"Factories are shutting down" is just a little bit more formal, but, in most situations, "close" and "shut" mean the same thing. You can shut the door, or close the door; close the drapes, shut the drapes, etc. There are a few exceptions, however. You never say "The store is shut" if a store isn't open for business, you always say "The store is closed", and I've rarely heard somebody say they are "Closing down the computer" instead of "Shutting down the computer"