GAS-L: Checking out Catalytic burners

[Peter Singfield <snkm@btl.net>]

Peter singfield -- reporting in from Belize -- Central America.


"Alternate methods of tar control"


All Gasifiers should find interest in this subject -- here is a "taste" of
a technology that has been greatly advanced in the past few years.

I a continuing a quick study of this field. But to date -- looks like an
easy and inexpensive experiment to pass hot product gas through one of
these devices to "reform" tars -- solving one of the problems with product
gas powering an IC engine.

To quote from below:

Q: How does this affect the operation of the wood stove or furnace?
A: It affects the operation of the stove or furnace in three ways.

It increases the overall efficiency of the burning unit by 10 percent.

It reduces creosote production 20 to 90 percent.

It decreases air pollution up to 75 percent.
***************


From:

http://muextension.missouri.edu/xplor/agguides/agengin/g01733.htm

Agricultural publication G1733 — Reviewed October 1, 1993
Catalytic Combustors for Wood Burning Stoves and Furnaces
James Pastoret
School of Natural Resources, University of Missouri-Columbia
----------------------------------------------------------------------------
----
 
Q: What is a catalytic combustor?
A: It is a ceramic honeycombed device coated with a noble metal, usually
palladium. There are various sizes and shapes, but the most common
combustor is shaped like a wheel, 5-3/4 inches in diameter and 2 inches thick.

Q: What does the catalytic combustor do?
A: It causes smoke to be burned and does not allow it to go up the stack
unused.

Q: How does the catalytic combustor work?
A: Gases given off by the wood will burn if the fire is 1,000 degrees F or
higher. However, if the fire is turned down and the gases inside the
firebox are less than 1,000 degrees F, the gases will not burn. When the
gases pass through the catalytic combustor, the noble metal acts as a
catalyst and causes the gases to burn at temperatures as low as 500 degrees F.

Q: How does this affect the operation of the wood stove or furnace?
A: It affects the operation of the stove or furnace in three ways.

It increases the overall efficiency of the burning unit by 10 percent.

It reduces creosote production 20 to 90 percent.

It decreases air pollution up to 75 percent.

Q: Are catalytic combustors expensive?
A: All approved stoves are reasonably similar in price. The approved stoves
with combustors may be slightly higher.

Q: What are the limits or shortcomings of catalytic combustors?
A: There are a number of limits.

The combustors have to be replaced periodically. If they are used properly
they will last 10,000 to 12,000 operating hours.

The combustors can be contaminated (poisoned) by burning foreign materials.
This contamination reduces their operating capabilities.

Q: What can you burn, and what can't you burn?
A: When you are using the catalytic combustor, you should burn only natural
wood. Among items you should not burn are:

trash,

coal,

paper logs,

treated wood,

painted wood, and

lighter fluid.

Q: Can I buy a catalytic combustor to put in the stove I own now?
A: A number of so-called add-on combustors used to be available. This
market has practically disappeared although a few may still be available.

Q: Do all manufacturers of wood stoves and furnaces incorporate catalytic
combustors into their products?
A: No, not all approved stoves have combustors. However, at this writing
(October, 1989), it is reported to be greater than 50 percent.

Figure 1. A cut-away sketch of a wood stove with a catalytic combustor.


Q: How does a stove with a built-in catalytic combustor differ from a
conventional wood stove?
A: Figure 1 shows a cutaway sketch of a wood stove with a catalytic
combustor. The upper box (1) is the heat exchange chamber. The lower large
box is the fire box. The circular honey combed disk (2) mounted in the
baffle plate is the catalytic combustor. Hot gases and smoke from the wood
fire are forced through the catalytic combustor, at which time the
combustible gases are ignited by the combustor. Other parts of the stove
are the bypass damper (3), flame guard (4), and safety bypass opening (5).



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