锥形流化床混凝装置内混凝指标和絮凝体分形维数

利用锥形流化床混凝工艺中固相颗粒的流化运动在液相中形成的微涡流,使液相中的胶体颗粒碰撞和聚集,形成絮体。结果表明在论文研究范围内,高岭土悬浊液去除率(23.97%～85.37%)随GT(1836.51～5399.53)增加而提高。G值的减小(169.2～189.7s-1)和混凝时间增加都会引起混凝效率的升高。采用分形维数模型计算得到,相同运行条件下形成絮体的分形维数相关系数均在0.9以上,表明絮体性质具有相似性,因此相同操作条件下絮体自由沉降速度区间分布狭窄,相同沉速的颗粒数量百分比峰值达45%。     

预臭氧氧化对聚硅酸铝铁絮凝效果及絮体形态影响研究

从絮体的分形结构、粒度、有效密度等微观特性出发,研究预臭氧氧化对聚硅酸铝铁絮凝效果和絮体形态的影响.结果表明,臭氧具有良好的助凝作用,并存在臭氧最佳投加量.一定浓度的臭氧能增大混凝过程中絮体的粒径,改变絮体的形态,使其更加规整,从而使分形维数发生变化.同时,适当的预臭氧氧化能增大絮体的有效密度,使絮体更加密实,提高沉降...     

不同水处理工艺的混凝效果比较

该文以宁夏宁东地区黄河水为研究对象,考察了不同混凝条件（常规混凝沉淀池、微涡旋混凝沉淀池、反冲洗水回流沉淀池）下三种水处理工艺对混凝效能的影响。结果表明微涡旋改造有助于提高絮凝池的混凝效果,絮体的沉降性得到改善,“跑矾”现象得到缓解,絮体颗粒数目较折板絮凝池减少,沉淀池出水浊度明显降低;滤池反冲洗水回流技术可以有效地提高浊度的去除率以及改善絮体的沉降性能,且絮体颗粒数目较微涡旋絮凝池有明显减少,说明增加水体中颗粒数目可以有效地提高混凝效果;由分形维数的数据可以看出,微涡旋改造和反冲洗水回流可以明显提高絮体的分形维数,改善了絮体的沉降性。     

有机絮凝剂对铁矿相沉降性能影响及其吸附机理

通过模拟拜耳法赤泥沉降过程研究了聚丙烯酸铵(PAAA)、阴离子聚丙烯酰胺(APAM)和氧肟酸絮凝剂(HPAM/HCPAM)对赤铁矿和针铁矿沉降性能的影响规律和絮凝后絮体的粒径分布及分形维数,并利用傅里叶变换红外光谱探讨了絮凝剂与铁矿相的吸附机理。在不同类型絮凝剂中,添加氧肟酸絮凝剂铁矿相沉降速度最快,且氧肟酸含量越高,沉降性能越好;聚丙烯酸铵和阴离子聚丙烯酰胺絮凝剂对铁矿相沉降性能影响较小;同等条件下赤铁矿沉降速度要远高于针铁矿,增加絮凝剂添加量有助于提高针铁矿沉降速度。在赤铁矿絮体中,添加PAAA絮体粒径最大,HPAM絮体分形维数最大、致密性最好;在针铁矿絮体中,添加APAM絮体粒径最大,HCPAM絮体分形维数最大、致密性最好。氧肟酸絮凝剂与铁矿相形成结构稳定、吸附能力强的五元环状螯合物,增强了赤铁矿和针铁矿的絮凝效果;PAAA通过双齿桥接配位与赤铁矿表面发生吸附,通过单齿配位与针铁矿表面发生吸附,其吸附能力弱于五元环;APAM与赤铁矿和针铁矿表面发生化学吸附,沉降性能差。     

