Effects of process severity on product formation in hydrothermal carbonization of kitchen waste
摘要
Kitchen waste (KW) can be converted into fuels and substrates used for the production of chemical compounds. Hydrothermal carbonisation (HTC) is a suitable method to use KW for this purpose. Tests were carried out in a pressure reactor, varying the temperature (180–250 °C) and residence time (0.5–3.5 h). As the temperature of the HTC process increased, the hydrochar production decreased. Hydrochar obtained at higher temperatures and longer residence times was characterised by lower volatile matter content (53.2%), a higher calorific value (28.5 MJ kg−1) and a higher surface area (4.69 m2 g−1). During the combustion of the hydrochar, it was observed that the fuel properties improved with increasing process severity. In the pyrolysis and gasification processes, higher quality products were obtained from hydrochar produced at higher temperatures. In the liquid fraction, growth severity in the HTC process caused an increase in acetic acid concentration (from 1.69 to 3.10 g dm−3) and a decrease in TOC (from 22.3 to 11.9 g dm−3) and TN (from 0.80 to 0.61 g dm−3). Analysis of the volatile organic compounds in the liquid showed that the number of ketones and phenols increased with the severity of the HTC process. Increasing the severity of the HTC process led to an increase in the gas production from 1.35 to 10.03%, consisting mainly of CO2.