HE15
A 15% hydrous ethanol and 85% gasoline blend, hE15, has been introduced at public gas stations in the Netherlands since 2008. Ethanol fuel specifications worldwide traditionally dictate use of anhydrous ethanol (less than 1% water) for gasoline blending. This results in additional costs, energy usage and environmental impacts associated with the extra processing step required to dehydrate the hydrous ethanol produced via distillation (3.5-4.9 vol.% water) to meet the current anhydrous ethanol specifications. A patented discovery reveals hydrous ethanol can be effectively used in most ethanol/gasoline blending applications.
According to the Brazilian ANP specification, hydrous ethanol contains up to 4.9 vol.% water. In hE15, this would be up to 0.74 vol.% water in the overall mixture. Japanese scientific evidence revealed the water is an inhibitor for corrosion by ethanol. The experiments were done with E50, which is more aggressive and speeds up the corrosion effect. Increasing the amount of water in fuel ethanol clearly can reduce the corrosion. At 2% or 20,000 ppm water in the fuel ethanol, the corrosion stopped. The observations in Japan are in line with the fact that hydrous ethanol is known for being less corrosive than anhydrous ethanol. The reaction mechanism will be the same at lower-mid blends. When enough water is present in the fuel, the aluminum will react preferably with water to produce aluminum dioxide, repairing the protective aluminum oxide layer, which is why the corrosion stops. The aluminum alkoxide does not make a tight oxide layer, which is why the corrosion continues. In other words, water is essential to repair the holes in the oxide layer. Based on the Japanese results, a minimum of 2% water content in fuel ethanol would enable E15 use in regular nonflex-fuel vehicles. Water injection has additional positive effects on the engine performance (thermodynamic efficiency) and also reduces emissions.
Overall, a transition from anhydrous to hydrous ethanol for gasoline blending is expected to make a significant contribution to ethanol's cost-competitiveness, fuel cycle net energy balance, air quality, and greenhouse gas emissions.
The level of blending above 10% (V/V) is chosen both from a technical (safety) perspective and to distinguish the product in Europe from regular unleaded petrol for reasons of taxes and customer clarity. Small-scale tests have shown many vehicles with modern engine types can run smoothly on this hydrous ethanol blend. Mixed tanking scenarios with anhydrous ethanol blends at 5% or 10% level do not induce phase separation. As avoiding mixing with E0, in particular at extremely low temperatures, in logistic systems and engines is not recommended, a separate specification for controlled usage is presented in a Netherlands Technical Agreement NTA 8115 (not published yet). The NTA 8115 is written for a worldwide application in trading and fuel blending.
Read more about this topic: Common Ethanol Fuel Mixtures