Silicon Deposition in NHT

Silicon

Origin

Deposition in catalyst

Deposition in reactors

Catalyst performance

Silicon questionnaire

Origin

‘Indigenous’ to crude most likely not really indigenous to crude ‘well head chemicals/pipeline drag reducers’, decompose in CD

furnace ? Convent (Arab medium, Arab Heavy) Wood River (Misc crudes) Al Jubail (Arab light) Norco

Added in refinery as antifoam DCU BEU (80’s DP) VPS pre flash vessel (Convent)

DCU antifoam : Decomposition

Si OHOSiOSiHO

CH3

CH3

CH3

CH3

CH3

CH3

N

Polydimethyl siloxanesN= ~1000Si content : 41 %

SiO

O

O

O

Si

SiO

CH3

CH3CH3

CH3Si

SiO

CH3

CH3

CH3

CH3

O

SiCH3

O

CH3

O

Si SiCH3

CH3CH3CH3

Spirosiloxane

Cyclo-methylsiloxane

Thermal decompositionin naphtha boiling rangetypically 2-7 Si atomsSi O Si

CH3

CH3

CH3H3C

CH3

CH3

HexamethyldisiloxaneBP 214 °F Si

O O

Si

O

Si

Si

O

CH3

H3C

CH3

CH3CH3

CH3

CH3

CH3

OctamethylcyclotetrasiloxaneBP 347 °F

DCU antifoam : Decomposition

Martinez data Naphtha : 48 % LGO : 21 % HGO : 30 %

DCU antifoam : Decomposition

Cut # Boiling range ºF

wt %Son total basis

ppmwt Non total basis

ppmwt Sion total basis

1 88-176 0.02 3.1 0.9

2 176-200 0.04 2.9 0.3

3 200-225 0.15 11.1 0.6

4 225-249 0.15 16.7 4.4

5 249-275 0.23 25.0 6.5

6 275-300 0.15 27.2 1.1

7 300-324 0.2 28.1 1.1

8+9 324-350 0.11 41.8 2.0

residue 350+ 0.09 64.4 2.3

DCU antifoam : Decomposition

Si as function of time

0123456789

10

0 2 4 6 8 10 12 14 16

Time in hours

Si in

ppm

wt i

n D

CU

N

apht

ha

00.050.10.150.20.250.30.350.40.450.5

AF

inje

ctio

n in

GPH

Si in Coker NapAF Injection

Si analytical capabilities

Methods used Inductive coupled plasma/optical emission spectroscopy

vaporization of Si Neutron activation analysis

High detection limit (1 ppmwt) Atomic absorption spectroscopy Direct current plasma

WTC DIN/ICP

direct injection nebulizer torch typically 0.1 ppmwt

Si on catalyst: chemical structure

SiO2 bonds with Al2O3

Low temp: adsorbed as silicon oil

O

Si

CH3

OH OH Si

O O

HO CH3Si O Si

CH3

O

CH3H3C

CH3

O

Si on catalyst: surface area

Development of high Si capacity catalyst high surface area low metal loading

Si uptake versus SA

02468

101214

100 150 200 250 300 350

Surface area (in m2/g)

Si u

ptak

e in

wt%

Si on catalyst: temperature

Norco NHT guard reactors temperature ~ 400 °F

C424 Si 2.0 wt% (‘89) TK551 Si 1.9 wt% (‘91)

MTZ HGHT temperature ~ 400 °F

DN190 Si 0.6 wt% (‘96) TK555 Si 0.6 wt% (‘96) TK525 Si 0.8 wt% (‘96)

Successful practice once Si breakthrough is measured raise the temperature

and Si breakthrough stops for few weeks, allowing preparation for S/D.

