Size of Your Firebox, Bed of Coal

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LsFarm
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Post Sun. Feb. 05, 2006 2:06 am

Hi KTM, the link below is to a pretty good supplier of tubing, parts and supplies for boilers, tubing etc. They have some water heated space heaters.

http://www.ctwoodfurnace.com/

I was hoping that your boiler came with a really good, detailed breakdown diagram for maintenance and cleaning. I did visit the AHS site, thanks for the link.

Take care, Greg L

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ktm rider
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Post Sun. Feb. 05, 2006 2:27 am

Not a whole lot to it really. The grates are removeable if need be. Not much maintenance involved. As far as cleaning, this is my first season with this boiler but, when I had my outdoor boiler, I used a shop vac to clean and then used my grandfathers technique and got the ol' paint brush and old motor oil and lined the firebox with a coat of oil. Some people disagree with this but his old coal stove lasted forever !
He also did this with his farm implements. ( which I also do ) Especially if they are left outside during the winter. Works great. He would coat the whole implement !!!

oilman
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Post Sun. Feb. 05, 2006 6:07 pm

Greg, I have various diagrams, etc. What exactly do you want to know about? I also have a couple of used stokers. (just the stoker burner assembly)

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LsFarm
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Post Sun. Feb. 05, 2006 6:29 pm

Hi Oilman, I'm interested in seeing how several different stoker designs work, how and if it would be possible to incorporate a stoker into my stove.

The big problem with a stoker for me would be finding sized and graded coal in my area.

I'm always interested in new knowledge. The different stoker feed designs and burner grates, air flows etc really intrigue me.

I'll PM you with my regular email address. If you have some info you could scan and email me I would apprciate it. If not I'll PM you with various questions about design if you don't mind.

BTW: My boiler is doing pretty good this weekend, I'm not home, I'm out working, but my farm caretaker says it is maintaining 140-150* at the end of an 8-10 hour burn with plent of coals remaining for a fresh load of coal to be added onto. We are to have 15* nights this week and I'll be back on Tuesday to feed the boiler myself and watch it's performance.

Thanks, Greg L

AL-53
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Post Sun. Feb. 05, 2006 7:09 pm

Greg

What about some type of auger feed ..on a timer...or temp sensor...or a combo of both....do not know if it could work for you..was just an idea...

Al

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LsFarm
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Post Mon. Feb. 06, 2006 3:30 am

Hi Al, I've been thinking along the same lines, either a timed feed using an auger or maybe a temp sensor off the aquastat that enables a feed if the water temp goes below a minimum setting.

Just thinking and learning. I can make a new door for the boiler real easy, and incorporate some form of stoker or feed mechanism. But before I use too many brain cells on this I need to see if I can find properly graded/sized coal to buy. Otherwise it will be a real pain.

Supposed to be down to 12* on wednesday night !

Greg L

AL-53
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Post Mon. Feb. 06, 2006 5:54 pm

Greg..with the right size auger you might be able to use up to nut coal or maybe bigger...If you could find an old 4 inch earth auger like the ones they use to do test bores with...they may work...just need to figure out the power...a gear reduction motor...figure out your rpm needed....like 2 rpm depending how much coal will be in the feed tube and so on...

Al

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LsFarm
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Post Wed. Feb. 08, 2006 7:12 pm

Last night when I loaded the firebox for a cold night, I moved the temporary back 'wall' of my coal firebox. This morning there was a 6" section of grate exposed near the middle of the firebox at the rear of the coal fire.

So I dug up a piece of heavy steel to fit over the grate to block the air from below, and welded on a angled plate to form the back wall of the coal pile. This is another temporary experiment. The steel I used for the angled plate is too thin to hold up to the heat generated by a hot coal fire, so if this works I will make a similar wall or barrier with a layer of firebrick to protect the steel plate from the direct heat of the coal fire.

Below is a photo of the temporary steel wall or coal barrier with only tack-welds. It fit nicely up against the firebrick sides, and the heavy steel 'foot' made it very stable. The barrier is sitting on top of the ash pan for the boiler.

I think it is going to work very nicely to shorten the firebox for coal. I may add a top plate behind the barrier to keep coal from getting behind from over enthusiastic shoveling or over filling the coal pile.

