The document outlines the crude oil refining process, which consists of three main steps: separation, conversion, and purification. It details the physical and chemical processes involved, including distillation and catalytic reactions, as well as operational units like crude distillation units (CDU) and vacuum distillation units (VDU). Additionally, it discusses secondary processing units such as thermal and catalytic crackers, highlighting their roles in producing various refined products while addressing environmental considerations.

1. CRUDE OIL REFINING PROCESS

2. CONTENTS
• INTRODUCTION
• PROPERTIES
• TYPES OF PROCESS
• REFINING OPERATIONS

3. PROPERTIES IN REFINERY ENGINEERING
• API GRAVITY
• WATSON CHARACTERIZATION FACTOR
• VISCOSITY
• SULFUR CONTENT
• TRUE BOILING POINT (TBP) CURVE
• POUR POINT
• FLASH AND FIRE POINT
• ASTM DISTILLATION CURVE
• OCTANE NUMBER

4. INTRODUCTION
-REFINING IS CARRIED OUT IN THREE MAIN STEPS.
1. SEPARATION
2. CONVERSATION
3. PURIFICATION

5. 1) SEPARATION
• THE OIL IS SEPARATED INTO ITS CONSTITUENTS BY DISTILLATION, AND SOME OF
THE REFINING COMPONENTS (SUCH AS THE REFINERY GAS) ARE FURTHER
SEPARATED WITH CHEMICAL REACTIONS AND BY USING SOLVENTS WHICH
DISSOLVE ONE COMPONENT OF A MIXTURE SIGNIFICANTLY BETTER THAN
ANOTHER.

6. 2) CONVERSATION
-THE VARIOUS HYDROCARBONS PRODUCED ARE THEN CHEMICALLY
ALTERED TO MAKE THEM MORE SUITABLE FOR THEIR INTENDED PURPOSE. FOR EXAMPLE,
NAPHTHA'S ARE "REFORMED" FROM PARAFFIN'S AND NAPHTHENES INTO AROMATICS.
THESE REACTIONS OFTEN USE CATALYSIS, AND SO SULFUR IS REMOVED
FROM THE HYDROCARBONS BEFORE THEY ARE REACTED, AS IT WOULD 'POISON' THE
CATALYSTS USED.
THE CHEMICAL EQUILIBRIA ARE ALSO MANIPULATED TO ENSURE A
MAXIMUM YIELD OF THE DESIRED PRODUCT.

7. 3) PURIFICATION
• THE HYDROGEN SULFIDE GAS WHICH WAS EXTRACTED FROM THE REFINERY GAS IN STEP
1(SEPARATION) IS CONVERTED TO SULFUR, WHICH IS SOLD IN LIQUID FORM TO FERTILIZER
MANUFACTURERS.
• THE PLANT AT MARSDEN POINT ALSO MANUFACTURES ITS OWN HYDROGEN AND PURIFIES
ITS OWN EFFLUENT WATER.
• THIS WATER PURIFICATION, ALONG WITH GAS 'SCRUBBING' TO REMOVE UNDESIRABLE
COMPOUNDS FROM THE GASES TO BE DISCHARGED INTO THE ATMOSPHERE, ENSURES THAT
THE REFINERY HAS MINIMAL ENVIRONMENTAL IMPACT.

8. TYPES OF PROCESSES
CRUDE OIL REFINING PROCESS ARE CLASSIFIED INTO TWO DIFFERENT TYPES,
THEY ARE
A. PHYSICAL PROCESS AND
B. CHEMICAL PROCESS

9. A) PHYSICAL PROCESS
THERE ARE DIFFERENT TYPES OF PHYSICAL PROCESS ARE PRESENT
• DISTILLATION
• SOLVENT EXTRACTION
• PROPANE DEASPHALTING
• SOLVENT DE WAXING
• BLENDING

10. B) CHEMICAL PROCESS
CHEMICAL PROCESS IS CLASSIFIED IN TO TWO TYPES
1. THERMAL PROCESS : UNDER THERMAL IT HAS THREE PROCESS THEY ARE
A. VISBREAKING
B. DELAYED COKING
C. FLEXI COKING
2. CATALYTIC PROCESS : THIS PROCESS ALSO HAVE DIFFERENT PROCESS FOR REFINING THEY ARE
A. HYDRO TREATING
B. CATALYTIC REFORMING
C. CATALYTIC CRACKING
D. HYDROCRACKING
E. CATALYTIC DE WAXING
F. ALKYLATION
G. POLYMERIZATION
H. ISOMERIZATION

11. REFINING OPERATIONS
---THERE ARE TWO TYPES OF OPERATIONS ARE PRESENT IN REFINING PROCESS
THEY ARE
• PRIMARY PROCESSING UNITS
• SECONDARY PROCESSING UNITS

12. -PRIMARY PROCESSING UNITS
PRIMARY PROCESSING UNITS ARE CLASSIFIED INTO TWO TYPES THEY
ARE
1. CRUDE DISTILLATION UNIT (CDU)
2. VACUUM DISTILLATION UNIT (VDU)

13. CRUDE DISTILLATION UNIT (CDU)
• THE MAIN PROCESS TECHNOLOGIES ENABLES THE SEPARATION OF THE CRUDE INTO ITS
VARIOUS PRODUCTS.
• USUALLY, FIVE PRODUCTS ARE GENERATED FROM THE CDU NAMELY GAS + NAPHTHA,
KEROSENE, LIGHT GAS OIL, HEAVY GAS OIL AND ATMOSPHERIC RESIDUE AS SHOWN IN THE
FIGURE
• IN SOME REFINERY CONFIGURATIONS, TERMINOLOGIES SUCH AS GASOLINE, JET FUEL AND
DIESEL ARE USED TO REPRESENT THE CDU PRODUCTS WHICH ARE USUALLY FRACTIONS
EMANATING AS PORTIONS OF NAPHTHA, KEROSENE AND GAS OIL.

