Soft Coal Stoker

alright all you soft coal stoker guys I have a question... I have a stokol stoker im about to install. when making the hearth around the retort how much room should I leave between the tweyers and the hearth around their circumference? and how thick should the hearth be, IE. how low should it be below the top of the tweyers? any information would be helpful!!!

Bituminous or Lignite?

sorry about that, Bit...

I'll move this to Dr. Berlin's forum. He is the resident expert on that soft stuff and should chime in soon. I hope he can tell us what a tweyer is.

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A "tweyer" is a cast section that will allow air to flow into the burning pile of coal

See the sections above that make up the fire pot of my big old obsolete stoker -- If you can find a pic of Gregs old Iron Fireman you will see his round pot - it had four tweyers if I recall right -- beer may be an issue tonight with my recall

Room around the tweyers will depend on the size of the fire you want to maintain but it won't be much since combustion air will not be available except along side and above the tweyers.

Sting, man is that thing OLD.
Yep, Tweyers let air into any combustion chamber. A tweyer could be a pipe with holes in it.

"alright all you soft coal stoker guys I have a question... I have a stokol stoker im about to install. when making the hearth around the retort how much room should I leave between the tweyers and the hearth around their circumference? and how thick should the hearth be, IE. how low should it be below the top of the tweyers? any information would be helpful!!!"

Hi

I would leave no room between the poured hearth and the tuyeres. I would however leave as much space as possible between the tuyeres and the nearest boiler wall; this gives maximum space for clinker and ash to accumulate. I would set the hearth so that there is about an inch of tuyere protruding above the hearth (ususally there are a ring of holes in the cast sectional tuyere that point out, away from the burnpot within the top inch of tuyere, this is to encourage clinker formation, however, not all stokers have this feature, yours may or may not, but be sure to pour the hearth just below those holes, do not cover them if they exist. I would pour the hearth about 3" thick minimum; if you wish to keep a large air space around the base of the stoker, use sheet steel to hold the hearth up from the bottom of the furnace and pour the hearth over it. glass-reinforced concrete works well for me, however there are more expensive and long-lasting materials to use.

DVC500 at last wrote:Sting, man is that thing OLD.

Ahhh -- not so old

It was new in 1954!!!

well what I was thinking as for the dim. between the tweyers and the hearth is to make a sleeve for the pour, then remove the sleeve when the concrete has cured and create about a 1/4" air space so the tweyers can be removed for good cleaning rather than pour tight. as was said in a previous reply there are holes about 1" down from the top of the tweyers. I was originally going to try to get away without pouring a hearth and suspending the retort in the firebox and let the ash roll off onto the floor, but now the more I read im not sure that would work all that well. I have only ever seen one of these in action once and that was in a 400 National and the stoker was a 500# per hour, there was no hearth but the retort was sitting on the concrete pad the boiler was sitting on. But I was also worried about cracking the retort from the extreme heat being generated.

in order for the stoker to function properly, you need a hearth; ideally you would have a big boiler and not have to pour the hearth all the way to the boilers edge and could set a large ash can under it, thus allowing you to rake the ashes off the hearth into the can and remove it once it's cooled. Most boilers will not have anywhere near that much room and thus you must pour the hearth all the way to the boiler wall. you need a good bed of ash on the hearth to insulate the fuel bed, usually about 4" of ash with regular removal of any clinker that forms (once/twice per day, sometimes less). I wouldn't bother preventing the hearth from reaching the tuyeres, the expansion and contraction of the tuyeres will loosen the concrete such that it will not have a tight fit. those tuyeres should last years and years without damage, if they are damaged quickly, you are firing very improperly: using too low of a feed rate and too much air, or allowing the hopper to run out of coal. this is why when you set the air controll, the fire should produce no visable smoke at full fire, but just. do not allow too much air or the fire will burn low in the pot and you will burn the retort/tuyeres and, in some cases, the screw.

this is all good information and im glad im going over this with you guys before I do the final install. Its going to be a learning process, as I hand feed my #3 American right now. So what your telling me is that when firing the stoker im going to leave the loose ash accumulate around the tweyers and pick the clinkers? what did you mean about insulating the fire?
Im wanting to try out this stoker in a #2-7 American Standard which has 5.28 sq feet of grate area. I didnt think about just making a hearth maby 12" all the way around the retort and tweyers for the accumulation of ash then rake them into a pan stored in the ash pit. This setup when complete is going to be capable of hand fire or stoker fire by pulling the stoker and replacing the grates. I plan on laying 2 courses of 8 inch block and set the boiler on its base putting the CL of the fire door at about 36" from the finished floor. I figure this will make tending and cleaning the fire easier, and making the area under the retort excessable. I also have a Gentleman Janitor hard coal stoker, off the top of my head I think it has an 18" pot with and external hopper set up just about the same way as the Stokol Bit stoker. So what im thinking from the last reply im going to make hearth around the retort and build a carriage for both stokers to fit on (one at a time of course) with wheels so that they can be pulled out away from the boiler and serviced or cleaned. I will have to take and post some pictures of what im talking about are far as these stokers and boiler I plan on using. can you guys provide some more information about how the BIT stoker fires and how to tend to it?