[Stoves] Distillation and oxidation Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )

Sat Jan 6 21:26:53 CST 2018

Dear Ron

I understand that you have been reading a description of a top loaded updraft gasifier in continuous operation. It produces high energy gases. It is NOT like a TLUD which ‎produces low energy low tar gases with about half the calorific value per cubic metre.

The TLUD gasifiers that are sold in India which are continuous (not all TLUD's are batch loaded) use augers below the oxidation zone, typically raising the active 'deck' one or two meters at a go. I posted photos some time ago of such a gasifier in Cambodia. Tom Miles said there are about 225 of them in the country. The fuel is rice hull and they make rice hull char.

The fact that the description of the top loaded updraft gasifier does not match that of the TLUD batch or continuous gasifiers does not change the names or processes taking place in the fuel.

Regards
Crispin

Andrew and list:

1.   A few days ago I tried to follow this story, which starts at Crispin’s site as http://www.newdawnengineering.com/website/library/Papers+Articles/Chakrabarti,%20H/BIOMASS%20GASIFICATION%20Hirendra%202013.pdf<https://nam03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.newdawnengineering.com%2Fwebsite%2Flibrary%2FPapers%2BArticles%2FChakrabarti%2C+H%2FBIOMASS+GASIFICATION+Hirendra+2013.pdf&data=02%7C01%7C%7C6144bc4af4ca491a8fb708d5556825f0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636508828155930872&sdata=vohAKqqBa7AFa4DUq1odhYLqCfWOcY%2FU1hhIO94xiLw%3D&reserved=0>
and is also found at  http://www.cmpdi.co.in/mineTech.php<https://nam03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.cmpdi.co.in%2FmineTech.php&data=02%7C01%7C%7C6144bc4af4ca491a8fb708d5556825f0%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636508828155930872&sdata=U4b8EWKFzBhQ9jUsdKzfRJn6NvoVDlEOtCcjbjKcYEA%3D&reserved=0>.   But I couldn’t find a way there to get to this particular article.  Pperhaps Crispin can tell us if there is a repository for “Minetech”.  CMDPI stands for Central Mine Planning & Design Institute Limited,  and is a subsidiary of an Indian government owned profit making firm.

2.  “Minetech” is an in-house quarterly - primarily dealing with the coal industry in India, through the coal (not a trade) organization CMPDI.  I think it safe to say they rarely publish on biomass.  But I’d like to see what else might have been published by “minetech” of this type.  And to learn more about Dr. Chakrabarti.

3.  From Crispin’s site we read (my added emphasis):
Pyrolysis/ Distillation of Biomass: The gas leaving the oxidation reduction zone at a temperature of about 550- 700oC passes through the dry biomass distilling it into three products namely biochar, tar & watery substance called Pyrolignious liquid & gases containing Carbon dioxide, Carbon monoxide, Hydrogen, methane, little quantity of oxygen, Nitrogen etc. In this zone the temperature is reduced to about 300 to 350oC.

4.  Re the first emphasized words:  “passes through the dry biomass”  - this is clearly referring to something totally different from a TLUD.  I hope Crispin can describe what geometry is being described here.

5.  I can believe that gases leaving any char go down in temperature, but in TLUDs there is nowhere near this much decrease to 300-350C.  Looking in is usually a bright red charcoal - not “dry biomass”.

6.  I am in agreement with Andrew below that ‘distillation” doesn’t make sense with TLUDs - but there certainly are commercial operations with biomass where the term “distillation” makes sense - and maybe even with char production - but I am unaware of any stove application where that has been attempted.

Thoughts?

Ron

On Jan 6, 2018, at 4:37 PM, Andrew Heggie <aj.heggie at gmail.com<mailto:aj.heggie at gmail.com>> wrote:

On 6 January 2018 at 21:39, Crispin Pemberton-Pigott
<crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:

The evidence from the distillation of biomass to produce liquids and ‎gases shows that there is a conversion of biomass to CO2. Paul asks if the C is completely separated from the OH. It probably does now and then but it is not material. If it happens the heat is lost then regained, lost again and regained as the chemistry rapidly changes. What we do know is that in the end, there is only a net heat released from the biomass at 360C, and that the rest of the time the chemical changes leading to the gaseous products are energy-neutral. This of course is in the absence of air.

Crispin as you are the only one to use the term "distillation" in this
way I wonder if your gasifier expert is a native English speaker?

Too my mind distillation applies to the creation of a vapour and its
subsequent condensation, either in a simple condenser or a
fractionating column, to a purified liquid. In TLUDs we produce a
pyrolysis offgas that is a mixture of gases and vapours with maybe a n
aerosol of solid particles. This is then subsequently burned in a
secondary flame so no condensate is recovered.

We have known of the exothermic part of pyrolysis for years, Tom Reed
mentioned it 20 years ago, but does the heat at 360C amount to less or
more than that necessary to raise the dry wood from ambient to 360C?

Andrew

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