NOVELTY - A large continuously changed methane tank comprises a tank bottom (1) and a material inlet (2); where multiple fermenting ponds (4) which are arranged continuously are arranged in the methane tank and are communicated via corridor doors (3); the vault (8) of the fermenting pond (4) is continuously ellipse arc-shaped; an air outlet (10) is arranged on the vault (8); the fermenting pond located at the starting end in the fermenting ponds (4); and a ladder (6) and a pond discharging door (7) are arranged in the water pressure chamber (5).    USE - The large continuously changed methane tank is useful for industrial and commercial applications.    ADVANTAGE - The large continuously changed methane tank uses the structure that multiple fermenting ponds are connected in series, which increases the space for placing the organic matter on one hand, and increases the gas generating rate and using rate of the raw material via carrying out multiple anaerobic returning fermenting in the pond; thus, the substance in the slag which will pollute the environment is reduced. Moreover, the inclined surface structure is used by the tank bottom of the fermenting pond; thus, the organic matter can be flowed in the pond. Additionally, the vault is clamped sleeve double-layer structure; and the water is used in the sandwich layer to be protected, which can control the temperature of the vault and prolong the service life of the vault.    DETAILED DESCRIPTION - A large continuously changed methane tank comprises a tank bottom (1) and a material inlet (2); where multiple fermenting ponds (4) which are arranged continuously are arranged in the methane tank and are communicated via corridor doors (3); the vault (8) of the fermenting pond (4) is continuously ellipse arc-shaped; an air outlet (10) is arranged on the vault (8); the fermenting pond located at the starting end in the fermenting ponds (4) which are arranged continuously is communicated with the material inlet (2); the fermenting pond located at the tail end is communicated with a water pressure chamber (5); and a ladder (6) and a pond discharging door (7) are arranged in the water pressure chamber (5).    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the large continuously changed methane tank.    Tank bottom (1)    Material inlet (2)    Corridor doors (3)    Fermenting ponds (4)    Water pressure chamber (5)    Ladder (6)    Pond discharging door (7)    Vault (8)    Sandwich layer (9)    Air outlet (10)