Multi-fuel boiler?

[Wearyman]

On one occsion (each) the owner forgot the steam valve was on, the tank overheated, the tank's safety lifted and dumped propane gas in the bilge where the burner promptly lit it off. OPERATOR error.

I do hope that nobody was seriously injured! Although with a bilge full of flammable gas I can't imagine that the operator escaped without some injury.

[artemis]

On one occsion (each) the owner forgot the steam valve was on, the tank overheated, the tank's safety lifted and dumped propane gas in the bilge where the burner promptly lit it off. OPERATOR error.

I do hope that nobody was seriously injured! Although with a bilge full of flammable gas I can't imagine that the operator escaped without some injury.

Fortunately no one was seriously injured in either case. In one the two persons aboard were both wearing lifejackets (good reason to always wear one ), promptly jumped overboard and a nearby boat picked them up and caught the boat before it was serriously damaged; in the other the owner and guests had just left the boat and were a short distance up the dock.

[87gn@tahoe]

On my father's boat the firebox door (Semple VFT40) has been modified so a portion is permanently closed and mounts a "williams" burner, the other side of the door still opens so that we may add wood (or other flamamble objects) for cold steamup, or for a "pilot light" for the burner. The boiler is a bit too small for the engine and the grate area is too small to be burning solid fuel and keep up with demand. Approx 2-3 gal/hr of straight used motor oil.

Wearyman, steam powerplants have MUCH less thermal effeciency than I think you are giving them credit for.

On my boat with it's "high effeciency" monotube boiler, I burn about 1-1/2 gallons of Kerosene an hour for a 7ish HP plant. (At 9mph it's almost the same fuel mileage as my dad's '77 Ford f250 with an "air brake" camper and a 460ci V8 at 70mph )

If you are going to be burning solid fuel, you will want a large grate area... I'm not sure on the rule of thumb for SqFt of grate area per HP.

I have seen guys use 5gal propane tanks to start the steaming process until they at least had enough steam to start their atomizing burners, then they would leave the propane tank on the dock. I personally wouldn't cary propane on a boat unless it was in an elevated and well ventilated position.

I don't know if it is true or not, but I have heard that the smell of propane is supposedly an added chemical that just happens to be water soluble.. meaning if you have water in your bilge, it is likely that you will be unable to smell if you have a leak until it's too late.

[artemis]

I don't know if it is true or not, but I have heard that the smell of propane is supposedly an added chemical that just happens to be water soluble.. meaning if you have water in your bilge, it is likely that you will be unable to smell if you have a leak until it's too late.

TRUTH

[87gn@tahoe]

I don't know if it is true or not, but I have heard that the smell of propane is supposedly an added chemical that just happens to be water soluble.. meaning if you have water in your bilge, it is likely that you will be unable to smell if you have a leak until it's too late.

TRUTH

Danger Will Robinson!

[Wearyman]

On my father's boat the firebox door (Semple VFT40) has been modified so a portion is permanently closed and mounts a "williams" burner, the other side of the door still opens so that we may add wood (or other flamamble objects) for cold steamup, or for a "pilot light" for the burner. The boiler is a bit too small for the engine and the grate area is too small to be burning solid fuel and keep up with demand. Approx 2-3 gal/hr of straight used motor oil.

Wearyman, steam powerplants have MUCH less thermal effeciency than I think you are giving them credit for.

On my boat with it's "high effeciency" monotube boiler, I burn about 1-1/2 gallons of Kerosene an hour for a 7ish HP plant. (At 9mph it's almost the same fuel mileage as my dad's '77 Ford f250 with an "air brake" camper and a 460ci V8 at 70mph )

If you are going to be burning solid fuel, you will want a large grate area... I'm not sure on the rule of thumb for SqFt of grate area per HP.

I have seen guys use 5gal propane tanks to start the steaming process until they at least had enough steam to start their atomizing burners, then they would leave the propane tank on the dock. I personally wouldn't cary propane on a boat unless it was in an elevated and well ventilated position.

I don't know if it is true or not, but I have heard that the smell of propane is supposedly an added chemical that just happens to be water soluble.. meaning if you have water in your bilge, it is likely that you will be unable to smell if you have a leak until it's too late.

You may be right about my estimation of thermal efficiency. It is likely I am way off.

Nevertheless, what FEW pictures I have seen of the burners in use by the diesel burning boilers leaves much to be desired. they seem to be either two straight tube style burners blowing directly up firetubes, a cylinder shaped burner (I think that's a Williams burner) meant for high-pressure fuels and some kind of simple spiral pipe with holes. None of these really seem appropriate for a slower-flowing fuel like Propane.

Also, one would think that if one is going to use a liquid fuel, one needs to compensate for the "transitory" nature of the fuel. IE: unlike wood or coal, there are no glowing coals and embers to sustain an even heat. it's either "surface of the sun" or "dark side of the moon". Therefore I would think that rather than using a simple, primitive burner , one would want something more like.... THIS:http://www.tejassmokers.com/images/IMG_0510edited.jpg

NOTE: I was going to paste the picture, but it's just too big!

Now THAT is a burner! The company that makes them even advertises them for hobby steam use. (That's the 19" diameter burner) From the company site:

Jet Burner - 19" diameter This high heat, cast iron burner ring has 88 jet nozzles, is designed for use with low pressure propane, and can develop 880,000 BTU of heat. Gas inlet is 1 1/4" NPT. If you want the biggest, "baddest" cast iron burner out there...this is the one! These jet burners will even heat roofing tar pots and other roofing materials. This cast iron burner will be shipped for propane use unless a natural gas version is requested. Use COM#2-60 regulator/hose. Weight 40#. Free shipping.
--------
These burners are also used on live steam trains, back yard trains, maple syrup evaporators... and professional steam cleaning machines.

