Verfahren und Vorrichtung zur Rueckgewinnung von metallischem und/oder gebundenem Queck-silber aus quecksilberhaltigen Katalysatoren

摘要

Mercury is recovered as the metal from spent catalysts containing mercury chlorides by heating at 270-600 DEG C. (preferably 300-400 DEG C.) in a stream of a reducing gas such as hydrogen. Alternatively a non-reducing gas may be used at above 350 DEG C. when the mercury will be obtained mixed with mercury chlorided and hydrogen chloride. The process may advantageously be carried out at sub-atmospheric pressure, preferably 100 to 500mm of water. The gas may be led to a condenser to remove mercury and chlorides if present and then scrubbed with caustic soda to remove hydrogen chloride.ALSO:Mercury values are recovered from spent catalysts containing mercury chlorides, especially on active carbon, by heating the catalyst to 270 DEG to 600 DEG C. (preferably 300-400 DEG C.) in a stream of gas. If a reducing gas, such as hydrogen, is used, the product is metallic mercury. If nitrogen, air, steam, carbon dioxide or hydrogen chloride is used, the product varies. Below 350 DEG C. mercury (I) chloride and hydrogen chloride are formed, whereas above 350 DEG C. mercury (II) chloride and metallic mercury are also formed in significant amounts. If the gas containing the mercury compounds is brought into contact at the elevated temperature with an excess of chlorine, then the resulting products are almost exclusively hydrogen chloride and mercury (II) chloride which may be used to regenerate the catalyst. The process may be carried out at sub-atmospheric pressure, preferably 100 to 500 mm. of water. The effluent gas stream is led to a condenser to remove the less volatile components and thence to a scrubber to remove hydrogen chloride and other volatile materials. In the apparatus shown in the Figure, catalyst is fed from a hopper 1 through a pipe 2 blown with nitrogen 3 as a nitrogen-lock to a pre-heating zone 4 and thence to the body of the heated desorption vessel 7. Here it is blown with the gas admitted through pipes 8, 9. The mercury-free catalyst is removed via a metering unit 10. The gas passes to a chlorination zone 12 where it is mixed with chlorine supplied through pipe 11. It then passes to a condensing tower 14 where the bulk of the mercury (II) chloride condenses and to a caustic soda scrubber 16. The system is maintained at a reduced pressure by a water jet pump 18. The desorption vessel 7 should be lined with glass, quartz, porcelain, enamelled steel or brickwork, glass or plastic being preferable for the remainder.