Regeneration - Spent Hydroprocessing Catalysts - page 187

(2 to 2.5m). The louvres supports are continuous radial partitions that form longitudinal
passages extending the entire length of the drum. The catalyst to be regenerated is contained
on the louvres and moves toward the discharge end by rotation of the drum. Hot air produced
in an external, independent combustion chamber passes through the spaces between the
louvres and permeates a thin layer of catalyst bed. A composition and high velocity of gases
combined with the rotation ensuring the movement of catalyst prevent the development of hot
spots. In addition, the countercurrent of the catalyst and oxidation medium are favourable for a
steady monitoring the temperature. Other important operating parameters include depth of
catalyst bed, feed rate of catalyst residence time. All these parameters can be varied to contain
temperature with acceptable limits. Under these conditions, a high recovery of catalyst activity
is ensured. Similarly as for the CRI (belt) process, all units required for the control of gaseous
and solid emissions are also integrated with the EUROCAT process.
6.4.4.4 REACT Process
This process was developed by Albemarle Catalysts for activity recovery of their STARS
portfolio catalysts with type II active sites. Some features of this process were discussed above
in the section on reactivation of spent hydroprocessing catalysts [430-432] . An Albemarble
catalyst used for hydroprocessing VGO was regenerated using conventional oxidative
regeneration method as well as reactivated using the REACT process [474] . In the former case,
the HDN activity of 60 to 70% was achieved compared with 92 to 97% using the STAR
process and/or about 10 and 2 ◦ C activity loss for conventional regeneration and that followed
by REACT process, respectively.
6.4.4.5 ReFRESH Process
This process was developed and commercialized by Haldor Topsoe [433] . The details of this
process are not available although the simplified schematic in Fig. 6.45 indicates that it may
involve an oxidative regeneration in the first step followed by a reactivation presumably
involving chelating agents. In the first step, the activity recovery reached 80-85 % of the fresh
catalyst activity. The further enhancement in activity to more that 95% achieved in the second
stage suggests that the refiner can use the same catalyst at least in two cycles.
6.4.4.6 Rotary Kilns
Rotary kilns have been used in various industrial applications (e.g., oil shale retorting, tar
sands coking, incineration, cement production, etc.). The rotation of a cylinder-shaped vessel
positioned longitudinally approximately 30 ◦ of the horizontal position ensures a continuous
motion of catalyst between the entrance and exit of the kiln. With regard to the spent catalyst
regeneration, the description of rotary kilns was given by Ellingham and Garrett [451] . There
are two types of rotary kilns, i.e., direct fire and indirect fire.