Tuesday, August 30, 2016

How can you tell if the combustor is working?


Note: Some stoves are equipped with a combustor view port, it should be noted that the combustor usually glows during the first 20 to 35% of the burn cycle when the catalyst is receiving the most smoke and burning at a high temperature.  The combustor temperature can reach 1000o f. and produce a glow.  However, the combustor does not have to glow to be working.  As less smoke is present to burn, the combustor temperature drops and the glow will cease.  Therefore, we suggest this not be a method of determining whether or not the combustor is working.
 

-The best method is the use of thermo couplings and following the manufacturer’s instructions.
This method will read the inlet and exhaust temperatures of the combustor.
 
-A more simple method is to visually observe the exhaust coming out of the chimney.  When the by-pass is in the closed position and the catalytic combustor is in good operating condition, there should be no dark smoke coming out of the chimney.

-If the catalytic combustor is not working properly, the stove’s operator will notice an increase in fuel usage.

-The stove’s operator will also notice an increase build-up of creosote in the system.

Wednesday, August 24, 2016

What are some of the necessary requirements for building a catalytic wood burning stove?


 

  a. Preheated secondary air supply.

        Since most of the intake oxygen is used up in the firebox burning, preheated secondary air must be supplied to the catalytic combustor.  This air is mixed with the wood gases from the firebox and distributed across the intake face of the combustor.  Air to fuel ratio is important.  Too much air will cool the combustor and not allow it to work properly. To little air will starve the combustor of necessary oxygen needed for its operation.
 

  b. By-pass system. (By-pass damper)

      The by-pass system is used in an open position when starting the initial fire in the stove.

      This allows the smoke to by-pass the combustor while the combustor is heating up and temperatures throughout the stove are stabilizing.  This requires anywhere from 20 to 30 minutes of burning with the by-pass in an open position.  After this period of time the combustor will light-off and the by-pass should be closed.
 
  c. Flame shield.

      The flame shield is designed to protect the combustor from direct flame impingement.  It is located at the top of the firebox.  Most flame shields are removable so that the combustor can be serviced or replaced if necessary.  It is usually held in place with four brass nuts.
 

  d. A Properly sized catalytic combustor.

      This is determined by the manufacturer and the size stove being built. The flow rate going through the stove will have a lot to do in determining the correct combustor size and cell density to be use.  Also the amount of room available where the combustor is to be positioned will help determine what combustor size to use.

      Cell density determines the amount of open frontal area needed to control the flow rate and also the amount of surface area required to burn the gases received by the combustor.

      Height of the combustor (distance through the cells) also plays a role in the residence time the gases have to burn within the combustor.  3” height combustors will create more residence time for the gases to burn, providing the stove has the available area for mounting the combustor.

      Applied Ceramics carries a wide range of combustor in various shapes, sizes and cell densities to select from. 
 

  e. Stove must be airtight.

      In the United States all catalytic stoves are required by law to be airtight.  This allows the consumer control over the flames in the stove’s firebox. 
 

  f. Firebox must have primary adjustable air intakes.

     The firebox air controls are used to control the amount air intake to the firebox.  These controls can be adjusted by the stove’s operator to reduce or increase the amount of oxygen being supplied to the fire.  Reducing the air intakes will lower the flames and create a longer burn rate. Reducing will also keep flames from wrapping the flame shield and burning directly into the combustor when the by-pass is in the closed position.  

Friday, August 19, 2016

Catalytic combustor design.

What makes up a catalytic combustor design?

Catalytic combustors are manufactured to a stove manufacturer's specifications. 
Each combustor requires a certain cell density to allow the stove a proper flow rate of the gases.
They are designed to allow proper residence time for the smoke and gases to burn before exiting the stove.
They are also sized based on the firebox volume.
All catalytic combustors must be EPA approved to assure the consumer they not only work, but will meet EPA emission regulations.

Tuesday, August 16, 2016

How a catalytic combustor works.

Normally, smoke will burn, at a temperature of 1000 F. or higher. Burning a stove this hot would require continuous intense fire and would require a higher wood consumption.
The answer to eliminate this is the catalytic combustor.

Wood smoke gases coming in contact with the catalyst, causes chemical changes to take place. This will then allow the smoke to ignite at temperatures around 500 F. or (260 C.)
 


This temperature is easily achieved in the firebox of a wood burning stove.

As the wood gases ignite and burn within the catalytic combustor, clean by-products of water vapor (H2O) and carbon dioxide (CO2) are emitted.   
 

Friday, August 12, 2016

Advantages of using a catalytic wood burning appliance.


What are some advantages of using a catalytic wood burning appliance?

 


  1. Reduces air pollution by up to 90%

  2. Generates up to 50% more useful heat from each log.

  3. Longer burns.

  4. Saves up to 1/3 on fuel cost.

  5. Reduces Creosote build up. (Up to 90% reduction)

  6. 72% or better heating efficiency.

Tuesday, August 9, 2016

Check the combustor in your catalytic appliance now.

While the weather is still warm and your stove is not in use, it may be a good idea to do your maintenance before the burning season begins.  
Remember the combustor is your heat source, not the firebox temperature.
If it is necessary to replace the combustor, I strongly recommend calling the friendly sales people at Applied Ceramics Inc. 
They will give you expert advice and the best prices you can find anywhere.

The right catalytic combustor is very important to the wood burning appliance's efficiency.




Wednesday, August 3, 2016

Methods for cleaning the combustor.


Now is a good time to check your wood burning appliance.  Don't wait until the last minute.

