但是，灰分含量高和收集加工上的困难制约了对它们的充分利用。

However, the high ash content and logistical problems with collection and processing will limit full utilization of this resource.

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试验结果表明，对于高灰分煤尘，在冲击波的多次冲击下煤尘的爆炸特性明显增强，危险性大大增加。

These experiments have proved that, for the coal dust with high ash component, after multiple actions by shock wave, it's explosive characteristic has been greatly increased.

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煤的变质程度低，灰分高。

The coal has lower metamorphic grade with high ash.

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