CHAPTER 3

OIL REFINERY PROCESSES

OUTLINE

1. Introduction
2. Physical Processes
3. Thermal Processes
4. Catalytic Processes
5. Conversion of Heavy Residues
6. Treatment of Refinery Gas Streams
INTRODUCTION

 Oil refining is a key activity in the Chemical

Process Industries.
 Over 600 refineries worldwide have a total
annual capacity of more than 3500 x 106 tones.
 Goal of oil refining is twofold:
i. Production of fuels for transportation, power
generation and heating
ii. Production of raw materials for the CPI.
Crude Oil
Crude oil is a non-uniform material.
The composition depends on its location.
Figure 2.11 shows the ratio of C/H in some of chemical compounds
The majority of crude oil is alkanes, cycloalkanes (naphthenes), aromatics,
polycyclic aromatics, Sulfur - containing compounds, etc.
Example: Gasoline: branched alkanes
Diesel: linear alkanes
Heavier crude contains more polycyclic aromatics lead to
carboneceous deposits called “coke”
Some crudes contain a lot of sulfur, which leads to
additional processing considerations.
Overview

 After desalting and dehydration, crude is separated

into fractions by distillation.
 The distilled fractions can not be used directly.
 The reason for such a complex set of processes is
1- the difference between the crude oil properties
and the needs of the market.
2- environmental legislation demands cleaner products
3- is the major drive for process improvement and
development of novel processes.
Refining operations
Petroleum refining processes and operations can be separated into five
basic areas:
1. Fractionation (distillation) is the separation of crude oil in atmospheric and
vacuum distillation towers into groups of hydrocarbon compounds of
differing boiling-point ranges called "fractions" or "cuts."
2. Conversion Processes change the size and/or structure of hydrocarbon
molecules. These processes include: :
• Decomposition (dividing) by thermal and catalytic cracking;
• Unification (combining) through alkylation and polymerization; and
• Alteration (rearranging) with isomerization and catalytic reforming.
3. Treatment Processes to prepare hydrocarbon streams for additional
processing and to prepare finished products. Treatment may include
removal or separation of aromatics and naphthenes, impurities and
undesirable contaminants. Treatment may involve chemical or physical
separation e.g. dissolving, absorption, or precipitation using a variety and
combination of processes including desalting, drying, hydrodesulfurizing,
solvent refining, sweetening, solvent extraction, and solvent dewaxing.
Refining operations

4. Formulating and Blending is the process of mixing

and combining hydrocarbon fractions, additives, and
other components to produce finished products with
specific performance properties.
5. Other Refining Operations include:
• light-ends recovery;
• sour-water stripping;
• solid waste, process-water and wastewater treatment;
• cooling, storage and handling and product movement;
• hydrogen production;
• acid and tail-gas treatment;
• and sulfur recovery.
Refining operations

 Auxiliary Operations and Facilities include:

