Experimental and kinetic analysis of Bambusa tulda pyrolysis in carbon dioxide and nitrogen atmosphere

Abstract

Experiments were conducted using a fixed-bed pyrolysis system and a thermo-gravimetric analyzer to investigate the effect of $N_2$ and ${\mathrm{CO}}_2$ atmosphere on thermal degradation, physicochemical, structural, and elemental characteristics of Bambusa tulda and its char. A kinetic study was conducted at four different heating rates to determine the activation energy, pre-exponential factor, and kinetic model. The results indicate significant weight loss during the second stage of pyrolysis, primarily due to the thermal degradation of low molecular weight compounds such as hemicelluloses, cellulose, and a small fraction of lignin. The ${\mathrm{CO}}_2$atmosphere leads to more significant weight loss compared to$N_2$ atmosphere, with an average weight loss of about 80 % under $N_2$ and approximately 95 % under ${\mathrm{CO}}_2$. This difference is likely due to specific gas-phase reactions and the consumption of carbon fuel induced by ${\mathrm{CO}}_2$. Iso-conversional methods determined that the average activation energy of Bambusa tulda in the presence of $N_2$ was 160.05 kJ mol⁻¹, whereas under${\mathrm{CO}}_2$, it was 105.51 kJ mol⁻¹. The kinetic mechanism of B. Tulda for both the atmosphere was validated using Cardio’s master plots. The data points for activation energy and pre-exponential factors show a strong linear fit across incremental conversion fractions, indicating the presence of the kinetic compensation effect. Biochar produced in ${\mathrm{CO}}_2$ atmosphere (BCC) exhibited larger pores than biochar generated in $N_2$ atmosphere (BCN). BCN has a porous, organized structure, while BCC displays pores with a channel-like structure due to the development of an aromatic structure. The carbon content and calorific value of Bambusa tulda char are noteworthy, with values of 81.23 % and 25.36 MJ kg⁻¹ for N₂ atmosphere, and 85.16 % and 29.44 MJ kg⁻¹ for ${\mathrm{CO}}_2$atmosphere, indicating its potential as feedstock for the gasification process or as an alternative to fossil fuels.