grid floor is generally applicable to vessels which contain fluidized beds therefore the invention is applicable to any particular process where by passing of gases in a gap between a grid floor and a vessel wall is undesirable referring now to fig1 a catalyst regeneration vessel is illustrated generally at 10 the vessel 10 receives spent catalyst containing coke from an fccu reactor not illustrated via line 12 in the regenerator a catalyst bed 14 is formed and coke is burned from the catalyst with air supplied via line 16 the air is evenly distributed throughout the catalyst bed 14 by passing upwardly through perforations in the grid floor 18 the air supplied through line 16 fluidizes the catalyst bed 14 the perforated grid floor 18 is sealed against the generally cylindrical wall 20 of regenerator vessel 10 by a lower seal plate 22 and an upper seal plate 24 as will be more fully explained hereinafter the heat of combustion of the coke raises the catalyst temperature to 1 100 u00b0 to 1 250 u00b0 f the regeneration catalyst is then passed through line 26 for recirculation to the fccu reactor and the flue gas passes through line 28 to heat recovery apparatus not illustrated the portion of the interior of the regeneration vessel 10 to which the present invention is applicable is shown in greater detail in fig2 and 4 in a preferred embodiment of the invention as best seen in fig2 and 4 a portion of the support means and seal means at the perimeter of the grid floor 18 are illustrated the support means includes a flat grid support ring 30 welded along the outer circumferential edge thereof to the interior surface of vessel wall 20 a plurality of spaced apart.