The Steamboating Forum

Has anyone here ever heard of a multiple-fuel boiler? That is, a boiler that can operate on either a liquid fuel, such as LP or Atomized Diesel, OR a solid fuel such as wood or coal?

I was thinking that a design that operates primarily on LP, but in a pinch the LP burner could be removed from under the boiler and a wood/coal grate be put in it's place. The thinking behind it is that should one be out and about and run out of liquid fuel, one could simply scavenge some solid fuel to get home on.

Thoughts?

Dear wearyman ,

What your proposng is certainly possible . Quite a few boilers have been converted from liquid to solid fuel and vice versa , but usually on a permanent or at least semi long term basis .
Probably the most important thing to take into consideration ( other than planning your journey so as not to run out of fuel ) is the different calorific value of the fuels you might want to burn . You should design your combustion space so it is big enough for the less calorific fuel otherwise you will struggle to get enough steam if switching from say propane to wood .

Regards Edward .

Wearyman wrote:Has anyone here ever heard of a multiple-fuel boiler? That is, a boiler that can operate on either a liquid fuel, such as LP or Atomized Diesel, OR a solid fuel such as wood or coal?...

Thoughts?

Artemis came with a "lawn sprinkler" type boiler and when I modified the "new" watertube boiler I installed in 1996, I redesigned it so that it could burn wood or or be switched over to steam atomized furnace oil. The fire door(s) were of a "pintle and hook" type similar to those used on rudders of earlier sailing ships. Thus by lifting the door "straight up" the "wood furnace door" - just a plain panel with a swing bar and hook type latch - could be replaced with a "steam atomizing oil door" - with all the oil burning stuff ready to light off - and vice versa. The two piece wood burning grate could be removed or installed with one of the wood fire tending tools, the appropriate fire door installed, the fire lit off, and away we go.

The pic below illustrates the oil firing furnace door - steam lines are on the boiler casing to the right. Complete burner assembly including steam to burner "dryer" is mounted on the burner door. I took a page from Bart's book and use propane as the atomizing agent when firing from cold. This is done by means of a three way valve on the burner assembly. Once I've got 15# steam pressure on the regulator line, I switch over. There's a nice article on this burner with complete build instructions in Steamboating Magazine, Vol. XI, No. 1, Jan/Feb 2007, issue.

View of fireside of the same door showing steam "dryer" is below

"Steam Queen" starts up on wood then we switch to used car oil ,diesel,electric transformer oil,vegetable oil -run what you brung!! I have found that all liquids should be filtered just to remove all things that end up in used stuff! I also run a gravity Day tank which has a bottom drain to remove water.Burning wood is quiet,uses no steam in the atomizer,smells better but you'll need alot because it can't match the BTU s available in the oils. I could burn coal if I added a grate but coal is not readily available on Vancouver Island. I read somewhere that plastics,rubber tires etc cover your tubes in the boiler and are frowned upon when passing white sail boats! Den

Oh wow, I didn't know there was so much versatility in fuel choices! That's great to hear!

Incidentally, I would like LP to be the primary fuel for my boiler, largely because it is inexpensive around where I live (near Buffalo NY, USA) and because of it's high BTU output. Also because propane-oriented burners are laughably easy to come by in an array of shapes and sizes. Just visit any hardware store and you can find at least 15 different makes and models to choose from.

I figure if I am careful with the design, I can set it up to that the burner sits just on top or above the solid fuel grate, with a swing door much like artemis describes to access the burner area should I need to. Then if I get overzealous and stay out too long, since I'm planning on sticking to the local rivers and canals there is plenty of brush and deadfall to pick from. (most of the Erie Canal in my area runs along farmland with lots of old hobnail trees and deadwood laying about.) Although I do plan on designing in room for 2 standard 20lb propane tanks, so I doubt I'll ever need the option. But I always like to have a backup plan.

artemis, I'd love to see those pictures if you have them. It will help me when I get down to designing. Thanks!

One more thing about wood firing. You will need dry wood.All these ol' timers that used to burn driftwood had large fireboxes to compensate for burning beach wood. I very quickly found that when burning green wood a tremendous amount of BTU's went just to get the moisture out of the wood-we were making steam alright but it was on the wrong side of the boiler! Propane works great but the valving freezes because of the volume of propane used so some sort of heater will be needed if you experience this. Perhaps someone who is burning propane could enlighten us as how to overcome this problem! Den

farmerden wrote:One more thing about wood firing. You will need dry wood.All these ol' timers that used to burn driftwood had large fireboxes to compensate for burning beach wood. I very quickly found that when burning green wood a tremendous amount of BTU's went just to get the moisture out of the wood-we were making steam alright but it was on the wrong side of the boiler! Propane works great but the valving freezes because of the volume of propane used so some sort of heater will be needed if you experience this. Perhaps someone who is burning propane could enlighten us as how to overcome this problem! Den

The Green wood bit I absolutely concurr with. growing up I was in a Boy Scouts-esque group and they told us never to try burning green wood. Not only does it burn very poorly, but you would be cutting down a perfectly good tree for wood you couldn't use. I figure if it works for campfires it works for small steam boilers. I was thinking more along the lines of scavenging dry deadfall, of which there is plenty to be had around here.

