| 摘要 |
PURPOSE:To contrive to simplify a system and consequently reduce the manufacturing cost of the title boiler by a structure wherein an upper burner to supply blast-furnace gas is provided and, in addition, an additional air nozzle to supply the air for burning unburnt matter is also provided above the upper burner. CONSTITUTION:About 20% of CO and about 3-5% of H2 are contained normally in the composition of blast-furnace gas, which reduces NOx produced in the combustion zone of a main burner 7. The remaining unreacted CO and H2 are burnt by the air introduced in a furnace 9 from an additional air nozzle 8 above an upper burner 24. Further, the feeding rate of the blast-furnace gas introduced in the furnace 9 from a lower blast-furnace gas burner 25 is controlled in order to control the vapour temperature of a reheater (or a superheater). In other words, the steam temperature mainly in partial load is controlled by changing the amount of gas produced through the change of the ratio of fuels mixed of the blast-furnace gas.
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