Clogged nozzles

[infinitymike]

I've been having trouble with the nozzles clogging up.
My ash has been turning into "concrete".
Sometimes it's real hard to scape the bottom of the chamber and when I loosen it up some of the nozzles are clogged solid.
I had to take a splitting wedge and tap it with a hammer to break through!
The WG has 6 nozzles down the center of the combustion chamber.
They are about 5/8" x 2".


Obviously, I have also been having trouble with gasification, stack temps only 150-200*
Thursday I did a total cleaning of the unit.
Swept clean the burn chamber and everything was spotless.
Saturday night I couldn't gasify at all. In fact I put my hand over the fresh air intake and barely felt any air moving.
Normally it sucks air like a vacuum.

I had a t least 4-6" of red hot coals and several charcoaled splits. I wasn't hearing that roaring sound it normally makes when I open the combustion chamber.
I can't open the gasification chamber, it interrupts the air flow and you lose gasification instantly.

I let it burn down enough to move the coals to find 3 clogged nozzles again.

And I'm tellin' ya they are packed solid and hard as a rock.

What's going on?

 

[hobbyheater]

I've been having trouble with the nozzles clogging up.
My ash has been turning into "concrete".


And I'm tellin' ya they are packed solid and hard as a rock.

What's going on?

This is a really wild guess. When cleaning the Jetstream burn chamber, I have found what appears to be a plate sized clinkers after I have been throwing a mixture of wood clips, sawdust and sand into the fire after cleaning up the woodshed floor. Up until now I have never thought of taking a picture.
Have added a picture of the Jetstream. It operates a little different than your down drafting unit.

 

[Singed Eyebrows]

I've been having trouble with the nozzles clogging up.
My ash has been turning into "concrete".
Sometimes it's real hard to scape the bottom of the chamber and when I loosen it up some of the nozzles are clogged solid.
I had to take a splitting wedge and tap it with a hammer to break through!
The WG has 6 nozzles down the center of the combustion chamber.
They are about 5/8" x 2".


Obviously, I have also been having trouble with gasification, stack temps only 150-200*
Thursday I did a total cleaning of the unit.
Swept clean the burn chamber and everything was spotless.
Saturday night I couldn't gasify at all. In fact I put my hand over the fresh air intake and barely felt any air moving.
Normally it sucks air like a vacuum.

I had a t least 4-6" of red hot coals and several charcoaled splits. I wasn't hearing that roaring sound it normally makes when I open the combustion chamber.
I can't open the gasification chamber, it interrupts the air flow and you lose gasification instantly.

I let it burn down enough to move the coals to find 3 clogged nozzles again.

And I'm tellin' ya they are packed solid and hard as a rock.

What's going on?

Are you burning different wood than normal? If I put willow in my boiler it will clog the nozzle, this is the only wood I have found that does this, Randy

 

[infinitymike]

Are you burning different wood than normal? If I put willow in my boiler it will clog the nozzle, this is the only wood I have found that does this, Randy[/quote]

I was thinking that could be the problem. I've been burning maple, cherry, and locust. I tapped into my 4th rack of wood and I think I've burned a few loads of Sassafras.
It was c/s/s in sept 2011. The bark is thick and narley and the wood is a golden/yellow color. I re-split about 4 pieces and they were 22% moisture.

I'm going to tap into the 5th rack which is all red oak and see if anything changes but I still have the same problem it also was c/s/s at the same time.

 

[HeatFarmer]

I would bet the red oak isn't going to be any better....It is notorious for taking a LONG time to dry. Most people usually wait 2 years before thinking of burning oak. I'm finding with the wood I cut in April of last year, that it even has too much moisture to burn practically unless I mix it with some really dry pallet wood or pine slabs which are very dry.

 

[infinitymike]

I would bet the red oak isn't going to be any better....It is notorious for taking a LONG time to dry. Most people usually wait 2 years before thinking of burning oak. I'm finding with the wood I cut in April of last year, that it even has too much moisture to burn practically unless I mix it with some really dry pallet wood or pine slabs which are very dry.

Yeah I know, this is the main problem I've been having since I started burning. I'm grateful that this year has been mild.
I think next year will be better.

