Sunday, April 29, 2007

Thermochemical liquefaction of corn components: Heat transfer, process and mechanism

Bo Zhang1, Marc von Keitz2, and Kenneth Valentas2. (1) Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave, Saint Paul, MN 55108, (2) BioTechnology Institute, University of Minnesota, 1479 Gortner Avenue, Suite 240, St. Paul, MN 55108

The corn components, corn stalk, corn leaf, corn cob, corn stover, and corn stover pellet, were liquefied in a batch pressure vessel equipped with an induction heating system, which allows the reduction of heat-up times by about two orders of magnitude.  Various corn components show different densities, but similar compositions, and do not seem to affect the yield and composition of bio-crude oils.  The direct conversion of corn stover pre-treated with dilute acid and lignin extracted from corn stover, were also studied to evaluate suitability as the raw material for producing bio-crude oil.  Liquefaction process of corn stover was optimized using the following treatment variables: heating rate (5-140°C /min), cooling rate (4-80°C /min), reaction temperature (300-450 °C, corresponding to a pressure range of 3000-5000 PSI), reaction time (1-30 min), particle sizes, and catalysts.  The yields of bio-crude oil were found to depend on heating rate, final liquefaction temperature, the length of reaction time.  The major compounds from biomass liquefaction were identified and quantified by GC-MS.  The mechanism of liquefaction reactions was proposed.