有机絮凝剂对铁矿相沉降性能影响及其吸附机理

通过模拟拜耳法赤泥沉降过程研究了聚丙烯酸铵(PAAA)、阴离子聚丙烯酰胺(APAM)和氧肟酸絮凝剂(HPAM/HCPAM)对赤铁矿和针铁矿沉降性能的影响规律和絮凝后絮体的粒径分布及分形维数,并利用傅里叶变换红外光谱探讨了絮凝剂与铁矿相的吸附机理。在不同类型絮凝剂中,添加氧肟酸絮凝剂铁矿相沉降速度最快,且氧肟酸含量越高,沉降性能越好;聚丙烯酸铵和阴离子聚丙烯酰胺絮凝剂对铁矿相沉降性能影响较小;同等条件下赤铁矿沉降速度要远高于针铁矿,增加絮凝剂添加量有助于提高针铁矿沉降速度。在赤铁矿絮体中,添加PAAA絮体粒径最大,HPAM絮体分形维数最大、致密性最好;在针铁矿絮体中,添加APAM絮体粒径最大,HCPAM絮体分形维数最大、致密性最好。氧肟酸絮凝剂与铁矿相形成结构稳定、吸附能力强的五元环状螯合物,增强了赤铁矿和针铁矿的絮凝效果;PAAA通过双齿桥接配位与赤铁矿表面发生吸附,通过单齿配位与针铁矿表面发生吸附,其吸附能力弱于五元环;APAM与赤铁矿和针铁矿表面发生化学吸附,沉降性能差。     

板式换热器内颗粒污垢表面分形特性

利用分形理论及其相关的图像处理方法对板式换热器内不同粒径的颗粒污垢所沉积的表面形态进行研究。结果表明:颗粒污垢具有分形特性,而且颗粒粒径变化影响污垢表面分形维数,纳米级颗粒污垢的分形维数比微米级颗粒污垢的大。分形维数还可用来定量描述颗粒污垢的孔隙和粗糙表面形貌,分形维数越大污垢表面越粗糙。     

壳聚糖盐酸盐对老鹳草水提液絮凝效果及微观特性的影响

研究了壳聚糖盐酸盐对老鹳草水提液的絮凝澄清效果,利用微电泳仪、激光粒度分析仪及图像法对上清液的ζ电位、粒度分布及絮体的分形维数等微观特征参数进行测量和分析,考察其随絮凝剂用量的变化规律。实验结果表明:壳聚糖盐酸盐最佳投加剂量为0.196 g?L-1,此时杂质絮凝率为90.1%,有效成分总黄酮损失率为0.8%。在最佳絮凝剂投加量下,上清液的ζ电位趋近于零,胶体粒子处于等电态,容易发生絮凝和聚沉;上清液中颗粒的粒径分布在5~62μm,平均粒径值为10.88μm,与原液相比绝大部分大颗粒被沉降;絮凝体的二维分形维数达到最大值1.43,说明絮体结构致密。     

水动力学条件对絮体形成的影响

利用颗粒运动方程,分析颗粒运动导致的碰撞絮凝,提出涡旋惯性离心力和剪切力是颗粒接触絮凝的主要动力因素,其中涡旋剪切力是主导动力;湍流过渡区控制絮体的成长尺度和密度;并讨论了提高絮凝效率的技术途径。     

用分形理论评价超塑化剂对水泥絮凝结构影响

用光学显微镜对不同超塑化剂掺量情况下的水泥絮凝结构进行了研究,并结合分形理论对各絮凝形态进行定量评价.结果表明:絮凝颗粒为组成水泥浆体的基本单元;超塑化剂的加入可以有效破坏水泥絮凝结构;在最佳掺量范围内,随掺量增加,水泥絮凝结构的平面分形维数增大.     

