Metal

Nat Mulcahy, World Stoves, March, 2010

Clearly pellets are the single best fuel option for Haiti right now.

Background

Ethanol stills use coal or wood, coal is not sustainable, and wood is vanishing fast. As for coal it is now being imported because local production and availability of wood is not able to keep up with demand and because much of Haiti is deforested. All fuel options underwent a 50% price hike following the earthquake. In ascending order of use the most common fuels are propane, kerosene, wood and coal.

Common Fuel Options in Quake Affected Regions

Haitian fire startersHaitian fire starters

Port au Prince uses 80% of all the coal consumed by Haiti. Wood, prior to the earthquake, was used mostly in rural areas but in many of the camps that we are working in we’ve noted more and more people using wood in their charcoal stoves. Kerosene is very expensive and used not for meals but for quick things like eggs or reheating precooked food. Following the fuel cost hike, however, I have seen more and more of the kerosene stoves gutted and transformed into small charcoal stoves by removing the tank and burner, pounding holes in some sheet metal for form a sieve to hold the charcoal and placing either a pot on the coals or using the rack or radiator from a refrigerator as a grill. As for propane it is used but the families in top 3% of the economic ranking.

Haitian Kerosene StoveHaitian Kerosene StoveKerosene Stove Converted to CharcoalKerosene Stove Converted to Charcoal

Regarding cost it is important to note that the drop in earning options and the spike in fuel costs now means that most of the displaced families now must spend 40% to 60% of the daily family income just to purchase fuel to cook with. In many cases this has meant that families have gone from eating two or three times a day to once a day even in the areas where WFP/PAM is sending distributing food.

What Other Options do we Have?

We could use fuels directly in the stoves which is one of the reasons I like gasifying stoves (fuel too small to use in a standard stove can be used in gasifying stoves); unfortunately the ability of gasifying stoves to use almost any biomass often creates misconception that all biomasses are the same. Users become disappointed when rice husks are used up faster than oak chunks. To avoid this I see briquettes and pellets as the best options. They are more consistent, clean to handle, low-cost, and perceived as a more modern fuel. This last is particularly important because many people are well invested in the “fuel ladder” and if they have already made the perceived social economic move forward (from wood to coal) they will not like to switch again unless it is to move up another rung. Marketing will be key to show that pellets and briquettes are a newer more modern fuel, it is important that pellets and briquettes not be viewed as taking a step back since they are made with “poor” materials.

Clearly pellets are the single best fuel option for Haiti right now.

1. What is the fuel offset by using the pellets? Is it 50% savings compared with wood?

wood fires here are either three rock stoves or charcoal stoves now being used with wood because many can no longer afford charcoal. efficiency is between 7 and 12 %maybe 20 % with some practice. pellet stoves require some training but then run themselves well and may be as much as four times more efficient. if you consider that 1kgofcharcoal produces here is really 7kg of trees the savings both economically and environmentally could be staggering

2. How much imported charcoal does it offset?

right now just one NGO's food program requires the use of 600,000 kg of charcoal a day, that's 1,800,000kg of CO2 per day give or take, right?and that is only one NGO hot meal program, put all the AID groups together and the numbers get big mighty fast

3. What are the relative costs of imported charcoal compared with pellets?

for now, thanks to Green Circle BioEnergy in FL we are providing free pellets to the people using our stoves. in general charcoal costs between 40% and 60% of a family's daily income. Daily income is about $5 US.

4. What is the benefit in number of meals from donated pellets? How may families could cook more than one meal per day by using donated or subsidized pellets as a transition fuel?

Green Circle Bio Energy's generous donation of 60 tons will provide 145,000 to 148,000 family meals, or feed about 740,000 people each once.
I strongly encourage other pellets producers to follow Green Circle's lead and in the mean time am working with the UN to see about funding regular shipments either weekly or biweekly to Port au Prince for the foreseeable future.
As a happy plus we have teamed up with three local ag and aforestation groups who will use the biochar produced by the stoves to restore soil carbon and help areas at risk of becoming desertified.

What Feed Stock Options are there in Haiti?

