水泥颗粒分散度对其性能影响的研究

本研究通过测定水泥体系颗粒分布,比表面积和水泥的主要性能,找出颗粒分散度与水泥性能之间的内在联系。 试验结果表明:本研究所涉及的水泥体系,颗粒分布符合Rosin—Rammler—Bennet提出的粉磨产品粒度分布的数学表达式。保持水泥的化学组成、矿物组成不变,使水泥颗粒分布趋向合理,就会取得水泥胶砂各龄期强度明显增加,水泥产品合格率提高的实际效果。 结论:改变水泥磨体系的有关操作参数,能使水泥的颗粒分布趋向合理,提高水泥产品的合格率。

关于水泥分散度与余水泥强度等级关系的研究

本文通过对水泥分散度实验,阐述分布参数、粒径间隔等对水泥强度的影响,介绍了实验环节应用的分散度理论,总结出分散度和强度等级关系,即水泥分散度、强度等级二者存在定量细度参数,此参数也是水泥生产环节粉磨细度的控制标准。

Effect of addition temperature on dispersion behavior and grain refinement efficiency of MgO introduced into Mg alloy

The effect of addition temperature of MgO particles(MgOp)on their dispersion behavior and the efficiency of grain refinement in AZ31 Mg alloy was investigated.In addition,the grain refinement mechanism was systematically studied by microstructure characterization,thermodynamic calculation,and analysis of solidification curves.The results show that the grain size of AZ31 Mg alloy initially decreases and then increases as the MgOp addition temperature is increased from 720 to 810℃,exhibiting a minimum value of 136μm at 780℃.The improved grain refinement efficiency with increasing MgOp addition temperature can be attributed to the reduced Mg melt viscosity and enhanced wettability between MgOp and Mg melt.Furthermore,a corresponding physical model describing the solidification behavior and grain refinement mechanism was proposed.

比氏旋流除砂系统除砂效果不佳的原因分析

通过测定某污水处理厂的旋流除砂系统进出水中固形颗粒含量、颗粒分散度和比重等参数,评价分析了其去除效果,找出了该系统实际运行中去除率不高和除砂量少的原因。

水合物防聚剂AA加剂技术适用性评价

天然气输送过程中与水分子在低温、高压条件下易生成水合物,造成管线压力波动甚至堵塞,增加了天然气输送风险,不利于油田稳定开发。防聚剂可使水合物呈稳定浆液输送,避免其聚集堵塞管道,具有良好的应用前景。通过检测水合物颗粒分散度、聚并弦长评价了防聚剂AA在不同温度、流速、含水率、加剂量条件下的有效作用时间,明确了AA的最佳加剂适用性,为该药剂的现场加注提供依据和保障。

钛酸钠纳米管/CPAM对高岭土的絮聚作用

山东轻工业学院张绪燕等人利用水热法合成了钛酸钠纳米管,并用TEM、Zeta电位对其进行表征,联合使用颗粒分散度分析仪与动态滤水仪研究了钛酸钠纳米管单独及与阳离子聚丙烯酰胺（CPAM）联合使用时对高岭土的絮聚作用。结果表明，钛酸钠纳米管自身对高岭土悬浮液仅有微弱的絮凝作用，

Spatial Density Distributions and Correlations in a Quasi-one-Dimensional Polydisperse Granular Gas

By Monte Carlo simulations, the effect of the dispersion of particle size distribution on the spatial density distributions and correlations of a quasi one-dimensional polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersive degree of the particle size distribution can be measured by a fractal dimension dr, and the smooth particles are constrained to move along a circle of length L, colliding inelastically with each other and thermalized by a viscosity heat bath. When the typical relaxation time τ of the driving Brownian process is longer than the mean collision time To, the system can reach a nonequilibrium steady state. The average energy of the system decays exponentially with time towards a stable asymptotic value, and the energy relaxation time τB to the steady state becomes shorter with increasing values of df. In the steady state, the spatial density distribution becomes more clusterized as df increases, which can be quantitatively characterized by statistical entropy of the system. Furthermore, the spatial correlation functions of density and velocities are found to be a power-law form for small separation distance of particles, and both of the correlations become stronger with the increase of df. Also, tile density clusterization is explained from the correlations.

Steady-State Properties of Driven Polydisperse Granular Mixtures

We represent a two-dimensional model of polydisperse granular mixtures with a power-law size distribution. The model consists of smooth hard disks in a rectangular box with inelastic collisions,driven by a homogeneous heat bath at zero gravity.The width of particle size distribution is characterized by the only parameter,namely,the fractal dimension D.The energy dissipation of the mixture is increased as D increases or as e decreases.Furthermore,it is found that the steady-state properties of the mixture such as the collision rate,granular temperature,kinetic pressure and velocity distribution depend sensitively on size distribution parameter D.

Non-Gaussian and Clustering Behavior in One-Dimensional Polydisperse Granular Gas System

We present a one-dimensional dynamic model of polydisperse granular mixture with the fractal characteristic of the particle size distribution, in which the particles are subject to inelastic mutual collisions and are driven by Gaussian white noise. The inhomogeneity of the particle size distribution is described by a fractal dimension D. The stationary state that the mixture reaches is the result of the balance between energy dissipation and energy injection. By molecular dynamics simulations, we have mainly studied how the inhomogeneity of the particle size distribution and the inelasticity of collisions influence the velocity distribution and distribution of interparticle spacing in the steady-state. The simulation results indicate that, in the inelasticity case, the velocity distribution strongly deviates from the Gaussian one and the system has a strong spatial clustering. Thus the inhomogeneity and the inelasticity have great effacts on the velocity distribution and distribution of interparticle spacing. The quantitative information of the non-Gaussian velocity distribution and that of clustering are respectively represented.

焦磷酸质量法测定粉尘中游离二氧化硅水平几点工作体会

目的探讨对各类不同性质的粉尘中游离二氧化硅(SiO_2)消解处理方法和影响游离SiO_2测定结果偏差的原因及解决方法。方法采用GBZ/T 192.4—2007焦磷酸质量法,根据粉尘样品的性质针对性地改变样品前处理、消解方法及消解温度控制。对样品消解液难溶胶状体的处理方法,游离SiO_2颗粒过滤时穿透渗出原因,分析质量控制等进行分析测定。结果粉尘样品的采集、消解方法、温度的控制、含难溶胶状物的处理、颗粒过滤时穿透渗出原因等本文均探讨出较好的解决方法;13种类型粉尘中游离SiO-2消解方法检测结果比对,无机化合物粉尘A、B组结果较接近,有机化合物粉尘A、B组结果对比有差别,但有机化合物粉尘经B组消解方法处理后,所得检测结果较为接近实际含量。游离SiO_2滤液第1次过滤收集回收率为61.0%～86.3%,第2次滤液过滤收集合并2次滤渣回收率为98.6%～99.5%。结论不同性质粉尘样品可以针对性地选择消解方法进行分析测定。焦磷酸法消解温度可以控制在240～250℃范围内保持15min进行消解。颗粒≤2μm的游离SiO_2滤液过滤收集时选择滤纸孔径在<2μm的定量滤纸或采用二次滤液收集合并灰化。