刍议煤矿采掘作业中粉尘污染及治理

煤矿井下粉尘污染既是一个劳动保护问题,也是一个环境保护问题。文章根据煤矿井下采掘粉尘的特性及其危害和对井下空气污染的状况,详细分析了煤矿井下的主要尘源和尘量分布。提出针对井下采掘各产尘源的治理措施。并对煤矿井下的防尘管理做了科学的展望。通过对粉尘污染的治理,改善煤矿工人的作业环境,实现清洁生产,降低矿工职业病发病率,提高煤矿生产效益和经济效益。     

用X射线衍射测定呼吸性粉尘中游离α-SiO2

采用美国Minusi-5和德国α—Fe2O3的标样，以及直径为40mm过氯乙烯纤维和丙纶滤膜，DXFC-1呼吸性粉尘采样器，模拟作业现场的条件，在发尘室内发尘和采样。选取滤膜增重0．1～3．5mg的5～7个试样，测定衍射积分强度，并用Si(111)晶面衍射积分强度进行归一化处理，按外标法制定定标曲线。根据标样按1：1比例配制试样，进行验证。实验结果表明，测定呼吸性粉尘中游离α-SiO2含量，其相对误差小于10％，灵敏度不高于0．02mg。     

南山煤矿粉尘危害防治

煤矿井下粉尘危害主要包括煤尘、岩尘、水泥尘等，本文阐述了南山煤矿井下粉尘治理所采取的综合措施及个体防护的方式方法。     

颗粒运动对衍射光空间分布的影响

为了研究激光粒度测量颗粒分布时,测量区中处于运动状态的颗粒对衍射光空间分布和粒径测量结果的影响,从理论上分析了颗粒运动对衍射光的影响。结果表明:颗粒运动并不影响衍射光的空间分布,只改变衍射光的时域分布,因此对于颗粒粒径测量结果不产生影响。     

氧化锆催化剂粉末粒度及其分布的测定方法

在相同试验条件下,用水做分散介质,用激光粒度测定仪测定三个氧化锆催化剂粉末样品的粒度及粒度分布,比较了三个样品的粒径大小和粒度分布情况.试验结果显示,氧化锆2号样品粒度最小,粒度分布集中,1号样次之,3号样粒度最大,粒度分布最分散.     

气流磨尾尘的超细粉碎

用气流磨加工碳化硅磨料时,约有5%-15%的物料变成了尾尘.这部分碳化硅微粉由于粒度分布范围很宽,无法直接利用.本实验研究对气流磨碳化硅尾尘用搅拌磨粉碎进行了探讨.实验研究了不同研磨时间粉尘的纯度变化;分散剂对粒度变化的影响以及不同研磨时间,微粉的粒度、粒度分布的变化关系,实验结果证明气流磨尾尘经过搅拌磨研磨可以得到分布窄、单峰的理想微细粉体;随着研磨时间的增加,粉体纯度下降;磷酸盐水分散剂可以促进研磨的进程.     

浅谈煤矿掘进工作面的防尘举措

掘进工作面是煤矿井下最主要的产尘点之一。随着机械化程度的不断提高,巷道不断加大加长,采用单一的降（除）尘技术和措施无法满足生产需要。本文从掘进工作面粉尘的构成人手,确定了粉尘产生的根源,通过对截齿破煤机理、煤层性质、工作结构与参数、掘进机工作方式等方面的研究、分析,确立了掘进防尘的举措。     

粉体物料的粒度测量

本文着重介绍了激光粒度分析仪的工作原理,并对不同的粉体物料如拆迁废料、道路尘以及粉煤灰的粒度分布实验数据进行了比较分析,分析它们各自的特点,为进一步研究大气粉尘的毒理学特性提供科学依据。通过实验分析得出:道路尘,拆迁废料的颗粒大小比较接近,一般在90μm~160μm区间内的颗粒比较多;粉煤灰的颗粒微分分布比较均匀,没有过大或过小变化,其颗粒非常的小。     