• light steam and power generation;
• process and fire water systems;
• flares and relief systems;
• furnaces and heaters;
• pumps and valves;
• supply of steam, air, nitrogen, and other plant gases;
• alarms and sensors;
• noise and pollution controls;
• sampling, testing, and inspecting and laboratory;
• control room;
• maintenance; and
• administrative facilities.
Flow scheme of a modern refinery
Physical and chemical processes
Chemical
Physical
Thermal Catalytic
Desalting/dehydrating Visbreaking Hydrotreating
Distillation Delayed coking Catalytic reforming
Solvent extraction Flexicoking Catalytic cracking
Propane deasphalting Hydrocracking
Solvent dewaxing Catalytic dewaxing
Blending Alkylation
Polymerization
Isomerization
Physical Processes
 Desalting/dehydration
 Crude distillation
 Propane deasphalting
 Solvent extraction
 Solvent dewaxing
 Blending
Desalting/Dehydration1/2
 Process Objective:
 Remove the contaminants in crude oil (often contains water, inorganic
salts, suspended solids, and water-soluble trace metals) so as to reduce
corrosion, plugging, and fouling of equipment and to prevent poisoning
catalysts in processing units.
 Primary Process Technique:
 The two most typical methods of crude-oil desalting are chemical and
electrostatic separation, and both use hot water as the extraction agent.
 Process steps:
 The crude oil feedstock is heated to 65-180°C to reduce viscosity and
surface tension for easier mixing and separation of the water
 In chemical desalting, water and chemical surfactant (demulsifiers) are
added to the crude, which is heated so that salts and other impurities
dissolve or attach to the water, then held in a tank to settle out.
 Electrical desalting is the application of high-voltage electrostatic charges
to concentrate suspended water globules in the bottom of the settling tank.
Surfactants are added only when the crude has a large amount of
suspended solids.
Desalting/Dehydration2/2
 The crude oil feedstock is heated to 65-180°C to reduce viscosity and
surface tension for easier mixing and separation of the water. The
temperature is limited by the vapor pressure of the crude-oil
feedstock.
 In both methods other chemicals may be added. Ammonia is often
used to reduce corrosion. Caustic or acid may be added to adjust the
pH of the water wash.
Crude Distillation
 Step 1 in the refining process is the separation of
crude oil into various fractions or straight-run cuts
by distillation in
1- atmospheric and
2- vacuum towers.

The main fractions or "cuts" obtained have specific

boiling-point ranges and can be classified in order
of decreasing volatility into gases, light distillates,
middle distillates, gas oils, and residuum.
Fraction of Petroleum

b.p. <20oC
 Crude Distillation Unit: Atmospheric distillation1/2

 Process Objective:
 To distill and separate valuable distillates (naphtha, kerosene,diesel) and
atmospheric gas oil (AGO) from the crude feedstock.
 Primary Process Technique:
 Complex distillation
 Process steps:
 Preheat the desalted crude feed by utilizing recovered heat from the product
streams
 The feedstock then flows to a direct-fired crude charge heater then into
the vertical distillation column just above the bottom, at pressures
slightly above atmospheric and at temperatures ranging from 340-370°C
(above these temperatures undesirable thermal cracking may occur).
 Crude Distillation Unit: Atmospheric distillation2/2

As the hot vapor rises in the tower, its temperature is reduced.

Heavy fuel oil or asphalt residue is taken from the bottom.

At successively higher points on the tower, the various major

products including lubricating oil, heating oil, kerosene, gasoline,
and uncondensed gases (which condense at lower temperatures) are
drawn off.

