Sewage sludge co-gasification in a pilot-scale two-stage fluidized bed gasifier for improved hydrogen production: Effects on sewage sludge moisture, metal species, and metal loading amount

The abundant mineral olivine was applied as second-stage-gasifier bed materials to increase the H2 2 content in the syngas produced during the co-gasification of the sewage sludge and the simulated municipal solid waste. Regardless of the second-stage bed material used, the hydrogen-to-syngas ratio in the syngas output from the second stage increased when the S/B ratio increased from 0.02 to 0.13. This demonstrates that adding steam enhances the hydrogen-to-syngas ratio in the second-stage syngas. Under the same S/B conditions, the H2 2 content in the syngas varied when the original and modified olivine were separately used as bed materials in the second- stage gasifier. The H2 2 content was 23.12 mol.% when the original olivine was used and increased to 25.27 and 26.99 % mol.% when the olivine was respectively impregnated with 1 wt% Ni and 1 wt% Fe. These results evidenced that Ni and Fe could efficiently catalyzed the co-gasification of sludge and simulated municipal solid waste and improved the hydrogen production efficiency.