Last week we had a very interesting discussion about the environment, CO2 and Greenhouse gas emissions and our 2 locomotives. I will leave my personal opinions on the side track for now, but can anyone here with hands on experience, post their pro's and con's of converting a oil burning locomotive to LNG [liquefied naturel gas] . Other than the cost, which would be horrendous, personal safety, storage facilities, loading/unloading, changes to refractory, consumption, etc. comments are what I'm needing.

Thanks

Brian Manning

The Florida East Coast Railroad is currently testing diesel locomotives that have been converted to LNG. By "oil burning locomotive" do you mean a diesel or a steam locomotive? Steam would be a whole different ball game. Here's a link to an article describing the FEC locomotive program. http://www.americanshipper.com/Main/New ... .aspx#hide

I occasionally work as the engineer on a two foot gauge Crown locomotive. (Yes, I know, it's not the same as a full size loco.) It's been converted to Propane and generally works well. Obviously it's quite clean, no smoke smell, and easy to fire. Unless you over-fire, the're no odor at all.

I would suggest trying to determine comparable BTU outputs for the various methods of firing. With a heavy load, the boiler can't quite keep up going up the hill and pressure slowly drops until one of two things happen. You either crest the brief grade with say a 20 psi drop, or, if it's a big load, your speed drops along with the pressure and you get to where thing settle into equilibrium and you're only using the amount of steam she's making. Either one works just fine for this operation. If it was a much longer grade and you'd have to add water during the pull, things would be challenging.

Many factors could be at play here. The original design of the boiler, the type and size of burner installed, the number of cars being pulled, etc. etc. However, I am off the general impression, maybe incorrect, that the propane doesn't put out as much heat as oil would.

Jeff, we talked about both , but I mistakenly only typed in LNG. Storage is a real concern for me as well as a tender full of either bottles or a huge pressure tank.
We have always had 2 or 3 environmentalist's every season asking questions about the fuel we burn, lubricants, etc, , and a issue was brought up again last week. The provincial governments attack on all forms of carbon, and everything which burns fossil fuels is under the microscope. This is only just a discussion at this point.
We currently burn recycled motor crankcase oil for fuel at a rate of 1000 liters [223 Imp gal] per day,7 days a week, for +/- 120 days. The boilers have a heating surface of 2400 sq ft, saturated steam. We have 2 grades of 1-2 %, and pull only 3 passenger coaches for a total weight of around 290 ton, including the engine.

Brian Manning

Let's do some napkin math.

we'll assume nat gas is about 1000 BTU per cubic foot, and Waste motor oil is about 150,000 to 200,000 BTU per gallon

You're using between 34 and 45 million BTU per day.

That is between 34,000 cubit feet to 45,000 cubic feet of natural gas per day. Keep in mind this is the bare minimum, fuel tank runs bone dry

That is a container between 33 and 36 feet square on each side. Huge!!

Wiki says LNG drops that by a factor of 600, so now we are down to 57 to 75 cubic feet, less then 5x5x5, so much more practical (very close to a 1000 gallon). Keep in mind liquid pressure tanks need about 25% headspace additional.

The REAL issue with LNG is that you have to keep it cryogenic. -260 F. You have to find a place to keep 1000 gallons of cryogenic LNG for each operating day! If you don't use your fuel, you must either run a refrigeration plant to keep it cold, or let it evaporate enough to keep it cool. If you shut down with any fuel left and don't use it, it will simply float away never to be seen again.

CNG is much more "practical" in storage, but requires tanks rated past 3600 PSI!!! The volume is about 2.5 times LNG, so you need 2500 gallons per day. Advantage is that the equipment exists to make it on site.

Why not consider propane? The pressures are MUCH more reasonable, storage and delivery much simpler, much higher energy density then LNG?

The Crowns at Kings Island are propane fired, they use multiple commercial tanks located in the front (fuel) pocket. They have replaced the blowtorch burner it originally came with with one that more evenly distributes the heat.

You might want to consider a cleaner oil firing system such as that used by Sulzer / SLM in their new generation of rack locomotives. They have a series of vaporizing burners surrounding a small pilot burner which is capable of holding pressure at spotfire on tis own. Fuel is light oil, not waste oil or heavy dirty fuel oil like Bunker C. The technical information they were distributing compared their system favorably with diesel powered locomotives in terms of exhaust products of combustion.

In the interest of full disclosure, part of my work involves CNG and rail. That being said, let me add a few thoughts.

Dave's point about moving to a more advanced liquid fuel burner is a solid option, especially if you switch from reclaimed motor oil to bio-diesel or similar which is used to good effect by a number of operators i.e. Disneyland, GCRY...the biofuel even works fine with conventional locomotive oil burners.

Propane is a cost and space-effective option with the main safety concern being that the fuel is heavier than air, so leaks will pool in low spots. In terms of environmental performance, natural gas, however, generally does better than propane due to the lower hydrocarbon chain carbon count of natural gas vs. propane.

CNG is also a good option with a range of tank technologies from Type 1 (all metal) to Type 4 (composite pressure vessel with plastic liner) that can safely handle the pressure and allow for a range of prices. While one person seemed concerned about the 3600 PSI pressures, the standards developed for this equipment (including hoses, nozzles, etc.) assure a very high degree of safety. For example, the Type 4 carbon fiber tanks I am familiar won't burst until they are pressurized well over 10,000 PSI and have been subjected to everything from fires, to gun shots, to drop tests and hard couplings (the latter conducted at TTCI in Pueblo). There are a variety of tank sizes and some clever packaging options that can be used to fit the amount of fuel you would need on your train as appropriate to your operation...a detailed discussion for another time.

