Increase Production in Your Recovery Boiler with LignoBoost • Extract Valuable Lignin for Biorefinery Production and Replacement of Fossil Fuels, 2009 TAPPI Engineering, Pulping, Environmental Conference

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The heart of the recovery cycle in a pulp mill is the recovery boiler. In the recovery boiler the organic material in the black liquor, of which lignin makes up the largest part, is combusted to produce heat and electricity. The inorganic part of the black liquor ends up in a smelt that is bled from the bottom of the boiler and utilized in the white liquor preparation plant to produce new cooking chemicals. Today, many mills have a surplus of energy and it is also rather common that the recovery boiler limits the production of pulp. By removing a part of the energy rich lignin, the overall heating value of the black liquor will decrease. Since the recovery boiler is limited by the heat load, the throughput of black liquor can be increased and, consequently, the production of pulp too. A lignin extraction unit does not only increase pulp production it also makes it possible to transform the energy surplus into a solid product. In a simplified example it has been shown that the production of pulp can be increased by about 22% upon removal of 0.18 ton of lignin/ADt pulp. Extracted lignin can either be used as a biofuel internally in the mill, e.g. as a replacement for fuel oil in the lime kiln, or sold to an external company to increase revenue. Lignin is, however, not only suitable for fuel applications, it can also be used as a raw material for the production of various products and chemicals, e.g. carbon fibers and phenols.