To reduce the running cost of a conveying pump by installing a spraying shower control valve in a shoot spraying shower inlet port side, carrying out a cleaning with a washing shower of a belt conveyor, and receiving wash water out of a recovery hopper with a sump pit, then transmitting it to a waste water treatment device.

The discharge of a shoot spraying shower is controlled by a shower control valve D and wash water to be fed to a waste water treatment device by a drain control valve E, respectively and in addition, a connecting control valve F is installed there. In addition, a coal stocking switch 14 to detect whether there is coal or not is installed on a belt conveyor 3, and a water level gauge 15 detecting a lower limit level is set up on a sump pit 9. Moreover, a flow meter 16 detecting an amount of discharge in the shoot spraying shower is installed at the downstream of the shower control valve D. An interval ranging from a distributing pump 10 to the drain control valve E and anther interval ranging from the shower control valve D to the flow meter 16 are connected by a connecting pipeline 17, and the connecting control valve F is installed in the point midway in this pipeline. The discharge of a spray shower 2 is detected by the flow meter 16, keeping the opening of the shower control valve D in the case where it is a specified value. With this constitution, an amount of running cast in a plant is reducible.