TLUD

Chinese TLUD camp stove purchased on EBay
Stove insert and perforated pot support ring
Flame pattern with insert

Modifying a Retail Chinese TLUD Camp Stove for Improved Efficiency

The problem with the stove is that the primary air grate has large diamond shaped cuts for air. This allows the stove to burn excessively, producing a large flame exiting the stove top. The large flames envelope the pot bottom and sides producing heavy deposits of soot on the cooking utensil.

My idea was to modify the stove by reducing the primary air and attempt to force the flames back into the burner by using a stainless steel cylinder in the center of the stove opening to restrict the exiting air flow, and at the same time introducing air into the stove top by punching holes in the angled concentrator ring/pot support.

To restrict the primary air flow, a paint can lid was placed upside down inside the stove bottom. A threaded bolt was run through the center of the lid, and four small holes were punched for primary air. A stainless steel cylinder was affixed to the top of the threaded bolt. Cylinder height adjustments can be performed by loosening the jam nuts, repositioning, and re securing.

No fan is used.

The assembly is placed inside the stove, and wood pellets are poured onto the paint can lid. (About 1” deep). After the pellets are ignited, it takes around 5 minutes for the stove to gasify. After gasification, you can see the flames are being pushed down into the stove.

Small scale biochar production and use was discussed at the annual conference of the Engineers in Technical and Humanitarian Opportunities of Service (www.ethoscon.com)

An estimated 2.5 billion people worldwide cook their meals with biomass. ETHOS is an international group of individuals and organizations that promote improved cooking stoves for health, safety, and household energy. The Toplit Updraft or TLUD stoves are efficient and can produce biochar as a co-product of household energy.

Participants were interested in how biochars can be used to remediate soils and improve agriculture. Norman Baker, Sequim, showed how a 55 gallon TLUD can be used to make biochar for growing vegetables and improving nutrition. Paul Anderson (drtlud.com) described 12,000 TLUD stoves in India that product 10 tons of biochar each day. Users receive cash from selling the biochar to a German company, atmosfair gGmbH, which recovers carbon offsets for the energy savings and char to help fund the energy efficient cooking stoves. Art Donnelly, Seachar (seachar.org) demonstrated a new biochar making stove and described how biochar from cooking stoves has been used by coffee workers in Costa Rica. ETHOS participants are among the 1600 partners of the Global Alliance for Clean Cookstoves (cleancookstoves.org)

ETHOS Lighting of the stoves
CREEC, Aprovecho Sam and others at ETHOS 2015
StoveTec TLUD with a toasting marshmallow
StoveTec Stove - new Colors
Christa Roth sitting near the StoveTec stoves
Peter Scott and others ETHOS 2015
Kirk Harris TLUD
Rocket Works Stove ETHOS 2015

ETHOS Cooking Stoves Conference in Kirkland, Washington January, 2015.
for more about the next ETHOS Conference see http://www.ethoscon.com/

The ETHOS conference brings together people involved in stove design, dissemination, and testing from Universities, Government, and Non Government organizations, and has themes around the topics of improving cook stove design and performance, reducing emissions, and improving stove adoption, but listening to the needs of the people using the stoves. It ends with the 'lighting of the stoves' which is a demonstration of some of the cooking stoves that people have talked about in the conference.

In addition to capturing photos of the stoves, this year I captured a few pictures of the crowd of attendees comparing stove designs, toasting marshmallows, etc.

The big green stove is the InStove institutional rocket stove http://instove.org/

The lovely people taking pictures were from CREEC ( Energy and Energy Conservation ) which presented a great analysis of current cooking stove tests and some insights to improve them. They also noted that fans typically fail in Uganda, and there are no fans available to replace them.
For more about CREEC see http://creec.or.ug

StoveTec and Aprovecho presented some interesting innovations in stove design that they hope to field test in the coming year. The light green stove has an insulated top door for adding fuel to their TLUD style stove. The purple stove is their rocket stove that has been optimized for improved particulate emissions, with an improved set of colors.
For more about StoveTec stoves see http://stovetecstore.net/
for more about Aprovecho and stove testing see http://www.aprovecho.org/lab/index.php

I was happy to get a good picture of Christa Roth of GiZ her handbook of MicroGasification is outstanding, to download a copy go to https://energypedia.info/wiki/File:Micro_Gasification_2.0_Cooking_with_g...

File attachments: 
TLUD Oven
height adjustment for turn-down
Oven Temperatures
Wood Pyrolysis to Char burning transition
bread baked in the TLUD oven

Marc Ayats Plana has updated his TLUD Oven paper the latest results. You can download a copy here.
http://stoves.bioenergylists.org/files/tlud_oven_english-update.pdf

This Oven started out as an experiment in creating a low mass oven using a rocket style stove, and after some experimentation Marc switched to a TLUD style stove to improve the oven's efficiency and to also be able to use agricultural residues, almond shells, instead of wood. Please see the report for details.

