Finding ways to maximize grain drying efficiency

Despite higher commodity prices, growers are being encouraged to examine their costs across all facets of their farming operations.

The impact of higher drying costs was the focus of a presentation during the first day of the Innovative Farmers Association of Ontario (IFAO) annual conference, held in London last month.

Drying charges have become a focal point for many growers with on-farm storage units. According to an Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) Field Crop Budget for grain corn in 2022, drying accounts for roughly 15 per cent of the cost of producing corn –third highest behind fertilizer (30 per cent) and seed (18 per cent).

All the more reason, said James Dyck, engineering specialist with OMAFRA, for optimizing existing grain dryers for energy savings.

The key points he made referred to measuring a dryer’s energy usage, optimizing the burner, increasing the plenum temperature, adding insulation, improving the heat exchanger and considering the use of hybrid systems.

With the grain dryer’s energy usage, Dyck noted that the dollar amounts and energy numbers don’t always go up at the same rate: the best way to measure energy usage is to calculate dryer energy use based on bushels dried and water removed. The resulting BTU per pound figure indicates the energy efficiency of the dryer and the lower the number (e.g. 2,000 BTU/lb), the more efficient it is.

In order to optimize the burner, a grower needs to calculate the optimal air:fuel ratios, and that may require the help of a professional. A natural gas burner should have a 10 or 11:1 ratio while a propane burner’s ratio should be 25 or 26:1.

“By fine-tuning your burner and the amount of air going to the burner, you can save up to 12 per cent energy and that comes from an Alberta study last year, and what they found looking at a number of different dryers,” said Dyck.

Increasing the plenum temperature is an easy adjustment but the trick is to do it slowly – by 5 C at a time. Dry a full batch, carefully inspect the grain and if the quality is good, increase it another 5 C. Repeat that if it works but if the quality is down, drop it by 5 C.

Next on Dyck’s list was adding insulation and he cited an example of a burner that uses 8.0 million BTUs per hour at 160 F (71 C). A 36-foot tall, 42-inch square duct will have an estimated heat loss through the duct wall of 187,000 BTU per hour – a 2.3 per cent loss per burner – or $936 per month with natural gas (based on 5.2 m3 per hour at $0.25 per m3).

With propane, the loss is equivalent to $4,212 per month (based on 7.8 litres per hour at $0.75 per litre).

Another option is to put in a new heat exchanger, which could save upwards of 40 per cent. It’s capturing the air coming off the bottom of the dryer and circulating it back into the system. Since the air’s already heated, it will take less energy to raise the temperature.

The hybrid system was the final part of Dyck’s presentation and he cited a study from Purdue University which found savings of 10 to 30 per cent of energy costs when using a “combination” dryer (see table below).

Instead of running a dryer hot and then cooling the grain in the dryer, a manager can pull the grain out while it’s still hot. Doing this leaves the grain a little wetter than normal because you’re going to transfer it to a bin and let it sit for four to 12 hours, allowing the hot grain to “steep”.

“By doing that the heat that’s left in the grain will force the remaining moisture in the grain out into the air within the bin,” said Dyck, noting this system is worth considering.

“Then you turn on the fans and it will blow all of that humid air out of the bin.”

It’s more complicated to manage and you need to be “hands-on” with the dryer system, but it’s possible to save money and increase capacity, he said.

– Read more on this topic from Ralph Pearce at Country Guide.