Fine particle alteration monitoring in flue gas at the convection pass inlet of a commercial circulating fluidized bed combustion boiler during solid recovered fuel combustion

A simple and effective method of fine particle sampling at the convection pass inlet in a boiler that burns solid recovered fuel is developed and demonstrated. The fine particles, which are assumed to be mineral salt in flue gas, easily combine with other fly ashes and then attach to the superheater tubes and form clinkers. This clinker deposits on the tubes cause deterioration of the boiler performance and lead to tube corrosion. Two commercially available chemical agents, ammonium sulfate ((NH4)2SO4) and borax solution, used for clinker control are tested to monitor their activity on clinker formation. When ammonium sulfate is applied, the PM2.5 particles of fly ash collected in the convection pass inlet increased. When borax solution is used, the PM10 particles are almost completely removed. The borax solution seems to absorb molten salt in the flue gas and make fine particles grow, whereas ammonium sulfate increases the 2.5 μm particles by changing the metal chlorides to metal sulfates. The borax solution shows potential to control fine particles, and especially PM10 particles. However, both additives increased sub-70 μm particles of convection pass bottom ash.