KCA fabricates mercury retorts that can process up to 40 cu. ft of wet or dry solids per batch. Temperature and time are fully automated. Mercury retorting treats materials containing significant mercury concentrations prior to smelting or further purification — minimizing the release of mercury vapors. Mercury is distilled from mercury-rich sludge or precipitate (typically containing mercury, gold, silver, and impurities); the wet sludge is slowly heated to the boiling point of mercury and the vapors are then condensed and collected.
The wet sludge is loaded into trays inside the stainless-steel retort chamber. The chamber is slowly heated above the boiling point of mercury under vacuum. Vapors are drawn through a water-cooled condenser. Liquid mercury collects in a sealed pot for periodic transfer to a containment vessel. The dry residue (with Au, Ag, and impurities) is sent to smelting.
KCA’s Mercury Retort (Model R17E shown) typically consists of the following elements:
• Stainless steel chamber where trays of precipitate are heated to expel mercury
• Heating chamber lined with refractory wool insulation
• Main control panel containing the Smart Controller (SCR), Eurotherm main process and high-limit controllers
• Skid-mounted electrical transformer, vacuum pump complete with starter, retort safety switch and furnace safety switch
• Mercury receiver for safe collection of the condensed mercury vapors
• Shell-and-tube heat exchanger for additional cooling of the mercury vapors
• Large carbon filter stainless steel tank filled with sulfur-impregnated carbon
• Vacuum pump which maintains negative pressure throughout the entire system
• Pan handler cart for the loading and unloading of pans into the tray chamber
• Air-water separator for the vacuum pump discharge
• Vacuum pump air exhaust chimney
KCA also offers engineering, design and installation supervision services to ensure the mercury retort area has adequate containment features suitable for the installation of the unit.
Mercury retorts allow precious-metal producers to meet environmental regulations on mercury emissions while maintaining gold and silver recovery from concentrate. KCA retorts are designed to meet permitted emission limits in every U.S. state and major foreign jurisdiction.
Selected recent projects where KCA delivered this service. All from our portfolio of 500+ engineering projects.
Whether you’re at scoping stage or ready to break ground, KCA has the lab capacity, engineering bench, and EPCM experience to deliver.
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