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Turn up the heat on aeration fans when drying canola

Some growers grappling with a late harvest and high-moisture crops in 2016 added supplemental heaters to their aeration fans. This grower’s experience may inspire an upgrade to aeration setups for 2017

Things were a little off with Harvest 2016 and Chad Bown was desperate. The farmer from Ranfurly, Alta., was combining 14 per cent moisture canola in late November after a month or more of snow delays.

Delivery locations were full, so on-farm storage was his only option. But aeration fans blowing cool air could not dry that damp canola to a safe nine per cent moisture level. So Bown paid $1,500 to $1,800 each for propane-fueled heaters for three hopper bins.

Aeration fan makers offer natural gas, propane or electric heaters that bolt to the aeration fans. Bown’s dad has an electric model, but Bown says that with more than one electric heater per yard, the power draw can start tripping breakers.

Bown’s three bin-fan setups were each different. The first was a Meridian 4,000-bushel smooth-sided bin with five-hp centrifugal fan. On that bin he put a heater rated at 100,000 British thermal units (BTU). The second was a 15-foot diameter Goebel 3,000-bushel corrugated-steel hopper with three-hp axial fan. It got a 60,000-BTU heater. The third was an “ancient” — his word — corrugated hopper with a 19-foot diameter and 3,600-bushel capacity. For this one, Bown had the three-hp fan and 100,000-BTU heater on the ground with a heavy-duty flexible “sock” — he paid $270 for a 12-footer of good quality — connecting them to the bin inlet. For all three, he used a soil temperature gauge shoved into the bin inlet to monitor incoming air temperature.

For all three setups, he had the heater between the fan and the bin. This fan-heater-bin sequence is recommended for canola. Grain Guard aeration engineer Imre Varro says the heater could go before or “upstream” of the fan when drying large-seeded grain such as corn and peas, which provide lots of room around the seeds for airflow.

“But with small-seeded and therefore high static pressure grains like canola, airflow into the bin can be so restricted that the fan can’t suck heat away fast enough. So the flame in a high-BTU heater can stretch out enough to damage the fan,” Varro says. That is why having the heater after the fan is better for canola.

It became obvious to Bown that the Goebel combo — the tall, narrow bin shape and smaller fan and heater — was “by far” the worst for drying, he says. “I had the bin nearly full and the fan was struggling to push air though that amount of grain depth,” he says. “And propane heaters for this kind of extreme moisture drying should be no less than 100,000 BTU for 3,000-bushel or bigger bins. The 60,000-BTU heaters just don’t cut it.”

Recommendations

Taking some grain out of the Goebel bin would have helped, as Bown concluded later. Running bins less than right full is just one of Joy Agnew’s recommendations when adding supplemental heat to an aeration system.

Agnew is a grain storage researcher with Prairie Agricultural Machinery Institute (PAMI) in Humboldt, Sask. Last fall, she put together these recommendations to improve results and reduce risk when using supplemental heat:

  • Air entering the bin needs to be at least 10 C to have good drying potential.
  • Air warmer than 10 C will dry grain faster, but in cold conditions, don’t heat incoming air above 20 C. “The reason for the maximum temperature increase,” Agnew says, “is to minimize the risk of condensation and freezing at the edge of the bin. With air in the grain more than 30 C warmer than the ambient air, this increases the chances of condensation and grain freezing to the edge of the bin.”
  • Use a fan which provides airflow of at least 0.75 cubic feet per minute (cfm) per bushel when adding supplemental heat. While airflow of 0.1 to 0.2 cfm/bu. is adequate to cool a bin of canola, with added heat this low airflow rate could put grain at greater risk because it could take a week or more to push the drying front through a bin. With warm and very moist air creeping so slowly, spoilage could have enough time to start before the front moved on, Agnew says.
  • Under-fill the bin and level the cone to improve airflow throughout.
  • Ensure adequate ventilation at the top of the bin to allow moist air to escape.
  • Turn the bulk frequently. Remove at least one third out the bottom and auger it back on top.
  • Monitor diligently.

