Air preheater control device for a coal-fired boiler

摘要

A method of controlling an air heater of a coal-fired boiler system comprising an air heater for heating a primary air used to dry a pulverized coal and convey it into the boiler and a secondary air to combust the pulverized coal by a heat exchange utilizing the exhaust gas discharged from the boiler as a heat source. The air heater includes a primary air heater and a secondary air heater arranged in parallel and the exhaust gas is introduced therein from the boiler by an induced draft fan with the flow rate of the exhaust gas being introduced into each of the air heaters being controlled by a respective gas damper. The heater primary air is mixed with a cold air to have a suitable temperature to dry and convey the pulverized coal, wherein the opening of the damper for the cold air is maintained at a low value of approximate 0% for maintaining the flow rate of the cold air low, while the suitable temperature is obtained by controlling the gas damper for the primary air heater.