Causes:

1.The fuel oil atomization is poor or oil gun is out of order and the lubricating nipple cokes.

2.Total air volume is not sufficient.

3.The air distribution is not good, the air at root lacks or the oil mist is not mixed well, causing oxygen deficit locally and generating pyrolysis.

4.The secondary combustion happens inside gas duct.

5.The boiler temperature and air temperature at initial period of starting is too low.

Preventive measures:

1.Before igniting, check the oil gun and clear the coking of nipple to increase quality of pulverization.

2.Confirm that the oil gun has entered to the burner and its position is correct.

3.Keep the oil supply, oil return pressure and fuel oil viscosity index in operation normal.

4.Feed proper amount of air at the root timely to make oil mist intensively mix with air and to prevent oxygen deficit locally.

5.To increase air temperature and hearth temperature as far as possible.