In my continuing quest to use readily available manufactured materials for stove construction, here is the steam pan charcoal stove with "perforated lollipop" air control. It is a 1/6 size steam pan (roughly 6" x 7" x 4" deep) inside a 1/2 size (roughly 10" x 12" x 6" deep) with 1" ceramic fiber board insulation between. The charcoal chamber is lined with expanded stainless steel to extend the life of the inner pan and improve air flow. Army surplus D rings are used for pot supports. Threaded rod for legs. It can be easily disassembled for repair. It has a small charcoal capacity like the BURN's Jikokoa (formerly Tank).
I plan to eventually build a two burner version in a full size steam pan.
On my trip to Haiti in March 2016, I finished the ammo box stovetop oven. It is made with two ammo boxes, ceramic fiber board insulation, some stainless steel sheet, and various hardware. The oven chamber is 13" x 13" x 5". I plan to add split firebricks on the floor for use as a pizza oven. It fits on a household rocket stove but could be used over virtually any heat source.
We are trying to (a) reduce the amount of emmisisons from charcoal production and (b) Condense and recover as much of the smoke into a usable product for your home/farm. Wood tar - the following is an explanation from the good folks at Food and Agriculture Organization of the United Nations (FAO) about what is going on in this process.
"The non-water component consists of wood tars, both water soluble and insoluble, acetic acid, methanol, acetone and other complex chemicals in small amounts. If left to stand, the proligneous acid separates into two layers comprising the water insoluble tar and a watery layer containing the remaining chemicals. Recovery of the water insoluble tar, often called wood or Stockholm tar, is simple - it is merely decanted from the water phase. This wood tar has uses as a veterinary antiseptic, a preservative for wood, a caulking agent, and as a substitute for road tar" http://www.fao.org/docrep/x5328e/x5328e0d.htm
On a recent trip to Haiti I was finally able to construct my CharBowl(tm) charcoal stove. It uses two nested stainless steel bowls (5 quart and 8 quart (4.7 liters and 7.6 liters))for durability and reflectivity with castable insulating refractory between them to reduce conductive heat losses. It has a 6.5" (16.5cm) dia cast iron grate for durability. It has a secondary air pipe to reduce CO emissions and increase heat output. The secondary air outlet pipe is 3/8" (10 mm) nominal (ID 0.493" 12.5mm; OD 0.675", 17mm) black iron with a Tee fitting on top to keep charcoal from dropping into it. 3/4" NC 10 (19mm 2.5) machine threads were cut over the pipe threads. This allowed the use of a split nut and flat washer inside and outside the bowls to hold the bowls together. The elbow is 3/8" to 1/2" . The inlet pipe is nominal 1/2" iron (ID 0.622" 16mm; OD 0.84", 21mm). The bowls sit on a stock pot base for stability and primary air control. (I couldn't get my hands on the stainless pot I really wanted to use for the base. I'm planning to build another with such a base now that I'm back in the States.)
I hope to get some testing done on my second prototype.
It can be used as the base of a TChar stove.
The triplets of triplets in the secondary air supply is a significant improvement.
The 18-12-6 iCan now has much greater total time with a very well behaved flame and an air fuel mixture that is lean to good for most of the run.
There are still several minutes of a too rich mixture that does emit some soot.
Run time on 350 grams was 27:45, most of the smoke was gone within 2 minutes, just two floaters, and the biochar had a good clean nose. This is about as good as I have gotten so far.
The "Easy 5 Gallon Bucket Rocket Stove", is very easy to build. All materials anyone needs to cook a good hot meal is a metal 5 gallon bucket, some stove pipe and vermiculite, pearlite or similar insulation (even "wood ash" can be used). Since the insulation separates the heat from the housing, almost ALL of the flame and heat is directed up to the cooking pot or utensil. Almost NO heat is wasted, making it one of the most efficient rocket stoves I've seen. Definitely one one the EASIEST to build and transport!