14. C.D.U
CRUDE OIL
GAS+NAFTHA
(SENDS TO NAFTHA HYDRO
TREATERS)
KEROSENE
LIGHT GAS OIL
ATMOSPHERIC RESIDUE
(V.D.U)
Operating Conditions : The temperature at the entrance of the furnace where the crude enters is 200 –
280oC. It is then further heated to about 330 – 370oC inside the furnace. The pressure maintained is about 1 bar.
CRUDE DISTILLATION UNIT (CDU)

15. ELEMENTS IN CRUDE DISTILLATION UNIT
---THE UNIT COMPRISING OF AN
1. SIDE STRIPPERS,
2. HEAT EXCHANGER NETWORK,
3. FEED DE-SALTER,
4. FURNACE,
5. PUMP-AROUND UNITS
LET US DISCUSS BRIEFLY ABOUT ELEMENTS IN CDU.

16. 1) SIDE STRIPPERS
• IN VERY GENERAL TERMINOLOGY, THE FEED STREAM ENTERS MOST FRACTIONATOR
COLUMNS AT ABOUT THE MID-POINT OF A COLUMN'S HEIGHT. THE SECTION ABOVE THE
FEED ENTRY POINT IS CALLED THE "RECTIFYING" SECTION. THE SECTION BELOW THE FEED
ENTRY IS CALLED THE "STRIPPING" SECTION.
• A STRIPPER IS SO NAMED BECAUSE IT HAS NO RECTIFYING SECTION.
• THE FEED TO A STRIPPER USUALLY ENTERS AT THE TOP TRAY OF THE STRIPPER OR VERY
CLOSE TO THE TOP TRAY.
• EXAMPLES OF STRIPPERS IN AN OIL REFINERY ARE:
-- SOUR WATER STRIPPERS IN WHICH STEAM IS USED TO REMOVE H2S AND NH3 FOR SOUR
WATERS.
-- SIDE-CUT STRIPPERS ON CRUDE OIL ATMOSPHERIC DISTILLATION TOWERS IN WHICH
STEAM IS USED TO REMOVE THE LIGHTEST COMPONENTS FROM SIDE-CUT PRODUCTS SUCH
AS KEROSENE, JET FUEL, OR DIESEL OIL.

17. 2) HEAT EXCHANGER NETWORK
• TWO HEAT EXCHANGER NETWORKS EXIST IN THE CRUDE DISTILLATION UNIT, ONE BEFORE THE
CRUDE DESALTER AND ONE AFTER THE CRUDE DESALTER.
• THE HEAT EXCHANGER NETWORKS FACILITATE ENERGY RECOVERY FROM HOT PRODUCT,
NAPHTHA+STEAM VAPOR AND REFLUX STREAMS TO HEAT THE CRUDE OIL IN AN INDIRECT
HEAT TRANSFER MODE I.E, USING HEAT EXCHANGERS.
• THEREFORE, THE DESIGN AND OPERATION OF A HEAT EXCHANGER NETWORK IS VERY
IMPORTANT IN THE CRUDE DISTILLATION UNIT.
• THE HEAT EXCHANGER NETWORKS ENABLE TO INCREASE THE CRUDE OIL STREAM
TEMPERATURE TO ABOUT 200 – 230 OC WHICH IS SIGNIFICANTLY HIGHER THAN THE CRUDE
OIL SOURCE TEMPERATURE (ABOUT 20 – 30 OC).
• CRUDE DISTILLATION UNITS WITHOUT HEAT EXCHANGER NETWORKS HAVE HIGHER FURNACE
LOAD TARGETS. THEY ALSO CAUSE MORE POLLUTION DUE TO BURNING MORE FUEL OIL AND
FUEL GAS STREAMS.

18. 3) FEED DE-SALTER
• CRUDE OIL CONSISTS OF DISSOLVED SALTS AND THEY TEND TO CAUSE FOULING AND
CORROSION IN VARIOUS PROCESS EQUIPMENT'S. THEREFORE, DISSOLVED SALTS NEED TO BE
REMOVED USING A SEPARATION PROCESS.
• THE CRUDE DESALTING UNIT IS A SEPARATION PROCESS. HERE, WATER ALONG WITH OTHER
TRACE CHEMICALS SUCH AS CAUSTIC AND ACID ARE ALLOWED TO ENTER A MIXING UNIT
ALONG WITH THE CRUDE OIL.
• THE MIXTURE OF CRUDE OIL AND WATER IS SUBSEQUENTLY PASSED THROUGH AN
ELECTROSTATIC PRECIPITATOR CUM GRAVITY SETTLER. THE ELECTROSTATIC FIELD ENABLES
THE AGGLOMERATION OF WATER DROPLETS AND AIDS FASTER GRAVITY SETTLING.
• AN ESSENTIAL ISSUE FOR THE GOOD PERFORMANCE OF CRUDE DESALTER IS THE
TEMPERATURE OF THE OPERATION. USUALLY, HIGH EFFICIENCY OF SALT REMOVAL IS
POSSIBLE BETWEEN 100 – 300 OF.
• THEREFORE, THE CRUDE OIL IS HEATED TO ABOUT 250 OF BEFORE IT ENTERS THE DESALTER
UNIT.
• USUALLY, A TWO STAGE DESALTING PROCESS IS DEPLOYED. WHEN HIGHER SALT REMOVAL

