NOVELTY - A circulating water purification device comprises a shell and three filters. The lower part of the filter is arranged in the shell and matched with the shell to form two sedimentation cavities. The filter comprises an outer cylinder, an upper flange, a flange cover, a water inlet pipe, a Venturi tube, a shutter grid, a film filtering device, a supporting ring, a water outlet pipe, a drainage valve, a decontamination pipe, a decontamination flange and a flange cover.    USE - Circulating water purification device for straw gasification system.    ADVANTAGE - The device is simply structured, convenient to maintain, safe and reliable.    DETAILED DESCRIPTION - A circulating water purification device comprises a shell and three filters. The lower part of the filter is arranged in the shell and matched with the shell to form two sedimentation cavities. The filter comprises an outer cylinder, an upper flange, a flange cover, a water inlet pipe, a Venturi tube, a shutter grid, a film filtering device, a supporting ring, a water outlet pipe, a drainage valve, a decontamination pipe, a decontamination flange and a flange cover. The water inlet pipe penetrates through the outer cylinder. The tangent direction is accessed on the upper part of the Venturi tube and inclined at 75 degrees with the axis of the Venturi tube. The lower end of the Venturi tube is connected with an inner hole of the shutter grid. The outer edge of the shutter grid is connected with the outer cylinder. The film filtering device is installed on the Venturi tube in the outer cylinder and connected with the supporting ring welded on the inner wall of the outer cylinder by a bolt. The water outlet pipe is connected with the outer cylinder on the film filtering device. The other ends of the water outlet pipes on two front filters penetrate through an upper sealing plate and extend to the lower parts of the sedimentation cavities. The water outlet pipe of a third filter is welded with the flange as a connecting port with the outer pipeline. The upper flange is connected with the upper end of the outer cylinder. The flange cover is tightly fixed with the upper flange by a bolt. One side of the lower part of the outer cylinder is provided with the decontamination pipe. The other end of the decontamination pipe is connected with the decontamination flange. The other side of the lower part of the outer cylinder is connected with the drainage pipe; and the other end of the drainage pipe is connected with the drainage valve.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a circulating water purification device.