A flash tank including: a closed interior chamber; a gas exhaust port coupled to an upper portion of the chamber; a liquid discharge port coupled to a lower portion of the chamber; an inlet nozzle attached to an inlet port of the chamber, wherein the inlet nozzle includes a flow passage, and a movable valve plate in the flow passage, wherein the valve plate has a first position which defines a first throat in the flow passage and a second position which defines a second throat having a smaller cross-sectional area than the first throat.