Bantrel blending in large hydrocarbon storage tanks

MIXING IN LARGE HYDROCARBON STORAGE

TANKS

Bantrell Lunch & LearnJuly 12, 2011

Dennis KerfeldRegional Sales Manager – WestSide Entry Mixers

Company ConfidentialCompany Confidential

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



Sizing -methodology and limitationsAll 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.



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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Recommended mixer positions on the tank – incorrect positioning can lead to poor mixing and wasted power



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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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)



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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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.



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.



Flow patterns – propeller v. jet nozzles



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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Latest developments

Pointing mixers upward – can reduce blend times by as much as 50%

Fuel oil Blending in The Netherlands



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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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



THE END

Thank you Ladies & Gentlemen – I/we will be happy to take questions now.

Bantrel blending in large hydrocarbon storage tanks

Technology

large tanks

large storage tanks

large storage tanks

propeller mixers jet

jet flow

solidssolids blending

large diameters

large flows