E85 Ethanol Industry Guidelines, Specifications and Procedures
Figure 1
As can be seen, for E85 (typically the summer grade), some blendstocks do not meet the 5.5 psi minimum. For E80, some do not meet the 7.0 psi minimum and for E75 very few meet the 9.5 psi minimum. Selection of a sufficiently volatile (high vapor pressure) hydrocarbon allows the final blend to meet minimum ASTM vapor pressure requirements when added at the correct levels. Seasonal Inventory Control: Retailers should exercise caution at seasonal changeover time. For instance, a high inventory of summer grade, if not run down before cold weather, would be below the specified vapor pressure and may adversely affect cold start and warm up performance. Sulfur: Sulfur limits must be controlled because sulfur can damage the catalytic converter. Care should be used in selecting denaturants because these hydrocarbons are the source of most sulfur in denatured ethanol. Methanol and Higher Alcohols: Methanol is held to low limits due to its corrosive properties, while higher alcohols are controlled to ensure ethanol purity. Acidity, pHe and Inorganic Chloride: These are limited to reduce corrosive properties. Solvent Washed Gum/Unwashed Gum: Solvent washed gum can contribute to fuel system deposits. The unwashed gum content is set to limit high boiling point components such as diesel fuel. The difference between unwashed and solvent washed gum can be used to determine the
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