立了偏钒酸铵从碳酸氢铵母液中高效结晶分离方法,获得了结晶最佳工艺条件。在碳酸氢铵浓度10g/L、降温速率0.36℃/min、搅拌速率200r/min、晶种添加量1.0%时偏钒酸铵结晶率可达94.28%,得到的偏钒酸铵晶体纯度为99.5%,产品粒度均匀,平均粒径约为152μm,晶体成规则棱柱状结构。     

密闭空间内聚乙烯粉尘爆炸火焰传播特性的实验研究

采用竖直、可视粉尘爆炸火焰传播实验平台,结合粒子图像测速PIV技术测得喷粉的冷态流场分布,研究聚乙烯粉尘在密闭容器内的爆炸火焰传播特性,探讨火焰结构与锋面位置的动态变化、火焰传播速度等参数的变化规律。结果表明,在200～1000 g/m³浓度范围内,低浓度聚乙烯粉尘爆炸火焰呈不连续片羽状结构,火焰锋面呈离散的星点状。粉尘浓度增加,火焰连续性及亮度增强,锋面呈齿状,并在400 g/m³火焰最明亮,火焰平均传播速度均随粉尘浓度的增加先增大后减小。采用均方根湍流速度量化体系整体脉动幅度,浓度接近最佳爆炸浓度400 g/m³时,均方根湍流速度为3.21 m/s。     

超重力液相沉淀法制备纳米铁酸钴

针对磁力搅拌器制备纳米材料时存在粒径分布宽、分散不均匀的问题,采用撞击流-旋转填料床结合化学共沉淀法,以Fe（NO₃）₃·9H₂O、Co（NO₃）₂·6H₂O、NaOH为原料制备CoFe₂O₄纳米颗粒。研究了转速、液体流量、NaOH浓度以及晶化时间对CoFe₂O₄纳米颗粒粒径的影响;并与磁力搅拌器制备的CoFe₂O₄纳米颗粒在磁性能方面进行了对比。采用X射线衍射仪（XRD）、傅里叶红外光谱仪（FTIR）、透射电镜（TEM）、纳米粒度仪及振动样品磁强计（VSM）对产物的粒径形貌及磁性能进行表征。结果表明：CoFe₂O₄纳米颗粒的粒径随转速、液体流量和NaOH浓度的增加而减小,但随晶化时间的增加而增大。最佳工艺条件为：转速900r/min,液体流量60L/h,NaOH浓度3mol/L,晶化时间6h。此条件下制备的CoFe₂O₄纳米颗粒的粒径约为20nm,饱和磁化强度为75.43emu/g,较磁力搅拌器提高40%。     

氨对平板显示玻璃窑炉烟尘性质的影响

通过平板显示玻璃窑炉烟气脱硝除尘装置,考察氨组分对烟尘析出温度、含水量及烟尘性质的影响规律.结果表明,烟尘析出温度随着烟气中氨浓度的增加而提高,烟尘含水量也明显增大,平均含水量约为7％～8％.通过扫描电镜和粒度分布仪表征,烟气中氨710 mg·Nm-3时,与无氨烟气比较,烟尘中出现氧化硼氨水合物,烟尘颗粒出现积聚现象,...     

Preparation of transparent BaSO4 nanodispersions by high-gravity reactive precipitation combined with surface modification for transparent X-ray shielding nanocomposite films

BaSO₄ nanoparticles as important functional materials have attracted considerable research interests, due to their X-rays barrier and absorption properties. However, most of BaSO₄ nanoparticles prepared by traditional technology are nanopowders with broad size distribution and poor dispersibility, which may greatly limit their applications. To the best of our knowledge, the synthesis of transparent BaSO₄ nanodispersions was rarely reported. Here, we firstly present a novel and efficient method to prepare transparent and stable BaSO₄ nanodispersions with a relatively small particle size around 10 to 17 nm using a precipitation method in a rotating packed bed (RPB), followed by a modification treatment using stearic acid. Compared with the BaSO₄ prepared in a traditional stirred tank, the product prepared using an RPB has much smaller particle size and narrower size distribution. More importantly, by using RPB, the reaction time can be significantly decreased from 20 min to 18 s. Furthermore, the transparent BaSO₄-polyvinyl butyral nanocomposite films with good X-ray shielding performance can be easily fabricated. We believe that the stable BaSO₄ nanodispersions may have a wide range of applications for transparent composite materials and coatings with X-ray shielding performance for future research.     

