Kinetics and experimental evaluation of hydrogen-rich synthesis gas from alkali lignin by chemical looping gasification with NiFe2O4 oxygen carrier

Chemical looping gasification (CLG) of alkali lignin with NiFe2O4 oxygen carrier was proposed to achieve hydrogen-rich syngas and realize the resource utilization of papermaking by-product, which exhibits advantages of cheaper oxygen source, lower reaction exergy loss, less tar content, and avoiding inert gas dilution in gas products. The kinetic behavior and reaction performance was evaluated by TG and fixed bed reactor coupled with thermal analysis kinetic of non-isothermal and heterogeneous systems. The results exhibited that the exogenous potassium alkali metal significantly reduced the average reaction activation energy from 182.62 kJ/mol to 142.16 kJ/mol and the CLG process conformed to the model of random nucleation and nuclear growth (n = 4). The presence of alkali metal and water molecules with the increasing temperature played a positive role in enhancing the CLG reaction process, adjusting the H2/CO ratio and improving the syngas yield and carbon conversion efficiency. Hydrogen-rich synthesis gas with H2 composition 57.67 %, LHV 13.28 MJ/m3, syngas yields 1.99 m3/kg, H2/CO 3.92 and carbon conversion 82.20 % was achieved in CLG of K-AAL with H2O molecular participation. The carbon conversion of K-AAL in CLG process is 28.78 % higher than that of AAL without alkali metal. The reaction path of NiFe2O4 oxygen carrier in CLG process was summarized as: NiFe2O4 → Fe0.5/Ni0.5 → Fe2O3/NiFe2O4. The CLG process is an effective way to prepare the synthesis gas for Fischer-Tropsch synthesis and realize the resource utilization of alkali lignin.