Dear David
You bring out lots of good points...
----- Original Message -----
From: "David Coote" <[email protected]>
To: <[email protected]>
Sent: Thursday, April 12, 2012 9:39 PM
Subject: [Gasification] Why would you want to make heating grade woodgas?
There's a heap of efficient wood burners (fuelwood, chip or pellet) on the
market that can convert wood to thermal energy at over 90% thermal
efficiency LHV. Some of the new condensing systems are even claiming over
100% on LHV.
# There are several concepts here... it is important to distinguish
between "Combustion Completeness", "Combustion Efficiency", and "Heating
System Efficiency."
# It is relatively easy to get very high, or complete "Combustion
Completeness" with wood gas... this is "completeness of burning of the fuel
gas."
# "Combustion Efficiency", in addition to "Completeness of Combustion", also
implies a minimum of excess air. Thus one could have 100% "Completeness of
Combustion,", but a low "Combustion Efficiency" if there was a large amount
of excess air.
# "Heating System Efficiency" is very dependant on the amount of "heat
recovery surface available" in teh stove or furnace system. For example, one
could have 100% Completeness of Combustion, 90% Combustion Efficiency, with
limited excess air, but only say 40% 40% "Furnace Efficiency", because there
was insufficient heat transfer area to recover the heat for space or process
heating.
# So... a separate gasification system can give much better control over the
fuel burning rate, and the completeness of combustion, but the products of
combustion must be sent to a "heat recovery system" of some sort, in order
to get a good "overall system efficiency.
So why would you want to go through a distinct gasification process to
produce gas for subsequent combustion in a burner?
# For one thing, a gasifier system for "Heating Grade Gas", can handle a
wide range of fuel sizes and shapes, with relatively simple feeding systems.
A Pellet Stove, for example, requires uniform, factory made, expensive wood
pellets, while a gasifier system can handle coarsely chunked wood or free
wood chips.
If you're methanating
the gas like the system developed at Gussing to bring the wood gas up to
the standard suitable for addition to the natural gas grid that makes
sense from a technical perspective.
# I don't know the Gussing Process, but producing a wood gas with a heating
value in teh same range as natural gas is well beyond what is considered to
be "Gasification" on this list.
But if you were just wanting to turn
the woodgas into space heat?
# The simplest way, of course, is to burn the wood directly, if that is
practical. Gasification could be advantageous in the following
circumstances:
1: Where the fuel size and quality is very variable.
2: Where it is desired to keep teh fuel mess and dirt in one location, with
teh wood gas being piped to a stove/boiler/furnace system in another
location.
3: Where it is desirable to have several burner systems in different
locations, supplied from a single gasification unit.
4: A Gasifier system can allow greater control over heat release into the
furnace/stove/boiler.
5: A gasifier could offer fuel handling and feeding advantages.
6: Ash can be basically confined to the gasifier, with little or no ash
passing through the burners to the stove/furnace/boiler system.
# So... there may be "Site Specific Advantages" that justify using a
gasifier, rather than burning the wood fuel directly.
Best wishes,
Kevin
Cheers
David
_______________________________________________
Gasification mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org
for more Gasifiers, News and Information see our web site:
http://gasifiers.bioenergylists.org/
_______________________________________________
Gasification mailing list
to Send a Message to the list, use the email address
[email protected]
to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/gasification_lists.bioenergylists.org
for more Gasifiers, News and Information see our web site:
http://gasifiers.bioenergylists.org/