Product draws are on the top, sides, and bottom

 Utilize pump around cooling loops to create internal liquid reflux

Simple Crude Distillation Unit
 Crude Distillation Unit: Vacuum Distillation2/2
 Process Objective:
 To further distill the residuum from
the atmospheric tower without
thermal cracking,
 A typical first-phase vacuum tower
may produce gas oils, lubricating-oil
base stocks, and heavy residual for
propane deasphalting
 Primary Process Technique:
 Reduced pressure is required.
 The process takes place in one or more
vacuum distillation towers
 Process steps:
 Preheat residuum feed in a fired furnace
 Introduce the feed to a tower at reduced pressure
evacuated by a vacuum pumps or ejectors
Modern crude distillation
 Propane Deasphalting
 Process Objective: Coke-forming tendencies of heavier
distillation products are reduced by removal
of asphaltenic materials by solvent extraction.
 Primary Process Technique: Liquid propane is a good solvent
(butane and pentane are also commonly used).
Deasphalting is based on solubility of
hydrocarbons in propane
 Process steps: Vacuum residue is fed to a countercurrent
deasphalting tower.
Alkanes dissolve in propane whereas asphaltenic
materials (aromatic compounds), ‘coke-
precursors’ do not.
Asphalt is sent for thermal processing.
Propane Deasphalting
Solvent Extraction and Dewaxing
 Solvent treating is a widely used method of refining
1- lubricating oils 2- a host of other refinery stocks.
 Since distillation (fractionation) separates petroleum products into
groups only by their boiling-point ranges, impurities may remain.
These include organic compounds containing sulfur, nitrogen, and
oxygen; inorganic salts and dissolved metals; and soluble salts
that were present in the crude feedstock.
 In addition, kerosene and distillates may have trace amounts of
aromatics and naphthenes, and lubricating oil base-stocks may
contain wax.
 Solvent refining processes including solvent extraction and
solvent dewaxing usually remove these undesirables at
intermediate refining stages or just before sending the product to
storage.
Solvent Extraction 1/3
 Process Objective:
 to prevent corrosion, protect catalyst in subsequent processes, and improve
finished products by removing unsaturated, aromatic hydrocarbons from
lubricant and grease stocks.
 Primary Process Technique:
 The solvent extraction process separates aromatics, naphthenes, and
impurities from the product stream by dissolving or precipitation.
 The most widely used extraction solvents are phenol and furfural.
 Process steps:
 In one type of process, the feedstock is washed with furfural in which the
substances to be removed are more soluble than in the desired resultant
product.
 The solvent is separated from the product stream by heating, evaporation,
or fractionation, and residual trace amounts are subsequently removed
from the raffinate by steam stripping or vacuum flashing.
 The solvent is regenerated for reused in the process.
Solvent Extraction 2/3

Aromatic Solvent Extraction Unit

Solvent Extraction 3/3
 In another process, selected solvents are added to cause
impurities to precipitate out of the product.
 In the adsorption process, highly porous solid materials
collect liquid molecules on their surfaces

 Electric precipitation may be used for separation of

inorganic compounds.
 The most widely used extraction solvents are phenol,
furfural, and cresylic acid.
 Other solvents less frequently used are liquid sulfur dioxide,
nitrobenzene, and 2,2' dichloroethyl ether.
 The selection of specific processes and chemical agents
depends on the nature of the feedstock being treated, the
contaminants present, and the finished product requirements.
 Solvent Dewaxing
 Process Objective:
 Solvent dewaxing is used to remove wax from either distillate or
residual base stock at any stage in the refining process.
 Primary Process Technique:
 Usually two solvents are used: toluene, which dissolves the oil and
maintains fluidity at low temperatures, and methyl ethyl ketone
(MEK), which dissolves little wax at low temperatures and acts as a
wax precipitating agent. Other solvents sometimes used include
benzene, methyl isobutyl ketone, propane, petroleum naphtha,
ethylene dichloride, methylene chloride, and liquid sulfur dioxide.
 Process steps:
There are several processes in use for solvent dewaxing, but all have
the same general steps, which are:
 Mixing the feedstock with a solvent;
 Precipitating the wax from the mixture by chilling;
 Recovering the solvent from the wax and dewaxed oil for recycling
by distillation and steam stripping.
Solvent Dewaxing Unit
Blending
 Process Objective:
 Blending is the physical mixture of a number of different liquid
hydrocarbons to produce a finished product with certain desired
characteristics.
 Primary Process Technique:
 Products can be blended in-line through a manifold system, or
batch blended in tanks and vessels.
 Additives including octane enhancers, anti-oxidants, anti-knock
agents, gum and rust inhibitors, detergents, etc. are added during
and/or after blending to provide specific properties not inherent
in hydrocarbons.
 Process steps:
 In-line blending of gasoline, distillates, jet fuel, and kerosene is
accomplished by injecting proportionate amounts of each
component into the main stream where turbulence promotes
thorough mixing.
THERMAL PROCESSES
 When a hydrocarbon is heated to a sufficiently high
temperature thermal cracking occurs. This is sometimes
referred to as pyrolysis (especially when coal is the
feedstock).
 When steam is used for heating it is called steam
cracking.
 There are two thermal processes used in refineries.
 Visbreaking
 Delayed coking
Visbreaking 1/2
Visbreaking is a mild form of thermal cracking to lower
the viscosity
 Process Objective:
 Lowers the viscosity of heavy crude-oil residues without affecting the
boiling point range.
 Reduce the pour point of waxy residues and reduce the viscosity of
residues used for blending with lighter fuel oils.
 Primary Process Technique:
Visbreaking is a mild form of thermal cracking for which oil is
heated to a sufficiently high temperature
 Process steps:
 Residuum from the atmospheric distillation tower is heated (425-510ºC) at
atmospheric pressure and mildly cracked in a heater.
 It is then quenched with cool gas oil to control over-cracking, and flashed
in a distillation tower.
Visbreaking 2/2

