Method and system for purifying a caustic fluid including sulfur

A method for purifying a caustic fluid including sulfur, the method comprising:

• (a) mixing the caustic fluid including sulfur with a hydrocarbon solvent, including injecting the hydrocarbon solvent, at a pressure greater than a pressure of the caustic fluid including sulfur, at a rate in the range of 3% to 10% of a flow rate of the caustic fluid including sulfur into a mixing valve operated at a pressure differential across the mixing valve in the range of 10 psid to 50 psid;
• (b) passing the caustic fluid including sulfur mixed with hydrocarbon solvent at a temperature in the range of from 50° F. to 150° F. through a pre-filter assembly operated at a pressure differential in the range of 1 psid to 25 psid, the prefilter assembly comprising a housing including the inlet and an outlet and defining a fluid flow path between the inlet and the outlet with at least one porous prefilter element in the housing across the fluid flow path, providing a solids-depleted caustic fluid including sulfur mixed with hydrocarbon solvent;
• (c) passing the solids-depleted caustic fluid including sulfur mixed with hydrocarbon solvent at a temperature in the range of from 50° F. to 150° F. through the inlet of a liquid-liquid coalescer assembly comprising a liquid-liquid coalescer assembly housing including the inlet and at least one liquid-liquid coalescer filter element in the liquid-liquid coalescer assembly housing, the liquid-liquid coalescer assembly housing having an upper part having an upper port, and a lower part having a lower port, wherein the liquid-liquid coalescer assembly is operated at a pressure differential in the range of 1 psid to 15 psid, with a flow rate in the range of 10 gpm to 50 gpm per liquid-liquid coalescer filter element;
• (i) passing coalesced droplets comprising sulfur and hydrocarbon solvent through the upper port;
• and
• (ii) passing purified caustic fluid having a reduced sulfur content though the lower port.