Reducing agglomeration phenomena in a SRF-fired fluidized bed waste-to-energy plant through the use of dolomite: a full scale investigation

Agglomeration is often the result of the in-bed formation of low melting point eutectic mixtures through the reaction of mostly alkali compounds of the waste feed with the silica bed materials. The agglomeration produces an increase in the particle size of the burner bed, generating the de-fluidization of the bed and consequently plant shutdown. Possible countermeasures generally include the use of alternative materials to sand as bed material and the addition of additives to increase the melting temperature of ash during waste combustion. Considering the field of additives addition, the aim of the study was to test the suitability of dolomite (CaCO3·MgCO3) to reduce the plant shutdown due to agglomeration. For this scope, a full-scale experimental investigation was carried out at the ETA WtE plant in Manfredonia (Southern Italy), which burns solid recovered fuel (SRF). The obtained results showed how, with the same amount of SRF burned, the working period of the turbine for electricity production increased on average by 10%. Slag characterization before and after the addition of dolomite showed how the density decreased from 2.75 to 2.41 g/cm3 while the concentration of carbonates (as CaCO3) increased from 3.94% to 57.7%. At the end of the treatment, the slag sample was visually softer, showing a tendency to crumble easily.