 

[711mhw]

Mike, when you say clogged, do you mean that you have a coal semi stuck in the slot? Or is it this hard "nugget" that you describe?
I'd be careful of how much physical force that you subject the center brick to, they're not so cheap. I usually try to stir the coal bed around a little, letting the fines get sucked through and into the cyclone and leaving anything that won't fit thru the slot continue to burn down. It seems that even with the slots covered completely with coals and new wood on top (24/7 burn, no storage) that I don't have a problem. I just leave the coals there intil they are small enough to get sucked through. Your point about low air flow backs up your cloging assesment, is your cyclone good? I've had the tray fill up and the bottom of the cone start to fill up on me. Pull your tray and stick your finger up the hole in the bottom - that sounded bad!- to be sure that is open. Might just be that different and wetter wood??

 

[infinitymike]

711,

Believe me, I was very careful when I was "chiseling" out the stuff. I was very nervous, the last thing I wanted was to break a section.

It definitely is not just a coal or a clinker.

It was filled solid.The whole nozzle was closed over. It almost looked like it was part of the refractory.
Not only that but as I would rake up the coals to get an even bed to lay the new wood on it felt like the bottom layer was stuck to the refractory.
I had to push and pull to scrap up the bottom. It was really strange, the way the bottom was "stuck"

if I think about I hadn't started burning the sassafras, I believe i was using a lot of oak.
They were rounds that were laying on the ground. My tree guy found them on a job and gave them to me, thinking they would help with my green wood problem.
i don't know how long but the bark was all soft and rotted.
When I split them open they were about 24-26% moisture.
Maybe the rotting bark was clogging it up?

 

[thecontrolguy]

I've been having trouble with the nozzles clogging up.
My ash has been turning into "concrete".
Sometimes it's real hard to scape the bottom of the chamber and when I loosen it up some of the nozzles are clogged solid.

My guess is that your wood is potentially very oily (naturally) and high-moisture or otherwise burns in such a way that it produces more gas residues than, say, oak. If that is the case, then it forms creosote-like tars that condense on the refractory, inhibit air-flow and bake into clinker sheets. At work, as the ash flies throught the gasifier and into the oxidizer, it plates out on the refractory and becomes 'glasified' with the same reusults that you describe. We are using the worst hog fuel available, with moisture anywhere from 15% TO 65% and long stringy bark to fine sawdust. Lots of troubles, lots of clinker on the refractory. You could try to ensure your wood supply has been artificially dried (like in your boiler room for several months) and then select different type of wood to try and see how it performs. That would eliminate the moisture variable and narrow it down to issue srelated to certain species. Happy chipping.

 

[maple1]

I'm thinking it is just the extra moisture coming out of the wood - kind of like cement dust (your wood ash) + water = concrete?

 

[Fred61]

I suspect it is either an overabundance of bark or it is sugar from one of your wood species. Bark will create clinkers.

It's not hot enough at that location to get fused ash.

 

[hobbyheater]

I've been having trouble with the nozzles clogging up.
My ash has been turning into "concrete".
Sometimes it's real hard to scape the bottom of the chamber and when I loosen it up some of the nozzles are clogged solid.
And I'm tellin' ya they are packed solid and hard as a rock

Burned some dirty wood and these concrete like chunks are what I got after a 7 hour burn.

 

[infinitymike]

Lots of good thoughts.
I think it might be the heavy bark from the sassafras.
I split some of it off and it is real damp and stringy.
I burned a load maple again and no problem.
I guess I need to let the sassafras really season and debark itself

 

[Trex83]

Lots of troubles, lots of clinker on the refractory. You could try to ensure your wood supply has been artificially dried (like in your boiler room for several months) and then select different type of wood to try and see how it performs. That would eliminate the moisture variable and narrow it down to issue srelated to certain species. Happy chipping.

Hello guys, off the top of your head, would you think that burning agricultural residues with higher ash content would run into similar problems?
I am writting a proposal to test agricultural residues and purposely grown agr. biomass for tryouts in downdraft gasifier. There are a few experimental plots in QC, NY and ON for biomass (besides wood) and will try to get my hands on briquettes or pucks.
Any ideas accepted!
Cheers,
Trex83

 

[Trex83]

Burned some dirty wood and these concrete like chunks are what I got after a 7 hour burn.

Can we say the third picture is 'slagging'? I am not familiar with ash qualifiers...
Thanks
Trex83