Aulas HDS

7/21/2019 Aulas HDS

http://slidepdf.com/reader/full/aulas-hds 1/41

Hydroprocessing Units

November 2004

Pedro da Silva

7/21/2019 Aulas HDS


Why Hydroprocessing?

CO, NOx, HC,

Particulates

BEFORE

NOW

7/21/2019 Aulas HDS



Desulphurisation units become more and more

important in refineries

7/21/2019 Aulas HDS


Market of solid catalysts in refining, (IFP data,1994)

tons /yearCatalytic cracking 440 000

Hydroprocessing 80 000

Claus 20 000

Hydrocracking 8 000

Reforming 5 000

isomerization 1 000

other 12 000

TOTAL 566 000

More than 80% of refined molecules see at least

one catalyst in their liver !


7/21/2019 Aulas HDS


Hydroprocessing Units Layout

in a Refinery Scheme

A t m o s p h e r

i c D i s t i l l a t i o n

Heavy fuel

Crude

V

a c u u m D

i s t i l l a t i o n

CatalyticCracker

FCC

Visbreaking

Reforming

propanebutane

gasoline

naphtha

Hydrodesulphurisation

kerosene

diesel

H2

Amine wash

HDT

7/21/2019 Aulas HDS




A t m o s p h e r


Heavy fuel

Crude

V

a c u u m D


CatalyticCracker

FCC

Visbreaking

Reforming

propanebutane

gasoline

naphtha


kerosene

diesel

H2

Amine wash

HDT

HDS

7/21/2019 Aulas HDS




A t m o s p h e r


Heavy fuel

Crude

V

a c u u m D


CatalyticCracker

FCC

Visbreaking

Reforming

propanebutane

gasoline

naphtha


kerosene

diesel

H2

Amine wash

HDT

HDS

7/21/2019 Aulas HDS


Typical operating conditions of

Hydrodesulphurisation Units

PROCESS Pressure

(bar)

Temperature

(°C)

Flowrate/

catalyst volume

(h-1) Naptha 7-30 280-320 3-10

Kerosene 15-50 300-330 2-6

Diesel oil 15-90 320-390 1-4

VGO 30-100 340-410 1-2

ARDS 80-200 370-410 0.2-0.5VGO, residue

hydrocracker100-200 370-410 0.5-1.5

- The most important parameters followed in these units (apart from productqualities!) are the temperature and unit pressure drop

- The difference on activity and stability of different catalysts is measured by °C

7/21/2019 Aulas HDS


Chemical Reactions in

Hydroprocessing

Not limited by thermodynamics

Refractory compoundS

Hydrogen consumption

7/21/2019 Aulas HDS



Hydroprocessing

222120191817161514131211109876543210

48 000

46 000

44 000

42 000

40 000

38 00036 000

34 000

32 000

30 000

28 000

26 000

24 000

22 000

20 000

18 000

16 000

14 000

12 000

10 000

8 0006 000

4 000

2 000

0

-2 000

-4 000

-6 000

S P W 0 . 2

0

.

RT [min]

µV A21 41838-01_1.DATA

S

C1

S

C2

S

C4

S

C3

S

S

C1

S

C2

S

C3

S

C4+

S

C5

Soufre peu réfractaire Soufre très réfractaire

Soufreréfractaire

S

S

BT:Benzothiophène

DBT:Dibenzothiophène

7/21/2019 Aulas HDS


Soufre total=6 ppmS

S

S

S

S

S

S

4,6-EtMeDBT

1,4,6-TriMeDBT

2,4,6-TriMeDBT

4,6-DiMeDBT

4,6-DiEtDBT

3,4,6-TriMeDBT

4,6-PrMeDBT


Hydroprocessing

7/21/2019 Aulas HDS



Hydroprocessing

7/21/2019 Aulas HDS



Hydroprocessing

7/21/2019 Aulas HDS


Température (°C)

% H

D A

S o u f r e e f f l u e n t ( p p m )

T1 T2

HDS

Régime thermodynamique

(HDA)

Régime cinétique

(HDA)

Equilibre thermodynamiqueHDA


Hydroprocessing

7/21/2019 Aulas HDS



Hydroprocessing- Hydroprocessing reactions are exothermic- Temperature and pressure are needed for hydroprocessing reactions- Reactor delta temperature:

8-9°C rise per 1 wt% sulphur removal1-2°C rise per 1vol% of polyaromatics removal1°C rise per bromine number removal

quench

f o u r lit 1

lit 2

0

R1

Opération normale

R1

température

7/21/2019 Aulas HDS


Simplified Scheme of an

Hydrodesulphurisation Unit

2

Partial by-pass

Recycle

compressor

Raw feed

Make-up

compressor

Make-up

hydrogento fuel

gas

H.P.

