Retted Switchgrass Fireballs
Jeff Davis, September 10,2006
Note: Click on image to enlarge.
These fireballs are made from retted switchgrass with some waste vegtable oil (WVO) added. As can be seen in the above picture they burn well in the inverted down draft gasifier thus the Woodgas Camp Stove.
The non-WVO switchgass fireballs (dry, no oil) did not burn well in this stove. They burned somewhat like charcoal fireballs. First lots of smoke then after the smoke cleared there was the charcoal like glow for about ten minutes. This smokey burn can be seen in picture 1. Also, they did not put out much heat. This provoked me to explore enriching them with WVO. Picture 11 shows a WVO enriched fireball (left) and a dry fireball (right).
My WVO is not exactly WVO, its stale cooking oil that I had for a few years. It might be corn oil, the label fell off some time ago. But in this article I refer to it as WVO.
Below in table 3 you will find the data concerning the burn/boil test. Also, in picture 7 you can see the boiling. Picture 2 is the fuel.
|water @ start||800g|
|water remaining after boil||126.1g|
|water boiled away||673.9g|
|start to boil||~ 4 min.|
|boil time||~ 19 min.|
|flame time||~ 24 min.|
|charcoal glow after flame||~ 10 min.|
Picture 3, 4, 5 and 6 are all shots of the burn.
Below in pictures 9 and 10 you will see the 10 minutes of charcoal like burn and the remaining ash, in that order.
I made one major mistake. I forgot to measure how much the fuel weighed before the oil was added. I think I dipped the original batch of fireballs twice. So I repeated the oil dipping, plus more dippings and weighings. This information can be seen in table 2 below.
|Woodgas Camp Stove Charge|
|Description||Fiber + Oil||Total Oil||Oil ea. Dipping|
|1st oil dipping||256.5g||57.8g||57.8g|
|2nd oil dipping||304.7g||106g||48.2g|
|3rd oil dipping||329.6g||130.9g||24.9g|
Picture 12 shows the stove filled with this new oiled dipped fireballs. This is to prove that they do not expand when the oil is added. If anything they may have shrunk but I can not see this as being possible.
I measured the angle of repose with the tube shown in picture 13 and the results can be seen in picture 14 and table 1
|angle of repose||~20%|
|bulk density  dry||354.4g / liter|
|dry particle density||0.460g / cm^3|
|oiled (3rd) particle density||0.957g / cm^3|