[Stoves] Questions on coal-burning possible TLUD

[Frank Shields]

Dear Crispin, Paul,

I think the advantage of coal over biomass, and the reason it can be 
made to burn so clean, is because coal is a very consistent product and 
stoves can be designed and adjusted to optimize to burn it. Biomass 
(even the same material, differs in texture, moisture, structures 
(lignin, resins etc) creating different burn patterns as the combustion 
process evolves. Pellets and compressed, processed  fuels should act 
more like coal -I think.

But going from open fires and poorly designed biomass stoves to well 
designed stoves like what Paul designs is a big move forward. And then 
adding the added cost and energy to pelletize or density biomass for a 
different stove may be another big move forward.

Regards
Frank



Crispin Pemberton-Pigott wrote:

>Dear Paul
>
>I can't see ANY reason to dismiss as relevant a stove that is a) on the
>market, b) well made, c) has extremely low emissions (far lower than nearly
>every stove you are likely ever to see).
>
>The Global Alliance was very clear in saying that they are not only working
>with biomass stoves. Neither is this discussion list. 
>
>One of the realities that is already accepted (thank goodness) by the Global
>Alliance is that the millions, probably hundreds of millions, of coal
>burning families will continue to do so, certainly during the coming decade.
>There are no viable alternative fuels visible at present at scale.
>
>One often hears about 'propane is a clean alternative'. There is already a
>global shortage of propane and it is completely unsuited to most rural
>applications.
>
>Many proposals say we should expand the use of biomass to include non-wood.
>This is great, as long as there is something available. Coal is well suited
>to long distance delivery to urban areas. Wood usually is not.  The problem
>has been that coal has be so abused as a fuel that almost no work has been
>done on burning it cleanly. It is routinely called a smoky, stinking fuel.
>Just like paraffin was and is, before super-clean stoves were developed in
>the past few years.
>
>It was not that long ago that a large meeting called by ProBEC was told the
>same thing about biomass, that wood was inherently smoky and we have to get
>rid of it and use nice clean electricity and propane. You get my drift? The
>difference between then and now is focussed product development and proper
>lab testing that shows how and when the fuel is burning properly. The
>advances have been rapid as the 'clean section' of a test is stretched to
>include the whole burn.
>
>A great deal of credit for cleaner biomass burning has been given to fans.
>This is incorrect. Yes some clean stoves have fans but it is better
>combustion that is the cause of clean burning and a fan is one way to
>produce the conditions necessary. We have to keep out eyes on the ball. Fans
>are one of several means to an end.
>
>The continued abuse of coal as a fuel is driven by two significant
>misunderstandings: first that cooking and heating stoves use large (meaning
>significant) quantities of it relative to other uses for coal, and second,
>that it cannot possibly be burned cleanly in small stoves.
>
>The amount of coal burned as domestic fuel is a tiny % of the total and the
>inherent emissions from it (trace metals etc) are a pale, insignificant
>quantity. The problem is, the combustion emissions from crummy stoves
>basically roast the coal until there are glowing lumps of coke. They smoke
>in the process, even though the smoke is simply unburned fuel.
>
>I am assembling a comparison between some coal stove tests which I will
>circulate. It shows that based on a reasonable baseline (good baseline
>stove, properly operated) there are three completely different stoves
>(different burning methods) that touch 99% reduction in particulate
>emissions. Surely that is worth our attention when thinking of improved
>stoves on a global scale.
>
>  
>
>>And your information leads me to have little interest.  
>>    
>>
>
>Frankly that makes little sense. Please take more interest.
>
>  
>
>>($200, heavy, ...
>>    
>>
>
>Many people pay much more for their stoves. The poor man's coal stove in
>South Arica is about R2000-4000. They are bought on time from large stores.
>People expect cast iron for that price and that it will last 50-100 years.
>
>  
>
>>...high-internal heat would pyrolyze biomass in perhaps irregular ways,
>>    
>>
>nobody is using it with biomass - because it is not intended for biomass and
>the Turkish users have learned that lesson well)
>
>We do not know how the stove would react with wood if slightly modified. It
>may be an excellent platform for making durable, clean stoves. Let's find
>out.  The fact is that there is a subsidy available in Mongolia large enough
>to make these stoves cheap, for the first 130,000 units.
>
>  
>
>>So, let's not get excited as if this recognition of a stove from  
>>Turkey will alter the past, present or future of TLUD cookstoves.   
>>    
>>
>
>I am not sure what that means. We are trying to alter the future. The past,
>known or unknown, is what it is.
>
>  
>
>>TLUD stoves (as a NAME, not as a process) 
>>    
>>
>
>What?? Come on.... If we take your own characterisation of the types of
>stoves, the fuel's chemistry or age is not part of it.
>
>  
>
>>....have characteristics that go beyond top lit and updraft, and the name
>>    
>>
>refers to devices that use biomass, not fossil fuels.
>
>You have chosen to interpret it that way. I view the classification of where
>the fire it lit and in which direction the fire proceeds to be very useful.
>There is nothing inherent in the classification that implies certain fuel
>types. You are basically appealing to your own authority on this issue.
>
>  
>
>>In my opinion, the "Silver" unit is a very nice distraction from all the
>>    
>>
>work being done on biomass burning TLUDs and other micro-gasifiers.
>
>It is nothing more than a solid, well-made cast iron TLUD stove. I guess the
>small ones are micro-gasifiers.  The one I tested is cleaner burning that a
>biomass micro-gasifier.  That might irritate some.  For all I know it will
>burn goat dung really well. I will try it, with modified secondary air. You
>don't have to be distracted from what you are doing. And leave it to those
>who wish to, to proceed without dissuasion about relevance.
>
>  
>
>>But as it stands now, the discovery or re-discovery of this Turkey product
>>    
>>
>will have minimal impact on the progress needed for 
>  
>
>>the Global Alliance for Clean Cookstoves.
>>    
>>
>
>What??  It has not been 'discovered'. The sales guys pitched up in a new
>market and made a deal to sell stoves. It is you who they might yet
>discover. They are the formal sector, business as usual, efficient stove
>producers going back two generations. They are not a tangential offshoot
>being grafted onto the 'core stove world'. They were making high efficiency,
>clean burning TLUD stove before VITA wrote their handbook for heaven's sake.
>The products are not perfect. I made a small change to the ignition and
>operating procedure and dropped the emissions by more than half. There is
>still work to be done.  Incidentally during that test the emissions reached
>0.0 ppm CO and 0.000 mg/m3 PM 2.5 several times. Like the GTZ 7.5 coal stove
>(the only other one I have seen do that), it is net negative for PM
>emissions for many hours at a time - about 3/4 of the burn. That is, the air
>going into the stove has far more particulate matter in it than comes out
>from the stack. The stove is cleaning the air!
>
>I think that would be of great interest to the biomass burning designers
>because, based on lab tests, are no longer as clean as (any of several)
>really good coal stoves.
>
>Regards
>Crispin
>
>PS The fuel used is 26% moisture, 50% volatiles brown coal. So much for
>'inherent emissions' from 'dirty, low quality coal'. More like dirty, low
>quality combustion.
>
>
>_______________________________________________
>Stoves mailing list
>
>to Send a Message to the list, use the email address
>Stoves mailing list
>
>to UNSUBSCRIBE or Change your List Settings use the web page
>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
>for more Biomass Cooking Stoves,  News and Information see our web site:
>http://www.bioenergylists.org/
>Stoves at lists.bioenergylists.org
>http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
>
>  
>