Bituminous Boiler Plan

Hi folks:

I just saw your site perusing the web on coal related topics. I've got a very large antique colonial house with garage and workshops in the suburbs of Boston. After reading about how much money one can save from switching to solid fuel, I'm ready to make the move. Current gas bills run $6000 per year and I also attend vintage steam events so love the smell of bituminous coal. Like others have found, the delivered cost of good anthracite around here is too high. It's like buying cordwood, $300 plus per ton. So, after doing some research, I realized I could get a 20 ton dump trailer full of high quality bituminous with the same BTU yield for around $120 - $130 a ton buying it direct from the mine and trucking it up myself. The other thing I realized is that continous burning in a central boiler (I have hot water heat) is not practical with the irregularity of heating demand and the inefficiency of the fire smouldering during slack times.

So my plan is to build a giant heat storage tank in the basement of a new family room wing. The basement will house the boiler, storage tank, and fuel. The storage tank will be built into the the basement walls out of reinforced concrete, holding 8000 gallons of water. Inside the concrete retaining walls, is foot thick polyurethane foam insulation and the inner liner will be a high temperature rubber bladder supported by plywood on 2x12's connected to the concrete outer walls. The plan is to have this tank hold 2 million BTU's of usable, on demand heat, at a temperature range of 150 - 200 degrees. Rather than have a small boiler heat this tank running virtually all the time, necessitating stoking at all hours of the day, I got hold of a surplus, industrial boiler for free that will generate around 600 - 700k BTU"S using hand fired bituminous. My thought is that 3-5 hours of running that boiler every other day, daily in the cold months, is much easier than keeping something small going. I saw how quick one can light a locomotive using kerosene soaked hardwood kindling, it took less than an hour to be at full temperature.

I'm looking for ideas on grates. The boiler is in excellent condition but it was converted to oil so I'm designing the combustion chamber from scratch. My welder friend and I plan to construct a deep base, giving around 9 - 10 sf. of grate. Boiler can accomodate 12 sf. but I think that's too much. I then plan to use two forced draft fans, one under the fire, the other for over fire secondary combustion, each will be completely separately controlled and will pipe the air through a preheater before it hits the fire. The entire firebox will be completely lined with high density firebrick. For the grate, I obviously need some ash removal facility plus I want to be able to burn a variety of coal sizes easily as well as wood sometimes. We'll have the base completely airtight, and put in a drawer to pull out the ashes. On the exhaust side, I'm using a high temperature (800 degree rated) industrial, centrifugal exhaust fan, to push the flue gas up a 12 inch stack very rapidly and hopefully avoid soot settling over my house. It's going to be a smooth, round, stainless lined flue as part of a large, multi flue chimney and will project 6 feet above the roof ridge. The plan is to balance the draft with a draft controller so the whole boiler is slightly negative at all times.

Please share your thoughts on grate designs, ash removal, and fly ash removal prior to the flue gas hitting the stack.

All I can say to start with is WOW , that's a plan!

First question - how large is the house? What is the current heating demand? What will the addition add?

If you were me, I would seriously consider going with a stoker on that boiler and ditch the entire storage idea. Will-Burt makes stokers that could likely be installed in that boiler (you would need probably the S50 model http://will-burt.com/stkComLight.asp), but that depends on the heating load. If you go down to the Will-Burt Stoker Info thread in this forum, you'll find some info on stokers, boilers, etc. A stoker will idle down to a very low fire rate and be totally automatic except for filling the hopper and cleaning the fire.

The only catch is that the bituminous coal closest to you (West Virginia, West PA, etc.) is very high quality, but lousy for underfed stokers. Those coals swell and coke like crazy, and can be hard to burn in an underfed unit without making "coke trees". The "lousy" coal we have out here in the Illinois/Indiana area is much more suited to these stokers as it has a low (under 4) swelling index, and the high volatile content doesn't pose a problem in a stoker as it does in a hand (batch) feed furnace.

Sounds like an huge project, one thing I will mention is a anthracite stoker is quite efficient while idling along. We burn approximately 1 ton between May and August. That's a little over 15 pounds a day and I've seen others post even less. We keep it going for two reasons. It provides domestic hot water so its saving us money and secondly a stoker should be run year round if possible because it will add considerable life to the unit. This does not apply to the smaller stokers.

