A Proto-Furnace was a device of Tirolian device that was seemingly used for the storage of Protoculture. They were equipped onboard the large Tirolian Motherships and were used during the exodus to Earth.
Before the onset of the Second Robotech War, the Robotech Masters were briefed by their clone scientists that there was insufficient supplies of Protoculture which afflicted their Bioroid operators. To combat this problem, ruling Triumvirate authorized the withdrawal of further Protoculture from the Proto-Furnace but only enough to ensure the success of their mission against the United Earth Government.
Behind the Scenes
This device is only mentioned in the one dialogue in the episode "Dana's Story" with no elaboration as to the machines purpose.