And there is more on the Fogons Solares web site:
http://www.cuinessolars.jimdo.com

File attachments: 

The Wonderwerk TLUD natural draft test stoves use a combustor section above the secondary burn area to provide time and space for the secondary flame to burn more completely.

The project started as a way to shorten the overall height of a TLUD stove by adding an improved combustor. In the process of Kirk Harris improved the efficiency of the stove.
His write-up: http://stoves.bioenergylists.org/files/wws_tlud_combustor_paper102714.pdf

Kirk modified the original TLUD design ( http://www.drtlud.com ) to include a concentratior and used Venturi principles to blend secondary air to improved combustion.

File attachments: 
TLUD Bread Oven
Flat Bread
TLUD Parts
TLUD Assembled
Oven Temp Profile

Estremera Nova, Bunyola, Illes Balears, Spain htttp://www.cuinessolars.jimdo.com

Marc Ayats Plana has been working on TLUD stoves and improved low thermal mass ovens. This TLUD powered low thermal mass oven was inspired by the Anderson's Recho Rocket Oven, and uses a Champion style TLUD heating stove to power the low thermal mass earth oven.

For Marc's excellent writ-up download the pdf TLUD-OVEN Description
These are some quick notes:

He has made some changes to the TLUD style oven

  • Increased primary air draft, which can apport enough oxigen to burn the charcoal generated during the gasification process and continue giving heat to the oven. Now the primary air enters around the lower perimeter of the reactor, instead of having a single inlet tube like in the original model.
  • Increased the length of the riser, which also sustains the diffuser. This extra extension allows the complete combustion of gases gasification to completely remove the visible smoke in the oven.
  • TLUD Reactor. Diameter: 20cm. Total length: 30cm. Fuel Height: 20cm
  • TLUD Outskirt. Diameter: 22cm. Diameter central hole: 10cm. Total length: 25cm
  • TLUD Riser and diffuser. Diameter: 12 cm. Total length: 30cm. Diffuser: granite piece 2cm thick and 15cm diameter
  • Fuel load: 3.38Kg pellets

The Low Thermal Mass oven is based on the Haiti Rocket oven http://www.rechoroket.com
To see more pictures of the TLUD oven and the process of construction go to:
http://cuinessolars.jimdo.com/forns/

In the Oven Temperature graph, you can see the complete temperature profile. Marc did a side by side comparison of both a 20cm reactor TLUD and a smaller TLUD, with 12,5cm reactor.
"Note: the temperatures refers to the inside side of the wall oven, half way between the baking surface and the top hole. Note2: the temperatures were taken by a temperature datalogger and a type K probe."

Marc's Notes and TLUD size comparison are copied here:
Notes about 20cm TLUD test

Notes from Paul Anderson
Gustavo has presented a very nice video of the use of a tall TLUD gasifier under a DUAL purpose stove frame (frame = stove structure without the heat source) that first boiled 5 liters of water in 12 minutes, and then converted into a plancha stove with chimney, cooking papusas (related to tortillas). Total cooking time 1 hour 45 minutes on one batch of wood chips/chunks (5237 grams) that yielded 1300 g of char. 25% weight yield of char. Probably could have operated an additional 10 minutes with pyrolysis fire and a slightly lower percentage yield of char.

Note: That is approximately 4000 g of fuel of pyrolytic gases (including moisture content that was probably near 15%). Any ash content (probably 1% of the raw fuel) remained in the char.

For a comprehensive resource for TLUD stoves, see Paul's web site: http://www.drtlud.com/

This presentation was put together by A.Phrao, Chiang Mai of the Warm Heart Foundation in Thailand. They are using biochar to attempt to restore fertility to badly degraded mountain soils, and to intensely fertilized mono-cropped soils that have low fertility.

They designed this medium sized TLUD system with the following constraints:
They wanted to design a simple, low-cost biochar burner that:

  • Can be built from locally available materials, preferably recyclables, at little cost;
  • Can be manufactured by local mechanics without
  • training;
  • Can be operated safely and efficiently by a single person;
  • Can use a variety of feed stocks, preferably field waste;
  • Can produce a minimum of 1 ton of biochar per week under normal, unpressured operating conditions.

The solution is pretty ingenious - please take a look at the PDF for all of the details.

