Enhancing dissolving pulp production and co-product value

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Dissolving pulp is used for manufacturing cellulose derivatives that are used in products such as clothing, cigarette filters, pharmaceuticals, etc. Dissolving pulp is composed of >95% cellulose, thus the hemicellulose and lignin must be removed during the pulping process.Although cellulose purification is an intensive process, the conversion of a Kraft pulp mill to produce dissolving pulp is transformative, as the mill adapts a true biorefinery approach with the potential to generate value from the cellulose, hemicellulose, lignin and extractive biomass components. The critical process modification when converting a conventional Kraft mill to produce dissolving pulp is the prehydrolysis of the wood chips which helps to facilitate the removal of hemicellulose, while subsequent kraft pulping is mostly aimed at removing the lignin. Fortress Specialty Cellulose (FSC) is at the forefront of Canadian efforts to produce dissolving pulp using a pre-hydrolysis Kraft (PHK) pulp feedstock. However, the PHK process presents bottlenecks as it requires extended cooking times and additional digester capacity upstream of kraft pulping. Therefore, methods that can boost hemicellulose removal can increase the overall production rate of a dissolving pulp mill. During prehydrolysis, wood issubjected to treatment under acidic conditions at high temperatures to dissolve the hemicellulose, thus the subsequent transitioning of the acidic prehydrolyzed pulp to the highly alkaline kraft process also presents challenges. As well as these challenges, the PHK process annually produces approximately 40,000 metric tonnes of hemicellulosic sugars. Therefore, valorization of this hemicellulose stream is crucial to the functioning of the mill and creating additional revenues to realize a biorefinery approach. The specific objectives of the proposal can be summarized as follows: 1. To treat wood chips with enzymes to enhance the subsequent removal of hemicellulose during the prehydrolysis process; 2. To integrate green liquor pretreatment during PHK production to reduce pH control issues and enhance cellulose yields and 3.To valorize the hemicellulose produced during pre-hydrolysis through fermentation to "bio-jet" and "drop-in" fuel.