Was just looking there, indeed three invar boilers would reach the 96 steam/t limit of a bronze steam engine, but that would only produce the max 24 KU/t @ 50% efficency of a bronze steam engine.
I think that means it would only be able to give the compressor half of that, being about 12KU/t, 4KU/t under the minimum to run the compressor.
I could be way off on my assumptions here though.
As far as I know there is no way to link steam engines, so the only next tier up that would work is the steel one, all others produce 24KU/t max.