title “reducing energy costs whilst increasing · foundation settlement ... •small leak washed...
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TITLE “Reducing energy costs whilst increasing
operating efficiencies in terminal tank farms – achieving
high operating standards and effective cost
programmes with side-entry tank mixers”
Christopher F. Hastings
Market Specialist – Petroleum Industry
Mixing Solutions Ltd UK / Philadelphia Mixing Solutions Ltd USA
February 22, 2013
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TITLE “Reducing energy costs whilst
increasing operating efficiencies in terminal
tank farms – achieving high operating
standards and effective cost programmes with
side-entry tank mixers”
Christopher F. Hastings
Market Specialist – Petroleum Industry
Mixing Solutions Ltd UK / Philadelphia Mixing Solutions Ltd USA
February 22, 2013
WWW.STOCEXPO.COM
StocExpo 2013
Case Study #1
Design improvements to tank mixing
that meet improved oil movements,
increased tank integrity and energy
savings.
Case Study #2
Using tank mixers to optimize heat
transfer and improve tank integrity in
asphalt, bitumen and coal tar pitch
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Case Study #1 Design improvements to tank mixing to meets improved
oil movements, increased tank integrity and energy savings.
Faster throughputs
Operational flexibility
Extended API 653 & EEMUA 159 tank inspection periods
Reduced risk of tank failure
Energy savings in tank mixing
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Construction of a 600,000 bbls crude oil
tank, Cushing, Oklahoma
Construction of a 600,000 bbls crude oil tank, Cushing, Oklahoma
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600,000 bbls crude oil tank – Plains Marketing Cushing Oklahoma
Most Tank Owners apply full API 653 & EEMUA 159 Tank Inspections every 10 -
20 years for integrity purposes, this included internal and external inspections
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750,000 bbls crude oil tank – Buckeye Pipeline (VOPAK), Bahamas
During API 653 & EEMUA 159 Tank Inspection the performance of
the tank mixers should be considered, why…..
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37,000m³ / 232,571bbls
evacuated from the tank in
15 minutes.
Tankage built in 1971 and
full inspection in 1990 when
ownership was transferred
to another operator.
Foundation settlement
checks every three years,
last being one year before
the failure.
Because of this - Tank failure - worst case scenario being…….
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On September 12, 2005 there was a minor leak of crude oil from one of the
other tanks. This tank was emptied and about to be cleaned in preparation
for proper inspection when the October 25 spill occurred in one of the other
three large tanks.
The catastrophic failure of one crude oil tank at the facility released 37,000 M³
(232,570 bbls) in the space of 15 minutes. Fortunately, despite the force of
the surge from the tank all but about 3M³ (19 bbls) was contained within the
bunding around the tank farm. High winds prevented a build up of vapors that
could have presented the risk of fire but, at the same time, spread the smell of
oil across a wide area generating intense media interest.
An investigation into the incident showed that the rupture originated in the
tank floor, where a gutter had formed, allowing water that had separated out
from the crude oil to pool and cause widespread corrosion, it had not been
picked up by normal inspection methods. http://www.aria.developpement-
durable.gouv.fr/ressources/ac070279__aria_30934_kallo_ah_impel07_26102007_en.pdf
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Lessons to be learned
1. Avoid or limit the presence of corrosive products
that can settle out, by removing water from the oil
before it is placed in storage
2. Prevent corrosive products from settling out by use
of effective mixing
3. Remove any product that has settled out, although
this may not remove any product that has settled in a
gutter
If the propeller flow penetration does not reach
completely across the tank floor then little to no
recirculation will take place and only “zonal
agitation” will take place creating the possibility of
sediment build ups a reality – as it did in this
case!
As recently as March this year a similar tank
failure occurred on the East Coast of the USA.
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•Void created low spot in the floor
•Corrosive water collected in the
low spot on the floor
•Deposition build up prevented
drainage
•Small leak washed sand into the
rock voids
•Tank Shell collapsed
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Extensive laboratory validation and Field data has shown clearly why so many tank
issues come about. Poor flow penetration leads to deposition build-up and should low
spots exist in the tank floor then water pockets are created. Failure of the propeller to
eliminate the build-up only compounds the situation. At some point tank floor failure is
inevitable unless a prior scheduled API 653 or EEMUA 159 Tank Inspection catches
the situation first, this is not always that easy because the floor when “unloaded-
empty” verses “loaded-full” is not always the same
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The aforementioned problems can be overcome by having tank
mixers that can generate an effective flow pattern in the tank.
