NOVELTY - A small-size movable quick thermal cracking device comprises advancing mechanism (25), combustion furnace (18), feeder (21), quick thermal cracking reactor (22), gas-solid separator (23), gas condenser (11), uncondensable gas purifying device (24), fan (16), gas buffer tank (17) and gas pre-heater (19). The quick thermal cracking reactor consists of inverted conical air inlet chamber, barrel-shaped reaction segment with changeable height, reactor top cover, and flat air distributing plate. The reactor top cover is provided with an inverted conical gas stabilizer.    USE - A small-size movable quick thermal cracking device for agricultural and forest biomass.    ADVANTAGE - The quick thermal cracking reactor has an adjustable height so as to be suitable for all kinds of agricultural and forest biomasses. The inverted conical gas stabilizer in the top cover of the reactor makes good flowing quality in the reactor; and the uncondensable gas is used as the ejection gas, the flowing gas source, and the heat supplying fuel. The device is simple in structure, small in volume and stable in operation, and can be transported to a place where the agricultural and forest biomasses are concentrated to produce at a low cost. Such working method of small size movement avoids the problem that the industrialized magnification of the fluidized bed reactor is difficult and realizes industrialized production of agricultural and forest biomass through quick thermal cracking in an innovative way.    DETAILED DESCRIPTION - A small-size movable quick thermal cracking device comprises an advancing mechanism (25), a combustion furnace (18), a feeder (21), a quick thermal cracking reactor (22), a gas-solid separator (23), a gas condenser (11), an uncondensable gas purifying device (24), a fan (16), a gas buffer tank (17) and a gas pre-heater (19). The gas outlet of the gas pre-heater is connected with the gas inlet at the bottom of the cracking reactor, while the heat exchanging medium inlet of the gas pre-heater is connected with the smoke outlet of the combustion furnace, the combustion gas inlet of which is connected with the gas buffer tank. The quick thermal cracking reactor is a small-size fluidized bed reactor, having an inner diameter of 0.1-0.3 m and a total height of 1.6-2 m; consists of an inverted conical air inlet chamber at the bottom, a barrel-shaped reaction segment with changeable height and a reactor top cover at the middle, and a flat air distributing plate between the inverted conical air inlet chamber and the reaction segment. The bottom of the inverted conical air inlet chamber is provided with a gas inlet. The reaction segment is made up of at least one barrel-shaped reaction pipe, where one or more reaction pipes with the same diameter and different heights can be installed according to need so as to change the height of the quick thermal cracking reactor. The center of the reactor top cover is provided with gas outlet, and its inside is provided with an inverted conical gas stabilizer sharing the same axis with the gas outlet and having a conical angle of 90 degrees , and the ratio of the diameter at the bottom of the cone to that of the gas outlet is (1.2-1.5): 1. The ratio of the distance from the conical bottom to the gas outlet to the total height of the quick thermal cracking reactor is (0.2-0.3): 1. The other devices except the advancing mechanism are all installed on the advancing mechanism. The flat air distributing plate is composed of a round plate and a steel wire mesh having a size of 100-180 meshes. The gas-solid separator is a two-level cyclone separator; and the bottom of the cyclone separator at each level is connected with a carbon collecting box.    DESCRIPTION OF DRAWING(S) - The drawing is schematic diagram illustrating the small-size movable quick thermal cracking device.    Inverted conical air inlet chamber (5)    Gas condenser (11)    Fan (16)    Gas buffer tank (17)    Combustion furnace (18)    Gas pre-heater (19)    Feeder (21)    Quick thermal cracking reactor (22)    Gas-solid separator (23)    Uncondensable gas purifying device (24)    Advancing mechanism (25)