Powder discharge system

An exhaust gas treatment apparatus comprising:

• a heat treatment unit for oxidatively decomposing an exhaust gas containing silane-based gas, including at least one of silane (SiH4) and disilane (Si2H6), discharged from a semiconductor manufacturing apparatus, the heat treatment unit comprising a combustion chamber for combusting the exhaust gas and a connecting pipe connected to the combustion chamber;
• an exhaust gas cleaning unit arranged at a stage subsequent to the heat treatment unit for cleaning the exhaust gas discharged from the combustion chamber with water and removing fine dust contained in the exhaust gas, the exhaust gas cleaning unit being connected to the connecting pipe of the heat treatment unit;
• and
• a powder discharge system having a circulating water tank for collecting powder containing silica (SiO2) generated when the exhaust gas is combusted in the combustion chamber of the heat treatment unit and for supplying the water to the exhaust gas cleaning unit to clean the exhaust gas and recovering the water after cleaning the exhaust gas, the connecting pipe of the heat treatment unit extending downward into the circulating water tank and configured to lead the powder containing silica (SiO2) into the circulating water tank, the powder containing silica (SiO2) generated when the exhaust gas is combusted being accumulated on an inner surface of the combustion chamber and removed from the inner surface of the combustion chamber, and the removed powder containing silica (SiO2) being collected in the circulating water tank through the connecting pipe and deposited on a bottom of the circulating water tank;
• the powder discharge system comprising:
• at least two eductors provided in the circulating water tank and disposed around the connecting pipe;
• each eductor comprising a nozzle configured to throttle a flow of water supplied from a pump 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 configured to eject the water sucked from the suction port together with the water discharged from the nozzle toward the bottom of the circulating water tank;
• wherein the discharge port of each eductor is positioned at the same vertical position as a position of a lower end of the connecting pipe;
• each eductor is disposed radially outward of the connecting pipe and equally distanced from a center of the connecting pipe at a distance between D1 and 2D1 wherein an inner diameter of the connecting pipe is D1 and a spray angle of each eductor is set in a range of 30° to 70°;
• a drainage port provided at an upper part of the circulating water tank and configured to discharge water in the circulating water tank to the outside of the exhaust gas treatment apparatus;
• and
• a water level sensor configured to control a water level of the circulating water tank to form a state where the water level is lower than the suction port of each of the at least two eductors and a state where the water level is higher than the suction port of each of the at least two eductors;
• when the water level is lower than the suction port of each of the at least two eductors, only the water discharged from the nozzle is ejected from each of the at least two eductors toward the bottom of the circulating water tank;
• and
• when the water level is higher than the suction port of each of the at least two eductors, the water discharged from the nozzle and the water sucked from the suction port are ejected from each of the at least two eductors toward the bottom of the circulating water tank;
• wherein the water ejected from the discharge port of each of the at least two eductors crushes the powder containing silica (SiO2) deposited on the bottom of the circulating water tank and floats the powder containing silica (SiO2), and the powder containing silica (SiO2) is discharged through the drainage port from the circulating water tank together with drainage water.