Effects of different factors on sulfur trioxide formations in a coal-fired circulating fluidized bed boiler

- Heterogeneous and homogeneous formations of SO3 in a coal-fired CFB boiler were measured.
- An improved SO2/O2/H2O/CO2/CO/NO mechanism was built based on previous mechanisms.
- Homogeneous formation of SO3 in a coal-fired CFB boiler was numerically calculated.
- Effect of the influencing factors on formations of SO3 was investigated.

Experimental and numerical studies were conducted to determine the effects of different factors on homogeneous and heterogeneous formations of sulfur trioxide (SO3) in a coal-fired circulating fluidized bed (CFB) boiler. In the experiments, homogeneous and heterogeneous formations of SO3 under coal-fired CFB combustion conditions were measured using controlled condensation and S balance, respectively. Meanwhile, homogeneous SO3 formation under coal-fired CFB combustion conditions was numerically calculated using an improved SO2/O2/H2O/CO2/CO/NO kinetic mechanism. Measurement results showed that the effect of fly ash on SO3 concentration was slightly stronger than that of circulating ash. Both experimental and numerical results showed that SO3 concentration was apparently affected by SO2, O2, and H2O concentrations and temperature but barely affected by CO2 concentration.