Why does it say that smoke came in His nose?
Rashi: When one gets angry, smoke exudes from his nostrils, and so the smoke came in His nose. The expression "Charon Af" means that the nose snorts and spews out hot air.
Radak: This is a metaphor for anger against enemies, like "Az Yeshan Af Hashem v'Kin'aso" (Devarim 29:19). 1
Malbim (Tehilim 18:9): The verse illustrates a burning [volcanic] mountain spewing fire, sulfur and smoke on the day of noise, as if the smoke comes from His nose.
According to Targum Yonasan, it refers to Pharaoh.
Why does it say that fire from His mouth consumes?
Rashi: From the decree of His mouth, fire will consume Resha'im.
Radak: Fire from His mouth will consume [the enemy].
Malbim (Tehilim 18:9): The verse illustrates as if Hashem's anger burns in the heart of the mountain, and the consuming fire comes from His mouth, like fiery rocks that come from volcanoes.