Patent ID: 7122160

Claim:
A hydrocarbon conversion apparatus, comprising: a plurality of riser reactors, each of the riser reactors having a first end into which a catalyst can be fed and a second end through which the catalyst can exit the riser reactor; a catalyst retention zone provided to contain catalyst and from which catalyst can be fed to the riser reactors; a separation zone provided to separate the catalyst from products of a reaction conducted in the hydrocarbon conversion apparatus; a transport conduit having a first end in fluid communication with the second ends of at least two of the riser reactors and a second end extending into the separation zone; and a catalyst return in fluid communication with the separation zone and the catalyst retention zone; wherein the smallest cross-sectional area of the conduit is at least equal to the sum of the smallest cross-sectional areas of the riser reactors in fluid communication therewith, and the smallest cross-sectional area of any one of the riser reactors varies by no more than about 20 percent from the smallest cross-sectional area of any other of the riser reactors.