Hi, I am new to blacksmithing and I have a idea for a coal forge. I plan on forging steel and doing a little bit of melting down copper, brass other metals with a low melting point. Without getting bogged down by too many details, I will be using a cut-down 50 gallon drum, and my question is this: I am planning on using ceramic fiber blanket for my insulator, and will this work with coal? I will be lining the inside of the drum with it, so will I be able to use coal in this? is there something I have to do to separate the insulator from the fuel? I don't know why but I have a feeling dust from coal would be damaging to the insulator I am using. I am probably wrong but better safe than sorry.

For a coal forge you don't need any insulation. The only insulation you could need would be if your forge pot was Thin material and it would basically just get lined with clay/sand or even just dirt. Refractory cement if you wanted to spend the money. Or those to build a fire pot if you were going that rout. A thicker steel fire pot needs none of that. 

You might not find the best of both worlds in one forge/furnace design. I'm not into melting or casting but I'll say a big Nope to ceramic fiber blanket in a coal Forge. 

Welcome to IFI! If you haven't yet, please READ THIS FIRST!!!

The thing is, you are talking about two entirely different processes. If you build one setup to do both, it won't do either particularly well. Pick whether you want to start with blacksmithing or casting, and then build either a forge or a furnace. 

What Daswulf says about not using ceramic fiber in a coal forge is spot-on. Look at the threads on the JABOD forges and the 55 gallon forge. That'll get you started on the right track.

Do you want a forge or a furnace?  they are not the same

Note that using a 55 gallon drum is ABSOLUTELY HUGE and will cost a lot of money to pay for heating it up.  I know a bunch of casters and the biggest they usually go with for a home system was built from a 33 gallon drum and well lined. (and using propane).  I've used my coal forge to melt small amounts (several ounces) of copper/silver/brass generally for knife fittings and jewelry. I generally use a Mt Fuji fire with the center sized for the crucible.

Can you explain more of what you want to accomplish with both the forge and the furnace?

All right. Thank you all! I will take this all into consideration.