I now can dump a full five gallon pail of coal into my firebox, about 40# worth, It should burn about 10-12 hours.

Greg L
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fireboxwall.jpg

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LsFarm
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Post Thu. Feb. 09, 2006 7:24 am

The sky is clear, and the outside temperature is 3*- 4*. The house has dropped off from 70* to 68* or so. The hotwater baseboards are only luke warm. But I'm a long way above the 58-60* that I kept the house at when I burned only propane. I burned only $5 of coal last night, if that, which is much better than the $30-$40 of propane I would have burned to keep the house 10* cooler.

However, I am a bit disapointed, I had a large load of coal in my boiler last night, in anticipation of the temperatures dropping below 10*.

The house stayed warm but the heat load from the house really pulled a lot of heat from the boiler. This meant that the combustion blower ran most of the night and the coal was being burnt at a high rate. The pile of coal after 9 hours had burnt down to mostly glowing embers with a little blue flame dancing above. The 8"-10" deep pile of coal was only 2"-3" deep and not putting out much heat.

The water temp was down to 120* which is barely enough to keep the temperature sustained in the house. But much warmer than the former small boiler would have been able to maintain.

I 'gambled' with an experiment last night, I used only coal, and didn't toss in the usual three big oak logs into the back of the firebox behind the coal. I needed those logs last night, but thought that with the larger than normal load of coal I would get through the night and maintain 140*+ water temp.

The ash pan was very full this morning, and a lot of the ash was thumb-sized 'clinker' and burnt-out coal. My coal is apparently poorer quality than I had thought.

So tonight, I'll go back to my normal routine and add a few logs to the firebox for extra heat. I need to find another source for coal in Michigan, hopefully anthracite is available somewhere. I'd like to get several bags of anthracite to try a similar experiment with to see just how much better, hotter and longer it will burn.

I guess I'll be on the phone today searching for a source of anthracite.

Greg L LsFarm

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Berlin
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Post Thu. Feb. 09, 2006 2:25 pm

Well, I think I may be able to help with a couple of things. first, you are using anthricite. if you were using bitumnious you would have better controll of the fire, few clinkers, but you would have black smoke and the coal would fuse and expand together in mid phase of burning.

1. clinkers, is fused coal ash directly due to the temp of the coal bed and make up of the ash more directly, the main culprit is iron pyrite content (the lower the better), most reputuable coal mines, even anthricite ones should tell you what the Ash Fusion Temp is or AFT, the higher the better.

2. when the coal "crusts over" which is odd in anthricite but still occurs with some coals; it is related to the free-swelling characteristics of a coal and this is generally much more pronounced in certain bituminous coals. however it is not a problem. Also this is NOT a clinker. the key to solving this problem is as you have already begun to discover - opening up the overfire air. however it is best to route the air though a pipe in the firebox first to heat the air and then to the fire rather than just through a door so that you ignite gasses more fully and increase the efficiency of your boiler, not decrease it.

3. when talking about the coal bed, providing you are using at least 1x1 coal or greater (and decent coal) you should have no problem making the bed of coals at least 20-28" thick and possibly half of that new coal. obviously this only works if your boiler is physically deep enough for that and it looks like yours is not. Make the bed deeper! not wider or longer. this will make your coal burning experience much more enjoyable.

4 when having problems burning coal in an easy manner also look to air issues, you have a forced underfire air system, so you should have very easy operation, however you don't. This may be partly due to air escaping around the coal bed when the blower is on and may also be related to problem 2. did you cement your firebrick with refractory cement? is the only place the air can go through the bed of coals?? the firebrick you have laying on the grate is that airtight?? if not, then it needs to be airtight. even a little air escaping around throught the firebrick and throguht he firebrick on the grate and other areas will cause signifigant problems; any air must go through the bed of coals, not around them.

5. your coal seems to be old anthricite, do you know how long it's been sitting around? I've seen anthricite in a small pile 30 years old that absolutely will not burn, even though it still looks fine, it has decomposed and oxidized away most of its BTU content. obviously this has not happend to your coal, but the fact that it has been sitting around for a while, possibly unprotected from the weather may make your situation worse.

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Post Thu. Feb. 09, 2006 6:41 pm

Thank you Berlin, Great information!!

