Lignin has many potential uses. Its use for fuel has been established, but as a biomass based source of aromatic functionality, its economic potential as a chemical feedstock significantly outstrips its fuel equivalent value. In addition to generating a value-added product from kraft pulp mills, removing lignin from kraft black liquor on a commercial scale could offload the recovery boiler with respect to calorific load thereby enabling increased pulp production. Integrating lignin extraction into an operating mill takes advantage of existing infrastructure, significantly reducing the complexity and cost versus a new standalone plant. A pilot scale lignin production plant has been installed in a Canadian kraft pulp mill. The unit is designed to produce 100 kg/d of lignin, which is precipitated from -30% black liquor, then separated from the liquor and purified. It incorporates a patent pending process^ developed by FPInnovations in which the liquor is oxidized prior to acidification, thereby improving slurry fiiterability and reducing acid requirements. The goals of the plant are to produce sufficient quantities of lignin for large scale trials and research into value-added applications, and to fine-tune lignin extraction conditions. The plant began operation in March 2011, and has been producing washed lignin for external users since August 2011. The plant can run mill liquor in real time, and can also process liquor from other facilities. The pilot plant can run in a variety of configurations and operating conditions, and is an excellent tool for process development and optimization. Lignin from the pilot plant is routinely characterized with respect to purity, morphology, thermal, and chemical properties. In most cases, the lignin contains low ash and a high amount of free phenolic hydroxyl groups. The latter characteristic is of importance when lignin is used as a replacement of phenol in the preparation of lignin-based phenol formaldehyde resins used as adhesives in wood products (for example, plywood and oriented strand board OSB). Wood product adhesivesis one application that FPInnovations has extensively evaluated with good success. The results show that when up to 50% of phenol is replaced by softwood kraft lignin, plywood shear strength values are comparable with those of the controls and very close to or higher than the Canadian specific standard value of 2500 KPa.
展开▼
