Tech Solutions

Sequential Liquid-Lignin Recovery and Purification: SLRP

        Lignin Enterprises has developed the SLRP technology which outperforms other lignin-recovery processes that debottleneck Recovery Boilers allowing an increased output of pulp in mill plants.

        The Recovery Boiler is one of largest and most expensive operations on the campus of any kraft pulp mill. Generally, the CAPEX required to rebuild a mill's Recovery Boiler is high, approaching or exceeding $100 million. Additionally significant downtime for the retrofit requires black liquor to be shipped to another mill for processing into white liquor to keep the mill running. Typically Recovery Boilers become limited due to excessively high heat flux through its steam-generating tubes. Removing lignin from black liquor offers the opportunity to de-constrict the Recovery Boiler with no downtime and relatively low CAPEX. Once other infrastructure is also increased, removing 40,000 Te/y lignin can facilitate an additional 60,000 Te/y of pulp production.

        Currently, there are three processes commercially available to remove lignin:

        All three operate on similar principles. Lignin is precipitated from black liquor by reducing the pH≈10 using carbon dioxide. Then sulfuric acid is used to reduce the the pH≈2 so the inorganic acid can be reduced by washing with water. LignoForce uses oxygen to pretreat the black liquor to minimize sulfur gases and to make the filtration easier.

        SLRP is significantly different from either of the other two processes in that: Oxidation improves the "odor profile" of the product lignin. SLRP is significantly different from either of the other two processes in that:

Pilot-Scale SLRP

    SLRP Advantages

  • One-half lower CAPEX

  • One-third lower OPEX

  • Superior sulfur-gas capture

  • One-third lower CO2 consumption

  • Smaller footprint

  • Can use acetic rather than sulfuric acid


Devon Stevens |