What is crude oil? Crude oil -.. What is crude oil? Crude oil - Oil we find underground.
DEHYDRATION AND DESALTING - UniMasr Engineering Program (PCE) –Petroleum Field Operations (CHE...
Transcript of DEHYDRATION AND DESALTING - UniMasr Engineering Program (PCE) –Petroleum Field Operations (CHE...
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
DEHYDRATION
AND
DESALTING
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wet Crude Oil
Crude oil from a GOSP may contain very
small droplets of salty water
Many of these droplets are held in
suspension by a thin film of oil that
surrounds them. These droplets are tightly
bound.
Other droplets of water are not surrounded
by a film of oil, these are freely suspended.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydrating & Desalting of
Wet Crude Oil
The purpose is to remove water and salts
from oil that comes out of the GOSPs.
This oil is called Wet Crude, because it
contains too much water and salt to meet
the following requirements:
Water content 0.3% wt, max.
Salt content 10 pounds of salt/1000 bbl
oil, max.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydration of Crude Oil
Water content < 0.2 - 0.5% by volume
Water: Corrosion & scaling for the equipment
Water forms
Free water
Emulsified water
Dissolved water
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Water Forms
Free Water
(F.W.)
Suspended
Water (SS.W.)
Soluble Water
(S.W.)
Emulsified
Water (E.W.)
W/O Emulsion
“Regular”
O/W Emulsion
“Inverse”
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Free water: Settled in 5 min.
Suspended water: require heat - oil viscosity
Soluble water: lower particle size (Solubility)
Emulsified water: drops - phase
W/O emulsion: oil drops in water phase
O/W emulsion: water drops in oil phase
Water Forms
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Factors Promoting Stability of
O/W Emulsion
Oil viscosity
Interfacial tension
Size of dispersed water particle
Density differences
Ratio of volumes of the two phases
Salinity of water: salinity increase the density
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Basic Approaches of Handling
Wet Crude Oil
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydration Techniques
Heating
Chemical Treatment
Electrical Aid
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Heating Techniques
Mechanism: Reduce Oil Viscosity
Types: Direct & Indirect Heating
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wet Crude Heating
Wet crude from a GOSP is heated to 60°C in two
stages before water and salts are separated.
The two stages are a preheating stage and a heating stage.
From the preheating stage, the warm wet crude oil passes
through the shells of a number of crude/diesel oil heat
exchanger. Hot diesel oil flow through the heat exchanger
and heats the wet crude to 60°C.
The diesel oil is heated in a furnace. Heating lowers the
viscosity of the wet crude. The thinner the oil is, the less able
it is to hold water droplets in suspension.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wet Crude Heaters
Heat ExchangersHot oil
Heater Dry Crude
From Desalters
Hot Diesel
HeaterWet Crude
to
Dehydrator &
Desalter
Diesel
Oil Ret.
Wet Crude
From GOSP
Wet Crude HeatersDry Crude
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wet Crude Heaters
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wet Crude Heaters
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Scale Inhibitor Injection
Scale inhibitor is injected into the wet crude before preheating, salt water tends to form hard scaledeposits when it is heated. The scale inhibitor prevents the formation of scales in the exchanger as the wet crude is heated.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Chemical Treatment
De-emulsifiers
Mechanism:
Absorbed to the O/W interface
Rupture the film
Added at the manifold
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Chemical Treatment
De-emulsifiers
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Electrical Aid
Mechanism: electrostatic separation
Film is destroyed
Di-pole attraction
Surface is expanded – ellipsoids
Water droplets combine, grow in size & settled down
Attractive with large volumes of fluids
Used with chemicals
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Chem-electric Dehydrator
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydration and Desalting
Each train consists of three main vessels, one dehydrator and two desalters. Each vessel is identical in construction and operation.
The vessels remove salt water droplets from the crude in a three stage process.
The dehydrator receives hot wet crude from the heat exchanger. The crude spreads across a tray in the vessel under the electrical grid called an electrostatic coalescer.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
A high voltage, low ampere current passes through the coalescer, the current creates a strong electrostatic charge in the vessel, this charge attracts the small salty water droplets in the crude, causing them to rise and join together or coalesce to form large drops which fall out of suspension, and separate at the bottom of the vessel.
The dehydrator removes only the freely suspendedwater, the tightly bound droplets of salt water that remains in the crude stream must be removed in the first and second stage desalters.
Dehydration
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydrator & Desalter
Oil
Outlet
E.T. E.T. E.T.
OIL IN
Inside View of Dehyd. / Desalter
Water Out
H. VOLTAGE EI. GRID OIL
WATER
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dehydrator & Desalter
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Desalting
The major components of a wet crude train are:
Wet crude heater Dehydrator Chemical injection pump Wash water system Mixing valves 1st stage desalter 2nd stage desalter Dry crude storage Storage tank
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Desalting (cont.)