分形结构团聚体在剪切流场中分散行为的三维数值模拟

为深入了解颗粒团聚体的分散机理及其动态细节,在经典离散元理论模型中引入范德华力和流体拖曳力,开发了三维颗粒离散元程序DEMix3D,对具有分形结构的颗粒团聚体在纯剪切流场中的分散过程进行数值模拟。结果表明:团聚体在流场中先发生变形然后再分散,分散过程中存在剥蚀和破碎两种分散方式;相同剪切流场下,初始团聚体的分形维数越小其分散效率越高。     

淮南煤焦颗粒内部孔隙结构在燃烧过程中的变化

用氮气等温吸附/脱附（77 K）方法测量了淮南低变质煤及其在850℃条件下燃烧得到半焦的内部孔隙结构.通过分析得到有关煤焦颗粒内部孔隙结构的参数及其与燃尽率之间的关系.由吸附/脱附曲线判断煤焦孔洞的形状呈多样性.结合吸附理论,认为分形BET和分形Freundlich方程回归得到的分形维数分别表征颗粒内部大中孔表面分形维数和微孔体积分形维数.发现在燃烧过程中煤焦的表面分形维数及体积分形维数具有不同的变化趋势.     

Morphological characterization of super fine pulverized coal particle. Part 2. AFM investigation of single coal particle

Super fine pulverized coal combustion is a new pulverized coal combustion technology which has better stability, higher combustion efficiency and lower NO_x and SO₂ emission than that using conventional particle sizes. In this paper we applied fractal analysis based on power spectral density (PSD) and slit island method (SIM), three-dimensional (3D) surface roughness measurement and surface-topography observations from AFM to form a proper investigative tool which may give a relatively full picture of surface morphology of super fine pulverized coal particles for the first time. The final results indicate that both fractal dimensions calculated by SIM and PSD and roughness of coal particle size increase with the increase of the coal particle size. Besides, the grey relational analysis was used to study the degree of relative importance of the influential factors about the microroughness of coal particle surfaces. The results show that the influence of the coal particle size is the greatest compared with the coal qualities and fractal dimensions.This work provides some reference for a relatively full picture of surface morphology of super fine pulverized coal particles. The findings from this work will be helpful to form the basis and provide guidance for further studies on the chemical and combustion characteristics of super fine pulverized coal particles.     

水泥颗粒微观分维与宏观流动性关系的研究

将微观分维作为表征水泥颗粒的形态参数；用数字显微系统测算了5种水泥颗粒样品的微观分维，研究了水泥微观分维及其与粉体流动性指数的关系，结果表明：水泥粉体微观分维与其流动性指数呈线性负相关。     

An investigation of fractal characteristics of mesoporous carbon electrodes with various pore structures

Fractal characteristics of mesoporous carbon electrodes were investigated with various pore structures using the N₂ gas adsorption method and the transmission electron microscopy (TEM) image analysis method. The mesoporous carbons with various pore structures were prepared by imprinting mesophase pitch used as a carbonaceous precursor with different colloidal silica particles. All imprinted mesoporous carbons were composed of two groups of pores produced from the carbonisation of mesophase pitch and from the silica imprinting. The overall surface fractal dimensions of the carbon specimens were determined from the analyses of the N₂ gas adsorption isotherms. In order to distinguish the surface fractal dimension of the carbonisation-induced pore surface from that fractal dimension of the silica-imprinted pore surface, the individual surface fractal dimensions were determined from the image analyses of the TEM images. From the comparison of the overall surface fractal dimension with the individual surface fractal dimensions, it was recognised that the overall surface fractal dimension is crucially influenced by the individual surface fractal dimension of the silica-imprinted pore surface. Moreover, from the fact that the silica-imprinted pore surface with broad relative pore size distribution (PSD) gave lower value of the individual surface fractal dimension than that pore surface with narrow relative PSD, it is concluded that as the silica-imprinted pores comprising the carbon specimen agglomerate, the individual surface fractal dimension of that pore surface decreases.     

