Pressure drop and liquid holdup in high pressure trickle-bed reactors

The vast majority of commercial trickle-bed reactors, fixed bed of catalyst particles contacted by cocurrent downflow of gas and liquid, operate at high pressure. In this study Holub et al.,s (1992, 1993) phenomenological model has been extended to describe the effect of high pressure (i.e. increased gas density) on pressure drop and liquid holdup in the trickle flow regime. This model, based on annular two-phase flow in a slit, ties pressure drop and liquid holdup but was previously verified only at atmospheric pressure. The advantage of this model is that the Ergun constants E-1 and E-2, required by the model, are determined from single phase (gas) flow through the packing of interest and no two-phase flow data is needed. Experiments were conducted at high pressure over a range of gas and liquid velocities and different bed characteristics. The developed phenomenological analysis, describing the effect of high pressure and gas flow rate in terms of five limiting cases, matches well the experimental observations. The high pressure data collected in this study was used as a basis for comparing the prediction for pressure drop and liquid holdup of the model and of the available high pressure correlations. Holub er al.'s (1992) model matches experimental observations better than available correlations. It also predicts all trends in pressure drop and holdup correctly for all changes in operating variables such as pressure, liquid and gas superficial mass velocity and with physical properties of the gas and liquid.