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.