Gas-Liquid Reactions - Influence of liquid bulk and mass transfer on process performance

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    The dynamic behaviour and stability of single phase reacting systems has been investigated thoroughly in the past and design rules for stable operation are available from literature. The dynamic behaviour of gas-liquid processes is considerably more complex and has received relatively little attention. General design rules for stable operation are not available.

    Dynamic model
    Schematic presentation of the rigorous reactor model.

    A rigorous gas-liquid reactor model has been developed (van Elk et al., Chemical Engineering Journal, 2000) and used to demonstrate the possible existence of dynamic instability (limit cycles) in gas-liquid processes in all regimes of mass transfer (van Elk et al., Chemical Engineering Science, 1999). The model is also used to demonstrate that the design rules of Vleeschhouwer et al. (1992) are restricted to a specific limit case.

    4 types of dynamics
    4 types of dynamics (asymptotic damping, spiral point, limit cycle and transition).

    A new approximate model is presented that after implementation in bifurcation software packages can be used to obtain general applicable design rules for stable operation of ideally stirred gas-liquid reactors.

    Stability map
    Stability map of a reactor design (operation in the yellow area is unfeasible (static unstable) and operation in the red area is usually undesired (dynamic unstable)).

    The rigorous reactor model and the approximate design rules cover the whole range from kinetics controlled to mass transfer controlled systems and are powerful tools for designing gas-liquid reactors.

    Interesting phenomena can take place in reactors with complex kinetics (negative reaction order). For an industrial size hydroformylation reactor limit cycles were found, which can vanish by reducing the mass transfer contact area, without changing the conversion (van Elk et al., Chemical Engineering Science, 2000).