The invention provides a method and a device for preparing synthesis gas by
biomass pyrolysis and gasification. The method comprises three stages of
roasting at low temperature, catalytically gasifying at high temperature, and reforming through
microwave; the three stages are respectively continuously performed in three relatively-independent spaces in a gasifying device, so as to obtain high-quality synthesis gas. The device comprises a double-shaft spiral
pyrolysis reactor which is equipped with a
roasting section at the front section, a gasifying section at the medium section, and a
microwave assisting reforming section at the
tail section; raw materials are fed into the double-shaft spiral
pyrolysis reactor through a feeding device; the way of combining internal heat and external heat which are produced by
smoke heat exchange, heat carried by a catalyst and
microwave assisting heating is adopted to provide proper temperature of the three reaction stages to achieve staged pyrolysis and gasification; the produced gas is processed by a
gas solid separator to obtain the synthesis gas; meanwhile, the deactivated catalyst and carbon
coke and the like discharged by the reactor are fed into a
combustion furnace to generate high-temperature
smoke and regenerate the catalyst. With the adoption of the method and the device, the process
system for preparing the synthesis gas can be simplified, the semi-
coke and
tar contents in pyrolysis and gasification can be decreased, and the gasifying efficiency of the
system and the quality of the synthesis gas can be improved.