Feed stocks vary widely through Haiti but in the interest of simplifying logistics and keeping transport costs to a minimum I recommend that local pellets/briquette production be made using local materials. Clearly this means each small pellet mill or briquette press will have a specific optimal mix. UNDP and the Clinton Foundation have done a fine job with this concept and their briquette plant is now in its third year of operation. The use the Work for Pay model developed by UNDP for the collection of paper and cardboard throughout the city.

PaperPaper cardboardcardboardUNDP PelletsUNDP Pellets

These are then soaked in large drums and pounded in enormous wooden mortars to archive a consistent slurry prior to pressing. I would recommend the additional purchase of a hammer mill or two to accelerate production. We have measured a wide difference in hardness of the briquettes which makes the use of them harder to learn. This could easily be fixed with a grading protocol prior to the sale of the briquettes or controlling the pressing and packing procedure of the press.

Pellets would have the advantages of ease of use, faster production rates, no drying period (during the dry season the briquettes require three days to dry but during the rainy season drying can take as much as a week) and a wider variety of feed stock options to provide a more energy intensive fuel.

Around the quake affected region the feedstocks we have tested over the past five weeks have included, bagass, rice hulls, coffee hulls, bamboo, sawdust (many mills are working overtime to provide wood for shelters), chadek rinds, coconut shells and husks, mango cores, palm fronds, sugar cane, sugar cane shavings, paper, cardboard (personal thought, much waste has been generated during food and aid distribution, it would be nice to be able to use all of it so as not to leave a littered city in our efforts to help). All larger wood was used following the quake either for building shelters or to cook with.

wood chipswood chipsstrawstrawpalm frondpalm frondMangoMangococonut shellcoconut shellcorn cobscorn cobschadek rindschadek rindsfood aid packagingfood aid packaging

My favorite has to be chadek rinds, which by themselves produce a spectacular blue flame in the Luica Stoves. Chadek are large pear-shaped citrus fruits. And the rinds are saved as fire-starters.
Bagass poses some challenges in that the gas it produces often has sugars in it that do not always burn. This was not the case with the denser sugar cane shavings or the full cane chunks. Which leads me to believe that bagass, once pelleted would also function well. This, if verified would be a fantastic feedstock in that it is by far the most abundant in this area with mountains of it just sitting throughout the region.

Out side the quake affected areas there are a great many other feedstocks and the energy balance must be carefully made to see if any of these would make sense. From what I have seen vetiver grasses are clearly the most promising feed stock option followed closely by banana plantain plantation and processing waste.

Where to go from here?

For the short term and immediate future the best solution would be to import pellets. While the thought of importing fuel may cause some reservation it must be noted that current aid programs are importing charcoal to cook the food that is being distributed. Current food distribution of rice alone requires a daily supply of 600,000 kg of charcoal. Larger camps are importing propane. If the aid effort is already importing fuel would it not make sense to import more environmentally compatible fuels which at the same time would help sensitize Haitian stove users about a new fuel which could be sustainably 100% Haitian produced? We have enough pellets for the school feeding programs and some camps for the near future but a steady donor supply would be key as we work with WFP to establish up to 30 local pellet mills throughout the Port au Prince area.
Other askes could be small mills for schools, shipping and logistics help with donor pellets (getting the first shipment was a nightmare)and experts or pellet producers willing to consider production in Haiti, the market here is ready and the need for jobs here is great.

Our Stoves,

As for our stoves we are currently producing three types of stoves:

  • Large institutional stoves for the school feeding programs, orphanages, and hot meals programs in the camps,
  • Precut Flat packed Lucia Stoves with incorporated pot stand (1000 fit in a four foot cube and only bending is required to assemble them)
  • and a 100% local version of the Falt Packed LuciaStove made from oil drums. (there was a great feeling of pride when the local one out performed the lazer cut version)

Photos of all three are attached (please note on the large version that the local artisans we are working with insisted on decorating it with trees and birds saying they had to because if people use these stoves the trees will come back to Haiti and then so too the birds.