 Alternatively, vacuum residue can be cracked. The severity of the

visbreaking depends upon temperature and reaction time (1-8 min).
 Usually < 10 wt% of gasoline and lighter products are produced.
Delayed Coking Process 1/3
 Coking is a severe method of thermal cracking used to upgrade heavy
residuals into lighter products or distillates.
 Coking produces straight-run gasoline (Coker naphtha) and various middle-
distillate fractions used as catalytic cracking feedstock.
 The process completely reduces hydrogen so that the residue is a form of
carbon called "coke."
 Three typical types of coke are obtained (sponge coke, honeycomb coke, and
needle coke) depending upon the reaction mechanism, time, temperature, and
the crude feedstock.
 In delayed coking the heated charge (typically residuum from atmospheric
distillation towers) is transferred to large coke drums which provide the long
residence time needed to allow the cracking reactions to proceed to
completion.
Delayed Coking Process 2/3
 Process Objective:
 To convert low value residue to valuable products such as naphtha
and diesel and gas oil (ie used to upgrade heavy residuals into
lighter products or distillates ).
 Primary Process Technique:
 The process completely reduces hydrogen so that the residue is a
form of carbon called "coke." in a semi batch process.
 Delayed Coking Process 3/3
 Process steps:
 In delayed coking, the heated residuum from atmospheric towers is
transferred into large coke drums which provide the long residence
time needed to allow the cracking reactions to proceed to completion.
 The bottoms of the fractionator are fed to coker drums via a furnace
where the hot material (440°-500°C) is held approximately 24 hours
(delayed) at pressures of 2-5 bar, until it cracks into lighter products.
 Vapors from the drums are returned to a fractionator where gas,
naphtha, and gas oils are separated out. The heavier hydrocarbons
produced in the fractionator are recycled through the furnace.
 After the coke reaches a predetermined level in one drum, the flow is
diverted to another drum in order to maintain continuous operation.
 To strip out uncracked hydrocarbons, the full drum is steamed, cooled
by water injection, and de-coked by mechanical or hydraulic methods.
 The coke is mechanically removed by an auger rising from the bottom
of the drum. Hydraulic decoking consists of fracturing the coke bed
with high-pressure water ejected from a rotating cutter.
Delayed Coking/ Process Schematic
CATALYTIC PROCESSES

There are several types of catalytic processes used in

refineries.

Fluid Catalytic Cracking (FCC)

Hydrotreating
Hydrocracking
Catalytic Reforming
Alkylation
 Fluid Catalytic Cracking1/3
 Process Objective:
 To convert low value gasoil to valuable products (gasoline, naphtha and diesel)
 Primary Process Technique:
 Catalytic cracking increases H/C ratio by carbon rejection
 Thermal cracking occurs on the surface of the catalyst in a continuous process.
Process steps:
 Gas oil feed and catalyst are dispersed into the bottom of the riser using steam
 Oil is cracked in the presence of a finely divided catalyst, which is maintained in an
aerated or fluidized state by the oil vapours.
 Preheated feed is mixed with hot, regenerated catalyst in the riser and combined
with a recycle stream, vapourized, and raised to reactor temperature (485-540°C) by
the hot catalyst
 As the mixture travels up the riser, the charge is cracked at 0.7-2 bar.
 The fluid catalyst is continuously circulated between the reactor and the regenerator
using air, oil vapors, and steam as the conveying media.
Fluid Catalytic Cracking2/3
 Disengaging drum separates spent catalyst from product vapors
 Steam strips residue hydrocarbons from spent catalyst
 Spent catalyst flows through the catalyst stripper to the regenerator,
where most of the coke deposits will burn off at the bottom where
preheated air and spent catalyst are mixed.
 Fresh catalyst is added and worn-out catalyst removed to optimize
the cracking process.
 Regenerated catalyst enters bottom of riser-reactor
Fluid Catalytic Cracking3/3
 Fluidic Catalytic Cracking-Process Schematic

