TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The material overturning and conveying device further comprises a machine frame located below the variable-frequency motor for supporting. A coupling shaft is located on the machine frame. The lower part of the variable frequency motor is extended downwards along the main axis and it is connected to the central rotating shaft through the coupling shaft. An oil and graphite stuffing box is arranged at the bottom of the machine frame around the central rotating shaft. The machine frame is arranged below the variable frequency motor and located out side the central rotating shaft, and has a sealing isolation. The oil and graphite stuffing box is set in the circulating water cooling system for cooling the central rotating shaft. The variable frequency motor comprises a motor connected to a speed reducing mechanism and a transducer. The upper 1/4-1/3 length of the central rotating shaft extended out from the lower part of the machine frame is not covered with the blades. The upper rotary blade, middle rotary blade and lower rotary blade have different thread pitches. The thread pitch of upper rotary blade is greater than or equal to the thread pitch of the middle rotary blade and lower rotary blade. The thread pitch of the upper rotary blade is 50-100 mm, middle rotary blade is 30-80 mm and lower rotary blade is 30-80 mm. The upper rotary blade is located in the upper pyrolysis chamber of the biomass destructive distillation cracking device. The diameter of the upper rotary blade is 65-80 % of the diameter of the upper pyrolysis chamber. The distance between the blade edges of the upper rotary blade and the sidewall of the upper pyrolysis chamber is 30-50 mm. The middle rotary blade is located at lower part of the upper pyrolysis chamber. The lower part of the lower pyrolysis chamber extends downwards in the biomass destructive distillation cracking device. The diameter of the middle rotary blade is 85-95 % of the diameter of the lower pyrolysis chamber. The distance between the blade edges at the lower part of the middle rotary blade and the lower pyrolysis chamber is 5-10 mm. The lower rotary blade is located at the lower pyrolysis chamber. The height of the lower rotary blade is 20-30 % of the height of the lower pyrolysis chamber. The diameter of the lower rotary blade is 65-80 % of the diameter of the lower pyrolysis chamber. The distance between the blade edges of the lower rotary blade and the wall of the lower pyrolysis chamber is 15-25 mm. The diameter of the lower pyrolysis chamber is smaller than the diameter of the upper pyrolysis chamber. The upper pyrolysis chamber has a reduced diameter at its lower part. The middle rotary blade is located at the upper pyrolysis chamber, where the diameter is less and extends downwards to a distance of 50-100 mm in the lower pyrolysis chamber. The central rotating shaft and the upper rotary blade, middle rotary blade and lower rotary blade have resistance to 1000 degrees C and are made by chromium-nickel steel alloy of formula (OCr25Ni20).