Homemade Bit Stoker?

Re: Homemade Bit Stoker?

PostBy: carlherrnstein On: Sat Dec 21, 2013 8:31 pm

I have never worked with aquastats but, I would think they are just a on-off temperature switch. The frequency of the AC probably doesn't matter much unless there are electronics involved. However a higher frequency will make arcing a problem.
carlherrnstein
 
Hot Air Coal Stoker Stove: combustioneer model 77B
Coal Size/Type: pea stoker/Ohio bituminous

Re: Homemade Bit Stoker?

PostBy: unhippy On: Fri Jan 24, 2014 5:53 am

What shape should i machine the inside of the tuyre?......should it be kind of like a trumpet or would a straight cone be suitable ?.....the bottom of the tuyre will have a 1.5" diameter inlet and the top will be about 4" diameter, it will be about 4" from top to bottom

tuyre shapes.gif
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sorry about the crappy drawing but this shows what i mean

the coal i will be burning is a non coking sub-bituminous type with a zero swelling index 8500btu and 4.7% ash and 1340c/2450f ash fusion temp

https://docs.google.com/viewer?a=v&q=ca ... u5Z98dS_3g

Kai Point, its the 5th coal up from the bottom on page 2...... altho its 10 years old that link also shows analysis of pretty much every coal mined in new zealand and most mines are still working the same seams today

sorry about the disjointed post....this week has just plain sucked work hours wise....102hrs when i finished the 7 days....gouging,grinding and welding for all of it.....the next idiot that tries to barrel roll an excavator i talk to with my 10lb sledge' :mad:

cheers for any ideas
Callum
unhippy
 
Stove/Furnace Make: Homemade
Stove/Furnace Model: MK1

Re: Homemade Bit Stoker?

PostBy: carlherrnstein On: Fri Jan 24, 2014 7:27 pm

The prill stoker stoves were built to burn low BTU non-coking sub bituminous coal. If I were building a stoker to burn that coal I would model it after one of those. Heres a link to a thread that shows how the firepot is shaped. Prill underfed stoker
carlherrnstein
 
Hot Air Coal Stoker Stove: combustioneer model 77B
Coal Size/Type: pea stoker/Ohio bituminous


Re: Homemade Bit Stoker?

PostBy: rockwood On: Fri Jan 24, 2014 11:51 pm

That "tuyre" (retort bowl) is quite small compared to that 5 inch auger pipe you mentioned earlier in this thread...you mentioned a bigger "tuyre" at the time as well.
Are you still planning on using that large of an auger?

Are you planning on burning fine coal in this?
rockwood
 
Hot Air Coal Stoker Furnace: Stokermatic coal furnace
Hand Fed Coal Stove: Rockwood Stoveworks Circulator
Baseburners & Antiques: Malleable/Monarch Range
Coal Size/Type: Soft coal: Lump and stoker (slack coal)

Re: Homemade Bit Stoker?

PostBy: unhippy On: Sat Jan 25, 2014 3:16 am

sorry i should have said that i have shelved the big auger and tuyre for a later boiler.....for this stoker stove i'm now making, the auger i have made is 1.5" in diameter hence the 1.5" inlet into the tuyre/retort bowl


the size of coal is 3/32" up to 3/8" and all sizes in between.....the supply of fines coal is a bit eratic so i sized to run on the cheapest reliable size of coal they can supply...... $85/ton pick-up

that prill tuyre looks like it has a straight cone walls rather than rounded walls.....sweet, easier to machine :D

cheers
Callum
unhippy
 
Stove/Furnace Make: Homemade
Stove/Furnace Model: MK1

Re: Homemade Bit Stoker?

PostBy: Lu47Dan On: Sun Feb 16, 2014 11:18 am

Callum, once you get back to the boiler build, think about the running 24VDC for the control system. Sure it adds some complexity to the system but then the arcing problem would be eliminated.
Run the fans, feed motor and other high voltage electrical devices off relays instead of directly off the aquastats. The relays then can be sized for the loads they will encounter in use.
Than you can have replacement relays on hand if something would fail in the middle of the night.
Good luck with your present build.
Dan.
Lu47Dan
 
Hand Fed Coal Stove: Sears circulator air tight stove.
Other Heating: Crown 115,000 BTU oil fired boiler(house) Weil Mclain 150,000BTU oil fired boiler(Shop)

Re: Homemade Bit Stoker?

