Floor of Fire Box Around Underfeed Stoker

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Short Bus
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Stoker Coal Boiler: Kewanee boiler with Anchor stoker
Coal Size/Type: Chestnut / Sub-bituminous C
Other Heating: Propane wall furnace back up only
Location: Cantwell Alaska

Post By: Short Bus » Mon. Apr. 16, 2012 12:46 am

I have a Anchor stoker, similar to the Iron Fireman, and that generation of Bituminous stokers

The question after reading other posts, is how should I have built the floor of my fire box?

I set the stoker box on the floor, set the boiler base around it, filled with sand, and set fire brick in high temperature mortar to create a flat floor about one inch below the top of the tuyeres. Is there a better way to allow more room for clinkers or concentrate heat around the fresh coal?

We did this based on how my father saw it done in my grampas house, when they removed the wood fire grates and added a stoker to the furnace.

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freetown fred
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Hand Fed Coal Stove: HITZER 50-93
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Post By: freetown fred » Mon. Apr. 16, 2012 8:15 am

Just an old farmers thoughts, but, if it was good enough for your Grandpa ( common sense generation) It oughta be good enough for you--it's really not rocket science & you know that SB. ;) PS---plus, it sounds real good to me. :) ECONOMIC & EFFICIENT--oooh- rah

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europachris
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Post By: europachris » Mon. Apr. 16, 2012 8:57 am

That's pretty much how it's done. I have installation drawings from Will-Burt that show it this way, aside from using castable refractory cement rather than firebrick.

I used firebrick and refractory cement when I did my install and it worked out well. If I did it again I'd use the castable refractory because cutting and fitting the bricks was a royal PITA and a huge mess. It's just hard to find castable refractory and the firebricks were on sale at the local home center at the time.

The only reason that this installation method was developed is due to the nature of the stoker installs - i.e. converting hand-fed boilers and furnaces. Since the stoker had to go in through the ash pit, there was no place for an ash can underneath the unit. Due to the fortuitous quality of bituminous coal ash fusing relatively easily, it was possible to just let the ash accumulate, fuse into a clinker, and remove it through the firedoor.

Otherwise, for a "new design" stoker boiler, one could use something like the Prill rotating ring retort and set it up like all the other anthracite burning units and just have the ash fall into the can. I assume there would be a bit of carbon carryover into the ash with this type of stoker compared to the clinkering style, but unless it was a large (>15~20%) amount, the benefit of not having to let the fire cool, dig around for a red hot clinker and haul it out with tongs twice a day would outweigh the carbon loss.


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rockwood
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Post By: rockwood » Mon. Apr. 16, 2012 11:14 am

Shortbus,
I think you did the floor (hearth) right but the hearth around the tuyeres would usually slope up toward the walls of the combustion chamber. This does leave less space for clinkers but I believe it was done that way to keep the ash closer to the heat so there will be more clinkers formed instead of lots of ash just sitting on a flat hearth. A sloped hearth would help keep the fire hotter and there would be a less chance of unburned coal falling away from the fire.

I'm not saying you need to re-do the hearth but I think that's what they commonly did. If you just leave a sloping layer of ash and clinker you would achieve the same result.

Old furnaces/boilers would commonly have curved firebrick like this

Does your boiler have these?

How much space is there between the tuyeres and the wall?

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Short Bus
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Posts: 510
Joined: Sun. Jan. 10, 2010 12:22 am
Stoker Coal Boiler: Kewanee boiler with Anchor stoker
Coal Size/Type: Chestnut / Sub-bituminous C
Other Heating: Propane wall furnace back up only
Location: Cantwell Alaska

Post By: Short Bus » Mon. Apr. 16, 2012 2:21 pm

Trust me I'm not changing my burner set up.
I think I have about 8 to 10 inches from the tuyeres to the boiler walls, my boiler is a vertical cylinder at this elevation, it is a Kewanee.
If I did it again I would probably slope the floor up gently, away from the tuyeres, but it is working fine.

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