Taguchi-optimized oxy-combustion of hydrochar/coal blends for CO2 capture and maximized combustion performance

The oxy-combustion of solid fuels has been proposed as an effective and promising approach for CO2 capture by recirculating the generated flue gas within the combustion system. However, performing the process under non-optimal conditions could lead to undesirable combustion performance. In this work, the optimization of oxy-combustion conditions for fuel blends of pomelo peel derived hydrochar (PPH) and coal was performed by the Taguchi method to achieve the best oxy-combustion performance through optimal conditions. Thermogravimetric analysis, single pellet combustion, and thermogravimetry-coupled infrared spectroscopy (TG-IR) were used to investigate combustion behavior, flame characteristics and exhaust gases, respectively. The results showed that the best performances for post-combustion ash (16.18%) and activation energy (25.70 kJ/mol) were achieved using the blending ratio of 5:5 (coal:PPH). In addition, experiment CG07 (with blending ratio of 5:5 and carrier gas of CO2:O2 = 40:60) showed the highest combustibility characteristic (S) index (15.88 × 10−11), which suggested that these conditions were also optimal for the best combustibility. Flame observation illustrated that the fuel blends showed enhanced flammability and combustibility. In addition, TG-IR analysis showed that blended coal/hydrochar fuel had reduced CO2 peak intensity (0.20 Abs) compared to unblended coal (0.27 Abs). This work proved that under optimal oxy-combustion conditions the combustion performance can be maximized.