Methods, devices, systems and processes for upgrading iron oxide concentrates using reverse flotation of silica at a natural pH
Cationic reverse flotation methods, systems, and processes for producing a marketable iron oxide concentrate from an iron oxide mineral slurry (“treatment slurry”), wherein the iron oxide content of the concentrate is greater than the iron oxide content of the treatment slurry, include introducing the treatment slurry into a flotation cell, together with a collector, a frother and optionally an iron oxide depressant, and recovering two flow streams from the flotation cell, namely a froth fraction (also referred to as a flotation tail fraction) and a sink material fraction (also referred to as the flotation concentrate), wherein the treatment slurry in the flotation cell is maintained at a Natural pH.
1. A method for processing a treatment slurry stream, comprising:
introducing into a first flotation cell a treatment slurry stream, the treatment slurry comprising a mineral assemblage that includes a first concentration of silica and a second concentration of at least one iron oxide;
metering into the first flotation cell a collector and a frother;
recovering a froth fraction from the first flotation cell;
recovering a sink material fraction from the first flotation cell;
conditioning the treatment slurry before introducing the treatment slurry stream into the first flotation cell, wherein said conditioning comprises mixing a depressant into the treatment slurry, wherein said depressant comprises a starch material made by mixing starch with a caustic and wherein mixing the depressant into the treatment slurry provides a mixture having a pH greater than 8.5; and
reducing the pH of the mixture before introducing the mixture into the first flotation cell, wherein said reducing comprises injecting CO 2 into the mixture;
wherein the sink material recovered from the first flotation cell comprises a silica concentration lower than the first concentration and an iron oxide concentration greater than the second concentration.
2. The method of claim 1 wherein the collector comprises an amine, a diamine or a combination thereof.
3. The method of claim 2 wherein the collector is metered into the first flotation cell at a rate sufficient to maintain the treatment slurry at the target pH.
4. The method of claim 1 wherein the frother comprises methyl isobutyl carbinol.
5. The method of claim 1 wherein the frother comprises a mixture of an aliphatic alcohol, an ester and an ether.
6. The method of claim 1 , further comprising metering a basic reagent into the first flotation cell at a rate sufficient to maintain the treatment slurry at the target pH.
7. The method of claim 6 wherein the basic reagent comprises sodium hydroxide.
8. The method of claim 1 wherein the caustic comprises sodium hydroxide or potassium hydroxide or a mixture of the two types of caustic.
9. The method of claim 1 wherein said reducing further comprises metering an acid into the mixture.
10. The method of claim 1 , further comprising introducing one of the froth fraction or the sink material fraction into a second flotation cell.
11. The method of claim 1 , further comprising introducing the froth fraction into a second flotation cell and introducing the sink material into a third flotation cell.