[chemeng]

There are working fluids (molten salts, liquid metals, etc) that can work in this regime, typically with ceramic piping systems (usually ceramic lined nickel alloy steels) with all ceramic/graphite pumping systems. That said, it’s used in very niche applications and hard to maintain at the scale required for a CSP plant.

If you’re after heat, it would be much simpler to just use the steam. Use it as is, as we have for centuries now, or you could transfer it to a higher thermal capacity oil, and if you want some energy, divert it to a steam turbine.

For cement you could presumably use the heat as a preheater, or use the energy for an arc furnace.