GEK Wiki / Exploring Hopper Mass Flow
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Exploring Hopper Mass Flow

Page history last edited by bk 10 years, 7 months ago

Summary

A series of tests were conducted to determine means to avoid bridging and other problems in the drying bucket and hopper. Shaking of wood chips prior to running a test was shown to settle it into a form that consistently bridged. This indicates that vibration of a hopper is useful when an arch or rathole has occurred, but can be detrimental to flow if it consolidates material. "Chisel" and conical funnel inserts inside the hopper and drying bucket greatly reduced bridging and ratholing problems. Mass flow of wood chips with a 2" auger was around 50 kg/hr or roughly 37 kW output (above the theoretical limit of 25 kW within the standard GEK form factor).

 

The current standard 2" helical auger required and average of 1-1.5 A at 12-13V while moving material. A double flighted design with a 3" flight around the 2" auger required an average of 3A at 12-13V with occassional excursions past 8 A. The double flighted auger did increase mass flow rate, although the motor didn't sound as "happy". A 10 A breaker was used and only reset when a weld broke on the double flighted auger causing auger binding against a wall.

 

Results

Results from Drying Bucket Tests on Softwood Chips

Drying Bucket Insert
Material Settled/Tamped
Auger Diameter
Bridging
Mass Flow Rate [kg/hr]
None
No
2"
0 of 3 tests
ND
None
Yes
2"
3 of 3 tests ND
Chisel + Channel
Yes
2"
0 of 3 tests 45-60
Chisel + Channel Yes 2" + 3" 0 of 3 tests 75-95
None Yes 2" + 3" 0 of 1 tests 65

 

Results from Drying Bucket and Hopper Tests

Material Drying Bucket Insert
Hopper Insert Auger Diameter
Bridging
Mass Flow Rate [kg/hr]
Pellets None
None 2"
0 of 1 tests
350
Screened Softwood Chips None
? 2"
1 of 1 tests 50

 

Screened Softwood Chips

Chisel + Channel
5" H Cone 2"
0 of 3 tests 55

 

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