Like Agnew, Varro also recommends a minimum of 10 C air for drying. He adds that canola is safer if dried at a cooler temperature for longer rather than a high temperature for shorter. He also says to cool the grain quickly when drying is done.

Then he adds an important caveat. “These rules are not cast in stone and the experience will not be the same for everybody,” Varro says. “We find a lot of guys trying different things. Some have success doing things we don’t recommend and others have no success doing things we do recommend.” Thus, “monitor diligently” is an essential ongoing part of the process.

Bown’s experience

It was while drying his first bin — the Meridian — that Bown started to tweak the recommendations to suit his high moisture and cold air situation. He had it filled right to the top.

“The moisture front froze about halfway up due to low inlet temperature and too much canola in the bin,” he says. So he cranked up his high-powered heaters and warmed the cold air by 40 degrees — shooting 30 C air into the bin. Even at that, it took him 12 days to dry that first bin to below nine per cent moisture. “But if I didn’t do that, I would still be drying the canola two months later.”

Bown dried three more bins through December — one batch for each bin. He didn’t fill the bins right full this second time. He also turned off the fans and heaters on days below minus 10 C because “it was a losing battle at that point,” he says.

As recommended, he turned the bins fairly regularly — cycling out a 1,500-bushel semi-load every few days to get a moisture reading and check the condition. He re-binned each load into the top of the same bin. Cycling is especially important for the Meridian bin with the rocket aeration system. The rocket doesn’t dry the cone, he says, “so it’s imperative to cycle these type of bins.”

Cold conditions kept adding challenges throughout the ordeal. With all the moisture inside the bin, canola froze to the side walls, as Agnew suggests could happen. Bown estimates about 25 bushels stuck to the corrugated bin walls and 100 bushels stuck to the smooth wall. And he had a bit of panic when a truck came to pick up canola six days after drying ended and he couldn’t get the bin hatch open. It was frozen shut. A four-foot pry bar couldn’t budge it. So he used an old stove pipe to focus heat from a tiger torch. When it finally opened, the thawed canola above the hatch left a pool of melted “canola juice” on the ground, he says.

Hoping next time will be different

Bown says one improvement for next time would be better ventilation. Neighbours in the same boat stuck hog barn ventilation fans on the top hatches to evacuate the moist air faster.

“When I crawled up the ladder to check the tops of my bins, it was basically a rainforest. I could actually see water vapour condense and run back down the bin walls,” he says. On the corrugated hoppers, so much moist air escaped through seams on the bin walls that ice and icicles formed all around the outside. “They looked like ice castles.”

Bown would also prefer centrifugal fans on all bins. “I will never buy another round axial fan for hopper bins,” he says. Upgraded heaters with more options — including temperature gauges, thermostats and timers, and control settings that adjust to the ambient outside air temperature — would be a bonus. “As long as the whole package isn’t insanely expensive, I can see value in a fully loaded heater since it would reduce my babysitting time,” he says.

And, if he has the choice, he’ll dry only on days above freezing. This would limit icicles on the outside and grain frozen to inside walls, and hopefully bypass the frozen hatches.

Was it worth it?

Bown used 675 litres of propane per bin at an average of 33 cents per litre. It worked out to around six cents per bushel for propane.

But propane is just part of the overall cost. When adding electricity for fans plus equipment costs (augers, trucks, tractor and diesel) and his time, total drying costs were around 50 cents per bushel.

“In the end, I might have been further ahead just selling high-moisture grain and taking the loss — but that wasn’t really a choice we had,” Bown says. By the time he started combining, the elevators were all full.

“So we tried to make the best of a lot of bad situations. Everything worked out — all the dried canola went No. 1 — but it was a lot of extra work.”

Jay Whetter is communications manager for the Canola Council of Canada. This article originally appeared on Country Guide.

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Comments

  • biglentil

    Never could get my Grain guard to function properly even with a half full bin. Manufacturer of no help, save your money.