The high carbon content in fly ash is mainly due to the following reasons: The fundamental reason is that the fuel is not completely burned.

(1) Due to various factors, the center of the furnace flame is on the upper side, and the incomplete combustion of pulverized coal in the furnace causes the carbon content of the fly ash to increase.
(2) Uneven mixing of air and powder or unreasonable combustion adjustment, resulting in insufficient fuel combustion and increased carbon content in fly ash.
(3) The operation of the pulverizing system, judging from the multiple sampling of pulverized coal, the pass rate of pulverized coal is not ideal. The main reason is that there is a big gap between the performance of the coal mill itself and the design performance. In addition, the coarse powder separation baffle, the air volume of the coal mill and the grindability of the coal will directly affect the fineness of the coal powder and increase the carbon content of the fly ash.
(4) The air leakage rate of the air preheater is too large, and the oxygen content of the furnace is insufficient. The air leakage rate of the air preheater is as high as 30%~40%, which is much higher than the design value of 20%. Due to the air leakage and oxygen-deficient combustion of the boiler, the carbon content of the fly ash is seriously high.
(5) The soot blower cannot be put into operation normally, the secondary air volume and air distribution are unreasonable, and the peripheral conditions of boiler combustion such as secondary air temperature affect the combustion quality of the boiler, which in turn affects the carbon content of fly ash.
(6) Poor coal quality: due to frequent changes in blended coal combustion, such as pulverized coal with high ash content and low volatile content, raw coal with high moisture content, or anthracite coal with high carbon content, because it does not meet the design coal type, It will cause insufficient fuel combustion and increase the carbon content of fly ash.
(7) When running at low load, or when the combustion is unstable and the fuel is used for combustion, the combustion in the furnace is unstable and the air volume is too large or too small, resulting in insufficient fuel combustion and increased carbon content in the fly ash.
(8) Due to the poor characteristics of the combustion equipment, it is not conducive to the complete combustion of pulverized coal, and the carbon content of the fly ash increases.
(9) If the primary wind speed is too high or too low, it will affect the carbon content of the fly ash. If it is too high, it will delay the ignition and cause unstable combustion. If it is too low, the rigidity of the pulverized coal airflow will be weakened, the airflow stability will become worse, and the flame will be easily interrupted. This will increase the carbon content of the fly ash.

The analysis of the carbon content of fly ash is not only from the conventional direction. For coal, the quality of coal is poor, which not only causes the reduction of calorific value and unstable combustion, but also causes more influences. The poor soot blowing of the preheater actually affects the stability of the combustion. Although too much ash in the coal is the root cause, as the quality of the coal is getting worse and worse, it has caused more and more difficulties and new problems in the completion of the operation improvement indicators. There will be more and more, and we have a long way to go.