NOVELTY - An automatically deslagging main gas tank of biogas digester, comprises a septic tank (1) which is connected to the main gas production pool (2) via compressed feed pipe (6) and can form pressure difference with the main gas production pool, and a gas outlet pipe (4) which is mounted on the top of the main gas production pool, where the bottom of the main gas production pool is equipped with an annular sealing groove (7) which is connected with the compressed feed pipe. The annular sealing groove is equipped with spray orifice (8).    USE - As an automatically deslagging main gas tank of biogas digester (claimed).    ADVANTAGE - The automatic deslagging main gas tank of biogas digestor avoids the use of additional mechanical equipments, and saves power, manpower and energy; and achieves the purpose of automatically deslagging.    DETAILED DESCRIPTION - Automatically deslagging main gas tank of biogas digester, comprises a septic tank (1) which is connected to the main gas production pool (2) via compressed feed pipe (6) and can form pressure difference with the main gas production pool, and a gas outlet pipe (4) which is mounted on the top of the main gas production pool, where the bottom of the main gas production pool is equipped with an annular sealing groove (7) which is connected with the compressed feed pipe. The annular sealing groove is equipped with spray orifice (8). The compressed feed pipe is equipped with movable cover (9) which is connected to the inner wall of the main gas production pool. The lowest position of the bottom of the main gas production pool is mounted with a discharging pipe (5) which is connected with waste pool (3), where the waste pool is connected with the septic tank via circulation pipe (10).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of an automatically deslagging main gas tank of biogas digester.    Septic tank (1)    Main gas production pool (2)    Waste pool (3)    Gas outlet pipe (4)    Discharging pipe (5)    Compressed feed pipe (6)    Annular sealing groove (7)    Spray orifice (8)    Movable cover (9)    Circulation pipe (10)