Since you already have the most efficient Smeltery, you may as well try and make it as efficient as possible when breaking down materials. You can speed up the process with Auxiliary Slurry Pumps.
A single Slurry pump can be placed (sneak-right-click with it in hand) on any side of your Smeltery. It will act as a second output. You can even place four more Alembics on top of it.
There is one more stage of this research but it is currently not available.
You can decrease the amount of flux that is let into the surrounding area by adding Auxiliary Venting Ports. With a bit of research, you should have no trouble completing this part.
You can add up to three Vents (with no Slurry Pump attached). You cannot add Vents to the top, bottom or front face of the Smeltery. These Vents will cut the amount of Flux let into the area by a third, but they do have diminishing returns (adding 2 would be most efficient).