報告書番号

M05013

タイトル（和文）

微粉炭燃焼時の灰中未燃分低減・均質化技術の開発(その２) -- 亜瀝青炭混炭燃焼時の検討 --

タイトル（英文）

Development of reduction technology of unburned carbon on pulverized coal combustion (Part 2)- Blended combustion of sub-bituminous coal with bituminous coal -

概要 （図表や脚注は「報告書全文」に掲載しております）

燃料比約1.5の瀝青炭に水分含有率約20％の亜瀝青炭を30％と低い割合で混炭し、燃焼させた場合に高くなる灰中未燃分濃度を低減する燃焼方法について検討し、以下の結論を得た。亜瀝青炭低混炭燃焼時は、Air/Coalを、亜瀝青炭中の水分蒸発量まで考慮した流量まで低減し、バーナから供給する燃焼用空気の旋回強度を弱めることで一層の燃焼促進が図れることがわかった。また、亜瀝青炭低混炭燃焼時は瀝青炭燃焼時よりも火炉内の温度が低下するため、灰中未燃分濃度が低くなるよう多段燃焼用空気の1段目の空気流量を瀝青炭燃焼時に適した流量条件よりも多く注入して燃焼促進を図り、2段目の注入位置を火炉後流側に移動することでNOxをより分解できた。さらに、1次空気管の断面積を拡大し、微粉炭の濃縮を図ることで、火炉出口のNOx濃度を100ppm以下に低減し、且つ、灰中未燃分濃度を3%まで低減できることが明らかとなった。

概要 （英文）

It is important to reduce to less than 3 % of unburned carbon concentration in fly ash without increase of NOx concentration at the exit of furnace, because fly ash has to be utilized as useful material such as cement mixture without the treatment cost. In this investigation, reduction technology of unburned carbon concentration in fly ash without the increase of NOx concentration at the exit of furnace was developed during low blended combustion, which means 30 % of blended ratio of sub-bituminous coal with bituminous coal. Then, fuel ratio of bituminous coal is 1.5 and moisture content of sub-bituminous coal is 20 %. Main results are follows. 1. When the mass ratio of carrier gas for pulverized coal, including both primary air and vaporized moisture from sub-bituminous coal, to supplied coal is reduced to prevent the sedimentation of pulverized coal, oxygen consumption progressed efficiently around the burner outlet. Additionally, by adaptation of swirl vane angle of both secondary and tertiary air, both NOx concentration at the exit of furnace and unburned carbon concentration in fly ash are able to be reduced. 2. Temperature in the furnace during low blended combustion of sub-bituminous coal is lower than that on bituminous coal combustion. Therefore, when air ratio after the first injection point of multi staged air increases, unburned carbon concentration becomes low. Then, NOx concentration after the first injection point is high. When the second air injection point shifts toward the exit of furnace, NOx reduction area before the second air injection point becomes wide and NOx concentration at the exit of furnace decreases.3. The cross section area of primary air is modified to be wide in order to reduce primary air velocity without the decrease of primary air volume. And, pulverized coal is concentrated at the exit of burner to improve oxygen consumption. As a result, by optimizing both burner operation condition and multi staged air injection condition, it is cleared that NOx concentration at the exit of furnace can be reduced unburned carbon concentration in fly ash was reduced to 3 % at 100 ppm of NOx concentration at the exit of furnace.

報告者

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