Apparatus and method for supercritical fluid extraction or supercritical

Abstract

An automatic variable-orifice fluid restrictor for use with a supercritical extractor having a collection trap or a supercritical chromatograph includes an inlet line for fluid at a pressure above its critical pressure, an extended tubular probe having an inner and an outer surface and a proximal and a distal end. The proximal end of the probe carries an inlet connected to the inlet line and is outside of the trap. The distal end of the probe includes a variable orifice means adapted for metering the fluid. The variable orifice means is adjacent to the outer surface of the probe and is located in the midst of the trap. The variable orifice means is adjusted by an adjusting stem having first and second ends. The first end of the adjusting stem is connected to automatic control means such as a servo at the proximal end of the probe and outside of the trap. The second end of the adjusting stem varies the area of the orifice by moving a first orifice member. The stationary second orifice member cooperates with the first orifice member to form the orifice. The first orifice member moves axially when the orifice is closed and moves both axially and rotationally when the orifice is open or partially open. This cleans deposits from the orifice without damaging the orifice parts by high pressure notional physical contact.