195523917 Refining 06 Hydrotreating Process Complete

8/12/2019 195523917 Refining 06 Hydrotreating Process Complete

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2/31

Section 6 - Page 2

GAS OIL CONVERSION REFINERY: REVIEW

Naphtha

Kerosene

Naphtha

Hydrofiner

Kerosene

Hydrofiner

Distillate

Hydrofiner

Distillate

A

P

S

Crude

Atm.

Residue

VGOV

P

S

Vacuum

Residue

S

p

l

i

t

t

er

C

a

t

C

r

a

c

k

e

r

Cat. Naphtha

(Mogas)

LPG/Gas

Cat.

Bottoms

LPG

Light

Naphtha (Mogas)

Reformate(Mogas)

Kerosene

(Jet Fuel)

Fuel Oil

CatalyticReformer

Cat

Distillate

Diesel

Heating Oil


3/31

Section 6 - Page 3

COMPLEX CONVERSION REFINERY: REVIEW

Naphtha

Kerosene

Naphtha

Hydrofiner

Kerosene

Hydrofiner

Distillate

Hydrofiner

Distillate

A

P

S

Crude

Atm.

ResidueVGO

V

P

S

Vacuum

ResidueC

O

KE

R

S

p

l

i

t

t

e

r

C

a

t

C

r

a

c

k

e

r

Cat. Naphtha

(Mogas)

LPG/Gas

Cat.

Bottoms

to Fuel

LPG

Light

Naphtha (Mogas)

Reformate

(Mogas)

Kerosene

(Jet Fuel)

Coke

KN

LKGO

HKGO

Cracked

Distillate

Reformer

Cat

Distillate

Diesel

Heating Oil

Gas


4/31

Section 6 - Page 4

PRODUCT QUALITY TRENDS FOR ALL REFINERIES

ENVIRONMENTAL CONSIDERATIONS HAVE HISTORICALLYDICTATED REDUCED CONTAMINANT LEVELS IN FUELS

PRODUCTS, PRIMARILY SULPHUR

AT SAME TIME, AVERAGE REFINERY CRUDE SLATES HAVE

BEEN GETTING HEAVIER AND HIGHER IN SULPHUR

HEAVY OIL TREATING PROCESSES WERE DEVELOPED TO

DESULFURISE FUEL OIL PRODUCTS FOR SALE (HYDRO-

DESULPHURISATION OR HDS)

AS FUEL OIL DEMAND HAS DECREASED, HEAVY OIL

PROCESSES HAVE BEEN ADAPTED TO SERVE OTHER

PURPOSES AS PART OF REFINERY OPTIMISATION

DISTILLATE HDS UNITS DESIGNED FOR 0.3 WT% S ARE NOW

BEING PUSGED TO ACHIEVE LOWER SULPHUR (0.05 WT%)

TARGETS


5/31

Section 6 - Page 5

HYDROTREATING PROCESSES

HYDROTREATING IS THE MOST IMPORTANT EXXON PRODUCT

AND FEED QUALITY IMPROVEMENT PROCESS

TREAT PETROLEUM FRACTION WITH HYDROGEN IN THE

PRESENCE OF CATALYST

FEEDSTOCKS INCLUDE VIRGIN AND PROCESSED STREAM IN

NAPHTHA AND DISTILLATE BOILING RANGE

SIGNIFICANTLY REDUCES SULFUR, NITROGEN AND OTHER

HETEROATOMS

GENERALLY IMPROVES COLOR, ODOR, STABILITY AND

COMBUSTION CHARACTERISTICS

GROWTH STEMMED FROM AVAILABILITY OF HYDROGEN AND

REDUCTION IN SULFUR SPECIFICATIONS

REPLACED OLDER CHEMICAL TREATING METHODS IN MOST

CASES


6/31

Section 6 - Page 6

CHEMICAL TREATING STILL USED IN CERTAIN

CASES

CHEMICAL TREATING USED IN SPECIAL SITUATIONS

HYDROGEN AVAILABILITY

IMPROVE SPECIFIC PRODUCT QUALITY

SOMETIMES MORE ECONOMICAL

CAUSTIC (NAOH) / WATER WASH

USED TO REMOVE MERCAPTANS IN LIGHT ENDS STREAMS

MEROX (MERCAPTAN OXIDATION) PROCESS (UOP)

