Improvements in coal-burning power plants?

nicholas bonham-carter

I was watching "The Crown" on Netflix. The story was of an early poisonous smog, which had descended on London in 1952. Sulphur dioxide from the power stations was not being blown away by the wind, and instead settled on London, resulting in many deaths (thousands apparently).
It made me wonder what improvements have been made with modern technology in regard to coal-burning power. Has it been somewhat cleaned up, or now just the same pollution as before. This may have been the result of burning Bituminous as opposed to Anthracite coal. Shall we be thankful now for still having so much natural gas with which to fire the grid?--NBC

Jamie Hall

Good lord -- so many improvements, @nicholas bonham-carter ! I can hardly count... first off, that smog -- and it was thousands of direct deaths -- was mostly from coal burning on individual hearths, not power plants. But... almost all coal fired plants today use scrubbers of varying designs to remove almost all the sulphur dioxide from the stack gas, and do a very good job of it, too. (At least some of it is recycled into drywall, believe it or not!!). Also, the overall efficiency is much higher now, from higher steam pressures (like... much higher!) and better alternators and prime movers (turbines instead of piston engines, for instance). Coal does produce more carbon dioxide than natural gas does, however, so there is an advantage there, too.

hot_rod

I wonder about the "improvements" for the workers at the coal mines? Or the people living down wind and down stream?

Both of these claim to be coal miners. One of them probably from the Clean Coal ads on TV.

Solid_Fuel_Man

I was under the impression that the vast majority of coal was mined by machinery. Not with people with pickaxe down a long tunnel which could cave in any time.

I also believe the anthracite (hard coal, or black coal) is reserved for heating as its inherently cleaner. Bituminous (soft coal, brown coal) is burned in power plants where the stack gasses are scrubbed.

I'm pretty certain America is the only place in the world with anthracite coal. So some of the stories are not as applicable as the rest of the world.

Either way the ash is more of a problem, coal produces a lot of ash which can have heavy metals in it.

Note: I did no fact checking, this is my general knowledge gathered throughout the years and it may not be accurate.

Jamie Hall

So far as I know, @Solid_Fuel_Man , your facts are accurate. There's very little underground minng done now, at least on this side of the pond (the Chinese still do a fair amount), and some of the machinery used is pretty spectacular (I made a U-turn in the bucket of a dragline once -- driving a Chevy pickup... just for the h__l of it).

And coal ash is a real problem -- as you say, heavy metals.

Sal Santamaura

Jamie Hall said:

...Coal does produce more carbon dioxide than natural gas does, however, so there is an advantage there, too.

Advantage? Coal causing the planet to heat more than natural gas does, thereby accelerating the unemployment of heating contractors?

Methinks this thread might be heading to "The Politics of Heating" category.

Jamie Hall

No, no, @Sal Santamaura -- I meant there was an advantage for natural gas!

hot_rod

Solid_Fuel_Man said:

I was under the impression that the vast majority of coal was mined by machinery. Not with people with pickaxe down a long tunnel which could cave in any time.



I also believe the anthracite (hard coal, or black coal) is reserved for heating as its inherently cleaner. Bituminous (soft coal, brown coal) is burned in power plants where the stack gasses are scrubbed.



I'm pretty certain America is the only place in the world with anthracite coal. So some of the stories are not as applicable as the rest of the world.



Either way the ash is more of a problem, coal produces a lot of ash which can have heavy metals in it.



Note: I did no fact checking, this is my general knowledge gathered throughout the years and it may not be accurate.

I think long wall mining is still a common method, and it does involve crews underground, although without pickaxes.

They mine right under homes and buildings.

http://www.popularmechanics.com/science/energy/a5527/dangers-in-longwall-coal-mining/

JUGHNE

I recall that in London in the mid 70's most hearths/fireplaces were closed up and that is where the electric heaters would sit.
Generation was by what I don't know.

Any picture of an old city like that shows multiple flue stacks on a single building. Easy to imagine the pollution if they all fired.

Solid_Fuel_Man

That's why London fog went away...they stopped burning coal. Remember that was dirtier brown coal, and in uncontrolled open fireplaces. All those chimney pots are quite aesthetically pleasing to some.

Think of **** VanDike on Mary Poppins. Chimm chimm chimmmnie chimm chimm charrooo.

