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GSI’s TopDry system recycles heat to improve efficiency

System blends grain dryer with temporary storage capacity

Although GSI’s TopDry grain drying and storage system has been on the market since 1986, the features it offers have recently been gaining popularity with North American corn and small grains growers, according to Gary Woodruff, GSI’s conditioning products marketing specialist. Adding computerized controls to the system significantly increased its appeal, he says.

“In the past five to seven years it went from just one of the alternatives we offer to the fastest growing product at GSI,” he says. “This is being driven by several factors, number one is economics. It equals the efficiency of our tower dryer. And the quality is good enough that we actually recommend this dryer for use with white food grade (corn).”

“In the past, the demand for dryers primarily centred around capacity,” he continues. “Efficiency was second. Today, we’re seeing the strongest drive being efficiency.”

“It’s not a new thing in the industry, for sure,” adds Collin Horst of Earl Horst Systems Ltd., a GSI retailer in Elmira, Ontario. “But probably efficiency is the key thing for our customers. Reusing the heat from the hot corn is where you gain the efficiency. As you are cooling the corn the heat is reused.”

The TopDry system houses a dryer in the top part of a 24-, 30- or 36-foot diameter bin, where grain is held in a layer no more than 32 inches deep while it’s dried. When the drying process is completed, the grain drops down to the aeration floor in the bin below. As it cools, the hot air it gives off is recycled and blown back up into the dryer.

“It has a limited grain depth of only 32 inches (while drying),” says Woodruff. “What this does is give you a much lower resistance to air flow and we can use a higher-efficiency 1,750 r.p.m. fan and deliver a lot of air with a relatively low amount of horsepower.”

“The more air (flow) you can get, the higher your drying capacity. Normally, in a grain bin you have six to 21 feet of grain depth, so you have very high static pressures with one to two CFM per bushel of air flow. So you have very low capacities. With a TopDry, you can get as much as 20, up to as high as 60 CFM per bushel, so we can dramatically improve that capacity level compared to a standard bin.”

“In addition to that we drop that warm, dry grain onto the bottom, normal aeration floor of the bin. We aerate and cool that grain and reuse that (warm) aeration air in the drying process (for the next batch). We wind up with a very high capacity, a very high efficiency and a very high quality dry.”

grain aeration graphic

Left: Warm air is blown through a 32-inch layer of damp grain at the roof of the bin. Right: After a batch is dried, it is dropped to the bottom of the bin. Aeration carries the heat it gives off back up to help dry additional batches of damp grain.
photo: Agco

Currently GSI offers two TopDry models. One is batch system, where each dryer batch must be manually loaded after the previous one is completed. The other is the computerized AutoFlow version, which automatically keeps the dryer full, allowing farmers to press on with other harvesting work while the dryer looks after itself.

“With that one (AutoFlow), you are going to run between eight and 15 times the amount of capacity of a conventional bin dryer,” says Woodruff. “It’s a rather dramatic improvement.”

“In a typical bin dryer, we’re lucky to dry 100 to 200 bushels per hour at 10-point removal,” he continues. “Over 24 hours that turns into 2,400 to 4,800 bushels per day. With a 36-foot TopDry, we can dry six or seven batches, which is 10,000 to 12,000 bushels per day. It’s a factor of at least three times more capacity per day in the same diameter bin.”

“When we go to the AutoFlow, the automated version, we reduce the depth of the grain as it moves to the outside of the floor. We don’t have any loading time. At 10 points, that dryer can easily do 35,000 to 40,000 bushels per day.”

The TopDry system is available in bin sizes of 24-, 30- and 36-foot diameters with 20,000 to 32,000 bushel storage capacity, providing a lot of temporary storage in the drying bin.

“This dryer, cost-wise, is very similar to a column dryer, but you get storage below the drying floor, says Horst. “The other luxury it gives you is we can do this system with one elevator, because you can dry until the bottom (aeration bin) is full. Then when you stop combining in the evening, you can transfer (dried grain) using the same leg you use to fill it.”

According to Woodruff, the TopDry system retails between 20 and 25 per cent less than a typical stack tower dryer, and that includes the cost of the bottom aeration bin. †

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Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.

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