Street CookingStreet CookingTwo Haitian Pellet StovesTwo Haitian Pellet Stoves
Two Stoves and One FanTwo Stoves and One Fan
Lucia in HaitiLucia in Haiti
Haitian Lucia Stove in Use, note no smoke.Haitian Lucia Stove in Use, note no smoke.

Nat of WorldStove

Green Circle BioEnergy http://www.greencirclebio.com/
2500 Green Circle Parkway
Cottondale, Florida 32431
who would like to thank the following for their help:

  • Port of Panama City
  • Shelton Trucking, Alpha, Florida
  • Arizona Chemical, Panama City. Florida
  • Aggregate Trucking, Panama City, Florida
  • E B Pipe Coating, Panama City, Florida

Crispin Pemberton-Pigott and Roger Samson, January 2010

GrasifierGrasifier

Roger Samson was here tonight and we made and tested a Grasifier: a Switchgrass burning stove based on the dimensions of the Vesto adapted to make a lower cost pellet burning stove for Haiti.

Power, 2.5 kw
Burn rate 8-10 g/min
Mass 550 g
Fuel load 600 g though it can hold 750

Lighted with two caps of paint thinners
The flame went completely blue (just before the end) then wobbled a lot and went out.
When it went out there was no smoke indicating there were no volatiles left.

Time to fabricate, about 30 minutes.

I see this as a burner that can be attached to the centre of a Haitian charcoal stove to convert it into very clean burning a pellet stove.

Char yield: 25% of the initial dry mass.
Moisture content of the initial fuel, about 7%

Ash: nearly none.

Regards
Crispin

Nat Mulcahy, January 2010

Spent the day yesterday working with the state department to get more clearance for our shipments. 64 tons of pellets will provide food and clean water for 145000 families.

with 3,000,000 people displaced it will not last long. we are handing our the pellets and peanut shells in paper bags we have measured out to cook one meal or boil three pots of water. the paper bags are about the size one a lunch bag and the bag itself is the tinder to start the stove.

Spend the past two days working with NIH, EPA, The State Department, Haiti, USAID, and the World Bank. LuciaStove production is now set at 3000 per month but we keep being asked to ramp up to 5 to10 times that number.
Today we started casting the larger parts for the Biucci (the institutional version of the LucieStove), see attached. The more we make in haiti the more jobs we create here and the less we have to depend on the very sporadic shipping options.

Fuel, Stoves and Water for Haiti
January 27, 2009

There are several projects to supply fuel, stoves and potable water to Haiti. Some have been been ongoing since before the quake and some. The organizations we know of are:

CHF International, Helps (Water Purifier)
To donate a $35 water purifying system, go to https://secure.helpsintl.org/store/haiti.php

Legacy Foundation (Fuel Briquettes)

Miombo, Project Haiti www.prohaiti.org
Peko Pe TLUD pellet fueled stoves to be distributed by Project Haiti. Pellets from Georgia.

Trees, Water, People TWP
Ananda Marga Universal Relief Team AMURT http://www.amurthaiti.org/ and
Recho Rocket stove made from mud formed in a bucket, the Haiti Rocket Stove
Stovetec Rocket Stoves in a metal bucket.

World Stove, International Lifeline Fund
Biucci, Everything Nice TLUD stoves fabricated in Haiti. Pellet fuel from Florida (Green Circle). Grass pellets to be made in Haiti.

Martin Boll, January, 2010

Take a normal 870ml (fruit-) can, cut with a sharp-edged knife parallel cuts in the bottom with about 5mm distance.

1.-Bend with a screw-driver and pliers the metal-ribbons to get a grate.
This alone works well, but looses some fuel/charcoal.

2.- Form a “plissee”-metal-sheet (pleated) out of the side of a (10cm
diameter) can.

Each zig-zag-side about 1cm. The angles 60°. Put the can with slits ( like
1.-) onto the plisse-grate/support, so that the slits cross the plies in 90°.

-The plissee-lines are directed in wind-direction.

-The ashes on the pleated-metal-sheet can be cleaned with a thin stick or wire, while burning; but caution, that the tin-can-stove does not tumble.

-Another advantage of the plissee is, that the grat/bottom is heat-isolating and protected by the ashes. The charcoal falling through the upper gate is burning on the ashes on the plissee.

