Method and means for using microwave energy to oxidize sulfidic copper ore into a prescribed oxide-sulfate product

Abstract

The present invention is directed to the microwave treatment of a class of selected metal ores and concentrates, particularly those known as chalcopyrite, in a fluidized bed reactor. The end product is commonly a mixture of copper oxide and copper sulfate, both of which are liquid soluble and directly recoverable by known techniques. The ratio of the oxide-sulfate mixture end product may be controlled by suitable control of microwave parameters.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims the benefits of U.S. Provisional Application Ser. No. 60 / 826,350, filed Sep. 20, 2006 entitled “Method and Means for Using Microwave Energy to Oxidize Sulfidic Copper Ore into a Prescribed Oxide-Sulfate Product”, which is incorporated herein by this reference.FIELD OF THE INVENTION[0002]The invention relates generally to the recovery of selected transition metals from sulfidic materials and particularly to the recovery of base metals, particularly copper, from sulfidic materials.BACKGROUND OF THE INVENTION[0003]Chalcopyrite is a commonly occurring sulfidic copper ore which must be oxidized to liberate the copper and make it amenable to conventional recovery techniques, which include smelting and solvent extraction (SX / EW). Due to the modest value of the finished copper metal, there is always a need for lower-cost methods of production. Coupled with this is the environmental concern over historical smelter ope...

AI Technical Summary

Benefits of technology

[0023]The present invention is particularly effective for the microwave treatment of a class of copper ores and concentrates known as chalcopyrite, whereby the end product is a mixture of copper oxide and copper sulfate, both of which are highly soluble in solvents, such as water and mineral acid, and directly amenable to solvent extraction electrowinning (SX / EW) copper recovery techniques. The problem of fine grains of copper-containing concentrates reporting to the slimes can be eliminated, thereby making it practical to recover the copper from copper concentrates.

[0024]Because sulfur-free copper oxides and copper sulfates are produced simultaneously under the same operating conditions, the ratio or relative proportions of (sulfur-free) copper oxides and copper sulfates in the removed oxidized material may be tailored for a selected downstream metal recovery process because of the precise process control afforded by the microwave process. For example, controlling the ratio can be a significant feature in the downstream metal recovery process because it provides a methodology for controlling excess acid generation during chemical pressure oxidation, such as in an autoclave. This can be particularly important in high and medium temperature pressure oxidation applications. An added advantage of the disclosed process is that it is most efficient in treating low concentration ores and concentrates known as “rough concentrates”. As will be appreciated, these materials are commonly more coarsely ground than copper ores and concentrates subjected to conventional pressure oxidation, thereby avoiding very significant grinding and concentrating costs and making it possible to economically process copper ores which would otherwise be subeconomic.

[0025]The present invention can provide a number of advantages depending on the particular configuration. By way of example, the use of microwave energy rather than radiant thermal energy can provide substantial energy savings. Microwaves heat and activate primarily the selected metal component of the sulfidic material and not the gangue (or other components). Microwave heating can extremely rapidly heat the selected metal components. The present invention can produce the selected metal oxide and sulfate end products more rapidly than by using either a simple batch process (as disclosed by Kruesi) or a conventional bubbling fluidized bed device. The microwave-controlled fluidized bed reactor of the present invention can beneficially operate as a “lean phase” (i.e. high gas to solids ratio) fluidized system similar to the elutriated (cyclone) product stream described herein.

Problems solved by technology

A large portion of the cost of producing copper product is the cost associated with the production of the high-value concentrate.

Of this, grinding is the most energy consumptive and costly, however this is an unavoidable step in conventional concentration which relies on increasingly finer grinding to liberate (and separate) the sulfide particles (containing the copper) within the ore.

Reaction (3) is actually an intermediate reaction which, upon further oxidation, produces CuO.Fe2O3 which is an insoluble spinel product and is therefore undesirable.

As well, Kruesi does not disclose an applicator or device in which the microwave process can be practiced such that the process variables (temperature, feed rate, gas composition, gas / solids intermixing) can be controlled as in an industrial process.

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