Danish Experiences with Deposit Probe Measurements in Grate and Pulverized Fuel Biomass Power Boilers

Several measuring campaigns with focus on deposition behavior have been conducted at full-scale power plants firing biomass in Denmark. These campaigns have been reviewed in this work. The focus is the obtained experiences on deposit formation, shedding and chemistry.
When comparing results from grate- and suspension-firing, it is found that the rates of deposit formation are comparable, while the chemical composition of the fly ashes are quite different, even for the same type of fuel. The flue gas temperature is considered to be an important parameter in the deposit behavior. Increasing the flue gas temperature leads to increased deposition rates and deposits with higher contents of Si and Ca and lower contents of K and Cl.
The shedding behavior is influenced by both probe surface temperature, flue gas temperature and deposits chemistry. The influence of temperature on the degree of sintering varies with the fuel type. Possibly, increased contents of Si and Ca leads to increases in the sintering temperature and thus altered shedding behavior.