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I'd dismissed this one as a stupid idea...
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Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Dec 07, 16 2:43 pm    Post subject:  Reply with quote    

How much Nitrogen do you need for how much ice cream?

{Why am I trying to talk myself into this?}

Nick



Joined: 02 Nov 2004
Posts: 33629
Location: Hereford
PostPosted: Wed Dec 07, 16 3:07 pm    Post subject: Reply with quote    

It's not precise. A quick pour to make enough for the lab.

I'd guess 300ml to make a litre.

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Wed Dec 07, 16 3:51 pm    Post subject: Reply with quote    

Nick wrote:
It's not precise. A quick pour to make enough for the lab.

I'd guess 300ml to make a litre.

Does it scale up well enough?
If I build this thing I'll be wanting to make it by the gallon...

dpack



Joined: 02 Jul 2005
Posts: 32752
Location: yes
PostPosted: Wed Dec 07, 16 4:21 pm    Post subject: Reply with quote    

on a commercial dairy scale (loseley) they put about 30 gallons of mix in a big pot and pull a handle to add l n down a pipe from a storage tank which iirc is topped up from a road tanker rather than made on site. they were making a few thousand gallons a week so perhaps to justify making your own l n you would be looking at quite a large scale operation.

the handle thing does make the process safer than free pouring (humans at minus 200 crack as well as rubber gloves and flowers )

Mistress Rose



Joined: 21 Jul 2011
Posts: 8606

PostPosted: Thu Dec 08, 16 7:06 am    Post subject: Reply with quote    

We had a delivery of liquid nitrogen from a tanker for our clean room too. We used the boil off as an inert atmosphere for various jobs in a glove box.

Shane



Joined: 31 Oct 2005
Posts: 3033
Location: Doha. Is hot.
PostPosted: Sun Dec 11, 16 9:35 am    Post subject: Reply with quote    

Hairyloon wrote:
dpack wrote:
reality check

any attempts at compressing flammable gasses are fraught with danger...


My thinking was to produce liquid air and use that to chill the methane rich atmosphere to condense the methane: practically no compression involved.

Though not thinking seriously about it as I don't have a cowshed...

Sorry - bit late to this one. It's a lot harder to have a browse since the work net nanny decided that Downsizer was an inappropriate website

Suggest that your plans to liquefy methane at atmospheric pressure may be slightly challenged by the -161 degrees that you'd have to get down to in order condense it. You'd have rather a lot of other liquids drop out on the way that you'd have to deal with before you started dropping out methane - my recommendation would be to use what you can to top up the mixed-refrigerant system that you'd need to supply your cryogenic heat exchanger (do let me know how you get on with designing one, by the way - there's only two companies in the world that make them and they keep their respective designs a closely-guarded secret. Try as I might, I can't replicate them). Oh - and although you only need minimal compression for the methane (downstream of purification, at least), you'll need significant compression power to drive your refrigerant circuit.

And as for storage - good luck, is all I can say.

Do let me know how you get on

Mistress Rose



Joined: 21 Jul 2011
Posts: 8606

PostPosted: Sun Dec 11, 16 11:37 am    Post subject: Reply with quote    

We might hear the bang to tell us Shane. Not really a goer I wouldn't think, but the output of methane from cowhouses and landfill sites is probably sufficient to be useful if only it could be harnessed. Digesters are now being used for slurry and some rubbish, which was an idea I had a long time ago, but didn't have the expertise to do anything about.

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Sun Dec 11, 16 1:50 pm    Post subject: Reply with quote    

Mistress Rose wrote:
Digesters are now being used for slurry and some rubbish, which was an idea I had a long time ago, but didn't have the expertise to do anything about.

Digesters are easy enough: shove enough crap in a bucket and off it goes...
There is a lot more to it if you want to optimise the process, but my initial test with a couple of buckets worked fine.

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Sun Dec 11, 16 2:24 pm    Post subject: Reply with quote    

Shane, did you look at the design on Instructables?
It's a few posts back...

Shane



Joined: 31 Oct 2005
Posts: 3033
Location: Doha. Is hot.
PostPosted: Tue Dec 13, 16 4:13 am    Post subject: Reply with quote    

Oh yeah - just found it. Looks like a fun rig.

There's a big, big difference between nitrogen and methane. One disperses almost immediately (and I would recommend that you never put a liquid nitrogen generator in a shed), one is very, very flammable indeed and will ignite in a catastrophic manner if it leaks.

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Dec 13, 16 9:37 am    Post subject: Reply with quote    

Shane wrote:
Oh yeah - just found it. Looks like a fun rig.

There's a big, big difference between nitrogen and methane. One disperses almost immediately (and I would recommend that you never put a liquid nitrogen generator in a shed)...

Where else should I keep it when it's not in use? Is too big to go in the basement.

I'm not clear why you are pointing that out either: they are obviously very different...
But thinking on, if you're gradually chilling air 'till it liquefies, then isn't the methane going to drop out first, followed by the oxygen...
I imagine a bucket with a mix of liquid methane and oxygen is not a good thing to have...

dpack



Joined: 02 Jul 2005
Posts: 32752
Location: yes
PostPosted: Tue Dec 13, 16 12:44 pm    Post subject: Reply with quote    

"I imagine a bucket with a mix of liquid methane and oxygen is not a good thing to have..."

ummmm, set up the camera at a respectful distance before you try.

i'm not sure it is even possible to get to the bucket stage in your shed.

this crew dont mention buckets

it lives in a slightly bigger incarnation , still no buckets

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Dec 13, 16 1:04 pm    Post subject: Reply with quote    

dpack wrote:
this crew dont mention buckets

But they do mention a spark plug: it seems they don't expect it to go off spontaneously...

Nick



Joined: 02 Nov 2004
Posts: 33629
Location: Hereford
PostPosted: Tue Dec 13, 16 1:23 pm    Post subject: Reply with quote    

No one who blows themselves up expects it to combust spontaneously, I guess.

Hairyloon



Joined: 20 Nov 2008
Posts: 14696
Location: Today I are mostly being in Yorkshire.
PostPosted: Tue Dec 13, 16 1:41 pm    Post subject: Reply with quote    

Well, there is a 20 degree difference in boiling points and I can't believe the chiller works that fast, so it should be easy enough to run them off into separate buckets...

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