I understand you want to go with Bit. I'm not familiar with Bit. stokers or even if they exist or if you could apply the above information to them.

Good, luck and keep us informed, lots of projects like this going on from other members and I myself enjoy to see the progress and conclusion.

go with a bituminous underfeed auto stoker from wil-burt. it will be by far the best most efficient setup. thermal cycling a boiler that big like you plan to do will likely lead to very very premature failure; and starting a huge bituminous fire every day will lead to a daily smokey inefficient mess; I know I've seen powerplant restarts hundreds of times which will be closer to what you're going to be starting everyday(600,000+ btu's!) than a small coalstove. go with an underfed stoker fired into a burnham commercial boiler, and you'll be very happy.

where are you trucking the bituminous coal from?.........we just paid 135 a ton for anthracite

You may want to check the cost of anthracite outside the area lincolnmania, it gets quite expensive.

But DavidW said he was going to truck it himself, the anthracite is much closer to Boston than the Bituminous, and much less of a hassle.

Hi David W: I'd look into the cost difference with the added construction you are contemplating. A good EFM or AA/AHS or Keystoker boiler will do the job for you and be virtually painless. I'd very seriously look into the five year cost of the two different coals.

Or go with the underfeed bituminous stoker instead of a hand feed..

My father and I made a home in central Michigan with huge water storage tanks to collect and hold solar heated water. Neat idea, worked for a while. Your tank design might work better than ours. We didn't have access to a bladder.

Berlin has it right, starting a big bituminous fire every other day will bring 'clean air' folks down on you and be a real pain. The underfeed stokers pretty much eliminate most of the soot and smoke. Just lots of coke, coke trees, and clinker to remove.

I've burned them both, anthracite is a lot further for me to go after, and drag home, but I prefer it to bituminous..

Greg L

Thanks for the comments so far. Some thoughts: The reasons I want to keep my boiler hand fired are several. Fuel flexibility: I want to be able to burn as wide an array of types and sizes of coal as possible, including anthracite, if I can make the numbers work. Your comments on the need for certain types of bituminous to make underfed stokers run properly reinforces this decision. And units like the EFM, would completely lock me in to one type and grade of anthracite, fine if I lived down the street from the mine! I also want to keep my options open for burning wood. I will occasionally get free wood that I will burn. A stoker eliminates that possibility. The other consideration is simplicity. Stokers seem finicky and will break and clog. The only moving parts in my design will be the blower fans and the recirculating pumps. I am interested in hearing about the effects of thermal shocks on welded steel boilers. Obviously, if it was run every other day, the boiler shell would go from room temperature to 200 degrees and back, is that harmful? Also, I could keep the shell at 150 degrees minimum by keeping the recirculator pump going all winter, in essence limiting the range from 150 - 200 degrees, is there a thermal shock issue with the grate and firebrick? As far as smoke upon startup, I plan on very carefully stoking the fire and the secondary air fan should ensure reasonably clean combustion. Also, I'm only going to light the bituminous at night, so any cloud will be less noticeable, during daytime, I'd probably burn wood or anthracite if I had to. The way I look at it, I'm going to burn around 250 lbs of coal every couple days. It would be far easier to burn that over 4 hours than spread it out over 48 and have to tend it. The fire, once going, would be running full tilt until I let it go out, so would be very efficient.

If you plan on making that many BTUs, then you will be burning 250# every 24 hours or less. When I was handfeeding my 'Big Bertha' stove I was going through more than 300# of bituminous or anthracite per day.

The Iron Fireman underfeed stoker I have feeds rice, buckwheat or pea size anthracite,as well as 'stoker' bituminous. So you aren't limited to just once size. The Willburt is the modern version of the IronFireman stoker.

I have the stoker set up on rollers, I can roll it out and convert my boiler back to a hand feed in about 20 minutes. You may be able to do the same.

I'm not selling stokers , I've just gone through the loading and feeding of a hungry boiler before.

One thing you mentioned is the variability of bituminous coal quality, and burning characteristics. You will really see the differences when you burn large quantities of coal. The swelling, high ash content, and bridging over of the fire, all make bituminous a bit of a challenge instead of with anthracite, just load, shake, empty the ash pan.

