報告書番号

W01034

タイトル（和文）

亜瀝青炭混炭燃焼時の灰中未燃分排出特性 -－亜瀝青炭低混焼条件における影響評価－-

タイトル（英文）

Characteristics of Unburned Carbon Concentration in Fly Ash on the Blended Combustion of Sub-bituminous Coal with Bituminous Coal - Evaluation of the Influence of Coal Property in the Low Blended Combustion -

概要 （図表や脚注は「報告書全文」に掲載しております）

瀝青炭と亜瀝青炭の混炭燃焼時における灰中未燃分の排出特性について、混炭率および石炭性状が及ぼす影響を当所の石炭燃焼試験炉を用いて検討した。亜瀝青炭の低混焼条件における灰中未燃分濃度は、亜瀝青炭の混炭率に応じて高くなる傾向を示し、その増加傾向は、水分含有率が高い亜瀝青炭の方が顕著になった。その際、未燃焼率は、混炭した亜瀝青炭に含まれる水分量と良い対応を示すことがわかった。さらに、混炭燃焼時の灰中未燃分の増加傾向は、瀝青炭の燃料比が低くなるのに応じて弱まり、特に、燃料比が亜瀝青炭とほぼ同等の太平洋炭では、混炭燃焼を行っても、灰中未燃分がほとんど増加しない事が明らかとなった。瀝青炭の燃料比と亜瀝青炭の水分含有量の増加により、灰中未燃分濃度は高くなるが、亜瀝青炭中の水分濃度に応じて低燃料比の石炭と組み合わせる事で、灰中未燃分濃度の急激な増加を抑制できることが明らかになった。

概要 （英文）

At present, coal-fired power stations in Japan fire mainly bituminous coal as fuel. Since consumption of bituminous coal is increasing worldwide and rate of bituminous coal will be advanced in the near future, the low rank coal will become an important fuel. Sub-bituminous coal, which contains more than 20% moisture, is expected to be a substitute fuel for bituminous coal. Sub-bituminous coal is the next most abundant reserve after bituminous coal and has a comparatively high calorific value. But there are some problems in use. Sub-bituminous coal does not easily ignite because of its high moisture content. Therefore, sub-bituminous coal will be fired on the low blended ratio with bituminous coal. This report describes the characteristics of unburned carbon concentration in fly ash on the low blended combustion of sub-bituminous coal, which means under 30% of blend ratio. This research was conducted using a pulverized coal combustion test furnace (coal combustion rate: 0.1 t/h). Main results are as follows.1.When sub-bituminous coal is blended with bituminous coal and fired, unburned carbon concentration in fly ash increases as the blend ratio of sub-bituminous coal because the combustibility of bituminous coal becomes worse due to moisture of sub-bituminous coal. The increase of unburned carbon concentration in fly ash as the blend ratio of sub-bituminous coal is more considerable when the sub-bituminous coal has higher moisture. Unburned fraction, which is calculated by ash content and unburned carbon concentration in fly ash, is shown a good correspondence with amount of moisture of blended sub-bituminous coal.2.Three kinds of bituminous coal, which are Newlands coal, Lemington coal and Taiheiyo coal, are used to compare the combustibility in blended combustion. Fuel ratio of Newlands coal, Lemington coal and Taiheiyo coal are 2.1, 1.6 and 0.8, respectively. When Newlands coal is used for blended combustion, increase of unburned carbon concentration in fly ash as the blend ratio of sub-bituminous coal is the highest. As the fuel ratio of bituminous coal decreases, increase of that becomes lower. Fuel ratio of Taiheiyo coal is the almost same as that of sub-bituminous coal. Particularly, the unburned carbon concentration in fly ash when Taiheiyo coal is used for blended combustion is almost equal in non-blended combustion.3.In the low blended combustion, unburned carbon concentration in fly ash becomes high when fuel ratio of bituminous coal increases or moisture of sub-bituminous coal is large amount. It was found that the considerable increase of unburned carbon could be suppressed by using bituminous coal with high volatile matter as increase of amount of moisture in sub-bituminous coal.

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