Products to Fractionation

Disengaging
Vessel

Flue Gas
Stripping (CO2, CO, SOx)
Steam

Stripper
Riser-Reactor Regenerator

Air

Gas Oil Feed

Dispersant Steam
Fluid Catalytic Cracking- Full Process
 Hydrotreating Processes1/2

 Catalytic hydrotreating is a hydrogenation process used to remove

about 90% of contaminants such as nitrogen, sulfur, oxygen, and
metals from liquid petroleum fractions. Such as Remove NH3

 Also, catalytic hydrotreating converts olefins and aromatics to

saturated compounds, such as:

 Typically, hydrotreating is done prior to processes such as catalytic

reforming so that the catalyst is not contaminated by untreated
feedstock.
 Hydrotreating Processes2/2
 Process Objective:
 To remove contaminants (sulfur, nitrogen, metals) and saturate olefins and aromatics
to produce a clean product for further processing or finished product sales.
 Primary Process Technique:
 Hydrogenation occurs in a fixed catalyst bed to improve H/C ratios and to remove
sulfur, nitrogen, and metals.
 Process steps:
 Feed is preheated using the reactor effluent
 Hydrogen is combined with the feed and heated to the desired hydro-treating
temperature using a fired heater (at 285-34O0C)
 Feed and hydrogen pass downward in a hydrogenation reactor packed with various
types of catalyst depending upon reactions desired (such as cobalt or nickel
oxide/molybdenum oxide catalyst)
 Reactor effluent is cooled and enter the high pressure separator which separates the
liquid hydrocarbon from the hydrogen/hydrogen sulfide/ammonia gas
 Acid gases are absorbed from the hydrogen in the amine absorber
 Hydrogen is recycled with make-up hydrogen
 Further separation of LPG gases occurs in the low pressure separator prior to
sending the hydrocarbon liquids to fractionation
Hydrotreating: flow scheme
Hydrotreating Processes
 Naphtha Hydrotreating
 Primary objective is to remove sulfur contaminant for downstream processes;
typically < 1wppm
 Gasoline Hydrotreating
 Sulfur removal from gasoline blending components to meet recent clean fuels
specifications
 Mid-Distillate Hydrotreating
 Sulfur removal from kerosene for home heating
 Convert kerosene to jet via mild aromatic saturation
 Remove sulfur from diesel for clean fuels
 FCC Feed Pretreating
 Nitrogen removal for better FCC catalyst activity
 Sulfur removal for Sulfur oxide reduction in the flue gas and easier post-FCC
treatment
 Aromatic saturation improves FCC feed “crackability”
 Improved H/C ratios increase FCC capacity and conversion
Hydrocracking
 Hydrocracking is a two-stage process combining catalytic cracking and
hydrogenation, wherein heavier feedstock is cracked in the presence of
hydrogen to produce more desirable products.
 The process employs (1) high pressure, (2) high temperature, (3) a
catalyst, and (4) hydrogen.
 Hydrocracking is used for feedstock that are difficult to process by either
catalytic cracking or reforming, since these feedstock are characterized
usually by
i) a high polycyclic aromatic content
ii) high concentrations of the two catalyst poisons: sulfur and nitrogen
 The process largely depends on the nature of the feedstock and the
relative rates of the two competing reactions: hydrogenation and
cracking.
 Heavy aromatic feedstock is converted into lighter products under a wide
range of very high pressures (70-140 bar) and fairly high temperatures
(400°-800°C), in the presence of hydrogen and special catalysts.
 Hydrocracking Process
 Process Objective:
 To remove feed contaminants (nitrogen & sulfur) and to convert low value gas oils
to valuable products (naphtha, middle distillates, and ultra-clean lube base stocks).
