Effectiveness of magnesium oxide additives in mitigating fouling problems in kraft recovery boilers

• Published in: TAPPI Journal
• Main Authors: Zhao, Liming, Tran, Honghi, McCabe, F. Donald
• Format: Article in Journal/Newspaper
• Language: English
• Published: TAPPI Press 2013
• Subjects: Canada; Peace River
• Online Access: http://hdl.handle.net/1807/98242; https://doi.org/10.32964/tj12.6.19

A systematic study was performed in the laboratory and in the field to examine the effect of magne - sium oxide additive on deposit accumulation and removal. Laboratory results show that the additive has little effect on the amount of deposits collected on a probe, but it can make deposits easy to remove if a coating layer thicker than 30 μm can be effectively applied on the probe surface. The results also show that mixing the additive with black liquor or injecting it separately has no significant effect on deposit accumulation and removal. Tests performed in a recovery boiler where the additive was continuously injected show no evidence for the existence of the coating layer. The magnesium oxide content in the boiler deposits varied between 0.1 and 0.4 wt%, which is several times lower than the amount that was found to be effective in laboratory tests. Nonetheless, the additive was shown to be effective in facilitating deposit removal if it can form a coating layer on deposit/tube surfaces. This may be possible by periodically injecting a large amount of additive into the boiler for a short period and reducing the black liquor fir - ing rate at the same time. This work was conducted as part of the research program In - creasing Energy and Chemical Recovery Efficiency in the Kraft Process, jointly supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and a con -sortium of the following companies: Andritz, Babcock & Wil - cox, Boise Paper, Carter Holt Harvey, Celulose Nipo-Brasileira, Clyde-Bergemann, DMI Peace River Pulp, Fibria, Internation - al Paper, Irving Pulp & Paper, Metso Power, MeadWestvaco, StoraEnso Research, and Tembec.