Avoid dark brown tar or in a wood stove or boiler

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Christophe
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Avoid dark brown tar or in a wood stove or boiler




by Christophe » 28/01/09, 10:10

How to avoid limiting tar or tarring? And limit at best the inevitable condensation (dew point)?

Some response information in this Buderus document: maintenance and use of a wood boiler Section 8.9.

If you have any other tips or document to complete?

ps: this subject is not innocent, we just had to disassemble and sweep the 1er ducts of the fireplace of our deom (after that is more). It was amazing how dirty it was :( Yet ... we use 95% briquettes of compressed sawdust (so very dry a priori) ...
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by Cuicui » 28/01/09, 11:04

For soot I do not know, but if bistre flows into the stovepipe, it is a sign of a very good performance: fumes and steam are at very low temperatures and condense in the pipe.
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by Christophe » 28/01/09, 11:14

Cuicui wrote:For soot I do not know, but if bistre flows into the stovepipe, it is a sign of a very good performance: fumes and steam are at very low temperatures and condense in the pipe.


Yes, but it does not mean that we burned shitwood ... and I know that I burned it last winter!

In fact, I justly estimated the performance of our deom after cleaning: https://www.econologie.com/forums/rendement- ... t6977.html

Well I admit that there are parameters of the test to review (see the subject in question, I would do a test) but it is still dismal as a result! 24% !!! Image

Un Image must not be far from this yield!

I found that at low T ° the deom had a better yield (normal) but low T ° of water = boring and compulsory tarring = decrease of the yield with the duration ...

So in the end we are in a somewhat paradoxical situation: low smoke temperature = better efficiency = yield degradation ...

The Buderus doc advises a T ° of DHW back to the 65 ° C boiler to avoid the bistre. In these conditions, I think, that the performance of the deom would pass below 15% !!! : Mrgreen: : Shock:
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by loop » 28/01/09, 12:30

Hello

I did not look at the doc but do we talk about recycling valve? Its role is to guarantee a minimum return temperature to the boiler, regardless of the flow rate of the circulator since the internal valve is thermostatic.

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Re: Avoid the bistre or tar in a stove or boiler b




by Did67 » 28/01/09, 12:52

Christophe wrote:... yet we use 95% briquettes of compressed sawdust (so very dry a priori) ...


The so-called "dry" wood is 15 to 20% humidity. The sawing of wood is often done at higher rates ... So if the sicure is compressed without being dried, we are in rates of this order (at a minimum).

People are always surprised to learn that flour is about 15% moisture!

Then all the complication of the regulation of the fire and the lowering of the temperatures of the gases (to increase the yield) are added ...
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by Did67 » 28/01/09, 13:02

Christophe wrote:
The Buderus doc advises a T ° of DHW back to the 65 ° C boiler to avoid the bistre. In these conditions, I think, that the performance of the deom would pass below 15% !!! : mrgreen:: shock:


Indeed, this is a fundamental point. And since you "touch" from time to time our exchanges about the Okofen regulations, this is one of the delicate points in the adjustment of pellet boilers. The regulation then manages the 3V valves so as to avoid condensations (closing below 65 ° C to "preserve" the temperature in the boilers). Besides the question of the bistre and therefore the gradual drop in efficiency, these condensations also raise the question of the corrosion of the boilers (except stainless steel - this is the case with the Okofen condenser, therefore "designed for")!

That's why I keep raising awareness of the problem that one can not compare the highly sophisticated automatic pellet boilers with vague tea kettles (as wood boilers are vaguely transformed for pellets, at the risk of mismanagement). lowering, starting, cleaning, oxidation, etc ...).

Not to mention the fact that in the conditions in which it forms the bistre, combustion is also an ecological disaster from the point of view of emissions (other than CO²) and it would perhaps be better to heat the gas ...? ???
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by Christophe » 28/01/09, 13:11

loop wrote:I did not look at the doc but do we talk about recycling valve? Its role is to guarantee a minimum return temperature to the boiler, regardless of the flow rate of the circulator since the internal valve is thermostatic.


Yes the doc speaks about it:

Condensation and formation of
tar can hinder the shelf life
of the boiler. Return temperature
must be 65 ° C minimum, the temperature
boiler water between 80 and 90 ° C.


- Install a thermostatic valve that
will prevent the return temperature from
to go below 65 ° C (elevation
the return temperature).


By cons on the deom, I do not have such a valve ...

Did67 wrote:The so-called "dry" wood is 15 to 20% humidity. Wood sawing is often done at higher rates


I think that it is drier than firewood, the machined wood is already planks and comes from far (exotic), the deep drying has time to do and for reasons of product quality final (buckling?) I think that the moisture must be well controlled before machining.

Well I just measured the hydrogenation rate of 5 briquettes (red padauk wood I think) with a humidimeter like this one: https://www.econologie.com/shop/humidime ... p-128.html

Results: between 11 and 13% therefore a little more than the "standardized pellets" therefore. I bet our non-standard pellets are over ... I'm trying this afternoon. But in both cases: pellets and briquettes will tend to absorb moisture from the air ... therefore ...

For the more precise rate of lumber, I will ask my briquette supplier the next time I see it.
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by loop » 28/01/09, 13:14

For the recycling valve, we talked about it here:

https://www.econologie.com/forums/recherche- ... t6264.html

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by Christophe » 28/01/09, 13:22

Thanks jviens to see:

Image

But this valve is apparently missing from the diagram I had inspired at the time of the assembly of the deom, namely:

Image

Fit this valve on our deom? I do not know if it's worth it, given the poor performance of our deom in high T ° (it's a boiler stove more than a boiler in fact) ... so I do not know ...

Because decrease the condensation and bistre, I want, but if it is to increase the consumption of wood by 2 or 3 I say no ... : Cry: : Evil:

I prefer to have a good sweeping every 2 years !! : Mrgreen:
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by loop » 28/01/09, 13:28

In any case, a poor performance on a boiler indicates that the calories go up in smoke in the conduit.
The exchange surface with the water of your DOEM is misplaced because on the outer wall, so far from the hottest point which is central.
Maybe you need to consider a modification to get the water where it is the warmest or add a circulation right out of the boiler on the pipe.
In principle if there is bistrage at the flames, it is destroyed by the heat.

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