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Campaigning with electric cars.

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Oatsandbeans View Drop Down
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Post Options Post Options   Quote Oatsandbeans Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 5:58pm
I work with hydrogen a lot and it isn't as bad as solvents for flammability- we have never had any issues. It needs much higher temperatures to set it off ( 600C. cf. 300C. from memory}.
The great thing is it is much lighter than air so if you design your system correctly and get it to vent upwards it clears very quickly unlike fumes from petrol.
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 5:54pm
Coal slurry apparently a good fuel for ships, found out about coal slurry when researching coal dust engines.
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Post Options Post Options   Quote Dangerousday Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 5:48pm
LEL for petrol / hydrogen aren't that different
But quite agree the range is quite different due to the UEL being 10x higher for hydrogen, and the energy requirement.
I was thinking more of long term effects of it. Benzene link to cancer (think some US States have pumps that draw vapour away from the nozzle?) and dermatitis, rather than glugging the stuff.
On which, I stink of diesel at the moment - just been inspecting an empty 300m3 that was full of it. Hydrogen? - can't really see a ship running on it.

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Post Options Post Options   Quote pondlife1736 Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 4:58pm
Originally posted by Dangerousday

Petrol flash point is -43 C so though, yes, it does have to be a vapour before it will ignite, practically there aren't that many places on Earth where it won't.
Quite possibly the most dangerous substance both for being flammable and the nasties it contains that anyone deals with regularly.

Well I agree with your first statement at least. If it didn't have that low flash point our petrol cars wouldn't start in Winter (or at least not without glowplugs like diesels).

But there are other factors, most significantly the air fuel ratio range it will burn. For petrol it is quite narrow. There is that anecdote about throwing a lighted match into a bucket of petrol and watching your mates run for cover while the match fizzles out. It's because the petrol vapour / air mixture at the surface is outside the combustible range. (Don't try this at home though kids.....)

Compare this with hydrogen which will combust in a very wide range of air fuel ratio, and which requires very little ignition energy to do so - a tiny spark or heat source is enough to set it off. Combine that with its propensity to leak from anywhere and everywhere and I consider it to be far more dangerous. How could it be worse? I know, put it in close proximity to a 600 volt car electrical system.

Petrol isn't even that toxic - ok I don't suggest you drink it  - but there are hundreds of liquid hydrocarbons out there that are far worse.
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 1:19pm
Always been a bit careful WRT petrol and wouldn't usually use it as a solvent (that's not saying I never have.....). Most domestic (and commercial) thinners are rather less volatile though there exceptions (Toluene being one I believe). Stuff like meths, paraffin and white spirit are somewhat less flammable. But they should all be handled with a modicum of caution.
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 12:56pm
Can remember years ago using petrol for thinners and cleaning paint brushes etc, loads of products in normal household use flammable, aerosols, seen horrific video on the news some years ago of a guest at a wedding badly burnt when silly string being sprayed on her exploded, we are surrounded by dangerous products,
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Post Options Post Options   Quote Dangerousday Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 18 at 12:36pm
Petrol flash point is -43 C so though, yes, it does have to be a vapour before it will ignite, practically there aren't that many places on Earth where it won't.
Quite possibly the most dangerous substance both for being flammable and the nasties it contains that anyone deals with regularly.
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Post Options Post Options   Quote pondlife1736 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 18 at 5:41pm
Originally posted by Oatsandbeans

Hydrogen pressure vessels taking 700bar are available right now in type 3-( metal liner with carbon overwrap) and the costs are falling as they become commercialised and volumes increase. They will only get lighter and lower cost and higher pressure, as they sort out the next generation plastic liner carbon over-wrapped cylinders. So I Think that in 10 years we may have hydrogen powered cars driving around. I haven't looked at the numbers but you would have to think that it would be more energy efficient than batteries, and hydrogen isn't as hazardous as some people think -it takes quite a bit to make it go bang compared to petrol for example.

I'm sure the victims of the Hindenburg disaster would disagree strongly!
In fact hydrogen is an order of magnitude more flammable and explosive than petrol. Being a liquid, petrol has to be vaporised before it will burn, so is inherently safer.

You can buy a hydrogen fuel cell car today if you wish, but it really makes no sense without a developed infrastructure. I find it hard to believe that a robust, rupture-proof high pressure tank and fuel handling systems plus that fuel cell will ever be lower cost than a battery, but who knows. Whatever, the auto industry did its sums and concluded that the future was electrification via batteries. The choice is made for us. 
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Rupert View Drop Down
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 01 Dec 18 at 7:32am
Hence the waterfall, as freeish energy on a small scale.
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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 18 at 11:05pm
Lots of Hydrogen, problem is it's always joined to something else, Carbon and Oxygen mainly, you can seperate from Oxygen using electricity passed through water, known as 'Browns gas' needs more energy to create than gained

Edited by 423zero - 30 Nov 18 at 11:06pm
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