In the gui for the industrial centrifuge there is a lava area.
what is it used for? Can I speed up the machine this way?
It is used to feed lava from a container object like a bucket.
By default you get:
16 Still Lava → 1 Tin Ingot + 4 Electrum Nugget + 2 Copper Ingot + 1 Tiny Pile of Tungsten Dust
This might be different depending on the pack.
It looks like the lava box is the place that the lava is stored from input via pipes.