Pressure leaching

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Pressure leaching is carried out in [[autoclaves]] (Figure …) at high temperatures (>220&deg;C) and pressures (>20 atm). It is usually characterized by very fast kinetics and the duration of the leaching is from 30 minutes up to 24 hours depending on concentrate being leached and conditions applied. The high pressure makes the method ideal for oxidative leaching of sulphides since the content of dissolved oxygen in the leaching solution is directly proportional to the pressure. Also in acid leaching of sulphides it can be chosen if the sulphide should be converted to elemental sulphur (S&deg;) or sulphate (SO<sub>4</sub><sup>2-</sup>). At temperatures below 120-150&deg;C elemental sulphur is formed which in many cases is a preferred form and also require less oxidant to be added. Pressure leaching is applied in leaching of Co and Ni sulphides with ammonia as leaching reagent, in the so-called Sherrit Gordon process. Another big application of pressure leaching is the Bayer process where bauxite is leached with sodium hydroxide to produce alumina (Al<sub>2</sub>O<sub>3</sub>), which is used as raw material for aluminium production by smelt electrolysis.
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Pressure leaching is carried out in [[autoclaves]] (Figure …) at high temperatures (>220&deg;C) and pressures (>20 atm). It is usually characterized by very fast kinetics and the duration of the leaching is from 30 minutes up to 24 hours depending on concentrate being leached and conditions applied. The high pressure makes the method ideal for oxidative leaching of sulphides since the content of dissolved oxygen in the leaching solution is directly proportional to the pressure. Also in acid leaching of sulphides it can be chosen if the sulphide should be converted to elemental sulphur (S&deg;) or sulphate (SO<sub>4</sub><sup>2-</sup>). At temperatures below 120-150&deg;C elemental sulphur is formed which in many cases is a preferred form and also require less oxidant to be added. Pressure leaching is applied in leaching of Co and Ni sulphides with ammonia as leaching reagent, in the so-called [[Sherrit Gordon process]]. Another big application of pressure leaching is the [[Bayer process]] where bauxite is leached with sodium hydroxide to produce alumina (Al<sub>2</sub>O<sub>3</sub>), which is used as raw material for aluminium production by smelt electrolysis.
[[Category:Leaching]]
[[Category:Leaching]]

Revision as of 14:09, 27 June 2007

Pressure leaching is carried out in autoclaves (Figure …) at high temperatures (>220°C) and pressures (>20 atm). It is usually characterized by very fast kinetics and the duration of the leaching is from 30 minutes up to 24 hours depending on concentrate being leached and conditions applied. The high pressure makes the method ideal for oxidative leaching of sulphides since the content of dissolved oxygen in the leaching solution is directly proportional to the pressure. Also in acid leaching of sulphides it can be chosen if the sulphide should be converted to elemental sulphur (S°) or sulphate (SO42-). At temperatures below 120-150°C elemental sulphur is formed which in many cases is a preferred form and also require less oxidant to be added. Pressure leaching is applied in leaching of Co and Ni sulphides with ammonia as leaching reagent, in the so-called Sherrit Gordon process. Another big application of pressure leaching is the Bayer process where bauxite is leached with sodium hydroxide to produce alumina (Al2O3), which is used as raw material for aluminium production by smelt electrolysis.

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