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The aforementioned problems can be overcome by having tank
mixers that can generate an effective flow pattern in the tank.
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The aforementioned problems can be overcome by having tank
mixers that can generate an effective flow pattern in the tank.
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The displacement flow from the propeller drops to the
floor and is guided across depending upon the angle that
the propeller is pointed.
Swivel-Angle tank mixers and best for controlling
deposition and preventing situations that have already
been discussed.
Now the “kicker”, obviously the propeller has to deliver a
penetrating flow completely across the floor, otherwise
“zonal agitation” is all that can be expected. This is
where problems start to get created and deposition builds
up.
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So with a well designed tank mixing system you can expect the following:
• Oil Movements continue unhindered by disruptions o Blending, Enhancing, Optimizing, Upgrading is fully maximized and product specification is met, and as required in reduced batch cycle time
o Savings account for less diluent (light crude oil) being used to achieve a certain specification for the CDU
Tank volume is always maximized oDeposition is eliminated, being homogenized in the overhead oil – “what comes in goes out”
oSavings - Tank Cleaning costs >$100,000 / €80,000 and in tankage in excess of 500,000 bbls / 80,000m³ capacity saving experienced are >$250,000 / >€200,000
Tank integrity is always at the maximum, and Tank Floor corrosion risk is dramatically reduced if not eliminated
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Case Study #2 Using tank mixers to optimize heat transfer and improve tank integrity in asphalt, bitumen and coal tar pitch Case
Temperature Uniformity – Product Specification
Operational flexibility
Extended API 653 & EEMUA 159 tank inspection periods
Reduced risk of tank failure
Energy savings in tank mixing
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Overview
Companies who specialize in asphalt / bitumen handling & storage indicated that the most important aspects of their business include heating, permitting, safety, transporting, tank construction, tank management, environmental control and quality control. All companies indicated that heating has become their number one expense in handling and storing of asphalt and bitumen. Previously their largest single expense used to be personnel, but now it is heating!
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Energy - Heating Keeping the binder at the right temperature is perhaps the most important goal of any asphalt storage facility commented Asphalt Operating Services. “The whole issue is keeping asphalt hot.” Managing the heating cost is the key to operating efficiently. Hot oil and steam are now the standard ways to heat asphalt.
So if you are storing asphalt,
bitumen or come to that heavy
bunker fuel oil at elevated
temperatures you better ensure
it is being done economically.
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Poor mixing will ultimately lead to:
Deposition build up leading to poor heat convection
Expensive tank floor repairs
At worst a tank failure
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The aforementioned problems can be overcome by having tank
mixers that can generate an effective flow pattern in the tank.
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Further gains in heat uniformity can be gained by a double angle on the tank mixer
mounting – 10⁰ propeller left and 5⁰-10⁰ propeller upwards. This not only
produces better “rolling action in the tank” but can reduce blend times.
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A Swivel-Angle tank mixer
installed on an 10,000m³ bitumen
storage tank at 200⁰C - 380 cSt
viscosity.
Swivel-Angle mixers bring added
value to any application where
solids can build up on the floor or
“coke” the coils / heaters” thus
preventing good heat convection.
The swivel action facilitates a
sweeping action over the floor
and coils / heaters thus
preventing this from happening.
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So in summary from Laboratory validation,
Engineering Simulation Field Data Analysis we
know…
The key to good mixing is in developing
penetrating flow beginning with the propeller
Clearly from the many tank issues not all
propellers are equal in performance
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There are various propeller shapes and designs available to a Tank Owner as discussed
Some have significance energy saving benefits and performance enhancements
There are no API or ISO Standards to guide selection it is very difficult for Tank Owners to determine what is and what is not the best option for them.
Available propeller technologies range from 50-60 years old to the present day
50 – 60 Year Old Technology
Pitch Adjusted Propeller
Minimum Mixing Energy input
0.45hp/1000 bbls (corrected)
2.111kW / 1000M3 (corrected)
50 – 60 Year Old Technology
Marine Three Blade Design
Minimum mixing energy input
0.25hp / 1000 bbls (vendor stated)
1.173kW / 1000M3 (vendor stated)
Advanced Pitch Propeller
Minimum Mixing Energy input
0.15hp / 1000 bbls (vendor stated)
0.707kW / 1000M3 (vendor stated)