Decomposing furnace for SNCR denitration system

The utility model provides a decomposing furnace for an SNCR (selective non-catalytic reduction) denitration system. The decomposing furnace comprises a necking section, a conical section expansion joint, a decomposing furnace conical section, a decomposing furnace straight section and a decomposing furnace gooseneck section which are sequentially communicated with one another, a smoke chamber isconnected below the necking section through a transition section; four tailing combustors are uniformly distributed on the circumferential surface of the conical section of the decomposing furnace atthe position 300mm above the conical section expansion joint; a platform is fixedly arranged on each of the left side and the right side of the outer wall of the conical section of the decomposing furnace, two distributing valves are mounted on each platform, a kiln tail main pulverized coal pipeline guides two paths of pulverized coal to the distributing valves of the platforms through a distributing device, and the pulve