Cause of clinkers

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Phil May
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Post by Phil May » Wed. May. 06, 2020 5:05 pm

What is the cause of clinkers. I have 1 customer burning nut in hot blast. He keeps getting big clinkers almost as big as a football. I know he pokes the fire because he says it bridges. I burn the same coal in my Harmon and don't have any problems. Would switching to stove size coal help this?

 
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11ultra103
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Post by 11ultra103 » Fri. May. 08, 2020 11:52 am

I've heard burning too hot will cause clinkers. stove coal lets more air through so I would think it would help, but I don't know that as fact.


 
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tcalo
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Post by tcalo » Fri. May. 08, 2020 12:16 pm

Stove temps and iron content in the coal have a lot to do with it. There’s a point at which the iron in the ash liquifies and will fuse together. It’s usually brittle when still warm and can be broken up easily. Once cooled they get tough. It usually happens at higher temps. Just part of burning coal.

 
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Sunny Boy
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Post by Sunny Boy » Fri. May. 08, 2020 12:35 pm

And coal like other hard substances will get soft at high temperatures. If you've ever run a fire poker down into a yellow-white coal firebed you can feel how soft and "mushy" it gets. That's it getting up to the fusion temp where the chinks will fuse together.

That's why you should avoid poking in the middle of a firebed to drop the bridging and poke around the outter edge. Poking in the middle is the hottest "stickiest" part of the firebed. Doing so pushes the softened coal together and forms larger fused chunks that will not shake through the grates. And with time, they just get harder and bigger like your Friend is getting.

Many of the old stoves didn't just have shaker grates like modern stoves. They had various types of rotating, or opening grates to daily grind up and dump those clinkers while they were still relatively small and easier to break up.

If you can keep it below that yellow-white range then fusion become less likely to happen. And let your friend know that poking in the middle of the firebed is not the best place to do that. Break the bridge loose by gently poking and scraping alternately along the sides of the firepot so that it drops as one piece instead of all falling in on one side.

Paul

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