GASIFICATION OF HERBAGE IN SUPERCRITICAL WATER, EXPERIMENTAL RESULTS

摘要

The gasification of fresh herbage (grass) in supercritical water has been optimized in a lab-scaleapparatus and then has been tested in the pilot-plant scale. A high gasification yield is possible. The product gasconsists of hydrogen, methane and some short chain hydrocarbons. The pretreatment of fresh herbage is complex.Sand should be removed by washing, size reduction with cutting devices and dilution to less than 10 wt. % DM. Anenzymatic treatment at elevated temperatures for 24 h is useful for the subsequent gasification. Optimized processconditions are temperature of 650 ℃, pressure of 28 MPa and mean residence time of 2 – 4 min; the resultinggasification yield of 98 % is high, also the hydrogen concentration. CO_2 can be removed by a water scrubber at apressure of 10 – 20 MPa. Due to technical boundaries the reaction temperature in the pilot-plant experiments waslower and consequently the gasification yield was lower.