Waste to Energy by Supercritical Water Gasification - Utilization of Residual By-Product Streams from the Pulp and Paper Industry

This study looks at supercritical water gasification as an alternative method to the current effluent treatment methods in the pulp and paper industry. The method provides means for recovering both energy and material, without the need for drying prior to treatment. The main question in this study is if the waste streams are suitable for treatment by SCWG. The type of residual by-product streams that arise, the energy content of the streams and the current treatment methods are mapped. The composition of the residual by-products has a wide variation, due to the production of many different products at the facilities. The suitability of treatment of three sample streams by SCWG is studied experimentally in a laboratory-scale reactor system. Gasification of black liquor from the sulphate pulping process, primary sludge from a pulp and paper effluent treatment plant and de-inking sludge at 700°C and 25 MPa resulted in gasification efficiencies of 33-53% on carbon basis, depending on the feed.