Experimental investigation of oxy-combustion using plastic waste pyrolysis fuel for CO2 capture technology

In response to the worsening environmental and energy crises, strategic research on plastic disposal (pyrolysis) and CO₂ negative application (oxy-fuel combustion) was carried out. The upgraded plastic pyrolysis oil was used to evaluate the performance of oxy-fuel combustion in a 5-kW scale boiler. Plastic oil middle distillate (diesel-like fraction, C₁₁-C₂₂) exhibits similar characteristics to diesel (e.g. HHV: 45.0 MJ/kg, viscosity: 2.70 cSt at 40 °C), resulting in a perfect miscibility. The 30 %P-oil (mixed fuel of plastic middle fraction pyrolysis oil for 30 wt% and petroleum diesel for 70 wt%) and pure diesel were applied for the oxy-fuel combustion study, respectively. The boiler efficiency of 30 %P-oil was about 62 %, close to pure diesel combustion (∼61 %), higher than air combustion (∼58 %) with mixed fuels in our previous study. The maximum boiler internal temperature was observed at 1080–1090 °C at 25 %O₂ and 75 %CO₂ of inlet gas concentration. Emission analysis showed that both the 30 %P-oil and diesel combustion emitted similar flue gas concentrations of CO (80–120 ppm), SO₂ (6–9 ppm) and CO₂ (∼95 %) at 25 %O₂ condition. On the other hand, 30 %P-oil showed higher NO concentration (61 ppm) than diesel (20 ppm) because of higher presence of the nitrogen content in plastic pyrolysis oil. Finally, highly concentrated CO₂ (∼95 %) was captured over oxy-fuel combustion, leading to CO₂-negative technology.