Therefore, the discovery and study of the coal balls is of great significance in theory and practice.

因此，这种煤核的发现和研究具有一定的理论和实际意义。

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The isolated and anatomically_preserved lepidodendralean leaf cushions were described from coal balls in Wangjiazhai Formation (upper Upper Permian) in western Guizhou Province.

描述了贵州水城矿区汪家寨组（晚二叠世晚期）煤核中一种脱落的具解剖构造的鳞木类叶座。

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The effects of binder and damp mill on green balls, the process for preheated pellets with high strength and easy reduction, and coal-based direct reduction iron(DRI) were studied.

以新疆磁铁精矿为原料，采用“一步法”直接还原，研究粘结剂种类和润磨方式对生球质量的影响，高强度、高还原性预热球团的制备及煤基直接还原的工艺。

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