What Makes a Klinker?

Modern and vintage hand fired coal stove are similar to a wood stove and in some cases can burn either. They need to be regulated and fed by hand usually every 12 to 24 hours depending on your usage. They require no power to operate making them ideal for rural settings with long power outages.
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Post Wed. Dec. 04, 2013 12:48 am

Just started burnin coal and was wonderin what causes the klinkers and if there's a way to reduce them. They look like oyster shells and I poke the bed and lift them out. Burning stove coal in a Harman sf 360 in NE Btitish Columbia.

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grumpy
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Post Wed. Dec. 04, 2013 12:58 am

Thats a great question..

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Berlin
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Post Wed. Dec. 04, 2013 1:46 am

What causes clinkers? Answer: allowing the fuel bed to exceed the AFT (ash fusion temp.) of the coal.

Some coals won't even clinker in a (clinkering-type) underfeed stoker (designed to make the coal clinker to melt the ash down = reduce ash volume)

Some coals will clinker in hand-fired stoves under a good hot fire (or even not so hot) as you've found out.

typically, pyritic sulfur (iron) will give red ash coals which will give lower AFT's and a greater propensity to clinker under home heating use.

To reduce the likelyhood of clinkers showing up in your fuel bed DON'T poke or disturb coal bed from top, keep a DEEP fuel bed (8-14"+), and reduce the underfire air to the minimum necessary to heat the house. If following those instructions doesn't help, you may need a larger appliance for the coal you're burning - a larger stove will allow you to not have to burn it as hot.
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Post Wed. Dec. 04, 2013 8:01 am

The general consensus is that klinkers form only in hand fired appliances. Nyet!!! I had a D&S stoker stove from Schylkill Haven Pa. that burned rice coal and it was a HOT momma. I was good with just about everything except rice coal from the old UAE mine. Every time I burned UAE coal the ash would fuse into a solid cookie and hang off the end of the grate. Sometimes it would be solid enough to stay together and come all the way out and hit the glass in the top door and not break off and fall into the ash pan below. Then the coal would back up on the top of the grate and spill over the sides.

UAE coal had a higher (than other coals) iron content and it would fuse in the ash. Only two ways I could keep that from happening. Mix the UAE coal with another coal and/or restrict the amount of combustion air to cool burn. Shame really. Spending money for something that worked too good and having to take steps to make it like everybody else's coal.

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Post Wed. Dec. 04, 2013 10:43 am

My ash always falls off the bed in one big clinkered chunk. Blaschak bagged rice. Sometimes it'll hang over the edge up to 5"!
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Post Wed. Dec. 04, 2013 11:28 am

The simple answer is that a clinker is ash that has fused together as a clump. In a hand fed, it can hide in the bottom of the coal bed just taking up space that could be better used for burning coal and/or block combustion air coming up thru the coal bed. Red ash tends to fuse more easily than white ash.

More good reading here.
Clinker Removal? Time to Go Fishing!

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Post Wed. Dec. 04, 2013 4:23 pm

Great info. I'll quit pokin,turn down lower air in,and fill the box.
How do I know how much lower air to give?
Should I restrict upper air also?
Dialing her in, thx guys,big help!

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Post Wed. Dec. 04, 2013 4:40 pm

This is for anthracite. Bituminous is a different animal :lol:
Got a match wrote:I'll quit pokin,turn down lower air in,and fill the box.
Nice and deep, I like to keep 9-12 inches deep..
Got a match wrote:How do I know how much lower air to give?
Primary combustion air will dictate how hot it burns. You'll need enough to keep ya comfortable :D
Got a match wrote:Should I restrict upper air also?
A generous portion of secondary air should be used during the first 30 minutes or so after loading to burn off volatiles once the blue dancers show up. After that, close it down to just a hair width.
Got a match wrote:Dialing her in, thx guys,big help!
Trial and error, stay observant and learn from what you see. These basics are just a starting point 8-) Keep us posted on your progress :up:
Last edited by Lightning on Wed. Dec. 04, 2013 6:10 pm, edited 1 time in total.

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Post Wed. Dec. 04, 2013 5:40 pm

Good last answer
Me and my eye brows thank you

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Lightning
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Post Wed. Dec. 04, 2013 5:50 pm

Got a match wrote:Good last answer
Me and my eye brows thank you
Ut oh, did the puff back get you?

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Dennis
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Post Wed. Dec. 04, 2013 6:03 pm

If your from BC Canada,your most likely burning bit. coal,look in the bit section and read away.Welcome to the forum

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Lightning
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Post Wed. Dec. 04, 2013 6:07 pm

Dennis wrote:If your from BC Canada,your most likely burning bit. coal,look in the bit section and read away.Welcome to the forum
Sheesh lol good point. I gave advice for anthracite. :lol:

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Duengeon master
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Post Wed. Dec. 04, 2013 8:04 pm

Dennis wrote:If your from BC Canada,your most likely burning bit. coal,look in the bit section and read away.Welcome to the forum
Yeah and go to Alberta to get it... No HST tax there!!! LOL!!
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Post Wed. Dec. 04, 2013 8:22 pm

I was burning Blaschak last season and had tons of clinkers. I switched brands this year and haven't had one clinker, I've been drowning in ash though. I've been running the stove at the same temps as last season. I've been getting twice the ash, almost 2 full ash pans during shake down. It's amazing how different coal veins are! The clinkers were pretty easy to remove. I just dug them out of the top of the coal bed with my poker. Fyi, I am running a handfed.

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Post Thu. Dec. 05, 2013 10:23 am

Read about bit coal after advice on this forum. Very informative.
We did get our coal out of Alberta. 40.00 bucks a ton.
Were on a quarter section which is a good thing cause this stuff stinks.
Fort St John this morning is - 30 cel. Stove is working great after advice from all you experienced coal guys. Reduced lower air and filled the box. Klinkers are golf balls now instead of grapefruits and not as many as before.I read in the bit coal section to run with no rain cap on chimney for draft which is good cause when we first fired up a gas explosion blew the cap off the stack anyways.
Thx again guys,there's no lookin back now!

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