In regards to Propane, I'm not sure what you mean by "valving freezes". I was planning on using a burner (and feed hardware) originally designed for a backyard Propane grill. I happen to own a very nice Weber propane grill and I've never had freezing problems with it. Indeed, I can even grill in below-freezing temperatures with no trouble.

The only thing I can think is if you tip the tank over so that pure liquid propane is coming down the line, then you would have a problem. But since most LP tank systems are designed to use the LP that has sublimated into gas and is floating above the LP pool inside the tank, I doubt freezing would be an issue. At least I hope it wouldn't be.

I was hoping a propane user would reply but for now I will say that I think where the propane leaves the tank is the problem.This boiler you have will burn a staggering amount of fuel. I use 2 1/2 gal an hour [diesel] thats about 250,000 btu's ! that's similar to heating two and one half homes!! These things are not your back yard barbi! Anybody running propane fell free to jump right in here! Den

Have to agree with Farmer Den.

In the PacificNW (Washington/Oregon USA) there are a number of propance fired boats. Numbers vary from year to year. Although there have been anumber of incidents involving leaky gas, these were invariably OPERATOR caused.

The biggest problem is the quantity of propane gas required as compared to the heat exchange surface of the propane tank. The propane in the tank is in liquid form. When it is withdrawn from the tank it must be turned into a gas - i.e. heat must be drawn from the air surrounding the container. If the quantity of heat required is large enough, the container and its valve and regulaor will aquire a THICK coating of frost (moisture condensed our of the air as heat is extracted) which cause the tank to "freeze up". No more gas flows. I am aware of at least two occasions where "heating" the tank caused fires - fortunately with no serious injuries. The tank was "frosting up" so the owner built a watertight box in which to place the tank and installed a couple of coils of copper tube from the boiler with a shut off valve to "help things along". Yep, you guesed it. 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.

And I wouldn't trust a temperature over-ride sensor shutoff. If the boiler requires more heat than a propane tank sized to fit the boat can handle then DON'T BURN PROPANE! However, anything under 15' should be OK. I'm thinking about using it in my next boat, 13-1/2' x 1HP, about 30# steam per hour

farmerden wrote:I was hoping a propane user would reply but for now I will say that I think where the propane leaves the tank is the problem.This boiler you have will burn a staggering amount of fuel. I use 2 1/2 gal an hour [diesel] thats about 250,000 btu's ! that's similar to heating two and one half homes!! These things are not your back yard barbi! Anybody running propane fell free to jump right in here! Den

Well, as long as the fuel leaves the tank via the top it should be OK. Propane is a gas at "room" temperature. It has a boiling temp of -42 °C or -43.6 °F so as soon as it leaves the pressure vessel of the tank it instantly vaporizes. Basically the tank is all that's keeping it as a liquid. Once you open that valve it will rush out as fast as the open space allows. So flow rate should be doable.

I am surprised that you go through so much fuel. That seems like a rather large amount, but then I don't have the experience with steam power like you do, so it's highly likely my estimations of the heat needed are way way off. But based on what I know about the heat producing qualities of various fuels I know that:

1 gallon of "diesel" fuel = 139,000 Btu
1 gallon of gasoline = 124,000 Btu
1 gallon of propane = 91,000 Btu
1 lb of coal = ~8800 Btu (depending on type of coal)
1 lb of wood = ~7000 Btu (depending on the type of wood)

Based on these numbers you can see how confusing this is. By all rights, your rig should be just sipping fuel. Yet it appears to suck "diesel" down with wanton abandon. So one must ask how wood burners are able to get by with just a few pounds of wood stashed in a small space while you run through gallons and gallons of "diesel" in the same amount of time.

I'm hoping it's just a trick of burner/boiler design and not an inherent issue with steam power. Not that I can't change my plans, but I had this nice layout going in my head and I'd hate to have to trash it.

farmerden, do you have any pictures of your burner setup? I'd be curious to see what you have.

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NOTE: I wrote the above the other night, but began to have issues with my internet connection. So I copied it to a text file and saved it for today.

Now that Artemis has replied I can see that there is likely more of an issue than simple burner design, although that may still be a problem. I'm beginning to suspect that you simply need a boiler designed around using Propane and it's lower flow rates. I'm guessing that this means the whole "multi-fuel" concept is a no-go. At least with Propane as the liquid option. I may just go with a solid fuel solution instead. I'm NOT about to risk having a "flying boat" (for all of 10 seconds) just for the convenience of propane.

Although one MIGHT be able to overcome flow rate issues by using two 20Lb tanks in tandem with a "Y" adapter on the feed line. I'd like to see what some others have done. And of course using propane as a "starter" for a wood or coal fire would still probably be a viable concept. (use propane heat for building quick steam and getting the wood/coal fire started, then more wood/coal to keep it going.)

Incidentally, I'd like to thank you guys for entertaining my questions. I'm absorbing as much as I can from all of you and in the process I've got this bubbling pot of information and ideas perking away inside my head. It's great to be able to check some of my ideas against your experience and see how realistic they are. Thanks.