RE: GAS-L: Biomass heats of combustion...

["Gavin Gulliver-Goodall" <Gavin@roseplac.worldonline.co.uk>]

Thanks John,
That's the order of magnitude I came up with first , then when I wrote the
mail it came out different! If you are correct then Joacim > (sun 12 Aug)
> But what is not mentioned is that the biomass involved must be 20% or less
> humidity! And of certain physical sizing.

Heat value for bone dry wood is 18 MJ/kg. Vaporisation heat for water is
2.26 MJ/kg.  Where did the 20% come from?  18/2.26 yields that the
theoretical moist level limit for combustion (gaining nothing in exergy) is
rather 800% (of dry weight).  Eight times as much water as wood? I can't
even imagine a piece of wood THAT wet.

> The physical sizing is resolved in straight-forward manner -- though for a
> "cost" -- pelletizing -- chipping -- hogging -- etc.
>
cannot be?
As for the 40% IT was and I was assured that the logs had been air drying
for 2 years!!!
Some fresh felled ash we chipped later came out at 25%wb so there we are-
My experience in the UK is that fresh felled can exceed 60% regularly
depending on season of felling. - remember we mostly grow softwood that
nobody wants here in the UK and consequently import any useful timber and
also a lot of finished timber products.

I think the UK economy is entirely supported by people buying and selling
money- certainly there is little engineering or farming left to speak of and
the mines were closed years ago! Oops don't want to go off topic or I'll get
my fingers rapped (or burnt) again!
Thanks
Gavin

-----Original Message-----
From: John L. Seger [mailto:jseger@maine.rr.com]
Sent: Monday, August 20, 2001 20:32
To: Gavin Gulliver-Goodall
Subject: RE: GAS-L: Biomass heats of combustion...

Gavin and all,

You're far from being a dimwit, HHV and LHV seems to be one of the most
misinterrpreted concepts around; it gives everyone problems.

Your "bone-dry" HHV is 20900 kJ/kg. Since your wood is 40% moisture, you
have only 60% of this HHV available, or 0.6 * 20900 = 12540 kJ/kg (of wet
wood). However, you also need to evaporate all of the water in the wood.
So, for every kg of wood, you need to evaporate 0.4 kg of water! So, you
loose another 0.4 * 2250 = 900 kJ/kg. Therefore, the LHV is 12540 - 900 =
11640 kJ/kg.

BTW, 40% MC is rather high for 'seasoned' wood. Freshly cut biomass is in
the 40-50% range. Several months of outside drying should get down to the
20% level at worst.

Hope this helps.

