PLENTY SIDE ENTRY PRESENTATION

1. MIXING IN LARGE
HYDROCARBON STORAGE
TANKS
Bantrell Lunch & Learn
July 12, 2011
Dennis Kerfeld
Regional Sales Manager – West
Side Entry Mixers

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Mixing,Blending or Homogeneity ?
> Mixing covers all process applications, liquid/liquid + gas/liquids +
liquid/solids and solids/solids
> Blending assumes two or more liquids to achieve a final state or third
product within a given time. This can include solid suspension
> (Maintenance of) Homogeneity assumes one product only
> BS&W – maintaining water and solids in suspension within crude oil
All blending applications in large tanks are flow
related and so selection is made by calculating
the required flow and selecting the mixer(s) to
achieve that flow

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Sizing -methodology and limitations
All manufacturers should use some form of selection procedure and it
would involve the physical parameters of the tank. Some mixer
companies have more experience than others, both in numbers in
service and process knowledge. Our system has been in constant
use successfully for over 50 years. It was developed with Shell Oil
in The Hague
Note: If insufficient power is supplied or some of the mixers are out of
action, almost no mixing will take place.

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
REQUIRED INFORMATION
> Tank Diameter and maximum liquid height (the tank height is
not relevant to the calculations)
> Properties of the product(s) – s.g.; viscosity (at operating
conditions); % of each product and volumes
> Process expectations. Blending using pump up or stratified
conditions; heat transfer (bitumen, palm oil) or BS&W
(maintaining the solids and water in suspension as found in
Crude Hydrocarbon or bio-diesel oils)
> The allowable time or limitations to available power

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Recommended mixer positions on the tank – incorrect
positioning can lead to poor mixing and wasted power

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Limitations and obstructions
Tank size & height is not an obstruction – largest
tanks we have mixed are in excess of 120metres in
diameter & 25metres height

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Limitations and obstructions
Floating roof supports do not create difficulties as by the time
the supports reach the floor the mixers have been stopped.
(The lowest mixable depth used in most tanks is about 2½
metres)

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Obstructions such as rigid roof supports can hinder flow and
reduce the effectiveness of the mixers, requiring more power and
time to do the same mixing job

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Flow dispersion pipes which intrude into the tank and have large
diameters will significantly affect the flow leading to product
slowdown and solid deposition.
Horizontal heating coils in general do not have a significant effect,
although vertical heating blocks will.
Roof drains are not a serious obstruction as the diameter is small
compared with the mixer flow.

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
PROPELLERS OR JET NOZZLES
Both systems work!
Both work by creating a jet flow in the tank, The propeller develops
a circulatory motion leading to better entrainment and the flow
reaches across the diameter of the tank. Jet mixers normally
reach a maximum of 13 metres.
To do the same job as propeller mixers jet mixers require a pump
to develop 8 bar pressure at the nozzle and create large flows.
Tanker unloading pumps cannot supply this pressure and volume and
cannot be used. The costs for delaying a tankers departure for this
application would be extremely expensive even if it would be
allowed. It is not unusual to hear of pumps needing twice the motor
power to generate the pressure and flow as the total calculated for
the propeller mixers.

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Flow patterns – propeller v. jet nozzles

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
PROPELLER MIXERS v JET MIXERS
Compare propeller mixer with ALL maintainable parts outside the
tank with jet mixer with ALL maintainable parts inside the tank
Compare the jet flow generated by impellers 14-33” diameter with
jet created by pressure from pump through 4” diameter nozzle.
Compare power required for mixers and jets –jets can require pump
motors with 2 x total power of mixers

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Latest developments
Pointing mixers upward – can reduce blend times by as
much as 50%
Fuel oil Blending in The Netherlands

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
Upward Pointing Mixers
Switchoff is liquid level at which upward pointing mixer(s) should be turned
off to protect floating roof. This is normally at half the HLL. The horizontal
mixer(s) continue to operate until minimum operating level at 2.5d above h2

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
CFD – Computational Fluid Dynamics
A useful tool for ‘seeing’ the flow at a moment in time
and potential deposition points
Showing flow at 10 degrees left
Horizontal – no pipes
Showing flow at 10 degrees left
Horizontal - distributor pipes

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BLENDING HYDROCARBONS IN LARGE STORAGE TANKS
THE END
Thank you Ladies & Gentlemen – I/we will be happy
to take questions now.