Prolonging catalyst lifespan

kennyp2339 said:

Wow all you engineers here, what transit system do you work for? I always wondered what the engineer was thinking when he / she was looking out the front window of the train, now I know.. woodstoves

Click to expand...

Different engineer, I deisgn and upgrade production machines. Although, always thought driving train might be interesting, especially when they've got the snowplow on!

I'm a mechanical engineer but as a kid I wanted to be an engineer that drove steam trains.

BKVP said:

It's referred to as masking and deposits on top of the precious metals decreases exposure to gases in wood combustion.

Click to expand...

Are you telling a thread full of geeks that they just need to find the right solvent and they will never need a new cat again?

We already know it's not boiling vinegar, people. Let's not have any toxic clouds enveloping living spaces. Aaaaand go!

How long does a cat last usually and how much are they to replace?

Jazzberry said:

How long does a cat last usually and how much are they to replace?

Click to expand...

Around 10.000 hours. To have a new cat delivered to my place, around 300 dollars, gasket included.

How long do they last? The fact is all wood stoves decrease in their ability to burn as clean as new after many years of use. That is why most elements of clean burning design are replaceable. Catalysts, baffle plates, tubes, ceramic blankets, refractory panels, gaskets etc. It's up to the user to maintain their stove over time. This forum is great in helping wood stove users realizing that need.

Catalytic elements usually decrease in their conversion ability over a ten year period...or longer. The 10,000 hours is provided by the leading supplier based upon their OVERALL experience.

Manufacturers ask for warranted catalyst to be returned because the OEM reclaims the precious metals. (Remember a few years ago, there were less than ideal dudes cutting them out of exhaust systems of vehicles while the owners slept)

So while a catalyst may last 10 years it is not as clean burning after that long. OMNI did a study, overseen by EPA, that showed in a few different models, the stove burned 1 gr/hr dirtier than new. That was based on a minimum of 3 cords per year for 9.5 years.

Are all catalytic wood stoves equal in their designs, definitely not. However the OEM supplier has recognized at least one manufacturer design and offered a 10 year warranty against failure. Not diminished ability, but failure (thermal shock/destruction).

There are users of catalytic wood stoves that realize they change overtime and elect to purchase a new combustor for continued optimization in performance. These are the ladies and gents here....engineers...stove needs (not geeks) that replace their motor oil every 3,500 miles too!

Also, there are users that burn many more days a year (Highbeam) and their experiences are noteworthy but not typical. Then guys like Ashful have two stoves and heat large amounts of space. Again, noteworthy but not typical. He also has massive wood accumulation but that's another story.

There are two OEM suppliers in the USA that serve the stove industry. Applied Ceramics and Clariant. There is only one OEM that make the ceramic substrates and sells them to others, including OEM's and that is Applied Ceramics. Our company purchases from both OEM suppliers.

Firecatcombustors.com is owned by Applied Ceramics and Clariant, a German owned company, does not sell direct to consumer. I have been to their Headquarters in Munich...but that also is another story.

Both of these OEM suppliers make great products. Not all stove manufacturers use these two companies. Some purchase combustors off-shore.

Price varies upon where you buy it, how many parties are involved in the shipping and reselling, model of stove etc. You can look at the firecat website to get a good ideal of cost.

Lastly, all those cat stoves in the 1980's that failed miserably, the cat supplier was Applied. The same company, same product as used successfully today by some stove manufacturers. Just goes to show it was inferior stove design that led to all those issues, not the cat.

Ashful said:

I would be willing to bet a good number of our members are engineers. I would be willing to bet even more that those particular members favor BK, it is the true burning-geek’s stove.

Click to expand...

When we were young, I and my three best buddies ended up at the same university ( don't ask when). I was the only one studying Natural Sciences but the rest were studying Engineering. They became software, mechanical, and electrical engineer. They all are very successful engineers now and I ended up at academia. We are still best friends BUT among the four, I'm the only one owning a stove (yep, a BK)! To make them jealous, I am sharing my stove and small wood stock pics with them
PS: To be fair, before I went full throttle into the academic career, I briefly considered Food Engineering master program and even got accepted to the program. But still went ahead with a non-engineering discipline.

I would like to add the following graphic. It shows the effect of excessive heat to the wash coat, which carries the precious metals and creates tremendous surface area. As the catalyst is exposed to temps greater than 1600F, the wash coat flattens out, loses surface area and no longer has the appearance of an English muffin. That makes it less effective. Prolonged or repeated excessive temps will then allow the wash coat to peel away from the substrate, essentially eliminating the ability for the combustor to convert gases to energy and therefore not burn cleanly. This is what happens to cats in stoves that do do protect against excessive drafting or over firing.

chemie said:

When we were young, I and my three best buddies ended up at the same university ( don't ask when). I was the only one studying Natural Sciences but the rest were studying Engineering. They became software, mechanical, and electrical engineer. They all are very successful engineers now and I ended up at academia. We are still best friends BUT among the four, I'm the only one owning a stove (yep, a BK)! To make them jealous, I am sharing my stove and small wood stock pics with them
PS: To be fair, before I went full throttle into the academic career, I briefly considered Food Engineering master program and even got accepted to the program. But still went ahead with a non-engineering discipline.

