Actually, if you chose you could just mix a flux and fire them up but you won't be happy w/ the result and odds are your new furnace isn't properly equipped to handle the plastic and what not you're trying to get rid of...few affordable ones are....and if curiousity gets you or you get anxious and start "watching the pot that never boils" you might really do yourself some damage, let alone the neighborhood sucking up the fumes.
There are lots of sites out there that can give you the basics for smelting, but even if you do come up w/ an adaptation for the chips that works, you'll still have to use chemicals (and then more heat again for that matter) to finish up the job. I'm guessing your furnace probably runs on propane and was advertised reaching temperatures to melt copper, gold and aluminum...but its a little trickier to actually do it than to just reach or be able to withstand the temperature. Also, the fuel will undoubtably put a big dent in any financial returns...assuming that's the goal as opposed to just enjoyment, entertainment or hobbying.
Either way, it strikes me so far in my reading here that its probably easier, less expensive and more satisfying to start at the other end w/ the chemicals and finish w/ the furnace. The by product of that approach is, man, this forum is so fascinating on so many levels that if hobbying is the goal you'll hit a home run...and if for profit is the goal, well, you'll hit a home run.
These guys (& gals, sorry) are real friendly, real patient & STUPID knowledgeable with actual collective experience on almost everything!
Cheers & happy hunting,
John
