A model-based fan and burner control strategy for the in-bin drying and conditioning of corn
Three different corn types (yellow dent, waxy and white) were used in a set of desorption and adsorption equilibrium moisture content (EMC) experiments. The ranges of temperature and moisture content (MC) for the tests were 0 to 25°C and 12 to 20%. The main conclusion was that the three corn types investigated had different adsorption and desorption EMC relationships. These corn type specific relationships were incorporated into a new model-based fan and burner control strategy for the in-bin drying and conditioning of corn. This Self-Adapting Variable Heat (SAVH) strategy incorporated the Thompson equilibrium drying model to predict MC changes in different layers of the grain mass. The drying model allowed the SAVH control strategy to successfully identify wet or dry weather conditions and target a uniform final MC for the entire grain mass. ^ This SAVH control strategy was successfully implemented in three field experiments during the 2004 drying season. The Post-Harvest Aeration and Storage Simulation Tool–Finite Difference Method (PHAST-FDM) software was further refined and validated by comparing the observed MC values for four natural air/low temperature (NA/LT) in-bin drying experiments with the predicted MC values. ^ On the basis of a 40-year analysis of weather data with respect to the performance of NA/LT in-bin drying systems, the Midwestern Corn Belt was divided into four regions. PHAST-FDM was used to study the performance of four NA/LT in-bin drying strategies for drying 20% initial.^ On the basis of a 40-year analysis of weather data with respect to the performance of NA/LT in-bin drying systems, the Midwestern Corn Belt was divided into four regions. PHAST-FDM was used to study the performance of four NA/LT in-bin drying strategies for drying 20% initial MC corn in 13 locations within these regions. The simulation results showed that the SAVH strategy outperformed the other strategies on the basis of drying costs (from 1.1 to 9.6 $/t lower drying cost), drying time, and relatively little overdrying of the grain bottom layer. The drying cost for the yellow dent corn type was always the lowest, followed by the white and then by the waxy corn types. ^ The fine material distribution in the grain mass and the air velocity through the core and periphery locations in the bin were quantified for 15 NA/LT in-bin drying field tests. The best management practices of leveling the grain peak after filling the bin and coring the grain mass were implemented, and the improvement on the airflow distribution was quantified. Simulation results showed that operators of NA/LT in-bin drying systems could reduce drying costs from 25 to 33% by leveling the grain peak after loading the bin. An additional savings of 18 to 22% could be achieved by installing effective grain (and fine material) distributors or by coring the grain mass. ^
Dirk E. Maier, Purdue University.