Mixing of secondary gas injection in a bubbling fluidized bed

In this work, three-dimensional numerical simulations with the aim of investigating the mixing of secondary gas in a bubbling fluidized bed are performed. Single and multiple horizontal gas jet injections into a small scale rectangular bubbling fluidized bed are studied. A tracer gas is introduced through the jet orifice to study the gas mixing in the system. Both transient and time-averaged results are analyzed. The effect of gas injection velocity and jet arrangement on the gas-solid contact is evaluated. It is found that the tracer distribution is non-uniform at the injection level. Within a short distance above the injection, the tracer becomes uniformly distributed. Gas back-mixing is observed in all simulations, which is prominent near the wall due to the downward flow of solids. For the cases studied, the gas back-mixing tends to decrease as the secondary gas flow rate increases. For the same secondary gas flow rate, it has been demonstrated that a better mixing between the tracer gas and solid particles is achieved when the secondary gas is injected through distributed jet arrangement.