The Industrial Oven's primary advantage over the stock Furnace is one of efficiency. Instead of being able to smelt one item at a single time, up to nine items can be smelt simultaneously, which is a large advantage when producing items at scale later on in Polycraft. In other words, a single Industrial Oven does the work of nine Furnaces.
What you'll need
How to make it
Start things off by distilling your crude oil. You should be left with a little over 2 beakers worth of Naphthalene, and about 32 vials of Gas Oil. Store the Gas Oil in some place you can get it back; you'll want it later. You'll then want to distill 2 beakers of that into about 1 beaker of Light Naphtha, which you then distill again. When you're finished, you should have 8 vials of Light Parrafins. You will need to repeat process until you obtain 16 vials to distill, which will give you 14 flasks of Methane and 2 flask of Ethane.
During any time in the distillation process, you can craft the Copper Ingots into Copper Pipe:
Or the Cobblestone into 3 Furnaces:
Or the Iron Ingots into a Bucket:
Make sure to fill your Bucket with water.
Once you've done this, you'll have all the items needed to craft an Industrial Oven. Head over to your Crafting Table and arrange the items like so to make an Industrial Oven (note: you need 2 flasks of Methane and one flask of Ethane):
You'll need some fuel in order to smelt items, just like a regular Furnace. Go back and get your Gas Oil, and put it in the fuel slot of your Furnace. Then put the Bucket into the bucket slot. You're now ready to smelt items at scale!