Copper oxide ore hydrometallurgy - thin layer heap leaching

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    Holmes & Narver Inc. of the United States has developed a method called “ thin layer heap leaching ” , which has been greatly developed in recent years. The whole process includes the following processes [1] :
A ore crushing
    The ore needs to be broken to about 8mm In order to ensure that the leachate can pass through the heap at a uniform rate, obtaining a higher leaching rate. Excessive crushing will reduce the speed at which the leachate passes through the heap.
B plus acid treatment
    The crushed ore is first mixed with acid by a drum to reach a moisture content of 8% to 13% , and the residence time in the drum is about 0.5 to 1 minute . The acid amount is determined according to the experimental results and the acid balance of the entire process.
C stacking and ripening
Adding an acid curing ore pile, let fever, activation, so that part of the metal was dissolved, while increasing the permeability of the ore. The ripening and the heap leaching are carried out separately, so that the agglomerates generated during the aging can be broken to prevent the generation of the channel flow.
D heap leaching
The aged ore is almost dry and brittle, and is transported by forklift to a pre-prepared yard to pile up at a height of about lm , which maintains good permeability throughout the leaching cycle. Increasing the stack height will lengthen the leaching cycle and increase operating costs. This is the characteristic of the " thin layer leaching " method.
E spray
Optimum leachate can be obtained by spraying with circulating leachate. The spray speed is about every ton of ore per day. 1.2m 3 Solution. The copper leaching rate is shown in the figure below. The first stage is the copper sulphate produced during the leaching and ripening stage. The concentration is high. This process lasts for about three days, followed by leaching of the copper. In the actual operation, countercurrent leaching is often used, that is, the late low-concentration leaching liquid of the previous pile is used for new heap leaching, and the produced rich leaching liquid is directly sent to the extraction material liquid storage tank. The late leachate is stored with the raffinate (see figure below). After the desired recovery rate is reached, rinse with water and drain. In the end, the tailings contain about 8% of the moisture, and the slag is removed from the site and sent to the tailings field without the need to build a tailings dam. The yard is rebuilt with new mines, so the yard is called a multi-use yard and is made of acid-resistant cement. The yard period is generally six days, and the leaching rate for oxidized ore is up to 90% . The investment is only 50% of the leaching tank. In this way, the secondary sulfide ore can be leached, and the leaching rate can reach 50% , but the high iron ion concentration should be maintained in the solution during the curing.
The Souece Minera de Padahuel of Sosos Mining in Chile first used and further developed this method. It has been applied in many factories and mines.
references
    1.Brimm EP , Johnson P H. Conference of Metallurgists , Montreal , Canada , Aug.28 , 1978[next]

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