ASTM D7794 Standard Practice for Blending Mid-Level Ethanol Fuel Blends for Flexible-Fuel Vehicles with Automotive Spark-Ignition Engines
6. Blending Procedures
6.1 This practice includes procedures for blending mid-level ethanol fuel blends at the bulk distribution terminal and at retail using a fuel blending dispenser.

6.2 A fuel blending plan shall be developed describing the necessary actions needed to achieve the targeted mid-level ethanol fuel blends and performance expectations of flexible-fuel vehicles.
6.2.1 Blending plans utilizing new equipment installation or conversion of existing equipment depend on thorough preparation and planning for the entire fuel system.

6.2.2 The investigation and design of the wetted fuel system starts with a review of the flow of the fuel from receipt through retail delivery ensuring materials compatibility with the blending components and the blended mid-level ethanol fuel blends.

6.2.3 Fuel storage and blending systems shall be approved by the jurisdictions in charge of storage tanks, fuel dispensers, and associated equipment.

6.2.4 If a single hose blending dispenser is used, the entire dispenser shall be dedicated to serving flexible-fuel vehicles. If a multiple hose dispenser configuration is used, one hose may be dedicated to E0 or E10 fuel, and one or more additional hoses may be dedicated to mid-level ethanol fuel blends.

6.2.5 Documentation of the findings and changes made during the system review may prove beneficial for the fuel blender's future reference.

6.2.6 The plan should include a strategy for handling the variability in ethanol and gasoline content in fuels being delivered and shall take into consideration the design and operational abilities of the blending meters that will be used.

6.2.7 This review should apply to the initial handling point at the terminal, through the distribution and transport system, and ultimately to the end point - the retail point of sale.

6.3 Determination of Blending Component Properties:
6.3.1 It is the responsibility of the suppliers of fuels that will be used for blending mid-level ethanol fuel blends to provide the blending parties with product transfer documents that contain, at a minimum, the information required by all applicable regulatory agencies. In the United States, this includes, among other items, a product description and the applicable Automotive Fuel Rating. The fuel supplier is responsible for ensuring that the product transfer documents are a true and accurate representation of the materials being supplied. Because product transfer documents are not always required to contain all information necessary for the blending party to accurately determine compliance with the final blend, the blending party must be prepared to either obtain a Certificate of Analysis from the fuel supplier(s), arrange for specific purchase specifications with their supplier(s), or have a sample of each component tested periodically to determine the ethanol content using Test Methods D4815 or D5599 for gasoline or gasoline-ethanol blends, and Test Method D5501 for Specification D5798 ethanol fuel blend, the resulting mid-level ethanol fuel blend, or for Specification D4806 denatured fuel ethanol. For Specification D4806 denatured fuel ethanol, the blending party shall also determine that the inorganic chloride content does not exceed a level that would result in finished mid-level ethanol fuel blend that would have more that the specified 1 mg/kg maximum of Specification D5798.

6.3.2 The blending party should be aware that the spark-ignition engine fuel (Specification D4814) used may contain ethanol up to the maximum concentrations permitted by fuel specifications and regulations, and that this content may change over time. Likewise, ethanol fuel blends (Specification D5798) may change in ethanol content depending upon the month and location of the intended sale of the ethanol fuel. These changes must be taken into account when preparing blending formulas for mid-level ethanol fuel blends.

6.3.3 The blending party shall also be aware that denatured fuel ethanol for fuel blending (Specification D4806) contains from 1.96 to 5.0 volume % hydrocarbons as denaturant (most often 2.0 to 2.5 volume % denaturant). This hydrocarbon content must also be taken into account when preparing blending formulas for mid-level ethanol fuel blends.

6.4 Blending Formula:
6.4.1 The formula used for blending mid-level ethanol fuel blends is based on the lever arm rule for binary components used to make a blend. To make such a blend, gasoline or gasoline-ethanol blend (Specification D4814) will be used to provide the hydrocarbon portion, and either ethanol fuel blend (Specification D5798) or denatured fuel ethanol (Specification D4806) will provide the ethanol portion. Blending calculations shall be based on "gross" gallons; (not temperature compensated net gallons).

6.4.2 The formula is:
FG = (FEE - FEML)/(FEE - FEG)
where:
FG = fraction of gasoline to be used to make the mid-level ethanol fuel blend,
(1 - FG) = fraction of the ethanol fuel or denatured fuel ethanol to be used to make the mid-level ethanol fuel blend,
FEE = fraction of ethanol in either the ethanol fuel blend (Specification D5798) or denatured fuel ethanol (Specification D4806),
FEML = the desired fraction of ethanol in the targeted mid-level ethanol fuel blend, and
FEG = the fraction of ethanol in the gasoline.

6.4.3 Example 1, Bulk Distribution Terminal Blending - The following example is used to make mid-level ethanol fuel blends at a terminal or bulk plant.

6.4.4 Assume that an E30 mid-level ethanol fuel blend is desired to be made from straight gasoline and denatured fuel ethanol at the terminal, thus FEML = 0.30.

6.4.5 The gasoline in terminal storage has no ethanol content, thus FEG in Eq 1 is 0.0.

6.4.6 The ethanol content in the denatured fuel ethanol at the terminal is determined to be 97.5 volume %, or FEE = 0.975.

