1. Coking and blockage of the burner nozzle in the low-nitrogen steam generator, or partial blockage of the burner inlet by debris such as small oil guns;

2. Excessive impurities in pulverized coal, excessively high speed of the coal feeder, heavy pulverized coal, and excessively low primary air velocity;

3. Excessively high speed of the coal feeder, excessive coal feeding without timely purging;

4. Excessively low primary air pressure (air damper not opened or opened too little), failing to carry away the pulverized coal.

Preventive measures for primary air pipe blockage in low-nitrogen steam generators:

1. Adjust the corresponding primary air pressure in time based on the speed of the coal feeder and the unit load of the low-nitrogen steam generator. The speed of the coal feeder must not exceed 700rpm. Maintain the primary air velocity at 25-30m/s, control the primary air and coal mixture temperature between 180-250°C, and adjust the primary air pressure according to the load and coal quality, with a variation range of 2.5-3.8kPa;

2. If the primary air velocity is found to be too low or the primary air temperature is below the normal value, promptly reduce the speed of the corresponding coal feeder to restore normal primary air velocity and temperature;

3. Fully purge the pipes when starting or stopping the coal feeder to remove accumulated pulverized coal in the coal pipes;

4. If the burner nozzle is coked or blocked by debris, take measures to clear it.