CRUDE OIL REFINING PROCESS

T.Mahendra Reddy

CONTENTS

• INTRODUCTION

• PROPERTIES

• TYPES OF PROCESS

• REFINING OPERATIONS

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

INTRODUCTION

-REFINING IS CARRIED OUT IN THREE MAIN STEPS.

1. SEPARATION

2. CONVERSATION

3. PURIFICATION

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.

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.

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.

TYPES OF PROCESSES

CRUDE OIL REFINING PROCESS ARE CLASSIFIED INTO TWO DIFFERENT TYPES,

THEY ARE

A. PHYSICAL PROCESS AND

B. CHEMICAL PROCESS

A) PHYSICAL PROCESS

THERE ARE DIFFERENT TYPES OF PHYSICAL PROCESS ARE PRESENT

• DISTILLATION

• SOLVENT EXTRACTION

• PROPANE DEASPHALTING

• SOLVENT DE WAXING

• BLENDING

B) CHEMICAL PROCESSCHEMICAL 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

REFINING OPERATIONS

---THERE ARE TWO TYPES OF OPERATIONS ARE PRESENT IN REFINING PROCESS

THEY ARE

• PRIMARY PROCESSING UNITS

• SECONDARY PROCESSING UNITS

-PRIMARY PROCESSING UNITS

PRIMARY PROCESSING UNITS ARE CLASSIFIED INTO TWO TYPES THEY

ARE

1. CRUDE DISTILLATION UNIT (CDU)

2. VACUUM DISTILLATION UNIT (VDU)

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.

C.D.UCRUDE 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)

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.

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.

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.

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 EFFICIENCIES ARE DESIRED, THREE STAGE UNITS ARE DEPLOYED.

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.

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.

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

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 AROUND 380 – 420OC.

ATMOSPHERIC

RESIDUE

LIGHT VACUUM GAS OIL (LVGO)

HEAVY VACUUM GAS OIL (HVGO)

VACUUM RESIDUE

V.D.U

H-HDS

SENDS TO T C

--SECONDARY PROCESSING UNITS1. 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.

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

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 PRESSURE MUST BE MAINTAINED.

T.C UNIT

VACUUMRESIDUE

GAS +NAPHTHA(SENDS

TON – HDS)

CRACKEDGAS OIL(SENDS

TOL - HDS

CRACKEDRESIDUE

SENDS TOFUEL OIL POOL

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.

• 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 INTERMEDIATEPRODUCTS) 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( FROM L – HDS )

GAS +NAPHTHA( FROM THERMAL.

CRAC.)

DESULFURIZED GAS + NAPHTHA FORNAPHTHA STABILIZATION (TO SATURATE UNSATURATES) FROM

HGO - HDS

REFORMER OFF-GAS (FROM CATALYTIC REFORMER)H2 PURIFICATION BY LOSS OF LIGHT ENDS IN N-HDS PROCESS

• 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 - HDSKEROSENE

(FROM C.D.U)

LIGHT GAS OIL ( FROM C.D.U )

DESULFURIZED GAS + NAPHTHANAPHTHA STABILIZATION (TO SATURATE & UNSATURATES)

SENDS TO N-HDS

HYDROGENFROM NAPHTHAHYDROTREATERS

DESULFURIZED KEROSENE (SENDS TO KEROSENE SPLITTER ) SPLITTING

KEROSENE FOR BLENDING POOL AND PRODUCT

DESULFURIZED LGO (SENDS TO GAS OILPOOL ) TO GENERATE AUTO DIESEL

AND HEATING OIL PRODUCTS

• 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).

HEAVYGASOIL

- HDS

LIGHT VACCUME GAS OILFROM V.D.U

HEAVY VACCUME GAS OILFROM V.D.U

HYDROGENFROM NAPHTHAHYDROTREATERS

DESULFURIZED GAS + NAPHTHA FORNAPHTHA 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

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 NaphthaSplitter ) To split Light Naphtha (LN)

from Heavy Naphtha (HN)

Desulfurized Gas + Naphtha ( FROM N- HDS )

Separation of gas and Naphtha (LN + HN)

• ON THE OTHER HAND, C3 SEPARATOR SEPARATES BUTANES (BOTH ISO AND BUTANES) FROM THE GAS FRACTION (FIGURE).

SEPERATOR – C3SATURATED 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 TON-BUTANE SPLITTER TO BY-PASS THE STREAM

CRACKED LIGHT ENDS(FROM CATI. CRACK)TO SEPARATE C3’S FROM BUTANES

• 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

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.

F.C.C

GASEOUS FCC PRODUCT ( SENDS TO GAS TREATINGUNIT) 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) TOGENERATE AUTO DIESEL AND HEATING OIL PRODUCTS

SLURRY (SENDS TO FUEL OIL POOL) TO GENERATEHARING 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.

