Environmental Engineering Reference
In-Depth Information
CEN and ASTM specifications are still keeping the chloride content limit for bioethanol too high
at 42 mg/kg maximum (ASTM D7319* and ASTM D7328 methods) and 25 mg/kg maximum (EN
15492 method), respectively, for undenatured ethanol (White Paper 2007). However, the U.S. limit
for E85 is already at 1 mg/kg maximum, and the EU is also planning to reduce its limit, but first the
new, more precise Ion Chromatography (IC) method must be adopted (White Paper 2007).
9.3.13 w atEr c ontEnt
Water can enter ethanol during production, fuel distribution, and storage through condensation
(WWFC 2008). Bioethanol with high water content should not be blended with gasoline (Gray
2005), otherwise a phase separation may occur, and the free water can influence the performance
or even damage the engine (WWFC 2008). Additionally, water in the fuel can cause corrosion and
microbial growth. The water content limit is used to protect the vehicle from these effects when they
use bioethanol even at low-ethanol blends.
Ethanol is hydroscopic and can collect water from ambient air and the distribution system
(IFQC 2004; White Paper 2007). By blending bioethanol (that contains mainly ethanol and water)
with gasoline, ethanol dissolves in gasoline and water, but water dissolves very little in gasoline.
As a result, the blend has a higher water content than its base fossil fuel (WWFC 2008); that is,
gasoline can dissolve up to 150 ppm water at 21°C and E10 up to 7000 ppm at the same temperature
(Chevron 2008).
The solubility of the fuel increases proportionately with ethanol content, the aromaticity of the
base gasoline, and temperature (IFQC 2004; Costenoble 2006). At low temperatures, a phase sepa-
ration will occur (separation of the ethanol from water) and form an aqueous lower phase in the
storage tank and vehicle fuel tank (White Paper 2007). The upper gasoline layer will have a lower
octane number and will be less volatile and consequently may cause serious operating problems for
spark-ignition engines (Chevron 2008). The lower layer is incapable of running the engine (Chevron
2008). The risk is higher for low-ethanol blends (i.e., E5 or E10).
The handling and distribution practices of bioethanol can influence the water content of the fuel
(RFA 2009). There are local parameters that also influence the water content, such as temperature
and humidity. All of these factors must be considered for determination of regional water content
limits. A compilation of the influence of all of these effects could be indicative, reflected by the fact
that the maximum water content of bioethanol in Brazil is in the range of 0.4% v/v § , half that of the
United States (between 0.6 and 0.7% v/v) (White Paper 2007).
Currently, the EU limits the water content to 0.24% v/v, whereas the United States sets the limit
at 1.0% v/v. Brazil has no water specification. The United States and Brazil found the EU limit to be
conservative (White Paper 2007). The difference between these specifications can be explained by
the varying ethanol concentration permitted in gasoline and the difference in gasoline handling and
distribution. For example, the EU, unlike the other two countries, uses no higher than E5 blends and
has a wet logistics infrastructure that enhances the risk of such problems occurring (White Paper
2007). At the same time, Brazilian blends are between E20 and E25 and therefore can hold more
water without phase separation (White Paper 2007). For this specification, the additional cost must
be taken into consideration because the additional drying required increases the cost of production
and can reduce productivity at the mill by up to 7% (White Paper 2007).
* ASTM D7319 Standard Test Method for Determination of Total and Potential Sulfate and Inorganic Chloride in Fuel
Ethanol by Direct Injection Suppressed Ion Chromatography.
ASTM D7328-07e1 Standard Test Method for Determination of Total and Potential Inorganic Sulfate and Total Inorganic
Chloride in Fuel Ethanol by Ion Chromatography Using Aqueous Sample Injection.
EN 15492:2009 Ethanol As a Blending Component for Petrol—Determination of Inorganic Chloride and Sulfate Content
- Ion Chromatographic.
§ Based on a minimum alcohol content of 99.6 vol% (White Paper 2007).
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