"ially in section of a four-stage countercurrent stripper which can be directly connected with the exhaust barrel of the cyclone separator illustrated in FIGS. 2a and 2b; FIG. 6 is a side view partially in section of one embodiment of a catalyst seal pot in accordance with the present invention; FIG. 7 is a side view partially in section of a further embodiment of a catalyst seal pot in accordance" . . . .