Seperation Processes

7/27/2019 Seperation Processes

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SEPERATION PROCESSES

FOR PETROLEUM REFINING

Basics of Separation Operations

Thermodynamics: Phase Equilibrium Mass Transfer and Efficiency of Separation

Operations

st at on Absorption and Stripping

Liquid Liquid Extraction

Crystallization Adsorption

Membrane Separation


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Basics of Separation Operations

Function of Separation

Operation in Refining Crude oil: complex

mixture of a very large of

components Given specifications

petroleum products

Necessary to separate outthe different fractions(cuts)


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I. Basics of Separation Operations

Three mains functions:

Fractionation

Recycling


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Fractionation

Recycling


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I. Basics of Separation Operations Homogeneous Mixtures

Two phases thoroughly mixed in the contact stage Separation factor:

Theoretical stage

mEquilibriu

ABAB

Real stage: separation factor depending on masstransfer kinetics


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I. Basics of Separation Operations Homogeneous Mixtures

Classification according to the separating agent and

the nature of the phases in contact: Distillation

Crystallization by cooling

Li uid Li uid extraction for se aratin com onents whose volatilities are

close and belong to different chemical families) Extractive distillation (Combination of the effect of a phase change by energy

input with the effect of solvent addition)

Adsorption (for difficult separation operations and deeppurification)

Membrane separation based on kinetic selectivity, notinvolving a change in phase (gaseous permeation (gas), Ultra filtration,reverse osmosis (liquid))


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I. Basics of Separation Operations Classification


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I. Basics of Separation Operations Implementation of separation processes

Thermodynamics equilibrium Boiling, Crystallization points, Equilibrium constants

Kinetic factor

Molecular diffusion, Hydrodynamic factors

Mass transfer driving force (C-C*)

Mass flux through the interface

N = K(C C*)

Overall diffusion coefficients (K)

Contact between phases


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Contact between phases


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Certain examples

Gas purification operation by means of solvent Separation by fixed-bed adsorption


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Membrane separation:

Still seldom used in refining

Potential application: Ultra-filtration, Pervaporation andGaseous Permeation


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I. Basics of Separation Operations


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I. Basics of Separation Operations Membrane separation:


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I. Basics of Separation Operations Exercise 1: Relation between the separation

operations processes in the oil refining


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II. Thermodynamics: Phase Equilibrium

Vapor-Liquid Equilibrium

General Description:

Describing a mixture: P, T and [Zi] or P, Vap% and [Zi] orT, Vap% and [Zi]

For binary and ternary mixture

Isobaric Vapor - Liquid Equilibrium Diagrams


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Vapor-Liquid Equilibrium

Isothermal Vapor Liquid Equilibrium Diagram


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II. Thermodynamics: Phase Equilibrium Vapor-Liquid Equilibrium

Two phase envelope

Ethane Benzene mixture


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Azeotrope:

Ex: n-Hexane and Acetone system

A. Isothermal diagram (T = 50C) B. Isobaric diagram (P = 1.013 bar)


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Azeotrope:

Existence only in limited pressure domain (Ex: C2H

6-CO

2)

Exercise 2: Using the SRK model with

ki,j = 0.13 for drawing up isothermal

vapor-liquid equilibrium curves for

the Ethane CO2

system at 263,15K.


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II. Thermodynamics: Phase Equilibrium Equilibrium conditions

Chemical potential and fugacity

Second principle of thermodynamics

Gibbs energy decreases to minimal: dGT,P = 0

Material balance imposing the condition: so

that we can deduce:

At equilibrium, the chemical potential of any component

has the same value in the liquid and vapor phase


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Heterogeneous methods to calculate the K value:Apply different models to the liquid and vapor phase

Methods usin the Re ular Solution model

Chao and Seader, Model 1961


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Heterogeneous methods to calculate the K value

Methods using the Concept of Local Composition

The NRTL Model (Non-Random Two Liquid)

The UNIQUAC Model (Universal Quasi Chemical)

Models Using Groups Contribution: ASOG and UNIFAC Models


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Homogeneous methods to calculate the K value

