Buried in my stuff, I have a report on coal slurry as a fuel in diesel IC engines. In the 1980's there was a brief look into this. I think the abrasive qualities killed it. It was somewhat like injecting grinding compound into the engine at speed.

TRAINS, late 1970's I think, had a piece on an experimental engine burning coal dust. It was called the "Snuff Dipper", a western road I think.

I have a gut feeling that this concept of burning coal directly in a diesel engine is going to make a great leap in technological perfection, and emerge as a substitute for oil burning diesels. I don’t see much information on the concept of coal-fired diesel on the web, but there are a few references mentioning water slurry being hydraulically injected as basically a liquid fuel.

Getting the coal into a diesel engine has got to be the main design problem. I believe it will ultimately require an injection system that is radically different than the conventional oil injection nozzle system of diesels. Consider, for instance, a rotating metering screw that delivers small charges of dry powdered coal, which is dispersed in the cylinder by high-pressure air.

I disagree. Grind it fine enough, make a dispersion in diesel fuel, and blow it in through the normal injectors. Engine wear is just a cost factor. At less than $1 per gallon for diesel fuel back in the eighties, the higher maintenance cost canceled out any fuel savings. How about compared to $5 / gal. oil? $10 / gal.? At some point it will become economical to sacrifice the engines for the savings in fuel costs, and then there will be renewed efforts to get the wear under control again.

Dear Paul:
I am always facinated (and occationally amazed) at how different operations address problems (real or percieved) and above all how forgiving the steam locomotive is to it all.
When I arrived at Steamtown in 1981, the SOP at the end of the day was to put in a bank and then spray it with the squirt hose. The idea was that it would coke better. I put a stop to that. The crews found that the coal coked nicely just by leaving it alone.
At "The Valley" our SOP for putting the locomotive to bed is to gradually bring the water level in the boiler up to the top of the glass as the fire is burning down. Once the central portion of the grates are dark (still glowing over the back 2 or 3 feet and perhaps a bit at the throat sheet), we put in the bank. The number of scoops varies between locomotives, how deep the firebed is at the back and how long the bank must last (at least overnight). Some of our firmen prefer a peaked "Ervin White" bank while others like the flat top "Fred Bailey" style. In all cases the bank is "designed" to provide sufficient burning coals to completely cover the grates the next morning when the grates are shaken to clear the ash and the bank is broken out and pushed forward.
Covering the stack (fully or partially) is a judgement call by the fireman depending on whether or not the bank is burning too vigorously,wind direction and velocity.
Typically, we'll leave the locomotive 140 PSI +/- and have between 70 and 150 PSI the next morning with the water level at 3/4 or 7/8ths. Once in a while we'll find the locomotive at or near 175 PSI (low safety valve popping pressure) and/or somewhat lower water level indicating the the safety valve had lifted overnight. Since I have been here (22 years and 4 months, but whos' keeping track) we have, on 3 occations, found the water level at the bottom of the glass in the morning, indicating that the bank was put in too early and/or the pressure was left too high and/or initial water level too low and/or goodness knows.
We have equipped our No. 40's ashpan with damper doors as per Chinese practice, and we close these at night to control the flow of cold air into the firebox. When we rebuild No. 97, we'll make a similar modification.
Now Paul, what we really want to hear about is the Cedar Point bunkhouse...
J.David

This argument assumes the price of coal remains static while oil skyrockets. The reality is that utilities and even entire countries are buying BTUs to convert to electricity any way they can, and coal has skyrocketed as a result--and reactivated some closed mines, as well. I see little way that the cost of injecting a cheap-but-abrasive fuel source into a high-output engine will outweigh the costs of a more-expensive-but-lubricating fuel.......

Does anybody know much about the Oil Pull engine?

dave

I understand your point of preferring the conventional diesel injection system if it means that you can simply burn the coal slurry in the existing diesel engines of today’s locomotives. What I was visualizing would be a completely new diesel prime mover, although it would be exchangeable with conventional engines in locomotive applications. It would, however, require a significant change in how the fuel is carried on-board, as well as some revisions in engine controls, indicators, etc. But the basic diesel electric locomotive concept would remain.

