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Early research limited the leaching temperature to 110
In research and development in terms of temperature acid leaching, as early as the 1970s when Soviet researchers discovered that leach temperature above the melting point of sulfur, the addition of a small amount of chloride leaching of nickel-iron can strengthen pyrrhotite taken, The sulfur produced does not prevent further leaching of the sulfide ore. Noranda (Noranda) mining company has developed a process of chalcopyrite leaching, the leach temperature 130 ~ 145`C.
In the past ten years, the medium temperature leaching of chalcopyrite has been highly valued. In the study of overcoming the influence of product elemental sulfur on the leaching reaction, more attention has been paid to finding solutions from industrial applications and engineering.
At the time of chalcopyrite leaching, most of the copper is leached very quickly, and only about 10% to 20% of copper requires a longer leaching time. In order to shorten the residence time in the autoclave, two sections of copper were taken, and the first section dipped 85% to 90% of copper in a short period of time. The unreacted copper concentrate is then recovered from the slag by flotation, dried, and then melt filtered to separate sulfur. The remaining copper concentrate is then ground and returned to the leaching. Although this copper concentrate is a hard-to-dip part and still contains many elemental sulfur, their leaching rate is not slower than that of the raw material copper concentrate. The returned elemental sulfur is not significantly oxidized during the leaching process. Therefore, the total leaching rate of copper can reach 98% to 99% by two leaching. At the time of flotation, most of the gold enters the sulfide ore concentrate. Recent studies have shown that gold remaining in flotation tailings can be recovered by direct cyanidation and the cyanide consumption is not large.
For low-grade concentrates with high pyrite, it is unreasonable to oxidize all pyrite. The method adopted by Dinatek is to finely grind the ore, slightly extend the leaching time, and make the copper leaching as much as possible, but the pyrite is not completely oxidized. The recovery rate of gold is determined by its state of occurrence and its distribution during flotation. Silver may produce silver iron strontium salts. When the silver content is high, lime must be used.
References :
1.Gupta, CK, Mukherjee TK, Hydrometallurgy in Extraction processes, Vol.1 , CRC Press , 1990 , Boston
2. Berezowsky RM et al., JOM , 1999 , 12 , Gupta
Sulfide ore acid leaching - medium temperature oxidation acid leaching
   Medium temperature leaching is roughly 150~ 170 ° C Often, the leaching speed is faster at the initial stage. However, as the amount of elemental sulfur formed increases, the reaction rate gradually decreases. The melting point of sulfur varies depending on the crystal state, and the melting point of orthorhombic sulfur is 385.8K . At 386.4 K , the orthorhombic sulfur is converted to monoclinic sulfur, and the melting point is changed to 392K . Although increasing the reaction temperature is beneficial to the leaching of sulfide ore, experience in practice shows that the best temperature range for producing elemental sulfur is 155~ 160 ° C . Above this temperature range, the viscosity of liquid sulfur increases significantly with increasing temperature and begins to oxidize to sulfate. -115°C That is, below the melting point of sulfur, in order to prevent molten sulfur from encapsulating unleached particles. Because the infiltration of liquid sulfur sulfide ore is very easy, especially copper sulfide ore surface, resulting in coated or agglomerated. Many compounds have been found over the years as surfactants or dispersants to reduce the infiltration of liquid sulfur into the sulfide ore, thereby reducing the coating or agglomeration of sulfur to the sulfide ore. The most used of these are sodium lignosulfonate , as well as o-phenylenediamine (OPD) and an extract of bark and shredded wood ( trade name Quebracho) from Quebec, Canada. The addition of a small amount of chloride to the leachate can also be very effective in achieving the above objectives. Based on this discovery, several processes have been developed [1] . When Dina recent Canadian Tektronix (Dynatec)'s researchers found that both the chalcopyrite leaching or sphalerite, a small amount of pulverized coal to be very effective in reducing agglomeration of sulfur and sulphide minerals [2]. 90 ° C It is possible to recover by dissolving the iron strontium salt from the left and right and releasing the silver from it.