Solid-Fuel as a Direct (Non-Gasified) Fuel for Gas-Turbines?

Thats basically how a coal fired power plant boiler works. They crush coal into a very fine powder and blow it into a massive combustion chamber and burn it in mid flight.

If you want more details find a coal fired power station and take a tour. Many do that as part of their public relations programs. Or at least around here in North Dakota they do. I have been on a number of tours now and its very interesting!

What you're describing is a coal-fired steam-turbine, surely? Steam turbines are a type of external heat-engine.

My Q relates specifically to an Internal-combustion machine - like gas turbines (or Otto cycle, etc).

There has been investigations of a Brayton-cycle coal fired plant in the form of a magnetohydrodynamic generator. This is one way to circumvent the substantial problems associated with pushing fly ash through a combustion turbine.

Interesting.

However fly-ash is produced in far lower quantities from biomass fuels, but that's not me saying it's not a problem. ... So the quality of the fuel is key as I see it.

'....So the quality of the fuel is key as I see it....'

Ash would be a big obstacle for combustion turbine attempting to utilize coal or wood or similar fuels.

What advantage are you hoping to gain by eschewing tried and true boiler technology?

Too much ash is generated with coal or wood to be practical in an internal combustion engine...You do have your solid rocket fuel engines...

How about pulverised charcoal, which is much lower in ash?
And could a chemical agent reduce the ash forming components to near zero?

I'm not asking if it's economical, I'm asking could it be done?

'...I'm not asking if it's economical, I'm asking could it be done?...'

Definitely.

Excellent!
Can you tell me what chemicals are needed to 'clean' the ash out of charcoal?

When you asked if it could be done without regard to economic efficiency, the need for clean fuel was no longer important since there are numerous solutions when no financial restraints are imposed.

The low availability and high costs of burning an ash producing fuel in a combustion turbine becomes a non-issue with a budget that allows for extended downtime, frequent and extensive maintenance and high capital costs for frequent new components.

Another non-budget restricted solution might be something like steam reformation of pulverized coal with the goal of producing purified a gaseous fuel. I haven't looked at that type of thing in a long time, and there must be significant problems, otherwise the cheap price of coal certainly have lead to attempts to provide an alternative to gasoline....

So, if I may paraphrase, are you saying that the reason, independent of initial investment in experimental plant or fuel processing for testing with solid fuels throughout the coal age is because it was just damn obvious that any design would be wrecked in almost no time at all? I can imagine them saying "no need to build that scale model, it's clear as day it'll be broke within the week!".

It isn't as if there was no data on which to go...

Gas and diesel engines gunked-up (technically speaking) over long periods from things like fuel contaminants, blow bye, EGR valves, bad air filters and poor maintenance habits, provide a decent insight into the woes that coal and wood fired ICE would develop in a much shorter period of time.

Damage to turbines due to particulate or liquid impingement is well studied.

Planes aren't too reliable when attempting to pass through volcanic ash.

Around a camp fire, if your marshmallow or hotdog on a wobbly roasting stick momentarily dips just the end into the wood ash below but distracted you do not notice and eventually take a bite. That entire night as you marvel at how in blazes there can still be grit in your mouth, it might become more clear why ash generating fuels are not very compatible with combustion turbines.

The smokestacks of coal fired boilers would also give an indication of the type and degree of fouling that would present such an enormous and constant problem.

so, yeah 'no need to build a scale model'

Er, ...thanks! *wry smile*

Although GTs can take a small amount of water vapour through - about 5% by volume IIRC. I remember reading that pumping in small amounts of distilled water just before the combustor will lower the temp and stop NOx forming.

*NB. May count as off-topic*

Anyway, so as you say, I won't bother building any SF-GT models anytime soon!

Coal oil. Coal liquefaction - Wikipedia, the free encyclopedia

It's easier to pump the liquid stuff out of the ground, for now.

WOODGAS POWERED VW'S AND OTHER VEHICLES

No doubt - 'stuff' in the ground is what the last two plus centuries have been all about!

It might be kinda wrong to ask on an engineering forum what [i]can[/i] be done if not also asking would anyone think it's an economic thing to do in the foreseeable future.

I have a little knowledge (a dangerous thing, they say) of Coal liquefaction, fast pyrolysis and wood gas. It's just it seems that none of those techs or the many others are quite right for smaller-scale applications. Take woodgas vehicles for example, you have to lug a whole trailer (or bed) of gizmos around to run on it. The fuel is low density and, even dry, contains alot of water (that's not fuel in anyones book, unless your name's Stanley Mayer!).

