Comparative VS softwood pellets, advice and feedback?

[Christophe]

For liquid water, the specific heat is 4 J · kg⁻¹· K⁻¹.
For vaporization, the enthalpy is 2 Jkg⁻¹

Passing 1kg of liquid water at 20 ° to steam at 100 ° therefore requires 80 * 4185 + 2264000 = 2431400 675 J = XNUMXWh

Uh good reasoning, I arrive at 722 Wh but that does not change much in the final result ... logically it would also take into account the rise in the temperature of the steam, right? But up to what temperature? That of smoke or combustion?

In total, 1% more humidity represents about 50Wh / kg less.

It's a lot less than I actually thought *, finally 1% of water, it is approximately 1% of PCI in less... but I had never done this reasoning ...

Note that in the case of moisture uptake, it is "only" 6,75 Wh because the weight of pellets burned has also increased by the quantity of water absorbed.

No understands?

* I happened to burn wood that was not dry enough and it was catastrophic ... much more than the 20% difference (but it's very subjective as a remark ...)

[Christophe]

2) YOU take a large dish that goes in the microwave. You weigh P1. You put a layer of pellets. You weigh P2.

Then you spend a minute in the microwave. You leave. You weight. P3. You mix. I don't know if it's a minute. Take smaller times and stay close by, so that it does not catch fire !!!

You start again until: a) the weight no longer moves; b) the pellets start to "brown". We can then consider that they are dry.

You calculate the quantity of water evaporated: weight of the pellets P2 - P1. Then you calculate the "losses" ...

Can we flame pellets in the microwave ??? Interesting to know!

For the method, ok I understood but why do it in the oven not microwave? Wouldn't that be less risky in the conventional oven (but certainly a little longer ...)?

[Ahmed]

The pellets can contain a little starch to increase their cohesion (in the case of a manufacture based on hardwoods, because they contain less lignin than softwoods).
It is possible to obtain an inflammation of the wood by raising its temperature, in a microwave or by other means (from 250-350 °, depending on the species).

[sicetaitsimple]

Uh good reasoning, I arrive at 722 Wh but that does not change much in the final result ... logically it would also take into account the rise in the temperature of the steam, right? But up to what temperature? That of smoke or combustion?

Up to that of smoke.
Even if the water vapor is superheated (it is) in the combustion gases, it will give up in the exchange body of your boiler (or a stove) this energy, between the state "gas of combustion outlet combustion chamber "and the status" combustion gas inlet exhaust duct ".

The inevitable losses through the exhaust pipe being by far the main losses of a combustion system.

[Did67]

These losses are reduced when we can have condensation (which is my case), with fumes released at 35 to 55 ° ... And part of the condensed vapor ...

[Did67]

* I happened to burn wood that was not dry enough and it was catastrophic ... much more than the 20% difference (but it's very subjective as a remark ...)

Attention, here we reason "thermodynamics". We assume that even wet, the wood would be perfectly burnt to determine its PCI.

In reality, damp wood burns badly, combustion is bad and in addition to the "thermodynamic losses" linked to the evaporation of water, there is also the fact that in your device, it "smokes", it "browns", it "spits out particles" and lots of "pungent, irritating" gases (stay next to a scout fire, under the smoke and you know what I mean). All these are unburned organic molecules!

This is the real disaster of insufficiently dry wood burned in non-controlled combustion devices (stoves, fireplaces, etc.). The use of wood then becomes "not green" at all, even if it is almost neutral in fossil CO²! When I go down to the village, I am assailed, in winter, by a vague odor which irritates the throat. If it was Renault, we would put him on trial! But as it is all the individuals, some of whom think they are "green" by heating with wood ... [Note that some cities prohibit heating with wood in too rustic appliances ...]

[Did67]

Can we flame pellets in the microwave ??? Interesting to know!

For the method, ok I understood but why do it in the oven not microwave? Wouldn't that be less risky in the conventional oven (but certainly a little longer ...)?

Because the "microwave" heats up inside, and instantly. "Scientifically", the humidity measurements are made in an oven, for x hours, at I don't know how many degrees (120 ° C and a few I think) ... So theoretically, you can in the oven. IF you want to stay nearby, for 24 hours ...

The "microwave" is a simple, approximate method. When I was only talking about pellets here, I had found a document from ADEME which "validated" this method fairly well, which gave fairly reliable results for a first approximation. Of course, in order to sue a manufacturer, standards must be applied, the oven, etc.

[Christophe]

Ok i will try some

[fabio.gel]

Hello Christophe

If your boiler is set on hardwood, do not change especially (if you have access to the admin code of the motherboard to change the settings).
I had done the test on my old pellet stove that is set on softwood, poor combustion result and much too much ash.

In return for experience and for not the cities, I use for two years granule from Castoche, I await the castochefolies to take a ton (about 240 €).

The notice : http://www.castorama.fr/media_aux/651553_a1.pdf

Fabio

[Gaston]

Note that in the case of moisture uptake, it is "only" 6,75 Wh because the weight of pellets burned has also increased by the quantity of water absorbed.

No understands?

In the case of moisture recovery, we go from 1 kg of pellets at 7% to 1,01 kg of pellets at 8%.

Water does not replace combustible material, it comes in addition.
1kg of combustible material remains which always produces the same energy, and a small amount of this energy is used to heat and evaporate the additional 10g of water.