I like your ideas of storing the hot water, I'm just in the belief that you will save enough money to offset the expense of building the tanks and plumbing the system No question that if you can heat and store the water effectively, it should be pretty effecient.

Greg L

300 lbs of bituminous coal a day is around 2.5 - 3 million BTU's a day net. I will only need 1 million to 2 million to heat my house. What was the consumption rate of your big bertha running full tilt? I think you may be right about the cost recovery on my storage tank idea. I'm going to do it anyway because I like the engineering challenge and I really want a miniature industrial setup. I know a small home size boiler would probably do the trick but it wouldn't be as interesting to run. The thought of the stoker on rollers is very intriguing, I didn't know that was possible. It still would be a big production to switch fuels and would require everything to cool down. As I'm reading here, even with stokers, you have to get the coal to the stoker. Why not just shove it in the boiler yourself. Think of all that tonnage of locomotive fuel that was hand shoveled over the years. I'm a nostalgic old steam buff but this system will be a mix of old and new tech. I'm interested in designing a fly ash separator to be placed inline between the boiler and the induced draft fan. It could also serve as the air preheater too. I would think you'd want to remove the ash before it gets to the fan to prolong the fan life and the gas would be cooler going into the fan enhancing efficiency.

If you want the challenge, then go for it!! It will be a doozey of a challenge! . I was just sharing my experiences, didn't want you to have erroneous information.

The problem with boilers, especially bituminous boilers, is that they aren't very effecient, about 50% after a week of burning and the surfaces get insulated by the soot throughout the heat exchanger. Make sure you have in your plan to open all the cleanout doors and vacuum/sweep the surfaces of the heat exchanger every week.

My boiler would get by on 200# for a few days, then gradually work up to more than 300 to keep the water at 150*, then I'd have to wheel out the stoker [just shut it off, the fire goes out in an hour or so with no air] The open the clean out doors and scrape the soot and vacuum it up. then back to the same process for the next week or two.

With anthracite there is fly ash, it is heavy, and settles on lower surfaces and if adheres to vertical surfaces, it falls off after it gets to a certain thickness, sort of self cleaning.

Switching fuels is easy, just add what you want to the coal feed hopper. not a big deal at all. And shoveling coal into the firebox is tougher than dumping it into the feed hopper with either an auger or 5 gal. buckets. I can wheel out my stoker, reinstall the hand fire grates, and have it ready to start a hand load fire in about 20 minutes. No need to let it cool, or worry about the fire in the stoker's firepot, it is going out, no air, just glowing embers for less than an hour.

As for hand loading bituminous: When you toss fresh bituminous on a fire, the volitiles immediately start to gass off, and unless you have a draft like .1-.2, you will get the black soot back in your face and into the room. You would have to make a conveyor to feed the fire with hot oxygen rich air blown into the volitiles to burn them off as the fresh coal is fed to the fire... an interesting challenge.
What I did was to open up the air supply, get the chimney really drawing, have 2-3 buckets of bitum coal at the ready. Shake down the fire, inspect it to make sure it was nice and hot. Then toss on the 100+ # of coal, and close the door QUICK !! Because the coal was going to gass off real quick. I also had to learn to leave a corner of the fire open, I used a garden hoe to open the fresh coal up down to the hot coals, otherwise the volitiles would build up, with not enough heat or an open flame to ignite them, Then the whole boiler would fill up with volitiles, and when the ignition finally occured, it would be spectacular,,, It kept my chimney clean !! looked like a Locomotive! and it also blew the flue pipes off a couple of times. Not a good thing... I had to powerwash the interior of my boiler building the next summer !!

From my perspective, I'd use the old boiler [sounds neat, and capable] and adapt an underfeed stoker, on wheels, so you could pull it out to service, clean or convert to hand feed. Then see how much heat you can make, and see about storing it.. A series of 250 gallon tanks plumbed in series as a storage unit, heating the basement would work. And prove the theory of heat storage without building the addition to the house with the built in tanks untill it is a proved setup.

My Dad and I spent a lot of time and effort on our heat storage system, but upkeep became too much work, we put in a wood burning hot air furnace... later propane, then we installed a new owner for the 'vacation house'.

