Kraft pulping Kraft pulping Energy consumption and production Pulp and paper production is among the most energy intensive segments of all industries. However, it is useful to distinguish between pulp and paper manufacture. Pulp and paper mills are not always integrated, and while pulp mills produce more energy than they need, paper mills require large quanitites of steam to run their dryiers. Kraft and soda pulp mills are energy self-sufficient, and often generate excess steam and electricity which can be used by an associated paper mill or sold to neighboring industries or communities.
Black liquor is an integral part of the standard pulping process.
Without chemicals recovery, the process would be uneconomical. The chemical recovery process is an exothermic chemical reaction which produces enough heat to gasify lignin and other volatile constituants of the black liqor. The reacted chemical salts are removed from the smelt bed into a smelt tank where they form the green liquor system in a pupl mill. Additional energy is often recovered from the combustion of bark and other wood residuals. This value is generally higher in some of the North European countries where higher energy prices drive them to spend more capital in order to obtain increased efficientcies.