As far as politics go, we can burn NG till it's gone, or we can burn coal where it can be controlled and flue gasses scrubbed. NG has some drawbacks politically think fracking. I, by no means, have the answer to that one. Just that we are fed the info we want to hear, or believe what we want to believe, (man-made) global climate change or not.

Sal Santamaura

Jamie Hall said:

No, no, @Sal Santamaura -- I meant there was an advantage for natural gas!

Thanks for clarifying. I read it the other way around, since everything else you'd written up to that point described how modern coal burning was improved, giving the impression that 'more CO2' from coal was better.

Thanks again.

BobC

i remember a george Gently episode where george had to put a coin in an electric meter to turn the power on in the flat. There was a electric heater sitting in the blocked up fireplace. Watch the last few minutes starting at about 1:20

https://www.youtube.com/watch?v=c1ksXLg2fw4

Bob

JUGHNE

And the point made that the old pensioner had to plug his electric meter while there were a 100 street lights burning outside during the day.

BobC

The poor always pay.

Bob

JUGHNE

Mismanagement by government agencies really made the point. The rest of the rate/tax payers have to pay for daytime lighting. Rich and poor alike.....IMO.

jumper

I've tried using furnace coal -the clean washed shiny hard stuff– in a fireplace and it didn't burn. Why?

Jamie Hall

jumper said:

I've tried using furnace coal -the clean washed shiny hard stuff– in a fireplace and it didn't burn. Why?

There's a real trick to getting that stuff going -- one needs a good hot kindling fire, and a good draught. And the correct grates. Without a proper coal grate, it's pretty hopeless.

EBEBRATT-Ed

I started my career at an oil company. Back then we were taught in school that gas will never have the efficiency of oil because of the water vapor content in gas (and this is true). The water vapor in gas had to be boiled and that heat was lost up the chimney.

Well guess what? The technology changed and condensing gas appliances make gas more efficient than oil (non condensing oil)

I am sure they can make coal burn clean. Maybe the technology isn't cost effective now but someday it very well could be

hot_rod

Burning rocks! To make steam, steam to spin a turbine, turbine to spin a generator, really this is the way to generate electricity?

Granted all energy come with a cost, ask the residents of Oklahoma, the earth shakes there almost daily since fracking started. But until it shakes someones home of political importance the drilling goes on

NG is still a lesser of two fossil fuel evils both for efficiency and quick ramp up and down.

Clean burning burning coal, whatever that means, still requires the boiler and steam conversion and it is not a ideal way to match ever-changing loads in the grid.

Once used as peak shaving for it's rapid acceleration, NG is now replacing many, perhaps most coal plants.

I doubt we we return those plants to coal

Solid_Fuel_Man

Well if you burn NG in mass quantities to generate electricity, we will still run out sooner than if we burned something else.

I still wonder what the future of nuclear is.

jumper

Industrialists can improve anything they produce. And continuously more economically as well. Except atomic energy?

Jamie Hall

Thermodynamics 101...

The maximum efficiency of any engine is determined by the two temperatures between which the engine operates -- the highest temperature reached and the lowest. Sadly, for all the wizards of Silicon Valley -- or Washington, D.C., -- the ain't no free lunch, and the temperatures set an absolute upper limit.

Now... A modern steam power plant, running supercritical steam, can reach -- without that much trouble -- an efficiency on the order of 50% of the input fuel energy to the output electrical energy. A gas turbine can reach about 40% with current technology, although there are folks working on ceramic turbines and stators which will allow raising that to perhaps 50%. Diesels also run around 40%; gasoline engines slightly less, although again they are getting better.

The input fuel for a steam power plant does not affect its thermal efficiency, although it may affect its overall efficiency; coal burning plants in particular lose a few percent to pollution control equipment.

For peaking power or standby power, natural gas or oil fired gas turbines are the way to go (coal fired gas turbines have been tried, but have problems due to the erosivity of the ash on the turbine blades). Why? Not because of their efficiency -- as noted above, 40% vs. 50% -- but because a gas turbine can be brought from a cold start to full load in a matter of minutes for big ones, and seconds for small ones.

Natural gas also has an advantage in today's environment in that the amount of carbon dioxide produced is significantly less than either oil or coal.

