In the Bible, we find fire occasionally associated with God.  The burning bush of Moses.  The pillar of fire that led him to the promised land.  The star (a big ball of fire) that announced the birth of Jesus.  More often  though, fire is associated with Lucifer, Satan and the other fallen angels.  So how can it be both a symbol of God and a symbol of the fallen angels? The answer is, I think, pretty simple.
    When we talk about fire that is associated with devils, that is material fire, a physical thing.  With God, we are talking about something spiritual.  So the burning bush, the pillar of fire, and probably even the Star of Bethlehem should not be thought of as physical things, but rather spiritual ones, ant the terms are symbolic, not literal.  Just as the term "Sun of Righteousness" refers to the spiritual sun, not the physical one.