Representation of the phases at equilibrium by the same

equation of state

Equations of state derived from the Van der Waals theory

For a mixture: ki,j: interaction parameter determined fromexperimental phase equilibrium data


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Mean relative deviations (%) in the calculation of vapor pressures and densities by the EOS


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Relation between Homogeneous and

Heterogeneous Methods

Liquid Liquid Equilibrium

Liquid Liquid Vapor Equilibrium


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Solid Liquid Equilibrium: Crystallization

Formulation of lube oils dewaxing

Purification de paraxylene (Tf= 14C), Tf(m-xylene) = -47C


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Solid Liquid Equilibrium: Crystallization


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Complex mixture

Small number of pseudo-component

Based on TBP distillation

Detailed chromatographic analysis (simulated

Parameters calculated for the model used (critical

coordinates) according to the data available (Tb, S)

Widely used to calculate distillations

Applied seldom to non-ideal due to the presence ofpolar components mixture or liquid liquid equilibrium


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III. Mass Transfer and efficiency of separation operations

Introduction Sizing the various pieces of equipment

Kinetics of transfer of mass

Efficiency of each of the stages

Height of packed column: transfer coefficient betweenphases in contact

Membrane separation: rate of diffusion of each component

Diffusion in a homogeneous phase

Mass transfer between two phases though theinterface

Efficiency of equipment for contact between phases

COMPLEX MECHANISM NEED THE EMPIRICAL DATA


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Diffusion in the homogeneous phase

For binary solution

NA, NB (mol.m-2.s-1): Mass transfer to a fixed point of reference

CA, CB: molar concentration (mol.m-3), vA, vB: velocities (m.s

-1)

The average volume velocity v is given by the equation:

Diffusion law: Ficks law

DAB: Molecular diffusion coefficient (m2.s-1)


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For binary solution

Mass flow NA in relation to a fixed point of reference

By using C to stand for the total molar concentration:

Correlation designed to predict the value of a diffusion

coefficient (DAB)


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In the gaseous phase: Chapman and Cowling (1964)

()A and ()A : diffusion volumes calculated by

summing the contributing terms


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In the liquid phase: Wilke and Chang (1955)

D0AB: Diffusion coefficient of solute A at infinite dilution in solvent B (m2.s-1)

.

VA: Molar volume of A at its normal boiling point (cm3

.mol-1

) MB: Molar mass of the solvent (g.mol-1)

B: Association parameter (2.6 for water, 1.9 for methanol, 1.5 for ethanol

and 1 if the solvent does not give rise to any association

Case of concentrated solution

Vignes equation (1966)


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Transfer between phase:

Phase 1 and 2 in contact

Mass transfer takes place if they are not at thermodynamic

equilibrium

Driving force of transfer: (C C*) leading the equation:

C* corresponding to equilibrium with the concentration C

K [m.s-1]


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Transfer between phase:

Phase 1 and 2 in contact

An individual transfer coefficient relative to phase 1

N = k(C Ci)

An individual transfer coefficient relative to phase 2N = k(Ci C)

C* = mC + q


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Predicting Transfer Coefficients Transfer coefficient depends on the diffusion coefficient

Assumed that the concentration gradient limited to a very

thin stagnant film in the neighborhood of the interface

The interface renewal model: limited contact time,transfer in a transient state:

ONLY IN THE STAGNANT MEDIUM OR BOUDARY LAYER EQUATIONIN THE CASE OF A LAMINAR SYSTEM


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Predicting Transfer Coefficients In practice: Complexity of hydrodynamic conditions

Impossible to determine the coefficient of transfer of mass

Using the dimensionless numbers

Reynoldss :

Schmidts number:


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Predicting Transfer Coefficients

Calculate of Sho(Re,Sc) inside a spherical particle

(Diffusion only)

For a short contact time (Dt/d2 < 0,035):

For fairly large contact time:

Calculate of Sho(Re,Sc) outside a spherical particle

(Diffusion and convection)


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Predicting Transfer Coefficients

Calculate of Sho(Re,Sc) outside a spherical particle

(Diffusion and convection)

By Hughmark (1967)


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Efficiency and Transfer Coefficients

Tray efficiency

(viscosity in cP or mPa.s)


