[Stoves] Charcoal burning, secondary flame vs no flame

Thu Aug 20 05:01:53 CDT 2015

Dear Crispin, 

If you are still in Indonesia right now,  would you be able to take more photos of the Improved  Keren  that would give a 360 degree view of the stove?   I agree with your statement  that the results you are getting with the Keren Super are possible with my stoves.  Perhaps  even better results.    I hope one day soon that the CSI standards would come to the Philippines as well. 
I now have the new clay and my potter is making more prototypes of my stoves.  The firing of these prototypes will be delayed to about the last week of September to allow for the "curing" of the repairs done to my kiln.  I would like to have a verbal discussion with you on Skype -- this would be more efficient and convenient  for me as I will be in the Chilcotin smoking salmon next week.   Is this possible with you?   I do have high speed internet there now so I can receive emails, teleconference and conduct cooking experiments in the Philippines via the internet, among others. 
Thank you so much for your help. 

Warm regards, 
Rebecca 

----- Original Message -----

From: "Crispin Pemberton-Pigott" <crispinpigott at outlook.com> 
To: "Rebecca A. Vermeer" <ravermeer at telus.net>, "Andrew Heggie" <ajheggie at gmail.com>, "Paul Anderson" <psanders at ilstu.edu>, "roberto poehlmann" <roberto.poehlmann at grupogtd.com>, "Ronal W. Larson" <rongretlarson at comcast.net> 
Cc: "Discussion of biomass" <stoves at lists.bioenergylists.org>, "Rebecca Vermeer" <ravermeer at telus.net>, "Kelpie Wilson" <kelpiew at gmail.com>, "Art Donnelly" <art.donnelly at seachar.org>, jonnygms at gmail.com 
Sent: Monday, August 17, 2015 7:01:03 AM 
Subject: Re: [Stoves] Charcoal burning, secondary flame vs no flame 

Dear Rebecca 

I have some news for you regarding the pot rest height changes we investigated at the Stove Test Camp.  

‎The plan was to lower the pot rest height until the excess air level inside the fire chamber was 'about right'. This is pretty much the only way to control that value with a simple clay stove. Lowering the fuel entrance helps.  

You will recall we looked at the type of flame, it's vigour and the colour as indicators that the EA was about optimised.  

The ideas were rooted in a stove now called the Keren Super which is an experimental stove developed in Yogyakarta. It is a very inexpensive stove made from clay purchased from roof tile makers.  

I can report that the combination of adding a grate (to burn most of the char normally formed on the floor of a grateless stove), opening an air hole at the back, lowering the pot rests to 7mm, lowering the fuel hole height and making is a little narrower had the effect of improving the fuel efficiency.  

Using the CSI burn cycle with its sequence of four power levels, the overall efficiency (similar to the fuel efficiency) increased from 16% to 27%. The average is a little above that value.  

The YDD lab reports ‎that the time to boil increased but I did not find this to be so in a series of experiments made using an early prototype in June. With 45% fewer sticks in the fire, it matched the original time of 15 minutes for 5 litres. So let's watch that performance over time. It is between 15 and 20 minutes so far.  

The stove costs about $0.50 wholesale and maybe $1.50 retail. It's a lot of bang for the buck. The CO level gets one star (under 12 g/MJ delivered) and the PM is still being checked. It has scored under 300mg /MJ delivered.  

I believe all these results are possible with the 'Rebecca stoves.'‎  

Keep on burning 
Crispin in Lombok Island 

Dear Friends, 
I would like to share with you and all in Stove List, two videos and their respective photo albums  on the Cooking Performance of the Whirly Pinay TLUD Stove which I am developing;  and the Baking Performance of the Bingka Clay Oven heated by a Whirly Pinay TLUD stove.  But before discussing these 2 videos  and photo albums, I would like to thank Crispin and Andrew for sharing their views on the amount of CO that is generated in burning residual char in a stove (such as my Eco-Kalan and Whirly Pinay TLUD Clay Stove). 

