[Stoves] stoves and credits again

Fri Sep 29 23:33:18 CDT 2017

Dear Paul

Again I feel you are imposing restrictions on how products should work. Recycled char can definitely be burned. If you have pellets that yield 15-20"% of initial fuel mass then definitely some of the char burned. That establishes the principle that TLUD‎s can burn char.

The stoves that recycle char to the next cooking session burn a large amount of the total char such that the mass 'carried forward' is about the same ea‎ch time. This establishes that the total char produced, net, each replication is completely combusted.

All that is needed is to increase the gasification rate until there is significant char gasification. ‎This does not hold for all models nor all fire powers. Some produce more than they can recycle so a portion is lost, or retained for other purposes. In the fuel consumption calculation that is fuel fed, meaning more is needed next time. For example a stove may produce 20% char from a mix that was 90% fresh pellets and 10% old char. In that case half the remaining char is not used next time.

Stoves that do this have been made and sold in Indonesia for several years.

While there is a 'purist' group holding that char is produced and not burned, and there are stoves like that, it is not a general case. It is particular to those products with a low temperature gas production rate. The cleanest stove we tested was like that. The most efficient was like the case above, in the high 30's, assessed on the Central Java cooking sequence.

The Rocketworks stove from South is in the same efficiency range. It is a stick burner‎ with a novel grate and both preheated secondary and tertiary air, i.e. not a gasifier nor semi-gasifier.

Regards
Crispin

‎
Crispin,

I am sure that Bill and Gordon in New Mexico (and others including mysel\f) will appreciate more info (details, photos, sizes, etc) about the continuous TLUDs with bottom feeding.   Please try to provide.

When mixing in the previously made char into the future batches of fuel, there are two concerns:

1.  Cannot mix in hot, glowing char (which would ignite low into the columnof fuel),  Therefore must be extinquished, which is an extra step.

2.  Char from a TLUD at whatever temperature of pyrolysis will essentially be "inert" material into a next batch to be pyrolyzed at the same temperature.   No gain.   Just filling space.    [[ But one exception:  created char can pick up some of the volatiles that are rising through it.   Those volatiles would be elegible to be released for making energy in the second round.   As far as I know, those volatiles would be a very very small percentage of the energy in the processes. }}    So why bother to do it, UNLESS the intention is to burn the created char (which should not be done in a TLUD).

I agree that anyone is allowed to test and experiment with any methods and materials.   What we are awaiting are reports of adoption of methods etc by significant numbers of appropriate users.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.com<http://www.drtlud.com>

On 9/28/2017 10:29 AM, Crispin Pemberton-Pigott wrote:
Dear Paul

Thanks for the ideas about char. I want to correct a couple of impressions.

>And users can continually drop in  more fuel, which is "trickle feeding"and requires user attention.   TLUDs are batch units.

This is only true some of the time. TLUD burners are frequently (often, not rarely) built at small industrial scale using batch-push feeding from below. I was surprised to find that the Stove Development Centre in Ulaanbaatar has been making a number of these units – the surprise coming from the fact that none of the domestic candidate stoves had used this system. I saw one being repaired in August.  Being a TLUD does not mean it has to be a single batch unit.

The char or charred fuel is not placed on top of the fresh fuel – it is mixed in and forms part of the fuel. I don’t know what the upper limits of content are, I believe for different stoves there are different limits. The HTP spreadsheet was modified in 2013 or so to accommodate this sort of ‘limited ability to recycle processed fuel’ and still produce the correct ‘as burned’ (AB) fuel analysis that forms the basis of the chemical mass balance calculation.

Next, with reference to the recycling of fuel from one burn to the next:

>Also, apart from the lab testing, is there evidence that the Indonesian cooks are actually using the stove as it was being used in the lab?

That is not up to the lab performing the test. If a manufacturer comes out with a novel method of construction and operation, it is up to the lab to test it as designed, not to speculate about home someone in future might use it.

For a project it makes a difference and a project might not adopt a stove for promotion if the cultural conflicts with how it works. In short, the testing does not stand in the way of innovation. There is a clear separation between the invention and testing of products from the projects that may or may not use them. I realise that there has been a confabulation of projects and test protocols in the past. That should end. A test method should be technology neutral.

That said, a test protocol specific to a project is also valid. On project I was associated with required that the stoves be mis-operated and the performance reported because ‘obvious misuse’ is an accepted risk and we wanted to know the implications.

>These stoves can be operated in  different ways.

Yes, but it would be good if you did not limit the operation of a TLUD to a batch or trickle-feed mode. There are other products around. TLUD coal and pellet and briquette burners are quite common. I expect one day the TLUD promoters will accept this as a standard operating technique because it overcomes several of the attested shortcomings of batch-loaded stoves.

>How many of each of those units (Todd's or the Indonesian ones) are in daily use in  households?   I hope that the numbers of users are VERY high.   Please send details.

I am not sure stoves are listed by operating mode. Those that are claimed to be operating as TLUDs with recycled fuel could be identified by brand and the numbers (probably) extracted from the CSI Indonesia aggregated sales numbers. It is in the thousands I suppose. I am not the one to ask.

Regards
Crispin

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