Yes, QUENCH is a Scrabble word!

Letter values in Scrabble US: Q 10, U 1, E 1, N 1, C 3, H 4.

Is it a valid word?

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

satisfy (thirst)
put out, as of fires, flames, or lights
electronics: suppress (sparking) when the current is cut off in an inductive circuit, or suppress (an oscillation or discharge) in a component or device
suppress or crush completely
reduce the degree of (luminescence or phosphorescence) in (excited molecules or a material) by adding a suitable substance
cool (hot metal) by plunging into cold water or other liquid

Also: snuff out, blow out.