Flash drumFurnace Reactor

Air

coolers

Heat

Exchangers

Stripper

Quench

7/21/2019 Aulas HDS


Hydroprocessing reactor andinternals

Vapor/liquid

distribution tray

Catalyst bed

Varies between 3 to 15 m

Catalyst supportgrid

Quenchdistributor

Mixing chamber

Outlet collector

Inlet diffuser

Unloading nozzle

Reactor diameter variesbetween 1,5 to 4,5 m

7/21/2019 Aulas HDS


Hydroprocessing Reactor andInternals

Catalyst bed

reactor outlet

collector

7/21/2019 Aulas HDS



Additional

gasketing

7/21/2019 Aulas HDS



What techniques can be used to check the gas-liquid distribution inside thereactor?

0

5

10

15

20

0 100 200 300 400 500 600

Days on stream

R a d i a l T d i s p e r s i o n ( ° C )

R1 B2 outlet

R2 B1 outlet

R2 B2 outlet

Radial temperature dispersionRadioactive tracers

Unit start-upUnit response to flow variations

7/21/2019 Aulas HDS


Hydroprocessing Catalysts

- Generally HDS catalysts are constituted by metal oxides from columnsVIA (Mo,W) and VIIIA ((Co),Ni) periodic table

- The active phase of HDS catalysts consists in the sulphided form of theseoxides – MoS2 slabs

Al2O3γ

Mo

Mo

S6Å

30Å

..

...

.

. .. . .

- Co or Ni are activity promoters and ‘decorate’ the edge of MoS2 slabs- CoMo catalysts are generally used for low pressure units and were the mainobjective are HDS reactions

- NiMo catalysts are generally used for higher pressure units and were the

main objective is density and cetane gain (hydrogenation reactions)

Co

7/21/2019 Aulas HDS


Hydroprocessing Catalysts

Used catalyst

Sulphide + coke

Regeneration of used catalyst is possible by carefully burning sulphur and

coke. The resulting catalyst will in its oxide form.

Fresh CoMo cataltyst 1.2-2.5 mm

Oxide state

7/21/2019 Aulas HDS


Hydroprocessing Catalyst’s Life

Were should I go on holidays?Why not a reactor of a

diesel hydrotreater?

Unloading under inert

atmosphere as I’mquite keen to react

with air

RotaryRotary KilnKiln

OvenOven

Spent CatalystSpent Catalyst

Hot Air Hot Air

Let’s do it again

Nice staying here, it’s always hot!

however, it’s also always raining

and it smells !!

catalyst

loading

7/21/2019 Aulas HDS


Catalyst Loading

7/21/2019 Aulas HDS


Catalyst loading

7/21/2019 Aulas HDS


Catalyst loading

L o c a l p o r o s i t y , ε

Catalyst bed grading must be adapted in order

to avoid pressure drop build-up

7/21/2019 Aulas HDS


Catalyst loading

Different particles are available to be loaded above the

main catalyst and minimize pressure drop build-up

good ‘hold’ inert balls or…

7/21/2019 Aulas HDS


Catalyst Activation

Oxide catalystMoO3

reactor

Reductionto MoO2

Unactive phase

Under H2T > 230-250°C

Oxide catalystMoO3

ex situ

‘preSulphided’

MoOxSy

ex situ

Active catalyst

MoS2

reactor

in situSulphidation

‘preSulphiding’Sulficat, Acticat,

EasyActive

H 2 Activation

Active catalyst

MoS2

ex situ

ex situ sulphiding Totsucat, XpresS

H2S

DMDS

Final step

7/21/2019 Aulas HDS


Catalyst Activation

R e a c

t o r i n l e t t e m p e r a t u r e ( ° C )

350

300

250

200

150

100

50

00 2 4 6 8 10 12 14 16 18 20

Time (hours)

Drying(120-150

°C)

Pre sulphiding step(reactor T < 15°C)

Catalyst sulphiding(320-350°C)

Catalyst wetting(liquid flow)

1.Catalyst wetting at lower temperature allows better gas-liquid distribution2.The drying step should always be below 150°C to avoid molybdenum oxide reduction

3.DMDS injection 1 hour before reaching presulphiding step

4.Maximum reactor exotherm should be below 15°C to avoid high catalyst temperaturesin without H

2

S

5.Catalyst sulphiding step temperature depends on catalyst type and unit operation

DMDS injection

Unit under pressure

7/21/2019 Aulas HDS


Kinetic Models

Feed + H2

Desulphurized product+ H2 + H2

[ ][ ]S k

dt

S d ×−=

LHSV

ek tck

Sout

Sin T R

Eact

×−

×=×=

0ln

××−=

0

)/ln(ln

k

LHSV Sout Sin R

E T

act

[ ][ ] [ ][ ] ∫∫∫∫ =⇔−= tcSin

Sout

tcSout

Sindt k

S

S d dt k

S

S d

00

7/21/2019 Aulas HDS


Kinetic Models

Typically, for HDS reactions on diesel and VGOEact = 25000 - 29000 cal/moleExample - Catalyst volume = 200 m3