Asymmetric human lung morphology induce particle deposition variation

The effect of lung morphology on the heterogeneity of regional ventilation and particle deposition in the bronchial airways is studied using Horsfield's regular-asymmetric lung model. Flow distribution among the airways is calculated by solving the whole tree network, assuming laminar flow hydrodynamic resistances without accounting for gravitationally enhanced preferential airflow distribution. The variation of morphological properties, such as the lung volume and surface area distal to any airway generation, and physiological properties, such as ventilation and particle deposition, is calculated, and fractal dimensions that characterize these properties and processes are computed. The close agreement between the model fractal dimension characterizing ventilation and those found from clinical data assess the validity of the model. It is shown that the fractal dimensions that characterize the morphological properties and the physiological processes are similar, suggesting that all are related and stem from a common underlying attribute—the lung morphology. The variation of particle deposition in the lung, as well as the variation of ventilation and morphological attributes, increases moderately with the lung tree asymmetry. The deposition density, regarded as a key exposure metric or therapeutic index, does not follow a spatial scale-free distribution.     

水泥颗粒粒度分布分形维与其胶砂抗压强度的关系研究

为研究水泥颗粒粒度分布分形维与其胶砂抗压强度的关系,利用粒度分布分形维的计算模型分析了有关文献报道的10种水泥颗粒粒度分布分形维值,结果表明:定量表征其分形特征的分形维值在2.325～2.435之间,各水泥颗粒粒度分布具有分形特征;分析了水泥颗粒粒度分布分形维值与水泥3d抗压强度、28d抗压强度的关系,分析表明:化学组成和矿物组成基本相同的条件下,水泥颗粒粒度分布分形维与水泥胶砂的3d、28d抗压强度具有较好的正线性相关关系。     

水射流解离煤的分形特征

利用高压水射流粉碎机与球磨机对煤进行超细解离,对解离后的煤颗粒进行了扫锚电镜分析,利用扫锚电镜图像。基于图像处理技术与分形理论,计算了粒度分布分形维数、边界形状分形维数与节理表面分形维数。利用上述3种分维数对解离后的煤颗粒的分形特征进行了研究。     

分形理论对煤粉粒度和孔隙的表征

介绍了分形理论的定义,说明自相似性和标度不变性是分形的2个重要特征。从粒度分形规律和煤粉研磨超细化分形2个方面对煤粉超细化分形进行了研究,说明煤粒研磨过程中,绝大部分能耗用在小颗粒的研磨上,颗粒表面分形维数越大,研磨能耗越高,颗粒形状越不规则,能耗越大。详细介绍了气体吸附法、压汞法和扫描电镜图像法3种测定煤粉孔隙分形维数的方法,阐述了煤粉粒度和孔隙的分形规律及国内外相关研究现状,着重说明了煤粉的研磨、高效燃烧、煤粒与孔隙发育程度的关系及煤粒孔隙的特点与瓦斯存在形式的关系。最后提出了煤粉粒度和孔隙的研究方向。     

Dependence of the Mechanical Sensitivity on the Fractal Characteristics of Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine Particles

Three fabrication methods were used to synthesize HMX powders with different particle sizes and microscopic morphologies. All as‐prepared samples were characterized by laser granularity measurements and scanning electron microscopy (SEM). The mechanical sensitivity and thermal stability of the different HMX powders were characterized using mechanical sensitivity tests and differential scanning calorimetry (DSC). Size distribution data and SEM images were used to find the size fractal dimension (D) and surface fractal dimension (D_s) of HMX samples, which were calculated by the least‐squares method and fractal image processing software (FIPS), respectively. The parameters D and D_s quantize two important properties of HMX particles, namely the complexity of the particle size distribution and the irregularity of the particle surface, which affect the thermal conductivity of the particle group if it is exposed to stimuli such as impact, friction or heating. The fractal dimensions reveal the dependence of the mechanical sensitivity of HMX on the powder size, size distribution and microscopic morphology. The results indicate that the proportion of fine particles in HMX powder increases as the D value increases, which causes decreased impact sensitivity. This occurs because hot spot formation leading to an explosion is more difficult because of the improved thermal conductivity of the particle group. Similarly, the surface roughness of HMX particles increases with an increase in D_s, causing an increase in friction sensitivity because of the excessive accumulation of frictional heat. In addition, thermal analysis results indicate that the maximum thermal decomposition rate of HMX decreases with increasing D and D_s.