Large-scale biogas anaerobic digestion reactor and method for producing biogas

The invention discloses a large-scale biogas anaerobic digestion reactor and a method for producing biogas. The large-scale biogas anaerobic digestion reactor comprises a tank body, wherein the tank body is internally provided with an annular heating coil and comprises a primary agitator and three secondary agitators; a communicating device and a circulating pump are arranged outside the tank body; the communicating device is communicated with the inside of the tank body through a vent pipe and a liquid pipe; a pump front pipe connected with the communicating device is arranged at a water inlet of the circulating pump; a pump rear pipe is arranged at a water outlet of the circulating pump; the pump front pipe is connected through a plurality of liquid outlet branch pipes which extend fromthe tank wall to the bottom of the tank body through a liquid outlet main pipe; and the pump rear pipe is connected with a liquid return main pipe which extends from the tank top to the upper part ofthe tank body. According t