Vertical multi-stage washing device and method for preparing polyacrylonitrile-based carbon fiber precursor by using vertical multi-stage washing device

The vertical multi-stage washing device comprises a primary coagulating bath and a stretching component, the primary coagulating bath and the stretching component are fixedly connected through a heat insulation plate, the stretching component comprises a first-stage stretching module, a second-stage stretching module and a third-stage stretching module in sequence from bottom to top, and a hot roller is arranged on the side wall of each stage of stretching module; a detachable baffle is arranged between the stretching modules, a wire passing through hole is formed in the baffle, the first-stage stretching module is communicated with the primary coagulating bath through a small hole, and sealing buckle plates are arranged on the side walls, opposite to the side wall where the hot roller is located, of the second-stage stretching module and the third-stage stretching module. The vertical multi-stage washing device can be used for preparing polyacrylonitrile-based carbon fiber precursors. According to the vertic