破碎煤矸石粒度与热值分布研究

通过研究不同方式破碎煤矸石中存在的热值随粒度减小而增大的现象,分析了破碎煤矸石粒度与热值分布间的相互关系。结果表明,煤矸石破碎后,不同粒级发热量随粒度变化而重新分布,呈负相关关系,且细粒级比粗粒级发热量提高1倍以上,为煤矸石的破碎分选提供了依据。     

煤粉粒度对元宝山褐煤燃烧特性的影响

为了给实际工程应用中煤粉粒度的确定提供参考,采用热重分析的方法,研究煤粉粒度对元宝山褐煤燃烧特性的影响.对燃烧热重曲线特征参数分析表明,粒度减小,煤粉着火提前、燃尽时间缩短;粒度减小,可燃指数C和综合燃烧指数S增加,表明煤粉燃烧性能得到改善;用Coats-Redfern方法求解燃烧反应的动力学参数,燃烧反应动力学分析表明,元宝山褐煤的热天平燃烧反应为一级反应;在最大燃烧速度对应温度前后燃烧过程分成两个阶段;粒度减小,各段燃烧反应的表观活化能和质量平均表观活化能均降低.减小煤粉粒度对改善煤粉燃烧性能是有利的.     

一种评价煤泥颗粒凝聚效果的激光粒度分析方法

为了实现对煤泥颗粒凝聚效果的量化评价,使用了一种激光粒度分析的方法.通过激光粒度分析仪,测试煤泥颗粒在不同转速和不用浓度的Ca2+或Na+溶液中的粒度分布.结果表明:Ca2+比Na+更容易使煤泥颗粒凝聚,Ca2+浓度越高,煤泥颗粒越容易凝聚.在转速为1 000rpm和Ca2+浓度大于5mmol/L时,颗粒的凝聚效果最好,d90可达到700μm以上.根据煤泥颗粒粒度分布的d10,d50和d90的大小,可实现对颗粒凝聚效果的量化分析.     

Experimental research into the effect of gas pressure,particle size and nozzle area on initial gas-release energy during gas desorption

Coal and gas outburst is a violent disaster driven by released energy from gas desorption. The initial expansion energy of released gas(IEERG) is a new method to predict coal and gas outburst. In this paper,an instrument for IEERG measurement was developed. Compared with previous setups, the new one which is equipped with three convergent nozzles and quick-release mechanism gets improved in data acquisition and gas sealing and releasing performance. To comprehensively know the effect of gas pressure, particle size, and nozzle area on IEERG, a series of experiments were carried out with this new setup.The variable control test results indicated that the gas pressure-IEERG curves remain the linear trend and the particle size-IEERG curves maintain the negative exponential trend for nozzle areas at 1.13, 2.26, and3.39 mm2, respectively. The increase in nozzle area leads to deceases in value of IEERG and absolute value of slope of fitting curves in each test. In addition, the orthogonal experiment showed that the influence of gas pressure, nozzle area, and particle size on IEERG decreases in turn. Only gas pressure had a marked impact on IEERG. This work offers great importance in improving the accuracy of prediction of coal and gas outburst.     

Development of a mass model in estimating weight-wise particle size distribution using digital image processing

Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumulative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, making it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters(such as major axis, minor axis, and equivalent diameter) on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape parameters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size(D-50) being just 0.4%. However, sieve-size of smaller particles(20 mm) strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles(20 mm) are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent(w.r.t cumulative frequency). The method proposed in this paper provides a time-efficient way of producing accurate(up to 99%) mass-wise PSD using digital image processing and it can be used effectively to replace the mechanical sieving.     

用灰色系统理论研究粒径分布对水泥抗压强度的影响

把实际水泥体系的粒径分布看作灰色系统,测定了不同粒径分布水泥的各龄期抗压强度,用灰色系统理论的关联度计算法定量表示了不同大小颗粒对不同龄期强度贡献的差异,提出了在实际生产中寻求最佳粒径分布的一个指导性原则。