Three key considerations for ethanol storage are: 1) Ensuring storage tanks are constructed of compatible materials and operated properly to minimize water ingress and allow for good recirculation. 2) Monitoring ethanol characteristics like pH (pHe), water content, and conductivity during storage to ensure proper storage conditions. 3) Adding the proper amount of corrosion inhibitor and pH buffer additives to manage corrosion and maintain ethanol stability over long storage periods.

1. ethanol storage biofuels
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What considerations are necessary when storing ethanol?
Good ethanol
storage practices
F
or more than 30 years, of petrol corrosion inhibitor
fuel ethanol has been in combination with caustic
transported and stored contaminants sometimes found
safely and effectively around in petrol. The exact cause is still
the world. The two main areas being investigated. However, the
of consideration for fuel ethanol industry trend among ethanol
storage are physical construction producers now is to minimise
and operation of the storage tank corrosion inhibitor/pHe buffer
and preventing any contamination usage. Ethanol marketers should
or unwanted changes to the be aware that as inhibitor treat
fuel ethanol during the storage Without proper buffering additive, fuel ethanol pHe quickly falls below rates are lowered, there is an
period. First, physical attributes specification increased potential for pHe
of the storage tank that should and other corrosion problems
be considered include ensuring byproducts of fermentation. ethanol as a blend component. prevented by the corrosion
the incorporation of compatible The pHe of fuel ethanol is a The Renewable Fuels inhibitor. Therefore as dosage
materials of construction and the measure of the acid strength Association in the US has gets closer to the minimum
specific tank operation, such as and is currently accepted as a recommended a procedure for required, accurate inhibitor
a high or low product draw and predictor of the fuel ethanol’s evaluation of corrosion inhibitor/ treat rate control becomes ever
good tank recirculation capability. corrosion potential. Low pHe pHe buffer performance that more important. Since both
Due to ethanol’s affinity for fuel ethanol has been linked to includes a requirement that over and under treatment of
water, ‘open’ floating roof tanks higher potential for corrosion. proper buffering be maintained inhibitor can result in engine
-storage tanks with the floating High pHe fuel ethanol may for up to 16 weeks. Fuel damage, fuel ethanol purchasers
roof operating as the roof of the contribute to failure of plastic and ethanol buyers should check should insist that the type and
tank that is also open to the other elastomeric parts found in for proper pHe on incoming amount of corrosion inhibitor
atmosphere, should be avoided engine fuel systems. In the US, shipments. There is a written be included on the certificate of
in an effort to minimize the risk of fuel ethanol pHe is specified to be ASTM procedure to determine analysis for every shipment.
water ingress. Secondly, many maintained between 6.5 and 9. pHe, ASTM D6423.
advancements have been made to Fortunately, corrosion and Contaminants
confirm the stability of fuel ethanol pHe can be easily managed by Every action has an
during storage over the past the application of the proper opposite reaction The corrosivity of any fuel
two decades. Monitoring of fuel amount of chemical fuel additive. including ethanol can be
ethanol characteristics, specifically The dominant type of additive The use of pHe buffering worsened by contaminants such
the pHe, water content and used consists of a blend of corrosion inhibitors, especially as chlorides and sulphates.
