| 摘要 |
PROBLEM TO BE SOLVED: To improve the separation efficiency of CF4 and C2 F6 by bringing a gas mixture containing CF4 , C2 F6 or the like into contact with a membrane under conditions effective to obtain a residual flow rich in SF6 , CF4 or the like to make SF6 adsorbed and to obtain a permeated flow rich in NF3 , CHF3 or the like and then bringing the residual flow into contact with an adsorbent. SOLUTION: When a gas mixture containing CF4 , C2 F6 , NF3 , CHF3 , N2 and SF6 such as a waste gas or a vent gas from a semiconductor production process is treated, first, the gas mixture 1 is brought into contact with a membrane separation unit 10 under conditions effective to obtain a residual flow 2 rich in at least one kind of SF6 , CF4 and C2 F6 and to obtain a permeated flow 3 rich in at least one kind of NF3 , CHF3 and N2 . Then, the residual flow 2 is brought into contact with an adsorbent such as zeolite and activated carbon in an adsorption unit 20 under the conditions effective to adsorb SF6 and to produce a flow rich in at least one kind of CF4 and C2 F6 . Thus, CF4 and C2 F6 are separated from a PFC (perfluorocarbon) mixture. |
