RogueRose
International Hazard
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Registered: 16-6-2014
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Production of H2SO4 from burning coal? SO2 + O2 + H2O?
Many coals have a high sulfur content and I know SO2, NOx and CO2 are usually byproducts of combustion. I know with the "clean coal" initiative they
use various types of scrubbers to remove the gases from the exhaust. One of the main methods is by passing the exhaust gases through a mist/spray of
water which (especially when O2 is present) absorbs the SO2 and NOx gases.
With the vast amount of coal burnt per minute in the country, I would think this could be a significant source of H2SO4 and what is done with the
captured water/acids after scrubbing is what I am trying to find out.
I've heard that the result of the scrubbers is considered "toxic waste" or "hazardous" and this is one of the reasons why they claim "clean coal" is
expensive.
Now H2SO4 is produced industrially by burning sulfur in presence of O2 and passing through water - so the result is basically the same as the
scrubbing "waste" (minus the NOx compounds). The big question is how can something be considered a "toxic waste" (in the coal scrubbing) when it is
produced on a massive scale in its own "solitary"/dedicated process.
So my question is if the output of the scrubbers is H2SO4, can it be used for anything as it has some NOx contaminates? How could the NOx's be
cleaned? Or could the scrubber acid be used to make Nitric acid industrially?
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Fulmen
International Hazard
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I don't think you understand the complexity of the situation.
From http://www.ucsusa.org/clean-energy/coal-and-other-fossil-fue...
"Waste created by a typical coal plant includes more than 125,000 tons of ash and 193,000 tons of sludge from the smokestack scrubber each year...
Toxic substances in the waste—including arsenic, mercury, chromium, and cadmium"
Part of the problem is that sulfur isn't a valuable resource. The petroleum industries produce millions of tonnes each year, so it's basically a
waste.
We're not banging rocks together here. We know how to put a man back together.
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CuReUS
National Hazard
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The contact process needs a catalyst,which can get poisoned due to the impurities in the coal exhaust.
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RogueRose
International Hazard
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Quote: Originally posted by Fulmen  | I don't think you understand the complexity of the situation.
From http://www.ucsusa.org/clean-energy/coal-and-other-fossil-fue...
"Waste created by a typical coal plant includes more than 125,000 tons of ash and 193,000 tons of sludge from the smokestack scrubber each year...
Toxic substances in the waste—including arsenic, mercury, chromium, and cadmium"
Part of the problem is that sulfur isn't a valuable resource. The petroleum industries produce millions of tonnes each year, so it's basically a
waste. |
I know the ash is a big issue. I'm curious if the cadmium, mercury and chromium make to the flue gases or if it is mainly the gases previously
mentioned. I'm sure the fly ash mixes with the water and gases and that is probably the sludge of which you speak - I hadn't thought about that.
Having the sludge be acidic, I can now see what the issue is and it is much more complex than some of the diagram's I've seen.
Thanks for the reply!
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Fulmen
International Hazard
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I don't know, some fly ash is clean enough to be used in cement. In fact it's become an important resource as fly ash can increase strength and
prevent unwanted reactions with sulfide-rich aggregate.
We're not banging rocks together here. We know how to put a man back together.
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