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Efficiency and Transfer Coefficients HETP for packed column

i ill i b i d i i


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IV. Distillation, Absorption and Stripping

IV Di ill i Ab i d S i i


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IV Di till ti Ab ti d St i i


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Realized in the tray column or packing column

Comparison the factors in favor of Tray and PackingTray Column Packed Column

, , ,

(manholes)

Complex column (feed injection product

draw off)

Low liquid retention

Large diameter column Operation when residence time minimized

Overly high/low liquid flow rate - flexibilityof tray design (perforation, use cap, valve)

Small diameter column: Easier install ofcontact equipment

Star-up and shut-down: attenuated

mechanical phenomena

Minimize the tendency to foam

Minimize the column weight

IV Di till ti i th P t l I d t


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IV. Distillation in the Petroleum Industry

Atmospheric distillation of crude oil, including the

important desalting operation

Vacuum distillation of the atmospheric residue

Gasoline distillation and gas fractionation

IV Distillation in the Petroleum Industry


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Atmospheric distillation of crude oil (Topping)

Producing the cuts:

Gasoline cut: feed for the gasoline and gas fractionation

Naphtha cut for the petrochemical industry

Kerosene cut for use in producing aviation fuel

Atmospheric residue as feed to the vacuum distillation unit

Eventually:

Distillate cut drawn off between HGO and the flash zone

for use as a fluxing agent for FO Possible to draw off a light gasoline cut in the distillation

unit at the top and heavy naphtha laterally via stripper

(corrosion problem at the top)



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Atmospheric distillation of crude oil (Topping) Designed to allow crudes of different characteristics

A base crude, representative of the refinerys average oil supply

A lighter crude, which sizes the top of the scheme and furnace zones

A heavier crude, which sets the dimensions of the bottom of the

column and the exchanger train

Allowing the variation in the cut points amounting to about twenty

degree Celsius on TBP

Unit able to operate properly at approximately 60% of its normal

capacity



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Atmospheric distillation of crude oil (Topping) Description of the process - Pressure: 1 3 barg.

- Products drawn off as side streams

by means ofstrippers

- Generally steam stripped or reboiled- Behaving like reflux absorber,

equipped one to three pumparounds

- Overflash Internal reflux of the first

tray above the feed sent back to the

bottom of tower- Overhead condensation total or

partial: residual gas taken up by

compressor and sent to gas plant

- Main column (~50m high): 30 50

conventional trays- Side stripper: 4 10 trays

- Crude preheated in an exchanger

train by recovering heat to 120

160C and desalted

- Desalting takes place at high pressure (~10 bars)

- Heated in a second exchanger train and furnace

to 330 390C

- Into the main column in a partially vaporized

state


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Atmospheric distillation of crude oil (Topping) Fractionation quality: GAP or OVELAP



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Atmospheric distillation of crude oil (Topping) Fractionation quality: GAP or OVELAP

- Other internal specifications

- Flash point of kerosene and gas oils

- End boiling point ASTM D86 of heavy naphtha (generally < 185C)

- Cloud point of heavy gas oil

- Flash point of atmospheric residue



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Atmospheric distillation of crude oil (Topping) Computerized calculation

Choose the thermodynamic model

- Deviations between two extreme models

- Amount of vapor generated in the flash zone: 5%- So, thermal load of overhead condenser: 5%

- Off take temperature: 3 5C

- Overflash: 20%



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Entering Data and Analyzing Results

TBP or ASTM D86 of the crude

Hypothetical component or pseudo-component

Density, Boiling point temperature, molar mass

Number of tray

Thermal exchange zone: 2 4 real trays

Pressure drop between the top and flash zones: 0,4 0,6 bar



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Estimating the Overhead pressure

Amounts of stripping steams Kerosene and gas oils: 15 to 30 kg of steam/m3 of product

Residue: 20 to 30 kg of steam/m3 of residue

Regulating the overflash

3 to 5% of the feed

Analyzing the results

TBP and ASTM product curves

Product specifications (gap or overlap) Flow rate of withdrawn products

Amount of heat extracted by various pumparounds

Convergence Difficulties



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Atmospheric distillation of crude oil (Topping) Technology