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.

G T

FUEL GAS SENDS TO STORAGE TANKTO STORE

SULPHER SENDS TO STORAGE TANKTO STORE

FUEL GAS + H2S (FROM C2 – SEP.)TO RECOVER SULFUR AND PRODUCE FUEL GAS

GASEOUS FCC PRODUCT ( FROM FCC UNIT) FORSULFUR 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).

• 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

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

• 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) FROMC3 - 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

• 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).

KEROSENESPLITTER

DESULFURIZED KEROSENE (FROMLGO-HDS ) SPLITTING KEROSENE FOR

BLENDING POOL AND PRODUCT

DESULFURIZED KEROSENE PRODUCT(SENDS TO STORAGE TANK)

DESULFURIZED KEROSENE (SENDS TO GOP) TO BLENDAND PRODUCE AUTO DIESEL AND HEATING OIL

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 - SPDESULFURIZED LVGO (FROM HGO - HDS)TO BY-PASS THE STREAM

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.

CATALYTICREFORMER

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) TOPREPARE PREMIUM AND REGULAR GASOLINE PRODUCTS

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.

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 POOLTO PRODUCE C3 LPG PRODUCTS

C4S SENDS TO LPG GAS POOLTO PRODUCE C4 LPG PRODUCTS

ALKYLATE SENDS TO GASOLINE POOL TO PRODUCEPREMIUM AND REGULAR GASOLINE PRODUCTS

UNSATURATED LIGHT ENDS ( FROM F.C.C UNIT )CONVERSION OF C3-4 TO ALKYLATES

ISOBUTANE (FROM ISOMER.) TO REACTANTUNSATURATES WITH ISOBUTANE AND PRODUCE ALKYLATES

• 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).

ISOMERIZATION

ISOBUTANE (SENDS TO ALKYLATION UNIT) TO REACTANTUNSATURATES WITH ISOBUTANE AND PRODUCE ALKYLATES

NORMAL BUTANE (FROM BUTANE-SPLLI.)TO CONVERT NC4 INTO IC4

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.

• 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

NORMAL BUTANE (FROM BUTANE SPLITTER )TO PRODUCE C3 AND C4 LPG PRODUCTS

C3S (FROM C2 - SEPERATOR ) TO RECOVERSULFUR AND PRODUCE FUEL GAS

LPG – POOL UNITSTORAGE

TANK

• 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).

GASOLINEPOOL

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 PREPAREPREMIUM AND REGULAR GASOLINE PRODUCTS

NORMAL BUTANE (FROM BUTAIN. – SPL.) TO PRODUCEPREMIUM AND REGULAR GASOLINE PRODUCTS

DESULFURIZED LN (FROM NAPHTHA SPLLITER)TO PREPARE PREMIUM AND REGULAR GASOLINE PRODUCTS

STORAGETANK

PREMIUM GASOLINE

REGULAR GASOLINE

ALKYLATE (FROM ALKYLATION) TO PRODUCEPREMIUM AND REGULAR GASOLINE PRODUCTS

• THE GASOIL POOL PRODUCES AUTOMOTIVE DIESEL AND HEATING OIL FROM KEROSENE (FROM CDU), LGO, LVGO AND SLURRY (FIGURE).

GAS OIL POOL

AUTO DIESEL

STORAGETANK

HEATING OILCYCLE OIL (FROM F.C.C. UNIT) TO GENERATEAUTO DIESEL AND HEATING OIL PRODUCTS

DESULFURIZED LVGO (FROM LVGO SLITTER)TO GENERATE AUTO DIESEL AND HEATING OIL PRODUCTS

DESULFURIZED LGO (FROM LGO - HDS ) TO GENERATEAUTO DIESEL AND HEATING OIL PRODUCTS

DESULFURIZED KEROSENE (FROM KEROSENE SPLITTER) TO BLENDAND PRODUCE AUTO DIESEL AND HEATING OIL

• 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

STORAGETANK

CRACKED RESIDUE (FROM THERMAL

CRACKING)

SLURRY (SENDS TO FUEL OIL POOL) TO GENERATEHARING 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

Total flow chart

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 BLOCKREACTIVE TRANSFORMATION

BLOCK REST BLOCKC.D.U

V.D.U

NAPHTHA SPLITTERS

C4, C3 AND OTHERSEPARATORS

ALL HYDROTREATERS

ALL GAS TREATING UNIT THERMAL CRACKER

ALKYLATOR

ISOMERIZER AND

REFORMER

BLENDING UNITS

KEROSENE SPLITTER

N-BUTANE SPLITTER AND

OTHER UNITS

THANK YO

U

T.Mah

endra

Reddy