Compressing Hydrogen

[Storker]

Blending by molar mass... hydrogen is approximately 2.014 grams per mole while for oxygen it's approximately 15.9994.

No. No, no, no.

Unless you're comparing molecular hydrogen with atomic oxygen, but only the noble gases (He, Ne, Ar et al.) are found in their monoatomic state.

H has an atomic mass of 1.008 g
Gaseous hydrogen, H2, has a molar mass of about 2.016 g
O has an atomic mass of 15.999 g
Gaseous oxygen, O2, has a molar mass of 31.998 g

So 24.79 liters of H2 at 1 bar and 25 degrees C masses 2.016g, and 24.79 liters of O2 at 1 bar and 25 degrees C masses 31.998g, not 16g!

Wouldn't it be kinda embarrassing to blend and end up with half the FO2 you were aiming for, just because you mixed up molar mass and atomic mass?

 

[Storker]

I saw the same error in my CMAS gas blender textbook, issued by the Danish Diving Federation DSF. At that time, I naturally assumed that it was just the Danes who had messed up. But now I wonder where else they're teaching that heresy.

To the Danes' credit, it took them only a few days to publish an erratum when they were notified.

 

[giovyledzep]

If your planning on breathing hydrogen in a breathing mixture first you need to verify the method of the hydrogen production. Current available high pressure hydrogen gas has two very dangerous compounds associated with its production that are fine for the main applications for hydrogen but are extremely dangerous from a point of breathing them at depth.

Second none of the major gas producers and suppliers are in a position to advise you on the safe PPM limits of these two compounds or indeed the ppm levels within the hydrogen gas, because unless your breathing it there is really no reason to analyse for them in the first place.

Third Neither are any hyperbaric doctors I am aware of either.

Its a catch 22. You need the background experience and knowledge to even begin to know where to begin
and those who do know are all ex offshore diving engineers and they dont get a look in now a days because anything to do with diving on this forum is controlled by medical moderators. And all your hard work submittd photo's and answers will be deleted as it was when we last discussed IWR on this forum.

So I dont see this topic getting much above a dead swedish dude that has a medal named after him and folk posting pictures of some balloon on fire.

If you want sub 250 MSW for my money neon would be an easier option to kick off with either way we wont get chance to discuss it fully either as we are already way past Tekdive 2020 or other some such forum bandwidth limit.
PS if you need to know how to compress hydrogen safety try the compressor section located in the backwater of these forum pages no one bothers looking for us down that deep. Iain

Understood, makes sense.

IWR is definitely an interesting topic. My opinion is that we should [ C E N S O R E D ]

(PS: that was a joke)

 

[Doppler]

I saw the same error in my CMAS gas blender textbook, issued by the Danish Diving Federation DSF. At that time, I naturally assumed that it was just the Danes who had messed up. But now I wonder where else they're teaching that heresy.

To the Danes' credit, it took them only a few days to publish an erratum when they were notified.

Thanks for the correction... I'm blaming lack of coffee.

However, let's hope our little discussion raises the OP's curiosity and level of alarm! LOL!

 

[Storker]

I'm blaming lack of coffee.

That's what I usually do, too.

 

[iain/hsm]

For compressing I would be looking at a used CNG compressor. The design is for compressing natural gas to very high pressures without leaking any to the outside nor blowing itself up.

Now the blending part, please leave notes of what you tried a long way from where you are doing it. that way if something goes wrong we have some idea of what to never try again.

I really would not suggest using a used CNG compressor for anything to do with breathing gas applications.
Even compressed air. CNG is such a filthy gas you will never clean the used compressor enough to use it for breathing air let alone a Hydrogen mix. Iain

 

[iain/hsm]

first, don't do it, it's really dangerous. IF you're going to do it, please use something designed for boosting hydrogen. Haskel does make boosters designed for compressing hydrogen for reference

Too late I've already done it. Its a pretty straighforward mechanical process with a few considerations bolted on for this specific application. As for the Haskel it's only just OK if your using Hydrogen for vehicle fuel applications.

If you wish to breathe the stuff can I suggest we start by using a proper compressor

 

[iain/hsm]

But now I wonder where else they're teaching that heresy.
.

Look no further than this very forum. If you post something that may affect a certain medical moderators tecdive lecture circus or suggest something he doesn't like, you will get your post deleted by a fellow moderator acting as his lacky. Hence why on an interesting post make for yourself a pdf copy.

But moving on I have first assumed the OP would be compressing a Helium Nitrogen Hydrogen mixture
so in addition you need to know the cohesive force constant (Van der Waals) the Density, the oil water separation coefficient, and the solubility in oil (if you ever dare attempt this using an oil lubed compressor)

For its breathing gas application in addition to the above you would also need to know the thermal conductivity and the narcotic (Brauer) classification for the breathing gas

Later I suggest we look at those critical gas purity aspects sugested earlier. But to kick off.

For the compressor aspects:
The Cohesive force constant Van Der Waals: Hydrogen 0.244 / Helium 0.034 / Nitrogen 1.390
Oil Water Separation coefficient : Hydrogen 3.10 / Helium 1.70 / Nitrogen 5.25
Solubility in Oil (at 37 deg C compressor output) ml.1 ~1: Hydrogen 40 / Helium 15 / Nitrogen 67

For the breathing gas aspects:
Narcotic Brauer Classification: Hydrogen 0.26 / Helium 0.07 / Nitrogen 1
Thermal Conductivity (W.(m.C~1) Hydrogen 40.21 / Helium 34.07 / Nitrogen 5.61

 

[Storker]

Look no further than this very forum. If you post something that may affect a certain medical moderators tecdive lecture circus or suggest something he doesnt like, you will get your post deleted by a fellow moderator acting as his lacky.

If you have issues with moderation practice, it's generally recommended to take it up in Site Support | Feedback instead of sniping in a thread which has nothing to do with what you're complaining about.

 

[tbone1004]

Too late I've already done it. Its a pretty straighforward mechanical process with a few considerations bolted on for this specific application. As for the Haskel it's only just OK if your using Hydrogen for vehicle fuel applications.

If you wish to breathe the stuff can I suggest we start by using a proper compressor

comment wasn't directed at someone like you who is an engineer that designs compressors.
To your second point, I wouldn't have the balls to use it in an oiled compressor, so it would be Rix or if already using pressurized hydrogen, the Haskel wouldn't really bother me.