USES CAUSTIC + CATALYST

SWEETENING PROCESS CONVERTS MERCAPTANS (ODOUR) TO DISULPHIDES

EXTRACTIVE PROCESS

REMOVES DISUPHIDES


7/31

Section 6 - Page 7

PROCESSED DISTILLATE HYDROFINER

Make-up

Gas

Compressor

Recycle

Gas

Compressor

Feed

Pump

Make-up

Treat Gas

Reactors

Furnace

MEA

Scrubber

Rich

MEA

MEA Regeneration

Purge to

Fuel Gas

Stripper/

Hot and Cold

Separators

Steam

Wild Naphtha

to APS

Water

Fuel Gas to

MEA Scrubbing

Distillate

Product

To Tankage

Lean

MEA

Feed


8/31

Section 6 - Page 8

OPERATING CHARACTERISTICS OF HYDROFINERS

OPERATE AT HIGH (95+%) SERVICE FACTORS

ONE YEAR CYCLE TYPICAL, BUT LONGER CYCLES OFTEN

ACHIEVED

FLEXIBLE - CAN HANDLE MORE THAN ONE TYPE OF FEED

OPERATING TEMPERATURE INCREASED DURING CYCLE TO

COMPENSATE FOR CATALYST DEACTIVATION

HYDROGEN PARTIAL PRESSURE MINIMIZES DEACTIVATION

AT END OF CYCLE, CATALYST REGENERATED BY BURNING

OFF COKE


9/31

Section 6 - Page 9

LOW SULPHUR DIESEL LATEST CHALLENGE FOR

HYDROFINING

LEGISLATION LOWERING SULPHUR SPECIFICATIONS FOR

DIESEL PRODUCTS (0.05 WT% SULPHUR)

EXISTING DIESEL H/FS DESIGNED TO ACHIEVE 0.3 WT%

SOME EXISTING UNITS CAN BE OPERATED AT HIGHER

SEVERITY TO ACHIVE NEW SPECIFICATIONS

OTHER UNITS REQUIRE REVAMPING

ADDITIONAL REACTOR VOLUME

OTHER FACILITIES (PREHEAT, TREAT GAS, ETC.)


10/31

Section 6 - Page 10

COMPONENT SULPHUR CONTRIBUTIONS TO FUEL OIL POOL

ARAB HEAVY CRUDE (HYDROSKIMMING BASIS)

WT% POUNDS SULPHUR/

KB/D SULPHUR FUEL OIL BARREL

VIRGIN KERO FLUX 7 0.2 0.1

VGO 26 3.0 4.5

VAC RESID 23 6.0 9.0TOTAL POOL 56 4.0 13.6

TYPICAL SPEC. FOR RSFO 3.9 10.2

RESID CONTRIBUTES BULK OF SULPHUR TO FUEL OIL POOL

REMOVING 25% OF TOTAL SULPHUR IN COMPONENTS REQUIRED

TO MEET SPECIFICATION

75% OF VGO SULPHUR OR

38% OF RESID SULPHUR


11/31

Section 6 - Page 11

MAJOR FUEL OIL DESULPHURIZATION PROCESSES

GO-FINING (EXXONMOBIL TRADE NAME FOR GAS OIL HYDRO-

DESULPHURISATION)

GAS OIL RANGE FEED STREAMS

VACUUM GAS OIL (VGO)

HEAVY COKER GAS OIL (HKGO)

CAT CYCLE OILS (HCCO)

