The Prairie Agricultural Machinery Institute (PAMI) has a number of recommendations to help minimize the risk of spoilage in grain bins.
The following information comes from a September 20th PAMI news release.
“We know producers are very concerned about the moisture content of their crops going into the bin, said Dr. Joy Agnew, project manager of Agricultural Research Services at PAMI. This has been an area of much research at PAMI and although some of our multi-year projects are still ongoing, the data we have already collected on the use of heat in grain drying can be used by producers to minimize losses in wet years like this.”
Adding supplemental heat to natural air drying involves two basic steps, she said. The first is to use the heat to draw moisture out of the grain and into the air that is in the pockets between kernels, and then use moderate airflow rates to move that moist air out of the bin.
“ A lot of our research has centered on wheat and canola but the physics apply across the board to any crop, said Agnew. For every 10° C you can increase the temperature of the air going into the bin, you cut the relative humidity in half. That means you can turn a cold, miserable, drizzly day into perfect drying weather.”
The following are some basic recommendations for improving results and reducing risk when storing wet grain.
1. The air moving through the bin needs to be at least 10-15° C for optimal drying potential and should not exceed 20-30° C to avoid high grain temperatures that can initiate spoilage.
2. Use a fan with an airflow rate of at least 0.75 cubic feet per minute (CFM) per bushel. Anything lower could result in heating of the grain, which can initiate spoilage. And, the higher the temperature increase of the air going into the bin, the more CFMs are required. With supplemental heating, hotter air is not necessarily better as you need to match your target temperature with your fan capacity. If you don t know your fan capacity (CFM per bushel), go to pami.ca/storage to learn how to measure or estimate your airflow.
3. Ensure there is adequate ventilation at the top of the bin to allow moist air to escape. That means one square foot of ventilation space per 1,000 CFM. Some bin and fan manufacturers are producing fans specifically designed to move air out of the tops of bins.
4. Rotate the bin contents frequently (every few days) by removing at least one-third from the bottom and auguring it back in the top.
5. Monitor the conditions in the bin. Ideally, the moisture content should be monitored but, at a minimum, monitor the temperature in the bin. When using supplemental heat, the drying rate is considerably faster than with no heat, so keep a close eye on grain conditions to prevent over-drying.
6. The size of the heater should be based on the desired temperature increase (which depends on the ambient temperature and the target temperature) and the airflow rate from the fan, keeping in mind the minimum air flow rate of 0.75 CFM per bushel.
7. Consider investing in thermostatic controls for heaters. The more consistent the air temperature going into the bin, the more effective the drying will be.
8. Heat transfer efficiency is important. Properly designed systems that are appropriate for the bins and fans are best, and setting up the system properly is key to efficiency and effectiveness.
9. The target temperatures mentioned above are valid for the fall season but when the outside temperature drops below about -5° C, the temperature of air going into the bin should be reduced to prevent damp grain from freezing to the sides of the steel bin.
10. When the grain is almost dry, turn off the heat and cool the grain to below 15° C. Cooling the grain will result in some additional moisture removal (ranging from approximately 0.5% to 2%).
Agnew cautioned producers to use care hooking up heating and electrical systems to grain bins as they pose potential safety risks. She also noted that the main difference among the heating options (propane, natural gas, indirect hydronic, etc.) is operating cost and ease of use. Direct fired heating systems do add moisture to the air entering the bin, but the amount of water added is negligible compared to the water being removed from the bin.
PAMI’s on-going research on this topic will better define the minimum airflow rates for use with supplemental heating, the drying rates with different target temperatures, and the energy efficiency and operating costs of different supplemental heating systems. Interim results will be available in 2019 and the study wraps up in 2020. This research is funded by SaskWheat and SaskCanola.
More information on crop storage can be found at pami.ca/storage