Has anyone here homebuilt a subBituminous coal stoker?....I'm in the early stages of building my own, and i'm looking for any rules of thumb or the likes that would help in the design...especially how on much air it will need....I'm in New Zealand so getting to have a look at a home heating sized one to shamlessly plagiarize isn't an option so i'm having to pick up ideas off youtube and this forum....
currently i have built a base for the stoker to mount into and the boiler to sit on, have material for the boiler but haven't started it yet, it will be vertical firetube with 16 2 inch tubes with chain turbulators the full length of the tubes, will be hydro tested to 35psi
i have a 4.75" screw/auger and a old 5" hydraulic cylinder barrel with a 5", long-radius weld bend on the end, on top of which my tuyere will be attached...still have to build the air shroud for under the tuyere
Tuyere will be 5" I.D at the bottom with straight sides up to a 1/2" radius out to 6" at the top and will be about 5" deep and is based on a picture of a fines coal stoker tuyere off Kotly.com...lol and they are even nice enough to put up a scale drawing which gives me a rough idea of the air hole centers, sizes and configuration
i know 5" isn't very big but i don't need much more than 30 to 40 thousand BTU
The drive motor/gearbox is a 1/3hp 1440rpm motor with a 60:1 reduction box (still waiting on the gearbox to arrive) that will have a cam and arm setup driving a 1/2" ratchet, with a snap-on 5 deg ratchet it should give me about 1/3 of a turn per minute so i may need to put a belt reduction on the output of the gearbox to the cam arm if it is too fast ....i liked how the EFM ratchet worked and bush engineered it with stuff i can get hold of (this is all built apart from the having the gearbox mounted)
the fan is driven off the rear end of the auger drive motor and is a cage blower that replaces the cooling fan on the motor with the intake being a shroud that pulls air the full length of the motor fins to keep the motor cool...the fan outlet is piped to the air shroud under the tuyere with a gate valve to dump excess air and in doing so control the air pressure under the tuyere (this is still at sketch stage but all material is on hand to build)
Flue will be of 6 inch but haven't got that far yet
My coal hopper is a open top 44 gallon drum with a sealing lid, the bottom will be cut out and a 30deg cone will be installed and feed into the auger( i have the drum but nothing has been cut as yet)
the coal i will be running is 8500btu subBituminous with a zero swell index and in my coal range(cookstove) you have to try damned hard to get a clinker out of it, the ash is a fine powder like some hardwoods produce
control gear will probably consist of a wood boiler draught regulator actuating a magnetic switch to control the stoker on/off...i can't get aquastats etc suitable for boilers here....and the ones from the US don't do so well on 240v 50hz...
i have an over temp control valve that opens at 95C and will dump cold water thru a cooling loop of copper tube in the top of the boiler before going down the drain, it closes when the boiler temp has dropped to 89C
still have to get the pump,pex,manifolds, plate HX for DHW,and thermal balancing valve for control of DHW, from overseas but i have the radiators locally...salvaged from a school that was pulled down
So...anyone see any truck sized holes in my boiler setup?