The Lignoboost Process

A process for lignin removal from alkaline pulping liquors (black liquors) has been developed within the FRAM2 R&D Program (Future Resource Adapted Pulp Mill, part 2). The lignin product (Fig. 1) from a demonstration plant, owned and operated by Innventia (formerly STFI-Packforsk), was characterized and used in different combustion trials with good results – co-firing of lignin and bark in a fluidized bed boiler, co-firing with coal in a PFBC (Pressurized Fluidized Bed Combustion) boiler and firing of lignin in a full-scale lime kiln. The process development and operation of the demonstration plant has displayed good results. Runnability in the demonstration plant and the lignin quality have been both very good. The work done on the investment and operational costs showed great potential for improving the concept of economy, which is very promising. INTRODUCTION One way of exploiting the energy surplus of a modern kraft pulp mill is to extract lignin from the black liquor. This gives the pulp mill a great opportunity to develop new economical revenues when the new by-product, lignin, is commercialised or used within the pulp mill to reduce production costs. Lignin extraction has the additional advantage of providing an incremental capacity in the chemical recovery area, so that it can be used to off-load the recovery boiler or to avoid expansion, when pulp production is increased. One way to handle the bulk flow of produced lignin could be to use the dry lignin powder as a biofuel in the lime kiln and swap fossil fuel. Other ways could be to use lignin in other burners/boilers, where fossil fuel is normally used, boilers in which corrosion from chlorides is a problem or, generally, in fluidized bed boilers frequently used for biomass combustion. Processing of kraft lignin, precipitated from black liquor, to produce a solid biofuel with high energy density and low ash content, is an idea originating from the R&D Program entitled KAM (the Ecocyclic Pulp Mill), developed within the R&D Program