The following is quoted from the pdf:
The 6-burner TLUD merry-go-round:
materials list

  • • 1 x children’s playground merry-go-round or equivalent
  • • 6 x 200 litre steel drums
  • • 6 x 60 litre steel drums
  • • 8 x meters 1” OD steel pipe
  • • 6 x meters 1” angle iron
  • • 6 x 3” hinges
  • • Miscellaneous nuts and bolts, welding rods, grinding wheels
  • • Circular grinder, arc welder

System

  • • 6 TLUD burners
  • • 55 kg corn cob load/barrel
  • • 20+ kg biochar output/barrel
  • • 120 kg per burn
  • • Single man can load, light, rotate, load, light, rotate…empty, extinguish, empty, extinguish… all six loads in 1.5 hrs.
  • • Single man can grind full load in 1.5 hrs.
  • • Two full loads per day = 240 kg/day
  • • 6 day week = 1,440 kg/wk
  • • Feed stock requirement = 3,600 kg/wk
  • • Cost: corn cob @ 700 baht/ton ($23.35) or $60/ton biochar if farmer does not have own supply
Lighting Cone on the Keren Stove no smoke 1 min after lighting
Anglo Supra Nova Stove
Loading the Anglo Supra Nova Stove
Good Fit for Cone Lighting
Lighting Cone on the Anglo Supra Nova
Handles get hot on lighting cones - make them large

Lighting Cones can help make traditional and charcoal stoves light more efficiently and with less smoke than other lighting methods. For the best detail, download the Masters thesis pdf from Kathleen Lask

From Crispin Pemberton-Pigott's Description:

"The main principle is that there should be enough draft to light the fire rapidly. The lighting cone provides this if it is about 500mm tall."

"The second principle is that the bottom of the cone should sort of cover the lighting fuels so that most air is pulled from below, not from the side."

"The third principle is that if there is a secondary air supply at of just below the top of the fuel, the bottom of the cone should bypass it so that the heat inside the cone is not used to pull air through the secondary air ports. Very few stoves have a secondary air controller."

In the result with good fit: "You can just see on the left that it bypasses the secondary and draws all air from below, through the fuel – in this case charcoal. Peter Coughlin reports it reduces the charcoal ignition time by more than ½. We will quantify the smoke reduction and GERES way independently confirm it at some point – it is about 90%."

Lighting stoves can also be used with traditional fires. In tests lighting damp wood in Suba Island "The speed of ignition and reduction in smoke was dramatic. You can just see the hot air distortion of the picture above the cone – basically no smoke. It is quite a bit cleaner than the fire when lit and the cone removed."
The cone on the 3 stone fire is 125

The Stove in the top example is an Anglo Supra Nova.
"It was developed at YDD during the World Bank/Indonesian Clean Stove Initiative."

"It as an Anglo Supra with preheated secondary air. It can burn wood or charcoal, and it can burn wood pellets in TLUD mode. It can automatically switch from pellet burning TLUD pyrolyser mode to char-burning mode by using a disc of paper on top of the grate."

"The loose piece of clay is a door which can close the primary air without affect the secondary air. It provides a significant level of power control without adding or removing fuel. The heat transfer efficiency burning charcoal (it is nominally a charcoal stove) is about 50%. It Is portable with handles and sells retail for about $5.50."

Kathleen’s investigation is attached.

Regards
Crispin

 Quad – 2012 to Present
Quad Flat Assembly

The Quad TLUD has features for easier production (using tabs and slots, and zero rivets), easier shipping (as flat-pack pieces), local assembly, and greater stability and coolness of four wooden handles that serve also as legs. Without question, there will be further improvements as the number of users increases and they provide feedback. For example, households using the Quad TLUD stoves in various refugee camps could make suggestions that outsiders might fail to foresee. Jigs, tools and methods for making flat-pack pieces are being prepared in the USA for availability to stove projects worldwide.

Material: Sheet metal and 4 wooden handles/legs

Cost: Mwoto and Quad TLUDs sell for approximately US$15 in Uganda, and should eventually cost less, especially if purchased in bulk as flat-pack pieces to be assembled by a local project.

Dimensions: Currently one size, but size can be easily changed: Height: 19” (48 cm), Square footprint 12 x 12” (300 x 300 mm); Fuel cylinder height 14 “ (36 cm) with diameters from 5 to 7” (12 to 18 cm).
Test results of Quad and closely related TLUD stoves such as Mwoto and Champion:

CO & PM Emissions: Consistently the lowest for any of the natural draft stoves that burn solid biomass.

Thermal efficiency: Range from 35% to 41% currently. Expected to go even higher.

Fuel consumption: 1050 to 1600 grams for a standard WBT of cold start plus simmer (respectably low).

Fuel types: TLUDs can utilize a wide variety of low-value chunky dry biomass fuels (e.g. corncobs, tree seed pods, nut shells), including briquette pieces that can be locally produced from unused biomass. “Stick-wood” is not a common TLUD fuel, but can be used vertically as “wood segments.” Vertical segments also with papyrus reeds, bamboo, etc.
Options: The Quad can be made as a TChar variation for ease of using the created charcoal as fuel in a charcoal stove or as biochar that is added to the soil.

For further information, contact Dr. Paul Anderson at: Email: psanders@ilstu.edu
and visit www.drtlud.com for future updates about TLUD gasifier technology.

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