Conventional technology

Ordinary carbon steel except for hot zones steel alloys

Usually clad with 12% weight chromium steel

Zone exposed to cold corrosion (top of the tower, reflux drum):Monel (Ni Cu ( Fe) alloys) or special coatings

Conventional valve trays of steel alloy 12%Cr

Tray efficiency diminishes from the top to the feed inlet Wash zones structured packing

Draw off tray - feed the side strippers and the pumparound:total draw off type (chimney tray)

Main column feed inlet of the tangential type

Furnace of cabin or cylindrical type

Heat exchangers of TEMA type the nominal working pressuredoes not exceed of 30 bars

Diameter 9m for a tower processing 1000 t.h

-1

of crude



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Atmospheric distillation of crude oil (Topping) Process variation

Double condensation at the top

of the column

Other flow diagrams



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting:

Essential operation in the refinery

Fouling of exchanger and the furnace

Corrosion of overhead equipment

Atmospheric residue with high sodium content: fouling rate of thevacuum distillation furnace; shorter cycle length for visbreakers,

ata yst po son ng n cata yt c crac ng, ou ng an corros on o

boiler superheaters Severe environment problems

Sources of the salt in the crude (10 80 mg.l-1)

Inevitable

Delibarable contamination (5 to 50 mg.l-1)

Accidental contamination

Concentration in chlorides of overhead water in the towershould not exceed 10 ppm



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting:

Salt content o a number

of crude oils (before andafter transportation)



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting and topping



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting: Mechanism

Diffusion of the crudes salts in water (by washing)

The mixture of water and crude through a mixing valve placed atthe desalter inlet - P = 0,5 (viscous) 1,5 bar(light cude)

Sufficiently fine water-crude emulsion from 1 to 10m

oa escence o wa er rop e s y e ec rocoa escence

Asphaltenes and FeS adsorbed on the water-oil interface stabilizing emulsion agents

Settling (by gravity Stokes law)



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting: Industrial Implementation

E1 = 200 Volt.cm-1

E2 = 1000 Volt.cm-1

Electrostatic desalter with one stage

Electrostatic desalter with two stages



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Atmospheric distillation of crude oil (Topping) Crude Oil Desalting: Industrial Implementation

Desalters performances

Desalting efficiency of 85 95%

Water content in the desalted crude: mower than 0,2% V (0,4 0,5% for

heavy crudes)

Hydrocarbon concentration in the water coming out not exceed 200ppm



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Atmospheric distillation of crude oil (Topping) Corrosion and Erosion

Corrosive agents: Chlorides, organic acids, non-organic salts, sulfur

compound

Corrosion by salts

Injection of caustic

Metals or metal alloys uses: Ti, Monel, Hastelloy

High Temperature sulfur corrosion

T: 300 420C for ordinary carbon steel

5%Cr-5%Mo steel or 12% - 18%Cr steel

Naphthenic Acid corrosion

T: 220C 240C

Severe corrosion above 350C (furnace 18/10/3 steel alloy)

Erosion

Transfer line, overhead line: high velocity and mitered elbow used



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Atmospheric distillation of crude oil (Topping) Precaution to guard against corrosion risks in topping unit



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Vacuum distillation of the Atmospheric residue Purposes:

Extraction of the distillate cuts to feed conversion unit

Feed for bitumen manufacture

Base stocks for lube oil manufacture

Technologies:

Dry vacuum distillation without injection of steam very low pressure(10 15 mmHg at the top)

Wet vacuum distillation with injection of steam in the furnace feed andstripping steam in the bottom of tower (40 60 mmHg at the top)

Semi-wet vacuum distillation with injection only at the bottom of thecolumn

Use of un ejector (called booster ejector)

Fractionation:

Typical cut points for a 350C TBP atmospheric residue: VGO 350 390C(T90 or T95 ASTM D86 360C), Vacuum Distillate: 390 550C (C, Me)

Reduce heavy oil production: to prolong distillates (exceed 585C TBP)



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Vacuum distillation of the Atmospheric residue Definition of terms specific to vacuum distillation:

