Anyone out there with experiense of reclamation of heat transfer oil? I have a client with 6500 liters of mineral based heat transfer oil (ISO VG46). Flashpoint of new product is 200°c (cc) / 235°c (PM). Oil analysis indicate flashpoint of 148°c (cc). Anyone with tips on how to increase the flashpoint?

I am thinking of vacuum dehydration (for removal of vapours as contamination). And filtering for removal of particles.

We had a similar problem with one of our customers. They have a 25,000 litre heat transfer system in a timber mill. We processed the oil by centifugal seperation and vacuum dehydration. Also we filtered it nominally to 5 microns. The flash point had reached a similar figure of around 140degC. We treated the system with an additive to break down the carbon formation in the burners a little over a week before the system was processed. We found that vacuum dehydration removed the light ends from the oil and increased the flash point back to over 180degC (unsure of actual figure as the lab they use didn't test above this limit). We also found that the filtration removed large amounts of carbon (mostly in the centrifuge) and thus reduced the warm up time by over 50% and also ongoing heating costs. It is also important to note that the process was done without draining the system and a complete filtration was not completed due to time restrictions from production. None the less, the process proved extremely benefitial.

Hi Mr Hughes,
What MC has stated is correct,
if you pull the lighter ends off with a thin film vacuum evaporator you can use the heat Transfer systems operational heat and the lighter ends will boil off when the H** is feed through the thin film vacuum evaporator ,
these lighter ends will be mercaptains highly sulphurised that would be best feed back the boilers if allowed by the EPA to get rid of them, the flash point is lowered by the presence of these lighter ends which are off course a result of cracking the heavier ends off the HT oil molecule by exceeding the watts density of the heat transfer fluid,
this process could be continuos with a centrifuge removing the carbon and the fluid top up replenishing the additives,
Although one would have to ask why the system is damaging the fluid as if the watts density of the heat transfer fluid is not exceeded there should be minimal carbon formed in H** over years of use unless the product is blended from low quality base oils.
Regards Rob S

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Mr Hughes, you have the right idea regarding which approach to take.

Also, great kudos to our friends from “down under” on offered details of such approach.

Great comments!

John, nice of you to bump this post up again.

We did use a vacuum dehydrator for 3 weeks paralell with 1 micron cellulose by-pass filtration. The total oil volume was around 6500 ltrs. They used approx 12 filters (each with approx 0,5 kg holding capacity).

The flashpoint increased to 200 deg c (like new oil).
The customer saved big-$$ on not having to replace the oil, and I trust they would want to do the same next time.

Thank you all for your comments.

K.S.,
I assume that when you mentioning shear, you think of viscosity. Only lube oils are susceptible to shear, not heat transfer oils. To my understanding, filtration itself does not directly affects oil shearing.

I am aware of a company in Quebec , Canada that has a process for thermal transfer oils. I don't know the complete details but they claim they can do it while the oil is still hot and in use. A complete turn key process.

Hi Mikoil. I am looking for an equipment or technology that can do carbon removal from the heat transfer oil while the heat transfer system is operating with temperature 250 Deg. C. You can email me to djunaidi@indosat.net.id.