External carbon supplementing device for agricultural greenhouse

The utility model relates to the technical field of carbon supplementing equipment, and discloses an agricultural greenhouse external carbon supplementing device which comprises a combustion box, the top face of the combustion box is fixedly communicated with a fixing pipe, the top face of the fixing pipe is fixedly communicated with an air pipe, and air holes are formed in the bottom face of the outer surface of the air pipe. The mounting rod is fixedly sleeved with the middle plate, the sealing cover is sleeved with the end face of the air pipe in a threaded mode, the sealing cover is movably sleeved with the mounting rod, the limiting ring located on the outer side of the sealing cover is sleeved with the outer surface of the mounting rod in a threaded mode, and the limiting ring is rotated irregularly in the using process; and then a mounting rod and a middle plate are driven to rotate, so that an arc-shaped cleaning plate rotates along the inner wall of the air pipe, ash attached to the inner wall of the