Chemical hot gas cleaning concept for the “CHRISGAS” process

The aim of the CHRISGAS project was the development of a gasification technique to produce clean hydrogen-rich synthesis gas from biomass. In order to improve the process efficiency, this work presents a gas cleaning concept, which combines chemical hot gas cleaning with hot (1 MPa, 900 °C) and warm (1 MPa, 300 °C) filtration. As the focus is set on the removal of H2S, HCl and KCl, calculations on chemical gas cleaning for the hot and warm gas filter were done using a thermodynamic process model using SimuSage™ (GTT-Technologies). The calculations show that Ca-based and Fe-based sorbents are not suitable H2S sorbents under the conditions of the hot gas filter. For Cu-based sorbents, H2S concentration below 100 cm3 m−3 is achievable, if the temperature is reduced below 810 °C. Additional calculations of KCl sorption on alumosilicates under the conditions of the hot gas filter show that the alkali concentration in gasifier-derived gases can be limited to 100 mm3 m−3. Thus, the condensation temperature of KCl can be decreased down to 580 °C. The results of HCl sorption calculations show that Na- and K-based sorbents are only suitable for temperatures below 600 °C. Therefore, the HCl sorption is transferred to the warm gas filter. The KCl sorption results were confirmed by experiments using bauxite, bentonite, kaolinite and naturally occurring zeolite as sorbents.

► Chemical hot gas cleaning for pressurized fluidized bed gasification of biomass. ► Laboratory experiments and thermodynamic model calculations. ► Aluminosilicates limit alkalis at 800 °C to < 0.1 cm3 m−3. ► Cu-based sorbents reduce H2S at 800 °C to < 100 cm3 m−3.