Depending on the combustor's condition, follow one of these methods:























 
A vacuum cleaner may be used, but never use high pressured air to blow the cells free of any build-up. This can damage the cell walls.
Any cell blockage can be removed with the use of a pipe cleaner or a cotton swab.


























Should the combustor’s cells become masked with fly-ash,...use a paintbrush or soft-bristled brush and dust the combustor gently.


Never use anything abrasive to clean the combustor.


























Normally the catalytic combustor requires little or no maintenance because it generates such high temperatures, it is basically self-cleaning.

However, should the combustor become masked with soot or creosote, it is possible to burn the accumulation off by opening the bypass and building a hot fire.
Once the hot fire is created, close the bypass halfway and burn for 30 to 60 minutes with the bypass left in this position.

Never use cleaning solvents to clean it.
It would be wise to check and clean the combustor, if necessary, before each burning season and inspect the flue system for any signs of creosote build up.

A clean flue helps prevent chimney flue fires.

Friday, July 29, 2016

Why is 'flame impingement' bad for the catalyst?



Simply put...direct flame contact is death to the catalyst.

A catalyst burns the byproducts in the smoke. The gases such as CO, HC, and O2 ignite with each other in a chemical reaction in the presence of the catalyst (while passing through the honeycomb configuration).

Direct flame inhibits this reaction by changing the chemical make-up of the catalyst breaking down the substrate or ceramic.
 
 
 

Today's modern wood burning stoves are designed so that flame impingement is unlikely. However, it is not impossible. A strong fast draft can pull the flames into the catalyst. A hot fire with all the primary air controls wide open or perhaps the firebox door or ash pan door ajar are other ways the catalyst might receive flame impingement.

Tuesday, July 26, 2016

What are some reasons for poor draft?


Below are a few reasons for poor draft.

1. Top of the chimney is too low, not extending above the top of the pitched roof or surrounding trees.

2. Dirt, creosote or soot lodged in corners or along the flue walls.

3. Loose mortar or cracks in the brick-work cause draft leaks.

4. Spaces between liner tiles.

5. Dislodged bricks or tile wedged in the chimney.

6. Connecting stove pipe projects too far into the chimney.

7. Chimney clean-out door too loose.

8. Leaks around chimney connector pipe.

Friday, July 22, 2016

What would cause the combustor to become plugged?

Plugging can occur if the stove is operated improperly.

Examples:
 
Not allowing the combustor to achieve light-off (closing the bypass to soon).  Remember the rule of thumb....when starting a fire in a cold stove, leave the bypass open for 20 to 30 minutes.

Burning materials that produce large flakes or char, such as wrapping paper or cardboard, can plug enough cells to cause smoke spillage. The combustor will struggle to do its job.



 

Tuesday, July 19, 2016

Burning in a catatlytic appliance.

Burning materials, like those listed below, will gradually reduce the efficiency of the catalyst.

“Burn only seasoned dried wood”


Never burn foreign matter such as…
garbage,
painted wood,
large amounts of colored paper,
cardboard,
rubber,

pressure treated wood,
plastic,
paneling with glue,
oily products and so on.


All catalytic combustors used in EPA certified Phase II stoves have a life expectancy of at least, 10,000 burning hours, when used according to the stove's operating manual.

It could be said, that a catalytic combustor’s life is really based on a number of things....

Operating the stove properly....
(Not burning with firebox door open or perhaps closing the by-pass to soon)


Using regular
maintenance habits to both stove and combustor....
(Simple things like checking the firebox door gasket)


Burning proper fuel in the appliance....
(This means burning seasoned dried wood only- no foreign matter that could poison the combustor)

Friday, July 15, 2016

Most effective way to operate a catalytic appliance.


The most effective way of operating a catalytic appliance is by utilizing temperature monitors. Ideally, two sensing positions will give all the information needed to tell when to engage the combustor, how well the combustor is operating, when it's time to refuel and when the combustor is no longer operational.



The upstream temperature gauge will monitor combustor inlet conditions.
The second temperature gauge should be mounted on the combustor's exhaust side, about a 1/4" off the surface and centered on the unit. This will monitor the catalytic combustion process. If only one temperature sensor is used, it should be the one that reads the exhaust temperature of the catalytic combustor.
Thermocouplings and thermometers of various designs are available for this purpose
.

Tuesday, July 12, 2016

What to do if the combustor is not working properly.

Catalytic combustors don't burn out like a light bulb and they don't just stop working when the stove is operated properly. 
If you happen to experience a problem with the combustor, do the following: 

-Check your fuel supply for moisture content. Fuel should be seasoned dried wood. Rain and snow are considered moisture and will produce damp smoke and steam. Both harmful to your combustor, especially when refueling and the combustor is burning hot.

-Check the flue and chimney, making sure the stove’s exhaust system is not blocked nor has any obstructions.

-Make sure the stove is getting the proper draft.

-Check all movable stove parts to be sure they are working freely.

-Make sure the combustor has not fallen out of its holding device.

-Check the combustor for plugged cells. Follow cleaning instructions.

-Check if the combustor has been in the stove for more than six burning seasons, it might be time to replace it.

It's important to follow the manufacturer’s instructions for proper firing. Different manufacturers and stove models require different procedures.
As a rule of thumb, the catalytic combustor needs a minimum of 500 F. temperature focused on it for a period of 20 to 30 minutes to achieve light-off. This is done with the bypass in the open position.
Nothing but heat will be going to the combustor at this stage. The catalyst will receive the heat it needs in this period of time.