High Temperature Bin Drying
Advantages:
Disadvantages:
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Condensation is likely to form along the bin walls so if the last batch of grain to be dried is left in the bin for storage, there can be mold problems along the bin walls.
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Additional storage for wet grain holding is required for Batch-in-Bin Drying.
Batch-in-Bin Drying
The batch-in-bin drying process involves using a bin as a batch dryer. A 3 to 4-foot deep layer of grain is placed in the bin and the fan and heater are started. Typical drying air temperatures are 120 to 160F with airflow rates of 8 to 15 cfm/bushel. Drying begins at the floor and progresses upward. Grain at the floor of the bin becomes excessively dry while the top layer of the batch remains fairly wet. The grain is cooled in the bin after it is dried. Some batch-in-bin dryers hold the grain being dried in a layer near the roof. After the grain is dried it is dropped to the bin floor where it is cooled. As it is moved from the bin, the grain is mixed, and the average moisture content going into final storage should be low enough that mold growth will not be a problem.
A stirring device can be added to provide more uniform drying and moisture content and to increase the capacity of the bin dryer. Research conducted at Iowa State University indicates that with a stirring device there is less than 1 percentage point moisture variation between upper and lower layers of a batch of grain. This research also indicates there is some reduction in resistance to airflow, permitting an increase batch size in the typical bin. Stirring allows depths of up to 7 or 8 feet for corn. There is a tendency for fine materials to migrate to the bin floor as the stirring device is in operation.
Condensation is likely to form on the bin walls. If the last batch of grain to be dried is to be left in the bin for the winter months, air tubes and bin liners have been used to help reduce the problems of mold growth next to the bin wall. Another technique that has shown some benefit is to operate the stirring device next to the wall to provide extra stirring.
Recirculating Bin Dryer
The recirculating bin dryer incorporates a tapered sweep auger which removes grain from the bottom of the bin as it dries. The sweep auger may be controlled by temperature or moisture sensors. When the desired condition is reached, sensors start the sweep auger, which removes a layer of grain. After one complete revolution around the bin, the sweep auger stops until the sensor determines that another layer is dry. This dried grain is redistributed on top of the grain surface. The dried grain will be partially rewet by the moist air coming through the grain, which reduces drying efficiency. After all the grain has been dried, the grain is cooled in the bin. The dried and cooled grain is then moved to storage or may be left in the bin. It is common to dry the last bin full of grain using a continuous flow bin dryer as a recirculating bin dryer.
Continuous Flow Bin Dryer
The continuous flow bin dryer also incorporates a tapered sweep auger which removes grain from the bottom of the bin as it dries, but the grain is moved to a second bin for cooling
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Up to 2 points of moisture may be removed in the cooling bin if dryeration is used. Increasing the grain depth will reduce the airflow rate, cfm, and the drying rate of a continuous flow bin dryer. In a recirculating batch or continuous flow bin dryer, it is the total airflow capacity, cfm, that determines the drying rate, not the airflow rate, cfm/bu.
Other Grain Drying Methods
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