Use of bio-glycerol for the production of synthesis gas by chemical looping reforming

Abstract

Glycerol availabity, a waste generated in the production of biodiesel, has increased during last years. In this work, Chemical Looping Reforming (CLR) of glycerol has been demonstrated in a 1 kWth continuous unit during 35 h using a Ni-based oxygen carrier to obtain a high purity syngas without CO2 emissions. Complete conversion of the glycerol and syngas composition close to thermodynamic equilibrium was obtained in the fuel reactor. Moreover, pure N2 was obtained as product in the air reactor. The influence of the main operating variables on the composition and flow rates of synthesis gas was evaluated. The oxygen-to-glycerol molar ratio was the main parameter since the amount of lattice oxygen transferred by the oxygen carrier in the fuel reactor controlled the syngas composition. The increase of the water-to-glycerol ratio produced an increase in the production of H2 and CO2 with a decrease in the CO content, increasing both the syngas yield and the H2/CO molar ratio in the gas. Fuel reactor temperature affected mainly to the CH4 content, being lower as higher was the temperature. Close to autothermal conditions, it is possible to obtain a syngas composed by H2 ≈ 48–50 vol%; CO ≈ 30–35 vol%; CO2 ≈ 14–18 vol%; and CH4 ≈ 1.6–3 vol%. In addition, different H2/CO ratios can be obtained by modifying the H2O/glycerol ratio and temperature. A H2/CO ratio of 2 could be reached using either a H2O/glycerol ratio of 1.5 at 750 °C or a H2O/glycerol ratio of 2 at 800 °C.