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Thread: Purification/Collection of Hydrogen: from a H2-Air mixed stream

  1. #1 Purification/Collection of Hydrogen: from a H2-Air mixed stream 
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    Hello everybody! I am currently finding a suitable process to separate hydrogen from a H2-Air mixture stream (in small scale). I would like to ask for some opinion or suggestions for the following situation:


    I have a mixture stream of hydrogen and air, i.e., it is composed of H2, O2, N2, and water vapor. Below is a simple illustration about the situation. Some system information are given below:
    H2-Air stream illustration.jpg
    Hydrogen production rate: 900 L/hr

    System daily operating hours: 10 hr/day


    The system described above is in small scale. The daily production can only theoretically fill 1.67 tank of cylinder (40L, 135bar H2 cylinder). I was given a task to utilize these hydrogen. The installation budget is around $20,000 USD, and operating budget should be less than $200 USD/month. I have got some ideas but each of them is having the following problems:

    1. Directly collection of the stream by pressurization and high pressure cylinder storage
    1A. The expected H2 purity would be low as it is mixed with O2 and N2. Is this kind of hydrogen useful in any kind of industrial application? (e.g. Some kinds of fuel cell that do not require high H2 purity like molten carbonate fuel cells (MCFC's) and solid oxide fuel cells (SOFC's))

    1B. Are there any simple methods to increase the purity of H2 before pressurizing it?

    2. Extraction/Purification of Hydrogen in the stream: Zeollite (molecular sieve) is famous in H2 storage, but I am not quite familiar with this material. I would like to ask:
    2A. Is zeolite a suitable mean in collecting those hydrogen?
    2B. Which type of zeolite is able to separate H2 from O2 and N2?

    2C. How can used zeolite be regenerated? How should I design this purification system? (A small scale system, maybe several equipments/piping occupying a space smaller than 2m x 2m x2m)
    2D.
    Will it be better if I separate those gases by some extra devices in addition to zeolite (say, place some water absorbing agents before zeolite to remove the water content)?


    Below is my draft proposed design:
    proposed design.jpg


    3. Combination of idea 1 and 2: hydrogen extraction by zeolite followed by filling of pressurized tank
    3A. If idea 2 does work, is it very common to directly utilize the released hydrogen during regeneration? How?
    3B. If the released H2 must be stored by some ways, is it again by pressurization? Or others?

    4. Any kinds of other suggestion


    Thank you very much for reading my passage
    Any answers are welcomed~ ~ ~


    Last edited by ingtest; October 31st, 2012 at 07:02 AM.
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  3. #2  
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    I am no expert at all... i'm only typing a post so that I notice this thread when it comes up in the new posts section and I'll be able to follow it more easily.

    Your bassically trying to extract hydrogen (1H?) from a mixture tank of H2, O2 and N2. Or you are looking for a reaction that will turn all the H2N2 and O2 into 1H?

    Is there a valvue or material that will allow 1H to pass but block H2, N2 and O2?

    Are you allowed to add anything to the mix in order to start a reaction that might turn it all into 1H?

    You need a reverse nucleosynthesis to change H2, N2 and O2 into 1H dont you?

    I wont confuse the matter any further, looking forward to hearing how you get on.

    Good luck


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  4. #3  
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    Actually, H2 just means H2, I have changed all of them just now.
    There is a stream purging hydrogen gas into the atmosphere, therefore resulting a H2-Air mixed stream. Hopefully I can separate hydrogen from air as discussed in my thread. There should be nothing to deal with isotope problem.

    Sorry for my confusing symbol, haha.
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    So when you say seperate hydrogen from air... you mean any isotope of hydrogen? including deuterium?

    Are you thinking along lines of filtration of oxergen and nitrogen in order to leave hydrogen?

    Or a chemical reaction that produces hydrogen from oxygen and nitrogen?

    Their are machines that turn air into Oxygen. Zeolites become saturated in oxygen. How this could seperate Hydrogen from air I have no clue.

    What you want surely is a chemical reaction that turns oxygen and nitrogen into Hydrogen?

    Please be aware that I am a complete novice and have no clue what i'm talking about
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    I can't help much either but ...

    Quote Originally Posted by ingtest View Post
    2. Extraction/Purification of Hydrogen in the stream: Zeollite (molecular sieve) is famous in H2 storage, but I am not quite familiar with this material. I would like to ask:
    2A. Is zeolite a suitable mean in collecting those hydrogen?
    I know zeolites are used for storage of (pure) hydrogen without requiring very high pressures but I'm not sure it would preferentially absorb hydrogen and not everything.

    Isn't the normal way of doing this by cooling the mixture so that the other gases turn to liquid, leaving the hydrogen behind?

    3B. If the released H2 must be stored by some ways, is it again by pressurization? Or others?
    Zeolite?
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by Strange View Post
    I can't help much either but ...

    Quote Originally Posted by ingtest View Post
    2. Extraction/Purification of Hydrogen in the stream: Zeollite (molecular sieve) is famous in H2 storage, but I am not quite familiar with this material. I would like to ask:
    2A. Is zeolite a suitable mean in collecting those hydrogen?
    I know zeolites are used for storage of (pure) hydrogen without requiring very high pressures but I'm not sure it would preferentially absorb hydrogen and not everything.

    Isn't the normal way of doing this by cooling the mixture so that the other gases turn to liquid, leaving the hydrogen behind?

    3B. If the released H2 must be stored by some ways, is it again by pressurization? Or others?
    Zeolite?
    Oh yea, I have thought about cooling too. I think it does work technically, but the temperature needs to be decreased to below -195oC (Boiling point of nitrogen). The profit comes from that small scale production of hydrogen probably cannot afford that much electricity consumption fee. Haha, that why the situation is difficult~~
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