A CLEAN BURNING COOKSTOVE DEVELOPED IN VIETNAM
Alexis Belonio, Tran Binh, Doan Thi Minh Nguyet, and Bui Dinh Hai
VINASILIC SJ, Socialist Republic of Vietnam and Center for Rice Husk Energy,
Philippines January 24, 2010

Nathaniel Mulcahy, January 2010

Attached are the photos of Mr. Ronald Watts' version of our EverythingNice Stove. A version of which we are now rushing for the Haitian relief efforts to provide clean water. More later

yours, Nat

--
Dear Nathaniel

Here a a few photos from the successful construction and operation of the stove. Because I had no suitable vessels, I built them from sheet steel. It operates quite well, and is a good prototype for a larger model

Many thanks
Ronald Watts

Bjarne Laustsen, January 2010, update November, 2010

Jiko Mbono is Swahili for Jatropha Stove.

This is an early version of the stove, it is now using That stove was an early prototype. It is no longer using whole seeds but instead pellets made from the pulp left over after the pressing of jatropha oil, although there is only one pelletization facility for this in Tanzania and no distribution arrangements. Now only, the Jiko Safi uses whole seeds.
The idea is to plant jatropha as a hedge around land holdings. Animals won’t eat it and around an average holding it produces enough seed for a family’s annual fuel needs. I agree that planting it as a crop isn’t ideal

*****

Jiko Mbono was developed for burning whole Jatropha seeds.
The stove is a TLUD (Top-Lit UpDraft) gasification stove with natural draft air supply.

Earlier development of Jatropha stoves have mainly been based on the use of Jatropha oil. But the use of Jatropha oil in stoves have had some problems. In wick stoves the problem have been on the high viscosity of the oil which makes it difficult to climb wick to feed the flame, this has caused the wick material to burn. Jatropha pressurised stoves have also the problems of keeping the nozzles clean, and also the complicated design which tends to make the stoves relative expensive.

I therefore got the idea to burn the seeds directly in the stove. If the gasification process could provide the heat in the stove to vaporize out the oil from the seeds in the form of gasses, that will save us the work of first mechanically pressing the oil out of the seeds.

I therefore started some experimentation with some simple stove design, and these first experiments showed that it was possible to burn the whole seeds in a stove. Further developments was however needed to get an efficient and user friendly design of the stove.

I contacted Dr. Hassan M. Rajabu from College of Engineering & Technology at University of Dar es Salaam so that we could further develop the stove and test the stove after each modification. In this development we have received valuable economical support from the US based organisation Partners for Development and also support from Pamoja INC. Engineer F. Lauwo from Tanzania Engineering and Manufacturing Design Organisation (TEMDO) have provided assistance in producing the prototypes of the stoves.


Diagram of Jiko Mbono.

The fire in the stove is normally started by having a few crushed seeds that are soaked in methylated spirit or kerosene. These crushed seeds are placed at the top of other seeds in the fuelbox and the fire is lit in these crushed seeds.
The initial process can be started inside the stove or outside. When some seeds at the top got good flames (3-5 minutes) the fuelbox is then placed on the shelve at the bottom of the stove door and the door is closed so the fuelbox get into its position in the centre of the stove. In this initial phase the primary air is kept fully open.

The pyrolysis of the seeds by supply of primary air will gradually build up and the gasses from the pyrolysis will raise by the draft from the stoves internal chimney and be burned at the top by mixing with the secondary air.

During this gradually build up of heat the primary air supply need to be reduced such that enough secondary air can be supplied to allow for a good combustion of the gasses.

The burning of the Jatropha seeds is undertaken in batch portions. After all the seeds in the fuelbox have been pyrolysis the fuelbox need to be taken out and refilled for a new burning. It is not possible at this stage of the development of the stove to refill the fuelbox when the stove is operating, such refilling will just results in heavy smoke.

With a full load of fuel 300 – 400 gram of Jatropha seeds the stove can burn for 1 to 1½ hour when used in real cooking where the fire is somehow turned down. During test we have recorded specific fuel consumption on around 52 gram seeds per liter of boiling water, and an energy efficiency around 44%. However, the high efficiency is atributed to the design of the top part of the stove where the top is inserted in a skirt.

