So I have 2500 addi ores and 7k coal at the moment and I heard that the blast furnce uses half the coal to make bars? Can I bring my own coal and addi there and make into bars or do I have to somehow get the ores within the game to take advantage of the half coal deal?

You bring your own stuff, but you'll need a team probably to do it. I think there's a guide somewhere about how to do it solo..

 

 

 

*EDIT* Here's that guide for soloing the Blast Furnace

The blast furnace uses half the amount of coal for every ore, including what you brought yourself. It's actually pretty easy to solo the furnace, just give it a try. The biggest problem is that you cannot unnote addy or runite ores there. That means that you are restricted to about 25 addy ores per bank run. It's a lot faster to superheat the ores into bars.

Hey, I need to use the blast furnace for a few thousand ores. Can we get together a group to do the furance today or tomorrow?

You actually can un-note your ores at the shop that's right there. It requires a bit of cash, but it's doable.