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Influence of coal thermoplastic properties on coking pressure generation: Part 2 - A study of binary coal blends and specific additives

机译：煤热塑性特性对焦化压力产生的影响：第2部分-二元煤混合物和特定添加剂的研究

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摘要

A number of coal blends and pitch/coal blends were evaluated using rheometry, thermogravimetric analysis and microscopy to confirm and further elucidate the coking pressure mechanism previously proposed by Duffy et al. (2007) [1]. We confirm that blending a low rank, high fluidity, low coking pressure coal, with a high rank, low fluidity, high coking pressure coal can significantly reduce the coking pressure associated with the latter. Interestingly, blending does not necessarily result in a fluidity that is midway between that of the two coals; sometimes the fluidity of the blend is less than that of the low fluidity coal, especially when the coals are significantly different in rank. This occurs because the increase in complex viscosity (η~*) through resolidification of the low rank, high fluidity coal counteracts the reduction in η~* resulting from softening of the high rank, low fluidity coal. It has also been confirmed that the η~* of the resultant blend can be estimated from the η~* of each component coal using a logarithmic addi-tivity rule commonly employed for polymer blends.rnPolarised light microscopy has indicated that the degree of mixing between coals of different rank is minimal, with fusion restricted to the particle surface. It is therefore inappropriate to think of such a coal blend in the same way as a single coal, since each component coal behaves relatively independently. This limited fusion is important for understanding the coking pressure mechanism for blends. It is proposed here that the lower rank coal, which softens at lower temperature, is able to expand into the interparticle voids between the high rank coal that is yet to soften, and these voids can create channels for volatiles to traverse. Then, and importantly, when the high rank coal begins to expand, the pore structure developed in the resolidified structures of the low rank coal can facilitate removal of volatiles, while the resolidified material may also act as a suitable sorbent for volatile matter. This is considered to be the primary mechanism by which coal blending is able to alleviate coking pressure, and applies to addition of inert material also.rnAddition of a coal tar pitch was found to increase fluidity but also to extend the thermoplastic range to lower temperatures. This caused an increase in the swelling range, which was accompanied by a long plateau in η~*, a feature which has previously been observed for certain high fluidity, high pressure coals. Elasticity and η~* at the onset of expansion were also higher for both the pitch impregnated coals and the high pressure blends, which supports previous findings for singly charged high pressure coals, and confirms the potential use of such criteria for identifying potentially dangerous coals/ blends.
机译：使用流变仪，热重分析和显微镜技术评估了许多煤混合物和沥青/煤混合物，以确认并进一步阐明Duffy等人先前提出的焦化压力机理。 （2007）[1]。我们确认，将低等级，高流动性，低焦化煤与高等级，低流动性，高焦化煤混合可以显着降低与后者相关的焦化压力。有趣的是，混合不一定导致流动性介于两种煤之间。有时，混合物的流动性要比低流动性的煤小，尤其是当煤的等级明显不同时。这是因为低级高流动性煤的再凝固引起的复数粘度（η〜*）的增加抵消了高级低流动性煤的软化导致的η〜*的降低。还已经证实，可以使用聚合物共混物常用的对数加和法则，从每种组分煤的η〜*估算出最终混合物的η〜*。偏光显微镜表明，两者之间的混合度不同等级的煤极少，其熔化仅限于颗粒表面。因此，以与单一煤相同的方式来考虑这样的混煤是不合适的，因为每种成分的煤的行为都相对独立。这种有限的熔融对于理解共混物的焦化压力机理很重要。在此提出，在较低温度下软化的较低等级的煤能够膨胀到尚未软化的较高等级的煤之间的颗粒间空隙，并且这些空隙可以形成用于挥发物穿过的通道。然后，重要的是，当高级煤开始膨胀时，在低级煤的再凝结结构中形成的孔结构可以促进挥发物的去除，而再凝结的材料也可以充当挥发性物质的合适吸附剂。这被认为是掺煤能够减轻焦化压力的主要机理，并且也适用于添加惰性材料。发现添加煤焦油沥青可以增加流动性，而且可以将热塑性塑料的范围扩展至较低的温度。这导致溶胀范围增加，并伴随着η〜*的长期平稳，这是以前对于某些高流动性，高压煤所观察到的特征。沥青浸渍煤和高压混合煤的膨胀开始时的弹性和η〜*也都较高，这支持了以前对单装高压煤的发现，并证实了使用这种标准来识别潜在危险煤/混合。

著录项

  • 来源
    《Fuel》 |2010年第7期|p.1600-1615|共16页
  • 作者

    John J. Duffy; Merrick R. Mahoney; Karen M. Steel;

  • 作者单位

    Nottingham Fuel and Energy Centre, School of Chemical and Environmental Engineering, The University of Nottingham, Nottingham NG7 2RD, United Kingdom;

    BHP Billiton Technology, Newcastle Technology Centre, P.O. Box 188, Wallsend 2287, Australia;

    rnNottingham Fuel and Energy Centre, School of Chemical and Environmental Engineering, The University of Nottingham, Nottingham NG7 2RD, United Kingdom School of Chemical Engineering, The University of Queensland, St Lucia 4072, Australia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    coal; coking pressure; rheology;

    机译：煤;焦化压力流变学;

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