Hydrometallurgical Method for Ferromanganese Ore Processing
The technical result of the hydrometallurgy of nonferrous metals, in particular, the processing of ferromanganese nodules, is the reduction of expenses and the increase of volume of recoverable manganese, nickel, cobalt, and copper concentrates. This ore treatment method allows obtaining maximum values of mono-concentrates of copper, nickel, manganese, and cobalt.
This processing method includes fine crushing, leaching of nonferrous metals and manganese with a sulphurous anhydride in a sulphuric solution and a successive sedimentation of copper, nickel-cobalt concentrate solutions by way of introduction into the solution of metallic manganese and elementary sulphur powders, sedimentation of the manganese concentrate by an ammonia solution or ammonium carbonate. Copper concentrate sedimentation is carried out through introduction into the elementary sulphur powder solution (copper/sulphur ratio – 0.3-0.6, рН 2.5-1.0), and treatment by gas containing sulphurous anhydride. For ore leaching and copper concentrate sedimentation they use one reagent – elementary sulphur that is used to obtain sulphurous anhydride and as a sulphidizer in the course of copper sedimentation.
The copper sedimentation is implemented with the use of the elementary sulphur powder in combination with gas supplied to the solution which contains sulphurous anhydride. The elementary sulphur consumption and optimal pH values were determined by an experiment. The decrease in the sulphur consumption to less than 0.3 kg/kg of copper results in cementation. In case of increased consumption of over 0.6 kg/kg of copper, the excessive amount of sulphur converts into the concentrate, and thus the copper content is reduced in the concentrate.
The pH-solution limitation is conditional on the requirements of selective and complete sedimentation of copper in the solution.
If we continue the reduction of the pH indicator, we will observe the decrease in copper sedimentation. If we increase the pH indicator to more than 2.5, we will disrupt the selectivity of its sedimentation.
The copper sedimentation takes place according to the following reaction:
Thus, the elementary sulphur is used to obtain sulphurous anhydrate in order to leach the ore and start copper sedimentation, and as a reagent – a sulphidizer in copper sedimentation. In order to obtain SО2 one can use gases from the process of burning the obtained sulphide copper concentrate. In the latter case, it utilizes into SO2 from the copper concentrate.
The table shows a chemical composition and basic indicators of processing of deep-sea ferromanganese ores. The leaching of valuable elements from ores was carried out in reactor-turboaerators with a capacity of 3 liters at the temperature of 70C and a solid-to-liquid ratio equal to 1:4. The selective sedimentation of copper, nickel-cobalt and manganese concentrates was conducted in the reactors equipped with a mechanical stirring tool.
For the copper sedimentation, they supplied sulphur to a 90-95С solution while transmitting the gas through it, which gas contained 10-12 volume % of sulphurous anhydride.
The sedimentation time was 1 hour. Upon completion of the process, the sediment was filtered, washed and taken to a chemical analysis. In the solution they conducted the sedimentation of nickel-cobalt concentrate by sulphur and metallic manganese powders, and the sedimentation of manganese concentrate – by the solution neutralization with ammonia water.
The metallic manganese powder consumption for the processing of 100 kg of ore equaled 2.8 kg.
The recovery of copper to a copper concentrate was 90.4%. Thus, this method provides high selectivity of copper sedimentation.
The nickel and cobalt sedimentation with copper concentrate was 0.11%, and that facilitates the technique for its further processing. Besides, this method increases the volume of recovery of nickel and cobalt into the respective concentrate.
As a result of processing of ferromanganese nodules by the hydrometallurgical method, we can expect, subject to some losses due to recovery:
1,000 kg of nodules with the content in % of: Сu -1.05, Ni-1.20, Co-0.22, Mn-29.9, Fe-5.7:
The peculiarity of this multi-stage FMNs processing technology is a possibility to conduct these processes without high