[Stoves] Calc. void space and pellet particle density

Mon Mar 10 13:13:57 CDT 2014

Ron and all,

Seems a few years back there was a University (or some group) that was going
to assemble a collection of test methods for stoves? Was Tami involved? Did
anything come of that? 

See below:

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Ronal W. Larson
Sent: Sunday, March 09, 2014 5:17 PM
To: Discussion of biomass
Subject: Re: [Stoves] Calc. void space and pellet particle density

Frank:  (and anyone on list)

  1.  Would you be good enough to add a few more tests:

a.      Measure (ml or gm) the amount of water (and/or acetone) you can add
to the container full of sand.  (I see relative density of .785 for acetone)

[Frank >] I like acetone because water can have air bobbles when measuring
the density of grains of particles -like sand. So for particle density of
sand you fill a container with water to get volume. Then fill with acetone
to get the density of acetone. Then add sand and acetone together to get the
particle density. 

b.     Same for sand replaced by pellets, even if the pellets are ruined
(but try to make the weight gain measurement as fast as possible (see how
much you can both add and drain).  But perhaps they can be waterproofed with
only a gram or two of waxy material.

[Frank >]  -Official tests for soil requires to coat with wax and use water.
Terrible - terrible. The wax leaks and add volume. The sand is better. The
sand changes in bulk density when shaken (a problem) but the item being
tested (wood chips, pellets, soil clod) do not change in particle size. So
my thinking is to decrease the sand / sample ratio as much as you can. That
is add the most pellets to the liter bottle as possible and get them to be
embedded into the sand.   

c.      Same when you mix sand and pellets  (my preference is to start with
a liter of only pellets, then first see how much sand you can get in [by
shaking], weigh and then see how much water (and or acetone) can be added).

[Frank >] I do this for wood chips and suggest for large particles like the
cubes being talked about. Fill a container to the top to get bulk density
then pour in the sand with lots of tapping. Take out the wood pieces and
determine the reduction volume of the sand (= voids). But for smaller
particles I suggest embedding the particles in the sand to make sure there
are no big pockets of voids. If you keep tapping the sample will float to
the top. So for wood chips and sticks I add sand and chips together and make
sure there is plenty of sand on top. Then tap until I see the first sigh of
sample pocking through the top. Then I know the particles are all surrounded
with sand. 

  2.  I agree with Andrew Heggie that a void space of 52% sounds high.  Can
you specify the diameter of the pellets and an average pellet length.
Manufacturer?  Any spec on source material?

[Frank >] This was a quickly conducted test using a real sample but without
all the QC usually done for the sole purpose of showing an example of how to
do the test. 

  3.  If you have to start over, let's use a volume of "exactly" 1 liter
(water weight = 1 kg), for all cases (to simplify the computations).

[Frank >] 

http://www.novatech-usa.com/Products/Glass-BOD-Bottles

http://www.hach.com/disposable-bod-bottles-300-ml-100-cs/product?id=76402371
02

One liter volumetric flask is not easy to use for such tests. Nice to fill
to top and determine that volume. I like BOD bottles for using with acetone
or water for testing the particle density of very small particles. Eye
dropper removes the excess to exact. I use glass but they are expensive. The
disposable ones are made of a plastic and I will work for water but may
not(?) with acetone (or other solvents).  

I use imhoff cones for wood chips and sticks. Add sticks or chips to a
couple inches from top. Pour in sand and tap, tap, tap until the chips poke
out of the surface. See total volume from marks on side. Pour out the sand
and collect. Dump wood. Pour back sand, tap, tap, tap and see volume of
voids. 

http://www.coleparmer.com/buy/product/56354-imhoff-settling-cone-plastic-eac
h-w990800.html

  4.  We should be able to get the same answer for pellet density regardless
of how hard we try to increase the bulk densities (Alex' point).  

[Frank >] Pellet density but not necessarily pellet bulk density. Depends on
packing. 

Thanks in advance.

Ron

On Mar 8, 2014, at 3:53 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

(831) 724-3188 fax

 <mailto:frank at biocharlab.com> frank at biocharlab.com

 <http://www.controllabs.com/> www.controllabs.com

From: Stoves [ <mailto:stoves-bounces at lists.bioenergylists.org>
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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