報告書番号

M12008

タイトル（和文）

未利用炭利用技術の開発 －豪州産難粉砕性石炭(低HGI炭)の粉砕・燃焼基礎特性の評価－

タイトル（英文）

Development of utilization technology for unused coal - Basic evaluation of grindability and combustibility of hard grindability (low HGI) coal mined in Australia -

概要 （図表や脚注は「報告書全文」に掲載しております）

瀝青炭ではあるが、HGIが４０以下と低い低HGI炭の粉砕・燃焼特性について、当所のローラミルと微粉炭燃焼試験炉を用いて評価した。低HGI炭を通常利用されている瀝青炭の微粉炭粒径まで粉砕すると、粉砕動力が非常に大きくなった。この原因は、ミル差圧が高くなっていることから、低HGI炭がミル内に大量に滞留し、繰り返し粉砕されているためと考えられる。低HGI炭を既設火力と同等の条件で粉砕すると、他の石炭で評価したHGIと粉砕仕事指数の相関関係から大幅に外れ、動力が推算できないことがわかった。一方、燃焼特性については、低HGI炭の燃料比が１以下と低いため、粒径が同等の瀝青炭と比べて、燃焼効率が高く、且つ、窒素分含有率が低いため、NOｘ排出量も低い値を示した。さらに、低HGI炭は、微粉炭の粒径を粗くしても、燃焼効率が大きく低下せず、NOx排出量が若干増加する程度であることが明らかとなった。

概要 （英文）

In these days, large amount of steam coal is required rapidly in the Asia area. Pulverized coal fired power stations in Japan mainly utilize high grade bituminous coals to steam coal. From the view point of amount of imported demand and exported supply of steam coal in the Asia area, it is important to diversify coal type. In Australia, large amount of unused bituminous coals are reserved. One of them is bituminous coal with low volatile. The other is bituminous coal with low HGI (Hardgrove grindability index). In this study, at first, the grinding characteristic of low HGI coal is investigated using a roller mill at CRIEPI (coal grinding rate: 0.3 ton/h). Secondary, combustion characteristics of it is investigated using a pulverized coal combustion test furnace at CRIEPI (coal combustion rate: 0.1 ton/h). Main results are follows.
1. When low HGI coal is ground by the roller mill, pulverized coal diameter of it is coarse and is almost same as that of sub-bituminous coal with nearly HGI. On the other hand, the grinding power of low HGI coal is much higher than that of sub-bituminous coal. Then, pressure drop between at the inlet and at the outlet of the roller mill becomes much high. It means that residence time of pulverized low HGI coal becomes long in the roller mill. Therefore, the reason of requiring high grinding power is considered that low HGI coal is ground many times in it. Here, the grinding power decreases and pulverized coal diameter becomes coarse when the rotation speed of separator decreases. Then, the grinding power of low HGI coal becomes much low as same as that of sub-bituminous coal.
2. Because of the volatile matter content in low HGI coal is higher than that in other bituminous and sub-bituminous coals, combustion efficiency becomes high. And also, NOx emission at the exit of furnace is also low since nitrogen content in low HGI coal is lower than that in other coals. In the case of firing of bituminous coal with low volatile matter, when pulverized coal diameter increases, NOx emission increases and combustion efficiency becomes low. On the other hand, when pulverized coal diameter of low HGI coal increases, both combustion efficiency and NOx emission are almost equal as volatile content of low HGI coal is low.

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