LVGO

MVGO

HVGO

Cracked h drocarbons

Non condensable Air entering through leaks

Non condensable dissolved in the feed

Light hydrocarbon produced by cracking in the furnace

Slop cut and overflash (3 5% of the feed): internal reflux



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Flow diagram of a dry vacuum distillation unit



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Flow diagram of a wet vacuum distillation unit


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Crude oil vacuum distillation Configuration of fractionation

Heat Exchange zones:

Random packing of metal ringand grates (grids)

Fractionation zones:

Structured packing: more effective and

expensive

Wash zone

Less sophisticated grates (grids)

Distributors Sprays or Gravity

IV. Distillation in the Petroleum IndustryComparison of two columns


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Vacuum distillation Vacuum pumps and Ejector Condenser To create the vacuum

Ejector (venturi effect)-low pressure steam about

of 6 bar

Combination ejector and liquid ring pump similar

to eccentric rotor gas compressors with a seal provided

By a ring of cooled water moving around in a closed circuit

with compression ratio of about 10 (eq. to 2 or 3 ejectors)



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Gasoline Distillation and Gas Fractionation Conventional Flow Scheme

Series of column working at different pressure chosen so that the condensation

can be done by air-cooler exchanger or cooling water

First column: stabilization column or debutanizer

After the amine washing, the overhead cut is sent to deethanizer

Stabilized gasoline is usually fractionated into 2 cuts gasoline splitter

are ract onate n a epropan zer



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Gasoline Distillation and Gas Fractionation



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Gasoline Distillation and Gas Fractionation with absorber and stripper


Gasoline Distillation and Gas Fractionation


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Main Operating Conditions

Common Specification

Debutanizer C5 content in butane: 0,5% mass or 1% volume maximum

1% volume maximum C4 in light gasoline

Depropanizer or Deethanizer

Commercial specifications for the products

Propane in Butane: vapor pressure not exceeded 6 bar rel. at 50C Ethane content in propane: vapor pressure not exceeded 14 bar rel at 38,8C

Splitter GAP 20C



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Gasoline Distillation and Gas Fractionation Other configurations

Cryogenic scheme in some applications to recover olefins contained in gas coming

from conversion unit

Set up with a deisobutanizer to recover isobutane for the alkylation unit,

deisopentanizer, de isohexanizer,

Columns for extracting aromatic compound

Gas treatment unit with the diethanolamine (DEA) washing, LPG sweetening,

sulfur trap and drier type in order to meet commercial specification



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FCC Primary Fractionation Similar to a crude topping unit but has two major differences

Totally vaporized and superheated feed (480 540C)

Large proportion of the gases

Feed always contains traces of catalyst Problem of pressure drop to the limits of

capacity of compressor and the activity of

,

A convention configuration includes: HCO

LCO

Heavy naphtha

Overhead vapors: C2-, C3, C4, light gasoline

Eventually an added draw-off of intermediate

gasoline


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f


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Treatment of FCC gas Including the following sequence:

Compressor

Deethanizer, primary absorber/stripper

Debutanizer

C3/C4 separation

Some characteristics

Working at a relatively high pressure (10 20 bars)

High specific liquid load in comparison to vapor loads High vapor gravity low liquid gravity

Favorable for tray

Sour water stripping

Remove H2S and NH3 contained in the water condensed at the top ofatmospheric fractionation column before the biological treatment

Stripping column supplied with the live steam at the bottom

Equipped with random or structured packing


T f FCC


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Treatment of FCC gas


Treatment of FCC gas


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The primary absorber:

To absorb most of LPG contained in the gas coming from HP seperatordrum with FCC gasoline

Equipped with some thirty tray made of 410S

One or two pumparounds to evacuate the heat of absorption

Reflux with a draw-off sump to collect the water or supplying the top ofthe column with the debutanized subcooled FCC asoline

Stripper

Remove th lightest fraction (C1, C2, H2S ) from wild gasoline

Equipped with some thirty tray made of 410S

Reboiled with LCO coming from primary fractionation

Secondary absorber

Gas from the top of the absorber washed with lean oil LCO (T < 40C)

