Closed Loop Fumigation of a
Concrete Elevator
Broken Arrow, Oklahoma
Dr. Carol Jones
Department of Biosystems and Agricultural Engineering
Oklahoma State University
Edmond Bonjour and Randy Beeby
Stored Products Research and Education Center
Department of Entomology and Plant Pathology
Oklahoma State University
Mark Fultz, Manager
Hansen Mueller Grain Co., Broken Arrow, Oklahoma
Urbanization around Rural Elevator
Challenges
• Fumigation safety is a concern to neighbors
and to employees
• Conventional methods of phosphine
fumigation put workers and people in close
proximity in danger
• Improper fumigation leads to insect resistance
Goals of this Project
• Seek a method to improve safety of fumigating
with phosphine
• Seek a method to decrease the amount of
fumigant required
• Seek a method to increase the concentration
distribution throughout the grain bins
Common Fumigation Methods
and Negative Effects
• Probe and Tarp: exposure during tarping
• Automatic Dispenser: pellets spill from buckets and
release gas in unwanted areas, shrinkage caused
from turning and moving grain
• Gravity Fumigation: little control of where gas may
go
Each method offers increased risk of exposure during
insertion of fumigant into the grain.
Proposed Method
• Closed Loop Fumigation System in a concrete silo
• Example of a J-System patented by James Cook in
1980.
• Consists of:
– Sealing air leaks in storage structure
– Installing low pressure low volume centrifugal blower recirculating air-gas mixture from headspace of grain into
base of silo
– Installing pipes from fan to blower and back into silos
Closed Loop Basic Idea
Pressured base ducts force gas mixture upward
through grain bulk providing better gas distribution
through grain.
Headspace
Grain Bulk
Blower
Bin Diagram of Elevator Facility
#10
#1
#11
#3
#2
#12
#13
#9
#8
#14
#4
#15
#7
#5
#6
#16
#17
Closed loop system installed in one half of the
elevator while the other half remained
unchanged for a conventional method fumigant
application
CLF
#10
#1
Conventional
#11
#3
#2
#12
8660 MT
capacity
#13
#9
#8
#14
#4
#15
(120,000 bu)
#7
#5
#6
#16
#17
Dosage: Phosphine Pellets
• Manager chose his normal dosage rate of 500
pellets/1000 ft3 which is his normal dosage rate.
Both sides of the elevator were treated the same.
– CLF side: pellets distributed on top of the grain.
– Conventional side: pellets were inserted into the grain as it
was loaded into the bin
Monitoring
• Monitoring fumigation: top, bottom, and middle of bin
Monitoring
• Electronic gas meters were used to measure
phosphine concentration every 4 hours for the first
32 hours and every 10 hours for the next 88 hours.
Results
CLF versus Conventional Fumigation
2500
CLF BIN
2000
ppm
1500
1000
CONVENTIONAL
BIN
500
200 PPM
0
0
10
20
30
40
50
Hour from Treatm ent
60
70
80
A closed loop system was installed in one half
of the elevator while the other half remained
unchanged for a conventional method fumigant
application
CLF
#10
#1
Conventional
#11
#3
#2
#12
8660 MT
capacity
#13
#9
#8
#14
#4
#15
(120,000 bu)
#7
#5
#6
#16
#17
Installation of CLF
Bin Diagram of Elevator Facility
Seal Inner Vents
#10
#1
#11
#3
#2
#12
#13
#9
#8
#14
#4
#15
#7
#5
#6
#16
#17
Installation of CLF
• Seal silos as completely as possible…inner vents to
silos not included in loop
Installation of CLF
Bin Diagram of Elevator Facility
Seal Outer Vents
#10
#1
#11
#3
#2
#12
#13
#9
#8
#14
#4
#15
#7
#5
#6
#16
#17
Installation of CLF
• Seal silos as completely as possible…outer
vents
Installation of CLF
• Seal silos as completely as possible...access
openings
Proposed Method for Study
Bin Diagram of Elevator Facility
#10
#1
Headhouse
#11
#3
#2
#12
#13
#9
#8
#14
#4
#15
#7
#5
#6
#16
#17
Install Fan on
top of Bin 6
(outside of
head house)
Proposed Method for Study
• Blower mounted outside on top of one bin adjacent
to the head house.
• 1/3 HP supplying 320 cfm
Proposed Method for Study
• Installing pipes from fan to blower and back into silos
Down man lift shaft to ground level
using 3 inch PVC sewage pipe
Flexible hose from fan through
window to man lift shaft
Proposed Method for Study
• Installing pipes from fan to blower and back into silos
After Fumigation
• Blower discharge piping was disconnected and the
blower was used to evacuate the fumigant from the
CLF system and bins.
• Evacuation can be accomplished when the danger to
workers or to residents around the elevator is the
least.
• Gas can be discharged 120 ft. above ground level
reducing danger
• Closed Loop Fumigation
–
–
–
–
Installation costs
Less fumigant
Less labor
Less worker exposure and
health costs
• Conventional Fumigation
– Turning costs and product
shrinkage
– More fumigant
– More labor
– More bin entry required of
workers causing health
risk and higher insurance
rates
Economic Comparison ($4/bu wheat)
Economic Comparison ($8/bu wheat)
Conclusion
• Closed loop fumigation was more successful
since it reached the desired 200 ppm for 100
hours. Conventional fumigation did not reach this
level.
• ¾ of the fumigant could have been saved in this
elevator
• Closed loop fumigation is ultimately cheaper
• Closed loop fumigation is safer than conventional
fumigation when carried out properly
Closed Loop Fumigation of a
Concrete Elevator
Broken Arrow, Oklahoma
Dr. Carol Jones
Department of Biosystems and Agricultural Engineering
Oklahoma State University
Edmond Bonjour and Randy Beeby
Stored Products Research and Education Center
Department of Entomology and Plant Pathology
Oklahoma State University
Mark Fultz, Manager
Hansen MuellerGrain Co., Broken Arrow, Oklahoma