TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Device: In the medium-heat biomass fuel gas preparation device, the drive mechanism comprises a gear ring (21) fixedly connected to the outer wall of the furnace body, rolling rings (22) fixedly connected to the two ends of the furnace body (20) and a supporting wheel mechanism (19) matched with the rolling rings (22); the supporting wheel mechanism (19) is further equipped with a furnace body axial locating device (18) matched with the side walls of the rolling rings (22); the included angle of the axis of the furnace body (20) and the horizontal plane is 3-5 degrees ; a sealing device (5) is equipped between the front end of the furnace body (20) and the front end cover (4), and between the rear end of the furnace body (20) and the discharging device (13), respectively; the sealing device (5) can be three insertion maze seals; a movable insertion flange (24) is fixed to the front end cover (4) and the discharging device (13); the fixed insertion flange (25) matched with the movable insertion flange is fixedly connected with the furnace body (20); a soft heat resisting filler is filled between the movable insertion flange and the fixed insertion flange; the inner wall of the furnace chamber of the furnace body (20) is equipped with at least two sets of copying plates (8); each set of copying plates (8) is staggered along a generatrix; the adjacent copying plate sets are arranged at intervals; the charging device comprises a charging hopper (1), a winds topper (2), and a spiral conveyor (3) which are in parallel connected below the charging hopper (1); the tail end of the spiral conveyor (3) is equipped with a tapered charging cover (8) on the front end cover (4); the inner wall of the tapered charging cover (8) is equipped with a group of guide plates (8); the discharging cover (12) is equipped between the rear end of the furnace body (20) and the discharging device; the dry distillation gas outlet (26) is equipped on the upper part of the discharging device (13); the lower part of the discharging device (13) is connected with a storage tank (14), a sealer (16), and a biomass carbon collecting device (17) in sequence; the discharging cover (12) is tapered which is amplified towards one side of the discharging device (13); and the inner part of the storage tank (14) is equipped with cooling water spiral densely distributed pipelines (15).