Now, that particular burner is around $650. So not cheap. But I'm betting that with a little work and creativity it'd be possible to fabricate something like this. Perhaps not as impressive as this one, but still pretty effective. With a little tweaking I'm betting that you could even set yourself up for diesel or Kero burning too.

Regarding safety, I suspect much of that has to do with the proper implementation of the feed system. It sounds VERY much like the previous accidents you've noted have more to do with improperly designed and unsafe systems than the nature of Propane.

Of course, it's going to be awhile until I can build anything, so I've got plenty of time for research. So I'll keep my eyes, ears, and mind open to all sorts of ideas.

Thanks guys!

[artemis]

For what you want, I think you'll find that propane is NOT the way to go. You don't have enough room for what you'll burn.

For example: a 7HP compound engine (will power a 24' boat nicely) will consume approximately 26 gallons of water (in the form of steam) an hour if the cutoffs are set correctly and engine is reasonable "tight". Now 26 gallons of water/hr equals about 220 lbs/hr. If you're running at 150psi (a good pressure for a compound) and you preheat the water using exhaust steam to say 150F, then the number of BTU/lb. to produce saturated steam from 150F water is about 1050 BTU/lb. or 231,000 BTU/hr - and that's with 100% boiler efficiency and if you're doing real well if you can get 40%. Take four average home gas furnaces running flat out and you're getting close. That's the real math, not pie in the skye. Tow a barge behind for fuel? Yeah, that might work.

[steamdonjr]

Generaly speaking I love solid fuel but know many people who use propane as a source of firepower, most of them burn approx 40 lbs in full day of steaming. remember you are creating power not cooking hotdogs so you need a much hotter fire. Most have two tanks connected in a series so it draws from both tanks at the same time with a welding outfit type regulator to control the flow.
Also the gas escaping from the top is a very big problem as propane is heavier than air and will sink into the bilge and slowly rise until it hits an ignition source being your lit boiler and FLASH !!, If you are lucky you will come out unscathed. but once again make sure all your connections are tight prior to opening the tanks. one great man who used propane without issue for many, many years was Ray HasBrouck.

[Wearyman]

Generaly speaking I love solid fuel but know many people who use propane as a source of firepower, most of them burn approx 40 lbs in full day of steaming. remember you are creating power not cooking hotdogs so you need a much hotter fire. Most have two tanks connected in a series so it draws from both tanks at the same time with a welding outfit type regulator to control the flow.
Also the gas escaping from the top is a very big problem as propane is heavier than air and will sink into the bilge and slowly rise until it hits an ignition source being your lit boiler and FLASH !!, If you are lucky you will come out unscathed. but once again make sure all your connections are tight prior to opening the tanks. one great man who used propane without issue for many, many years was Ray HasBrouck.

Ahhh. Now see this is EXACTLY what I was wanting to do! 2-20lb tanks hooked with a "T" or "Y" connector. I was thinking I would put them in the stern and that I would SEAL the tank holding area on 5 sides, with a vent at the top, OUTboard. That way, if I do get a leak, it stays out of my bilge and overflows out of the boat.

It is gratifying to know that Ray used propane. Since I'm planning on building one of his engines once the plans are available again, It would be appropriate to fire my boat that way.

How long is a "full day" of steaming though? 4 hours? 8? 12? That is important as if it's just a couple hours there wouldn't be much point. It's about 20 bucks to fill a 20lb tank, with two tanks that'd be around 50 bucks after tax here in WNY. I would hate to pay 50 bucks for only a couple hour's steaming. An 8 or 10 hour day out is another matter.

[stevey_frac]

Consider that if you were to power with wood, you can buy a cord of hardwood around my area for about $200 delivered. If you are willing to go pick it up yourself stack it, etc, it goes for about $100.

That cord of firewood weighs about 3500 lbs, and provides roughly 24 million BTU. That should be enough to run your 7hp boat for roughly 110 hours, using the above 220k BTU figure. For $100... that turns out to be something like $1 /hr in fuel costs.

$2/hr if you get all luxurious and have it delivered.

Note those figures are based on red oak. Also, that means you are burning roughly 35lbs of wood an hour. Expect to have to carry 400lbs of wood for 10 hours of steaming if you include steam up, and having a bit in reserve!! o.O

Conversely, propane in my area costs $0.70 / litre and contains 24k BTU/litre. By the same metric above of 220k BTU/HR figure, it's going to cost you something like $7 / hr of steaming, and your 40 liters of capacity will last you roughly 4 hours. ish.

Can you tell i'm a fan of solid fuel boilers?


EDIT While i'm on about it, and have the numbers in front of me: Fuel oil costs $.75 / liter here, and contains roughly 36k BTU/l. So to steam for an hour you'd need about 6l/hr with that 220k BTU / hr. That 6l is going to cost your about $4.50 / hr. Much better then propane, not quite as good as wood.

Coal costs roughly $150 / short ton if you can find someone willing to sell you in amounts as small as a ton.

It has an energy density of roughly 10k BTU/ lb. SO you would need roughly 22 lbs/ hr to feed our hypothetical 7hp boat. That 22 lbs is going to be about roughly $1.50. Better then having wood delivered, not quite as good as 'Git it Yourself' wood.

If anyone sees problems with these figures, let me know and i'll update em. It does make an assumption that all burners are basically able to get a complete burn which probably not true of either coal or wood unless you are employing an advanced burner design with heated secondary combustion air.