One possibility bud...
Read through the whole thread mate, and you seem to have had no luck at all
I know you seem to have your mind set on Chlorine being the culprit, but I wouldn't close the case on that one just yet. I live in Ireland, right on the border between North and South and there's alot of dodgy fuel about.
One method rogue traders use around here is using suphuric/hydrochloric acid to remove the dye from laundered red diesel.
This usually leaves a "black sludge" behind which is then dumped.
I wish I was active here when the
problem first arose, I would have recommended a pH test on the fuel and more importantly the sludge that poured out to test for high acidity. Obviously the corrosive nature of the fuel would have played a part in knackering your engine, but if the cowboy laundering it didn't remove all of the waste after removing the dye, the black sludge you mentioned is what you would have found.
The waste consists of a multitude of chemical compounds and general gunk left after the process, and would have a chlorine pang to it.