When operated properly the carbon in the seeds will remain as some kind of charcoal.

The use of renewable fuel is important here in Tanzania, where most of the biomass fuels are harvested in natural forests which takes year to re-grow.
We have estimated that a household having 200 – 300 meters of hedges of Jatropha trees will be able to meet their own need of fuel for the household cooking. Jatropha is often planted as hedges, it is a good hedge plant, as it is not browsed by goats, cows or other animals. Also as a hedge plant it does not compete with food crops on cultivating areas.

For urban households in Tanzania Jatropha is a viable alternative to charcoal. A farmer here gets 150 Tsh for one kg of Jatropha seeds (exchange rate 1350 to $). In town the Jatropha seeds will sell for around 300 sh. An urban household will need around 2 kg seeds per day to meet their energy need for cooking, that gives a monthly energy bill of 18,000 sh. If the same households are using charcoal it will on average consume 3 bags of 30 kg charcoal of a price of not less than 15,000 sh, this gives a monthly energy bill of minimum 45,000 sh. The use of Jatropha will in this way represent a good saving and alternative to fuelwood and charcoal.

Other seeds and crop wates can also be used in the stove. We know that seeds from the Croton tree burns well so does Castor seeds. We have also tried and found that the shells from cashew nut burn well in the stove. These shells are mainly a waste product from small-scale Cashew nut processing plants which are scattered in regions growing cashew trees.. We also believe that other seeds such as the oil palm kernel could also burn well when cracked a little. There will likely be many other oil holding seeds that could be used in such a stove.

This is a three-part brief description of the World Stove Everything Nice stove made by Al Hislop and Patty Roberts, with Ron Larson participating in the first tests, January, 2010.

World Everything Nice StoveWorld Everything Nice Stove
Plans Available at: http://worldstove.com/wp-content/uploads/2009/11/EverythingNice_Stove_Instructions.pdf

Part A. Narrative (by Patty)

Biochar Experiment 1 1/9/10

Al made an Everything Nice pyrolyzer from the design on the World Stove website. We used a large coffee can and then a canister for the two cans so it was rather large. We first tried pine cones but they just smoked so we put in pellets instead. This gave a good clean burn and we put a tripod over the stove and boiled water, heated soup, cooked pasta and cooked pasta sauce with fresh meat and fresh vegetables. When the flame extinguished, there was still some smoke coming from the stove so it was covered on the top to remove oxygen and set in a shallow basin of water on the bottom. This extinguished the smoke but moistened the bottom of the char slightly. When we emptied the stove, we saw that some of the pellets had not pyrolyzed. We believe this was because of the fairly large diameter of the can. To dry the char and pyrolyze the remaining pellets, we put the mass into a canister and put it into our hot wood stove. This allowed complete pyrolysis of the remaining pellets and provided complete drying of the fuel. It’s possible that this changed the pH of the char from its original pH because of a different pyrolysis temperature.

Ignition: torch (for several minutes)

Pre-burn Fuel Weight: 58.5 oz wood pellets from 100% pine, less than 1% ash

Post-burn Fuel Weight (Char): 16.5 oz (28.2% of starting weight)

Post-burn Fuel Volume: Slightly greater than half of pre-burn volume

Time: 2 hours and 20 minutes of a very good, clean, strong burn.

Calculated output to pot: 560 watts


Exp1: (Saturday)
_*Lighting:*_ See text. Hope others can tell us of their successful
ways to light this same stove. We have not yet tried to solve this
problem using prepared starter materials. Maybe easier with the
"restriction-lid" removed? The two sheet metal wind-breaks and the ice
show this was not the best day for testing. Note the small amount of
discoloration (burned paint on the lid) - from an earlier test with
too-loose material (that was easier to light), which only gets a little
larger in later photos.. Discoloration off-centered because of windy
conditions and means of lighting. When we got it started with this
torch, there was never any massive smoking.

