From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Saturday, May 25, 2019 10:30 AM
Subject: Re: [QRPLabs] Where can I buy floater balloon?
Excellent answer, thanks for taking the time to explain this!
As I understand it, in summary, H2 combines with trace water vapor to form Hydronium,
and Hydronium can react with the hydrocarbons in grease.
Sounds like this could happen at room temperature and atmospheric pressure.
One often hears of the dangers of grease on oxygen regulators and valves.
I see references on the web stating one should never use grease on any regulators,
but assumed this was just generalizing the rule regarding grease around oxygen
to make it easier to follow. But apparently this also applies to at least hydrogen.
(There are special greases not based on hydrocarbons that can be safely used.)
A few questions:
> Hydrogen gas leaking into external air may spontaneously ignite.
That could be nasty, we need to drill down a bit on that one.
Under exactly what conditions may it spontaneously ignite?
Does this apply when working with a cylinder of hydrogen using a regulator
to bring it down to a few psi? 40 psi?
Or does it only apply to high pressure H2 discharges of 1000+ psi?
Well this depends on the activation energy for the pathway the molecules take to ignite. It’s pretty much linear in pressure (the Arrhenius function for H2 combustion is multiplicative in H2 concentration… and concentration is proportional to pressure. See this reference: https://www.chemguide.co.uk/physical/basicrates/arrhenius.html). This can occur at near zero pressure… just slower than if it’s at elevated pressure. If it’s via a hydronium ion, it won’t work without at least trace water molecules and then temperatures above the freeze point of water. That was probably obvious. However, other modes that are possible by just heat or heat plus a catalyst are way more difficult to predict. Completely dependent on the catalyst type (steel, aluminum, rare earth metal, etc.). Here is a general discussion of catalysts:
https://en.wikipedia.org/wiki/Catalysis Using the right catalyst, the reaction path can take place at almost any temperature and pressure. Therefore you may not even be safe with H2 brought through a regulator in very cool conditions.
> You could literally walk into an area with leaking H2 and only feel heat,
> and because H2 is generally under pressure, it can act like an invisible
> blow-torch that an unsuspecting victim may find too late.
Can we assume that if our H2 is not more than 40 psi above ambient pressure
and has no significant oxygen in the mix, the danger is minimal?
At 40 psi, is there any danger in using plastics such as polyethylene, PVC,
or polycarbonate to contain H2?
I would say the danger is minimal without any O2 or water. Also, blowtorching occurs with elevated pressure H2 only…. The same mechanics as you would use for a butane, propane, or acetylene torch. A few pounds won’t mean much.. but once you get up two atmospheres (15 PSIG), torching will begin and just get worse with pressure. PVC is interesting here… I don’t know if the matrix is small enough to contain H2 or not… the thing to investigate here is the average bonded structure size versus the diameter of the H2 molecule. My wild guess is that it will not contain H2… and may replace some bonds causing it to break over time. Mylar actually does contain H2. Evidently the bonded structure of Mylar is smaller than H2.
These are quick answers as the family is calling to go out on this beautiful holiday weekend! Enjoy.
On Thu, May 23, 2019 at 09:46 AM, J68HZ wrote:
Just back from traveling so now I can answer this… Please excuse and delete if this topic is o no value to you…
There are several mechanisms by which Hydrogen (H2) can react and the mere reaction by one mechanism can avalanche into others at a rapid pace. H2 is at the top of the list of what is called Brostead Lowry acidic proton donors… so if there any trace of moisture nearby, H2 + 2H2O forms 2H3O+, called Hydronium, which is an extremely reactive acid. It’s formation is catalyzed (meaning the activation energy for formation of the specie is drastically lowered by) metals; noble metals give the lowest activation energy…(this is all equationally captured by Arrhenius rate chemistry that I will not go into here)… but aluminum and steel are still fine catalysts that can lower the temperature of formation from about 500C as required to happen spontaneously, to about 3C with a suitable catalyst. Once formed the Hydronium will attack anything neutral or negatively charged with enormous energy release… including oxygen in the air… which is electron rich. (nb. Refineries use metals like platinum, nickel, and rhodium on supports like diatoms as a catalysts in their unit ops, but control the reaction rate with temperature, pressure, and reacting reagent concentration). Pure hydrogen burning in air emit ONLY ultraviolet waves (non-visible to the human eye), and thus ultraviolet glasses or some sort of ultra violet detectors are used to tell if there is danger in commercial plants. You could literally walk into an area with leaking H2 and only feel heat, and because H2 is generally under pressure, it can act like an invisible blow-torch that an unsuspecting victim may find too late.
So how does this self-ignite with hydrocarbons? A hydronium ion is constantly seeking sources of electrons to neutralize. Carbon rich hydrocarbon chains like grease will make an ideal source of fuel for such molecules which react could violently, but most often is controlled by diffusion of Hydronium in air. In this case, flames from the burning hydrocarbons are blue (smaller molecules like butane) to yellow in color (pentane and to decane) or even black (C10+). The reaction needs no catalyst because the activation energy is negative signed at ambient temperatures and pressures. H3O+ and HxCy… form H2O plus a number of fractional hydrocarbons from the burning process.
An additional note (from other sources); H2 can dissolve in many metals, leak out, and have adverse effects on them, like hydrogen embrittlement that leads to cracks and explosions. Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns
1. "Liquid Hydrogen MSDS" (PDF). Praxair, Inc. September 2004. Archived from the original (PDF) on 27 May 2008. Retrieved 16 April 2008.
2. "'Bugs' and hydrogen embrittlement". Science News. 128 (3): 41. 20 July 1985. doi:10.2307/3970088. JSTOR 3970088.
3. Hayes, B. "Union Oil Amine Absorber Tower". TWI. Archived from the original on 20 November 2008. Retrieved 29 January 2010.
4. Walker, James L.; Waltrip, John S.; Zanker, Adam (1988). John J. McKetta; William Aaron Cunningham (eds.). Lactic acid to magnesium supply-demand relationships. Encyclopedia of Chemical Processing and Design. 28. New York: Dekker. p. 186. ISBN 978-0824724788. Retrieved 20 May 2015.