報告書番号

W03016

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１） -－ CI-α･WRバーナによる瀝青炭燃焼時の操作条件の影響解明 －-

タイトル（英文）

Development of reduction and homogenization technology of unburned carbon on pulverized coal combustion (Part 1)- Influence of burner operating condition of CI-α･WR burner on bituminous coal combustion characteristics -

概要 （図表や脚注は「報告書全文」に掲載しております）

瀝青炭の微粉炭燃焼時に灰中未燃分濃度を1.5～2.5％に低減・均質化する燃焼技術について、灰中未燃分に影響の大きな燃料比が異なる３炭種を用いて、当所の石炭燃焼試験炉において検討を行った。CI-α･WRバーナと空気多段注入法の組み合わせでは、燃料比の低い石炭では、目標とする灰中未燃分濃度を達成できたが、燃料比の高い２炭種においては、それより灰中未燃分濃度が高くなった。燃料比の高い瀝青炭燃焼時においては、微粉炭搬送用空気流速を減少させ、３次空気の旋回角度を強くすると、高温の燃焼火炎における微粉炭の滞留時間が長くなると共に火炎を適度に拡げることが可能になり、バーナ近傍の広い範囲において酸素の消費が促進できることがわかった。その際，灰中未燃分濃度を1.5～2.5％に調整できることに加えて、還元領域も広がるため、火炉出口のNOx濃度を100ppm以下に低減できることが明らかとなった。

概要 （英文）

Coal is an important energy for meeting the increasing electricity demand because it has more abundant reserves than other fossil fuels. At present, the main method of coal utilization in Japan is pulverized coal combustion. It is important to reduce both emissions of NOx and unburned carbon on pulverized coal combustion. We have already developed the advanced low NOx burner (CI-a burner). This burner with multi staged air injection method can reduce unburned carbon concentration in fly ash less than 3 % at 100 ppm of NOx concentration at the exit of furnace. Additionally, we have also developed the wide road range burner (CI-a･WR burner), which can fire at a lower load such as an oil burner. In these days, ash utilization is problem and cost of it has to reduce. In order to utilize ash for valuable matter such as a cement mixture and so on, unburned carbon concentration in fly ash has to reduce and be homogeneous. This report describes the pulverized coal combustion technologies in order to reduce unburned carbon concentration in fly ash from 1.5 to 2.5 % at 100 ppm of NOx concentration at the exit of furnace. Combustion tests were performed by firing three kinds of fuel ratio’s coal (0.8, 1.5 and 2.0), which were used in Japanese power stations, on pulverized coal combustion test furnace with CI-a･WR burner. The main results are as follows.1) When low fuel ratio coal (0.8) was fired, unburned carbon concentration in fly ash could be reduced less than 2.5 % at 100 ppm of NOx concentration at the exit of furnace. When fuel ratio was higher (1.5 and 2.0), unburned carbon concentration in fly ash was more than 2.5 %. Then, combustion flame became narrow in the furnace.2) When A/C (Weight ratio of primary air to pulverized coal) decreased, pulverized coal stayed a long time in combustion flame with high temperature. We cleared that unburned carbon concentration in fly ash could be reduced without large increase of NOx concentration at the exit of furnace by decrease of A/C.3) Combustion flame could be diffused by increase of swirl vane angle. Oxygen consumption was accelerated outer side in the furnace, and unburned carbon concentration in fly ash decreased. NOx reduction area at the optimized burner operating condition became wider than that at the standard combustion condition. NOx was decomposed outer side in the furnace, and NOx concentration decreased at the exit of furnace.As a result, when burner operating condition was optimized for fuel ratio of bituminous coal, it was possible that unburned carbon concentration in fly ash reduced and homogenized from 1.5 to 2.5 % and NOx concentration at the exit of furnace decreased less than 100 ppm.

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