容重法确定原料的颗粒级配

本文根据紧密堆积理论，结合生产实际，运用容重法原理确定合理的颗粒级配并讨论了其应用。     

玻璃原料颗粒度对平板玻璃熔制质量的影响

配合料的颗粒级配对玻璃产品质量的好坏具有明显的影响。原料颗粒级配的控制是玻璃生产质量控制的重要组成部分。本文通过大量的实验和理论研究，讨论了砂岩、纯碱、长石、白云石、石灰石等玻璃原料颗粒度对玻璃熔制质量的影响，对实际生产具有指导意义。     

不同粉磨工艺水泥颗粒级配的研究及评价

近年来，水泥的颗粒级配越来越受到人们的重视，尤其是新标准实施后水泥应用过程中出现的一些新问题，如在相同配比下，新拌混凝土裂纹增加，和易性变差，水化速率过快等[１]，更引起了人们对水泥颗粒组成的关注，也使人们意识到传统的细度控制已很难满足现代水泥应用技术发展的需要。但新的颗粒级配组成如何，生产过程又如何进行控制，目前报道不多。至于不同粉磨系统的颗粒级配，其深入研究的也不多。而我国开路系统和闭路系统的水泥颗粒级配从前人们只是从８０μm筛余和工艺流程上意识到两者的差别，很少做量的测试，这给下一步颗粒级配…     

坯体粉料性能对坯体干法混色技术的影响

坯体干法混色技术是一种先进的陶瓷坯体混色技术,在通体纹理的坯体生产中优势明显。但此工艺技术对坯体粉料参数要求严格,实验通过研究坯体粉料的含水率、颗粒级配、容重3个主要生产参数,为坯体干法混色技术的稳定生产提供支撑。     

玻璃用硅砂的应用探索

针对本公司现用三种不同产地的硅砂,将三种不同产地的硅砂按照一定颗粒级配配制成配合料,通过高温熔制实验制成样品,观察样品中未熔颗粒,确定熔化质量,探索对比三种硅砂的熔化工艺,为实际生产提供参考。     

Φ2.2×7.5m水泥磨采用逐渐增大级配的生产效果

0引言水泥粉磨工艺,确定研磨体级配广泛采用的是“两头小、中间大”的配球方法,它是减少两头钢球的配比,增加中问钢球的搭配,这种级配方法水泥磨应用较多。生料磨与水泥磨、开路磨与闭路磨、长磨与短磨,因生产工艺和设备选型不同,研磨体级配的方法不相同,水泥粉磨系统采用何种级配,对磨机产量影响较大,如何提高水泥颗粒有效利用率至关重要,它对水泥性能、强度影响较大。从优化水泥粉磨工艺,确定合理级配,在2004年ZJ厂送样对水泥颗粒级配进行检测,结合粉磨循环负荷、选粉效率确定了“逐渐增大”的级配方案,以下对比不同的研磨体级配,对水泥颗粒及物理性能的影响,其中所用熟料的强度等级均为52．5MPa左右,混合材品种掺入量相同。     

白云石粒度级配对平板玻璃熔制的影响

白云石是平板玻璃生产中的主要原料，它的颗粒度级配对本合料的质量存在明显的影响。应用高温熔制，澄清，均化实验以及Ｘ－射线衍射分析等手段研究具有不同白云石颗粒级配的配合料的熔制过程，从中找出优化的白云石颗粒级配方案，并从理论上加以探讨。     

水泥颗粒级配分析的实践

通过对激光粒度分析仪测出的水泥颗粒级配数据进行分析,结合水泥生产实际中遇到的问题,初步探讨了水泥颗粒级配数据,分析了其在调整优化标准稠度需水量、强度以及选粉机选粉效率等方面的应用。实践表明,水泥颗粒级配分析在水泥生产中起着越来越重要的作用。     

砂砾级配抗压性能研究

为了解决路基基层砂砾路用性能,确定合理的砂砾级配参数。对天然的砂砾石进行了筛分及级配,并通过实测砂砾空隙率与抗压实验研究。实验表明:全部为大颗粒砂砾以及全部为小颗粒砂砾的压碎指标要比连续级配砂砾的压碎指标大得多,而在连续级配砂砾中空隙率越大,压碎指标越小。     

均匀设计在煤矸石充填材料颗粒级配试验中的应用

多因素多水平采用均匀设计方法具有布点均匀、代表性好、使用方便等优点。作者采用U9（9^6）均匀设计方法对充填材料的颗粒级配确定进行了实验研究，确立了较优的颗粒组成，在此颗粒级配下，可使充填材料获得高的堆积密度和强度；在一定固相含量条件下，可使充填材料表观粘度明显降低．具有较好的工作性能。     

