Environmental Engineering Reference
In-Depth Information
Table 7.8: Properties of spent catalyst particles from ebullated bed reactor [From ref.
12
. Reprinted
with permission].
Property
Spent mix
Lightly fouled
Heavily fouled
Vanadium (wt.%)
10
.
6
4
.
4
13
.
8
Nickel (wt.%)
4
.
0
3
.
5
5
.
2
Carbon (wt.%)
16
.
2
15
.
8
16
.
3
Surface area (m
2
/g)
68
122
55
Bulk density (kg/L)
1
.
09
0
.
97
1
.
21
Side crushing strength (lb/mm)
1
.
8
2
.
1
1
.
2
Pore volume (mL/g)
0
.
17
0
.
21
0
.
11
Particle length distribution (wt.%)
<
1.5 mm
25
.
2
14
.
4
40
.
0
1.5-3.0
42
.
3
23
.
5
37
.
0
3.0-6.0
32
.
5
61
.
3
23
.
0
>
6.0
0
0
.
8
0
shows the properties of spent mix obtained from ebullated bed reactor as well those of lightly
fouled and heavily fouled portions obtained from the spent mix by jigging technique using a
mineral jigg. Lightly fouled particles accounted for about 30 wt.% of the mix. According to the
classification discussed earlier, lightly fouled particles could be still regenerated; however, the
other particle fractions would almost certainly require rejuvenation step before decoking.
Particle size distribution in
Table 7.8
is of particular interest. Thus, for the fresh catalyst,
particle size was dominated by 3.0-6.0mm particles. For the heavily fouled particles, almost
70% of these particles were broken to less that 3.0mm length. This suggests that the size
separation of the heavily fouled particles would be desirable prior to their use in rejuvenation
process.
The rejuvenation strategy discussed in the introductory part of
Chapter 6
included three
options. Each of these options requires de-oiling of spent catalyst followed by particle size
and/or density separation.
Figure 7.17 [462]
shows how these two steps can be integrated into
a single process that could be applicable for each option. In this case, the dotted lines show the
gas flow, thin solid lines show the liquid routes, and thicker solid lines shown the solids
streams. Details of the gravity settling unit, termed also as a surface velocity classifier shown
in
Fig. 7.17
as unit “01V03” are given in
Fig. 6.36 [462]
. In this unit, separation depends on
the particle terminal velocity, which is a function of the physical and transport properties of the
solvents and catalyst particles. By adjusting the liquid flow from each compartment, the
catalyst particles with different densities are separated. After removing solvent in the drier,
particles are transferred to metals leaching process.
