Effect of pretreatment biomass by gas from polyvinyl chloride dehydrochlorination process on maize cob pyrolysis with integrated CO2 capture

Abstract

This study investigates the effects of pretreatment of maize cob with hydrogen chloride gas obtained from polyvinyl chloride dehydrochlorination on pyrolysis yields and integrated CO₂ capture. The dehydrochlorination process was conducted at 320 °C, while the pyrolysis of the pretreated biomass was performed at 500 °C. Pretreatment significantly altered composition of biomass, reducing hemicellulose from 34.3 % to 3.7 %, increasing fixed carbon from 15.8 % to 20.3 %, and increasing the chlorine content from 0.27 % to 1.48 %. These changes influenced on the thermal decomposition characteristics of maize cob. During fast pyrolysis, the bio–oil yield increased by 17 %, from 32.9 % to 38.4 %, while gas production decreased from 38.7 % to 30.3 %, indicating a shift towards liquid biofuel production. Integration of calcium hydroxide in the pyrolysis reactor reduced CO₂ emissions by 87 %, from 56.5 % to 7.5 %, and captured chlorine from the pyrolysis gases, minimising harmful residues. Additionally, the use of calcium hydroxide facilitated the generation of hydrogen, increasing its content to 44.7 % in the gas phase. The bio–oil produced contained 0.8 % chlorine, demonstrating the effectiveness of in–situ chlorine capture. This approach, utilising hydrogen chloride derived from polyvinyl chloride waste, not only reduces environmental impact but also enhances the efficiency and sustainability of bio–oil production.