6.4.7 For this example, we use Eq 1.
FG = (0.975 - 0.30)/(0.975 - 0.0) = 0.692

6.4.7.1 Thus the fraction of gasoline for this blend is 0.692 or 69.2 volume %. And the fraction of denatured fuel ethanol is 1 - 0.692 = 0.308 or 30.8 volume %.

6.4.8 Example 2, Retail Station Blending - The following example is used to make mid-level ethanol fuel blends at retail stations using fuel blending dispensers. Analysis of the ethanol content of the gasoline and the ethanol fuel blends is known from the supplier.

6.4.9 Assume that an E30 mid-level ethanol fuel blend is desired to be made from gasoline with 10 volume % denatured fuel ethanol (E10) and ethanol fuel blend at the retail site, thus FEML = 0.30.

6.4.10 The (E10) gasoline in the retail tank storage has 9.7 volume % ethanol content as reported by the fuel supplier, thus FEG in Eq 1 is 0.097.

6.4.11 The ethanol fuel blend at the site is reported by the supplier to contain 72.5 volume % ethanol, so the ethanol content in the denatured ethanol FEE = 0.725.

6.4.12 For this example, again we use Eq 1.
FG = (0.725 - 0.30)/(0.725 - 0.097) = 0.677

6.4.12.1 Thus the fraction of gasoline for this blend is 0.677 or 67.7 volume %. And the fraction of ethanol fuel is 1 - 0.677 = 0.323 or 32.3 volume %.

6.4.13 Example 3, Retail Station Blending - The following example is used to make mid-level ethanol fuel blends at retail stations using blending dispensers. In this case we have a bill of lading from the terminal listing the denatured fuel ethanol contents in the ethanol fuel blend and the gasoline.

6.4.14 Assume that an E50 mid-level ethanol fuel blend is desired to be made from gasoline with 10 volume % denatured fuel ethanol (E10) and ethanol fuel blend at the retail site, thus FEML = 0.50.

6.4.15 The E10 gasoline from the terminal has 9.5 volume % ethanol content assuming that the denatured fuel ethanol blend had 5.0 volume % denaturant (see 6.3.3); thus FEG = 0.095.

6.4.16 The ethanol fuel blend is reported from the supplier to be made from 70 volume % denatured fuel ethanol and 30 volume % gasoline. Since denatured fuel ethanol contains hydrocarbon denaturant, we must account for this hydrocarbon to get the true ethanol content in the ethanol fuel. The denatured fuel ethanol contains about 95% pure ethanol (see 6.3.3). Thus the ethanol content in the ethanol fuel is 0.095 (70 volume %) = 66.5 volume %, thus FEE = 0.665.

6.4.17 For this example, again we use Eq 1.
FG = (0.655 - 0.50)/(0.665 - 0.095) = 0.290

6.4.17.1 Thus the fraction of E10 gasoline for this blend is 0.290 or 29.0 volume % and the fraction of ethanol fuel blend is 1 - 0.290 = 0.710 or 71.0 volume %. If the ethanol and hydrocarbon components of the fuel inventory are unknown, retail fuel blending dispensers must be programmed to cease dispensing any mid-level ethanol fuel blend.

6.5 It is recommended that Mid-Level Ethanol fuel blends be identified as "Mid-Level Ethanol Blend". It is also recommended that the product description name be followed by the term EXX, where XX represents the nominal percentage of denatured fuel ethanol and that each fuel dispenser offering Mid-Level Ethanol Fuel Blends provide a cautionary statement advising the purchaser that the fuel is "For Flexible-Fuel Vehicles Only".

6.6 Target ethanol contents for the various mid-level ethanol fuel blends covered by this practice could follow a general practice of EXX +/- 5 volume %.

6.7 Volatility Requirements - In order to confirm compliance with applicable volatility requirements, it is necessary for blending parties of mid-level ethanol blends to first confirm that the ethanol fuel blend used to prepare those blends is compliant with Specification D5798. This may be accomplished by receiving a certificate of analysis or other acceptable forms of product compliance assurance from the supplier of the ethanol fuel blends. Ifthe blending party will be blending using Specification D4806 denatured fuel ethanol, the blending party shall arrange for the preparation of a representative sample of the target ethanol/hydrocarbon ratio using the Specification D4806 denatured fuel ethanol and Specification D4814 gasoline or gasoline-ethanol blend that will be used to make the blend and test the mixture for vapor pressure using Test Method D5191.
6.7.1 The measured vapor pressure shall meet the minimum vapor pressure specified in Specification D5798 for the volatility class for the time and location where the mid-level ethanol fuel blend will be used.

6.7.2 Ifthe minimum vapor pressure limit is not met, a more volatile gasoline or gasoline-ethanol blend shall be used and the vapor pressure confirmed once again using the procedures of 6.7.

7. Keywords
7.1 automotive spark-ignition engine fuel; blending formula; conventional-fuel vehicles; denatured fuel ethanol; ethanol; ethanol fuel blend; flexible-fuel vehicles; fuel blending dispenser; fuel ethanol; inorganic chloride; mid-level ethanol fuel blends; phase separation; water tolerance