Ethanol Solution: Just Add Water?

By Ron Kotrba | January 10, 2008
Adding anhydrous ethanol to gasoline at 10 percent concentration has been the U.S. standard blend protocol for years, but a different perspective reveals phenomena with the power to reduce the intensity of production and make transporting ethanol easier and less costly.

According to Frits Dautzenberg, founder of San Diego-based consulting company Serenix Corp., molecular chemistry defies the conventional wisdom of drying ethanol and blending it with gasoline in low percentages. "If you have a fuel-alcohol and gas mix, and it picks up water from the atmosphere, you get three phases—water, gas and alcohol," he said. "If the ethanol concentration is beyond 10 percent, then the water in the mix is taken up by the alcohol, and then water and gasoline are completely compatible."

Source: Serenix Corp.

Dautzenberg and Netherlands-based client Process Design Center BV were investigating new ways to dry ethanol and stumbled across unexpected interactions among water, ethanol and gasoline. "We knew of the problems in drying ethanol," he said, referring to the capital- and energy-intense employment of molecular sieves in dehydration. "We tried to find another way, so we asked ourselves, ‘Why not use gasoline to dry the ethanol?' The hydrous ethanol and gasoline mix should not have been miscible, but it was fully miscible." As a result, a ternary equilibrium diagram was formed. "We went to Shell in Holland with this information, and they said, ‘This cannot be true,' but they investigated it further only to arrive at similar results," Dautzenberg said.

Following the nonlinear evaporative curve for ethanol blends, which displays the worst property characteristics at 6 percent and improves dramatically when percentages surpass 10 percent ethanol, water problems in ethanol-blended fuel are much the same. "Five or 6 percent ethanol is a very dangerous area," Dautzenberg said. "Even if there is only a little water present, it will separate with the water on the bottom." The simple solution: Add more azeotropic ethanol (96 percent alcohol, 4 percent water). "We could go up to 20 percent to 30 percent," said Dautzenberg, adding that a U.S. EPA waiver is needed to do so.

Eliminating ethanol drying could offer producers a 20-cent-per-gallon production savings and drop investment costs. The reduction of energy consumption at the plant could also make U.S. ethanol production more sustainable—by up to 50 percent, Dautzenberg contends. While more studies are needed to look at pipelining 15 percent or more hydrous ethanol in gas through petroleum pipelines, Dautzenberg said the principles should hold steadfast. "If you premixed a certain higher percentage of hydrous alcohol and gas, the water-gas-ethanol mix will remain homogeneous—and therefore no corrosion concerns," he said.