Conventional coking treatment methods:

Early biomass power plants generally used steam soot blowers to carry out coking and ash removal treatment on the heating surfaces. However, in terms of actual effects, the requirements for coking removal were not met. The treatment can only be carried out by flushing with high-pressure water after the furnace is shut down. The main reason is that the potassium content in biomass fuel is relatively high, which lowers the ash melting point. Meanwhile, silicon forms low-melting-point compounds with potassium during combustion, resulting in a lower softening temperature of the ash. According to experimental data, the deformation temperature of wood ash is around 800℃, while the temperature of the furnace superheater in boilers is mostly within this range. Therefore, under high-temperature conditions, Softened ash deposits are prone to adhere to the outer walls of the heated surface pipes, and it is difficult to deal with the accumulated coke blocks using a steam soot blower. Based on past experience, for general boilers using steam soot blowers, after being cleaned and put into use for 15 days, the control of the main steam temperature does not need to be adjusted with desuperheating water. The temperature is normally maintained at around 510 ° C. After one month of operation, the boiler needs to be shut down for water flushing; otherwise, the main steam temperature will increasingly deviate from the rated value (540 ° C), and the efficiency of the boiler will decline. The exhaust gas temperature will rise by about 5 to 10 degrees Celsius.

There are the following problems when using steam to blow ash:

(1) The medium purge area is limited, with some dead corners existing, which is prone to form flue gas corridors and aggravate local wear.

(2) The long ash blowing cycle causes excessive ash accumulation on the heating surface, and even leads to the sintering and hardening of the accumulated ash, increasing the difficulty of ash blowing.

(3) If the pressure of steam soot blowing is too high or it is used for a long time, it will accelerate the wear of the metal pipe wall. If the pressure is too low, it will affect the soot blowing effect.

(4) It increases the humidity of the flue gas inside the furnace, causing low-temperature condensation at the air preheater and resulting in severe corrosion of the air preheater tubes.

(5) The failure rate of mechanical parts is high and the maintenance cost is also high.

In summary, strengthen the separation of impurity components in biomass pellets to ensure that the content of soil impurities is lower than the average value. Improve the air supply mode and air volume for the combustion of biomass pellets; Modify the combustion mode of the boiler or the distance between the feed and the ash discharge.