Disposal of Solid Wastes from the Paper Industry using a CHTC-Based Technology: A Preliminary Study

The domestic paper industry is using tremendous amounts of recycled wastepaper as raw material for papermaking. Fair amounts of external matter get into the system along with the wastepaper and end up as various solid wastes. Biological treatment of mill effluents also produces large amounts of sludge. Disposal of the solid wastes presents an onerous task for the industry. Thus, we tried the catalytic hydrothermal conversion (CHTC) technology using alkali salt (Na2CO3) to catalyze the formation of hydrogen and carbon monoxide at mid-temperature (> 800℃) and atmospheric pressure. The process might be a viable technique for disposing of organic solid wastes and recovering the energy contained therein, thereby effectively reducing the volume. In trial process, rejects from wastepaper-based paper mills and their sludge were tested. Sericite (a mica mineral) was found to facilitate heat transfer and enable good conversion efficiencies. In the first series, reacted ashes had less than 5% volatile substances, indicating effective volume reduction, even with the passive mode of reaction (no steam injection or agitation) and more than 40% hydrogen emissions in the flue gas. Overall we deemed the process viable, but reactor design must enable good mixing and high-temperature steam injection to arrive at the potential optimal reaction conditions.