Evolution of asphaltene floc size distribution in organic solvents under shear

A mathematical model was developed on the basis of population balance to analyze experimental data on asphaltene floc size distribution in a coagulating suspension. Experiments were carried out in a Couette device under a laminar flow condition. Floc size distributions were measured on-line using optical microscopy and image analysis. The aggregation behavior of asphaltenes was investigated by monitoring the size distribution of flocs for various intensities of agitation (i.e., shear rate, G), solvent composition (i.e., ratio of toluene to n-heptane in the solution, T:H) and particle contents (i.e., volume fraction of particles, ?). The results showed that (i) the floc size distribution can be predicted using a population balance approach, (ii) a steady-state mean floc size is reached for a given shear rate, and (iii) this steady-state floc size increases as ? is increased or T:H is reduced. The relative rates of shear-induced aggregation and fragmentation determine the steady-state size distribution. Similar floc size distributions were obtained at steady state for various shear rates, indicating that the width of the size distribution is independent of shear. However, the experimental observations indicate that the steady-state floc size distribution depends on asphaltene concentration and solvent composition.     

Modelling the Effective Thermal Conductivity in Polydispersed Bed Systems: A Unified Approach using the Linear Packing Theory and Unit Cell Model

A comprehensive, unified approach, using the Linear Packing Theory and Unit Cell Model, is proposed for calculating of the effective thermal conductivity of polydispersed packed beds. In this new approach, the effect of packing density is incorporated by the use of (i) an initial porosity to take into account the packing of mono‐sized particles, and (ii) the packing size ratio as a measure of the particle‐particle interaction. The proposed approach was validated with the experimental measurements of binary and ternary beds. This new approach demonstrates that the effective thermal conductivity of beds composed of polydispersed particles can be simulated for any composition without the need to measure the in situ porosity.     

A generalized model to predict the viscosity of solutions with suspended particles. IV. Determination of optimum particle-by-particle volume fractions

A new approach has been introduced to establish the optimum composition for all particles within a mixture or suspension to achieve the optimum packing fraction, φ_n, and/or the minimum viscosity, η. The derivation to obtain the optimum particle volume fraction assumed that a previously developed optimum composition for binary particles applied to any two particle volumes V_i and V_j in the mixture. The composition of the maximum packing fraction for a mixture of more than two particles was then assumed to be calculable from the optimized relationship of each separate binary pair of particle volumes V_i and V_i in the mixture. This derived equation was successfully shown to predict the optimum particle-to-particle composition of McGeary's experimentally measured binary, tertiary, and quaternary mixtures. The difference between the calculated and measured volume fractions was no greater than 3.85% and, in most instances, was significantly less than 3.85%. The maximum packing fractions, φ_n, determined experimentally by McGeary, were also successfully predicted to better than 3.26%. Theoretical particle-to-particle volume fractions evaluated for an example pressure-agglomerated latex appeared to predict the particle-size distribution only within a narrow range of particle sizes. However, when the theoretical and experimental results were evaluated as a function of the number of particles for each particle diameter, it was apparent that the agglomerated distribution closely approximated the theoretical optimum distribution above 600 Å. Agreement with theory below 600 Å was unsatisfactory. The decrease in viscosity of the example agglomerated latex appeared to have been enhanced as the optimum theoretical particle-size distribution was approached. © 1994 John Wiley & Sons, Inc.     

The continuous mixing of segregating particles

Earlier work has shown that when non-segregating particles are fed to a continuous mixer the fluctuations in the output stream can be predicted if the input fluctuations and residence time distribution for the mixer are known. In this paper the work is extended to particles which segregate in the mixer. The amount of segregation occurring is characterised by a steady state variance, that is the variance of composition fluctuations in the exit stream when a mixture containing no fluctuations is fed to the mixer. It is shown that when known composition fluctuations are fed to the mixer the variance for the output stream can be predicted by adding together the steady state variance and the variance predicted for no segregation, using the residence time distribution. Predicted variances agree with the experimental results obtained for a continuous fluidized bed mixer.     

Filtration Efficiency of Non-Uniform Fibrous Filters

Although theoretical models of the filtration efficiency of fibrous filters are typically based on a single type of fiber in an ordered array, many actual fibrous filters comprises fibers that are inherently randomly distributed. It is desirable to be able to estimate the filtration efficiency of such non-uniform fibrous filters from their composition arrangement and the filtration property of individual fibers. Toward that end, we approximate the filter system as a series of cells comprising individual fibers with random distribution, deviating from the homogeneity assumption in the classical models. With better characterization of the filter structure based on the Voronoi diagram, we theoretically revisit filtration efficiency by the top-down (TD) approach and the bottom-up approach. The proposed models are compared with the existing experimental and numerical results under different fiber volume fractions, indicating the high accuracy of the TD model for the filtration of submicron aerosol particles. The influence of the degree of randomness of fiber distribution on filtration efficiency is also quantified.

