Renewable, low-cost, Midwestern grits also soon could be part of industrial paint sprayers and an alternative air conditioning system.
The ethanol-filtering technique will get a workout this year, as U.S. Department of Agriculture analysts estimate that ethanol demand should increase 100 million gallons between September 1994 and August 1995.
Agricultural engineer Michael R. Ladisch developed the prototype laboratory system that used corn grits (ground corn kernels) to extract water from corn-made ethanol for use in automotive fuel in 1979. Ladisch forced ethanol in vapor form through a column of grits. The grits pulled water out of the ethanol.
Some alternative ethanol-drying systems use benzene or cyclohexane, which require special handling to avoid health risks to those who use them. Other systems use relatively expensive, inorganic compounds, which require hotter temperatures and are not biodegradable.
Corn grits are inexpensive, pose no health risk and are easy to recycle.
Ladisch's system, which was scaled up for industrial use in 1984 thanks to a team effort that brought together researchers from Purdue and Archer Daniels Midland, is getting a workout as industry works to meet the increasing demand for ethanol. Today the system is used to produce more than half of all the ethanol in the nation. That's 750 million gallons of ethanol processed annually from 288 million bushels of corn.
After Ladisch's success with drying ethanol, Monsanto EnviroChem funded additional experiments in which Ladisch used corn grits to dry air and other gases needed in industrial applications such as paint spraying and ozone generation. In particular, Ladisch studied use of grits in pressure-swing dryers, which dry the air for these applications.
Pressure-swing dryers consist of two columns packed with desiccants (materials used to remove moisture from air) and connected by tubes that carry air for processing. As one column dries the air under high pressure, desiccants in the other column are regenerated by a portion of the low-pressure, dry air flowing from the working column.
Ladisch, a professor of food and agricultural engineering with Purdue's Laboratory of Renewable Resources Engineering, saw an opportunity to replace the inorganic desiccants with environmentally friendly, low-cost corn grits.
Ground corn grits in their natural state don't dry gases quite as well as the inorganic particles currently in use. But with a grant from the U.S. Department of Agriculture, Ladisch modified the grits to make them more porous and increased their ability to pull moisture from air.
Also, in work funded by the National Science Foundation, a Purdue research team created synthetic grits from starch and cellulose. The team was headed by Ladisch, Eric Kvam, Purdue associate professor of materials engineering, and Paul Westgate, former Purdue research engineer now with Grace Chemical Co.
In lab tests, both types of grits appear to be natural candidates for use in pressure swing dryers for industrial applications.
"Anyone using the column where we've replaced the desiccant with (modified) corn grits wouldn't know the difference," Ladisch says.
Corn grits also could become part of a system that replaces the ozone-depleting air conditioners that cool and dehumidify homes and cars. The move would make them part of a business that, according to the July 11, 1994, issue of Business Week magazine, brings in $26 billion worldwide.
As a result of the Montreal Protocol on Substances That Deplete the Ozone Layer, which will go into effect in January, manufacturers no longer can make the refrigerants used in many cooling systems. In response, appliance manufacturers and producers of car air conditioners have switched from the chlorofluorocarbons often used in the past to hydrofluorocarbon-134a (HFC-134a), which eats up no ozone. But HFCs also face regulation because they have been declared greenhouse gases.
Manufacturers looking for alternatives to standard air conditioners have started developing systems that use evaporative coolers with desiccators. Evaporative coolers pull hot, dry air through a water spray or wet pad. As the water evaporates, it pulls heat out of the air, just as evaporating sweat cools your skin. Because evaporative coolers don't work where air is already very humid, they have been used only in desert-like climates. Now manufacturers of evaporative coolers are adding desiccators, which dry air with water-adsorbing, inorganic particles similar to those found in industrial pressure swing dryers. With desiccators, evaporative coolers can be used in humid areas.
Desiccant/evaporative cooling systems already are in use in grocery stores in Pennsylvania and Puerto Rico and in a clothing distribution center in Alabama. Compared to standard air conditioners, the systems cost less to run, deliver air that contains fewer microorganisms, and contain no CFCs or HFCs, according to the manufacturer.
Ladisch says he believes that, just as in industrial dryers, grits look like a low-cost, natural substitute for the inorganic desiccants in these new cooling systems.
"We need to do a few more tests," he says, "but scientific evidence suggests they will."
Sources: Michael R. Ladisch (765) 494-7022; Internet, firstname.lastname@example.org
Paul Westgate (410) 531-4705; Internet, email@example.com
Eric Kvam (765) 494-4097, Internet, firstname.lastname@example.org
Writer: Rebecca J. Goetz (765) 494-0461; Internet, email@example.com
Purdue News Service: (765) 494-2096; e-mail, firstname.lastname@example.org
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