[AR] Re: Removing Coking Deposits
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 18 Sep 2016 22:20:54 -0400
On Sun, Sep 18, 2016 at 04:35:20PM +0100, Peter Fairbrother wrote:
On 18/09/16 03:24, Norman Yarvin wrote:
Note that "trike" was commonly 1,1,1-trichloroethane, until it got
banned for depleting the ozone layer.
It isn't actually banned per se; just manufacturing it, using it for
most purposes, and selling it in most cases are banned.
That stuff was relatively safe;
indeed, it's safety (non-reactivity) was likely also why it lasted
long enough to reach the ozone layer.
Except that it doesn't really reach the ozone layer, at least not in
significant quantities - unfortunately it is still listed as a class 1
ozone depleting substance, even though it is now known not to be one.
More, it's atmospheric life is only about 6 years. Continued small-scale
use would have no detectable effect on the ozone layer, but this is not
allowed.
How do you have something with an atmospheric life of 6 years and yet
which doesn't make it to the ozone layer?
For that matter, the stuff is such a good solvent that prior to the
ban it had been made in quantities of (from memory) something like a
million pounds a year. If the ban (or near-ban) were lifted, I'd
guess there would be more than just "small-scale" use. I'd certainly
run out and buy some.
(I read at some point that the rather-quick recovery of the ozone
layer after the Montreal Protocol was adopted was attributed to the
phaseout of 1,1,1-trichloroethane in particular: refrigerants such as
R12, with their longer half-lives, could not have been responsible.
Of course such conclusions are always somewhat speculative in nature,
and you may have better and more recent information.)
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