Debutanizer

Adjust the FCC gasoline vapor pressure some forty trays of 410S

Reboiled with HCO coming from primary column


k f


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Coker primary fractionation

Visbreaker primary fractionation

Fractionation of HF Alkylation Effluents

Treatment of Reforming Effluents

V. Liquid Liquid Extraction in the Petroleum Industry

Separation technique based on the differences in solubility


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between the components of a homogeneous liquid feed in a

appropriate solvent

Employed when distillation alone can not provide an

economically satisfactory solution (azeotropy, too small

relative volatility)

Good for separating components by chemical family

In oil and gas industry: dearomatizing gas oil, deasphaltingheavy cut and extracting BTX aromatics

Compose of two main complementary steps:

Extraction implemented in different ways: One-stage, Crosscurrent,single countercurrent, Countercurrent with reflux, Dual solvent

Solvent regeneration generally by distillation

V. Liquid Liquid Extraction in the Petroleum Industry

Solvent characteristics


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Solvent properties related to the thermodynamics of L L equilibrium

Capacity or Solvent power

Selectivity

Physical properties Viscosity: pumping, dispersion energy, mass and heat transfer, settling velocities

Density: density of the extracted phase, difference between the densities of

extract and raffinate for operating the extractor

Surface tension: low surface tension promotes the dispersion of one phase in theother, large interfacial surface area favorable to mass transfer, stable emulsion

Boiling point: differences in volatility great enough to avoid azeotropic

phenomena, minimize equipment size and energy consumption

Other properties Thermal stability

Chemical inertia

Low toxicity, Biodegradable and high flash point

VI. Solvent Extraction in the Petroleum Industry

Extraction of aromatic compound from lube oil stocks in order to produce

lubricants


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lubricants

Deasphalting of distillation residues to produce both DAO and Asphats

Extraction of Aromatic compound from lighter stocks: gasolines or

kerosenes in order to comply with present and future regulation


Extraction of aromatic compound from lube oil stocks in order to produce

lubricants


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lubricants


Choice of solvent

S l t (S l t it )


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Solvent power (Solvent capacity)

High selectivity for aromatics molecules

Other points enter into consideration in the choice of a solvent


Extraction of aromatic compound Furfural Extraction

Extraction solvents are numerous among which furfural meet the target


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Extraction solvents are numerous, among which furfural meet the target

criteria adequately

Examined different variables:

External variables: Solvent, Extractor, feed composition, extraction

efficiency

Internal variables : Solvent ratio, Extraction temperature, Temperature

, ,

Furfural

Phenol N-methyl-2-

pyrrolidone (NMP)


Furfural Extraction - Comparison


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Furfural Extraction Points to consider for understanding

Water and furfural form a heteroazetrope


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ate a d u u a o a ete oa et ope

The mutual solubility of water and furfural are not negligible

The solvent power of furfural increases when the temperature increases anddegreases with the molecular mass

The selectivity of furfural toward aromatics degreases when the temperatureincreases

Furfural is chemical compound that is sensitive to oxidation, acids andtemperature.

Inhibitors such as amines protect furfural during the storage against the action ofoxidizing agents but they are difficult to use in a unit in operation

Metal such as copper accelerate the oxidation process that form acids, they inturn make furfural break down into resins

Rate of degradation is proportional to the concentration in H+, so water can alsoaffect furfural

Furfural has tendency to break down with temperature (at 230C, 5% is degradedin 80h) with the formation of resin insoluble in aromatics

Furfural is not inert toward some components of feeds so giving rise to complexpolymers


Furfural Extraction Choice of extractor


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Present-day trend is to use the high efficiency RDC (Rotating Disc Contactor)

-High number of theoretical stages (up to 10 compared with 5-7 conventional

columns)

-Very clear-cut raffinate/Extract interface- Raffinate yield 3 to 5% higher

-Possibility of optimizing extraction quality depending on the type and flow rate

of feed by using rotating disc


Furfural Extraction - Flow Scheme

Feed deaeration


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DAO, thermal exchange with the extract to 100C, 50mmHg, eliminate the moisture and air,furfural sensible to oxidation and to presence of water

Extraction Extractor working under pressure (6 bar at the top)

Introduction of feed at the bottom of the extraction zone, solvent at the top of column

Adjusting the feed temperature by an exchanger

Mixed extract side stream drawn off under the feed inlet, cooled in exchanger and sent backto t e tower

Regulated Top/feed/bottom temperature gradient with the set point of the temperature of

the top

Recovery of solvent in the raffinate Equipped exchanger and furnace to heat the raffinate to 200C for vaporizing the furfural in

flash drum and recovering the solvent trace in the steam stripping zone.

