FORMATION OF LOW-MELTING DEPOSITS IN A MODERN KRAFT RECOVERY BOILER

In a kraft pulp mill, the build-up of chloride and potassium in the li quor cicuit can result in both the plugging of flue gas passages and i n the rapid corrosion of the superheaters inside the recovery boiler. A sampling prog-ram was conducted at a coastal kraft mill to study the influence of chlorides and potassium on the melting points of boiler deposits. One deposit with a melting point as low as 535 degrees C was recovered from the primary superheater, but the result could not be a ccounted for by consideration of the chloride and potassium content on ly. Some interesting correlations were found between boiler operation and deposit melting points.