Just wondering if these Catalytic stoves have secondary air injected to help the catalyst
I have done a little research on this with no luck.
I have done a little research on this with no luck.
Does the blaze king princess catalytic or similar catalytic stoves have a secondary air pipe?
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No, not to my knowledge. Older cat stoves used to have this (i.e. my previous DutchWest), and maybe other modern cat stoves, but BKs have one inlet that is conveniently controlled with a thermostat.
lsucet
Minister of Fire
BK has a single intake. All the air that is needed at different rates come in through a single intake with a mechanico/automatic thermostat inline. Most thermostat flapper has a set hole allowing always some air going through including when the flapper is closed.
Depending on your setup, draft, outside temperature etc, can be enough air to run the stove without stall the cat. Not everyone can run the hole ( a Highbeam saying ) without stall the cat.
Depending on your setup, draft, outside temperature etc, can be enough air to run the stove without stall the cat. Not everyone can run the hole ( a Highbeam saying ) without stall the cat.
Wonder why they would inject catalyst air? I don't see the point, Maybe its just strictly because it helps them meet the EPA standards?
lsucet
Minister of Fire
Progress Hybrid Wood Stove
Unique Hybrid Design The Progress is a HYBRID because it uses both a catalytic combustor and a secondary combustion system. Until the Progress was introduced in 2011, EPA certified wood stoves used one or the other. The Progress gives you the best of both systems - combined. A catalytic combustor b
www.woodstove.com
So basically its a hybrid with both cat and secondary, I would think a Catalytic stove would work better without Secondary air?
Other old cat designs added catalyst air too. Like even the really old designs. Maybe the weird one is BK!
Hmm wouldn't that mean the BK would stall a lot at low burn rate? I have no idea just tryin to learn
lsucet
Minister of Fire
Progress Hybrid Wood Stove
Unique Hybrid Design The Progress is a HYBRID because it uses both a catalytic combustor and a secondary combustion system. Until the Progress was introduced in 2011, EPA certified wood stoves used one or the other. The Progress gives you the best of both systems - combined. A catalytic combustor b
So basically its a hybrid with both cat and secondary, I would think a Catalytic stove would work better without Secondary air?
That’s a hybrid stove. Woodstock didn’t start hybrids until recently. Before that they made some very good cat stoves. Still do.
The hybrids, in theory, allow you to run a stove hot without as much emissions as a cat only stove. A straight cat stove at high output isn’t quite as clean since the smoke rushes through the cat so fast.
Catalyst air is not the same as secondary air in a hybrid. I suppose you could say that the Woodstock PH offers primary combustion, secondary combustion from the air feed in the firebox roof, and then tertiary combustion in the catalyst supported by that catalyst air supply.
Lots of new things being done to keep things clean, efficient, and still provide user control of burn rate.
lsucet
Minister of Fire
The thermostat opens as the stove gets colder to provide more air if things cool off too much.
I used to have a photo of the one in my princess. Not every BK has a hole in the flapper plate. Some models have a hole elsewhere in the intake manifold. The hole is only pinky sized. Smaller than a dime.
I've wondered about this, I also wonder if its because on high the firebox gets hot enough that the air is being burnt there, leaving little remaining oxygen to properly oxidize the smoke and particulates at the catalyst. Maybe a cat air injection that activates only on high output settings would clean this up?
I guess this theory would be pretty simple to prove with the right equipment, an oxygen sensor above the cat could fairly easily determine remaining oxygen levels, and if a low remaining O2 at high output is the cause of higher CO and particulate emissions.
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Cat stove on high: not necessarily, because it depends on the impedance of the air inlet and the capability to use the oxygen in the firebox (which depends on the airflow turbulence in the firebox and the amount of exposed and hot wood surface). It could very well be that a stove can suck in more air than it can use in primary combustion - in fact that appears to always be the case as the cat IS working (using oxygen to further oxidize the gases).
Just reading thru this thread and yes, that was my thought. I suspect the secondary air feed was/is for times during startup when there is a need for additional air to burn up a large bloom of wood gases. This is introduced via the secondary feed. IIRC they do this on some car exhausts too.
Maybe that's the case. But generally in the case of wood combustion excess oxygen is always required to achieve complete combustion. At EPA 2020 standards it only takes a small amount off wood gases to either not be burnt or only partially burnt to exceed the max limits.
It's similar to diesel engines, in theory the stoichiometric ratio is 14.5 parts diesel to 1 part air by mass. In practicality most engines begin to produce significant amounts of soot when going richer than 18:1. Even natural gas combustion which is extremely clean runs excess air to prevent soot.
I'm not saying there's already excess air in a cat stove like a blaze king, but I'm strongly inclined to believe they would burn cleaner on high output with more excess air being introduced just ahead of the cat, particularly if this air was pre-heated. Having a look at the emissions testing for the BK Princess further increases my belief in this, on high output CO increases greatly, CO is easy to oxidize in a catalyst given high temps (which are certainly there on high) and enough oxygen (probably not enough).
BKVP
Minister of Fire
In 1982 Blaze King introduced the PE1000. A catalytic wood stove that also had 4 secondary air tubes. This would be the forerunner to today's hybrid wood stoves. In fact, one applicant (manufacturer) for hybrid stove technology patent, served another manufacturer with an intent to litigate because they too had a hybrid wood stove. The manufacturer being threatened with action called me to discuss the topic. I provided his attorneys with documents showing prior existence. The bigger manufacturer withdrew their claim against the nice guy. So these concepts are not new.
We learned a great deal from this period. First, keep in mind the industry was just giving birth to catalytic wood stoves. The supplier at the time was Corning and they supplied mullite and cordierite substrates. The introduction of room air to the combustor was fraught with one major issue, thermal shock! Some when the substrate was really nice and hot, room air of 78 or so was piped directly to the combustor making it a less than perfect design.
The next step was to try supplying heated air to the combustor. Some of these have come to market in the past couple of years. Anecdotally, I suggest the jury has yet to respond to longevity of such designs. The use of metal substrates may give the impression that all is well, however, you must keep in mind the wash coat carrying the precious metals can also suffer from thermal shock. So, just because it doesn't crumble, doesn't mean all is well.
We left this design because it added to the cost, did not increase efficiency and did not reduce particulates. We still make some of the cleanest burning, most efficient units, without adding complexity.
There is a single air source for all our current stoves and inserts. The "hole" that is discussed can be located in different locations and may not be easy to locate. This is intentional. We are required to make our stoves as tamper proof as possible.
We learned a great deal from this period. First, keep in mind the industry was just giving birth to catalytic wood stoves. The supplier at the time was Corning and they supplied mullite and cordierite substrates. The introduction of room air to the combustor was fraught with one major issue, thermal shock! Some when the substrate was really nice and hot, room air of 78 or so was piped directly to the combustor making it a less than perfect design.
The next step was to try supplying heated air to the combustor. Some of these have come to market in the past couple of years. Anecdotally, I suggest the jury has yet to respond to longevity of such designs. The use of metal substrates may give the impression that all is well, however, you must keep in mind the wash coat carrying the precious metals can also suffer from thermal shock. So, just because it doesn't crumble, doesn't mean all is well.
We left this design because it added to the cost, did not increase efficiency and did not reduce particulates. We still make some of the cleanest burning, most efficient units, without adding complexity.
There is a single air source for all our current stoves and inserts. The "hole" that is discussed can be located in different locations and may not be easy to locate. This is intentional. We are required to make our stoves as tamper proof as possible.
