CO2-assisted gasification of Patagonian rosehip bio-wastes: Kinetic modeling, analysis of ash catalytic effects, and product gas speciation

Abstract

In the present study, the valorization of two rosehip wastes –husk and seed– was performed, through the CO2 gasification of biochar obtained by pyrolysis. The kinetics of gasification in a CO2 atmosphere at different partial pressures was investigated, obtaining the activation energy (E), pre-exponential factor (A), conversion function (f(α)), and reaction order with respect to the partial pressure of CO2 (x). The rosehip seed waste biochar (RSWB) yielded the following parameters: E = 302.11 kJ/mol, A = 2.18×1012 1/(s atm0.64), f(α) = ; while the rosehip husk waste biochar (RHWB) results were: E = 198.60 kJ/mol, A = 2.13 × 1008 1/(s atm0.64), f(α) = . The reaction order was the same in both wastes and equal to 0.64. The greater reactivity of RHWB can be attributed to the catalytic effects of the ashes contained in the biomass. To evaluate this effect, tests were conducted on rosehip husk waste ash mixtures with orthoasphaltite mineral char in proportions of 1, 5, 7, and 10 % (m/m). Thermogravimetry determined that the gasification temperature decreased up to 200 °C compared to pure char. Additionally, dry gasification of raw biomass experiments were carried out, and the evolution of gaseous products was analyzed with FTIR spectroscopy, evaluating the absorbance profiles of CO, CH4, and CH3OH, and comparing them with those obtained in a pure N2 atmosphere. The results obtained demonstrated the potential of rosehip wastes as a source in thermochemical processes for its complete valorization in a production chain with a focus on biorefinery.