What do I need to know about solid fuel?

[jtcedinburgh]

My Morso Owl stove is multi-fuel, and I want to try some solid fuel (not house coal) in it to see how that goes for getting a decent amount of heat into the wee hours.

What do I need to know about?

Specifically, can I chuck some smokeless briquettes on top of my wood coals at the end of the night - will that work, and would I need to change to primary air (from below) as opposed to secondary air (from above)?

Also, if I only use a little at the end of each evening, will this mean that I need to get the flue cleaned more regularly, or is that only if I burn more?

Do I need to clean the solid fuel debris from the stove before lighting the next wood fire?

Basically what I'm looking for is the low-down on using wood AND solid fuel...

 

[Andre B.]

????????????
Wood is a solid fuel.
_________
Andre' B.

 

[jtcedinburgh]

You know what I mean :D

I'm talking about smokeless coal briquettes...

 

[wg_bent]

Hey JT, actually, I'd guess very few folks here in the states did know what you meant by solid fuel. I didn't either.

I guessed you were talking about coal, but then you said "not coal". So I figured you meant peat briquettes....but you said charcoal brickettes. Is that like what you use for the bbq?

Seriously, I'm not sure what that stuff is, since I'm not aware of it being available here.

What does the "debris" look like? If I burn charcoal briquettes for cooking a steak, there's nothing left but some ash that looks similar to the ash left over from a wood fire.

 

[berlin]

you should definately run more underfire air, also if it is a true smokeless fuel for use in smoke controll areas, you should have to clean your chimney less than with wood, those compacted coke briquettes burn very clean. btw, for those interested, in the uk
"house coal" means bituminous, which along with wood, unless burned in an aproved appliance is not for use in "smoke controll" areas, however there are various anthricites- smokeless coals mostly from wales and the continent that are approved for use in these areas as well as various manufactured smokeless fuels such as coke from coal, compacted or not, compacted anthricite culm etc. and the newest thing is petrolium coke which can be made into briquettes as well. these are not the same as "kingsford" charcoal but may appear similar.

 

[jtcedinburgh]

yeah, sorry, I should have explained myself a bit better. I was meaning the kind of smokeless coal that's approved for use in smokeless zones here in the UK.

Some further questions if I might?

(1) Is the sulphuric acid content in regular coal present in the smokeless, compacted briquette variety?
(2) How many briquettes would be sufficient to keep enough heat going to last say 6 hours?
(3) With these smokeless coal briquettes, do I need to clean out the 'debris' (ash/muck/dust/whatever you call whatever remains after burning) or can I just riddle the excess like I do with hardwood logs?
(4) Given the objective here is a longer burn, is throwing some smokeless briquettes atop the glowing embers of a wood fire going to increase the burn longer than reloading with logs?

I'm tempted to try this tonight - I can get some from a local petrol station (probably paying over the odds, but then it is an experiment) and I figure that one evening's burn won't really make so much of a difference to flue cleanliness...

 

[begreen]

JC, you may be educating us on this. These are good questions, but may need to be asked on your side of the pond. I would experiment. And ask the place you bought the stove from. If it were me I would experiment during the daytime or on a weekend. Otherwise you may be up all night wondering how the fire is doing.

 

[wg_bent]

When you try it and get the results...let us know what happens. As I tell my oldest kid...Your the experiment.

 

[jtcedinburgh]

Well, I tried it - last night, got the stove up to temperature using logs in the conventional way and let it burn down to red hot coals. Then I placed seven or eight smokeless briquettes evenly into the wood coals. I damped down the air from above and opened the air from below, and these thumb-length, oval smokeless briquettes quickly started to take.

Within around ten minutes I was able to reduce the air from below to approx. 1/4 open (and for good measure I opened the air from above to approx. 1/8 open just on a whim). By this time the central coals (over the vents) were turning yellow/red, and had a small amount of slightly red coloured flame. I couldn't see any smoke or vapours, but I soon noticed some fogging of the glass, which I reckon could be attributed to closing down the airwash.