John L. Seger


At 07:18 PM 8/20/2001 +0100, you wrote:
>Tom,
>Sorry for being a real dimwit, What is the relationship between HHV and LHV
>ie how do you do the sum?
>i.e. I have fuel (UK seasoned pine) with a moisture content of 40%wet
basis.
>taking the HHV as your average of 22.21 the LHV is 20.9 for oven dry wood
>so I calculated the net CV as 19.57MJ/kg Is this correct?
>
>Thanks
>gavin
>
>-----Original Message-----
>From: Thomas Reed [mailto:tombreed@home.com]
>Sent: Monday, August 20, 2001 18:12
>To: arnt@c2i.net; gasification
>Subject: GAS-L: Biomass heats of combustion...
>
>Dear Arnt and all:
>
>You said the heating value of bone dry wood is 18 MJ, but the HIGH heating
>value is  22.21 MJ/kg (LHV 20.9) (average for most biomass, but varies +/-
>2).  Trouble is you NEVER find bone dry wood, but it's easy to measure
>moisture content and correct the heat values.  Typical here in Denver is 7%
>moisture content.
>
>There are major tables of these values in our book,
>
>"Thermal Data for Natural and Synthetic Fuels", S. Gaur and T. Reed, Marcel
>Dekker, 1998 and you can find tables at my site www.woodgas.com
>both measured and predicted from the ultimate analysis.
>
>
>         Dr. Thomas Reed
>  The Biomass Energy Foundation
> 1810 Smith Rd., Golden, CO 80401
>303 278 0558; tombreed@home.com
>----- Original Message -----
>From: "Arnt Karlsen" <arnt@c2i.net>
>To: <gasification@crest.org>
>Sent: Sunday, August 12, 2001 8:36 PM
>Subject: Re: GAS-L: Combustion Vs Gasification
>
>
>> On Sun, 12 Aug 2001 17:44:49 -0500, Peter Singfield <snkm@btl.net> wrote
>> in <3.0.32.20010812174243.00917740@wgs1.btl.net>:
>>
>> > At 11:07 PM 8/12/2001 +0100, you wrote:
>> > >Heat value for bone dry wood is 18 MJ/kg. Vaporisation heat for water
>is
>> > >2.26 MJ/kg.  Where did the 20% come from?  18/2.26 yields that the
>> > >theoretical moist level limit for combustion (gaining nothing in
>exergy) is
>> > >rather 800% (of dry weight).  Eight times as much water as wood? I
>can't
>> > >even imagine a piece of wood THAT wet.
>> >
>> > Yes -- I always mess up when it comes to counting wetness in terms that
>can
>> > be understood by all.
>> >
>> > "Whole" Green wood is slightly over half water -- half wood (55%).
>> >
>> > 20% as in 20% water and 80% wood per pound of whole wood.
>> >
>> > >
>> > >Oh yes we have, several times. Fresh wood is no problem. Using fresh
>> > >cucumbers or jellyfish would be difficult though.
>> > >
>> >
>> > You know -- here in the tropics -- put up a tin shed and loosely stack
>wood
>> > -- dries to 20% in maybe one week or less when to sun shines.
>> >
>> > But talk about having 18 tons of biomass to dry every hour -- on the
>fly --
>> > is another problem. That takes one awful big tin roofed shed. Which --
>by
>> > the way -- only dries biomass when the sun shines. Not at night -- not
>> > during heavy overcast -- and not during the rains.
>> >
>> > But now -- being as small is beautiful -- and I have two rabbit diesel
>> > engines on the ground -- and would like to run one on wood gas to make
>just
>> > 3.4 kw power (the size of my present old Honda Genset -- converted to
>run
>>
>> ..these I believe are designed for 10 kW to Dooms Day, and
>> should do fine anywhere from your idle setting to ~25 kW.
>> Above that, it time for supercharging and a few mean tricks.
>>
>> > on Butane gas -- which is very economic here in Belize) --
>> >
>> > Am prepared to mount a distributor (all Volks diesel have the "slot" in
>> > place for the gas model distributer) and see no problem with adapting
>the
>> > injection hole for spark-plug.
>>
>> ..do.
>>
>> > Raising the head to lower compression is easy to -- as over head cam is
>> > belt driven.
>>
>> ..shoot for a 13.5:1 compression ratio, lower it if you
>> supercharge.  If you start grinding cams, try leaving
>> the inlet open _long_, as in "way past half way up".
>> Gives you a variable compression controlled by rpm and
>> the inlet charge inertia.
>>
>> ..on my mums VW Beetle, 125 rpm idle, _prompt_omph_,
>> about 100 kts (185km/h) rotation speed, (I caught it,
>> gut told me _stomp_ the brake, as it started feeling
>> like aquaplaning on dry asphalt,) and about 25 bikers
>> tickets, (at 60 km/h I lifted my foot off, and let the
>> green street light drag racing bikers catch up... and
>> get caught... ;-) ...and a snapped drive shaft. :-( )
>>
>>
>> > So --
>> >
>> > Should I run this on good charcoal only to avoid all the tar problems?
>Or
>> > make a copy of Arnt's gasifier in micro size and hope it does produce
>tar
>>
>> ..after deciding and tweaking some, you may want to resize
>> the gasifier's throat and nozzles a few times.
>> A piece of 3-5' tall 12" dia 1" wall steel pipe should do
>> fine for my gasifier proper shell, if you want to sneeze it.
>> For preliminary sizing of the internal trim, chk Gengas or
>> with me.  How much power etc., can/do/may/will you sell?
>>
>> ..when do you build this?  ;-)
>>
>> > free gas from 20% whole biomass? All that gas cleaning -- and
>maintenance
>> > of gas cleaners -- would so love to avoid it.
>>
>> ..I drew the hot gas thru a couple of barrels with about 10" of water
>> in each.  Simply cool and filter the water, draining and adding more
>> as needed.  Hot gas 2" piping enters each barrell tangentially, at
>> the bottom of the side wall, "spinning" the bobbling water, and is
>> drawn out of the barrel at the top center.  I used a cyclone inside
>> the final bath exit.  An radiator the same size as the engine's
>> radiator, and a water pump, and a water filter, valves, and a
>> few transplarent hoses to show off color, "spin" rpm, pressures, temps,
>> etc.
>> A turbocharger can be also used to collect and condense water.
>> Cat skin.
>>
>> > The advantage to charcoal is three birds with one stone. Moisture
>> > conditioning, fuel size conditioning and less tars.
>> >
>> > Have on file the plans for that "Big-Top" -- great charcoal maker.
>>
>> ..url?  (as in "Did I miss this?")
>>
>> > And if I save the gas from that device during charcoal production --
the
>> > volatiles -- can cook with it.
>> >
>> > The point being -- when going small -- easier to convert a motor laying
>on
>> > the ground than build a refrigerent cycle uniflow engine and boiler.
>>
>> .. ;-)
>>
>> > Peter in Belize
>>
>>
>> --
>> ..med vennlig hilsen = with Kind Regards from Arnt... ;-)
>>
>>   Scenarios always come in sets of three:
>>   best case, worst case, and just in case.
>>
>>
>> -
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>>
>> Gasification List Moderator:
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>> www.webpan.com/BEF
>>
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>> -
>> Other Gasification Events and Information:
>> http://www.fsec.ucf.edu/bioam/
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>>
>
>
>-
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>
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>www.webpan.com/BEF
>
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>-
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>
>
>-
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>
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>www.webpan.com/BEF
>
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>-
>Other Gasification Events and Information:
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>
>


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http://solstice.crest.org/renewables/biomass-info/