| 摘要 |
PURPOSE: To increase the flow rate of combustion exhaust gas which flows into a, combustion exhaust duct from a boiler main body by mixing a part of combustion exhaust gas on the outlet side of an air preheater with a secondary air heated by the air preheater. CONSTITUTION: When high humidity coal 18 is supplied to a mill 12, a part of combustion exhaust gas (a) on the outlet side of an air preheater 7 is mixed with a secondary air (c) on the outlet of the air preheater 7, thereby increasing the flow rate of the secondary air (c). The temperature of a primary air (b) to be supplied to the mill 12 from the air preheater 7 is raised by increasing the flow rate of the combustion exhaust gas (a) which is introduced to the air preheater 7 from a boiler main body 3. Even when high humidity coal 18 is supplied to the mill 12 for the coal 18, the air preheater 7 is capable of raising the temperature of the primary air dramatically. It is, therefore, possible to prevent the temperature of the primary air on the outlet side of the mill 12 from dropping to a specified temperature or below. This construction makes it possible to prevent the combustion efficiency of the boiler main body from being lowered and hold the operation efficiency of the boiler at a high level. |
