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Micro-properties of coal aggregates: Implications on hyperbaric filtration performance for coal dewatering

机译:煤骨料的微观性质:对高压煤脱水的过滤性能的影响

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The recovery of ultrafine coal can be enhanced significantly by flocculating the particles prior to dewatering. It is thus crucial to be able to quantify the effects of aggregated particles on the separation efficiency, of which they are still not fully understood. This study focused on the relationship between the micro-properties (size, structure, and strength) of flocculated coal particles and the characteristics of filter cakes obtained through hyperbaric filtration. Tools such as small angle light scattering and confocal scanning laser microscopy were used to determine the aggregate structure. The comparative bond strength of aggregates generated under different flocculation conditions was measured through a non-dimensional approach. The effects of these properties on specific cake resistance, saturation, and moisture content, as indicative of the filtration performance, were observed. It was found that floes generated using a moderate amount of flocculant dosage (60-100 g of polymer/tonne of coal) for this ultrafine coal (97 percent <35 mu m) optimised the properties of dewatered filter cakes. Although cakes composed of larger and stronger aggregates with more flocculant were found to have higher porosity, the effects on specific cake resistance and cake saturation were detrimental, possibly due to the increasing proportion of intra-aggregate pores that were harder to dewater. The trend was less noticeable at low filtration pressures where most of the dewatering occurred within the larger capillaries of the inter-aggregate zones. In addition, the presence of polymer molecules was responsible in absorbing residual moisture that could not be removed through mechanical means. Through a series of tests using pre-formed filter cakes, the amount of moisture retained by the flocculant was quantified to be approximately 10.2 mg of water for every addition of 1 g of polymer/tonne of coal, calculated per 100 g of filter cake produced from hyperbaric filtration in this case.
机译:通过在脱水之前絮凝颗粒,可以大大提高超细煤的回收率。因此,至关重要的是要能够量化聚集的颗粒对分离效率的影响,但对于聚集的颗粒仍没有完全了解。这项研究的重点是絮凝的煤颗粒的微观性质(尺寸,结构和强度)与通过高压过滤获得的滤饼特性之间的关系。使用小角度光散射和共聚焦扫描激光显微镜等工具确定聚集体结构。通过无量纲方法测量在不同絮凝条件下产生的聚集体的比较粘结强度。观察到这些性质对特定滤饼抗性,饱和度和水分含量的影响,作为过滤性能的指标。发现使用适量的絮凝剂剂量(60-100克聚合物/吨煤)生成的这种超细煤(97%<35微米)的絮凝物可优化脱水滤饼的性能。尽管发现由更大,更强的聚集体和更多絮凝剂组成的滤饼具有较高的孔隙率,但对特定滤饼阻力和滤饼饱和度的影响是有害的,这可能是由于难以脱水的集聚体内部孔隙比例增加所致。这种趋势在低过滤压力下不太明显,其中大部分脱水发生在集聚区之间较大的毛细管中。另外,聚合物分子的存在负责吸收无法通过机械手段除去的残留水分。通过使用预先形成的滤饼的一系列测试,每添加100克滤饼,每添加1克聚合物/吨煤,絮凝剂保留的水分量就可量化为大约10.2毫克水。在这种情况下来自高压过滤。

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