Presence of solids/ sludge implies that someone, someday, will be tasked with cleaning the gooey side of the thing. Whether you like it or not, they will use scrapers, and chisels, and hammers.
Which suggests something like Panelcoil, but with the sludge contact surface made planar, and either thick or abrasion resistant or both.
I don't know if anyone actually makes such a thing commercially, but you get the idea.
Mike Halloran
Pembroke Pines, FL, USA