What issues should be considered during the startup of a circulating fluidized bed boiler?

Precautions during startup: 1. Before ignition, the thickness of the bed material should be maintained between 600 and 800 mm. The particle size and distribution of the bed material as well as the coal fed should be appropriate; it is advisable to keep the bed pressure in the furnace at 4.5 to 6.0 kPa when feeding coal. 2 If the feedwater temperature is low, try not to put the economizer recirculation pipe into operation. 3 To prevent the bed temperature from rising too rapidly during oil injection, the output of the oil injector can be adjusted, or the atomizing elements of the oil injectors located beneath the bed can be replaced at different stages to increase their output gradually. 4 During the fuel process when coal feeding conditions are about to be met, close monitoring of the ignition air duct should be carried out, and the flow rate of the fluidization air should not be reduced indiscriminately. 5 It is necessary to establish a concept of the trend in bed temperature changes; this is particularly important at the times when there are two increases in bed temperature. The flow rate of air used for fluidization should not be reduced too rapidly, and when the rate of change in bed temperature shows a downward trend, care should be taken to add an appropriate amount of coal. 6　In the event of a furnace deflagration, all fans should be stopped promptly depending on the situation, in order to identify the optimal timing for preventing coking. After deflagration, a comprehensive assessment should be made based on various parameters; slag removal should be intensified. If coking is detected, replacing the bed material and removing slag will not improve the fluidization conditions inside the furnace, and in such cases the furnace must be shut down urgently for coking removal. There should be no attempt to take chances, as this could lead to further expansion of the accident. 7　In the later stage of ignition, it is necessary to strengthen the monitoring of two parameters: the outlet temperature at the upper part of the furnace and the oxygen content at the furnace outlet, in order to assist in assessing the quality of combustion and fluidization conditions within the furnace.