Patent ID: 6919048

Claim:
A reaction vessel that is elongated substantially along a substantially vertical axis, comprising at least two stages in the vertical direction, in which at least one endothermic or exothermic catalytic reaction is carried out, comprising: at least one catalytic reaction zone ( 12 a , 12 b ) per stage ( 6 , 7 ) and extending substantially along the axis of the vessel; means ( 2 ) for introducing at least one reaction fluid to a stage adapted for substantially transverse fluid movement over substantially the whole vertical extent of the reaction zone; means for introducing catalyst into the at least one reaction zone and means for extracting catalyst from the at least one reaction zone; at least one means ( 5 a ) for heat exchange with reaction fluids, located inside the vessel between two successive reaction zones; means ( 6 ) for transporting reaction fluids from one stage to a subsequent stage connected firstly to a heat exchange means of the one stage and secondly to the reaction zone of the subsequent stage; and means for recovering reaction fluids downstream of the last stage; wherein the thickness of each reaction zone being determined to limit the variation in temperature in said zone and the heat exchange means being adapted to adjust the temperature of the reaction fluids entering the reaction zone to a level substantially at most equal to that of the temperature of the reaction fluids entering the preceding zone, and in which the catalyst is in the form of a moving bed, with substantially gravitational flow, the at least one reaction zone of one stage being connected to that/those of a lower stage via at least one passage with cross section (S 1 ) that is reduced with respect to the cross section (S 2 ) of the at least one reaction zone, the at least one reaction zone of the first stage comprising means for introducing catalyst and the at least one reaction zone of the final stage comprising catalyst extraction means, said extraction means comprising a means for adjusting and controlling the rate of catalyst flow.