 Primary Process Technique:
 Hydrogenation occurs in fixed hydrotreating catalyst beds to improve H/C ratios
and to remove sulfur, nitrogen, and metals. This is followed by one or more
reactors with fixed hydrocracking catalyst beds to dealkylate aromatic rings, open
naphthene rings, and hydrocrack paraffin chains.
 Process steps:
 Preheated feed is mixed with hot hydrogen and passes through a multi-bed reactor
with inter-stage hydrogen quenches for hydrotreating
 The catalysts convert sulfur and nitrogen compounds to H2S and NH3. Limited
hydrocracking also occurs.
 Reactor effluents are combined and pass through high and low pressure separators
and are fed to the fractionator where valuable products are drawn from the top,
sides, and bottom
 Fractionator bottoms may be recycled to a second pass hydrocracker for additional
conversion all the way up to full conversion the operations of the second stage are
more severe (higher temperatures and pressures). Again, the second stage product
is separated from the hydrogen and charged to the fractionator
Hydrocracking Flow Scheme
Catalytic Reforming
 Catalytic reforming is an important process used to convert low-
octane naphthas into high-octane gasoline blending components
called reformates.
 Reforming represents the total effect of numerous reactions such as
cracking, polymerization, dehydrogenation, and isomerization taking
place simultaneously.
 Depending on the properties of the naphtha feedstock (as measured
by the paraffin, olefin, naphthene, and aromatic content) and catalysts
used, reformates can be produced with very high concentrations of
benzene, toluene, xylene, (BTX) and other aromatics useful in
gasoline blending and petrochemical processing.
 Hydrogen, a significant by-product, is separated from the reformate for
recycling and use in other processes.
Catalytic Reforming
Catalytic Reforming
 Most processes use Pt as the active catalyst. Sometimes
Pt is combined with a second catalyst (bimetallic catalyst)
such as rhenium.
 There are many different commercial processes including
platforming, powerforming, ultraforming, and Thermofor
catalytic reforming.
 Some reformers operate at low pressure (3-13 bar),
others at high pressures (up to 70 bar). Some systems
continuously regenerate the catalyst than in other systems.
One reactor at a time is taken off-stream for catalyst
regeneration
 Catalytic Reforming Process
 Process Objective:
 To convert low-octane naphtha into a high-octane reformate for gasoline
blending and/or to provide aromatics (benzene, toluene, and xylene) for
petrochemical plants. Reforming also produces high purity hydrogen for
hydrotreating processes.
 Primary Process Technique:
 Reforming reactions occur in chloride promoted fixed catalyst beds; or
continuous catalyst regeneration (CCR) beds where the catalyst is
transferred from one stage to another, through a catalyst regenerator and
back again. High temperatures with typical catalysts of platinum and/or
rhenium on alumina and short contact times are used
 Desired reactions include: dehydrogenation of naphthenes to form
aromatics; isomerization of naphthenes; dehydrocyclization of paraffins
to form aromatics; and isomerization of paraffins.
 Hydrocracking of paraffins is undesirable due to increased light-ends
make.
Process steps:

In the platforming process, the naphtha feedstock is mixed with recycled
hydrogen, vaporized , and passed through a series of alternating furnace
and fixed-bed reactors containing a platinum catalyst.
Each pass requires heat input to drive the reactions