The removal of phosphate ions from aqueous solution by fly ash, slag, ordinary Portland cement and related blends

Phosphate ions have been removed from aqueous solution by fly ash, slag, ordinary Portland cement (OPC) and related cement blends. The rate and efficiency of PO₄³⁻ removal were found to increase in the order: fly ash, slag, OPC, apparently mimicking the order of increasing percent CaO in the adsorbents. Blending OPC with fly ash or slag evidently results in diminished PO₄³⁻ removal efficiency. Better removal was obtained at higher solute concentration, acidic pH and higher temperature. The effect of particle size and the speed of mixing were found not to be significant. A first-order kinetic model was used to obtain values for overall sorption rate constants and intraparticle diffusion constants. The Frumkin isotherm was found to be the appropriate equation for modelling isotherms from the experimental adsorption data, and values have been obtained for the isotherm constants. A 400-mg/l PO₄³⁻ (as P) solution was fed at a steady velocity of 2.0 cm/min through a 2.0-cm fixed-bed column (at pH 9.0 and 25 °C), and breakthrough curves were constructed to obtain estimated adsorption capacity values of 32, 60, 75, 78 and 83 mg PO₄³⁻/g adsorbent for fly ash, slag, OPC+fly ash, OPC+slag and OPC, respectively.     

酸浸法提取粉煤灰中氧化铝溶出规律的研究

酸浸法是粉煤灰提铝的主要方法之一。介绍了一种提取粉煤灰中氧化铝的方法,用不同浓度的硫酸作溶剂,用氟化钠作助溶剂,通过一定配比加入粉煤灰中反应。实验结果表明,当温度为沸腾温度、氟化钠添加量为0、硫酸浓度为12 mol/L、溶出时间为150 min时,氧化铝的溶出率可达80.19%。该工艺反应在低温常压下进行,避免了高温烧结工艺,节约了能源,降低了成本,具有较高的实用价值。     

Decomposition of CCl2F2 over metal sulfate catalysts

Activity for hydrolysis of CCl₂F₂ (CFC12) on various metal sulfate was investigated. Zr(SO₄)₂ was found to be the most active while FeSO₄, Cr₂(SO₄)₃, Al₂(SO₄)₃, La₂(SO₄)₃ and Ce₂(SO₄)₃ had intermediate activity. MnSO₄, CoSO₄, and MgSO₄ showed low activity and SrSO₄, CaSO₄, and BaSO₄ had even less activity. The major carbon containing product was CO₂ and small amount of CClF₃ and CO were formed over several sulfates. The crystal structure of the sulfates was stable during decomposition of CCl₂F₂, and the conversion reached a steady state after initial decrease at 275 °C over Zr(SO₄)₂ catalyst. The concentration of surface hydroxyl was larger than that over AlPO₄-based catalysts and a reaction mechanism similar to that over AlPO₄-based catalysts was proposed.     

用于选择性激光烧结成型的聚酰胺6/硫酸钙复合粉体的制备及性能研究

采用溶液沉淀法制备了聚酰胺6/硫酸钙（PA6/CaSO₄）复合粉体,通过扫描电子显微镜（SEM）、差示扫描量热仪（DSC）、激光粒度分布仪和Ｘ射线衍射仪（XRD）对复合粉体的微观形貌、热性能、粒度分布、晶体结构和流动性进行了表征。结果表明,随着CaSO₄的加入,PA6/CaSO₄复合粉体由松散的球形结构转变为密实的球形结构;CaSO₄的加入能够提高PA6/CaSO₄复合粉体的结晶度并拓宽其烧结温度窗口,在CaSO₄含量为5 %（质量分数,下同）时,结晶度和烧结温度窗口均达到最大值,分别为61.84 %和18.95 ℃;PA6/CaSO₄复合粉体的粒径随CaSO₄含量的增加呈现先减后增的趋势,休止角先减后增,堆积密度先增后减;当CaSO₄含量为3 %~5 %时,PA6/CaSO₄复合粉体的流动性能最佳,最适用于选择性激光烧结。     

