TOM HAGEDORN, an industrial engineer, was on the way to Burlington, Iowa, a year ago last April when he heard the news on his car radio: Six of the 12 concrete storage bins at the Burlington grain elevator had blown up and the area was a raging inferno. The blast was compared to the impact of a 2,000-pound bomb. Mr. Hagedorn changed direction and headed home to Holts Summit, Mo. There would be no one available to speak to him at the grain elevator that day. Ironically, his briefcase contained plans for a recently developed system of dust control, using ``white'' oil, that would eliminate the kind of disaster that had just occurred.
In grain elevators, airborne dust, particularly cornstarch, which results from the breakdown of the kernels during storage, can be even more explosive at certain concentrations than coal dust. A spark from a motor, static electricity, or simple friction on a gear or pulley belt can set off an explosion.
Over the years, dust explosions have been considered an inevitable risk associated with the grain-storage industry, similar to the risks in driving a truck carrying high explosives. Most times nothing happens, but occasionally everything erupts. Some 200 explosions have occurred in the United States since grain silos began appearing early in the century, most recently in Joliet, Ill., April 22, where a natural gas explosion is thought to have been triggered by a smaller dust explosion.
Until recently, the only approved technology to remove the explosive dust - pneumatic ``aspiration'' or vacuuming - was often resisted by industry because of a slight grain weight loss (removal of the edible dust) plus the high capital costs of installing the system. Then in 1983 the government approved the use of two oils - food grade ``white'' oil and soybean oil - as a dust suppressant, and the way opened for a less costly and, proponents say, more effective system for controlling dust.
Some 10 percent of the nation's 14,000 elevators now use the oil-based system. Many more are expected to adopt the approach, spurred on by an Occupational Safety and Health Administration regulation requiring grain elevator operators to control in-house dust levels. That regulation took effect May 1.
While critics charge it is ineffective because its provisions can be complied with by periodically sweeping the floor with a broom, the oil-based system is expected to gain ready acceptance as the technology becomes better known.
The system requires that an ultra-fine coating of oil cover the grain, so dust adheres to the kernels, where it forms no explosive threat at all.
White oil is derived from conventional petroleum but is purified several times over to remove all sulfur, nitrogen, oxygen, benzine, and other undesirable elements until it becomes a transparent, tasteless, food-grade oil. Soybean oil, as the name implies, is a vegetable oil derived from soybeans.
Developers of the dust-suppressant system say it is far less expensive to install (10 percent, down in some cases to as little as 1 percent of the cost of the vacuum systems), that it requires much less energy to operate, and eliminates a disposal problem (what to do with the dust). Also, the oil provides a small measure of insect repellancy. But the most important reason, Amoco researcher Dr. Roger Reuff says, is that oil ``has proven to be extremely effective'' at controlling dust.
Some concerns have been voiced about the oil's possible influence on the grain during further processing. Would it affect the taste of your breakfast cornflakes, for example. ``No,'' says Tom Hagedorn, who points out that adding 1/100th to 1/50th of a percentage point to a grain that is already 12 percent corn oil ``is so negligible that it can't be found.'' For their part, soybeans are 16 percent oil. In addition Hagedorn points out that with many grains most of the suppressant is removed with the chaff.
The application of excessive amounts of oil would almost certainly affect further processing. Flour milling machinery could become plugged by oily flour. But, says Hagedorn, ``controlling the spray so that it is on while the grain is falling, and off the moment it stops, involves extremely simple control equipment.''
David Krejci, executive vice-president of the Grain Elevator and Processors' Association, concurs. ``You don't need highly sophisticated equipment for proper control of oil spread.'' But he remains cautious. A record system needs to be developed so that grain sprayed at one elevator would not be resprayed when transferred to a second elevator.
Meanwhile, the ``barley and malt people won't touch it [the oil suppressant system],'' Mr. Krejci says. ``They are afraid it will alter the flavor of their beer.''
Overall, however, the grain industry is showing interest.
``We're optimistic, but we stress cautious appraisal,'' Krejci says. ``We don't want to solve one problem at the expense of another. In the lab it works great, but we want more real world experience,'' before the association will endorse the process without reservations. Reports from the baking industry are mixed. Some say the oil improves the end product, others say it makes the flour more difficult to handle.
While it is still being appraised, proponents are confident it will gain increasing acceptance in the next few years and that it will dramatically reduce the frequency of explosions in a country where towering grain elevators are more commonplace than anywhere else in the world.