19. 4) FURNACE
• THE FURNACE IS AN IMPORTANT CONSTITUENT IN THE CRUDE DISTILLATION UNIT
• HERE, FUEL OIL AND FUEL GAS (HEAVIER PRODUCTS) OBTAINED FROM THE REFINING PROCESS
ITSELF ARE BURNT TO INCREASE THE CRUDE OIL TEMPERATURE.
• TYPICALLY IN REFINERIES, THE CRUDE OIL IS HEATED TO A TEMPERATURE THAT ENABLES
OVERFLASH CONDITIONS IN THE MAIN CRUDE DISTILLATION COLUMN.
• THE CONCEPT OF OVER FLASH IS THAT THE CRUDE IS HEATED TO SUCH A TEMPERATURE
THAT ENABLES AN ADDITIONAL 5 % VAPORIZATION WITH RESPECT TO THE RESIDUE
PRODUCT. IN OTHER WORDS, THE RESIDUE FRACTION VAPORS AMOUNTING TO 5 % OF THE
TOTAL VOLUME OF THE CRUDE OIL ARE DESIRED.
• DEPENDING UPON THE QUALITY OF THE CRUDE, THE DESIRED TEMPERATURE FOR THE CRUDE
OIL IS ABOUT 600 - 700 OF.

20. 5) PUMP-AROUND UNITS
• PUMP AROUND UNITS ARE MOST ESSENTIAL UNITS IN THE CRUDE DISTILLATION COLUMN.
• THEY ARE USED TO MAINTAIN GOOD REFLUX CONDITIONS IN THE MAIN COLUMN AND
THEREFORE THE DESIRED PRODUCT QUALITY.
• THEY ALSO PROVIDE A GOOD HEAT SOURCE AS THE LIQUID STREAMS ARE AT HIGHER
TEMPERATURES. THEREFORE, THEY ARE ALSO IMPORTANT UNITS IN THE HEAT EXCHANGER
NETWORK.
• THE COOLED LIQUID IS SENT BACK TO A SECTION ABOVE.
• USUALLY TWO PUMP AROUNDS ARE USED IN CONVENTIONAL DESIGNS. HOWEVER, THERE ARE
CRUDE DISTILLATION UNITS WITH EVEN THREE PUMP AROUND UNITS.

22. 1. WHAT IS THE MOST IMPORTANT ASPECT OF MAIN COLUMN IN THE CDU?
THE COLUMN HYDRAULICS WITH A GOOD DISTRIBUTION OF LIQUID AND VAPOR IN
THE CDU IS THE MOST IMPORTANT ASPECT.
2. WHAT SIMILARITIES ARE THERE FOR THE CDU WITH VACUUM DISTILLATION UNIT?
ONLY BASIC DIFFERENCE IS THAT WHILE WE OPERATE THE VDU AT LOWER
PRESSURE (30 – 40 MM HG), THE OPERATING TEMPERATURES WILL BE LOWER THAN THOSE IN THE
CDU. OTHERWISE, THE BASIC PRINCIPLES REMAIN THE SAME.
3. WHAT PRIMARY DISADVANTAGE EXISTS BY USING LIVE STEAM IN THE CDU COLUMNS?
LIVE STEAM ONCE IT ENTERS THE COLUMN DOES NOT CONDENSE ANYWHERE, AS
WE DON’T WANT ANY CONDENSATION TO HAPPEN. WHEN LIVE STEAM IS USED, VAPOR LOAD
INCREASES SIGNIFICANTLY IN THE COLUMN

23. VACUUM DISTILLATION UNIT
• THE ATMOSPHERIC RESIDUE WHEN PROCESSED AT LOWER
PRESSURES DOES NOT ALLOW DECOMPOSITION OF THE
ATMOSPHERIC RESIDUE AND THEREFORE YIELDS LVGO, HVGO
AND VACUUM RESIDUE (FIGURE).
• THE LVGO AND HVGO ARE EVENTUALLY SUBJECTED TO
CRACKING TO YIELD EVEN LIGHTER PRODUCTS.
• THE VDU CONSISTS OF A MAIN VACUUM DISTILLATION
COLUMN SUPPORTED WITH SIDE STRIPPERS TO PRODUCE THE
DESIRED PRODUCTS.
• THEREFORE, VDU IS ALSO A PHYSICAL PROCESS TO OBTAIN
THE DESIRED PRODUCTS.
OPERATING CONDITIONS : THE PRESSURE MAINTAINED
IS ABOUT 25 – 40 MM HG. THE TEMPERATURE IS KEPT AT
ATMOSPHER
IC RESIDUE
LIGHT
VACUUM
GAS OIL
(LVGO)
HEAVY VACUUM
GAS OIL (HVGO)
VACUUM RESIDUE
V.D.U
H-
H
D
S
SENDS TO T C

