Gulf Coast heavy vacuum gasoil hydrotreater
Actual WABT HDS normalised WABT
Feed/operating conditions
Units
Typical values
Space velocity
h-1
1
Density Sulphur Nitrogen
SG/°API
0.94/19
wt%
3-3.3
Wt ppm bar/psia
2,500-3,100 130 /1,900
Hydrogen partial pressure
Deactivation <<1˚F/month (0.55 ˚C/month)
Cracked feedstock Feed IBP, SimDist Feed FBP, SimDist
%
100
°C/°F °C/°F
232/450
571/1,060
Diesel product sulphur TLP product sulphur TLP product nitrogen
wt ppm wt ppm wt ppm
<20
0
50
100
150
200
250
300
350
400
Run day
<125
<50
heavy long-chain molecules that contain highly complex sulphur and nitrogen species, polycyclic aromatic struc- tures, and a high degree of metals usually present in heavier fractions. The complexity of the gasoil feed can necessitate a high-capacity guard catalyst that can result in a lower vol- ume of active catalyst available for HDS and HDN reactions. In addition, to achieve extremely low product sulphur and nitrogen specifications in conjunction with elevated polyar - omatic saturation, characteristics of both NiMo and CoMo catalyst are needed to maintain product specifications and unit stability. With the development of the trimetallic TK-594 HyBRIM catalyst, industrial units have been able to achieve this balance of unit stability with deep desulphuri- sation and optimal product yields. Case study: real results The TK-594 HyBRIM has been installed in a high-pressure Gulf Coast heavy vacuum gas oil (HVGO) unit. The primary unit process objective is to achieve ULSD product speci - fications, and the secondary process objective is to max - Figure 6 Commercial deactivation rate of TK-594 HyBRIM – Gulf Coast heavy vacuum gasoil hydrotreater
Table 2
deactivation rate is shown as a function of the logarithmic sulphur vs run hours. The results indicate that TK-594 HyBRIM shows similar stability to a stacked NiMo/CoMo catalyst system, which typically shows similar stability to a pure CoMo catalyst system in industrial units. It is also clear that the pure NiMo catalyst system deactivates faster than the other two CoMo-containing catalyst systems. The pilot test deactivation rate cannot be translated directly into an industrial deactivation rate due to the large difference in lineal hydrogen velocity, which accelerates the deactivation in the pilot test. However, it can serve to directionally gauge the impact and stability risk of utilising a pure NiMo catalyst load. Optimising heavy gasoil hydrotreating unit performance In industrial hydroprocessing units many challenges are present when compared to conventional naphtha and dis- tillate hydrotreaters. Gasoil feeds are comprised of very
imise hydrogen consumption to increase the volume swell. Typical operating con- ditions of the unit can be found in Table 2 . The bespoke catalyst in the Gulf Coast HVGO unit exhibited exceptional sta- bility in terms of the HDS deactivation rate from start-of-run (SOR) conditions. It maintained diesel yield and product sulphur stability throughout the cycle, as shown in Figure 6. The small difference between the actual and kinetically nor- malised weight average bed temperature (WABT) is an indication that the unit was running close to the reference condition with a small variation of the feed and operating parameters. The diesel sulphur and American Petroleum Institute (API) gravity shifts vs true conversion (690°F+, wt%) are shown in Figure 7 . The diesel sulphur shows a lineal response to the true conversion, while the API uplift (high volume swell) in the total liquid product significantly
140
Diesel sulphur (wt ppm) C + API shift
12.00
120
10.00
100
8.00
80
6.00
60
4.00
40
2.00
20
0
0.00
10.0
15.0
20.0
25.0
30.0
35.0
40.0
True conversion 690˚F (wt%)
Figure 7 Diesel sulphur and API shift of TK-594 HyBRIM – Gulf Coast heavy vacuum gasoil hydrotreater
54
PTQ Q4 2024
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