Yes, SUBLIMING is a Scrabble word!

Letter values in Scrabble US: S 1, U 1, B 3, L 1, I 1, M 3, I 1, N 1, G 2.

Is it a valid word?

SUBLIMING is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

vaporize and then condense right back again
change or cause to change directly from a solid into a vapor without first melting