Low-rank coal pyrolysis rotary kiln capable of recycling pyrolysis gas

The invention discloses a low-rank coal pyrolysis rotary kiln capable of recycling pyrolysis gas, which comprises a rotary kiln body and pyrolysis gas circulating conveying equipment, and the pyrolysis gas circulating conveying equipment comprises a separation device and a sweeping device, the separation device comprises a processing part, a separation piece, a connection part, a three-way valve, a control unit, a rotating shaft, a blocking piece, a longitudinal separation piece, a fluid channel and an energy storage part, and the sweeping device comprises a ratchet disc, a strip-shaped assembly piece, a ratchet strip, an inverted-U-shaped sliding plate, a loading box, a connection seat and a sweeping tool. According to the pyrolysis gas circulating conveying equipment, the separation device and the sweeping device are spliced in a moving connection mode, the separation device and the sweeping device are spliced into the whole pyrolysis gas circulating conveying equipment in the moving connection mode, then r