CRC系列熟料辊式破碎机的工作机理及运行维护

CRC系列辊式破碎机在熟料的破碎过程中保持低转速运转,转动部件的转速仅为4 r/min左右,运行平稳,基本没有扬尘;同时耐磨性较好、电耗较低;破碎机出料粒度通过辊间间隙来控制,可保证熟料粒度在比较均匀且集中的范围内,以利后续水泥粉磨系统的稳定控制。在运行维护中,要重点关注破碎机上部及下部的堆料和外界异物的影响,合理安排辊套磨损修复周期。     

Very Rapid Densification of Nanometer Silicon Carbide Powder by Pulse Electric Current Sintering

Rapid densification of a nanometer SiC powder doped with 2.04 wt% Al₄C₃ and 0.4 wt% B₄C was conducted by using a nonconventional sintering technique called pulse electric current sintering (PECS). In all experiments, the sintering temperature and applied pressure were kept to be 1600^oC and 47 MPa, respectively, while heating rates varied between 100^oC/min and 400^oC/min and the holding time was either 2 or 5 min. All of the specimens which were PECS-sintered under various conditions reached near-theoretical density. The microstructures of the rapidly densified SiC ceramics consisted of large elongated grains, and the grain size increased with the increase of heating rate. Polytype transformation of SiC occurred during the PECS process, where faster heating favored the formation of 6H polytype while slower heating favored 4H polytype.     

Densification Behavior of Single-Crystal and Polycrystalline Spherical Particles of Zirconia

Micrometer size polydispersed spheres of zirconia were produced via electrostatic atomization and pyrolysis of aqueous zirconium acetate-yttrium acetate precursors. Varying the precursor composition in the ZrO₂-rich region of the ZrO₂-Y₂O₃ binary system resulted in the production of either single-crystal (0 and 10 mol% Y₂O₃O or dense polycrystalline (3 mol% Y₂O₃) zirconia spheres of similar size distribution for densification studies. Powders of either the singlecrystal or the polycrystalline particles exhibited contrasting densification behavior; viz., powder compacts composed of polycrystalline particles obtained significantly higher endpoint densities than their single-crystal counterparts. Microstructural observations showed that while necks between single-crystal particles reached a stable size, necks between polycrystalline particles continued to grow.     

Effect of interlayer anions on chromium removal using Mg–Al layered double hydroxides:Kinetic,equilibrium and thermodynamic studies

The influence of interlayer anions such as NO3-, SO42-and Cl-on Mg–Al hydrotalcites for Cr(VI) removal from aqueous solution was studied. The structure of the prepared LDHs was characterized by XRD, SEM, FTIR, TGA, BET surface area and p Hzpc. The sorbent ability and sorption mechanisms were also investigated. The LDHs exhibit high removal for Cr(VI), and the sorbed amount depends on the nature of interlayer anion, which decreased in the following order: NO3-N Cl-N SO42-. Nitrate-containing LDH reached a Cr(VI) sorption equilibrium within only 30 min. The effects of operating conditions, including initial concentration, solution p H, agitation time and sorbent amount have been studied in batch mode. The optimum conditions were observed at an initial concentration of 100 mg·L-1, p H = 6, agitation time of 60 min and a sorbent dose of 2 g·L-1. The equilibrium data were fitted to the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The Langmuir model was found to sufficiently describe the sorption process, offering a maximum sorption capacity of 71.91 mg·g-1. The sorption kinetic follows pseudo-second-order reaction with high accuracy. Thermodynamic parameters suggested that the sorption process is spontaneous and endothermic in nature.     

