Clinker

[dirvine96]

I've been reading many of the posts and the term clinker pops up every so often.

What is a clinker?

What does it look like?

What can I do to avoid getting them.

Just started burning coal this year. I've got a manual feed US Stove Hot Blast. From what I've read I've got the type of stove that can get clinkers.

Thanks Don

[Richard S.]

Basically a clinker is where the non burnable material has fused together. If you have a stoker stove you've no doubt seen some small ones in your ash but they should easily be breakable even using your fingers and really isn't considered a clinker. You're more likely to get them when burning a stove/stoker at it's max.

The issue is if they are very hard and do not break easily, in that case the won't go through the grates or could get logged somewhere in some stoker mechanisms. If you aren't having that problem don't worry about it.

[LsFarm]

Here is a photo of a clinker. It is as our forum leader [he prefers administrator] said, a bunch of ash fused together.

The clinker you see is one piece, the can in the background is a standard size spray can. This clinker is about 18" long and 8" wide. It was created by burning high-ash, low AFT bituminous coal. AFT is ash fusion temperature, or the temperature that the ash will become liquid and flow and stick together.

It doesn't show real well in the photo, but there are lots of areas that look like melted glass.

Anthracite usually won't make any clinker, or very little. The AFT of anthracite is about 2700*, but it is half that for Bituminous. The coal I was burning that made this clinker was very poor coal. That clinker was pulled off the grate of my firebox after three days of burning the lousy bitum. coal. I would notice after two days that the fire wouldn't burn as hot and by the third day, I couldn't keep the fire going. So I would shovel out the unburnt coal and ashes, and then with a hoe and a hook pull up and remove the sheet of fused ash.... the clinker.

It would completely cover the grate, blocking the air to the coal fire.

Anthracite might ocasionally have a few pieces of ash fuse together, but I've yet to see anything bigger that 1-2" around. I have several old coal burning brochures that say not to poke into the hot coal bed, that this causes clinkers. I guess you force the pieces of ash together when they are near molten, then they stick together.

Hope this answers your question. Greg L

I can take and post more photos of clinkers if you wish, I saved a few because of their appearance.

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[Richard S.]

Here is a photo of a clinker. It is as our forum leader said,

Leader? Ok got my fall off the chair laugh today.

[LsFarm]

I fixed it!


Greg L

[coaledsweat]

That is one ugly beast! I'll bet it put up a hell of a fight.

[LsFarm]

The clinker is actually quite light in weight and very fragile. I wanted to preserve one of the truely large clinkers. So I was carefull with the one in the photo.

The clinker in the photo weighed less than half what the can of starting fluid weighed. A clinker is mostly expanded glass and minerals, which is exactly what house insulation is made of.

Greg L

[Richard S.]

The clinker is actually quite light in weight and very fragile.

They can be as hard as rock, I've seen tham as big as softballs. Generally those have rust red color to them.

FYI, Greg Rich or richard is fine.

[barley master]

we encounter them at work all the time. if they are hardend they will break shakers if they get lodged between them. our cause is due to reaching the ast and actually melting it because of plant load conditions. one of my units has a glass front wall because of the coal actually melting and ran down the wall. its as hard as and smooth as glass. not good but it does a great job of protecting the existing refractory.

[LsFarm]

Here are two photos of clinkers I just recently removed from my firebox. I am burning a much higher quality bituminous coal this year. And I'm mixing it with Anthracite in various ways.

The poor quality coal I burned last year would clog the grate with a huge sheet of clinker in only three days. The better quality coal this year is taking over a few weeks to create enough fused ash to start to clog the grate.

The photo with the soda can shows five big clinkers, they were separate and mixed in with the ash from a burnt out fire.

The close-up is of a particularly hard an glassy clinker that shows the degree that the ash melts together.

Greg L

[Charlie Z]

I remember them in old driveways. Ouch.

[EasyRay]

Wow! Thank God for Anthracite. I don't think I could deal with that, every couple of weeks.

Regards, Ray

[LsFarm]

Hi Ray, I agree, last year it was a royal pain to shovel out the firebox every three days. This year isn't too bad, when I'm home I burn the less expensive Bituminous, when I'm away my caretaker burns mostly anthracite. The anthracite is a much easier coal to use.

The quantity of coal I burn, somewhere around 2-3000# a month, is enough that the price savings of the Bituminous coal is attractive. I do create a huge pile of ash as well.

Letting the fire go out, cleaning and inspecting the firebox and scraping fly ash and soot off the heated surfaces every couple of weeks isn't too bad of a chore.

Greg L

[EasyRay]

I guess you could call that your part time job. I have a manual feed stove. Fifteen minutes in the morning and fifteen minutes at night and thats it. Any clinkers I get, just shake right out.

I don't have the patience for your set up. I want easy and dependable. I admire your perseverance.

Regards, Ray

[LsFarm]

I want easy and dependable too!! With just anthracite, It is pretty much load, shake, empty the ashes, close the door and forget it. But I don't have enough anthracite to get through the winter. The Bituminous is helping me get through this season.

Next year there will be many changes, I'm going to have a stoker setup inserted in the loading door of the boiler. the stoker will have a hopper. I hope to be just filling the hopper, and emptying the ash drawer every day or two.

The Huge advantage with my coal boiler is that even with the warm temperatures we are experiencing, I would have burnt over $2500 of propane so far this heating season. And this is to keep the house at 60-62* and heat domestic hot water.

So far I would guess that I've burnt $300-400 in coal, and the house is 70* with unlimited hot water. It's worth the work.

Once the plumbing is done the shop will be heated from the same boiler, and that propane bill will go away as well.

The BTU's /dollar from coal is the highest of any fuel source I can use.

Take care, Greg L

I used to cringe when family came over for Thanksgiving or Chirstmas because I could just hear the propane burner in the house's boiler roaring to keep the house at 68*. This year I may have to TURN DOWN the thermostats 'cause the house may be too warm!! WHAT A LAUGH!

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