Implications of Converting a Kraft Pulp Mill to a Dissolving Pulp Operation with a Hemicellulose Extraction Stage, 2012 TAPPI PEERS Conference

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The global market demand for dissolving pulp has been increasing at a remarkable pace over the last few years. The P&P industry took this opportunity to enter this market by converting pulp mills to dissolving pulp producers. Additionally, new value-added products could be produced if hemicelluloses are extracted. However, the conversion of a Kraft process into a dissolving pulp operation and the extraction of hemicellulose involve technical challenges and capital expenditure. Hemicellulose hydrolysis and its subsequent extraction affect energy and chemical balances. In this work, the conversion of a Kraft process into a dissolving pulp operation and the extraction of hemicellulose are studied. The energetic impacts of hemicellulose extraction, equipment requirements and new operating conditions have been analyzed by computer simulations and thermal pinch analysis. The digester is the first bottleneck to increase pulp production. A steam hydrolysis process in combination with energy optimization has the potential to increase power generation. However, this potential is limited by the upgrading level required in the recovery boiler and lime kiln. Water hydrolysis is required to extract hemicelluloses. This extraction reduces the load in the recovery boiler and lime kiln. In this case, energy optimization can decrease the need for external fuels.