Wastewater and contaminants are discharged from the bottom of the settling tank to the wastewater treatment facility. The desalted crude is drawn continuously from the top of the settling tanks and sent to the crude distillation tower.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Desalting
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Two-stage Desalter
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Wash Water System
Wash water is injected into the crude upstream of the two desalters. The purpose of the wash water is to dilute the salt concentration.
The wash water is recycled between the desalting vessels.
Fresh water is used for the second stage desalting.
Salty water from the bottom of the second desalter is recycled upstream of the first desalter to act as wash water.
Wash water is then sent to a tank for disposal.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Sweetening & Stabilization
of Crude Oil
H2S < 10-100 PPM, weight)
Vapor pressure: ethane > H2S > Propane
Stabilization: removal of light HC
Sour crude oil: 0.05 ft H2S/ gallons of oil
RVP: 8-12 PSI
H2S: A POISON hazard
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Stabilization using
Fractionation
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Crude Cooling & Storage
Dry Crude Coolers
The dry crude from the desalters passesthrough the tubes in the wet crude/dry crudeheat exchanger, then it passes through thecrude after being cooled to drop thetemperature of the crude stream.
Storage Tanks
The dry crude from the second stage desalteris constantly monitored for total salt andwater content.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Crude Cooling & Storage
If it meets specification then it is sent to storage tank.
If it does not then it must be re-processed.
Off-specs oil is sent to wet crude storage for recycling.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Types of Tanks
There are three main types of
tank used for storing liquid
hydrocarbons.
Atmospheric storage
Pressure storage
Heated storage
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Atmospheric Storage
Tanks
All atmospheric storage tanks areopen to the atmosphere, or aremaintained at atmospheric pressureby a controlled vapor blanket. Thesetanks fall into two categories:
- Floating Roof Tanks
- Cone Roof Tanks
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Cone Roofed Tank
This tank is used for the storage of non-toxic liquidswith fairly low volatility.
The roof of the tank will contain a vent, open toatmosphere, which allows the tank to “breathe” whenemptying and filling.
In oil refining, this type of tanks is used for thestorage of gas oils, diesel, light heating oil, and thevery light lube oils.
Tanks containing flammable material will beequipped with foam and fire water jets locatedaround the base of the roof.
All storage tanks containing flammable material andmaterial that could cause environmental damage arecontained within a dyked area or bund.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Cone Roof Tank
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Floating Roof Tanks
Light volatile liquids may be stored at atmospheric pressure by the use of “Floating Roof ”tanks where the roof of this tank literally floats on the surface of the liquid contents of the tank. In this way the air space above the liquid is reduced to almost zero, thereby minimizing the amount of liquid vaporization that can occur.
The roof is specially designed for this service and contains a top skin and a bottom skin of steel plate, held together by steel struts. These struts also provides strength and rigidity to the roof structure.
The roof moves up and down the inside of the tank wall as the liquid level rises when filling and falls when emptying. The roof movement is enhanced by guide rollers between the roof edge and the tank wall.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Floating Roof Tank
When the tank reaches the minimum practical level for the liquid contents the roof structure comes to rest on a group of pillars at the bottom of the tank.
These provide the roof support when the tank is empty and a space between the roof and the tank bottom. This space is required to house the liquid inlet and outlet nozzles for filling and emptying the tank which, of course, must always be below the roof.
The space is also adequate to enable periodic tank cleaning and maintenance.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Floating Roof Tank
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Floating Roof Tank
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Pressure Storage
Pressure storage tanks are used to prevent or minimize the loss of the tank contents due to vaporization. These types of storage tanks can range in operating pressures from a few inches of water gauge to 250 psig. There are three major types of pressure storage. These are:
Low-pressure tanksThese are dome roofed tanks and operate at a pressures of between 3 ins water gauge and 2.5 psig.
Medium pressure tanksThese are hemispheroids or spheroidal which operate atpressures between 2.5 to pressures up to 15 psig.
High-pressure tanksThese are either horizontal “bullets” with elipsoidal or hemispherical heads or spherical tanks (spheres). The working pressures for thesetypes of tanks range from 30 to 250 psig.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dome Roof Tanks
Dome tanks are used to store high vapor pressure naphtha
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dome Roof Tanks
Pre-Stressed Concrete Tanks
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Dome Roof Tanks
A dome roof tank is a closed cylinder witha rounded top. They are used to storehigh vapor pressure hydrocarbons.
Liquefied Petroleum Gas (LPG) tanks areheavily insulated to prevent ambient heatfrom entering the tank. There is stillconstant vaporization (boil off) of some ofthe propane/butane liquid. One volume ofliquid changes to about 200 volumes ofvapor. Therefore, as product boils off itcreates pressure in the tank.
Petrochemical Engineering Program (PCE) – Petroleum Field Operations (CHE N303) – Spring 2009/2010
Dr. Fatma Ashour - Dr. Sahar El-Marsafy
Heated Storage Tanks
Heated storage tanks are more commonin the petroleum industry than mostothers.
They are used to store material whoseflowing properties are such as to restrictflow at normal ambient temperatures.
In the petroleum industry productsheavier than diesel oil, such as heavy gasoils, lube oil, and fuel oil are stored inheated tanks.