NOVELTY - Spiral type slag to biogas fermentation tank comprises coaxially arranged outer tank and inner tank body. A spiral flow guide plate provided between the inner wall and outer wall of the outer tank and inner tank body. The top end of the outer tank body is connected with a marsh gas output pipe. The part upper of the marsh gas output pipe is provided with a switch valve. A connecting inlet is provided with a biogas slurry overflow pipe. The overflow pipe outlet end is located close to the top end of the outer tank body.    USE - Useful as spiral type slag to biogas fermentation tank.    ADVANTAGE - The fermentation tank is provided with simple structure, is safe to use, ensures reliable and smooth operation in generating biogas, ensures automatic cleaning of biogas residues, and realizes biogas production cycle.    DETAILED DESCRIPTION - Spiral type slag to biogas fermentation tank comprises coaxially arranged outer tank and inner tank body. A spiral flow guide plate provided between the inner wall and outer wall of the outer tank and inner tank body. The top end of the outer tank body is connected with a marsh gas output pipe. The part upper of the marsh gas output pipe is provided with a switch valve. A connecting inlet is provided with a biogas slurry overflow pipe. The overflow pipe outlet end is located close to the top end of the outer tank body. The biogas slurry collecting tank and biogas slurry overflow pipe are provided with a first control valve. The first control valve is provided with a switch valve inlet orifice set on the bottom of the outer tank body. The feeding port is connected with output port of feed pump. The upper half part and lower half part of the outer tank body is provided with multiple biogas residue discharge pipe along the circumferential direction. The biogas residue discharge pipe is connected an inner cavity of the outer tank body. The biogas residue discharge control valve is set on the slag discharging pipe. The biogas residue discharge pipe and the biogas residue inlet pipe are respectively connected with inner cavity of the sedimentation barrel. The top end of the sedimentation barrel is respectively connected with a return gas pipe sedimentation barrel. The return gas pipe sedimentation barrel respectively connected with inner cavity of the outer tank body is provided with a second control valve. The sedimentation barrel upper return gas pipe is provided with a biogas residue discharge valve. The biogas residue discharge valve is set at bottom of the biogas residue sedimentation barrel.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the spiral type slag to biogas fermentation tank.