[AR] Re: Removing coking deposits
- From: Peter Fairbrother <zenadsl6186@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Fri, 16 Sep 2016 17:12:10 +0100
On 16/09/16 04:42, Henry Spencer wrote:
On Thu, 15 Sep 2016, Robert Watzlavick wrote:
...a few of the holes seem slightly darker than others so I can only
assume that is due to coking from the fuel (kerosene). Does anyone
have suggestions on how to clean up the holes? I was thinking of
chucking up a wire brush in a drill and running it down in the holes
but a solvent would be preferable.
I don't think you're going to find a solvent that will simply dissolve
classical coking deposits -- my understanding is that they simply aren't
soluble in anything reasonable. (Remember, if they're there at all,
that means that hot fast-flowing kerosene couldn't dissolve them...)
Yep.
Hydrocarbons when over heated break down into carbon and hydrogen -
eventually. If it has gotten that far then there isn't anything which
will dissolve carbon.
However, the decomposition occurs in stages. First you get shorter
chains with double bonds and triple bonds, then these join together to
form 3D masses of linked carbon atoms with few hydrogens, finally the
last hydrogens are driven off.
The last stage takes some considerable temperature and time though.
probably enough to melt aluminium.
As Henry says, if the deposits are still there then they don't dissolve
in hot kero - which is a pretty good solvent for low-hydrogen
hydrocarbons. About the only two better solvents are trichloroethane
(best) and methylene chloride aka dichloromethane (second best), which
may be worth a try.
heat,time
Some oven cleaners contain these. However other oven cleaners rely on
sodium hydroxide, which will/may dissolve partly carbonised organic acid
residues but isn't very good at dissolving low-hydrogen hydrocarbons.
And sodium hydroxide is quite good at dissolving aluminium ...
In the UK trike (trichloroethane) is hard to get hold of, but methylene
chloride is available. I don't know about US availability, but I suspect
it is similar.
Something that would *react* with them and not with the passage walls,
well, maybe, but I think it would take something pretty aggressive to
react with that stuff.
Perhaps supercritical water might do it? But 3050psi, 380C ...
Maybe just oxygen, with the chamber at around 600C?
I'd guess you're going to end up doing mechanical removal.
If you can, that's probably the best bet.
-- Peter Fairbrother
Henry
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