A bit of learned knowledge about bituminous coal. It is sold usually two ways, 'run of the mine' and nut or stoker. The nut or stoker is washed, or sorted by size and is roughlly like pea to nut anthracite. With not very many fines in the coal. The 'run of the mine' is the coal just as it comes out of the mine, huge chunks like basket balls down to LOTS of powder-like fines. The fines are a disaster. The combustion air cannot get up through the fines, so they choke off a fire, get hot, swell, stick together into a gooey lump and make a bridge over the fire, often even putting out the fire. You have to go in after an hour and break up a bituminous fire, it has welded the pieces together into one sheet of coal, that is not burning well, there are few air passageways through the big lump of stuck together coal pieces. So you have to use a 'railroad bar' to jab at the big lump and break it up into smaller lumps so it will burn and not bridge/smother the fire below.

So if you go with a truck to buy bituminous PAY THE EXTRA for sized washed stoker or nut coal DON'T buy the run of the mine... like I did the first time..

The Beauty of anthracite is that each piece of coal stays independant from the next, and does not stick together, and will burn down to ash with little if any tending in a properly designed firebox [vertical sides, grates all across the entire floor of the firebox.].

Ok, by fingers are tired, and my coffee is cold. gotta get something done..

I've attached a few photos, I think they are on the forum somewhere.

LSfarm, you are most gracious to share your experiences. Everything you've said makes perfect sense. First of all, the addition is getting built anyway, so I'm not adding to my house just to house the giant storage tank. I know from reading extensively on the subject, with geothermal and solar collectors, that a super insulated cube of water, will only lose like a 1/2 degree of water per hour, so all of my output will be stored and released through my radiators. Any excess heat from the tank and the boiler itself will be directed back into the house. Regarding soot and draft, I knew immediately that if I wanted to burn bituminous coal, natural draft wasn't going to work. So, with that in mind, I've designed three fans. One to feed air under the grates, another to supply preheated over fire air to burn off the volatiles like you said, and a really big one to suck the flue gases out of the boiler and push them rapidly up the chimney. My coal burning experience to date is with anthracite in a heater stove, and bituminous in a blacksmithing forge. I know about breaking up the clumps and keeping ignition points within the fire. My scavenging fan will easily create massive draft to ensure any smoke is sucked up the flue and not escaping into my house. I will increase the draft just prior to tending the fire for that purpose. I think I will proceed with my hand fired plan since it is simple and cheap. If heaving the buckets in the fire and raking it out prove a problem, I can always buy a stoker and fit it like yours. I really like the idea of burning wood too, so that also makes grates more attractive. Your furnace looks interesting. Mine is an old style but modern welded ASME unit that you'd see in an apartment building or greenhouse. It's roughly 3 1/2 feet wide, 4 1/2 feet deep, and seven feet tall. Holds 280 gallons in hot water trim.

Your boiler is a monster - 1MBTU Gross output and supports up to 100lbs./hr coal firing rate. 20" smokepipe outlet and it weighs just shy of 4000# empty (5150# in hand firing trim). Over 12sq.ft. of grate area to fire.....

I've been developing my future bituminuous burning plans around the 4N-63 boiler and the Will-Burt S30 stoker, and that's still a sizeable setup.

That will be an impressive setup when finished.

David thats a pretty good idea to reclaim that piece of machinery, Unfortunately you will have alot of problem burning wood. I did the exact same thing and when all was said and done ended up with an efm.The problem being extensive creosote buildup. Buildup not causd by green wood, not caused by insufficient draft, but caused by the boiler walls never really warming up enough to prevent the oil (creosote) from plating out. Creosote problem of epic proportions. It happened in mine with 2 year seasoned oak. Dry as tinder. Can't imagine what would happen if you burned some hot coal after a period of burning wood. Sounds like a recipe fora disaster. Soot would be sort of the same. It seems that the most condensation occurred when the boiler was in it's initial warm up . The stuff would run out like a faucet until the water warmed to 200 degrees. If you put a underfeed stoker in 275 gallons of water would be easy to regulate with a simple aqustat setup. Then again, my 600 gallons wood stay hot for several days before the oilfired would kick in.
For wood I can definely say that your going somewhere bad. Coal is something else that I wood defer to someone more experienced than I. Good luck with your project. Scott