Purification of liquid metal heat exchange fluid for hydrocarbon conversion reactions, involves removing hydrogen from dissolved hydride in drum, at specified temperature and interfacial surface area

摘要

The method involves passing a portion of a circulating liquid metal stream comprising a heat transfer fluid into a drum maintained under vacuum. Sufficient interfacial surface area and sufficient temperature is provided in the drum to release hydrogen from hydride present in a liquid metal stream. The purified liquid stream is recovered and recirculated. The liquid metal stream initially contacts a heat transfer surface that permits permeation of hydrogen into the liquid metal stream and results in the formation of metal hydride. A portion of the circulating stream is withdrawn and passed to the drum maintained under vacuum. Hydrogen released from the drum is vented and removed. The purified liquid metal stream contains a near-equilibrium concentration of the metal hydride and has a reduced concentration of metal hydride relative to the stream separated from the circulating stream. The drum is maintained at a vacuum of 1-10 mm Hg and at 400-550 degrees C. At least a portion of the purified stream passes through an additional hydride removal zone, which comprises a cold trap that removes hydride particles from a cooled liquid metal stream. The cold trap is periodically regenerated by passing a heated liquid metal stream into the trap to dissolve metal hydride particles and produce a regeneration efficient stream comprising liquid metal and the dissolved metal hydride particles. The drum has trays for providing the interfacial surface area. The drum has at least 10 m2 of surface area per m3/hour of liquid passing through the drum. In an alternative method, multiple cold traps are provided either in parallel or serial flow.