H2 Storage 2

[kayan]

Hi

Storing H2 is a safety concern. However, giving that a mitigation measure is put in place, what is safest highest storage capacity of H2 should be considered?

Regards,

 

[Montemayor]

Kayan:

You're right. Hydrogen, like any other fuel, should be a safety concern. However, I don't know what "mitigation" measure you are talking about putting in place and I also don't know what state of Hydrogen you are working with. Liquid Hydrogen is a common, ordinary bulk commodity supplied all across the USA by such companies as Air Liquide, Air Products, Praxair, etc. This liquified product is normally vaporized at the use site employing ambient vaporizers. Smaller consumption capacities are delivered as high pressure gas in tube trailers and cascaded down from a conventional pressure of 3,500 psig to consumption pressures. Which system are you talking about?

I also don't understand your classification of the safety issue as hinging on the size of the storage facility. Gaseous H2 will burn with the same temperature and flame size depending only on the type & size of excape that it finds from the storage system - regardless of the size of the storage system itself. Could you please specifically explain what you conceive to be your safety problem?

Are you concerned with an explosion, rather than a fire involving hydrogen?

 

[kayan]

Montemayor

The intent is to pressurize vapor H2 upto 200 Barg and then store it in high pressure cylinder. The mitigation measure would be e.g. leak detection, special pipe to prevent the leak. However, i have been told that H2 leak is difficult to avoid because of its diffusivity.

The safety concern is fire potential upon leakage given its low energy requirment for fire. Worst than that is H2 Explosion.

What i am after is the magnitude of imposed safety risk of having storage of 1.8 ton vs. 3 ton of H2?

Regards,

 

[Ashereng]

kayan,

Here is 2 cents worth of another angle.

If a 1.8 ton H2 storage vessel blows up, what radius will it affect? Or 3 tons?

How much H2 do you need? Does it all have to be stored in the same location, in the same vessel?

How about 8 x 1/4 ton H2 vessels instead of 1 x 2 tons vessel? (Implied is that the vessels are out of each other's blast zone).

 

[kayan]

Ashereng

The actual requirment is 3 ton. Yes it has to be stored in the same location but not in the same vessel.

Regards,

 

[Montemayor]

Kayan:

The fact that H2 is either the 1st or 2nd smallest molecule in the Universe is an outstanding cause of its diffusivity - through steel pipe walls. I and others have discussed this and other safety concerns in many threads spread out through these Forums in the past. Compressing H2 gas to 200 barg is nothing extraordinary. It's done everyday in thousands of installations around the world - and that's been going on since before I got into engineering 46 years ago. So I can categorically state that you don't have an exceptionaly safety problem on your hands - thank God.

If you are a Chemical Engineer you will understand my next statement. There is as much explosion concern in this application as there should be every time we drive up to a gasoline station to fill up our automobile's gasoline tank. In a gasoline station we park our cars literally on top of various underground gasoline storage tanks while we expose ourselves to gasoline vapors emitted during the operation - and which could cause an explosion. And yet, this is done millions of times a day probably - and by people who don't have the slightest idea or concept of what vapor pressure is and what is going on. I can assure you that the industrial storage of gaseous Hydrogen at 200 barg is far safer that your normal gasoline station operation.

There is no "imposed safety risk of having storage of 1.8 ton vs. 3 ton of H2" as you state. Anyone trying to quantify the difference is wasting their time when they should be concentrating on a totally safe installation - not because of its size, but because of its inherent design. If you are going to stick to your allegation or inference that there is a difference in safety due to capacity size, then the best and safest installation you can do is NO INSTALLATION. That should be 100% safe.

Hydrogen needs an oxidant to explode. It doesn't decompose on its own. Presumably you are not adding oxidants to the H2, so please explain how you conceive that an oxidant could accidently migrate into a bank of isolated H2 tubes at 200 barg? Not likely, but then I haven't seen your tube bank design.

 

[owg]

The folks who design rocket motors have been handling fairly large volumes of hydrogen for many decades. They have had at least one large explosion. You could look into that area of technology.

HAZOP at

http://www.curryhydrocarbons.ca