title: Hydrothermal carbonization: process water characterization and effects of water recirculation.
abstract: Poplar wood chips were treated hydrothermally and the increase of process efficiency by water recirculation was examined. About 15% of the carbon in the biomass was dissolved in the liquid phase when biomass was treated in de-ionized water at 220 °C for 4 h. The dissolved organic matter contained oxygen and was partly aerobically biodegradable. About 30-50% of the total organic carbon originated from organic acids. A polar and aromatic fraction was extracted and a major portion of the organic load was of higher molecular weight. By process water recirculation organic acids in the liquid phase concentrated and catalyzed dehydration reactions. As a consequence, functional groups in hydrothermally synthesized coal declined and dewaterability was enhanced. Recirculated reactive substances polymerized and formed additional solid substance. As a result, carbon and energetic yields of the produced coal rose to 84% and 82%, respectively.
authors.affiliation: Department of Energy Technology, Technische Universität Berlin, Marchstrasse 18, 10587 Berlin, Germany. jan.stemann@bam.de
authors.forename: Jan
authors.initials: J
authors.lastname: Stemann
authors.forename: Anke
authors.initials: A
authors.lastname: Putschew
authors.forename: Felix
authors.initials: F
authors.lastname: Ziegler
mesh_terms: D018533:Biomass; D002244:Carbon / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D002244:Carbon
keywords: Accumulation; Dissolved organics; Energetic yield; Organic acids; Polymerization