[Stoves] Calc. void space and pellet particle density

Mon Mar 10 12:14:14 CDT 2014

Alex,

It's not the change bulk density of the pellets that concerns me as much as
the change in bulk density of the sand that is used to measure the particle
density of the pellets. If a line was drawn around the inside of a TLUD and
a known weight of pellets were dumped in and shaken to the line may be a way
to come up with consistent %voids. 

But the sand used to measure particle density needs to be reproducible -
more than I get. So am open for ideas to other materials. 

The sand can be improved with washing with RO water and drying. But the more
you shake the more it settles so I standardize it to: fill to top and give
two taps on the bench then re-fill and level. Jellybeans would work better
but we need something small enough that free flows around the particles
being tested and close to its contour. 

The sample I tested was a quick test on some pellets I have had around the
lab for a few years I use for research. Did not use my precious washed sand
nor did I do it in replicates etc. Just to show an easy procedure to do the
test. 

The #20 sand comes from an ASTM procedure for determining bulk density in
packed soil intended for roads or earthen dams. They just pour and not
tapping. But we need to make sure the particles surround the particles we
are measuring - so a couple taps. 

I like the article you directed us to and the set-up for measuring the flow
rate. I think we must measure and not think we can calculate from the
formulas they give as it is all so complex. 

Thanks

Frank

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
alex english
Sent: Sunday, March 09, 2014 6:56 AM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Calc. void space and pellet particle density

Frank,

Thanks for  the numbers. 5 decimal accuracy aside, I just did a little
jiggling of a freshly poured sample of wood pellets,  which voidedthevoids,
so to speak. Roughly a 10% decrease  volume or increase in bulk density. 

Yours +/-

Alex

PS Came across this data;
http://www.pellet.org/images/2009-04-13_Airflow_Pressure_Drop.pdf

On Sat, Mar 8, 2014 at 5:53 PM, Frank Shields <frank at compostlab.com> wrote:

1555.68

sand

1053.17

water (vol)

671.78

pellets

152.47

pellets used

1539.82

Pellets + Sand

0.637865

Bulk density Pellet 

	671.78/1053.17

1.47714

Sand bulk density

	1555.68/1053.17

1387.35

Sand used when mixed with pellets

1539.8-152.47

168.33

Sand not used

		1555.68-1387.35

113.9567

Vol sand not used 

		168.33/1.477

1.337965

pellet density

		152.47/113.95

502.091

pellet vol in bottle

		671.78/1.337965

551.079

void space

		1053.17-502.091

52.32574

% voids

			551.079/1053.17*100

Tare a glass narrow neck bottle

Fill with sand -weigh

Fill with pellets weigh

Fill with water - weigh (vol of glass jar)

Calc bulk density of sand and pellets

Weigh a handful of pellets

Add sand > sprinkle in pellets > add sand > sprinkle in pellets until all
pellets are in bottle and topped off with sand

Weigh sand + pellets mix

Calc sand in mix 

Calc sand NOT in mix

Calc volume of sand NOT in mix using sand bulk density

Calc. particle density of pellets from wt hand full of pellets / volume of
sand not in mix.

Calc pellet volume in liter bottle when filled with pellets 

Calc. void space in bottle left 

Calc percent voids from void / total vol of liter bottle X 100

I fill with sand then tap twice on the counter then top off with sand. 

This is a sample from a local US pellet source. The bulk density is 0.638
g/cc and the particle density of the pellets is 1.338 g/cc

Void space for air movement in a TLUD filled with these pellets is 52.3% 

Instead of sand one can use water or acetone for other materials. The
particle density of sand (or like) I find best done using acetone.  

Hope the calcs are correct. : )

Regards

Frank

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 <tel:%28831%29%20724-5422>  tel

(831) 724-3188 <tel:%28831%29%20724-3188>  fax

frank at biocharlab.com

www.controllabs.com

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Dean Still
Sent: Thursday, March 06, 2014 11:21 AM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Cuber and size of densifying machines. (no longer Re:
The wood and char and fuel "debate" )

Hi Tom,

In Uganda the pellets were too dense and were hard to light. Do you know the
density of USA heating stove pellets?

Best,

Dean

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