1. Silicon Deposition in NHT

2. Silicon n Origin n Deposition in catalyst n Deposition in reactors n Catalyst performance n Silicon questionnaire

3. Origin n ‘Indigenous’ to crude u most likely not really indigenous to crude u ‘well head chemicals/pipeline drag reducers’, decompose in CD furnace ? l Convent (Arab medium, Arab Heavy) l Wood River (Misc crudes) l Al Jubail (Arab light) l Norco n Added in refinery as antifoam u DCU u BEU (80’s DP) u VPS pre flash vessel (Convent)

4. DCU antifoam : Decomposition Polydimethyl siloxanes N= ~1000 Si content : 41 % Spirosiloxane Cyclo-methylsiloxane Thermal decomposition in naphtha boiling range typically 2-7 Si atoms Hexamethyldisiloxane BP 214 °F Octamethylcyclotetrasiloxane BP 347 °F

5. DCU antifoam : Decomposition l Martinez data u Naphtha : 48 % u LGO: 21 % u HGO: 30 %

6. DCU antifoam : Decomposition

8. Si analytical capabilities l Methods used n Inductive coupled plasma/optical emission spectroscopy u vaporization of Si n Neutron activation analysis u High detection limit (1 ppmwt) n Atomic absorption spectroscopy n Direct current plasma l WTC n DIN/ICP u direct injection nebulizer torch u typically 0.1 ppmwt

9. Si on catalyst: chemical structure l SiO 2 bonds with Al 2 O 3 l Low temp: adsorbed as silicon oil

10. Si on catalyst: surface area l Development of high Si capacity catalyst u high surface area u low metal loading

11. Si on catalyst: temperature l Norco NHT guard reactors n temperature ~ 400 °F u C424 Si 2.0 wt% (‘89) u TK551 Si 1.9 wt% (‘91) l MTZ HGHT n temperature ~ 400 °F u DN190 Si 0.6 wt% (‘96) u TK555 Si 0.6 wt% (‘96) u TK525 Si 0.8 wt% (‘96) l Successful practice n once Si breakthrough is measured raise the temperature and Si breakthrough stops for few weeks, allowing preparation for S/D. l Norco NHT main reactor n temperature ~ 600 °F u C424 Si 2.9 wt% (‘89) u C424/311 Si 4.7 wt% (‘91) l MTZ HGHT n temperature ~ 570 °F u DN190 Si 1.0 wt% (‘96) u TK555 Si 1.1 wt% (‘96) u TK525 Si 0.7 wt% (96’)

12. Si on catalyst: particle size l Criterion data, DN140, 1/10” Si load 6.8 wt%Si load ~ 3 wt%

13. Si on catalyst: particle size l Haldor Topsoe data TK431 TK524, TK525

14. Si in catalyst: pore size l Effect of pore size: l Diffusional resistances, for small pore sizes n data from various early ‘90 catalyst u KF84480 A u TK43159 A u DN14079 A

15. Si deposition in reactors n Top saturated n Middle part, transfer zone n Bottom part ‘non’ used SOR Mass transfer zone Unused zone EOR Saturated zone Mass transfer zone Saturated zone

16. Si deposition in reactors l Plant data ex Norco NHT

17. Si deposition MTZ I l Similarity with adsorption on zeolites u H 2 O, H 2 S on 3A, 4A zeolites u C: constant, to be defined basis plant data u V: vapor velocity (feed + recycle gas) u r p : particle diameter u D Si comp : Diffusivity of Si component inside cat particle

18. Si deposition MTZ II l Extrapolate Norco data to pilot plant n Norco2.5 mm, 550 SCF/bbl, SV 4.1 n Pilot plant1.3 mm, 1140 SCF/bbl, SV 9 n extrapolation about 50% of catalyst volume is MTZ in pilot plant test

19. Si deposition MTZ: conclusion l Small catalyst particle l Low velocities

20. Si on catalyst: activity l Haldor Topsoe data n small effect on HDS n strong effect on HDN l Naphtha n mainly HDS, SI breakthrough l LGO (in diesel) n small effect on HDS l HGO n small effect on HDS (CFH) n large effect on HDN (HCU)

21. Maximum Si loading ‘91

22. Maximum Si loading ‘99 (*) older data

23. Maximum Si loading: conclusion n Net wt% Si on catalyst data available n CBD is crucial u DN140Lab 42 (CBD), DP 44.5 (dense), Densicat 48.3 difference between 2.5 and 1.3 (4 lb/ft) u TK431PS 48 (dense) u KF844 Lab 43 (CBD), ED 41 (sock), 49 (dense)

25. Silica questionnaire l Aim to analyze injection of antifoam u quantity u quality l Aim to see how it was handled in downstream unit u monitoring u capacity l Preview

26. Silica injection