RESIDFINING (EXXONMOBIL TRADE NAME FOR RESID HYDRO-

DESULPHURISATION)

RESID FEEDSTOCKS

BOTH PROCESSES RESEMBLE HYDROFINERS, BUT AT MORE

SEVERE CONDITIONS AND WITH GREATER PROCESS COMPLEXITY


12/31

Section 6 - Page 12

GO-FINING

Sour

Water

Product

Stripper

Wild

Naphtha

Stripper

Off Gas

Lean

MEA

Purge

Gas

H2S

AbsorberRich

MEA

Hot

Separator

HDS

Reactors

Preheat

Furnace

Go-finerFeed

MEA

Regenerator

H2S

Sour

Water

ColdSeparator

Water

Wash

H2O

Sour

Water

Hydrogen

Make-up

Desulfurized

Gas Oil

Product

MEA

Make-up

Steam

Steam

Generation

Recycle GasCompressor


13/31

Section 6 - Page 13

GAS OIL CONVERSION REFINERY WITH HYDRODESUFURIZATION

Naphtha

Kerosene

Naphtha

Hydrofiner

Kerosene

Hydrofiner

Distillate

Hydrofiner

Distillate

A

P

S

Crude

Atm.

ResidueVGO

V

P

S

Vacuum

Residue

S

p

l

i

t

t

e

r

C

a

t

C

r

a

c

k

e

r

Cat. Naphtha

(Mogas)

LPG/Gas

Cat.

Bottoms

LPG

Light

Naphtha (Mogas)

Reformate(Mogas)

Kerosene

(Jet Fuel)

Low Sulfur

Fuel Oil

CatalyticReformer

Cat

Distillate

Diesel

Heating Oil

Residfiner

Gofiner


14/31

Section 6 - Page 14

HYDROTREATING PROCESSES REQUIRE

SUPPORT PROCESSING

REFINERY TREAT GAS SYSTEM PROVIDES HYDROGEN TO

HYDROTREATING/ HYDROCONVERSION UNITS

INCLUDES H2 GENERATION, DISTRIBUTION AND RECOVERY

SULPHUR REMOVAL FROM REFINERY TREAT GAS STREAMS

REQUIRED BY ENVIRONMENTAL LIMITATIONS ON REFINERY

SULPHUR EMISSIONS

INCLUDES RECOVERY OF ELEMENTAL SULPHUR AS

REFINERY BYPRODUCT

CONTAMINANT REMOVAL FROM REFINERY EFFLUENT WATER

ONSITE SOUR WATER STRIPPING

OFFSITE WASTE WATER TREATING


15/31

Section 6 - Page 15

RESIDFINING

MEA

ScrubbingMEA

Regeneratio

n

Guard

Chamber

Feed

Furnace

HDS

Reactors

Hot

Separator

Quench

Water

Treat Gas

Furnace

Product

Stripper

Cold

Separator

Sour Water

(To Stripping)

Hot Sep. Vapor

Codenser

Trim

Cooler

Steam

Generation

CW

Sour Water

(To Stripper)

C1-C4

Fuel Gas

CW

Compressor

400/650 HAGO

(Optional)

400+

Product

C5-400

Wild Naphtha

CW

Purge

Gas

KO Drum

Recycle Gas

Compressor

Make-up H2from

H2Plant 950 psig

FeedFilter

FeedSurge

Drum

Hot Feed

(350F)

Hot Sep. Vapor

Cold Sep. Liquid

Hot Sep.

Vapor Feed

Hot Sep. Vapor

Treat Gas

MEA


16/31

Section 6 - Page 16

CAT FEED HYDROTREATER (CFHT)

The conversion of cat cracking feed to higher value gasoline and light ends can be

significantly improved by severe hydrotreating of the more aromatic gas oils,

particularly those that contain nitrogen and/or heavy metals (which are different

types of catalytic cracking catalyst poisons). If the multi-ring aromatics in the gas

oils can be saturated such that only one core aromatic remains in the molecular

structure. That molecule will eventually be converted to gasoline or light-ends. Also,

higher cat cracking conversion can be achieved if three ring (cores) aromatics canhe reduced because of lower coke yields. Coke burning capacity often limits the cat

cracking unit conversion level.