Crispin Pemberton-Pigott (New Dawn Engineering) with Prof Sereeter Lodoysamba (National University of Mongolia),
Sod Dulam (Energy consultant, Ulaanbaatar) and Altangadas Tsegmid (Heat and Power Systems consultant, MonEnergy)
This stove was seen in operation in 6 and 8th March 2010 by in the home of Demberel in Ulaanbaatar, Mongolia.
It is a form of top lit updraft (TLUD) stove part of the time. The combustion chamber is a (ceramic?) lined square box with a grate enclosing the top and the bottom. It is mounted in a fairly standard brick-lined steel box with a heat exchanger at the back. The overall dimensions are approximately 500 W x 600 L x 500 H.
The unusual burning sequence is:
Open the stove, push the top grate out of the way (towards the back).
Build a wood fire in the combustion chamber and wait until it has burned to the point of being substantially charred.
Load coal on top of the burning wood. At this point it becomes a bottom lit, updraft (BLUD) burner.
The coal is left to be heated on top of the burning/smouldering wood. The top grate is pulled over the coal closing the box. It is now a square box with a grate on the top and bottom.
When flames emerge through the coal and appear above the top grate, the box is flipped over using the handle on the front of the stove. At this point it becomes a TLULD burner because the charcoal has been moved to the top. The smoke arising from the hot coal below has to pass through the charcoaled wood on top and is ignited.
The charcoal finishes burning during which time the coal gets fully ignited, de-volatilised and coked. After that it is an ordinary coke fire.
The coke fire burns until it expires. During the first visit it was tested with a combustion analyser during the later portion of a burn. There was nothing unusual about the fire. On the second visit gas samples were taken during ignition and for a period of one hour afterwards. The sample point was where the gases leave the mass wall and enter the bottom of the short chimney passing through the roof. Gases were analysed with a certified TSI CA-6203 combustion analyser.
Initially the CO/CO2 ratio was 20% to 40% as the fire got going. The ratio after one hour was just over 4% and 12 % late in the fire. At all times there was a high excess air ratio, 900% on high power and 1500% on low. This is higher than a traditional stove which runs 400-1000%.
The system efficiency was negatively affected by the high excess air level: from 40 to 50%. The system efficiency of a traditional stove is about 70%. The major portion of the particulates are emitted during the first 45 minutes in both stoves.
The 'heating wall' is a heat storing brick structure that condenses the combustion and fuel moisture thereby retaining the latent heat of condensation. They are gaining popularity. In spite of condensing the moisture and the low gas exit temperature (70-90 Deg C) the system efficiency is not high because of the great quantity of warmed air passing through the system. The openings are large and the stove is generally leaky, for example the cast iron top on the one we tested is not bolted onto the body (see the picture near the end of the video).
A moveable flat plate with a few holes in it is provided over the top grate that limits the rate of combustion. The burn rate is quite high for a domestic stove (because of the large area of the grate). It is probably able to reach 40 kW thermal output. The flat plate is pulled over the top grate and interferes with the airflow, extending the burn. A full charge of coal will reportedly burn for 8 hours in that condition and still have some hot coals left with which the next fire can be started. That is a major consumer demand - burning through the night.
: It is likely that this system will reduce start-up emissions from the point that the hot coal is under the burning wood/charcoal fire (the TLUD stage), for approximately 1/2 of the ignition cycle.
: The system efficiency is low compared with a traditional stove which means that although the rate of particulate production may be less per kg burned during part of the ignition cycle, more coal might have to be burned to provide adequate heat, possibly increasing the overall production of smoke.
The contact information for one of the local (Mongolian) promoters is:
Prof Adiyasuren Borjigdkhan firstname.lastname@example.org
He reports that they wish to install 80 in homes around Ulaanbaatar to gather user opinions.
Crispin Pemberton-Pigott (New Dawn Engineering)
with Prof Sereeter Lodoysamba (National University of Mongolia)
and Sod Dulam (Energy consultant, Ulaanbaatar)
and Altangadas Tsegmid (Heat and Power Systems consultant, MonEnergy)