Chemical looping gasification of microalgae biomass with Fe-based oxygen carrier for gas production and kinetic behavior

Abstract

Chemical looping gasification (CLG) is an efficient method for energy conversion and utilization. It is an emerging technology to convert bioenergy into high value gas through redox of oxygen carriers (OCs). In this paper, the pyrolysis process of Chlorella vulgaris(CV) with OCs was mainly divided into three stages by TG-FTIR-MS test. Using iron ore as OCs and quartz sand as blank experiment. The addition of OCs increases the reaction rate and exhibits a catalytic effect on tar cracking. The kinetic equations for Stage 2 and Stage 3 are dα/dt=3.12(1-α)³·exp(-1.62 × 10⁴/T) and dα/dt=5.49[(1-α)^2/3/(1-(1-α)^1/3)]·exp(-4.86 × 10⁴/T), respectively. The most probable mechanism functions are the reaction order models (O3) and the diffusion models (D3), respectively. The average activation energy E₀ and pre-exponential factor A₀ were 134.44 kJ/mol, 3.12 min^-1 and 404.18 kJ/mol, 3.66 min^-1 for Stage 2 and Stage 3, respectively. The CLG process of CV&OCs showed that the yields of CO₂, H₂ and CO were increase by the addition of OCs. The CO yield increased most significantly from 0.097 Nm³/kg to 0.313 Nm³/kg. The carbon conversion and gasification efficiency increased from 41.7 % and 43.4 % to 78.3 % and 54.9 %, respectively. Moreover, appropriately increasing the temperature can promote the deep pyrolysis gasification of CV and generate more pyrolysis gas with high value. The microalgae CLG power generation system was found to have less negative effects on the environment through LAC and is a worthwhile gasification technology.