Hell and death are thrown into the lake of fire at the end of the 1,000 year reign. They are not there yet, so nobody can be burning in the lake of fire, even if they are in hell.
There is a huge misunderstanding of the meaning of the Hebrew and Greek words that have been translated “hell”. A beginning to understanding the significance of those words can be found here: http://www.gotquestions.org/did-Jesus-go-to-hell.html