In order to hydrotreat PGO at this severity, it is necessary to operate around 1500

psig and below 1 V/V/hr. Operating temperatures are in the range of 670-730F EIT

(a kinetic average). For typical feed stocks, we expect 600-1100 SCF/barrel ofhydrogen consumption. Typical run lengths are from less than 1 year to over 3

years.


17/31

Section 6 - Page 17

CAT FEED HYDROTREATER (CFHT)

Figure 4 is a flow plan of the Baytown Cat Feed Hydrotreater. The feed is mixed

with hot hydrogen at the exit of the recycle H2 furnace. Because of possible fouling

of the catalyst beds, the feed goes through a filter to remove particulates before the

hydrogen is added. The H2 and feed go through a small reactor, filled with the

catalyst, which acts as a guard reactor to remove metal contaminants. Then the

mixture goes through the reactor train. After the reactors, the liquid and gas are

separated in flash drums, and the hydrogen is recycled to the furnace. On the way,it passes through an amine scrubber to remove the H2S formed in the reactors.

The liquid goes to the fractionator, where an overhead stream is taken which is

separated into gas and naphtha. The fractionator bottoms is the hydrotreated

product that can be used as high quality catalytic cracking feed.


18/31

Section 6 - Page 18

FIG 4 - CAT FEED HYDROTREATER (CFHT)

MAIN REACTORS

SEPARATORS

AMINE

SCRUBBER

RECYCLE HYDROGEN

FRACTIONATOR

GAS AND

NAPHTHA

CAT CRACKER

FEED

FILTERFEED

COMP

MAKEUP

HYDROGEN

FURNACE

GUARD

REACTOR


19/31

Section 6 - Page 19

GO-FINING

GO-fining is a process for sulphur reduction in gas oils. It is an Exxon Engineering

process, and several units have been built world-wide, especially in Venezuela. The

only one in the Exxon Company, U.S.A. is at Baytown (HU6A/6B now in diesel andjet fuel service).

Previously, the process application is for reducing sulphur in fuel oil by

desulphurizing the flux oil to be blended with vacuum residuum. Now because of

poor quality crude and tighter diesel specifications, these two units are used for

severe hydrotreating of middle distillates.

Typically operating conditions for Go-finers are 600 PSIG, and 650F. The catalyst

is cobalt/molybdenum or nickel/molybdenum, and can be regenerated and reused.

Regeneration is done offsite. This is required after about 18 months onstream. The

treat gas rate is normally about 1000 SCF per barrel of feed, and hydrogen

consumption ranges from about 200 to 500 SCF/B.

Feedstock used to be 650-1050F cut range gas oil, from any source. Sulphur in

the feed was reduced by 75 percent. Now the feeds are 350-520F and 520-620F

distillate.


20/31

Section 6 - Page 20

GO-FINING

A small yield of gas and naphtha occur, but the 350F + cut is usually 100 percent

on feed.

A flow plan is shown in Figure 5.

Feed exchanges heat with the reactor effluent and is mixed with the recyclehydrogen stream. This goes through the furnace, and then through the reactors in

series. The reactor effluent is separated from recycle hydrogen in the hot separator.

The hydrogen is cooled and goes to the cold separator, where more liquid is

separated out. The hydrogen goes then to a water wash and an amine scrubber

before being compressed for recycle. Liquid from both the hot and cold separators

goes to the product stripper. By steam stripping, the light ends are separated from

the gas oil product.


