To provide a device capable of preventing breakage of a piping or a pump by blocking the piping with slurry.

When the slurry can be circulated to an upper part from a lower part of a tank A (1) through the piping (8) for a pump, reversible liquid delivery pump (9) and the circulation piping (4), can be delivered to a tank B (2) by the liquid delivery piping (5) branched from the circulation piping and can be changed over by opening and closing of a circulation valve 6 and a liquid delivery valve 7 arranged on the circulation piping and a branch downstream part of the liquid delivery piping, (a): the slurry is circulated in the tank A (1) in a state of the circulation valve closed, the liquid delivery valve closed and the liquid delivery pump normally rotated, (b): the slurry in the branch downstream part of the circulation piping is discharged by reversing the liquid delivery pump, (c): the slurry is delivered to the tank B (2) in a state of the circulation valve closed, the liquid delivery valve opened and the liquid delivery pump normally rotated and (d): the slurry is delivered in such a way to include a process to discharge the slurry in the liquid delivery piping by reversing the liquid delivery pump.