The causes of Loss of ignition accidents is mainly because that incomplete comburent accumulates in large amount due to long term poor or incomplete combustion and drops, thus the negative pressure of boiler hearth fluctuate violently, and the flame can not be monitored by flame detection, so the protective device acts and the flame is extinguished. The main causes are as follows:
1. Poor proportioning of air and coal fine
Too much air or too less air volume both will cause incomplete combustion, if there is too much air, the coal fine will not burn out and will be taken away from the combustion room, thus causing coking; if there is too less air, the oxygen is not sufficient and the loss from incompletely burning out of coal will increase, and the unburnt materials accumulate in the hearth of the combustion chamber or under it.
2. Outlet air speed and air rate of primary air and second air of burner
The air speed of primary air and secondary air will directly affect the height of the flame  kernel and will make combustion in advance or postpone the combustion or cause incomplete combustion .
 3. Fineness of pulverized coal
If the pulverized coal is too coarse, the combustion will be incomplete; if the pulverized coal is too fine, it will be burnt too early and will coke at the outlet of the burner.
4. Load distribution and turning on/off mode among the burners
The load distribution shall be evenly as possible in order to promote the complete combustion.
5. Combined mode of coal mills
The operating condition of Mill A and Mill C and the operating condition of Mill B and Mill C shall be avoided.
6. The proportioning of secondary air and surrounding air shall be reasonable.
7.  The dip angle of burner shall be proper, if it is downward much, thus easily causing insufficiently air incoming and coking at the cold ash hopper and upper part of the side wall. If the dip angle is too small, thus easily causing the flame upwarping and incomplete combustion.