煤矸石、页岩砖厂粉尘的治理

粉尘是由固体物质在破碎、研磨过程中分裂而成的单个尘粒所组成,通常具有与母料相同的化学成分。漂尘粒度一般在0.2～200μm之间,在煤矸石粉尘中,游离二氧化硅含量一般在30%～40%之间。砖厂工人经常生活在这样粉尘浓度较高的环境中,容易引起肺组织产生广泛的纤维性变化和形成矽肺结节。砖瓦行业为了防止矽肺病的发生,在破碎、原料运输、搅拌等工艺过程中,采用有效的方法,防止粉尘的产生和扩散,从而改善工人的工作环境,以提高粉尘“以防为主,防治结合”的自觉性。图1防尘总体示意1—粉碎机;2—旋风储存器;3—垂直回风管;4—出料管;5—回风斜…     

几种常见粒度分析方法的比对研究

正一、概述颗粒的粒度分析方法很多。随着科技的进步,有些方法被逐步淘汰,有些方法得到了改进和发展(如激光衍射法、动态光散射法等),并在生产和科研中得到了广泛应用(如激光衍射法、显微图像法、电阻法、光透沉降法、筛分法等)。本文选择了目前常见的激光衍射法、显微图像法、电阻法、光透沉降法4种不同测量原理的粒度分析方法,邀请国内实验室合作进行比对实验,对粒度分布范围在(1~100)μm的玻璃微珠颗粒进行粒度分析,对各类统计粒径进行数据比对,以验证这几种粒度分析方法的一致性与可比性。     

Experimental investigation of the wetting ability of surfactants to coals dust based on physical chemistry characteristics of the different coal samples

To select suitable surfactant as water-spray additive to improve dust suppression efficiency, six types of coal sample (lignite, long flame coal, non-caking coal, gas coal, coking coal, and anthracite) were selected from some typical mining areas in China, the influence of the physical chemistry characteristics of coal samples on the wetting ability of surfactants to the coals dust was investigated. Their proximate composition, ultimate content, chemical structure, surface morphology, pore structure parameters, and contact angle were determined. Three kinds of anionic surfactants – Sodium Alcohol Ether Sulphate (AES), Sodium Alpha-Olefin Sulfonate (AOS), Fatty Acid Methyl Esters Ethoxylate Sulfonate (FMES) – and one kind of nonionic surfactant – Coco Diethanolamide (CDEA) – were selected to carry out sedimentation experiments on the coal samples dust, to explore the main factors influencing the wettability of the coal samples dust. Among these factors, pore size is the main factor determining the wettability of coal dust, the contact angle decreases linearly (R² = 0.96) with pore size increase. The experimental results demonstrate that the following factors produce correspondingly increased wettability: higher moisture content, lower carbon content, higher oxygen content, more oxygen-containing functional groups, and increased pore size. In addition, the wettability of the six types of the coal samples dust shows a high-low-high trend with metamorphic degree increase, lignite has the strongest wettability, and the coking coal with the highest degree of metamorphism in the selected bituminous coal sample has the weakest wettability. Moreover, compared with nonionic surfactants, anionic surfactants have stronger wetting ability, but the same anionic surfactants have different wetting abilities to coal dust with different metamorphic degrees. AOS has stronger wetting ability to the dust of long flame coal, non-caking coal, and anthracite; AES has stronger wetting ability to the dust of lignite and coking coal; and FMES has stronger wetting ability to the dust of gas coal. The research results provide a theoretical basis for different coal mines to select suitable surfactants as water-spray additives to improve dust suppression efficiency.     

Size distribution of mineral aerosol: using light-scattering models in laser particle sizing

The size distribution of semitransparent irregularly shaped mineral dust aerosol samples is determined using a commonly used laser particle-sizing technique. The size distribution is derived from intensity measurements of singly scattered light at various scattering angles close to the forward-scattering direction at a wavelength of 632.8 nm. We analyze the results based on various light-scattering models including diffraction theory, Mie calculations for spheres with various refractive indices, and T-matrix calculations for spheroidal particles. We identify systematic errors of the retrieved size distribution when the semitransparent and nonspherical properties of the particles are neglected. Synthetic light-scattering data for a variety of parameterized size distributions of spheres and spheroids are used to investigate the effect of simplifying assumptions made when the diffraction model or Mie theory is applied in the retrieval.     

