Rotary cement kiln pre-decomposition device

The utility model provides a rotary cement kiln pre-decomposition device which comprises a decomposition furnace, and the decomposition furnace comprises a necking section, a decomposition furnace conical section and a decomposition furnace straight section which are sequentially communicated with one another; a smoke chamber of the rotary kiln is connected below the necking section through a transition section; two tailing combustors are symmetrically mounted on the circumferential surfaces of the lower end and the middle end of the conical section of the decomposing furnace respectively; theleft side and the right side of the outer wall of the upper portion of a conical section of the decomposing furnace are each fixedly provided with a platform, two material distributing valves are installed on each platform, a kiln tail main pulverized coal pipeline guides two paths of pulverized coal to the material distributing valves of the platforms through a material distributing device, andthe pulverized coal is fin