Both of these approaches, plus variations may have already been tried, but I am only guessing. I would like to learn more about it. Wasn’t the original diesel engine invention intended to burn coal dust? I wonder how that was to be executed. I know that conventional injectors and nozzles are extremely intolerant to contamination, so it is hard to imagine that a coal slurry would not destroy injectors in short order. I have been told that water damages them easily.

I suspect that there are dozens of possible systems of injecting coal fuel into diesel engines, each requiring different degrees of departure from a conventional diesel engine. And this array of possible systems implies an array of possible processes to convert coal to an internal combustion fuel, in either a dry or liquid state such as might be required by the various injection system possibilities.

I'm surprised that no one has mentioned that Dr. Diesel's original concept was to burn coal dust in an IC engine, igniting the fuel and air mixture by compression alone. I remember reading that handling the dry fuel presented such a problem that Diesel decided to experiment with liquid fuels.

I remember the Trains article. The "Snuff Dipper" was a T&P steam engine (a 2-10-4, IIRC) converted to burn lignite, a very soft and powdery coal found in Texas. I have to give them credit for trying to use local fuel and save on transportation costs.

The reason I asked is it burned heavy oil mixed with water. Could it burn coal powder mixed with water?

dave

Very interesting Dave. I've seen a couple of Oil Pull tractors in operation at an antique tractor show in Silk Hope, NC a few years ago.

I'd think as previously suggested the problem with burning coal in an IC engine is going to be the fly ash causing abrasion inside the engine. OTOH- if you grind the coal fine enough, it seems like the ash would wind up being so small that it couldn't cause any significant abrasion.

I understand one approach tried has been to mix the coal dust with water to form a viscose liquid or slurry, which can be injected hydraulically. I seem to recall a source saying that this is the approach used by GE in developing coal fired diesel engines, however, I have no idea where the GE technology on this stands today.

I suppose the water in the coal slurry fuel flashes to steam as the charge is detonated. That in itself would consume some of the energy of the coal charge, but then the steam produced is exactly in a position to aid the force of combustion in driving the engine. That part is very interesting. A diesel engine running on a water-based coal slurry fuel would be, in part, a steam engine. It would be an internal combustion engine making steam right in the cylinders.

Oil could be used to make slurry, and it might add some benefit of lubrication in the injection process. It would also add its own fuel energy as it burns with the coal. But then it constitutes a second fuel, and it is oil fuel, so the total benefit of burning cheaper coal is diminished to some extent. The coal pulverizing process also adds cost to the fuel.

Here is a patent description of a coal / diesel combustion process. It talks about the considerable heat that is generated in the coal grinding process being reclaimed as the pre-heated coal is fed into the engine combustion system:
http://www.patentstorm.us/patents/54560 ... ption.html

The problem I see with a coal burning engine is the incredible quantity of ash that coal can produce and how to get rid of it, comply with environmental regulations and also not foul up your engine at the same time.

Any one who has spent any time in a power plant knows how abrasive fly ash is, and just how much of it you get. Thinking of how that ash must act as it blows by under the valves I wonder how long a diesel would last.

There is a lot of ash to remove in a typical power plant, and unlike 50-60yrs ago you can't just throw it all up in the air or next thing you know everyone and their uncle's lawyer is out suing you for damages to their lungs.

I wonder how big of an environmental control system the average locomotive would need to comply. If you look at a coal burning power plant today vs. the same plant 40yrs ago, the one today occupies 2times the original foot print, yet outputs less power, simply due to ever increasing pollution control equipment.

Adam

I recall hearing that the early experiments with coal fired, gas turbine locomotives were plagued by problems with fly ash eroding the turbine blades. Apparently this problem can be overcome by removing the inorganic material from the coal before it is burned. I conclude this from the following excerpt from the patent language that I linked above:

“coal… is diverted to the fluid energy mill. The coal particulates are pneumatically conveyed from the coal pulverizer … into a suitable mineral and ash separator, generally shown at as an electrostatic separator for removing loose minerals and ash from the coal prior to delivery of the "clean" coal particulates into the combustion chamber.”

This dissertation speaks of pulverizing coal in a fluid energy mill to micron-sized particles. What is that, about 1/25000th inch? If you then removed all of the inorganic matter, would that leave only pure carbon plus combustible volatiles? If that were the case, would the combustion produce no ash?