Reduced fluidization of solid particles in radial flow fluid/solid contacting

A process for converting a fluid hydrocarbon feed at least partially in the gas phase, the process comprising:

• (a) passing a major portion of the hydrocarbon feed substantially radially through solid particles of hydrocarbon conversion catalyst retained in an annular catalyst bed between concentric, cylindrical upstream and downstream screens;
• (b) passing a minor sealing portion of the hydrocarbon feed axially downward from the top of a sealing portion of the catalyst and through the annular catalyst bed;
• (c) withdrawing a hydrocarbon product resulting from contact between the major portion and sealing portion of the hydrocarbon feed with the hydrocarbon conversion catalyst;
• (d) adding regenerated hydrocarbon conversion catalyst to the sealing portion of the catalyst;
• and
• (e) withdrawing spent hydrocarbon conversion catalyst from the bottom of the annular catalyst bed;
• wherein the upstream screen has openings above highest downstream openings of the downstream screen, wherein a base of a sealing portion of the solid particles is defined by a downwardly sloping line segment from highest upstream openings to the highest downstream openings,
• wherein a ratio of a) a vertical distance from highest upstream screen openings to a top of the sealing portion to b) a horizontal spacing distance between the upstream screen and the downstream screen is less than about 0.8, and
• wherein a pressure drop of the fluid across each of the upstream and downstream screens is less than about 10% of a pressure drop across the bed of the solid particles.