21/31

Section 6 - Page 21

GO-FINING


22/31

Section 6 - Page 22

Hydrofining and Hydrotreating

Hydrofining and hydrotreating are broad terms which in general refer to processes

that remove or convert impurities by catalytic treatment with hydrogen. The effect is

primarily In the reaction of hydrogen with sulphur and nitrogen in heavier molecules

to produce hydrogen sulfide and ammonia. For example:

2 RNH2 + H2 => 2 NH3 + 2RH

Amine Ammonia + Paraffin

and

2 RSH + H2 => 2 H2S + 2 RH

Mercaptan

Other reactions include saturation of olefins and reduction of oxygen compounds,

such as:

RC = C + H2 => R - C - C

Olefin Paraffin

and


23/31

Section 6 - Page 23

The net result is an improvement in many properties, such as odour, colour,

corrosivity, gum formation, stability, burning characteristics, cracking quality and

carbon forming in cracking. It has largely replaced the old process of acid treatmentand clay percolation. In general, hydrotreating refers to any process short of

conversion, while hydrofining usually means relatively mild conditions for colour

improvement, and hydro-desulphurization means more severe treatment required

for deep desulphurisation of heavier oils. Hydrofining is an Exxon Engineering

process, which is very similar to a number of other processes developed by other oil

companies.

The process flow in a hydrotreater is essentially the same regardless of the

operating conditions or catalyst. Please refer to the flow plan in Figure 6 on the next

page.

The feed is heated to reaction temperature in a furnace, and is joined by a stream ofhydrogen. The mixture flows down through the fixed bed of catalyst in the reactor.

The effluent is cooled and the liquid is separated from the gas in a separator, which

usually (but not always) provides a hydrogen recycle stream. The liquid is again

separated at lower pressure, and the product is stripped for flash correction.



24/31

Section 6 - Page 24

The catalyst may be cobalt/molybdenum, or nickel/molybdenum, depending on the

feedstock and the purpose of the unit. For but desulphurization, cobalt/

molybdenum is the more common. Nickel catalysts are core effective in removingnitrogen than cobalt molybdenum, and are usually used with heavier feedstocks.

Catalysts are usually in the form of 1/60 extrudate. Most catalysts are now

regenerated ex-situ (offsite).

When either new or regenerated catalyst is loaded in the reactors, it is necessary to

activate the metal oxides (cobalt, nickel, or molybdenum) by carefully controlled

sulphiding. This is done in a hydrogen rich environment, but if the metals arereduced before they are completely sulphided, a large loss of catalyst activity will

result. Operating conditions also depend on the feedstock. In general, the range of

conditions are these:

Hydrofining Hydrodesulphurization

Temperature F 500 - 700 600 - 800Pressure, PSIG 200 - 600 600 - 3,000

Feed Rate, V/Vlhr 0.5 - 5.0 0.2 - 1.2

H2 Treat SCF/B 200 - 1,000 1,000 - 3,000

H2 Consumption SCF/B 10 - 500 200 - 1,000



25/31

Section 6 - Page 25

Figure 6 - Hydrotreater flow plan

SEPARATORS

FUEL GAS

REACTORS

FURNACE

HYDROGEN

DEHYDRATOR

PRODUCT


26/31

Section 6 - Page 26

Some of the operating variables and the effects of changing them are:

Variable Effect

Increased feed rate Reduce sulphur and nitrogen removal

Increased temperature Increase sulphur and nitrogen removal

Increased pressure Increase sulphur and nitrogen removal

Increased hydrogen purity Increase sulphur and nitrogen removal

Increased treat gas rate Increase sulphur and nitrogen removal



27/31

Section 6 - Page 27

CAT FEED HYDROTREATER


28/31

Section 6 - Page 28

HYDROFINING REACTIONS


29/31


30/31

Section 6 - Page 30

FIGURE 1 - SCHEMATIC FLOW PLAN -

HYDROTREATER


31/31

Section 6 - Page 31

GO-FINER FLOW DIAGRAM

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195523917 Refining 06 Hydrotreating Process Complete

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