The high pressure makes the method ideal for oxidative leaching of sulfides since the content of dissolved oxygen in the leaching solution is directly proportional to the pressure. Also in acid leaching of sulfides it can be chosen if the sulfide should be converted to elemental sulfur or sulfate . At temperatures below 120 150°C elemental sulfur is formed which in many cases is a preferred form and also requires less oxidant to be added.
The technical advantages of pressure leaching over atmospheric leaching stem from a combination of elevated operating temperature and oxygen overpressure, both of which increase reaction kinetics. Increased operating temperatures above the ambient boiling point can only be achieved by increasing pressure. Early Applications of Pressure Leaching
Pressure Oxidation Leaching Process. Batch Autoclave Laboratory Procedures: The vessel used for the laboratory pressure oxidation process was a two liter Parr titanium autoclave with dual impellers. It was heated and cooled externally and was pressurized with commercial grade oxygen.
A consequence of these studies was the observation that the oxygen percentage in the offgases and consequently the oxygen partial pressure varied materially during the leaching period. The highest consumption of oxygen is occurring during the period covering ½ to 2 hours and tailing off to a minimum over the last 3 hours of the 8 hour leaching ...
leach contact time and, accordingly, the size of vessels. Although oxygen partial pressure also affects the rate of leaching, tempera ture has a far more pronounced effect. When the pressure is increased from atmospheric to 20 psig and the temperature from 180°F to 220° in Pachuca tanks, leach retention times are cut roughly in half. At higher levels, in the range of 50 psig and