优化爆破参数提高块煤率的实验研究

为了控制黑岱沟露天矿煤层爆破中1.8m以上大块的产出率和10mm粒度以下煤的产率,提高优质煤的块煤率和产量,在分析煤岩爆破破碎机理及减少爆破药柱粉碎区途径的过程中,对爆破参数进行了优化,提出了将低密度铵油炸药应用于黑岱沟露天煤矿煤层爆破的方案。同时,对低密度铵油炸药和铵油炸药不同孔网参数、装药结构、填塞长度进行煤层爆破对比实验,分析了二者对块煤率、采掘效率及安全性的影响。结果表明:低密度铵油炸药能够实现炮孔内连续装药,其线装药密度低,有利于降低炸药单耗,爆炸能量传递更均匀,能有效减少末煤量,块煤率较铵油炸药提高了13.78%。确定了露天煤矿厚煤层爆破炸药单耗的最佳范围是0.176⁰.23kg/m3,可为露天煤矿煤层爆破设计提供依据。     

Experimental study on geometric parameters of pore structure and quantitative evaluation of complexity of pulverized coal with different metamorphic degrees

In order to quantify pore structure complexity of coal, the low pressure argon adsorption method (LP-ArGA) was used to study geometric parameters of pore structure and quantitative evaluation of complexity of pulverized coal. The results showed that the geometric parameters of pore structure of most single-particle coals showed an obvious downward trend with the decrease of particle size, indicating that the pore structure became simpler in the pulverization process. The weight value of equivalent matrix scale is the largest, which is 0.4871, indicating that it has the greatest influence on pore structure complexity. With the decrease of particle size, the composite evaluation index of complexity of 1#, 2#, 3#, 4#, 5# and 6# samples decreased by 52.4%, 61.1%, 86.3%, 42.1%, 74.6% and 39.9%, respectively. It indicated that particle size has an extremely influence on pore complexity characteristics of single-particle coal. With the decrease of particle size, the pore complexity characteristics of coal samples tended to be simple, on the contrary, they showed medium or complex characteristics. The model has important guiding significance for evaluating the same coal sample with different particle sizes, but there are still some deficiencies for different coal samples.     

Grain breakage under uniaxial compression using a three-dimensional discrete element method

Grain breakage in rockfill in civil engineering structures is the major cause responsible for settlement and collapse. It is inherently due to large grain size and angular shape of the grains. To model these features, a three-dimensional discrete element model of a breakable grain is presented hereafter. The model is able to reproduce grain breakage into rigid irregular fragments with conservation of the mass of the initial grain. Polyhedral shapes are chosen to represent the grains, and are divided into irregular tetrahedral fragments joined together by a cohesive law to enable breakage. This model is implemented in a Non-Smooth Contact Dynamics code. Single grain crushing tests are first conducted to capture the influence of mechanical and geometrical parameters of the model. The intra-granular cohesion defines the grain strength. The grain size and the size and geometrical disposition of subgrains can act in a competitive way, thus contributing to the definition of the grain strength, and in the validation of the scale of effect observed in this type of material: the bigger the grain, the lower its strength. The same grain model is then used to generate multi granular samples subjected to oedometric compression, where grains interact via contact and friction processes, with a uniform initial grain size distribution. The effects of grain breakage are investigated through the analysis on the macroscopic and microscopic scales, with a comparison with unbreakable grains samples. The ability of the model to reproduce physical laboratory tests is confirmed through the simulations.     

Electric arc furnace filter dust: Influence of organic material on the bulk density and flowability

In this study, the influence of condensed organic matter on the flowability and the bulk density of electric arc furnace (EAF) dust was investigated. The properties of the original dust samples containing some organic matter were compared with the properties of these samples after the removal of the condensed organic compounds by a deoiling procedure. The particle size distribution and the density of the three investigated dust samples were quite similar but the content of organic matter (TOC) was different. The values for the bulk density were lower for the original dust compared to the deoiled dust samples. The higher the TOC content, the higher the difference in the bulk density. Thus, the storage capacity of the dust silo was reduced by 9–17%. The flowability of all deoiled dust samples was very similar, whereas the flowability of the original dust was worse. The higher the TOC content, the worse the flowability. The average reduction of ff_c in comparison to the deoiled dust samples was 48, 38, and 17% for EAF dust samples with 0.65, 0.46, and 0.26% TOC, respectively. Evidently, the condensed organic matter on the dust particles reduces the flowability of the material. Therefore, the bulk density for dust with a higher TOC content is also lower.     

