Unit for roasting and milling large biomass particles in a fluidised bed, e.g. to make fine, dry wood particles for gasification, has 3 fluidising zones defined by a sloping wall, with a mill at the bottom

摘要

A unit for roasting and milling large particles (2-5 cm) of biomass in a fluidised bed, has two vertical walls (P1, P2) and inclined wall(s) (P3) defining three zones: (1) a lower zone with means of fluidising particles 2-5 mm in size and with a mill at the bottom, (2) a zone with means of fluidising particles of 1-2 mm and (3) an upper zone with means of fluidising particles smaller than 1 mm, in which the particle feed pipe (11) reaches down to the level of zone 2 and (P3) is at an angle of 30-60[deg] to the vertical. Independent claims are also included for (1) A method for roasting and milling biomass particles as above in which (2) the rate of particle fluidisation in zone 1 is 1.3-2.5 times the minimum rate for particles with a diameter of 1-2 mm (3) the rate in zone 2 is 1.3-2.0 times the minimum rate for particles with a diameter of 1-2 mm (4) the rate in zone 3 is 1.3-1.5 times the minimum rate for particles with a diameter of less than 1 mm (5) the average residence time of the largest biomass particles in the unit is 10-40 (preferably 15-30) minutes and (6) the temperature inside the unit is 230-300 (preferably 250-280) [deg] C .