Am having a pop at thinking outside the box, without I hope loosing my grip on reality!

I don't know if it's feasible to scale this down, but:

Fluidized bed - Wikipedia, the free encyclopedia might have some promise.

fluidized bed combustion,

Advanced though it is, this is still a boiler tech though isn't it? Rather than a GT combustor tech I mean.

Edit: I mention this because some of the energy in the fuel is lost through partial oxidation if a gasifier stage 'prepares' the fuel for an I.C. engine (of what ever type).

Slowly, are we finding that it may not be an efficient way to burn solid fuel, especially in a small package?

Keep thinking, though. "Rome wasn't built in a vacuum".

OK, it's my day to butcher old sayings.

''Polished swords, butter no parsnips''

Ooo, sayings! - I got an oldie too: 'Nothing new under the sun'. One that sums up why I'm having a hard time accepting that no prior art exists on this - ie. someone must have had a go at some point.

IIRC there have been times when gas turbines have been used with external combustors, though I can;t recall what difficulty this overcame. I can envisage a part external gasification with the reaction chamber in close proximity to the combustor (heat travels through metal I've heard!). The (mainly) carbon monoxide could then be circulated into the main burner in theory .... except I think the CO would need to be formed with pure O2 otherwise the feed-gas in the main combustor would be aerated with lots of LP air which would ruin any gains from the compressor stage.

''the early bird gathers no moss''

So true!

Lyn my man.

You are what you are.

Do you like Nascar racing?

I do not see a reason why it cannot be done. I suspect that it cannot be done economically or there would be stationary facilities already using pulverized fuel directly into a turbine. I suspect the added pressure boost of enthalpy from converting water into steam and back is the added efficiency why power plants work as tcmtech mentioned. (That's horribly phrased but I think the meaning comes through. Forgive me. )

Well, at least I'm not alone in my -crazed- conviction then!In fact I wrote, "I'm sure this must have been experimented with during the age when coal was king" heavily under that influence!

I had reckoned in all the years of using coal there must have been an effort to experiment with, if not gas turbines, then piston engines using the stuff. Perhaps, the very fact that coal is so chemically nasty for high tolerance machinery is why such tests were never bothered with.

Rudolph Diesel had coal dust in mind as a fuel when he developed his engine.

I was wondering if anyone would mention that bit of history. I believe his difficulty was almost blowing himself to bits? I understand the engine was not strong enough for the coal dust. Or maybe I remember it wrong?

Can you explain the bit about pressure boost and enthalpy a bit?

An interesting way to burn coal dust is in 'pulsating combustion'. The combustion chamber is shaped like a mason jar, and combustion is very efficient. The Germans experimented with it for power generation, even had some of their rockets using it. We were blowing up their petroleum supplies, so they used coal, very efficiently, too.

I forgot to cite Wikepedia for the above info, see the full article here...

http://en.wikipedia.org/wiki/Union_Pacific_GTELs

For a more modern (1981) approach to direct-firing check this out...

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1151513

Abstract

A direct coal-fired turbine is a very light engine for powering ships. Weight savings over a diesel engine nearly make up for the added weight associated with fuel bunkering when converting from oil to coal-firing. A method of hot-gas-particulate cleanup based on fragmentation using pulsed CO, lasers is discussed as a means of providing adequate turbine blade life- time. Two cases, a cargo ship and large merchant tanker are considered. Present value of fuel savings equates to the value of a coal- fired turbine For a ten-year lifetime, the value of the turbine due to fuel-lost savings is projected to be roughly 48 M$ for the cargo ship and 194 M$ for the tanker.

Thanks RAM' - This is exactly the kind of experimentation that I was convinced some firm or uni/school must've had a go with at some point.

As I wrote earlier, I'll repeat the old adage 'nought new under the sun'. Or put another way, most of everything that technology allows will have been tried - even the borderline ridiculous.

So the lesson I think I've learnt on this is: If you want to drastically shorten the life of your GT then go on and fire it with solid fuel!

Modern day wood gas fueled cars....

In the old days....

http://www.lowtechmagazine.com/2010/01/wood-gas-cars.html

I know that Rudolf Diesel has made his first trials with the intern combustion engine with dust of coal but one of the great problem was the remaining ashes...

I suppose ashes will also be critical for the erosion of the turbine blates...

Léon LAKAIE

Brussels Belgium