Staging Effect By a Baffle in a Deep Fluidized Bed

A commercial deep fluidized bed such as a fluid coking reactor is dominated by the large scale internal recirculation patterns that are much faster than the external solids circulation rate. When hot solids are introduced to the reactor, the solids are well mixed throughout and maintain a rather uniform temperature profile in the fluidized bed reactor. As a result, there is a need to separate the reactor into two stages/zones operating at different temperatures to increase its flexibility, e.g., running the top stage at lower temperature for higher liquid yield.   A CFD simulation was applied to demonstrate the feasibility to separate the fluidized bed reactor into two distinct mixing zones. It indicated that without an annular baffle present, the solids were distributed uniformly in the reactor and no staging occurred; with an annular baffle, the solids injected below the baffle remained confined within the zone below the baffle. A cold flow testing in a 3ft ID unit was also used to demonstrate this behavior. Solids tracer testing was conducted to test the solids distribution with and without the annular baffle. The cold flow testing results were consistent with the CFD simulation.   This paper describes how cold flow testing and advanced modeling are used to develop technology solutions for commercial application.