Sources
Bio Ethanol may be produced from different feedstocks and no international standards have been set up.
Properties
The biggest difference to gasoline/petrol is the the oxygen content.
Pure Ethanol is a flammable, colorless liquid which looks like water.
The heating value per litre is 27% lower compared to gasoline/petrol (26.74 MJ/kg 11,500 BTI/lb). The fuel mileage in practice is 5% to 12% lower(Handbook for Handling, Storing and Dispensing E85). This also relates to the higher densitiy which is at the upper level of gasoline/petrol. And the stochiometric air/fuel ration is smaller (9) compared with gasoline/petrol (14.7) reducing the energy demand for air intake and compression.
Ethanol fuel shall contain 99.8% ethanol at minimum, 0.3 % water maximum, acetaldehyde 0.0025% max, acetic acid 0.0025% max..
Ignition improver, MTBE, Isobutanol and corrosion inhibitor may be added more....
Ethanol is not as toxic and corrosive as Methanol, it contains in its pure form no carcinogenic compounds, but is used only with a certain gasoline/petrol amount inheriting the carcinogenic characteristics.
Ethanol vapor is heavier than air. Ethanol will mix with water, only higher amounts tend to separate, thus condensing in tanks should be avoided.
The octane number is 98-100.
Ethanol flame are less bright than gasoline/petrol but easily visible in daylight. At low temperatures (0°C 32°F) E85 vapor is more flammable than gasoline but at normal temperatures E85 is less flammable because of the higher autoignition temperature of 454°C 850°F. Ignition may occur between 3% to 19% fuel vapor in air which is elevated compared to gasoline/petrol with 1% to 8%.
Ethanol is not an electric insolator like gasoline/petrol.
The reid vapor pressure is much lower compared to gasoline (0.15 bar 15 kPa 2.3 psi).
Starting with 80% Ethanol the vapor pressure at 37.8°C is 38-58 kPa.
Commercial fuel blends
E85 is specified in the US more...
In any case Ethanol has to be denatured in order to avoid consuming by humans. This gives E95, if 5% gasoline/petrol is added.
With the Ethanol part of the blend, no additives used for gasoline/petrol are necessary.
compounds shall be limited (ASTM D5798-99):
- Lead <2.6 mg/l
- Phosphorus < 0.3 mg/l
- Water < 1%
- Methanol <0.5%
- Higher alipatic alcohols C3-C8 < 2%
- Acidity as acetic acid < 50 mg/kg
- Inorganic chloride < 1 mg/kg
- Total chlorine as chlorides < 2 mg/kg
- Gum unwashed < 20 mg/100ml
- Gum solvent washed < 5 mg/100ml
- Copper < 0.07 mg/100ml
Consequences of Ethanol usage
The car fuel filter should be changed after the first few tankfuls of ethanol after having been operated with other fuels. After this, the ethanol will maintain a clean system.
Cold weather starting is poor compared to gasoline/petrol. Therefore winter blend contain up to 30% gasoline.
Because Ethanol conducts electricity aluminium parts shall be avoided.
Other materials degrading when in contact with Ethanol include natural rubber, polyurethane, cork gasket material, leather, polyvinyl chloride (PVC), polyamides, methyl-methacrylate plastics and certain thermo and thermoset plastics.
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