LNG certainly does have better range performance than CNG, but the extra precautions needed for handling the cryogenic fuel and some other details regarding its use and sourcing make me suggest that it would not be a good option for most smaller operations. I should note that LNG boil off is much less of a concern these days as vacuum-based "super" insulations have dramatically reduced heat leak issues.

If your organization does want to take a serious look at this, feel free to send me a PM.

Cheers,

Personally I would go for Dave's option, clean diesel oil. However with the added option to take a second look at the exhaust system. Adding oil in a locomotive burner frequently leads to black smoke/soot because of lack of proper oxygen levels. So proper operation would be to take care of the oxygen supply first and seconds later add oil. As for gas, there is a curious mismatch between its storage and operation and its btu content. The hydrogen component releases 4 times the amount of btu's compared to the carbon component based on weight, so in theory it is better to use fuels with the highest amount of hydrogen. Sofar not mentioned is a hybrid system, clean oil for a steady state operation and additional gas when needed.
Kind regards
Jos Koopmans

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A few comments



This is a good idea in theory, but in practice you'll want to watch out for the 'taking care of the oxygen supply' not chilling down the firebox and boiler structure in the absence of firing, or tending to create any volume of critical mixture in the gas path while the added air (I'm presuming he is not calling for injection of actual oxygen or oxygen-enriched gas instead of primary/secondary air) is being admitted.



This is nice when referring to stoichiometry, or perhaps use of the heat of combustion in an internal-combustion engine, but it ignores the fact that the heat from the gas has to be coupled to the internal boiler structure for heat transfer. The products of combustion of hydrogen are transparent, whereas much of the initial combustion of carbon (in oil fuel and of course coal and coke) produces a broad-spectrum radiant emission (from the physical carbon particles as combustion to CO/CO2 occurs and the gas scrubs off the surface to admit further oxygen). Part of the rationale for control of secondary air admission is to prolong the radiant emission as long as possible, so there is some control of the actual oxidizing atmosphere within the firebox volume; remember also that the whole combustion is below atmospheric pressure (with some very slight, really accidental, exceptions - see the pressures observed in testing in the Santa Fe Big Three book).

Remember that the whole point of Besler tubes is to absorb the peaky emissions from gases and then re-emit the energy 'normal' to the enclosing tube wall with a broader spectrum.



Most dual-fuel arrangements have historically been for convenience or overall economy in fuel selection. Since part of the problem with light-oil firing, historically, has been perceived as a relative lack of "delivered" BTU content to make steam, there may not have been much call to provide a dual-fuel system that augments firing with lower-energy-density primary fuel admission. I think it is likelier that a system designed for this would ge geared toward reducing toxic exhaust emissions (e.g. for operation in enclosed or restricted spaces) with the oil perhaps cut back to minimum for effective flameholding.

In the late 1990s I looked at both the idea of flutter burners for 'turndown' of supplemental or primary gas firing, and the use of 'gas-fired independent superheaters' to keep steam quality high at periods of relatively low gas mass flow across superheater elements. Neither of these was particularly cost-effective and the 'special needs' in either case were not typical of practical use of locomotives for contemporary purposes. In my opinion they have more use as 'maintenance' devices (e.g. for maintaining boiler pressure in the absence of power for an 8055-like electrical-element system, or providing short-term clean firing increases) than for active firing at a high percentage of heat release.

I would like to establish one point about LNG firing: part of the perceived difficulty with LNG as a compression-ignition locomotive fuel is that so much heat has to be put in to get it to a 'combustible' state. There are lavish and available sources of heat on any external-combustion locomotive to provide this at any time other than the early stages of cold startup. I also have to wonder whether it is that much more difficult to arrange for liquefaction of gas that has been compressed to high pressure from 'commercial' gas sources (as is mentioned as a CNG fueling-option advantage).

Thanks to everyone for the discussion in regards to oil conversion. This is exactly what I was trying to achieve; a wider insight into the pros and cons of this topic. The waste oil burns relatively clean, and I have instituted a more in-depth training component for the Engine Crews to eliminate the possibility of heavy smoke, what with the environmental concerns in everyone's mind......BUT, as you know , there is always 1 !!!!
Due to efficiencies in boiler management, water treatment, refractory design and firing techniques, I have managed to decrease the fuel consumption by 47% over the last 7 years.
We try to be as environmentally friendly as we can, by using a biodegradable grease, Synthetic lubricants and eliminate drips/pooling by installing track mats at all the station stops. As I mentioned, this is just a discussion now, to collect as much information as we can. Any more insight is appreciated.

Brian Manning

You're dead on about it being the whole system, not just the fuel. Nigel Day achieved a 50% drop in fuel consumption at the Cog by system wide reengineering, which included an exhaust steam feedwater heater - perhaps there's an opportunity for something along those lines that could make your operation even cleaner?

Please tell us more about the work you have done with details.

This would be the same as opening up the regulator or increasing the cut-off. Both actions generate more air in the firebox. However if you cannot miss the steam, a Lemaitre type multiple blastcap is the idea where the orifice in the centre could be closed, increasing the blastpressure and vacuum generation a few seconds before extra oil is fed.
Kind regards
Jos Koopmans

But carbon weighs about 12 times hydrogen. In practice, the more carbon dense (and dirty...) fuels have more punch. From least to most
NG
LP
Kerosene
Gasoline
motor oils
Diesel
Bunker fuels

(keep in mind they all can vary a bit due to exact composition)