GO/Al2O3复合纳滤膜的制备及其稳定性能研究

以平均孔径为20 nm的Al₂O₃管式超滤膜为载体,经多巴胺改性后,利用压力驱动沉积法成功制备出能在水溶液中长期稳定的GO/Al₂O₃复合纳滤膜,并通过改变负载量实现了对GO层厚的调控。结果表明,随错流时间的延长,不同GO负载量下GO/Al₂O₃复合纳滤膜的纯水渗透系数均呈现先降低后稳定的趋势。且随着GO负载量的增加,稳态纯水渗透系数逐渐降低;当GO负载量增加到90 mg/m²后,GO/Al₂O₃复合纳滤膜对一二价盐的渗透系数与截留率均无显著变化。同时,由于盐测试过程中残余的盐离子在GO片层间产生了交联作用,从而导致随着在纯水中存放时间的延长,不同GO负载量的GO/Al₂O₃复合纳滤膜对一二价盐的截留率均呈上升趋势。GO负载量为140 mg/m²的GO/Al₂O₃复合纳滤膜在水中浸泡680 h后对1 mmol/L Na₂SO₄的截留率可达到91.0%。GO/Al₂O₃复合纳滤膜对四种一二价盐的截留率满足：R(Na₂SO₄) > R(MgSO₄) > R(NaCl) > R(MgCl₂)。     

双峰孔分布Al_2O_3载体的研究

采用两种不同孔径分布的拟薄水铝石干胶粉,制备呈明显双峰孔分布的Al2O3载体。考察原料粉体、孔结构调节剂种类和用量以及焙烧温度等对Al2O3载体的孔分布的影响,并采用N2物理吸附法和高压压汞法分析载体孔结构。结果表明,两种干胶粉按质量1∶1混合时,能改变单一粉体的堆积状态,制得载体兼具单一原料制备载体时的孔分布,孔容达到最大,为1.58 cm3·g-1,且孔径分布集中在(10~100)nm和300 nm以上;加入不同孔结构调节剂后,对载体孔径分布调节作用相似,孔径分布更为集中;添加质量分数5%尿素后,(10~100)nm孔径分布达到62.1%;载体的比表面积随尿素含量增加依次降低,适量添加调节剂可制得所需最佳孔径分布;载体在约920℃焙烧时,晶型为γ相和δ相的混合相。     

CeO2/g-C3N4复合光催化剂的制备及其性能研究

采用高温聚合有机物前驱体的方法,以三聚氰胺为前驱体,制得类石墨型氮化碳(g-C₃N₄)粉末,采用水热法制得CeO₂/g-C₃N₄复合光催化剂,对其进行了表征,考察了CeO₂/g-C₃N₄复合光催化剂在可见光下处理亚甲基蓝的性能,并对CeO₂/g-C₃N₄复合光催化剂进行回收实验、吸附实验以及光催化动力学分析。结果表明,CeO₂/g-C₃N₄中g-C₃N₄和CeO₂分别为石墨相和萤石相,复合CeO2使得g-C₃N₄的吸附性能有了大的提高,15 min能达到吸附平衡,吸附82.5%的亚甲基蓝;45 min后对亚甲基蓝处理率达到99.45%,远远快于g-C₃N₄。CeO₂/g-C₃N₄在5次使用后仍然可以保持73.1%的净化效果。亚甲基蓝处理过程包括吸附和光解2部分,光解反应符合一级动力学方程。     

厌氧氨氧化颗粒污泥的快速形成

以好氧硝化颗粒污泥与厌氧氨氧化生物膜作为接种污泥,在缺氧条件下利用EGSB反应器培养厌氧氨氧化颗粒污泥。根据反应器内污泥性状以及运行效果,随时调整反应器的进水基质浓度以及上升流速等关键控制因素,加快厌氧氨氧化颗粒污泥的快速形成。同时考察系统的脱氮效能、粒径分布、厌氧氨氧化颗粒污泥表面形态以及内部结构与微生物分布情况。反应器运行80 d后,培养出成熟的厌氧氨氧化颗粒污泥,平均粒径为0.556 mm;89 d时,总氮去除负荷达4.758 kg N·m^-3·d^-1。FISH表明颗粒污泥中厌氧氨氧化菌为优势菌种,同时SEM与TEM观察表明颗粒污泥是由多个小颗粒聚集形成,而且形状不规则,内部结构排列紧密。