24. --SECONDARY PROCESSING UNITS
1. THERMAL CRACKER
2. HYDROTREATERS
3. SEPARATORS
4. FLUIDIZED CATALYTIC CRACKER
5. STREAM SPLITTERS
6. GAS TREATING
7. REFORMER
8. ALKYLATION AND ISOMERIZATION
9. BLENDING POOLS
==THESE ARE THE SECONDARY PROCESSING UNITS LET US KNOW ABOUT
BRIEFLY.

25.  WHAT IS CRACKING?
• CRACKING INVOLVES THE DECOMPOSITION OF HEAVIER HYDROCARBON FEEDSTOCK'S TO
LIGHTER HYDROCARBON FEED STOCKS.
• CRACKING CAN BE CARRIED OUT TO ANY HYDROCARBON FEEDSTOCK BUT IT IS USUALLY
APPLIED FOR VACUUM GAS OIL (VGO)
• CRACKING CAN BE WITH OR WITHOUT A CATALYST.
 THERMAL CRACKER

26.  THERMAL CRACKER
• THERMAL CRACKER INVOLVES A CHEMICAL CRACKING PROCESS
FOLLOWED BY THE SEPARATION USING DIFFERENT BOILING
POINT TO YIELD THE DESIRED PRODUCTS.
• THERMAL CRACKING YIELDS NAPHTHA + GAS, GASOIL AND
THERMAL CRACKED RESIDUE (FIGURE).
• IN SOME PETROLEUM REFINERY CONFIGURATIONS, THERMAL
CRACKING PROCESS IS REPLACED WITH DELAYED COKING
PROCESS TO YIELD COKE AS ONE OF THE PETROLEUM REFINERY
PRODUCTS.
OPERATING CONDITIONS : THE TEMPERATURE SHOULD BE
KEPT AT AROUND 450 – 500OC FOR THE LARGER HYDROCARBONS
TO BECOME UNSTABLE AND BREAK SPONTANEOUSLY. A 2-3 BAR
T.C UNIT
VACUUM
RESIDUE
GAS +
NAPHTHA
(SENDS
TO
N – HDS)
CRACKED
GAS OIL
(SENDS
TO
L - HDS
CRACKED
RESIDUE
SENDS TO
FUEL OIL POOL

27.  HYDROTREATERS
• FOR MANY REFINERY CRUDES SUCH AS ARABIC AND KUWAIT CRUDES, SULFUR CONTENT IN THE
CRUDE IS SIGNIFICANTLY HIGH.
• THEREFORE, THE PRODUCTS PRODUCED FROM CDU AND VDU CONSIST OF SIGNIFICANT
AMOUNT OF SULFUR. HENCEFORTH, FOR DIFFERENT PRODUCTS GENERATED FROM CDU AND
VDU, SULFUR REMOVAL IS ACCOMPLISHED TO REMOVE SULFUR AS H2S USING HYDROGEN.
• THE H2 REQUIRED FOR THE HYDROTREATERS IS OBTAINED FROM THE REFORMER UNIT WHERE
HEAVY NAPHTHA IS SUBJECTED TO REFORMING TO YIELD HIGH OCTANE NUMBER REFORM
PRODUCT AND REFORMER H2 GAS.

28. • IN THIS N-HDS PROCESS, LIGHT ENDS FROM THE REFORMER GAS ARE STRIPPED TO ENHANCE
THE PURITY OF HYDROGEN TO ABOUT 92 % (FIGURE).
• CONCEPTUALLY, HYDRO TREATING IS REGARDED AS A COMBINATION OF CHEMICAL AND
PHYSICAL PROCESSES.
OPERATING CONDITIONS: THE OPERATING CONDITIONS OF A HYDROTREATERS
VARIES WITH THE TYPE OF FEED.
FOR NAPHTHA FEED, THE TEMPERATURE MAY BE KEPT AT AROUND 280-425OC
AND THE PRESSURE BE MAINTAINED AT 200 – 800 PSIG.
NAPHTHA -
HDS
HYDEROGEN
(HYDRODESULPHURIZATION
OF INTERMEDIATE
PRODUCTS) TO L & H - HDS
DESULFURIZED GAS +
NAPHTHA ( SENDS TO C4 –
SEP)
SEPARATION OF GAS AND
NAPHTHA (LN + HN)
GAS+ NAFTHA
( FROM C.D.U)
DESULFURIZED GAS + NAPHTHA
GAS +NAPHTHA
( FROM THERMAL.
CRAC.)
DESULFURIZED GAS + NAPHTHA FOR
NAPHTHA STABILIZATION (TO SATURATE UNSATURATES) FROM
HGO - HDS
REFORMER OFF-GAS (FROM CATALYTIC REFORMER)
H2 PURIFICATION BY LOSS OF LIGHT ENDS IN N-HDS PROCESS

