Hydrogen production by supercritical water gasification of black liquor: Use of high temperatures and short residence times in a continuous reactor

The Supercritical Water Gasification (SCWG) of black liquor (BL) to obtain hydrogen and dispose of organic waste simultaneously has been studied in a continuous reactor employing short residence times. The experiments were conducted at 600-700 degrees C, with times between 24.5-29.1 s, at 23 MPa and feedstock was diluted to different concentration levels (0.81-2.43 wt.%). Furthermore, different NaOH concentrations (0-1.2 wt.%) were added to maintain a basic medium and avoid the polymerization of the compounds. Hydrogen production and COD removal was conducted with short residence times. The best results regarding hydrogen yield were achieved at 700 degrees C, 24.5 s residence time and 0.9 wt.% NaOH concentration, with a production of 38.68 mol H-2/kg(sample). In contrast, and regarding COD removal, the best results were obtained at 700 degrees C, with 24.5 s residence time and the highest feed COD concentration used (2.43 wt.%). The COD removal levels reached were between 65-90 %. (C) 2020 Elsevier B.V. All rights reserved.