Brick Oven - convert from wood to coal

Brick Oven - convert from wood to coal

PostBy: willclarke On: Fri Aug 07, 2009 8:30 am

Good morning. I’m bringing another brick oven topic to the forum. I’ve just joined the forum last night and I’m new to coal firing. I was reading the response to Coalpit’s ( Nick’s) posting and everyone on the forum was certainly very helpful with Nick and his brick oven topic.
I built an outdoor barbeque area with a brick oven. See the pictures attached. I built the oven as a wood fired “black” oven, which means the fire is in the same chamber as the cooking area. I built the oven in April this year. The oven works great with wood, with temperatures reaching 1000 in 3 hours.
My problem began last month when my neighbor was diagnosed with esophagus cancer. My neighbor cannot be exposed to any smoke. My oven creates an enormous amount of smoke during the first 2 hours of firing it with wood. So in consideration of my neighbor, I need to figure out a way to use my oven without creating much smoke.
I was considering using coal, and my questions are concerning how to burn it in the chamber. With wood, I would just burn the fire on the right side of the chamber, right on the hearth. Will coal burn if it is just sitting on the hearth, without a grate, without mechanical ventilation? I can place a gas torch next to the coal to get the coal ignited…. Any ideas or suggestions?

More oven specs:
interior is 36" x 60"
oven arch is 18" high
oven doorway is 10" high, 16" wide
The only vent to the oven is the doorway. Intake enters in the lower portion of the doorway and the exhaust leaves at the top of the doorway and goes up the chimney.
Oven 18.JPG
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Stove/Furnace Make: Custom - Brick
Stove/Furnace Model: Custom - Brick

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Re: Brick Oven - convert from wood to coal

PostBy: CapeCoaler On: Fri Aug 07, 2009 8:55 am

Nice work!
Is the neighbor's house seen behind your oven?
Coal wants air from under the fire.
How about a taller chimney or adding a blower.
The smoke is from a fire that is lacking enough air.
When we last had a hurricane all the blow downs were burned at the dump...
to get past the EPA and neighbors about the smoke...
Huge fans were setup on the sides to introduce excess air to the fire pit.
The result was a quick hot fire with little smoke.
They burned for 4 or 5 days with no complaints!
I would start with a fan and a metal pipe into the wood fire and see if you can cut the smoke during startup.
Stoker Coal Boiler: want AA130
Hand Fed Coal Stove: DS Machine BS#4, Harman MKII, Hitzer 503,...
Coal Size/Type: Pea/Nut/Stove

Re: Brick Oven - convert from wood to coal

PostBy: Richard S. On: Fri Aug 07, 2009 12:14 pm

Damn, nice oven!

You need a grate with underneath air, here's what the EFM coal/wood boiler looks like and this would be similar to most hand fired stoves:

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The bottom:
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What you should note about this is all the air comes from underneath and the steep almost completely vertical sides. Without a similar design you're going to have trouble. The grate assembly or similar assembly could probably be purchased through an EFM dealer or someone else. You will still be able to burn wood in it too.

See here for more info on this boiler: The efm WCB-24 hand fired wood/coal boiler
Richard S.
Stoker Coal Boiler: Van Wert VA1200
Coal Size/Type: Buckwheat/Anthracite

Re: Brick Oven - convert from wood to coal

PostBy: willclarke On: Mon Aug 10, 2009 9:13 am

Thank you for the responses. The house seen in the picture is my house. My neighbor's house is 100' to the left of the oven. I contacted a couple of local coal suppliers and I plan to pick up a couple of bags of nut coal to try out. I've started working on a pipe to feed air underneath the coal as it burns. I'm trying to avoid any major changes to the oven if possible. I"ll be firing it up on Thursday so I will let you how it works.

Thanks again.
Stove/Furnace Make: Custom - Brick
Stove/Furnace Model: Custom - Brick

Re: Brick Oven - convert from wood to coal

PostBy: franco b On: Wed Aug 12, 2009 1:43 pm

Beautiful masonry work.

I would stick with wood and just take measures to burn cleaner. Coal would require too many difficult alterations and would have to be started with wood anyway. Coal wold take hours to establish itself and there might not be sufficient draft with that short chimney which is probably over size for a coal fire. There would be trouble getting it lit and even when you do it might then want to burn far longer than you want it to.

A clean fire means mixing air with the fuel in such a way that no part starves for air causing smoke. It also means having enough heat to ignite the smoke, which requires a fire chamber small enough to accomplish this without dissipating the heat. This is why well designed heating boilers and furnaces separate the burning function from the heat exchange function. As has been suggested you can try forced air, but that means electricity and further complication.

A simple inexpensive thing you can try is to use a fire basket to hold the wood, such as is used in fireplaces. This will hold the wood up off the floor of the hearth and provide for better air circulation. Start with a small fire and gradually build up as the mass of brick gets hot and draft is established. Once all that masonry gets hot it will burn clean.

Another thing to try would be to start with charcoal, again in a basket, and add wood once the heat is up. Any thing you can do to aid draft such as extending the chimney with metal or terracotta pipe will also help.

There is no way you are going to get a smokeless fire until heat is high enough in that enormous mass, but you can improve things. Also avoid starting a fire in low draft atmospheric conditions such as hot humid days where everything just hangs.

With your obvious talent for brick work you might also consider building what is known as a Russian fireplace inside your house using plans that are known to work well.

franco b
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Brick Oven - convert from wood to coal

PostBy: SSB On: Sat Aug 29, 2009 11:48 am

You can do it but you're going to have to cut apart that floor.

I just did it with mine. Originally built to burn just wood. After I finished the dome and made a few wood fired pizzas I decided coal would be a good option too. I basically had to cut a hole in the floor, make a shaker grate system out of rebar and cast iron grill grates and slide the whole thing in. I'm not going to lie ... it was a royal pain in the ass. I spent many hours with the top half of me crammed in the oven amdist hammers, chisels, and dust spewing power tools.

To deal with the fact that the front opening is too large and cuts down on the heating efficiency I block up all but the few top inches of the inner arch with firebrick when burning coal. I have to remove it every time I want to add or remove food. For the short time there's a pizza in there I leave it full open. It's temporary. Once I build the door and size it so it fits just inside the outer arch I'm going to put a damper in the vent to control the heat loss.

It gets started with charcoal then coal on top. Very little smoke. The charcoal starting is the worst part. When I'm impatient I run a small blower forcing air up under the coal and it brings everything up to temp quicker. Still not as fast as a good roaring hardwood fire though.

I'll take pics and post so you can see what I mean.
Stove/Furnace Make: Crane Coal Cooker Model 44
Stove/Furnace Model: Homebuilt Brick Oven

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