Recovery of solvent in the extract Complex circuit to reduce the energy consumption involved in vaporizing furfural

Made up of four consecutive vaporization stages and ends with steam stripping

Water removal and azeotropic distillation section

Drainage system and Inert Gas system


Furfural Extraction


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10-15% Furfural

20% Furfural

recovery

60% Furfural

recovery

90-85% Furfural

10% Furfural

recovery


Furfural Extraction

Azeotrope: 35% Furfural 65% H2O


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Azeotrope: 35% Furfural 65% H2O


N-methyl-2-pyrrolidone (NMP) Extraction

In comparison with furfural, it has the following advantages


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p , g g

Better stability

Better oxidation resistance

Less carryover in the raffinate and the extract Higher solvent power toward aromatics

Lower process temperature

Less toxicity

The following drawbacks

Lower specific gravity

Less selectivity

Higher boiling point


N-methyl-2-pyrrolidone (NMP) Extraction


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N-methyl-2-pyrrolidone (NMP) Extraction Dehydration section


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Deasphalting Purpose of process


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Oily fractions

Production of bright stock and waxes

Preparation of FCC feed with or without an intermediate hydrorefining stepFeed specs for FCC unit: 2000ppm Maxi. Basic nitrogen,

2% Maxi. Conradson carbon content

20ppm mass Maxi. metal

Preparation of hydrocracking feeds to increase the production of high quality

middle distillates

Asphaltic fractions

Production of road quality

Use as components in industrial fuel oil or solid fuels

Feed for conversion unit as visbreakers, oxyvapogasifiers and cokers


Deasphalting Incorporation of deasphalting process in the lube oil

stock production process


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Deasphalting Incorporation of deasphalting process es an extra

conversion unit


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Deasphalting Products and properties


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Deasphalting Solvent characteristics and operating conditions


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Deasphalting Solvent characteristics and operating conditions


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VII. Crystallization in Oil Industry

Solvent Dewaxing

Most common Oil/Wax separation based on crystallization with


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a solvent

Ideal solvent: Dissolve the Oil and Precipitate all the Wax

Solubility and selectivity: good solubility for the oil and goodcrystallization selectivity for the wax

Low heat of vaporization

Low congeal point: remain liquid at filtration temperature

No toxicity or corrosivity

Low price and wide availability

In the industry using the mixture of Methyl Ethyl Ketone (MKE)and Toluene (80%) or Methylisobutylketone


Solvent Dewaxing

Physical properties of MEK and Toluene


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Dewaxing Process Using an MEK-Toluene Mixture as solvent Crystallization in presence of solvent


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Filtration

Separation between the solvent and the oil or the wax by distillation


Dewaxing Process Using an MEK-Toluene Mixture as solvent

Products


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- Dewaxed oil and

-Wax with oil content of 10 20%

(slack wax or petrolatum wax)

-Deoiling (wax with very low oilcontent and foots oil)


Dewaxing Process Using an MEK-Toluene Mixture as solvent(Without in line deoiling)


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Dewaxing Process Using an MEK-Toluene Mixture as solvent

Four main section:

Crystallization section to cool the


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- Crystallization section to cool the

raffinate and solvent, thereby

crystallizing the waxes

- Filtration section to separate the

dexaed oil from the wax cake

-- D st at on sect on w t two

operation for dewaxing unit without in

line deoiling and three with in line

deoiling to separate the solvent from

de dewaxed oil, the wax and the foots

oil

- Solvent system recovering the

solvent exiting the distillation

operation and redistrubuting it in the

form of dilution

Seperation Processes

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Transcript of Seperation Processes