29. • FOR LGO HYDRO TREATING CASE, ALONG WITH DIESEL MAIN PRODUCT, NAPHTHA AND GAS
TO C5 FRACTION ARE OBTAINED AS OTHER PRODUCTS (FIGURE).
• ONLY FOR KEROSENE HYDROTREATERS, NO LIGHTER PRODUCT IS PRODUCED IN THE HYDRO
TREATING OPERATION.
LGO - HDS
KEROSENE (FROM
C.D.U)
LIGHT GAS OIL (
FROM C.D.U )
DESULFURIZED GAS + NAPHTHA
NAPHTHA STABILIZATION (TO SATURATE & UNSATURATES)
SENDS TO N-HDS
DESULFURIZED KEROSENE (SENDS TO
KEROSENE SPLITTER ) SPLITTING
KEROSENE FOR BLENDING POOL AND
PRODUCT
DESULFURIZED LGO (SENDS TO GAS OIL
POOL ) TO GENERATE AUTO DIESEL
AND HEATING OIL PRODUCTS

30. • HYDRO TREATING IN SOME HYDROTREATERS PRODUCTS LIGHTER THAN THE FEED ARE
PRODUCED. FOR INSTANCE, IN THE LVGO/HVGO HYDROTREATERS, DESULFURIZATION OF LVGO
& HVGO (DIESEL) OCCURS IN TWO BLOCKED OPERATIONS AND DESULFURIZED NAPHTHA
FRACTION IS PRODUCED ALONG WITH THE DESULFURIZED GAS OIL MAIN PRODUCT (FIGURE).
HEAVY
GAS
OIL
- HDS
LIGHT VACCUME GAS OIL
FROM V.D.U
HEAVY VACCUME GAS OIL
FROM V.D.U
DESULFURIZED GAS + NAPHTHA FOR
NAPHTHA STABILIZATION (TO SATURATE UNSATURATES) SENDS
TO N- HDS
DESULFURIZED LVGO (SENDS TO LVGO SPLITTER)
TO BY-PASS THE STREAM
DESULFURIZED HVGO ( SENDS TO F.C.C )
TO CATALYTICALLY CRACK AND PRODUCE
LIGHTER PRODUCTS

31.  SEPARATORS
• THE GAS FRACTIONS FROM VARIOUS UNITS NEED CONSOLIDATED SEPARATION AND REQUIRE
STAGE WISE SEPARATION OF THE GAS FRACTION.
• FOR INSTANCE, C4 SEPARATOR SEPARATES THE DESULFURIZED NAPHTHA FROM ALL
SATURATED LIGHT ENDS GREATER THAN OR EQUAL TO C4S IN COMPOSITION (FIGURE).
SEPERATOR – C4
Saturated light ends (SENDS TO C3-SEP.)
To separate C3 from C4 fraction
Desulfurized LN+HN ( SENDS TO Naphtha
Splitter ) To split Light Naphtha (LN)
from Heavy Naphtha (HN)
Desulfurized Gas + Naphtha
( FROM N- HDS )
Separation of gas and
Naphtha (LN + HN)

32. • ON THE OTHER HAND, C3 SEPARATOR SEPARATES BUTANES (BOTH ISO AND BUTANES)
FROM THE GAS FRACTION (FIGURE).
SEPERATOR – C3
SATURATED LIGHT ENDS (FROM C4-SEP.)
TO SEPARATE C3 FROM C4 FRACTION
SATURATED LIGHT ENDS (< C3S SENDS TO C2 SEP.)
TO SEPARATE C3S FROM THE STREAM
C4S (NORMAL AND ISOBUTANE MIXTURE) SENDS TO
N-BUTANE SPLITTER TO BY-PASS THE STREAM
CRACKED LIGHT ENDS(FROM CATI. CRACK)
TO SEPARATE C3’S FROM BUTANES

33. • SIMILARLY, THE C2 SEPARATOR SEPARATES THE SATURATED C3 FRACTION THAT IS REQUIRED
FOR LPG PRODUCT GENERATION AND GENERATES THE FUEL GAS + H2S PRODUCT AS WELL
(FIGURE).
OPERATING CONDITIONS: MOST OIL AND GAS SEPARATORS OPERATE IN
THE PRESSURE RANGE OF 20 – 1500 PSI.
C2 -
SEPERATOR
FUEL GAS + H2S (SENDS TO GAS TREATING UNIT)
TO RECOVER SULFUR AND PRODUCE FUEL GAS
C3S (SENDS TO LPG POOL UNIT )
TO RECOVER SULFUR AND PRODUCE FUEL GAS
SATURATED LIGHT ENDS (FROM C3 SEP.)
TO SEPARATE C3S FROM THE STREAM

34.  FLUIDIZED CATALYTIC CRACKER
• THE UNIT IS ONE OF THE MOST IMPORTANT UNITS OF THE MODERN REFINERY.
• THE UNIT ENABLES THE SUCCESSFUL TRANSFORMATION OF DESULFURIZED HVGO TO
LIGHTER PRODUCTS SUCH AS UNSATURATED LIGHT ENDS, LIGHT CRACKED NAPHTHA, HEAVY
CRACKED NAPHTHA, CYCLE OIL AND SLURRY (FIGURE).
• THEREBY, THE UNIT IS USEFUL TO GENERATE MORE LIGHTER PRODUCTS FROM A HEAVIER
LOWER VALUE INTERMEDIATE PRODUCT STREAM.
• CONCEPTUALLY, THE UNIT CAN BE REGARDED AS A COMBINATION OF CHEMICAL AND
PHYSICAL PROCESSES.

