2.1. Gasification test in the MIUN gasifier
Fig. 1. The 150 kWth MIUN SEA0400 DFBG gasifier.Figure optionsDownload full-size imageDownload as PowerPoint slide
The tar content in raw untreated syngas from the MIUN gasifier with silica sand is approx. 20 g/Nm3 or more. The concentration of CH4 is about 10% corresponding to one third of syngas energy, which cannot join the downstream synthesis reaction for liquid fuels. The content of tars and CH4 in the syngas from the MIUN gasifier needs to be reduced to an acceptable low level.
Hence, internal tar/CH4 reforming with catalytic bed materials needs to be investigated in detail. These tests are carried out in both BFB mode and DFB mode to compare the bed materials under different gasification conditions. The tar/CH4 reforming test runs in three cases: 1) basic condition with silica sand (no catalytic activity), 2) calcined olivine, 3) Fe-impregnated olivine (10%wtFe/olivine Catalyst), at the temperatures of 750, 800, 850 and 900 °C, and at the steam-to-carbon (S/C) ratios of 0.6, 1.2 and 1.8 in weight (kg/kg). The S/C ratio is calculated according to equation (7).equation(7)S/C=m˙steam+νH2O×m˙biomassνC×m˙biomasswhere m˙steam represents the mass flow of steam (kg/s)m˙biomass represents the flow of biomass (kg/s)νC represents the carbon mass fraction in the biomassνH2OνH2O represents the water mass fraction in the biomass