Sub-Bituminous, underfeed stoker, warmer weather transition

Sub-Bituminous, underfeed stoker, warmer weather transition

PostBy: Short Bus On: Sun Apr 10, 2011 2:43 am

Burning Sub-Biuminous C coal in a Anchor underfeed stoker.
In the winter the circulation pump rarely turns off and I'm making nice clinckers, pulling them twice a day and filling hopper with coal twice a day, could probalby streach to 24 hours but why.
The weather has warmed, spring is in the air, 38 F during the day and 10 F at night, circulation pump seams to be off all day, solar heat gain and 50% slab heat, tending boiler once a day.
Clinckers seam to grow vertically out of the ash, and don't seam to absorb the ash as well as in the winter, the problem is the ash is now filling my combustion chamber.
Is it time to adjust coal feed rate and air to get longer run times with hopes of hotter fires that melt the ash better.
I will start experimenting soon, summer is coming and I anticipate this problem will only get worse, I will be burning all summer as I now have an indirect hot water heater.
Monthly average low temperatures are only above freezing three months here, so keeping the boiler running thought the summer for the hot water is not a big deal.
My boiler controls turn the stoker on at about 160 off at about 180 when there is call for heat, and a low temperature cut out for the circulation pump at 140 to prevent condensation, this low temperature cut out also starts the stoker. I installed a relay to latch the stoker on, any time it starts, until the high temp cut out at 180 shuts it off, to lengthen run times.
This coal and stoker combination seams to hold fire well, it can be unplugged for at least twentyfour hours and still fire up, so no hold fire timer.

Question, Will adjusting my feed rate from maximum and adjusting the air get a longer burn times and hotter smaller fire that will clincker better and ash less?

I will be experimenting but thought some advice may be helpfull.
Oil is getting to 5$ a gallon here and people are starting to ask me questions, the three Outdoor hand fed Wood/Coal boilers in town have basically disapointed, in my opinion.
Short Bus
 
Stoker Coal Boiler: Kewanee boiler with Anchor stoker
Coal Size/Type: Chestnut / Sub-bituminous C
Other Heating: Propane wall furnace back up only

Re: Sub-Bituminous, underfeed stoker, warmer weather transition

PostBy: rockwood On: Sun Apr 10, 2011 9:43 pm

How long would you say the stoker runs when there's a call for heat with current weather conditions? If your boiler is insulated now, I don't think the stoker will run much at all during the summer because the idling coal fire will keep things hot if you're only heating domestic water. Adjusting temperatures on boiler to get longer stoker run time and not adjusting stoker settings I think would be best to try first. Is the fire burning down low into the retort bowl now? You might just have to deal with more ash during summer which isn't optimum for your stoker set-up but will be ok.
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: Sub-Bituminous, underfeed stoker, warmer weather transition

PostBy: Short Bus On: Sun Apr 10, 2011 10:46 pm

Boiler is insulated.
Unfortuantly I have a Honywell L8148A controler with a L6006 Low limit controler. With the L8148A the differental is not adjustable, only the range it operates in.
I pulled clinker this morning, and again this evening, hoping this will cut down on the ash, and increase the clinkers.
I'm not sure where the fire is now but the clinkers somtimes come out with a dome shape about the diameter of the twyeres.
Still down to the single digets last night.

I also don't like the Idea of changing the belt and air adjustment, this setting has changed my world from ash all winter to clinkers for the driveway.

I don't have an idle fire timer since my fire will stay lit 24 hours without running, fire seams to disapear into the retort, and you can put your hand above the center of the retort without sensing heat.
Short Bus
 
Stoker Coal Boiler: Kewanee boiler with Anchor stoker
Coal Size/Type: Chestnut / Sub-bituminous C
Other Heating: Propane wall furnace back up only


Re: Sub-Bituminous, underfeed stoker, warmer weather transition

PostBy: europachris On: Mon Apr 11, 2011 12:09 pm

I've read where summer or early/late season operation of clinkering style stokers will not provide hot enough fuel bed conditions to fully clinker all the ash, so some loose ash shoveling will be required. However, at the same time, the coal consumption rates drop off enough to where you only may have to do that once a week.
europachris
 
Stove/Furnace Make: EFM 350/Iron Fireman
Stove/Furnace Model: Custom bituminous burner

Re: Sub-Bituminous, underfeed stoker, warmer weather transition

PostBy: Berlin On: Mon Apr 11, 2011 9:28 pm

europachris is right, sometimes with a higher AFT coal, you will have loose ash in the shoulder season/summer but usually the demand will be so low that it doesn't mean you have to remove it often. Two things that will help having an idle timer and increasing the differential on the aquastat to obtain longer run times and larger swings in boiler temp. Although you don't have that capability a generic idle timer and a different aquastat are redily available online at grainger etc.
Berlin
 
Hot Air Coal Stoker Furnace: Will-Burt Combustioneer 77B
Coal Size/Type: Ohio BITUMINOUS pea stoker coal