PostBy: unhippy On: Wed Apr 23, 2014 8:44 am

A DC control system is on the 'future boiler plans' list as of now :D

as for my current build i have the tuyre machined and drilled and the auger tube mounted to the air shroud/plenum, the gearbox ( thats actually 119:1 not 60:1 like it had written on it lol) has been test run with the new 1/4 hp motor i had to get (original motor was 3 phase) and i have a 120 division/3 deg ratchet for the auger drive that should allow me to gear down to 1/10th of an rpm auger speed on one click or 6 rpm if i adjust the throw to maximum.

i splashed out and got a sheet of steel and folded up a stove body, the woodstove conversion idea died a death of looking somewhat uncooth....i did pinch the door off the woodstove before it got scrapped tho.

once i have it built and tested i will post a video or two showing all parts etc....its getting chilly here at night so the enthusiasm for stove building is increasing

Callum
unhippy
 
Stove/Furnace Make: Homemade
Stove/Furnace Model: MK1

Re: Homemade Bit Stoker?

PostBy: unhippy On: Wed May 14, 2014 7:27 am

Have had a major fail with the underfeed stoker.....i put chip coal in and get 100% coal dust at the tuyre....lol i've built the worlds lowest efficiancy coal grinder..... :mad:

i had a talk to a guy that fires a couple of large steam boilers (500hp each) and told him what had happened.....found out they had the same problem a few years back when the mine opened their current pit and closed the old one....they had to completely redesign and rebuilt the feed setup to their boilers because the coal was being ground to dust before it got to the spreader....and when the spreader would throw it into the boiler it was flareing off above the firebed and getting blown into the tubes while still burning.....they had to change all their screw feeds to little belt conveyors all the way from the bunker to were it drops into the spreader/slinger. :(

so all my work in the underfeed stoker is a dead loss

on the up side the same guy thought that a flatbed stoker would work as long as it had secondary air supplied to the flame.....the sub-bit coal i need to use doesn't swell, melt together or do anything silly.....and it has quite a high clinker temperature so he thought that wouldn't be a problem either.

I got a Mellor 1RPM constant duty pellet stove motor and a dayton 49 CFM blower from the "electric motor warehouse" in the US that turned up today so round 2 will be a flatbed stoker with secondary air added....i will see how things go this time
unhippy
 
Stove/Furnace Make: Homemade
Stove/Furnace Model: MK1

Re: Homemade Bit Stoker?

PostBy: carlherrnstein On: Wed May 14, 2014 9:21 pm

Too bad your having problems. My dad tended a winkler stoker that fed a boiler for the farm house for about 60 years. He had to replace the auger a few times because the flights would wear down and the coal would be crushed to a powder by the time it got to the retort. The coal peices would get bound and be crushed.

I wonder if your auger has too much clearance. Also the coal might be getting crushed in the bottom of the retort where it is being forced to change directions.

You might PM fourm member Berlin he knows a lot about soft coal stokers and might be able to offer some advice.

Good luck I hope you dont give up on it just yet it sounds like you have invested a good bit of time into this project.
carlherrnstein
 
Hot Air Coal Stoker Stove: combustioneer model 77B
Coal Size/Type: pea stoker/Ohio bituminous

Re: Homemade Bit Stoker?

PostBy: unhippy On: Thu May 15, 2014 2:27 am

believe me i have tried to get it to work....i have 1mm(40 thou) clearance between my auger tube and the screw and i machined the screw down in the lathe so it would have nice square edges....no dice :x

the problem is with the softness of the coal....or rather how soft it gets when it dries out....as it comes out of the ground it has 30% moisture content, at this moisture content level it works fine in screwsfeeds as its fairly hard....if it was dug out a couple of weeks ago and has been left in the open exposed to the sun and wind and has had time to dry out a bit before i get it, its soft enough that you can break it down to 1/8" pieces in your hand with little effort.....no screw in the world is going to move coal that delicate without munching it up a fair bit.

i need to build something that will work with both fresh coal and older more brittle coal......a carpet bed stoker seems to be the most gentle autofeed so i figure it will have the best chance of working with both types of coal.
unhippy
 
Stove/Furnace Make: Homemade
Stove/Furnace Model: MK1