Moving bed reactor (MBR) is a reactor where the spent catalysts are removed and fresh catalysts are added periodically. These types of reactors can be used to process petroleum feeds with higher level of contaminants including heavier feeds, to increase catalyst cycle and life of the downstream hydrotreating units by better protection from fouling metals of the feedstock and to improve in general the product quality. In this reactors gas and liquid phases flow upward. In order to increase the throughput of the reactor, high flow rates and high gas/liquid ratio have been used which put the reactor under incomplete fluidization. Thus gas phase behavior is important to reactor performances.

In this work, we investigated gas phase mixing and dispersion in a cold flow MBR reactor with 11 inch (0.2794 m) in inner diameter using gas tracer technique. In this multi-phase system, water as liquid phase with superficial liquid velocity 0.018 cm/s and air as gas phase with superficial gas velocity range 1.27 cm/s~7.64 cm/s entered the bottom together then flowed upwardly through the packing bed with catalysts of 3mm in diameter. Helium as gas tracer was injected into bottom and two sampling were detected at bottom and top of the packing bed, respectively. Residence time distribution and axial dispersion coefficient of gas phase under different operating conditions were obtained. In this research, the results show residence time decrease and axial dispersion degree increase with increasing gas flow rate.

Key words

Multiphase flow, Moving bed reactor, Gas tracer technique, Residence time distribution, axial dispersion coefficient