Norco NHT main reactor temperature ~ 600 °F

C424 Si 2.9 wt% (‘89) C424/311 Si 4.7 wt% (‘91)

MTZ HGHT temperature ~ 570 °F

DN190 Si 1.0 wt% (‘96) TK555 Si 1.1 wt% (‘96) TK525 Si 0.7 wt% (96’)

Si on catalyst: particle size

Criterion data, DN140, 1/10”

Si load 6.8 wt% Si load ~ 3 wt%

Si on catalyst: particle size

Haldor Topsoe data

TK431

TK524, TK525

Si in catalyst: pore size

Effect of pore size:

Diffusional resistances, for small pore sizes data from various early ‘90 catalyst

KF844 80 A TK431 59 A DN140 79 A

gmareasurface

gccvolumepore

areasurface

volumepored p

/

/

*4

2

Si deposition in reactors

Top saturated Middle part, transfer zone Bottom part ‘non’ used

SOR

Mass transfer zone

Unused zone

EOR

Saturated zone

Mass transfer zone

Saturated zone

Si deposition in reactors

Si uptake in catalyst bed

0

2

4

6

8

10

12

0 5 10 15 20 25

depth in bed, in ft

wt%

Si upta

ke

.

Plant data ex Norco NHT

Si deposition MTZ I

Similarity with adsorption on zeolites H2O, H2S on 3A, 4A zeolites

C : constant, to be defined basis plant data

V : vapor velocity (feed + recycle gas) rp : particle diameter

DSi comp : Diffusivity of Si component inside cat particle

compSi

pmtz

D

rVCH

*15**~

2

Si deposition MTZ II

Extrapolate Norco data to pilot plant Norco 2.5 mm, 550 SCF/bbl, SV 4.1 Pilot plant 1.3 mm, 1140 SCF/bbl, SV 9 extrapolation about 50% of catalyst volume is MTZ in pilot

plant test

0

1

2

3

4

5

6

7

wt%

Si

upta

ke

1 2 3 4 5 6 7 8

depth in bed

Si uptake in catalyst bed

Si deposition MTZ: conclusion

Small catalyst particle Low velocities

Si on catalyst: activity

Effect Si deposition on activity

0102030405060708090

100

0 2 4 6 8 10 12

Si load in wt%

Rel

ativ

e ac

tivity

in %

HDSHDN

Haldor Topsoe data small effect on HDS strong effect on HDN

Naphtha mainly HDS, SI

breakthrough LGO (in diesel)

small effect on HDS HGO

small effect on HDS (CFH) large effect on HDN (HCU)

Maximum Si loading ‘91

Catalyst Net Si load inwt%

CBD Si in lb/ft3

9.6 43 4.1

7.6 42 3.2

7.9 47 3.7

5.1 52 2.6

9.0 54 1.8

7.1 41 3.7

5.1 40 2.8

9.8 39 2.6

Maximum Si loading ‘99

Catalyst Net Si load inwt%

CBD Si in lb/ft3

9.1 36 3.3

8.3 36 3.0

9.0 43 4.2

9.6 43 4.4

7.0 45 3.2

7.3 45 3.3

9.5 42 4.0

10.5 42 4.4

9.8 48 4.7

(*) older data

Maximum Si loading: conclusion

Net wt% Si on catalyst data available CBD is crucial

DN140 Lab 42 (CBD), DP 44.5 (dense), Densicat 48.3 difference between 2.5 and 1.3 (4 lb/ft)

TK431 PS 48 (dense) KF844 Lab 43 (CBD), ED 41 (sock), 49 (dense)

Silica questionnaire

Aim to analyze injection of antifoam quantity quality

Aim to see how it was handled in downstream unit monitoring capacity

Preview

Silica injection

5/24/99 30

Silica injection

Location Feed ratembbl/sd

Ant ifoaminjectionLb Si/day

AF/feedLb Si/ mbbl

throughput/drum areabbl/sd/ft2

Outage atstart injection,

in ft

Visco, incSt

DP 61 54 0.88 50 55 10000

ED 18 12 0.67 57 20 60000

Norco 26 18 0.69 68 30 60000

PAP 54 29 0.54 47 60000

BfP 22 45 2.05 53 60000

LA 56 26 0.46 29 60000

MTZ 27 2 0.07 51 25 60000

PS 25 33 1.32 47 30 60000