Unfortunatly for me what you describe for Bituminous coal is pretty much what I'm experiencing. When I add fresh coal to to a hot fire, I don't get the blue flame for about half an hour to an hour, depending on how deep I piled on the new coal.

The initial smoke off the new coal is yellowish gray then black-gray. Once the coal has all started, I get the blue flames dancing above the coal. I have never seen blue flame without the heavy yellow flames first. The only variation is when I have a shallow bed of hot coal and add only a few inches of fresh coal and have the combustion blower on high, then I get more of a blowtorch effect from the large volume of air going through a low-restriction bed of fuel.

The coal usually does bridge and stick together, but I'm unable to tell if it is swelling when it sticks together. I get a lot of ash, and clinker. In the photo below you can see the ash from 40 or 50 pounds of coal. There is in the ash pan several large pieces I picked out of the coal bed that were too large to drop through the grate.

I have found a source for stove/nut coal, but it comes from Kentucky, and is $180 a ton, and I have to shovel it into my truck or containers, the guy has no loading equipement. I doubt if it is any better quality than the stuff I'm burning now.

The coal I have is of very questionable pedigree. It is from an old coal yard, and is from a huge pile, the scrapings and remains from the numerous coal bins at the yard. I have no idea it's age. But it has lots of volitiles that burn off when initially put on a fire.

I'm going to do some more research to try to find a coal source here in michigan, or maybe if Dave decides to buy his local stove store, maybe we can share a railcar full of good anthracite..

Below are two photos, one of the ash pan full of clinker and burnt out coal, and the other showing the coal fire after about 4" of fresh coal was added and the fire has burnt about half an hour . The full bed of coal was burning with the yellow flame you see in the back, before it finally burned clean and has the blue flame in the front.

I have the unused grate sealed with a steel plate, all the combustion air comes through the coal bed.

Thanks again for the good information.

Greg L LsFarm
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Newfire.jpg
Ashpan.jpg

Ken L
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Post Sun. Nov. 19, 2006 4:14 pm

I am wondering how I can effectively reduce the size of my firebox in my hearthmate 2200 insert. I have a small house and am blown out the door with the heat. Anyone have any specific ideas. I tried putting bricks in last winter but I kept losing the fire. I suppose it could be a trial and error thing but if anyone has suggestions they will be greatly appreciated!! Thanks

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LsFarm
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Post Sun. Nov. 19, 2006 5:12 pm

Hi Ken, welcome to the forum. I'll try to help.

Whenever you reduce the size of the firebox, you must make sure that you are completely blocking the combustion air that would normally feed the blocked firebox area. If this air is allowed to get around the burning coal then the fire will go out.

The wall that you create to block off the unused firebox needs to be able to withstand very high temperatures. I think you said you used firebrick. This is what I used but they fell over when stacked 2or 3 high. So now I have a tall steel grid with brick stacked in the grid to protect the steel from the heat.

I had problems blocking off the air supply to the unused portion of the firebox. Eventually I found a way to block the grates without stopping their movement during shaking.

I'll try to find a website that shows your stove, if you can post a photo of the stove and it's firebox and grate system. Then maybe we can help you easier.

Hope this helps Greg.

.

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Post Sun. Nov. 19, 2006 5:31 pm

Greg, Very informative info,thanks. What was it you did to seal off your grate from the air supply so the grate still operates properly. I don't have a pic and I've got a fire going in there right now so can't measure the grate. Thanks for the help it was informative.

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LsFarm
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Post Sun. Nov. 19, 2006 6:05 pm

Hi Ken, My grate has a raised lip on either side of the grate itself. I think you can see this in the photo below. The lip is actually the angled lower stop or rest for the angled firebrick.

What I did was cut a plate of 1/2" thick steel to rest on the lip and butt up against the firebrick on each side . The first time I made a steel plate to do this job it didn't butt up against the firebrick and one side slid off the lip and onto the grate. Then when I shook the grate, I had a lot of extra weight and friction and the plate eventually developed a large gap at the back of the firebox allowing combustion air a way arround the coal bed.

I don't know if my method will apply at all to the design of your grate and firebox. But the basic idea still applies.

Greg L.
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