conductivity, during storage are organic acid corrosion inhibitor in excessive amounts, has been Though these contaminants are
recommended to confirm proper (commonly used in petrol and linked to engine problems such tightly controlled at the ethanol
storage conditions have been diesel fuel) along with an organic as intake valve deposits (IVDs). producer level, they can appear
maintained. A further discussion of amine that acts to neutralise the The problem IVDs may also be again in mid-level blends with
the properties to monitor follows. effects of the small amounts of caused or contributed to by petrol, which itself can be a
Pioneering research by General acids found in new ethanol and the use of excessive amounts source of chloride and sulfate
Motors in the early 1990s created those acids that may be formed
the concept of pHe – the pH over time. Together, these two
of fuel ethanol. By definition, components manage corrosion
pH is associated with water. issues and they are capable of
But fuel ethanol is essentially buffering the ethanol pHe for
anhydrous. GM’s research led long periods of time. This type of
to the discovery that ethanol additive is almost always used in
that contained large amounts North America, but is not normally
of dissolved CO2 (a natural used in South America. However,
byproduct of fermentation) along much of the ethanol now being
with small amounts of water will imported from South America
form carbonic acid over time. In to Europe is being treated with
addition, fuel ethanol may contain corrosion inhibitor/pHe buffer
small amounts of acetic and by the major oil companies
lactic acids that are unwanted and fuel marketers that use Intake valve deposits
supplement biofuels international april 2012 7

2. biofuels heading
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Introducing EC5624A PLUS
E85 fuel pump screen fouled with chloride salts
NexGen Ethanol contamination. Sulphates can be and hydrous fuel ethanol.
Corrosion Inhibitor particularly stealthy as they can This subject is an evolving
unintentionally get into the fuel controversy, so ethanol blenders
ethanol in the form of a sulphite, and marketers should stay
Nalco has created a new formula to make our Ethanol
and then oxidize to the more tuned for further developments
Corrosion Inhibitor better, safer, easier to use and more troublesome sulphate form with as they change and are
cost effective! oxygen exposure and time. Tests established internationally.
that can detect this potential for
As treat rates fall, it is more important than ever sulphate formation are readily The bigger picture
available and have been adopted
to manage dosage accurately. Nalco’s proprietary
by most ethanol producers and Another parameter critical to
fluorescent tracer makes treat rate management fuel marketers. Fuel ethanol engine performance, especially
easy, fast and accurate. buyers should insist on specific engine startability, is Reid Vapor
listing of chlorides, existing and Pressure (RVP), which is an
Improved pHe boosting power
potential sulphates in shipment indication of the volatility of the
Better cold weather handling. certificates of analysis in order fuel. This is normally a parameter
to ensure delivery of a quality that can be controlled only by the
No more heated storage required! product to their fuel ethanol users. petrol/ethanol blender. However
Excellent corrosion protection without risk of Sodium and silicon may it is important to note that petrol
also end up in fuel ethanol and and ethanol, and other fuels
intake valve deposits.
ethanol blends in very small, but including diesel and biodiesel,
Lower treat cost. potentially troublesome amounts. kerosene, jet fuel and heating oil
Sodium is recognised and all have very different volatility
Same regular, on-site service to help you maintain limited by the Brazilian ethanol characteristics. Extreme care
ethanol quality and control inhibitor treat cost. specification, but it is not yet must always be taken at storage
included in the North American facilities to minimise or prevent
Discover more about EC5624A PLUS at specification. Silicon is not cross contamination of various
regulated by either specification. fuels. Even small amounts of
www.nalco.com/TRACE or call Phil Bureman
Both of these contaminants can contamination can create large
at 913-708-4969. be found, though only rarely, issues for the consumer.
as a contaminant in both fuel Further, not all ethanol is used
ethanol and petrol. In excessive as an E5 or an E10. An E15 blend
amounts these contaminants is now being promoted for use
can contribute to several engine in the US for engines of model
problems. Both sodium and year 2001 and newer. Higher
silicone are easy to test for if ethanol blends such as E85 and
contamination is suspected. mid-level blends are already in
limited use in North and South
Conductivity America. As blend levels increase,
the control of critical parameters
Even though many fuel ethanol such as chloride, sulphate and
regulations require that the fuel water contaminants, as well
maintain a specific pHe, there as acidity, pHe, conductivity
are some in the fuel ethanol, and corrosion inhibitor content
petrol and automotive industry become even more critical. l
that believe that ethanol pHe
control may not be as important
as conductivity management. For more information:
This article was written by Phil
Indeed ethanol conductivity is Bureman, senior industry technical
limited in the Brazilian national consultant for biofuels at Nalco – An
© 2012 Ecolab USA, Inc. Ecolab Company, www.nalco.com
specification for both anhydrous
0 april 2012 biofuels international supplement