Click to expand...

At every single event where the manufacturers gather for meetings, the number one topic over drinks is where to find some good combustion engineers. The last meeting I attended, two weeks ago, two very well established company representatives asked me if I knew of anyone looking to make a change.

A very large number of stove designers have worked for multiple companies. We need new blood in this industry so if you have sons, daughters or grand kids going to college to study engineering, tell them they can write their own deal if they have an education in combustion engineering!! Most get paid extremely well and they won't have to look very hard or far to land a job!

BKVP said:

At every single event where the manufacturers gather for meetings, the number one topic over drinks is where to find some good combustion engineers. The last meeting I attended, two weeks ago, two very well established company representatives asked me if I knew of anyone looking to make a change.

A very large number of stove designers have worked for multiple companies. We need new blood in this industry so if you have sons, daughters or grand kids going to college to study engineering, tell them they can write their own deal if they have an education in combustion engineering!! Most get paid extremely well and they won't have to look very hard or far to land a job!

Click to expand...

Good advice! My son, though just sixth grader, has an engineering mindset that he mostly likely inherited from his mom.

BKVP said:

At every single event where the manufacturers gather for meetings, the number one topic over drinks is where to find some good combustion engineers. The last meeting I attended, two weeks ago, two very well established company representatives asked me if I knew of anyone looking to make a change.

A very large number of stove designers have worked for multiple companies. We need new blood in this industry so if you have sons, daughters or grand kids going to college to study engineering, tell them they can write their own deal if they have an education in combustion engineering!! Most get paid extremely well and they won't have to look very hard or far to land a job!

Click to expand...

First time I've ever heard of a combustion engineer. I'm sure its heavy in chemistry (obviously). There was a combustion course I could have taken but opted not to... Now I'm getting qualified in machinery lubrication...

Lol, it's really not that anticlimactic.

BKVP said:

As the catalyst is exposed to temps greater than 1600F, the wash coat flattens out, loses surface area

Click to expand...

Talking about BK, that if everything is working correctly, the tstat prevents overfiring the stove, is it ok to run it on high for a long period of time if needed?

Combustion engineering isn’t one of the big three but a sub category or specialty. An engineering degree proves that you can learn and apply math so most of the time, your area of specialty in school isn’t as important as you would like to think.

Now if experienced combustion engineers are needed then that specific experience on top of education is very valuable.

i talk to the customers so the engineers don't have to

lsucet said:

Talking about BK, that if everything is working correctly, the tstat prevents overfiring the stove, is it ok to run it on high for a long period of time if needed?

Click to expand...

Yes

Dobish said:

i talk to the customers so the engineers don't have to

Click to expand...

"I have people skills"

BKVP said:

I would like to add the following graphic. It shows the effect of excessive heat to the wash coat, which carries the precious metals and creates tremendous surface area. As the catalyst is exposed to temps greater than 1600F, the wash coat flattens out, loses surface area and no longer has the appearance of an English muffin. That makes it less effective. Prolonged or repeated excessive temps will then allow the wash coat to peel away from the substrate, essentially eliminating the ability for the combustor to convert gases to energy and therefore not burn cleanly. This is what happens to cats in stoves that do do protect against excessive drafting or over firing.View attachment 232049

Click to expand...

While we have you talking cat geekery, I have a substrate question.

We are told that steel cats can start doing their thing ~100°F lower than ceramic cats. My experience with steel this year seems to confirm that.

Why would that be? Obviously the steel is far more thermally conductive than the ceramic, but given the hot air blowing through the cells and the fact that the action happens right on the surface of each cell... why does the substrate material affect the light off temperature at all?

Same question put a different way: If I blow 450° smoky air through a steel cat and a ceramic cat, the surfaces of both come up above 400° and the wood gas and other hydrocarbons are making contact with the catalyst. Why would there be reactions taking place with a steel substrate but not a ceramic one?

jetsam said:

While we have you talking cat geekery, I have a substrate question.

We are told that steel cats can start doing their thing ~100°F lower than ceramic cats. My experience with steel this year seems to confirm that.

Why would that be? Obviously the steel is far more thermally conductive than the ceramic, but given the hot air blowing through the cells and the fact that the action happens right on the surface of each cell... why does the substrate material affect the light off temperature at all?

Same question put a different way: If I blow 450° smoky air through a steel cat and a ceramic cat, the surfaces of both come up above 400° and the wood gas and other hydrocarbons are making contact with the catalyst. Why would there be reactions taking place with a steel substrate but not a ceramic one?

Click to expand...

