Demonstration of Pilot-scale Bio-dimethyl ether Synthesis Via Oxygen- and steam- enriched Gasification of Wood Chips

The demonstration operation of an pilot-scale bio-dimethyl ether(DME) synthesis system was carried out for with 300-350 kg/h of wood chips as feedstock. The tar content was 4.4-5.7 g/Nm3 and carbon percent in the residual char was low due to the combined advantages of the specific gasifier combining with upstream and downstream gasification with O2-rich air(46.3vol%), fed through the top and bottom inlets of the gasifier. Steam, as the secondary gasifying agent, also increased H2 content in the raw bio-syngas. The reforming of tar and light hydrocarbons further decreased tar content to 0.42-0.67 g/Nm3 over Ni-MgO/γ-Al2O3 cordierite monolithic catalysts with less than 5.0vol% of CH4 content in the raw bio-syngas. CO2 removal efficiency was about 70% by pressure-swing unit(PSA), using propylene carbonate as adsorbent. CO conversion and space-time yield of DME over Cu/Zn/Al/HZSM-5-packed fixed-bed tubular reactor were 61.4-71% and 90.4-155.8 kg/mcat3/h respectively when the gas hourly space velocity(GHSV) was 650-1500 h-1 at 220oC and 4.3 MPa. The selectivity of methanol and hydrocarbons were than less 3% under the typical operation condition. About 15.7% carbon of dried wood chip was converted to DME with the production cost of ca. ¥4810/ton DME.