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首页> 外文学位 >Rock dust surface chemistry modifications for eliminating cake formation and improving dispersion in coal dust explosion mitigation applications.
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Rock dust surface chemistry modifications for eliminating cake formation and improving dispersion in coal dust explosion mitigation applications.

机译：岩石粉尘表面化学改性，可消除结块形成并改善煤粉尘爆炸缓解应用中的分散性。

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摘要

Rock dust has been historically applied to mitigate the coal dust explosion in either dry or wet form. Dry rock dust performs best in inerting the potential coal dust explosion due to the greatest dispersive properties. However, it undesirably exposes underground coal miners to respirable dust particles which imposes a severe health danger. Wet dust application is able to significantly reduce the floatable dust particles but another problem associated with caking is predominant. Caking phenomenon is usually used to describe the change of free-flowing bulk solids into agglomerated chunks. Unfortunately, the environmental conditions of an underground mine have the potential to cause caking of the rock dust, especially for wet dust application, which reduces the dispersive characteristics needed for effective explosion mitigation and is also the focus of the present study. Surface modification of rock dust to generate a hydrophobic surface is believed to alleviate the caking problem by allowing instant water drainage and eliminating the formation of water and solid bridges.;Surface modification of rock dust was evaluated in the present study with a series of potential modifying reagents including oleic acid, sodium oleate and stearic acid. The modification efficiency in terms of measured contact angle, zeta potential and dispersibility values was investigated with sodium oleate generating the best modification effect. Dispersants were investigated as well in the present work aiming to further increase the particles dispersibility in addition to the excellent hydrophobization effect generated by sodium oleate. However, dispersibility test results indicated that the adsorption of dispersant and sodium oleate was competitive. The preferential adsorption of dispersants over oleate deteriorated the surface hydrophobicity of particles and the dispersibility was decreased as a result.;As anticipated, dry rock dust always provided the best dispersibility with almost 95% of the dust remaining in suspension at a dispersion time of 30 seconds. The percentage dust dispersion values of sodium oleate treated rock dust was increased to as high as 71% in contrast to 47% of untreated wet rock dust and the explosion potential was correspondingly reduced by almost 83%. The effect of sodium oleate was further studied as a function of reagent concentration to determine the optimum application condition. The dispersibility of rock dust particles was initially increased until the application of 0.1 wt% sodium oleate, after which it slightly decreased up to 0.5 wt% oleate. When the concentration was above 0.5 wt%, the dispersibility of dust particles substantially decreased to a value lower than the value obtained for regular wet dust. The optimum sodium oleate concentration was thus determined at approximately 0.1 by weight of rock dust particles with a corresponding contact angle of around 110 degrees.;The pivotal of rock dust modification efficiency is its long-term stability which can be corroborated by irreversible chemical adsorption rather than the short-term physical adsorption. Therefore, the fundamental adsorption mechanism of sodium oleate on rock dust surface was continuously investigated by means of using surface tension measurements, FTIR, Thermogravimetric, SEM analyses and constructing the species distribution diagram. Based on the surface tension measurements and calculated apparent surface area occupied by per oleate molecule, the monolayer adsorption of oleate on dust surface was proposed with oleate concentration falling between 0.1-0.15 wt% which guarantees the long-term surface modification efficiency. Calcium oleate started precipitating out of bulk solution and depositing on the dust surface when the oleate concentration was above 0.15 wt% which became more predominant under high oleate concentration. Super hydrophobic particles together with nucleated calcium oleate nanoparticles tend to increase particles aggregation significantly through attractive hydrophobic particle-particle interactive force, which renders the particles more agglomerated instead of dispersed.;Systematic and economic evaluation of the wet form rock dusting process in underground coal mine applications was conducted at the end to determine the safety effects, potential benefits and improvement for future implementation. Suggestions for future work were given as well to shed light on the dusting process together with rock dust surface chemistry modification.
机译：从历史上讲，岩石粉尘已被用于减轻干粉或湿粉形式的煤粉爆炸。由于具有最大的分散性，干岩粉在抑制潜在的煤粉爆炸方面表现最佳。然而，它不希望地使地下煤矿工人暴露于可吸入的尘埃颗粒中，这具有严重的健康危险。湿粉尘的施加能够显着减少漂浮的粉尘颗粒，但是与结块有关的另一个问题仍然很突出。结块现象通常用于描述自由流动的散装固体转变为团块的过程。不幸的是，地下矿山的环境条件有可能导致岩尘结块，特别是对于湿尘应用，这降低了有效缓解爆炸所需的分散特性，这也是本研究的重点。人们认为，通过对岩石粉尘进行表面改性以产生疏水性表面，可以通过立即排水并消除水和固体桥的形成来缓解结块问题。本研究对岩石粉尘的表面改性进行了一系列潜在的改性研究试剂包括油酸，油酸钠和硬脂酸。研究了在测得的接触角，ζ电势和分散性值方面的改性效率，其中油酸钠产生了最佳的改性效果。在目前的工作中，还对分散剂进行了研究，目的在于除油酸钠产生的优异疏水作用外，还进一步提高颗粒的分散性。然而，分散性测试结果表明，分散剂和油酸钠的吸附具有竞争性。分散剂优先于油酸酯的吸附降低了颗粒的表面疏水性，结果降低了分散性。如所预期的，干岩粉尘始终提供最佳的分散性，在分散时间为30时，几乎有95％的粉尘保留在悬浮液中秒。与未处理的湿岩石粉尘的47％相比，油酸钠处理过的岩石粉尘的百分分散值增加到高达71％，爆炸电位相应降低了近83％。进一步研究了油酸钠的作用与试剂浓度的关系，以确定最佳的应用条件。最初增加了岩石粉尘颗粒的分散性，直到添加了0.1 wt％的油酸钠，此后它才逐渐降低，直至达到0.5 wt％的油酸钠。当浓度高于0.5重量％时，粉尘颗粒的分散性显着降低至低于常规湿粉尘获得的值。因此，确定的最佳油酸钠浓度为约0.1重量％的岩粉尘颗粒，相应的接触角约为110度。;岩尘粉改性效率的关键在于其长期稳定性，这可以通过不可逆的化学吸附得到证实比短期的物理吸附。因此，利用表面张力测量，FTIR，热重分析，SEM分析以及构造物种分布图，不断研究了油酸钠在岩石粉尘表面的基本吸附机理。根据表面张力的测量结果和计算出的每个油酸酯分子占据的表观表面积，提出了油酸酯在粉尘表面的单层吸附，其油酸酯浓度在0.1-0.15 wt％之间，从而保证了长期的表面改性效率。当油酸盐浓度超过0.15重量％时，油酸钙开始从本体溶液中沉淀出来并沉积在粉尘表面上，在高油酸盐浓度下油酸钙变得更加占优势。超疏水颗粒与有核油酸钙纳米颗粒一起，通过吸引的疏水颗粒-颗粒相互作用力趋向于显着增加颗粒聚集，这使颗粒更加团聚而不是分散。;地下煤矿湿式岩石除尘过程的系统和经济评价最后对应用进行了确定，以确定安全效果，潜在利益和改进措施，以供将来实施。还提出了今后工作的建议，以阐明除尘过程以及岩石粉尘表面化学改性。

著录项

  • 作者

    Huang, Qingqing.;

  • 作者单位

    University of Kentucky.;

  • 授予单位 University of Kentucky.;
  • 学科 Mining engineering.;Chemical engineering.;Engineering.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 182 p.
  • 总页数 182
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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