Chemical hot gas cleaning of Alkali, Chlorine, and Sulphur species in a sorption enhanced gasification process at 650 °C

• GICO-Project converts biomass to biofuel via advanced gasification technology. • CaO reduces CO 2 , H 2 S, and HCl in gasifier but needs secondary cleaning. • New sorbents are explored for effective hot gas cleaning at 650 °C. • Ba-, Sr-, and Ce-sorbents achieve H 2 S below 1 ppm v , preventing catalyst poisoning. • Aluminosilicates reduce KCl to below 1 ppm v for over 20 h. The European GICO-Project aimed to develop an advanced approach to convert energy from biomass into biofuel and on-demand power production. In the GICO-Process, a H 2 -rich hot gas stream of a gasifier operating at 650 °C has to be cleaned from inorganic contaminants, e.g. H 2 S, HCl, and KCl, to protect downstream equipment, e.g. membranes, SOFC and a plasma reactor from corrosion. The use of CaO as a primary sorption material in the gasification reactor reduces the CO 2 amount by forming CaCO 3 . Moreover, CaO reduces the H 2 S and HCl concentration in the gasifier by forming CaS, respectively CaCl 2 . However, previous studies have shown that these reactions are not sufficient to reduce the H 2 S and HCl concentrations below the demanded 1 ppm v goal. Thus, secondary hot gas cleaning is necessary. As standard sorbents are only used at temperatures up to 600 °C, further consideration of new sorbents developed and investigated in this work is of particular interest. Thermodynamic model calculations and sorption experiments in lab-scale furnaces were conducted to determine if chemical hot gas cleaning concepts can effectively remove sour gas and alkali components from the syngas leaving a gasification unit operating at 650 °C. In contrast to other studies, gases such as CO 2 , H 2 O, H 2 , and CO were not substituted in the sorption experiments. This realistic gas composition represents a novel approach at 650 °C, allowing for more representative and reliable experimental results. Using a mass spectrometer, it was possible to record the H 2 , CO 2 , H 2 S, and HCl concentrations during the sorption experiments simultaneously, although the input concentrations of the gas components (H 2 : 72 vol-%, CO 2 : 1 vol-%, H 2 S: 60 ppm v and HCl: 40 ppm v ) were differing strongly. Zinc titanate, as a conventional sulfur sorbent, reduced the H 2 S concentration in the experiments to around 7 ppm v . Ba-, Sr-, and Ce-containing sorbents achieved H 2 S concentrations below 1 ppm v for several hours, which should be sufficient to prevent poisoning of the nickel catalyst. 6 aluminosilicates, i.e. Bauxite, Clinoptilolite, Kaolin, Bentonite, Montmorillonite, and Cat litter, have been proven to be suitable for KCl reduction to values below 1 ppm v .