35. F.C.C
GASEOUS FCC PRODUCT ( SENDS TO GAS TREATING
UNIT) FOR SULFUR RECOVERY AND FUEL GAS PRODUCTION
UNSATURATED LIGHT ENDS ( SENDS TO ALKYLATION UNIT )
CONVERSION OF C3-4 TO ALKYLATES
LIGHT CRACKED NAPHTHA (SENDS TO GASOLINE POOL)
TO GENERATE PREMIUM AND REGULAR GASOLINE
HEAVY CRACKED NAPHTHA (SENDS TO GASOLINE POOL)
TO GENERATE PREMIUM AND REGULAR GASOLINE
CYCLE OIL (SENDS TO GAS OIL POOL) TO
GENERATE AUTO DIESEL AND HEATING OIL PRODUCTS
SLURRY (SENDS TO FUEL OIL POOL) TO GENERATE
HARING DIESEL, HEAVY FUEL OIL AND BUNKER OIL
DESULFURIZED HVGO ( FROM HGO - HDS ) TO
CATALYTICALLY CRACK AND PRODUCE LIGHTER PRODUCTS
Operating Conditions: The temperature should be maintained at 34oC with pressure ranging from
75 kPa to 180 kPa. Moreover, the process is to be carried out in a relatively wet environment.

36.  GAS TREATING
• THE OTHERWISE NOT USEFUL FUEL GAS AND H2S STREAM GENERATED FROM THE C2
SEPARATOR HAS SIGNIFICANT AMOUNT OF SULFUR.
• IN THE GAS TREATING PROCESS, H2S IS SUCCESSFULLY TRANSFORMED INTO SULFUR ALONG
WITH THE GENERATION OF FUEL GAS (FIGURE).
• EVENTUALLY, IN MANY REFINERIES, SOME FUEL GAS IS USED FOR FURNACE APPLICATIONS
WITHIN THE REFINERY ALONG WITH FUEL OIL (ANOTHER REFINERY PRODUCT GENERATED FROM
THE FUEL OIL POOL) IN THE FURNACE ASSOCIATED TO THE CDU.

37. G T
FUEL GAS SENDS TO STORAGE TANK
TO STORE
SULPHER SENDS TO STORAGE TANK
TO STORE
FUEL GAS + H2S (FROM C2 – SEP.)
TO RECOVER SULFUR AND PRODUCE FUEL GAS
GASEOUS FCC PRODUCT ( FROM FCC UNIT) FOR
SULFUR RECOVERY AND FUEL GAS PRODUCTION
Operating Conditions: Gas treaters may operate at temperatures ranging from 150 psig
(low pressure units) to 3000 psig (high pressure units).

38. • TO FACILITATE STREAM SPLITTING, VARIOUS STREAM SPLITTERS ARE USED IN THE REFINERY
CONFIGURATION.
SPLITTERS ARE DIFFERENT TYES THEY ARE :-
• NAPHTHA SPLITTER
• BUTANE SPLITTER
• KEROSENE SPLITTER
• LVGO SPLITTER
 STREAM SPLITTERS

39.  NAPHTHA SPLITTER
• THE NAPHTHA SPLITTER UNIT CONSISTING OF A SERIES OF DISTILLATION COLUMNS ENABLES
THE SUCCESSFUL SEPARATION OF LIGHT NAPHTHA AND HEAVY NAPHTHA FROM THE
CONSOLIDATED NAPHTHA STREAM OBTAINED FROM SEVERAL SUB-UNITS OF THE REFINERY
COMPLEX (FIGURE).
• THE NAPHTHA SPLITTER IS REGARDED AS A PHYSICAL PROCESS FOR MODELING PURPOSES.
N - SDESULFURIZED LN+HN ( FROM SEP.-C4 )
TO SPLIT LIGHT NAPHTHA (LN)
FROM HEAVY NAPHTHA (HN)
DESULFURIZED LN (SENDS TO GASOLINE POOL)
TO PREPARE PREMIUM AND REGULAR GASOLINE PRODUCTS
DESULFURIZED HN (SENDS TO CATALYTIC REFORMER )
TO CRACK HEAVY NAPHTHA INTO LIGHTER PRODUCTS
Operating Conditions: The pressure is to be maintained between 1 kg/cm2 to 4.5 kg/cm2.
The operating temperature range should be 167 – 250oC

40. • BUTANE SPLITTER SPLITS THE N-BUTANE STREAM INTO BUTANES ENTERING LPG POOL,
GASOLINE POOL AND ISOMERIZATION UNIT (FIGURE).
• UNLIKE NAPHTHA SPLITTER, THESE TWO SPLITTERS FACILITATE STREAM DISTRIBUTION AND DO
NOT HAVE ANY SEPARATION PROCESSES BUILT WITHIN THEM.
C4S (NORMAL AND ISOBUTANE MIXTURE) FROM
C3 - SEPERATOR TO BY-PASS THE STREAM
NORMAL BUTANE (SENDS TO LPG POOL UNIT)
TO PRODUCE C3 LPG AND C4 LPG PRODUCTSBUTANE
SPLITTER
NORMAL BUTANE (SENDS TO GASOLINE POOL)
TO PRODUCE PREMIUM AND REGULAR GASOLINE PRODUCTS
NORMAL BUTANE (SENDS TO ISOMER.)
TO CONVERT NC4 INTO IC4