Copyright 2015 American Association for Aerosol Research     

A mixed Weibull model for size reduction of particulate and fibrous materials

This paper describes a simple alternative to the classical population balance breakage model, which characterizes and controls the size distribution of particles submitted to a reduction process. The new approach is based on cumulative distribution functions of mixed random variables. Results indicate that a Weibull mixture distribution function adequately models the size of particles submitted to various breakage processes. The model was further applied to experimental reduction processes with apparently random breakage probability and yielded good estimates of the unbroken particle and fragment distributions. Use of these results for direct and indirect prediction of the size alteration under dimensional reduction processes is discussed.     

Simulation of compositional profile in functionally graded materials

The development of a polymer based functionally graded material (FGM) of desired composition profile by the centrifugation technique requires control on centrifugation, size, shape, and concentration of suspended particles, time, viscosity variation of polymerizing fluid, etc. A simulation was conducted to observe the compositional variations with time at different places of FGM, using a modified terminal velocity equation for particle movement in polymerizing fluid. It was further modified for the particles having different sizes. The simulation demonstrated two graded‐composition profiles each one in low concentration region from where particles were moved to the other part of sample and second high concentration profile in which particles entered to increase the concentration. The third region situated between the two composition profiles was observed as that of uniform distribution of particles and the length of this region can be controlled by adjusting the size of the centrifuged sample. The simulation was compared with the experimental results of FGM having SiC particles in polysulphide epoxy resin. POLYM. ENG. SCI. 46:1660–1666, 2006. © 2006 Society of Plastics Engineers     

A mathematical model of ash formation during pulverized coal combustion

A mathematical model of ash formation during high-rank pulverized coal combustion is reported in this paper. The model is based on the computer-controlled scanning electron microscope (CCSEM) characterization of minerals in pulverized coals. From the viewpoint of the association with coal carbon matrix, individual mineral grains present in coal particles can be classified as included or excluded minerals. Included minerals refer to those discrete mineral grains that are intimately surrounded by the carbon matrix. Excluded minerals are those liberated minerals not or at least associated with coal carbon matter. Included minerals and excluded minerals are treated separately in the model. Included minerals are assumed to randomly disperse between individual coal particles based on coal and mineral particle size distributions. A mechanism of partial-coalescence of included minerals within single coal particles is related to char particulate structures formed during devolatilization. Fragmentation of excluded minerals, which is important particularly for a coal with a significant fraction of excluded minerals, is simulated using a stochastic approach of Poisson distribution. A narrow-sized sample of an Australian bituminous coal was combusted in a drop-tube furnace under operating conditions similar to that in boilers. The particle size distribution and chemical composition of experimental ash were compared to those predicted with the model. The comparisons indicated that the model generally reflected the combined effect of coalescence of included minerals and fragmentation of excluded minerals, the two important mechanisms governing ash formation for high-rank coals.     

鼓泡流化床内高灰煤气化过程的颗粒尺度特性研究

基于多相流体质点网格方法(MP-PIC)对高灰煤在三维鼓泡流化床气化过程进行了数值模拟研究。在欧拉-拉格朗日框架下将气相和固相分别视作连续介质和离散相处理。首先,将模拟得到的出口处气体组分结果与实验数据进行对比,实验数据与模拟结果具有良好的一致性。其次,研究了煤颗粒在气化炉内的温度、传热系数、速度和停留时间,从颗粒尺度揭示了鼓泡流化床气化炉内的颗粒分布特性和气固流动特征。结果表明:在气化炉入口附近煤颗粒与床层温差最大,传热系数最大;由于流化床内强非线性的气固流动,床中煤温度和传热系数的空间分布不均匀;煤颗粒和床料的瞬时速度具有稳定的波动幅度,其中垂直方向速度波动最明显,且煤颗粒的瞬时速度比床料的瞬时速度略大;由于颗粒间的剧烈碰撞,延长了煤颗粒停留时间。此外,对鼓泡流化床中煤气化过程颗粒尺度的研究,有助于深入了解固体颗粒的流动行为以及气固相相互作用特性,对鼓泡流化床反应器的设计优化具有重要意义。     

Measurement of size and shape distributions of particles through image analysis

The size and shape of particles can be described using a 2D particle size distribution (PSD) where two characteristic lengths define each particle in the population. The determination of 2D PSDs based on microscopic pictures of particles in suspension is studied. The experimental data are represented as an axis length distribution (ALD) that can be extracted from a series of microscopic pictures by a fully automated image analysis. The problem of finding the underlying bi-dimensional PSD is stated as an optimization problem. For the solution a genetic algorithm is used. The approach is tested on simulated ALDs, as well as on an experimentally measured ALD obtained from carbon fiber particles.