Fire in the boiler.

[Scorpster]

So I've been trying to do some distilling on the grain viewtopic.php?f=32&t=72767,
had a few successful runs so was trying some AG rice viewtopic.php?f=34&t=66045&start=30#p7553536.
Now I had an issue with my rice run, but didn't inspect anything, just added sugar etc, and wasn't going to use the internal element.
So fired up the induction cooktop and waited, seemed slower than usual, didn't see drips until the 4 hour mark, but they never really came on stronger. Then I started to see some smoke coming out of the condenser, and still only a drop every few seconds...so I decided that was enough and shut of the cooktop.
Usually the drops stop almost immediately, so when they kept coming out the red flags were all over the field. I though I had maybe clogged my copper mesh, so I started dismantling the still head, and when I pulled it off the boiler there was still smoke and steam coming of the wash. I pulled the lid off and it was still very much at a rolling boil, and it was full to less than an inch from the top. I scooped some out and added some cold water but it wasn't helping much, and I knew by then I had an actual fire in the cavity below the false bottom. So I snagged a handle on the false bottom with my mash spoon and wiggled it around some to try and let the wash flow beneath it. Well it fell about 2 inches once I broke that seal, and then I worked it harder to let wash underneath, it took a few seconds for the boiling to stop.
So time to access the damage, the fire had been between the bottom of the boiler and the 1/2" layer of rice sludge. The sludge layer was shaped like a volcano over the primary fire site, and it had seperated from the bottom, towards the edges it is stuck on pretty good, but elbow grease will take care of it. The boiler itself seems to have held up, no glaring warps in the bottom, and the internal layer didn't melt out as in another pot my kid burnt up.
The induction cooktop did not survive, it had a plastic body and was badly deformed and actually stuck to the bottom of the boiler.
So, some lessons learned...a consumer grade induction cooktop can generate enough heat to start combustion. Trying to distill with a very restrictive false bottom was a failure.
Now for the question that came to my mind as I was trying to figure out what was going on...what the heck was the source of oxygen? Seems to me it should have been very void of oxygen and full of carbon dioxide.

[Swedish Pride]

that sounds scary enough.
glad nothing worse cam out if it than a busted cook top

[still_stirrin]

Now for the question that came to my mind as I was trying to figure out what was going on...what the heck was the source of oxygen? Seems to me it should have been very void of oxygen and full of carbon dioxide.

Carbon dioxide (CO2) is a molecule with one carbon atom (C) bonded with two oxygen (2O) atoms. If you add enough energy (heat), you can break the bonds. Two CO2 molecules will produce two molecules of carbon monoxide (2 x CO) plus one molecule of oxygen (O2) during the reduction. That oxygen will feed a fire. Bear in mind that in order for this to occur, you need to add energy, but you did that with heat and pressure (under the rice cake).

You’re lucky...but don’t do this again. Next time you may not be so lucky.
ss

[Scorpster]

So just an quick update, I haven't done this again My boiler still has the scars on the bottom but still works well with a commercial induction (3200 Watt) unit. I just watched a "Still It" video on distilling on grain and Jesse suggested this exact setup, so I did post a comment and directed him here as a warning to change his suggestion or at least revise it with appropriate information. Hopefully he will catch it and make adjustments so nobody else has this happen. I would like to return to distilling on grain, but haven't found a safe enough solution that I'm willing to invest in. Thumper sounds easy but then you are still doing a separation of the wash and not sure if the flavour gains justify the very slight volume gains.

[squigglefunk]

I have distilled on grain and just stir the mash as it's heating, then when it is almost ready to go I give it a good stir and seal it up. It has never scorched or caught fire but I use propane heat not induction so maybe that's the difference?

[TwoSheds]

I would like to return to distilling on grain, but haven't found a safe enough solution that I'm willing to invest in. Thumper sounds easy but then you are still doing a separation of the wash and not sure if the flavour gains justify the very slight volume gains.

I'm headed in the same direction and a light went off over my head when I realized a thumper is just a steam injection boiler that is heated with steam from mash.

If you flip the script and make your still into a thumper and come up with another suitable source that you can use safely as a steam source (I'm converting a keg when I find the time) you can safely distill your entire mash on the grain, no separation needed.

Thanks for sharing your close call!

[bluc]

I have been going over and over on mash distiiling in my mind for years still see indirect bain marie or continous steam fed as safest option.

[Scorpster]

Yes squigglefunk, I use the stir while heating technique when I have a wash that's heavy in solids. I think the issue with my fire incident was mostly that it was a rice wash, and therefore mostly sludge, no hulls. There was enough sludge that slipped through the false bottom to create a fairly thick layer on the bottom and thicker on top the false bottom. There was also a thermometer with a long shaft that was not far above the false bottom and likely prevented the false bottom from lifting up and stopping the process. I don't think it had anything to do with induction, they seem to be known for more even heating, and it was only a cheaper 120V unit, so max about 1500 Watts.