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How can I remove steam from exhaust gases?

  1. Mar 2, 2015 #1

    I have hot gases with steam (water) inside
    how do I seperate it ?

    without cooling it

    magnetic field can help?
    something else?
  2. jcsd
  3. Mar 2, 2015 #2
    What kind of gas is mixed with the steam and why can't we cool it?
  4. Mar 2, 2015 #3
    exhaust gas from internal combustion engine
    I want it as hot as possible to react with the catalyst
    at the same time I want it without water/steam
  5. Mar 2, 2015 #4


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    It's not clear what sort of reaction you want to accomplish with the help of the catalyst.

    BTW, automobiles equipped with catalytic converters as pollution controls work just fine without removing water vapor from the exhaust stream before it enters the converter.
  6. Mar 2, 2015 #5
    I don't think theirs another way except condensation or find a membrane or chem that's hydrophilic, maybe pressure.
  7. Mar 2, 2015 #6

    jim hardy

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    You've made contradictory statements

    do you want to separate water from steam as in title of thread

    or do you want to separate H2O from another substance as inferred in posts 1 and 3 ?

    Removing water from steam is often done mechanically by abruptly changing its direction, look up "chevron steam dryer" .
    Chemical separation is another story....
  8. Mar 3, 2015 #7
    the reaction that the catalytic converter does!

    I know they work without having to remove the water vapor, but I would like to remove the water vapor!
  9. Mar 3, 2015 #8
    I want to remove H2O from exhaust gases, which H2O is obviously in the form of steam/vapor there!
  10. Mar 3, 2015 #9


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    Can I ask why you want to do this?

    Perhpas a desiccant would work.
  11. Mar 3, 2015 #10
    I want to do it as a project
    to dehydrate exhaust gases of internal combustion engines
    Last edited: Mar 3, 2015
  12. Mar 3, 2015 #11
    desiccant is not sustainable, I need a way that is sustainable
  13. Mar 3, 2015 #12
    why can't I take advantage of this phenomenon:

    to seperate all the water molecules from the exhaust gases?
  14. Mar 3, 2015 #13
    I'm not a combustion expert, but that's only good if all the exhaust molecules are non-polar except the water. Plus, do you really need the steam separated badly enough to create a static E field inside your exhaust pipe?
  15. Mar 3, 2015 #14
    it's an experiment, it's not going to an actual car

    is the video I posted amazing?

    did you know that?

    I didn't, although I was expecting it

    the question is how much forcefield I need, to grab molecules and accelerate them?
  16. Mar 3, 2015 #15


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    Staff: Mentor

    Isn't your teacher/professor going to ask why?
    What do you mean by "sustainable"?
    I'm not sure how you would actually utilize that.
  17. Mar 3, 2015 #16


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    Usually one would remove water droplets from wet steam mechanically, through steam dryers.

    However, since the water vapor (steam) is intimately mixed with CO2, CO, NOx, SOx, one would have to remove it via a dessicant as Russ indicated, or centrifugally (separation of molecular mass variation), which would require a lot of power (energy) and would probably penalize the IC power generation.

    Fossil fuel power plants use scrubbers to preferentially remove pollutants. Steam (water vapor) is usually considered acceptable to release into the atmosphere.
  18. Mar 8, 2015 #17
    You can do the same thing with a plastic comb you run through your hair or a balloon your rub on your head.
  19. Mar 9, 2015 #18
    Right after the catalytic converter, the exhaust gas temperature drops significantly even if there is still some exothermic reaction from CO and HC oxidation. Once the exhaust gas passes the catalytic converter, you can use a low temperature heat exchanger to bring the exhaust gas below 100C though you may want even lower than 100C.

    In internal or external combustion engines equipped with water injection, it is good to recover the spent water and filter it before it goes back into the engine. Message me separately if you want to discuss this further outside the forum
  20. Mar 9, 2015 #19
    according to me drier will be the best option
  21. Mar 9, 2015 #20

    Mark Harder

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    Look up Water Gas and the Water Gas Shift Reaction. 'Water gas' is a mixture of CO and H2 made simply by passing high-temperature steam over red-hot carbon. If you make it this way, the carbon will be used up, but carbon in the form of coke (not the soft-drink, it's the stuff used to smelt iron in a blast furnace) is a plentiful (and I think cheap) ingredient. Perhaps there is some spot in the exhaust stream that is hot enough. The idea is that the CO and H2 can be then oxidised by a suitable catalyst, perhaps in the cat converter itself. This latter reaction should be exothermic, which might be used to supply heat to the water gas generator(?).

    The water gas shift reaction is this reaction: CO +H2O = CO2 + H2. The CO is oxidised to CO2 and the H2O is reduced to H2. Since you have both CO and H2O in your exhaust stream, the reaction should be a no-brainer. The fact that the water somehow escapes reacting with carbon monoxide in the internal combustion exhaust stream suggests to me that a catalyst will be needed to promote the reaction. Perhaps this needs to be something different than the PGMs in the standard cat converter. You'll have to look it up yourself. I'm no chemical engineer. But this solution meets the difficult requirements of sustainability and no low T condensation. In theory at least.
  22. Mar 9, 2015 #21

    Mark Harder

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    P.S. To my previous reply:
    I looked up the shift reaction in Wikipedia and learned that the equilibrium constant has a negative response to temperature. At T>1000K, it's ≤1. On the other hand, the products are swept away by the pressure gradient in the pipe, so the reaction will be 'pulled' toward the products, i.e. it can achieve some sort of steady-state over the catalyst (I think). The catalyst is a mixture of Fe2O3, Cr2O3 and a pinch of MgO, all very common and cheap ingredients.
  23. Mar 9, 2015 #22
    Mark for water to be converted to H2, you will need a lot of energy. Exothermic reaction at the catalytic converter is far from enough or it will sinter the precious metal the the monolith.

    Bear in mind also, in a complete combustion, water is just a small percentage if compared to the CO2 and unreacted N2.
  24. Mar 9, 2015 #23


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    In complete combustion, water is one of the primary components of the exhaust stream. What it lacks, though, is a significant amount of CO.
  25. Mar 9, 2015 #24
    You can get enough co by injecting rich upstream. Still if you have lots of nitrogen in the exhaust stream the conversion efficiency will drop. Frankly, just cool off the exhaust gas stream after the catalyst is a much simpler option. I have published papers on this
  26. Mar 12, 2015 #25


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    Unfortunately, a chevron steam dryer removes water condensate from the steam flow but does not remove steam.

    When you consider the products of the combustion of hydrocarbons in air you get predominantly N2, H2O and CO2. The molecular weights are H2O=18, N2=28 and CO2=44.

    If you then use a bank of gas centrifuges you will be able to separate those three gasses.

    A fast cyclonic separator would create a lower pressure at the centre, that would result in local condensation of the water component along the axis. The density of that water as a condensate would then be higher than all the gasses involved and so it would be thrown back out to the higher PT region where it would go back into solution. It might be possible to intercept and collect that liquid water condensate as it departs the central axis to move outwards. That could be an application for a chevron steam drier.
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