Are North American Kraft Pulp Mills at Risk?, Paper360º November/December 2018

The first recovery boiler for kraft application was invented by Tomlinson in the early 1930s. While the average life expectancy of a boiler is 40 years with a rebuild frequency of every 15 years, 57 percent of the recovery boilers currently operating on a global basis are operating beyond the anticipated life (Fig.1).

A recovery boiler is an integral component in the successful operation of kraft (and, to a lesser degree, sulfite) pulp mills. As the name implies, the chemicals for white liquor are recovered and reformed from black liquor, which contains lignin from previously processed wood. The black liquor is burned, generating heat that is usually used in the process or in making electricity, much as in a conventional steam power plant.

North America does have some of the oldest recovery boilers (52 percent of North American recovery boilers were built in or before 1978) when compared with other papermaking regions, and it also has the highest total steam capacity and rate in its recovery boilers (rate = kg or lbs/day of black liquor solids). One of the reasons for this is the aging of recovery boilers (Fig. 2).

North America has gradually lost its stronghold versus other regions in kraft pulp production, declining by 6 million tons (9 percent) since 2007 (Fig. 3).

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