Revealing roles of CO2 and N2 in pressurized hydrothermal carbonization process for enhancing energy recovery and carbon sequestration
Mingjing He, Yang Cao, Yinzheng Fan, Ondřej Mašek, James H. Clark, Daniel C.W. Tsang
Abstract
In this study, CO 2 – and N 2 -pressurized hydrothermal carbonization processes were investigated to understand the catalytic effects of CO 2 on hydrochar production and its quality ( e.g., surface properties, energy recovery, and combustion behaviour). Both CO 2 – and N 2 -pressurized HTC processes could enhance the energy recovery (from 61.5% to 63.0–67.8%) in hydrochar by enhancing the dehydration reactions. Nonetheless, the two systems exhibited contrasting trends in volatile release, oxygen removal, and combustion performance as a function of increasing pressure. High N 2 pressure enhanced deoxygenation reaction, facilitating the release of volatiles and increasing the hydrochar aromaticity and combustion activation energy (172.7 kJ/mol for HC/5N). Without the contribution of CO 2 , excessively high pressure may cause an adverse impact on the fuel performance owing to higher oxidation resistance . This study presents an important and feasible strategy to utilise CO 2 -rich flue gas in the HTC process to produce high-quality hydrochar for renewable energy and carbon recovery.