Design and operation of integrated pilot-scale dimethyl ether synthesis system via pyrolysis/gasification of corncob

The integrated pilot-scale dimethyl ether (dme) synthesis system from corncob was demonstrated for modernizing utilization of biomass residues. the raw bio-syngas was obtained by the pyrolyzer/gasifier at the yield rate of 40-45 nm(3)/h. the content of tar in the raw bio-syngas was decreased to less than 20 mg/nm(3) by high temperature gasification of the pyrolysates under o(2)-rich air. more than 70% co(2) in the raw bio-syngas was removed by pressure-swing adsorption unit (psa). the bio-syngas (h(2)/co approximate to 1) was catalytically converted to dme in the fixed-bed tubular reactor directly over cu/zn/al/hzsm-5 catalysts. co conversion and space-time yield of dme were in the range of 82.0-73.6% and 124.3-203.8 kg/m(cat)(3)/h, respectively, with a similar dme selectivity when gas hourly space velocity (ghsv, volumetric flow rate of syngas at stp divided by the volume of catalyst) increased from 650 h(-1) to 1500 h(-1) at 260 degrees c and 4.3 mpa. and the selectivity to methanol and c(2)(+) products was less than 0.65% under typical synthesis condition. the thermal energy conversion efficiency was ca. 32.0% and about 16.4% carbon in dried corncob was essentially converted to dme with the production cost of ca. (sic) 3737/ton dme. cu (111) was assumed to be the active phase for dme synthesis, confirmed by x-ray diffraction (xrd) characterization. (c) 2009 elsevier ltd. all rights reserved.

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