Catalyst AFlowrate = 300 m3 /h

Bed 1 Tin = 345°C, Tout = 365°C, Bed 2 Tin = 360°C, T = 370°CWABT = 362,5°CSin = 7000 wtppmSout = 40 wtppmk0 = 1,5E10 h-1

Catalyst BFlowrate = 280 m3 /hBed 1 Tin = 342°C, Tout = 362°C, Bed 2 Tin = 352°C, T = 362°CSin = 7000 wtppmSout = 33 wtppm

WABT = 359,9°Ck0 = 1,4E10 h-1

Catalyst A is 2°C more active than catalyst B

(this value is higher with more precise models!)

7/21/2019 Aulas HDS


Kinetic Models - Cycle Length

Other parameters that must be taken into account in the kinetic models are:- hydrogen partial pressure

- feed severity (nitrogen, density, aromatics, T95, other)

- hydrogen/oil ratio, hydrogen sulphide and ammoniac partial pressure

Time

SOR EOR

Feed rate

Max temp

Cycle length

R e g en er a t i on or c a t al y s t c h a

n g e o u t

Temperature

7/21/2019 Aulas HDS



Time

Feed rate

Max temp

C cle len th

Temperature

Time

Feed rate

Max temp

C cle len th

Poor catalyst performance High pressure drop

7/21/2019 Aulas HDS



- Average Reactor Temperature = 1/3 inlet T + 2/3 outlet T- Temperature increase with time due to coke formation and poisons adsorption

- 3,5°C/month deactivation

320

330

340

350

360

370

380

390

400

0 40 80 120 160 200 240 280 320 360Days on stream

R e a c t o r A

v e r a g e T e m p e

r a t u r e ( ° C )

10°C difference

Catalyst B

Catalyst A

7/21/2019 Aulas HDS



320

330

340

350

360

370

380

390

400

0 40 80 120 160 200 240 280 320 360Days on stream

R e a c t o r A

v e r a g e T e m p e r a t u r e ( ° C )

Normalized temperature

1,5°C/monthActual temperature

3,5°C/month

- Normalized temperature allows to correct for unit conditions and feedvariations

- Assessment of the real performances of the unit and the catalyst are muchmore precise

H d i U i

7/21/2019 Aulas HDS


Hydroprocessing UnitCold Scheme

Advantages: higher H2% in recycle gas, simpler, light feeds can be processed

Disadvantages: lower energy efficiency, larger high pressure separator

H d i U it

7/21/2019 Aulas HDS


Hydroprocessing UnitHot Scheme

Advantages: better energy efficiency, no need for stripper feed heating (most cases)

Disadvantages: need for recycle gas amine wash, loss of hydrogen

H d i U it

7/21/2019 Aulas HDS


Hydroprocessing UnitStripping section

The objective of the stripping section is to removed light ends from the diesel (H2S, CH’s)and/or to remove products lighter than the unit main product

H d i U it

7/21/2019 Aulas HDS


Gasoline hydrotreaters

In general, the objective of the gasoline hydrotreaters is to remove sulphur and nitrogenfrom reformer or isomerization feeds.Indeed, sulphur and nitrogen will poison anddegrade the performances of reforming and of isomerization catalysts

Gasoline hydrotreaters operate on 100% gaz phase, there is no need for distribution trays

Kerosene and Diesel hydrotreaters

The objective of the diesel hydrotreaters is to remove sulphur, reduce density and improve

cetane index. In the case of kerosene hydrotreaters, the objective is also to respectaromatics specification (naphthalenes and smoke point)

Diesel hydrotreaters operate in gas/liquid phase – reactor needs good distribution trays

Vacuum Gasoil hydrotreatersThe objective of the VGO hydrotreaters is to remove sulphur and nitrogen to prepare the

FCC feed. The objective is to be abble to produce 10 wtppm S gasoline and to improveFCC yields

VGO hydrotreaters operate in gas/liquid phase – reactor needs good distribution trays



7/21/2019 Aulas HDS



Kinetic Models

7/21/2019 Aulas HDS


Kinetic Models

Feed + H2

Desulphurized product+ H2 + H2

[ ] [ ] 1, >×−= nS k dt

S d n

LHSV

ek tck

S S n

T R

Eact

n

in

n

out

×−

−−

×

=×=

−×−0

11

11

1

1

×

−×

−×

−=

−− 011/11

1

1ln k LHSV S S n

R

E T

n

in

n

out

act

[ ]

[ ]

[ ]

[ ] ∫∫∫∫ =⇔−=

tcSin

Sout n

tcSout

Sin n

dt k

S

S d dt k

S

S d

00

Documents

Aulas HDS