41. • SIMILARLY, A KEROSENE SPLITTER IS USED TO SPLIT KEROSENE BETWEEN THE KEROSENE
PRODUCT AND THE STREAM THAT IS SENT TO THE GAS OIL POOL (FIGURE).
KEROSENE
SPLITTER
DESULFURIZED KEROSENE (FROM
LGO-HDS ) SPLITTING KEROSENE FOR
BLENDING POOL AND PRODUCT
DESULFURIZED KEROSENE PRODUCT
(SENDS TO STORAGE TANK)
DESULFURIZED KEROSENE (SENDS TO GOP) TO BLEND
AND PRODUCE AUTO DIESEL AND HEATING OIL

42.  LVGO SPLITTER
DESULFURIZED LVGO (SENDS TO GAS OIL POOL)
TO GENERATE AUTO DIESEL AND HEATING OIL PRODUCTS
DESULFURIZED LVGO (SENDS TO FUEL OIL POOL)
TO GENERATE HARING DIESEL, HEAVY FUEL OIL AND BUNKER OIL
LV - SP
DESULFURIZED LVGO (FROM HGO - HDS)
TO BY-PASS THE STREAM

43.  REFORMER
• AS SHOWN IN (FIGURE), HEAVY NAPHTHA WHICH DOES NOT HAVE HIGH OCTANE NUMBER IS
SUBJECTED TO REFORMING IN THE REFORMER UNIT TO OBTAIN REFORMATE PRODUCT (WITH
HIGH OCTANE NUMBER), LIGHT ENDS AND REFORMER GAS (HYDROGEN).
• THEREBY, THE UNIT PRODUCES HIGH OCTANE NUMBER PRODUCT THAT IS ESSENTIAL TO
PRODUCE PREMIUM GRADE GASOLINE AS ONE OF THE MAJOR REFINERY PRODUCTS.
• A REFORMER IS REGARDED AS A COMBINATION OF CHEMICAL AND PHYSICAL PROCESSES.

44. CATALYTIC
REFORMER
REFORMER OFF-GAS (SENDS TO N-HDS)
H2 PURIFICATION BY LOSS OF LIGHT ENDS IN N-HDS PROCESS
CRACKED LIGHT ENDS(SENDS TO C3-SEP.)
TO SEPARATE C3’S FROM BUTANES
REFORMATE (SENDS TO GASOLINE POOL) TO
PREPARE PREMIUM AND REGULAR GASOLINE PRODUCT
DESULFURIZED HN (FROM NAPHTHA SPLITTER )
TO CRACK HEAVY NAPHTHA INTO LIGHTER PRODUCTS
Operating Conditions : The initial liquid feed should be pumped at a reaction pressure
of 5 – 45 atm, and the preheated feed mixture should be heated to a reaction temperature of 495 –
520oC.

45.  ALKYLATION AND ISOMERIZATION
• THE UNSATURATED LIGHT ENDS GENERATED FROM THE FCC PROCESS ARE STABILIZED BY
ALKYLATION PROCESS USING IC4 GENERATED FROM THE C4 SEPARATOR.
• THE PROCESS YIELDS ALKYLATE PRODUCT WHICH HAS HIGHER OCTANE NUMBER THAN THE
FEED STREAMS (FIGURE).
ALK
C3S SENDS TO LPG GAS POOL
TO PRODUCE C3 LPG PRODUCTS
C4S SENDS TO LPG GAS POOL
TO PRODUCE C4 LPG PRODUCTS
ALKYLATE SENDS TO GASOLINE POOL TO PRODUCE
PREMIUM AND REGULAR GASOLINE PRODUCTS
UNSATURATED LIGHT ENDS ( FROM F.C.C UNIT )
CONVERSION OF C3-4 TO ALKYLATES
ISOBUTANE (FROM ISOMER.) TO REACTANT
UNSATURATES WITH ISOBUTANE AND PRODUCE ALKYLATES

46. • AS ISOBUTENE GENERATED FROM THE SEPARATOR IS ENOUGH TO MEET THE DEMAND IN THE
ALKYLATION UNIT, ISOMERIZATION REACTION IS CARRIED OUT IN THE ISOMERIZATION UNIT
TO YIELD THE DESIRED MAKE UP IC4 (FIGURE).
ISOMERIZATIO
N
ISOBUTANE (SENDS TO ALKYLATION UNIT) TO REACTANT
UNSATURATES WITH ISOBUTANE AND PRODUCE ALKYLATES
NORMAL BUTANE (FROM BUTANE-SPLLI.)
TO CONVERT NC4 INTO IC4

47.  BLENDING POOLS
• ALL REFINERIES NEED TO MEET TIGHT PRODUCT SPECIFICATIONS IN THE FORM OF ASTM
TEMPERATURES, VISCOSITIES, OCTANE NUMBERS, FLASH POINT AND POUR POINT.
• TO ACHIEVE DESIRED PRODUCTS WITH MINIMUM SPECIFICATIONS OF THESE IMPORTANT
PARAMETERS, BLENDING IS CARRIED OUT.

