One exemplary embodiment can be an apparatus for isomerizing a hydrocarbon stream rich in a C4 hydrocarbon and/or at least one of a C5 and C6 hydrocarbon. The apparatus can include: a first drier and a second drier adapted to receive a fluid including at least one reactant; and a reaction zone communicating with the first drier to receive the fluid including at least one reactant and with the second drier to receive the regenerant. Generally, the first drier operates at a first condition to dry the fluid including at least one reactant and the second drier operates at a second condition during regeneration with a regenerant. The regenerant can pass through a fluid tapering device for regulating the flow of the regenerant to the reaction zone.