What is "fractionating"

Usage examples of "fractionating".

I was aware of all her hidden engines, all working away, from the slow hard kuh-dup of her heart to all the other hidden things, absorbing, nourishing, fractionating, eliminating.

Outside, the tops of fractionating towers and steel pylons, indistinct and ghostly in Titan’s feeble light, were drifting slowly into view from below.