METHOD AND DEVICE OF REMOVING NITROGEN TRIFLUORIDE

PROBLEM TO BE SOLVED: To prevent nitrogen trifluoride (NF3 ) and reductive gas from forming an explosive mixture when the concentration of NF3 in waste gas exceeds the target concentration by additionally feeding inert gas to waste gas to make the NF3 concentration not more than the target concentration. SOLUTION: After NF3 containing waste gas effluent from a NF3 effluence device 1 is mixed with diluting gaseous nitrogen fed from a diluting inert gas feeding port 2, in a NF3 removing device 20, first, the NF3 concentration and the NF3 containing waste gas flow rate are measured by a NF3 concentration meter 6 and a flow meter 7 respectively, and in an arithmetic unit 13, when the measured NF3 concentration is not more than the target value, the preset value of a flow controller 15 is made zero, and on the other hand, when it exceeds the target value, from the difference between the measured concentration and the target value and the flow rate of the NF3 containing waste gas, the quantity of nitrogen to be fed is calculated to output the preset value to the flow controller 15, and the gas is mixed with the added nitrogen and reductive gas to remove the NF3 in a NF3 reduction reactor 9.