Wood Pellet storage (end user)

[RFDACM02]

Has anyone dealt with wood pellets being stored in bulk inside at the point of use? Not the bags stored on pallets (possible issue of their own), but large storage bins installed to feed a wood boiler.

Here's our situation: 4 story sprinklered mercantile/office building, single tenant. They properly install a wood pellet boiler in the basement, but they stick build (2x4's and OSB) a bin capable of holding 12-14 tones of pellets. This bin is about 10x12 ft and 7 ft tall (tapered at the bottom to feed an auger). I immediately have a few issues: the bin top is too close to the sprinkler heads, the sprinkler company has not been consulted to ensure their design will cover the fuel load, the room is not fully enclosed as there's a 6 ft opening to access the room from the basement mail room (I'm considering this a high hazard for separation purposes). Lastly, and this is a question for others, but I don't like fusible link fire dampers in sprinklered spaces as I doubt the link will trip as the sprinkler will typically activate first and cool the space, so this allows smoke and CO to pump out the damper/vent?

Wondering if others are dealing with these? Or have thoughts or ideas?

 

[cda]

Welcome!!!!

fire5555

moved the post to commercial fire

 

[steveray]

Someone needs to move this out of residential.....The sprinkler design certainly needs to be addressed...I don't know if should really be treated as an H, but maybe.

Moved it while I was replying...

 

[cda]

Magic of the Alnet

 

[north star]

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RFDACM02,

To clarify, ...the wood pellet storage bin is located in the basement

close to the boiler ?

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[Frank]

Wood pellets are ordinary hazard, no different than paper storage--shelves of boxed records would be more of a hazard as the pellets have less exposed surface for burning. As long as the bin walls are not obstructing the sprinklers and the clearances to the boiler are maintained it should be a nonissue--no different from the traditional coal bins next to boilers. If there is a top on the bin it would be creating a combustible concealed space and a sprinkler head would need to be dropped into the bin.

 

[cda]

Wood pellets are ordinary hazard, no different than paper storage--shelves of boxed records would be more of a hazard as the pellets have less exposed surface for burning. As long as the bin walls are not obstructing the sprinklers and the clearances to the boiler are maintained it should be a nonissue--no different from the traditional coal bins next to boilers. If there is a top on the bin it would be creating a combustible concealed space and a sprinkler head would need to be dropped into the bin.

One other of possible many problems with wood pellets::

Pellets in a closed storage environment can heat up due to microbiological and/or chemical reactions. The bulk mass act as insulation and therefore heat is usually built up deep inside the bulk. Microbiological decay requires moisture and it is therefore usually a problem occurring when the moisture content of the biomass is too high or in case of water (rain) coming in contact with the biomass. Microbial decay results in a temperature increase in the stored fuel and peak temperatures of microbial self-heating can be up to 80 °C depending on the type of microorganism [19]. Chemical degradation usually starts to have influence at about 40 °C and at temperatures above 50 °C chemical degradation reactions will exceed the biological ones [19]. Due to poor heat transfer within the bulk mass and the insulating properties of biomass, heat is accumulated inside the bulks that can result in self ignition. The main factors affecting the temperature in a pellet silo are the ambient temperature, moisture content, moisture gradients, size of the bulk and density.

 

[RFDACM02]

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RFDACM02,

To clarify, ...the wood pellet storage bin is located in the basement

close to the boiler ?

% $ % $ %

The bin is in a "separate space" from the boiler, as they built a rated wall between the boiler and the storage bin. Clearly, the sprinklers are an issue as there is a top on the bin (OSB) and it's within 6" of the heads vs. below the 18" plane. In this case the basement storage area is almost separated from the rest of the basement areas by a concrete wall, except a 6 ft opening which I'd like to see enclosed. This would put the storage bin inside a rated room with sprinklers (when they're corrected). The fear on the part of the pellet people is that the pellets can absorb water and grow 4-5 times their size, which could result in structural damage if the space is too tight? In all it says to us this "plan" was ill-conceived at best.

I have also read about cases of CO poisoning in Europe where pellets are stored? Not sure how the CO is produced vs. just a lack of oxygen, but this has been noted in 9 or so cases and apparently is spurring some Code changes.

Also, anyone else not allowing thermally operated fire dampers in sprinklered spaces? I question their ability to close before the sprinkler activates and then not close at all, thereby creating a place for "cold" smoke and CO to pump out? They've installed two of these dampers in the separation wall, I'd like to see no openings or dampers activated by smoke detection. Can only assume they needed make-up air as the reason for them.

 

[cda]

So do you have a building official that is also looking at this??

For the possible swelling,

Use what is there now, if loaded

Than require the bin size to be reduced

 

[RFDACM02]

So, many positive things were found this week. The sprinkler company found their design was fully capable of meeting the hazard of the storage (ore on that in a minute), the 18" sprinkler plane issue was not a problem for the sprinkler designer as they call it an obstruction, not storage and the overall spacing and coverage met their needs, and all of this was documented for us.

The pellet people (biased? maybe) are confident that one cannot get pellets to burn readily without blown air. Our Solid Fuel and Oil Board Inspector also noted this was the case, and confirms a propane torch can get a handful to smolder, but once removes they basically self-extinguish. As far as the swelling of pellets from water/moisture, again this was more fiction than fact, with State and pellet people agreeing that when they get wet they turn to sawdust mush, no swelling, just lose shape. The issue with CO is addressed with the 4" infill lines having vented caps so given its enclosure the gas should passively escape, but CO detection has been installed, just to be on the safe side.

The last issue we had was the fire dampers, which will now have the heat releasing pellet moved to the ceiling and connected by cable/wire. This has a far better chance at operation than the same release being 4 and 6 ft from the ceiling.

 

[cda]

Sounds good if all is documented.

Should have said, I like to do field test as in burn stuff

You might get some and see for yourself how it burns

Also throw some in water , and see what happens.

Glad you just do not let things go!!!!

Keep on coming back and contribute answers !!!