[Stoves] Vesto emissions - TLUD with Pellets

Sat Jan 3 18:57:28 CST 2015

Dear Ron

I do not remember the char mass in the Vesto tests. Normally the char is burned after the wood gas is coming to an end. That is accomplished by opening in the primary air /before/ the gasification is done. This sets up a charcoal gasification process.

The purpose of this sequence had nothing to do with trying to make char. It is was to create a stove that has a considerable degree of power control without removing fuel. Gasifier style burning can at any time be changed from whole fuel burning simply by increasing the air supply.

Similarly wood stacked in the chamber and burning normally can be choked of air and turned into a gasifier, though not one with an MPF‎.

Regards
Crispin

Crispin and list:

        Many of us interested in TLUDs would like to also hear the weights of input pellets and output char, and your reported efficiency for this test.

Ron

On Jan 2, 2015, at 10:52 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:

> Dear Friends
>
> Although the stove has been around for 10 years, there is never anything heard of the emissions performance of a Vesto so I have decided to send a little to the group.
>
> I found a really old Vesto (2004) at YDD in Yogyakarta a couple of years ago and ran it as a TLUD with locally produced wood pellets to see how it worked.
>
> This is Prianti Utami holding the sample tube.
>
> <image001.png>
>
> This is the steady state combustion:
> CO2 5.6% (by calculation)
> Excess air ≈290%
> CO concentration 183 ppm
> CO/CO2 ratio 0.03%
> High power heat transfer efficiency ≈35%
> Low power heat transfer efficiency (burning remnant charcoal) >60%
>
> <image003.jpg>
>
> The combustion chamber has a lever-controlled primary air supply with free flowing secondary air plus a portion of the primary air is preheated and supplied as secondary (sorry, but it is complicated).
>
> In later years the secondary air supply holes were reduced in number by 25% which limits the excess air even further.  It reduces the high power limit but improves combustion generally.
>
> Note to Saloop and others: This stove architecture with descending preheated primary (and/or secondary) air has proportions that are dictated by the % of oxygen in the atmosphere, the density and the thermal mass of air. In other words, the entrance heights and primary/secondary air split follows a set of ratios dictated by The Earth which taken together with the oxygen content of the fuel itself, show where the optimum performance lies.
>
> Here is a picture of the flame from a Vesto burning switchgrass pellets in TLUD mode (it can also burn in a regular updraft mode):
>
> <image006.jpg>
> Note the complete absence of any central spire of flame.
>
> Solid fuel combustion regulations often seek a CO/CO2 limit of 2% in part because it is (apparently) not considered dangerous given ‘standard’ air turnover rates and also because it is achievable. Lately the performance of wood-fired heating stoves and cooking stoves have greatly exceeded these standards when using pellets (processed fuel).
>
> Given that may ‘high end fuels’ like LPG and kerosene and ethanol are highly processed, it seems reasonable that the wood burning community demand ‘equal treatment’ meaning that there is no sound reason for solid fuels, as a group, to be rejected as ‘modern fuels’ as has apparently been done in the Nov 2014 WHO document which basically claims they are inherently unable to burn cleanly.  There is mention repeatedly in documents that ‘only stoves with a fan’ can burn biomass cleanly which is disproven by this one measurement (if it was necessary to demonstrate it at all – there are lots of other examples).  The biomass stove community as a group needs to understand this and its implications, and demonstrate how these widely available, inexpensive and low cost fuels can be applied safely and consistently to cooking and heating tasks.
>
> Regards
> Crispin
>
>
> Crispin Pemberton-Pigott
> crispin at newdawn.sz
> Managing Director
> New Dawn Engineering
> www.newdawnengineering.com
>
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