The effluent from the last reactor is cooled and sent to a separator to
permit removal of the hydrogen-rich gas stream from the top of the
separator for recycling.
The liquid product from the bottom of the separator is sent to a
fractionator called a stabilizer (butanizer). It makes a bottom product
called reformate; butanes and lighter go overhead and are sent to the
saturated gas plant.
Catalytic Reforming/ Process Schematic
3rd Pass Reactor
2nd Pass Reactor
1st Pass Reactor

Naphtha Feed

1st Pass Heater 2nd Pass Heater

3rd Pass Heater

High Purity Recycle Compressor

Hydrogen

LPG HP Separator

LP Separator
Reformate to
Fractionation
Catalytic reforming reactors
Alkylation

 Alkylation combines low-molecular-weight olefins

(primarily a mixture of propylene and butylene) with
isobutene in the presence of a catalyst, either sulfuric
acid or hydrofluoric acid.
 The product is called alkylate (gasoline) and is
composed of a mixture of high-octane, branched-chain
paraffinic hydrocarbons.
 Alkylate is a premium blending stock because it has
exceptional antiknock properties and is clean burning.
The octane number of the alkylate depends mainly
upon the kind of olefins used and upon operating
conditions.
Sulphuric acid alkylation process

 In cascade type sulfuric acid (H2SO4) alkylation units, the feedstock

(propylene, butylene, amylene, and fresh isobutane) enters the
reactor and contacts the concentrated sulfuric acid catalyst (in
concentrations of 85% to 95% for good operation and to minimize
corrosion).
 The reactor is divided into zones, with olefins fed through distributors
to each zone, and the sulfuric acid and isobutanes flowing over baffles
from zone to zone.
 The reactor effluent is separated into hydrocarbon and acid
phases in a settler, and the acid is returned to the reactor.
 The hydrocarbon phase is hot-water washed with caustic for pH
control before being successively depropanized, deisobutanized, and
debutanized.
 The alkylate obtained from the deisobutanizer can then go directly to
motor-fuel blending or be re-run to produce aviation-grade blending
stock. The isobutane is recycled to the feed.
Sulphuric acid alkylation process
HF Alkylation Process
 Process Objective:
 To combine light olefins (propylene and butylene) with isobutane to form a high octane
gasoline (alkylate).
 Primary Process Technique:
 Alkylation occurs in the presence of a highly acidic catalyst (hydroflouric acid or sulfuric
acid).
 Process steps:
 Olefins from FCC are combined with Iso-Butane and fed to the HF Reactor where
alkylation occurs
 Acid settler separates the free HF from the hydrocarbons and recycles the acid back to the
reactor
 A portion of the HF is regenerated to remove acid oils formed by feed contaminants or
hydrocarbon polymerization
 Hydrocarbons from settler go to the De-Isobutanizer for fractionating the propane and
isobutane from the n-butane and alkylate
 Propane is then fractionated from the isobutane; propane as a product and the isobutane to
be recycled to the reactor
 N-Butane and alkylate are deflourinated in a bed of solid adsorbent and fractionated as
separate products
 HF Alkylation/ Process Schematic
Stripped HF

Olefin Feed Isobutane Recycle

& Isobutane

Reactor
HF Stripper

Depropanizer

Settler Propane
DeIsobutanizer

Fresh Acid N-Butane

HF Regenerator
Debutanizer
Acid Oils
Deflourinator

Alkylate
TREATMENT OF REFINERY GASES
 Removal of H2S from gases is usually performed by absorption in
the liquid phase.
 The concentrated H2S is frequently converted to elemental sulphur
by the “Claus” process.
 In the Claus process 95-97% of the H2S is converted.
 H2S is often removed with solvents that can be regenerated, usually
alkanolamines: e.g. CH2(OH)CH2NH2 MEA (mono-ethanolamine).
 These amines are highly water soluble with low volatility and their
reaction with H2S is much faster than with CO2 so that the amount
of absorbed CO2 can be limited by selecting appropriate conditions.