Is there a way to speed up the smeltery's smelting process?
Solution 1:
There are several mods that introduce items that speed up the tick rate locally. Examples include time torches and items similar to them. Now you want to put this next to the Smeltery controller.
Between Ender IO, AE2, and some nifty redstone, it can be fully automated.
Solution 2:
No, you cannot speed it up.
However, you can process more at the time by increasing the size of your smeltery, which is handy when you start automating it.