I then retired to bed (approx. 11pm) and woke up just before 6am. At around 6.10am I had to have a look. The stove was still appreciably warm (whereas it would have been cold to the touch had I used logs) and a bit of poking with the poker revealed the coals to have red hot cores - most of the coals had turned to a light, powdery ash/dust, but had held the briquette shape. The hot centres were hot enough to start a couple of bits of kindling (with maximum air) from which I managed to get a few splits going before I had to head off for work at 6.40am.

So, a success of sorts. Next time I may try more briquettes - perhaps 8 is not enough? - but at least there is enough to actually get an overnight burn, even if I reckon I was on the cusp of losing the core heat after 7 hours.

Downsides? Well, there's more ash per unit volume than with wood, though the overall volume of briquettes was considerably less than with logs, so I reckon 8 briquettes produces 2/3 of the ash of 3-4Kg of logs. It seems fairly benign stuff, not noticeably different to potash, so perhaps the cleaning out after each fire thing I'd heard only applies to conventional house coal?

Upsides? Well, I can overnight burn now, and I'd swear the heat output from 8 briquettes is not far short of that from considerably more hardwood logs.

Anyone else tried this?

 

[begreen]

Thanks for the update JC. I haven't seen anything like that around here. But is sounds like you may have a solution for the stove. That's got to be way less expensive than moving the stove and buying another one.

I did a little searching and find there is a lot of info on the web in Europe about these briquettes. You have a lot of choices in brands and even what the briquettes are made from. I found peat, cabonized waste, cabonized coal + biomass for sale. Because of the wide variety of sources, the emissions will vary with the briquette components. Most of the information is about manufacturing, some of it quite interesting. Poland is doing a lot of research on them.:

Home Stoves

The coal stove tested during this program is a traditional storage stove built of brick and covered with ornate ceramic tiles. It has been reported that there are seven million such stoves in Poland. These stoves are fired once or twice daily during Winter. Each firing period lasts about 1 1/2 hours, and during this time the stove's mass is heated. After the burning period is over, the room is heated as the masonry slowly cools.

Testing was done at the Academy of Mining and Metallurgy (AGH) in Kraków with a test stove built in place by local craftsmen. The test protocol used was based on U.S. standard methods for testing wood stoves and allowed continuous measurement of emissions and efficiency during burn cycles.

A range of fuels were tested, including coal typically used (10-20% ash, 30% volatiles) and low volatile, smokeless briquettes. The briquettes are being considered for future use and are not yet available on the fuel market. In tests with normal operating procedures, thermal efficiency of the stoves was found to be considerably higher than expected (60-70%). Emission factors for particulates were found to be very high with coal firing. With the low volatile briquettes, particulates were reduced by more than an order of magnitude. Similar results were obtained with use of low volatile coke.

The work at AGH included tests with a wide range of operating conditions. During the course of this work a new operating procedure was developed which can produce efficiency levels of 72-75% consistently.

Links:
http://www.serina.es/escaparate/verproducto.cgi?idproducto=4921&refcompra=NULO
http://www.geocities.com/envirocharcoal/
http://www.stovesonline.co.uk/smokeless_fuels.html
http://www.bnm.ie/downloads/peat_for_domestic_heating.pdf

 

[jtcedinburgh]

Thanks for that. I am 99% certain that the fuel I am using is the CPL 'Homefire Ovals' - which I am looking forward to using again tonight later on (after I've had my woodburning fix!)

My only small worry about all of this is not knowing how much and what type of nasties it's putting 'up the lum' (as we say around here) - I've read about sulphuric acid content in coal, which can't be good for a steel liner...

john

 

[begreen]

I read that they gasify and collect a lot of the sulfur during the coal charring process. Here's a doc straight from Glasgow that lists percentages of sulfur. Homefires must be less than 2% sulfur. There are other brands that are less than .5% if you are concerned, but I suspect with a good stainless liner you'll be ok. How long have these briquettes been on the market in Scotland? Long enough for sweeps to notice problems if any? (Other than a lot less business.)

http://www.opsi.gov.uk/legislation/scotland/ssi2001/20010433.htm