So much more surface area, so many more cells, so much more exposed catalyst, so much lower velocity across each cell for longer residence time. So very thin walls so little thermal mass so quick to heat up without that fat ceramic stealing heat.

Here's the steelcat I installed into the princess. It worked fine but I don't feel like ceramic performs any worse.

jetsam said:

While we have you talking cat geekery, I have a substrate question.

We are told that steel cats can start doing their thing ~100°F lower than ceramic cats. My experience with steel this year seems to confirm that.

Why would that be? Obviously the steel is far more thermally conductive than the ceramic, but given the hot air blowing through the cells and the fact that the action happens right on the surface of each cell... why does the substrate material affect the light off temperature at all?

Same question put a different way: If I blow 450° smoky air through a steel cat and a ceramic cat, the surfaces of both come up above 400° and the wood gas and other hydrocarbons are making contact with the catalyst. Why would there be reactions taking place with a steel substrate but not a ceramic one?

Click to expand...

Jetsam,

Simple answer. The stainless combustors have more surface area. Look at the cell structure and you'll see more cells per square inch. Second, the wall thickness is much thinner in the stainless versus the ceramic. So keep in mind there is time lag time in the cat thermometers. So the stainless certainly light off much quicker, about 10-15 minutes, but they also cool off quicker at the tail end of the burn.

BKVP said:

Jetsam,

Simple answer. The stainless combustors have more surface area. Look at the cell structure and you'll see more cells per square inch. Second, the wall thickness is much thinner in the stainless versus the ceramic. So keep in mind there is time lag time in the cat thermometers. So the stainless certainly light off much quicker, about 10-15 minutes, but they also cool off quicker at the tail end of the burn.

Click to expand...

I'm not debating that the surface of the steel warms up and cools down faster (lower mass, much higher thermal conductivity), but why would steel and ceramic begin operation at different temperatures?

A quote regarding steelcats from Condar's catayst website:




If I baked one of each cat at 450° in an electric oven for six hours, why would the steel one be ready to eat smoke while the ceramic one isn't? I assume they have the same catalyst(s) on the surface of the substrate.

If you greatly raise or lower the surface area of either one by changing the cell size, the question of minimum operating temperature doesn't vary.

(Also, now I want a stove that would hold one of each side by side with perfectly balanced air flow, and temperature and flow rate sensors before and after the cats. This in turn leads me to worry that you are trying to bait me into becoming a combustion engineer just to fill your vacancies at work.... )

jetsam said:

I'm not debating that the surface of the steel warms up and cools down faster (lower mass, much higher thermal conductivity), but why would steel and ceramic begin operation at different temperatures?

A quote regarding steelcats from Condar's catayst website:

View attachment 232081


If I baked one of each cat at 450° in an electric oven for six hours, why would the steel one be ready to eat smoke while the ceramic one isn't? I assume they have the same catalyst(s) on the surface of the substrate.

If you greatly raise or lower the surface area of either one by changing the cell size, the question of minimum operating temperature doesn't vary.

(Also, now I want a stove that would hold one of each side by side with perfectly balanced air flow, and temperature and flow rate sensors before and after the cats. This in turn leads me to worry that you are trying to bait me into becoming a combustion engineer just to fill your vacancies at work.... )

Click to expand...

So I spoke to the ONLY guy with a degree in catalytic chemistry in the stove/combustor industry. He states, "When you look at the light off curve, both stainless and ceramic have the same light off temp. Only the stainless gets their sooner." I would believe this man's word over another company claim that is a reseller.

The way i see it is like steel vs stone stoves. steel heats up faster than stone. The same way cools off faster than stone. i think i got confused here.

BKVP said:

So I spoke to the ONLY guy with a degree in catalytic chemistry in the stove/combustor industry. He states, "When you look at the light off curve, both stainless and ceramic have the same light off temp. Only the stainless gets their sooner." I would believe this man's word over another company claim that is a reseller.

Click to expand...

Also, that makes sense and Condar's claim doesn't. Thank you.

So, why is it recommended to wait until the combustor reaches active temperature before engaging it? Is it just to avoid thermal shock from sending hot gases into a cold combustor? I.e is "active" just a proxy for "hot enough to not thermally shock the cat?" If it's OK to send cold combustion products across the cat at the end of the burn, why not at the start of the burn?

ben94122 said:

So, why is it recommended to wait until the combustor reaches active temperature before engaging it? Is it just to avoid thermal shock from sending hot gases into a cold combustor? I.e is "active" just a proxy for "hot enough to not thermally shock the cat?" If it's OK to send cold combustion products across the cat at the end of the burn, why not at the start of the burn?

Click to expand...

Great question.. first stage of combustion...boiling water out of fuel..no measurable moisture at end of burn. We need "catalyst conversion" to begin before we shove 100% of gases thru the combustor. Look at burn charts and there is a direct correlation to moisture influence early in burn cycle and combustor temps.