From the standpoint of environmental impact, and considering only fuel burning power conversion, a natural gas fired supercritical steam plant beats anything else, closely followed by oil fired, followed at some distance by coal, and then followed at another considerable distance by gas fired and oil fired gas turbines.

This is considering only the conversion to electricity, and only fuel fired equipment. Now if we figure out some way to use the "waste" heat from these plants, the equation changes somewhat; if the waste heat can be used for space heating (for instance, "Big Allis" -- ConEd's power plant on the east side of New York City) there are major overall gains. It can also be used for industrial process heat -- or distilling sea water or waste water to drink.

Then there are fuel cells. They can reach 60% efficiency -- but only using hydrogen. If they are to use other fuels, the fuel must be reformed and something clever done with the remaining carbon. The hydrogen can also be produced by electrolysis of water -- but the electricity has to come from somewhere, so the overall efficiencies are the project of the fuel cell efficiency and the generating efficiency -- and the result is pretty horrid if fuel burning power is used to create the electricity. ("zero emissions" electric cars have this problem, too).

Then, for proper consideration of environmental impact and all, and taking as wide a view as possible of the various fuels, one must consider the costs (monetary, environmental, social, political) of extracting the fuel in the first place, moving it to where it gets used, and disposing of any waste materials produced.

There are no simple answers, nor one size fits all answers, despite the sound bites, tweets, banners, protests and what have you. Sorry about that.

Then there are various renewable energy sources -- wind, hydro, solar, even wood -- but they all have the four major costs, some of which are really significant (hydro, for instance, has huge environmental and often social costs). Wind and solar are further compromised by the storage problem -- which has its own costs, which can be very significant.

Then there is nuclear. The actual costs and risks associated with nuclear are smaller than any other energy source. Unfortunately, the political costs of nuclear have been overwhelming. Perhaps these can be overcome in the future, though I am not optimistic about that.

I hope all this helps...

Solid_Fuel_Man

We have two biomass (wood chip) Electric generation facilities near me. While interesting, it kills me to see those sopping wet green, piles of wood headed to the boilers. There is a tremendous amount of heat lost just to boil that moisture off so combustion can occur.

The time to dry, or the energy to force dry that fuel would also be tremendous so they burn it green. Most of this is "junk wood" which is chipped in the forest and hauled to the plant. Those who burn chips for heating want dry hardwood chips.

@Jamie Hall excellent write up, I was wondering when you would weigh in!

hot_rod

Solid_Fuel_Man said:

Well if you burn NG in mass quantities to generate electricity, we will still run out sooner than if we burned something else.



I still wonder what the future of nuclear is.

We need an electrical energy source that doesn't require burning anything

Be interesting to see if Sweden hits that fossil free target.

http://www.government.se/government-policy/fossil-free-sweden/

jumper

Country folk who heated home with wood air dried it for at least two years. Almost every winter there was a period of deep freeze so the second year was redundant. But the security of all that fuel was comforting.

hot_rod

Solid_Fuel_Man said:

We have two biomass (wood chip) Electric generation facilities near me. While interesting, it kills me to see those sopping wet green, piles of wood headed to the boilers. There is a tremendous amount of heat lost just to boil that moisture off so combustion can occur.



The time to dry, or the energy to force dry that fuel would also be tremendous so they burn it green. Most of this is "junk wood" which is chipped in the forest and hauled to the plant. Those who burn chips for heating want dry hardwood chips.



@Jamie Hall excellent write up, I was wondering when you would weigh in!

I'm surprised the boilers are allow to, or can even tolerate wet chips?

I see some of those large chip burners have dryers that use some of the flue gas or boiler output to dry the chips.

Chips seemed like a better alternative to pellets which take considerable energy to dry and press, store and haul.

Solid_Fuel_Man

I'm not up on their complete operation. I know that the chips are green wet when they go into the plant, and that there is lots of steam out the stack.

There are also two mills that produce wood products in the area. One makes OSB and burns all the waste from that process, this makes steam for operating the plant. Another makes hardwood veneer and they burn the bark and waste for the operation of kilns, and steaming the logs prior to peeling. Very interesting processes. I burn their core logs when I can get them.

hot_rod

All sorts of unique ideas for fuel sources.

The Vermont State Wood Energy group published this helpful guide for renewable fuels. they talk about the types of chips and pros and cons.






http://newbiomass.com/our-products/torrefied-wood/