Yes, REFINE is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, F 4, I 1, N 1, E 1.

Is it a valid word?

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

improve or perfect by pruning or polishing
make more complex, intricate, or richer
treat or prepare so as to put in a usable condition
reduce to a fine, unmixed, or pure state; separate from extraneous matter or cleanse from impurities
attenuate or reduce in vigor, strength, or validity by polishing or purifying
make more precise or increase the discriminatory powers of

Also: fine-tune.