The reasons for the incomplete combustion of biomass:

1. Furnace temperature. The incomplete combustion of biomass in the boiler is related to the temperature in the furnace. If the furnace temperature is lower than 600 degrees Celsius, it can not provide a good combustion environment for the biomass, and incomplete combustion will occur. 

2. Air supply. Air is inseparable for the combustion of any substance. If the air supply is insufficient or the air is not well mixed with biomass pellets under sufficient conditions, the air supply can not meet the needs of complete combustion of combustible components in the fuel, which results in the incomplete combustion of biomass.

3. Fuel moisture. If the biomass fuel moisture is too high like more than 45%, incomplete combustion will occur.

4. Biomass pellets. The biomass fuel has common shapes such as particles and lumps. If the biomass pellets are too large, incomplete combustion will occur.

5. Ash content. If the biomass is of low quality, it means the ash content is large, which will cause the ash content to be packaged into the burning part, resulting in slower fuel combustion.

6. Feeding. If the hand-fired or chain-linked biomass boilers that exceed the specified fuel amount, the fabric layer on the grate will be too thick and the gas and solid cannot be mixed benignly, so incomplete combustion is easy to occur. Too little feeding will cause insufficient heat storage capacity of the grate’s feed layer and incomplete combustion of fuel.