Experiment 1, Good FlameExperiment 1, Good Flame

*_Good flame_*. A typical flame without a cook-pot. We saw essentially
the same flame for a total of more than 4 hours over two experiments.
The gap-reducing bricks not in place in this early photo. The
discoloration of the lid never got much more pronounced than here -
showing that a relatively cool gas is coming up in the outer narrow
"chimney". You can't see it here - but there are hot gases going down
through the central can fuel supply - doing the pyrolysis without
oxygen. We are unsure whether any pyrolysis gas is coming upwards
(we don't understand the pressure profiles yet), but certainly a good bit
is going downward. This is the best view of the outer set of large
holes. Could they be done with a punch? Maybe. Could they be
placed on the bottom of the outer can? Maybe - with a spacer
between the bottom surfaces of the two “cans” (as is done in the
mainWorld Stove models). There are several ways
possible to control this air supply - which should NOT be called the
primary air, as would be appropriate if this were a TLUD. Although
there is some pre-mixing of the combustion gases, this still is showing
signs of being a ("wispy") diffusion flame - not at all like the tighter
much bluer flame seen in Nathaniel's numerous YouTube videos and
mentioned in the instructions.

Experiment 1, CookingExperiment 1, Cooking
*_Cooking_*: Typical flame with a typical pot (and larger ones used for
some of the cooking). The tripod was in no way optimized (we raised
the stove about three inches with standard available mini-bricks; four
inches might have given higher efficiency - but more soot). It was
certainly easy to have too much heat for cooking pasta (boil-over once
when we weren't paying attention). At no time during the two hours of
operation did we (or could we) adjust anything. We are working on a
possible fix for that, when on a later weekend, we will try a means of
controlling the air flow. You should also next see a "convection skirt"
of the type being sold by Aprovecho.

Biochar Experiment 2 1/10/10

Using the same stove as yesterday, but this time with a cone in the center to displace the area that didn’t pyrolyze yesterday, we filled the stove with pellets again. This time however the stove had 15% less fuel because of the cone. We spent about a half hour trying to light the stove with twigs, vasoline, pine needles, paper, some other fluffy combustibles and fondue fuel. None of these things got the stove going. We ended up using the torch again. The torch lit the pellets in a minute or so and then it took about 15 minutes before we saw the good, steady, smokeless cooking flame. Once we got that good flame, we measured 2 hours 23 minutes of pyrolysis. The stove burned for the about the same amount of time as yesterday, but this time all the pellets were pyrolyzed. The outer can seemed to have the same temperature pattern today as yesterday.

Ignition: torch (shorter time than yesterday)
Pre-burn Fuel Weight: 49.5 oz wood pellets (same kind as yesterday)

Post-burn Fuel Weight (Char): 14 oz (28.2 % of starting weight, same as yesterday)

Post-burn volume: a little less than half

Calculated output to pot: 287 watts (This number is much lower than yesterday’s. We don’t like our thermometer for this application, so both days’ numbers are suspect.)

Time: 2 hours 23 (more carefully measured than yesterday)

Those temperatures were pretty consistent until the pyrolysis ended and we put a cap on the top. Unlike yesterday, we didn’t put the bottom in water. Smoke began to come out of the holes at the bottom and the temperature at the bottom began to rise. We suspected that some combustion was starting to take place. We poured the pellets into a tray but they seemed to be getting hotter rather than cooler so we scooped them into another canister and put on a tight lid so no more oxygen would be available.

Experiment 2, ConeExperiment 2, Cone

_*Cone*_ - Showing the cone and the interior (the latter after almost
five hours of operation). No signs of any excess heat anywhere on the
outside can. Little on the inner can, but considerable tarring on the
inside and the top portion of the cone. Probably a lot of interesting
pyrolysis science in understanding why the cone looks like it does after
2+ hours of operation one time. Note the many interior small holes.
Note the single screw holding the two cans together (not shown in Nathaniel's drawings [at http://worldstove.com/wp-content/uploads/2009/11/EverythingNice_Stove_In...
] but mentioned at the bottom of p 3. We found all the instructions
complete, but guess we have to test a lot more fuel combinations before
we get the tight blue flame mentioned in the instructions.

