Combustion global kinetic model of an industrial hydrochar

Abstract

This research analyzes the thermal and kinetic behavior of the combustion of hydrochar obtained industrially from green waste biomass. The combustion kinetic analysis was studied using thermogravimetry and applying complementary methods such as Friedman´s isoconversional analysis, mathematical deconvolution, combined kinetic analysis, and optimization by non-linear regression of the kinetic curves. The process involves two overlapping steps: the organic compounds devolatilization and the oxidation of fixed carbon. For steps 1 and 2, the apparent activation energies were 178.5 and 183.1 kJ mol-1, while the apparent ln⁡(A/s^(-1)) were 31.2 and 30.0, respectively. The truncated Šesták-Berggren model was used as a surrogate for distributed reactivity, resulting in n_1 = 1.37 and m_1 = -0.54 for step 1, and n_2 = 3.31 and m_2 = 0.496 for step 2. In step 1, the m < 0 serves as a surrogate for an activation energy distribution. While in step 2, the value of n > 1 would substitute a gamma distribution of frequency factors. Finally, the obtained kinetic model allows successful predictions of thermal programs outside the range of the analysis.