composition of firepot deposits?

[stecy]

Both the Enviro Maxx at home and the Harman PB105 at the in-laws accumulate hard black deposits in the firepot that have to be scraped off weekly to maintain a good flame. These deposits are HARD - especially on the Maxx, where sometimes I have had to resort to a cold chisel & hammer to remove them. For a long time I assumed that this material was carbon, but recently I questioned that, and began to suspect that it must be minerals. If it was carbon, why wouldn't it just burn up?

Does anybody know the scientific facts? Is there anything to the idea that different pellets might have an effect on this, or is that just folklore? Have been burning hardwood pellets: Northern or New England. Some say softwood pellets produce softer ash, but does that relate to this type of deposit in any way?

TIA

Steve

 

[SmokeyTheBear]

There are several things that are in the deposits left in the fire pot, some of those deposits that stick to the pot are chlorides (salts), if left on and get a bit of moisture will slowly corrode the metal, the problems they can cause also includes restricting the air flow through the pot leading to a bad burn.

 

[schoondog]

I sometimes question the same thing. I have heard that there are " additives" in wood pellets to improve the compactibility or the resistance to come apart. After burning the grass pellets I had no "carbon" in my burnppot and I do not believe any "additives" were in the pellet.

Schoondog

 

[BDPVT]

Hard black firepot deposits are best descibed as carbon scale caused by incomplete combustion. This occurs when there isn't enough oxygen to allow the fuel ( hydrocarbon) to react completely with the oxygen to produce carbon dioxide and water, and also when the combustion is quenched by a heat sink such as a solid surface or flame trap. When a hydrocarbon burns in air, the reaction will yield carbon dioxide, water, carbon monoxide, pure carbon (soot or ash) and various other compounds such as nitrogen oxides.

 

[SmokeyTheBear]

There is also potash, potassium and sodium carbonates, and sodium sulfate. These can adhere to the pot under proper conditions.

But that said there is still carbon in the ash and some of it will get "glued" this happens as BDVT has noted when combustion is quenched (stopped for the material that was burning).

Ain't combustion just grand, so many compounds so much to scrape and clean out.

 

[Dr_Drum]

I know you didn't ask about cleaning specifically, but I have been using Easy-Off oven cleaner once every few weeks. Macman suggested it in post (thanks Mac). After a few hours it just lifts the scale off the steel. I don't really get a thick layer of build-up anyway so it works very well and is easier than scraping. May make things easier for you?
Mike -