Experiment 2, After PyrolysisExperiment 2, After Pyrolysis
Exp 2 (Sunday)
*_After Pyrolisis_* A view into the unit perhaps ten-fifteen minutes after the
unit stopped operating - and began smoking (pretty profusely, so you
want to react quickly). We placed a second lid to cover the opening -
but nothing else.(no covering of the lower holes - which we would likely
try to do next time). Note good uniformity of the char except right in
the middle where you can see the tip of the added cone. This is the first
time you can see that there are two cans - with the spacing of about a
centimeter (exact spacing dictated by can availability; this outer can is available at
about $.50-$1.00; no cost for the inner can). At the lower left is the
(pre-trimmed) pine cone which charred perfectly after being placed into
the unit.. No lighting up, no combustion, perfect retention of tiny
features - proving the lack of oxygen just below the flames seen in
other pictures. The unit was initially filled up to within 3/4 inch of
the top of the inner can, per Nathaniel's instructions, so you can see
there was perhaps 35-40% shrinkage.

Experiment 2, CharExperiment 2, Char
_*Exp 2 Char:*_ This to show the good uniformity of the resulting
char. Just a few that looked torrified (deep brown color - but we
can't even see them in this photo), not charred. In Experiment #1,
with no interior cone, perhaps 15% uncharred, roughly in the volume
taken up by the cone.

New plans and new ideas: We want a sliding band around the bottom of the can which can be used to regulate airflow through the holes and maybe the pyrolysis rate. When the band slides down, it will partially close the holes. When pyrolisis has finished, the band can be pushed all the way down to cover the holes entirely and keep oxygen out.

Part B. Technical Description

(by Al)

The inner tin was a Yuban Coffee can, with diameter 6.05 inches (excluding the roll bead where the bottom is attached. The original height of the can was 7.5 inches, and the height was trimmed down to 6.7 inches above the inside of the bottom surface. 74 holes .0.159 inch diameter were drilled on a line 0.75 inches from the bottom.

The outer tin was a decorative cookie tin with a fitted lid. The diameter of the can (excluding the rolled bead that attached the bottom) was 6.4 inches. A 3 inch diameter hole was cut in the center of the lid. The lid was 7.1 inches above the inside of the bottom of the can. 33 holes of 0.5 inch diameter were drilled as close as possible to the bottom of the outer can.

The inner can was filled to about ¾ inch of its top with pine pellets intended for use with pellet stoves. The weight of the fuel was 58.5 oz (1.66 kg). These pellets were ignited using a propane torch over the entire top surface for about 1 minute.

The stove operated with what appeared to be constant output for 140 minutes. A water heating test was performed with a pot set about 3 inches above the stove opening. Two liters of water was placed in a covered pot of diameter 8.5 inches and height (without lid) of 3 inches. Water temperature was measured using a “point-and-shoot” infrared thermometer. (I suspect that at higher temperatures this thermometer reads low, as it most likely senses the temperature of the steam above the water in the pot, and not the water itself.) Water start temperature was 12.5C, and finish temperature was 81.1C, at which time boiling bubbles were coming off the bottom of the pot, and much energy was being lost to steam. Elapsed time was 17 minutes.

When the flame extinguished, much smoke came from the stove, so a lid without a hole was placed on top of the stove. Smoke continued to pour from the holes at the bottom of the stove, so it was placed in a pan of water to cover the holes. This resulted in wetting of the contents of the stove. After cooling, the stove was opened and the contents examined. The fuel was found to have been converted to char, except for a portion of pellets about 1.5 inches high and 3 inches in diameter at the bottom of the stove.

Since the fuel was wet, it was not weighed. Instead, the wet fuel including the unconverted pellets was placed in a container and heated to complete pyrolization. The weight of the remaining char was 16.5 oz (28.2% original weight).

A hollow metal cone of height 4.5 inches and diameter 4.5 inches was made, and placed in the bottom of the inner can before adding fuel pellets for a second run. This time the weight of the fuel was 49.5 oz, the burn time was again 140 minutes, and the weight of the remaining char was 14 oz (28.3% original weight). This time all but 1 or 2 pellets appeared to have been converted to char.

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