Grain Dryer Exhaust Air Recycling System For Farm Fans Inc. AB-Series Grain Dryers By: Tony Wagner 1
Grain Drying Introduction Why dry grain? Must be dried before storage to prevent spoilage Eliminates pay cuts from elevator who MUST store the corn 2
Grain Drying Introduction Grain Dryer Types Tower Dryers Column Dryers 1. Continuous Flow 2. Automatic Batch 3
Grain Drying Introduction Column Grain Dryer Key Components 3. Loading Auger 6. Grain Column 8. Plenum 19. Control Box (thermostats, relays etc ) 20. LP Burners 23. 15 hp Axial fan 4
Grain Drying Introduction How it works 1. Cold ambient air drawn into fan 2. Passes through burner 3. Maintains Plenum Air Temperature at 200 F 4. Hot air passes through corn, thus withdrawing moisture 5
Grain Drying Introduction How it works 5. Hot air/steam exit to atmosphere This hot air and steam is what I will be trying to utilize. 6
Project Objective To create a system capable of decreasing the amount of fuel required to keep plenum air temperature at 200 F without significant energy input to the drying operation Specifically for my Dad s FFI AB-250 Dryer, but could be further developed for other dryers later on 7
Drying Parameters Farm Fans Inc. (FFI) AB-250 Specifications Automatic Batch Column Dryer Grain Capacity: 250 bushels Intake Flow Rate: 22250 CFM Plenum Pressure: 1psi Maximum Heating Capacity: 4.6 million Btu/Hr=(1800hp) Propane: 91500 Btu/gal Burner Efficiency: 90% Plenum Operating Temp: 200 F Typical Fall Ambient Temperatures: 25 to 70 F Fuel: Liquid Propane up to 49 gal/hour 8
Drying Parameters Moisture Content and Drying Times Drying Time is based on moisture content of corn Moisture Content Drying Time (minutes) Moisture content is on a percent by weight basis Must be dried to 15% moisture by weight before storage 22% field moisture is common for a normal season 20 30 22 40 25 60 30+ 90+ 30%+ field moisture was common this past season 9
Motivation Energy Requirements (typical situation) 22% field moisture corn, 35 F day Mass of air sent through plenum: m=q*t*ρ m=22250 cfm*40 mins*.079 lb/ft^3=70310 lbs of air Energy required to heat that air: E=m*cp*ΔT E=70310lb*(.241Btu/lb* F)*165 F*1.10=3.1 million Btu *For one load of corn only!! 10
Motivation Now, increase intake air temp by just 10 22% field moisture corn, 35 F day, 45 intake temp Mass of air sent through plenum: m=q*t*ρ m=22250 cfm*40 mins*.079 lb/ft^3=70310 lbs of air Energy required to heat that air: E=m*cp*ΔT E=70310lb*(.241Btu/lb* F)*155 F*1.10=2.9 million Btu *For one load of corn only!! 11
Motivation 200000 Btu is about 2.2 gallons of propane @2.50/gallon A simple 10 temperature increase can save $5.50/load A typical season produces about 75 loads Seasonal savings of $400 12
Motivation 4000 Fuel Costs Saved in One Harvest Season 30 minute runtime 3500 Fuel Costs Saved ($) 3000 2500 2000 1500 1000 500 54, 718.4555716 25 35 45 55 0 0 20 40 60 80 100 120 Intake Air Temperature ( F) 13
Motivation 6000 Fuel Costs Saved in One Harvest Season 40 minute runtime 5000 Fuel Costs Saved ($) 4000 3000 2000 1000 54, 957.9316793 25 35 45 55 0 0 20 40 60 80 100 120 140 Intake Air Temperature ( F) 14
Motivation 8000 Fuel Costs Saved in One Harvest Season 60 minute runtime 7000 Fuel Costs Saved ($) 6000 5000 4000 3000 2000 1000 54, 1436.897519 25 35 45 55 0 0 20 40 60 80 100 120 140 Intake Air Temperature ( F) 15
Motivation 12000 Fuel Costs Saved in One Harvest Season 90 minute runtime 10000 Fuel Costs Saved ($) 8000 6000 4000 2000 54, 2155.339466 25 35 45 55 0 0 20 40 60 80 100 120 140 Intake Air Temperature ( F) 16
Feasibility Discharge Air Temp: about 125 F Whether or not that heat can be transferred to intake air is yet to be determined (a main topic of next presentation surely) 17
Requirements Cost: Must be able to be paid for by the user in 3 years to be considered a viable investment to the farmer In this case cost to the user should be below $1200-1500 Must be built within dimensions of existing pole shed which houses the dryer No moisture can condense onto the dryer causes premature rust and would impair the drying process Cannot restrict air intake of fan fan venturi are designed to maximize efficiency Must be able to allow ambient air into fan for cooling cycle 18
Concepts Collect hot air, send it through an air dryer, then back to the intake Directly heat ambient air using electric heating elements Pass cold air through radiator which has hot moist air passing over it Collect hot air, pass over water tank (heat sink), pump hot water through pipes that run through intake air Draw in ambient air mixed with hot air Draw ambient air into fan by passing it across partition wall between hot and cold air discharge air Collect air only from 20 minute cooling cycle, then store that air for initial heating of next batch 19
Next steps Begin modeling dryer to model recycling system around Further development/consideration of each concept Cost Effectiveness Power consumption Final Critique/scoring of each concept Concept Selection (March 15 th ) 20