On the ship on which I was a boiler technician we used a similar system for pre-heating the heavy fuel oil (properly labeled NSFO--Navy Special Fuel Oil). It was foul smelling, stained everything, flowed like molasses and attracted water and dirt like nobody's business.

The fuel was quite viscuous at room temp and thus, did not atomize well. So we'd run it through a 150 PSI, 350 F steam heat exchangers. We burned about 1,000 gal/hr per boiler at flank speed. Later we shifted to a diesel-like fuel-->JP-5. It had much lower thermal efficiency, meaning we burned about 1,200 gal/hr/boiler but it was a lot cleaner.

In order to make the switch we had to use a little bit different burner plates and a different casing air pressure but the difference in having to clean the firebox less frequently made a huge difference in a BT's life.

Oh yeah, the point of all that is that the cooks would dispose of dirty cooking oil by giving it to us. We'd run that stuff with no noticeable effect.

B