48. • THERE ARE FOUR BLENDING POOLS IN A TYPICAL REFINERY. WHILE THE LPG POOL ALLOWS
BLENDING OF SATURATED C3S AND C4S TO GENERATE C3 LPG AND C4 LPG, WHICH DO NOT
ALLOW MUCH BLENDING OF THE FEED STREAMS WITH ONE ANOTHER (FIGURE).
C3 LPG PRODUCT SENDS TO
STORAGE
C4 LPG PRODUCT SENDS TO
STORAGE
C3S (FROM ALKYLATION)
TO PRODUCE C3 LPG PRODUCTS
C4S (FROM ALKYLATION)
TO PRODUCE C4 LPG PRODUCTS
ORMAL BUTANE (FROM BUTANE SPLITTER )
TO PRODUCE C3 AND C4 LPG PRODUCTS
C3S (FROM C2 - SEPERATOR ) TO RECOVER
SULFUR AND PRODUCE FUEL GAS
LPG – POOL UNIT
STORAGE
TANK

49. • THE MOST IMPORTANT BLENDING POOL IN THE REFINERY COMPLEX IS THE GASOLINE POOL
WHERE IN BOTH PREMIUM AND REGULAR GASOLINE PRODUCTS ARE PREPARED BY BLENDING
APPROPRIATE AMOUNTS OF N-BUTANE, REFORMATE, LIGHT NAPHTHA, ALKYLATE AND LIGHT
CRACKED NAPHTHA (FIGURE).
GASOLINE
POOL
LIGHT CRACKED NAPHTHA (F.C.C. UNIT)
TO GENERATE PREMIUM AND REGULAR GASOLINE
HEAVY CRACKED NAPHTHA (FROM F.C.C. UNIT)
TO GENERATE PREMIUM AND REGULAR GASOLINE
REFORMATE (FROM CAT. - CRACK) TO PREPARE
PREMIUM AND REGULAR GASOLINE PRODUCTS
NORMAL BUTANE (FROM BUTAIN. – SPL.) TO PRODUCE
PREMIUM AND REGULAR GASOLINE PRODUCTS
DESULFURIZED LN (FROM NAPHTHA SPLLITER)
TO PREPARE PREMIUM AND REGULAR GASOLINE PRODUCTS
STORAGE
TANK
PREMIUM GASOLINE
REGULAR GASOLINE
ALKYLATE (FROM ALKYLATION) TO PRODUCE
PREMIUM AND REGULAR GASOLINE PRODUCTS

50. • THE GASOIL POOL PRODUCES AUTOMOTIVE DIESEL AND HEATING OIL FROM KEROSENE (FROM
CDU), LGO, LVGO AND SLURRY (FIGURE).
GAS OIL POOL
AUTO DIESEL
STORAGE
TANK
HEATING OIL
CLE OIL (FROM F.C.C. UNIT) TO GENERATE
UTO DIESEL AND HEATING OIL PRODUCTS
DESULFURIZED LVGO (FROM LVGO SLITTER)
TO GENERATE AUTO DIESEL AND HEATING OIL PRODUCTS
DESULFURIZED LGO (FROM LGO - HDS ) TO GENERATE
AUTO DIESEL AND HEATING OIL PRODUCTS
DESULFURIZED KEROSENE (FROM KEROSENE SPLITTER) TO BLEND
AND PRODUCE AUTO DIESEL AND HEATING OIL

51. • IN THE FUEL OIL POOL HARING DIESEL, HEAVY FUEL OIL AND BUNKER OIL ARE PRODUCED FROM
LVGO, SLURRY AND CRACKED RESIDUE (FIGURE).
FUEL OIL POOL
STORAGE
TANK
CRACKED RESIDUE (FROM
THERMAL CRACKING)
SLURRY (SENDS TO FUEL OIL POOL) TO GENERATE
HARING DIESEL, HEAVY FUEL OIL AND BUNKER OIL
HARING DIESEL
HEAVY FUEL OIL
BUNKER OIL
DESULFURIZED LVGO (FROM LVGO - SPLITTER)
TO GENERATE HARING DIESEL, HEAVY FUEL OIL AND BUNKER OIL

52. Total flow chart

53.  HOW TO REMEMBER THE REFINERY PROCESS FLOW SHEET IN A SIMPLE WAY?
ANS.) DIVED THE REFINERY INTO FOUR BLOCKS NAMELY THE SEPARATION BLOCK, THE
TREATING BLOCK, THE REACTIVE TRANSFORMATION BLOCK AND THE REST BLOCK.
REFINERY
SEPARATION BLOCK
TREATING BLOCK
REACTIVE TRANSFORMATION
BLOCK REST BLOCK
C.D.U
V.D.U
NAPHTHA SPLITTERS
C4, C3 AND OTHER
SEPARATORS
ALL HYDROTREATERS
ALL GAS TREATING UNIT
 THERMAL CRACKER
 ALKYLATOR
 ISOMERIZER AND
 REFORMER
 BLENDING UNITS
 KEROSENE SPLITTER
 N-BUTANE SPLITTER AN
 OTHER UNITS