KD Birch auction

[Bluecoat]

heh nice try, but I'm afraid you are wrong here sir.

Your statement that "The drier it is the less energy is wasted drying moisture out so the higher the heat output." is correct, BUT you forget one important factor. Wood becomes lighter when it gets drier. And heat output is calculated by weight.

1tonne of wood at 30% would lose 20% of its mass if you decide to dry it down to 10%. Yes, calorific value per tonne increases, but it looses 20% of its mass. I've done a simple study on optimum m/c on hardwood logs in the past and came to conclusion that ~22% m/c is what we need to aim for.

 

A cubic metre of firewood has the same at calorific value whether it be 40% or 0% moisture content. The important factor is the efficiency at which it burns. The lower the moisture content the more efficient it burns - simple.

[PremiumWood]

Are you suggesting that the water present in the wood has no detrimental effect to it's calorific output?

 

OK I'll try again...

according to FC document posted by Acilidon before

1tonne hardwood at 20%m/c would produce ~4300kw/h

 

if you dry it down to 10% m/c it loses 100kg of its mass, so it is no longer 1000kg- its 900kg

 

1000kg hardwood at 10% produces ~4700kw/h

 

 

so, 4700 x 0.9 = 4230kw/h

 

4230 < 4300 This is what I am suggesting.

[Alycidon]

At the end of the day the product will burn acceptably for most people immediately and will be acceptable for my customers by next autumn. If its cheap enough then fine.

Ironically there is another thread offering Ash started by premium wood as few days ago with MCs up to 30%. I guess their suppliers have not been up to scratch which for a new company is a shame.

 

I have sourced my own imported kiln dried this winter as an experiment, Birch currently at 12% - 18% externally and down to 7% internal, so that company gets its kilning right, got 16 crates left tonight so timed it about right.

 

A

Edited February 25, 2014 by Alycidon

[Alycidon]

OK I'll try again...

according to FC document posted by Acilidon before

1tonne hardwood at 20%m/c would produce ~4300kw/h

 

if you dry it down to 10% m/c it loses 100kg of its mass, so it is no longer 1000kg- its 900kg

 

1000kg hardwood at 10% produces ~4700kw/h

 

 

so, 4700 x 0.9 = 4230kw/h

 

4230 < 4300 This is what I am suggesting.

 

Buts thats hardly the same as your suggestion that 22% was the optimum MC, thats just plain wrong in my book, and the FCs book.

 

A

[PremiumWood]

we're going in circles here and its getting late. Good nite

[pete23]

does mould on said logs stop them burning

[Johny Walker]

we're going in circles here and its getting late. Good nite

 

a bit like the magic round about ,florance said to zeberdy :laugh1:doogul just laughed

[PremiumWood]

a bit like the magic round about ,florance said to zeberdy :laugh1:doogul just laughed

 

:thumbup:

[muldonach]

They could have been as low as 10% when leaving the kiln ..... however wood will only be as dry as its surrounding humidity , so will probably have absorbed water from the atmosphere , even indoors in the UK at this time of year ... so kiln drying was a bit wasted really , but will still be great firewood I would think !

 

 

Not at all sure that is correct

 

Wet basis moisture content for timber is absolute - 10% moisture content means exactly that - 1kg of timber at 10% will contain 100g of water.

 

Humidity in air is quoted as relative humidity or the percentage of the maximum quantity of moisture per unit volume which the air is carrying - 10% humidity means that the atmosphere can actually carry 10 times as much moisture as it is holding at present. The ability of air to carry moisture is a function of temperature - the higher the temperature the more water the air can carry.

 

There are several ways that moisture can be deposited on "dry" timber

 

1. immerse it in water

2. leave it out in the rain

3. In circumstances where the surface temperature of the timber is below the dewpoint of the surrounding atmosphere (the point at which relative humidity = 100%) the timber (or anything else) will "sweat" and moisture will be deposited on the surface and absorbed into the timber. Such circumstances can easily arise when a warm front passes over the UK following a cold or cool spell of weather. The same mechanism explains condersation on a window in a house.

 

It is perfectly correct to say that dry timber can re-absorb moisture and its mc may rise - but it is over simplistic to say that it will only be as dry as its surrounding humidity.

 

I have seen this adage trotted out several times, timber will dry as long as the relative humidity is below 100% and the surface temp of the timber is above dewpoint.

 

Cheers

mac

[SamWhiting12]

A cubic metre of firewood has the same at calorific value whether it be 40% or 0% moisture content. The important factor is the efficiency at which it burns. The lower the moisture content the more efficient it burns - simple.

 

Wrong- If this was true why wouldn't firewood merchants sell unseasoned wood???? Considering most stoves will be 80% efficient.

 

OK I'll try again...

according to FC document posted by Acilidon before

1tonne hardwood at 20%m/c would produce ~4300kw/h

 

if you dry it down to 10% m/c it loses 100kg of its mass, so it is no longer 1000kg- its 900kg

 

1000kg hardwood at 10% produces ~4700kw/h

 

 

so, 4700 x 0.9 = 4230kw/h

 

4230 < 4300 This is what I am suggesting.

 

I believe your figures are wrong. At 20%=4100kWh/t and 10%=4700kWh/t

 

900kg at 10%=4230kWh, 1000kg at 20%=4100kWh