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Smokestacks & Water Vapour

November 23, 2014
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By Paul Homewood  

 

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800px-Eggborough_power_station

 

Readers will recall the image of Eggborough power station used by the BBC (top), and a more conventional photo (bottom). But, regardless whether it is black or white, what is that stuff coming out of the smokestack? Surely it must be something nasty?

 

Well, not really actually. According to Wiki:

 

Flue-gas emissions from fossil-fuel combustion refers to the combustion-product gas resulting from the burning of fossil fuels.[1] Most fossil fuels are combusted with ambient air (as differentiated from combustion with pure oxygen). Since ambient air contains about 79 volume percent gaseous nitrogen (N2),[2] which is essentially non-combustible, the largest part of the flue gas from most fossil-fuel combustion is uncombusted nitrogen. Carbon dioxide (CO2), the next largest part of flue gas, can be as much as 10−25 volume percent or more of the flue gas. This is closely followed in volume by water vapor (H2O) created by the combustion of the hydrogen in the fuel with atmospheric oxygen. Much of the ‘smoke’ seen pouring from flue gas stacks is this water vapor forming a cloud as it contacts cool air.

A typical flue gas from the combustion of fossil fuels contains very small amounts of nitrogen oxides (NOx), sulfur dioxide (SO2) and particulate matter.[1] The nitrogen oxides are derived from the nitrogen in the ambient air as well as from any nitrogen-containing compounds in the fossil fuel. The sulfur dioxide is derived from any sulfur-containing compounds in the fuels. The particulate matter is composed of very small particles of solid materials and very small liquid droplets which give flue gases their smoky appearance.

 

It is of interest to note that the total amount of flue gas generated by coal combustion is only 10 percent higher than the flue gas generated by natural-gas combustion.

http://en.wikipedia.org/wiki/Flue-gas_emissions_from_fossil-fuel_combustion

 

Bearing in mind that the Large Combustion Plant Directive already puts strict limits on the amount of sulphur dioxide (SO2), nitrogen oxides (NOx) and dust particulates that can be emitted, that stuff you see coming out of the chimney is little more than water vapour.

17 Comments
  1. November 23, 2014 4:08 pm

    Paul says

    It is of interest to note that the total amount of flue gas generated by coal combustion is only 10 percent higher than the flue gas generated by natural-gas combustion.

    http://en.wikipedia.org/wiki/Flue-gas_emissions_from_fossil-fuel_combustion

    Bearing in mind that the Large Combustion Plant Directive already puts strict limits on the amount of sulphur dioxide (SO2), nitrogen oxides (NOx) and dust particulates that can be emitted, that stuff you see coming out of the chimney is little more than water vapour.

    Henry says

    Maybe it is only 10% higher than natural gas, but you have to put in additional energy to remove the poisons which do not only include sulphurous – and nitrogenous oxides but also carbon monoxide and heavy metals.

    Hence the recent statements by Shell that “when used to generate electricity, natural gas emits around half the CO2 of coal”

    More gas is the way to go….

    • November 23, 2014 5:39 pm

      Yes, I think the point is that as most of the flue gas is nitrogen, there is not much difference between gas and coal in volume

    • November 23, 2014 9:00 pm

      “…… you have to put in additional energy to remove the poisons which do not only include sulphurous – and nitrogenous oxides but also carbon monoxide…”

      Carbon Monoxide is ONLY formed when there is incomplete combustion. With stoichiometric combustion, C combines with O2 to form CO2 / carbon dioxide. (Rather than 2C + O2 >> 2CO.)

  2. Derek permalink
    November 23, 2014 4:50 pm

    If you do not believe that CO2 is a problem, As I don’t (and HenryP, if his name means anything) then coal is an excellent fuel. It is relatively cheap and plentiful. The oxides of sulphur and nitrogen can easily and cheaply be removed leaving a clean exhaust gas. If coal is good enough for the Germans and the Chinese it should be good enough for us.

  3. November 23, 2014 5:18 pm

    I am not against coal if the poisons are removed. They have to be removed because else you get acid rain. Another problem with coal is storage and keeping it dry. This is why we are currently sitting without enough electricity (South Africa).
    It seems the turnaround of the US economy is largely “fueled” by the fracking for shale gas. I have not seen the figures but I have heard that the cheapest electricity generating plant is the one that runs on gas.

  4. November 23, 2014 5:28 pm

    It is important to remember that most coal-fired power stations have de-sulphurisation plants http://tinyurl.com/km9ajnj to remove SO2. These use limestone, react with SO2 and produce gypsum which is generally purer than can be mined. It is the basis of plaster products.

    Ratcliffe, one of the largest UK power stations is a good example: http://tinyurl.com/or3xs2x

  5. November 23, 2014 5:43 pm

    A comparison: Iceland’s Bárðarbunga volcano is pumping out 35,000 tons of sulphur dioxide (SO2) per day: http://tinyurl.com/mb3qt3s Ratcliffe power station only removes ~425 tonnes per day from the flue gas.

  6. November 23, 2014 9:19 pm

    I doubt the BBC or any other organisation will show an image of a gas-fired appliance’s warm flue in operation, ‘cos there’s literally ‘nothing to see’.

    Only when the flue is cold and an appliance is fired-up, or, on a cold morning when a high-efficiency/condensing boiler emits a plume of water vapour, simply because the flue-gas temperature is very close to ambient temperature.

  7. November 23, 2014 9:33 pm

    “It is of interest to note that the total amount of flue gas generated by coal combustion is only 10 percent higher than the flue gas generated by natural-gas combustion.”

    That is an insidious statement.

    The volume might be 10% greater, but its ‘quality’ is immeasurably worse.

    Waste products from coal-fired plant include fly ash, bottom ash, and flue-gas desulfurization sludge, that contains mercury, uranium, thorium, arsenic, and other heavy metals.

  8. November 24, 2014 12:26 pm

    ben says
    https://notalotofpeopleknowthat.wordpress.com/2014/11/23/smokestacks-water-vapour/#comment-32822
    the problem has literally just vanished from existence. FAZ writer Jürgen Kaube even asks in his piece: “What ever happened to forest die-off?” –

    Henry says
    Limits were set for the exhaust for SO2 and others. Everybody in Europe eventually obliged as you could see the damage done by the acid rain. I also saw it. SO2 is POISON.
    (CO2 is not a poison, it is good for life)

    Note Jonathans comment:
    https://notalotofpeopleknowthat.wordpress.com/2014/11/23/smokestacks-water-vapour/#comment-32788

    • catweazle666 permalink
      November 24, 2014 5:04 pm

      You appreciate that far more SO2 reaches the atmosphere through natural causes such as volcanoes, oceans, biological decay and forest fires than via anthropogenic emissions, and that the threat to forests from anthropogenic emissions has been thoroughly debunked, right?

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