| Magnesium oxide-based additives have been used in kraft recovery boilers to minimize deposit accumulation on superheater and generating bank tubes. Due to inconclusive results observed in boilers and claims made for additive effectiveness backed by little scientific evidence, only a few mills still use the additives for fouling control. A systematic study was performed to examine the effect of MgO-based additives on deposit accumulation and removal under controlled laboratory conditions, and to evaluate the additive effect in a kraft recovery boiler. The results show that while the additive coating has no effect on deposition, it could ease deposit removal if a coating greater than 5 μm can be applied on the tube surface effectively. Separate injection of additive and black liquor had insignificant effect on deposition and removal. Results of the field study show that the amount of additive collected on the tube is too small to have an impact. |