>From Crispin: 
I have taken many measurement of CO/CO2 at various stages and what I see is that in the late burning stage the CO/CO2 ratio is not as bad as many assume – even in a poorly sheltered fire. The combustion of char tends to stabilise at 12-16% CO/CO2 with 14% being common in a ‘cold fire’. It is not true at all that the carbon mostly emerges as CO. 

To get high CO one has to ‘force’ the production of it such as in a hot, choked, air-inadequate fire. Then one can see the CO/CO2 reach 30% or more. It is not uncommon to see 25% in poorly constructed stoves, but not at the end. Little well-aerated char fires stabilise in that 12-16% range. 

It is often said that “the CO is really high”. That is relative true compared with a really good fire, but CO is highest in hot, bad fires where there is enough energy to create a high burn rate and poor mixing or poor combustion. 

>From Andrew: 

Your palangay way looks like it is a good candidate for retained heat 
cooking. 

Even so the method you mention of allowing char embers to burn out and 
produce the remaining necessary heat need not necessarily produce a 
lot of CO. This is because the conditions for a full CO generator 
require the char to be hot and deep so that oxygen first encountering 
a hot piece of char will dissociate on the char surface and form CO2, 
this CO2 then would only be reduced to CO if it encountered another 
bit of hot char in the absence of any other oxygen, this reduction to 
CO is also endothermic, so it lowers temperature. Hence if the char 
bed is shallow and heat is being radiated from it little CO need form 
but some always will. 

CRISPIN & ANDREW, THANK YOU! - I take comfort from what you have shared.  It encourages me to go on practising the Philippine cultural  tradition of cooking rice or corn last  the "palangay" way.  

I have one last question on the CO.  How quickly (or slowly) does the CO change to CO2 once it is released to the open air through a chimney or by diffusion from a stove? 

Now back to the Whirly Pinay TLUD clay stove videos and photos. 

Cooking Bam-i & Rice with Whirly Pinay TLUD Stove, Eco-Kalan Project, June 11, 2015 

https://youtu.be/HZhHzQUfrGk 

 June 11, 2015 Cooking Bam-i and Rice with Whirly Pinay TLUD Clay Stove,  Eco-Kalan Project 

https://plus.google.com/photos/113101643783889350444/albums/6159008359940818145 

My Comments: 

1.  Cooking with the Whirly Pinay can be fun when you start with a "dead" and dry firewood and a strong fire.  We don't have a moisture measuring device at Felipa Beach so we put our pre-cut wood  in the sun for at least 3 days and store  the dry fuel in a covered container.  Dry firewood makes starting a strong fire easy.  We use kerosene to start a fire and make sure there is sufficient primary air to produce a strong flame before containing the wood gas in a combustion chamber with inlets for the secondary air.  I prefer to close the supply of primary air during pyrolysis and to open it to burn the char when cooking rice or soup with leafy vegetables or fish and other seafood at the end.  

2.  As a cook using firewood for fuel,  I make my decisions on what to do with the char on the basis of its best use.  A burning char is best for keeping the food hot without burning the food at the bottom of the pot until it is time to serve.  It is best for foods that cook readily and do not require high heat like omelettes, shrimps, and sauces. 

3.  As a baker using a Bingka Clay Oven heated by a Whirly Pinay Stove fuelled with wood, I make my decision on what to do with the char on the basis of its best use also.  In the baking I have done so far, the oven temperature has to be around  500 degrees Fahrenheit.  Burning the char cannot produce sufficient heat to maintain that high a temperature so it does not make sense to burn it.  Instead,  I save it and mix it with sand and organic matter of which I have plenty of at Felipa Beach.  Have a look at the video and photos below. 

  Baking Hopia with Bingka Oven & Whirly Pinay TLUD Stove, Eco-Kalan Project, July 30, 2015 

  https://youtu.be/vHfSjZINxUA 

July 30, 2015 Baking Hopia with Bingka Oven and Whirly Pinay TLUD Clay Stove, Eco-Kalan Project 

  https://plus.google.com/photos/113101643783889350444/albums/6178681391871082273 

Warm regards, 

Rebecca Vermeer 

Eco-Kalan Project in the Philippines 

----- Original Message -----

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