Lecture 5Lecture 5

Grain Drying FundamentalsGrain Drying Fundamentals

The Drying ProcessThe Drying Process

Moisture removed from one point to another at Moisture removed from one point to another at a rate dependant on the difference in water a rate dependant on the difference in water vapor between the two locationsvapor between the two locations

Air passed through the bed of grain will either Air passed through the bed of grain will either gain or lose moisturegain or lose moisture

Air passing through wet grain will gain moistureAir passing through wet grain will gain moisture Airflow rateAirflow rate

Too fast-not as much removedToo fast-not as much removed Too slow- not as much removed Too slow- not as much removed

Drying Zones Drying Zones

Grain does not dry uniformlyGrain does not dry uniformly Especially bin type dryer with low air flowEspecially bin type dryer with low air flow Three ZonesThree Zones

Dried ZoneDried Zone Drying Zone-most potential for dryingDrying Zone-most potential for drying Undried Zone-rewetting zone, condensation Undried Zone-rewetting zone, condensation

occurs hereoccurs here

Developing a Uniform Developing a Uniform drying frontdrying front

Uniform air flowUniform air flow Parallel air flowParallel air flow

Drying CalculationsDrying Calculations

Size of binSize of bin Rating of fanRating of fan Moisture of grain currently & desiredMoisture of grain currently & desired Temp of drying airTemp of drying air RH of drying airRH of drying air

Size Groupings of Drying Size Groupings of Drying SystemsSystems

Low CapacityLow Capacity Less than 10,000 bushel/yr & 500 bu/dayLess than 10,000 bushel/yr & 500 bu/day

Medium CapacityMedium Capacity 10,000-30,000 bu/yr & 500-1500 bu/day10,000-30,000 bu/yr & 500-1500 bu/day

High CapacityHigh Capacity More than 30,000 bu/yr & 1,500 bu/dayMore than 30,000 bu/yr & 1,500 bu/day

Natural Air DryingNatural Air Drying

Only energy required is that to run the fanOnly energy required is that to run the fan Occurs if RH allow a net moisture transferOccurs if RH allow a net moisture transfer Equipment NeededEquipment Needed

Perforate floor & fanspreader, sweep augerPerforate floor & fanspreader, sweep auger Stirring devices are not neededStirring devices are not needed Portable auger-sized to handle harvest needsPortable auger-sized to handle harvest needs At least 500 bu capacity/hrAt least 500 bu capacity/hr

Natural Air DryingNatural Air Drying

AdvantagesAdvantages Most energy efficientMost energy efficient Low CostLow Cost Move grain only one Move grain only one

time ( usually) time ( usually)

DisadvantagesDisadvantages Slowest methodSlowest method Greatest potential for Greatest potential for

spoilagespoilage Highest level of Highest level of

managementmanagement More time needed for More time needed for

inspection spoilageinspection spoilage Insect problemsInsect problems

Other factors of Natural Other factors of Natural DryingDrying

Rate of drying directly related to the Rate of drying directly related to the airflow delivered & the RHairflow delivered & the RH

Quantity of grain may effect air flowQuantity of grain may effect air flow Depth of grainDepth of grain Dockage of grainDockage of grain Settling of grainSettling of grain

Concerns with fansConcerns with fans

Fans of same Hp are not always capable of Fans of same Hp are not always capable of same air flowsame air flow

Doubling air flow increases energy Doubling air flow increases energy requirements by 5 timesrequirements by 5 times

Systems have limited auxiliary drying capacity Systems have limited auxiliary drying capacity May require you to partially dry in the fall & May require you to partially dry in the fall &

complete drying in the springcomplete drying in the spring Maximize efficiency by adding layers, & Maximize efficiency by adding layers, &

watching grain tempwatching grain temp