Combustion of Salicornia bigelovii Pyrolysis Bio-oil and Surrogate Mixtures: Experimental and Kinetic Study

Abstract

Pyrolysis bio-oil (PBO), a renewable and sustainable alternative energy source, is gaining significant importance. PBOs are polar, viscous, and acidic in nature, which restrict their direct utilization. The blending of PBOs with fossil-based fuels in combustion processes can potentially reduce net carbon emissions. The utilization of PBOs in combustion systems warrants an understanding of their combustion chemistry, which serves as the motivation for this study. In this study, pyrolysis of a saltwater halophyte, Salicornia bigelovii, was performed to obtain PBO. Based on the PBO composition, a blend of pyrrole, furfural, and toluene was prepared as a surrogate. The combustion chemistry of a three-component surrogate comprising oxygen- and nitrogen-containing compounds is studied for the first time. To understand the gas-phase combustion chemistry of the PBO surrogate, experiments were performed in a jet-stirred reactor (JSR) at atmospheric pressure and a residence time of 2 s in the temperature range of 780–960 K (ϕ = 0.25). Also, the PBO surrogate was blended in the ratios of 10 and 20% (by wt) with a toluene/iso-octane (80/20 mol/mol) mixture and investigated to mimic the combustion of PBO with hydrocarbons. A detailed chemical kinetic mechanism was compiled using different sub-mechanisms for surrogate components. NUIGMech1.2 was used as the base mechanism. Fuel-reactant species and 17 product species were identified to understand the combustion chemistry of PBO surrogate and its blends. Furthermore, rate of production analysis was performed to understand the pathways vital for forming intermediates. In addition, the thermal stability of PBO was studied in a thermogravimetric analyzer in the temperature range of 105–750 °C in oxygen and nitrogen atmospheres. The mass loss and derivative mass loss profiles were acquired, different stages of the reactions were identified under the oxygen atmosphere, and the apparent kinetic parameters were determined via the Friedman method.