Bed temperature is detected by the thermocouple arranged at the dense-phase area. During the operation of the circulating fluidized bed boiler, in order to reduce incomplete combustion heat loss, improve the heat transfer coefficient, and to reduce CO and NO emissions, bed temperature shall be as high as possible, but in consideration of desulfurization to reduce Nox emissions and preventing coking in bed,  the bed temperature shall be lower. Under normal conditions, the bed temperature generally is controlled in the range of 850-950 ℃. To maintain normal bed temperature is the key to stable operation. The best means to control bed temperature is  to re-allocate different combustion air volume in the combustion chamber and to keep total air volume constant. Under a certain load,  if the coal feeding is certain, then the primary air and the secondary air amount shall be adjusted. On the basis of  ensuring fully fluidization of bed materials, the primary air volume can be appropriately reduced, in order to reduce the quantity of the heat taken away by the fume, to maintain higher bed temperature and increase the combustion efficiency. With the secondary air , the oxygen amount can be kept within the normal range ,so that the balance of bed temperature is between 850-950 ℃.    (lsh)