A powder discharge system having a circulating water tank for collecting powder generated when an exhaust gas is treated in an exhaust gas treatment apparatus , the powder discharge system comprising: at least one eductor provided in the circulating water tank ; the eductor comprising a nozzle configured to throttle a flow of water supplied from a pump (P) for pumping water in the circulating water tank , a suction port configured to suck water in the circulating water tank into the eductor by utilizing a reduction of pressure generated when the flow of water is throttled by the nozzle , and a discharge port (3 OUT ) configured to eject the water sucked from the suction port together with the water discharged from the nozzle toward a bottom of the circulating water tank to crush powder deposited on the bottom of the circulating water tank and to float the powder; and a drainage port provided in the circulating water tank to discharge the floating powder through the drainage port from the circulating water tank together with drainage water; wherein the water is ejected from the discharge port (3 OUT ) of the eductor ; and means for controlling a water level of the circulating water tank to form a state where the water level is lower than the suction port of the eductor and a state where the water level is higher than the suction port of the eductor ; wherein, when the water level is lower than the suction port of the eductor , only the water discharged from the nozzle is ejected from the eductor toward the bottom of the circulating water tank ; and wherein, when the water level is higher than the suction port of the eductor , the water discharged from the nozzle and the water sucked from the suction port are ejected from the eductor toward the bottom of the circulating water tank . at least one eductor provided in the circulating water tank ; the eductor comprising a nozzle configured to throttle a flow of water supplied from a pump (P) for pumping water in the circulating water tank , a suction port configured to suck water in the circulating water tank into the eductor by utilizing a reduction of pressure generated when the flow of water is throttled by the nozzle , and a discharge port (3 OUT ) configured to eject the water sucked from the suction port together with the water discharged from the nozzle toward a bottom of the circulating water tank to crush powder deposited on the bottom of the circulating water tank and to float the powder; and a drainage port provided in the circulating water tank to discharge the floating powder through the drainage port from the circulating water tank together with drainage water; wherein the water is ejected from the discharge port (3 OUT ) of the eductor ; and means for controlling a water level of the circulating water tank to form a state where the water level is lower than the suction port of the eductor and a state where the water level is higher than the suction port of the eductor ; wherein, when the water level is lower than the suction port of the eductor , only the water discharged from the nozzle is ejected from the eductor toward the bottom of the circulating water tank ; and wherein, when the water level is higher than the suction port of the eductor , the water discharged from the nozzle and the water sucked from the suction port are ejected from the eductor toward the bottom of the circulating water tank . <EOS>