Modeling flow properties of fine dry powders using particle morphological properties and its effects on geometry of fly ash evacuation hoppers

This paper results from an ongoing effort to correlate the physical properties of powders at a fundamental level with their bulk behavior. Cohesion and unconfined yield stress are the measure of inter-particle forces of attraction in the bulk powder. The existing model for cohesion does not include important bulk properties, such as particle size distribution, tapped density, and prevailing applied stress. In the present paper, flow properties of 25 bulk solids (different cement and fly ash samples) have been evaluated using a ring shear tester and the products have been characterized according to their flowabilities. Models for cohesion and unconfined yield strength have been developed in this study by taking into account the effects of particle size distribution, tapped bulk density and pre-shear stress. The newly developed models have provided good fit to the experimental data. The effect of these flow properties on the design of hoppers have been investigated for fly ash samples collected from seven consecutive electrostatic precipitator (ESP) hoppers of a coal fired thermal power station. The results show that fly ash from the rear end ESP hopper would require higher amount of opening size compared to the first or second field of ESP to ensure proper mass flow condition is achieved at all the ESP hoppers.     

Influence of coal properties on dust suppression effect of biological dust suppressant

In order to study the effect and influencing factors of biological dust suppressant on secondary dust of coal dust, the biological dust suppressant was prepared with bacillus pasteurii and 0.6 mol/L urea-CaCl₂ solution. The experimental result shows that the yield of mineralized products of CC is the highest, reaching 81.11%, in bonding solutions with different calcium source and different concentration. For 5.0 g coal dust, 8 mL is the suitable spraying amount of bacteria solution and bonding solution. Biological dust suppressant has the best secondary dust suppression effect on coal dust with particle size above 200 μm. Moreover, it has the strongest effect on inhibiting secondary dust emission of lignite, and the weight loss rate of coal dust about 200 μm is only 0.84%. At the same time, the proportion of calcite crystals with the strongest thermal stability in mineralized products produced by MICP is higher. When the coalification degree of coal is lower, the effect of biological dust suppressant on secondary dust emission is better.     

Effects of statistics of cell’s size and shape irregularity on mechanical properties of 2D and 3D Voronoi foams

In the study of the mechanical properties of metallic foam, the relative density (or porosity) and the average size of cells are two key parameters of the meso-geometry, but it is also well known experimentally that the two parameters alone are not enough since the mechanical properties of metallic foams are different even with the same initial relative density and average cell size. In this paper, we have classified the irregularity of cells into two types to describe polygonal and polyhedral cells in 2D and 3D metallic foams, which are called size irregularity and shape irregularity, respectively. The former reflects the deviation of the size of a cell from the average cell size in the foam and the latter reflects the deviation of the shape of a cell from a circle with the same area (2D) or a globe with the same volume (3D). With the two kinds of definitions, effects of the irregularity of cells in aluminum foam on mechanical properties are investigated using the Voronoi tessellation technique and the finite element method. The well- designed 2D and 3D Voronoi models are constructed, of which the statistic distributions of size and shape irregularity are presented. The compression simulations of Voronoi-based models indicate that the yield stress of metallic foam is seldom affected by the size irregularity, but significantly affected by the shape irregularity. The more regular the foams, the higher will be their yield plateau at constant overall relative density and average cell size.     

Preparation of microbial dust suppressant and its application in coal dust suppression

To promote the application of microbially induced carbonate precipitation (MICP) technology for coal dust suppression, two urease-producing bacteria (SZS1-3 and SZS1-5) in a coal mine soil were screened. 16 s rDNA sequencing of these bacteria indicated sequences similar to those of Acinetobacter guillouiae CIP 63.46 and Staphylococcus caprae ATCC 35538, respectively. Strains SZS1-3 and SZS1-5 had their largest urease activity at the initial urea concentration of 0.5 mol/L, under slightly alkaline (pH = 9) and neutral (pH = 7) initial pH levels, respectively. Their final mineralized products were vaterite-type and calcite-type calcium carbonate. Although dust suppression results indicated that both bacteria can effectively bind coal dust particles, consolidated coal dust treated with SZS1-5 had a stronger resistance to wind and rain. The screening, mineralization and dust suppression potential analysis of these two urease-producing bacteria can provide reference for the application of MICP technology in coal dust suppression.