Abstract:

Effect of internals on the pressure drop, axial and radial solids concentration distribution and radial non-uniformity index inside a novel riser reactor with a diameter-enlarged bottom was emphatically studied in a cold model apparatus, and the flow structures inside the diameter-enlarged sections with different internals were proposed. The results show that the pressure drop of the diameter-enlarged section with a bluff-body is larger than that of the one with an annular pipe under the same operating condition, which diminishes the impetus of circulation. The solids concentration is affected by the internals apparently. The jet effect caused by annular pipe feeding lowers the solids concentration as well as worsens the radial uniformity while the bluff-body could overcome the drawbacks of annular pipe, weakening the jet action and increasing the solids holdup. Besides, gas and solids are redistributed by the bluff-body, forming a cross-flow which intensifies the gas-solids contacting, and a vortex, which promotes the turbulence inside the diameter-enlarged section. The radial non-uniformity index of solids concentration in the diameter-enlarged section with the bluff-body is much smaller, resulting in a more uniform solids distribution, and a small variation of the index as the operating conditions change, which exhibits higher operation stability.

Key words: annular pipe, bluff-body, variable diameter riser, pressure drop, solids concentration, radial non-uniformity index