Flotinor 4815 efficiently purifies calcium carbonate for cement application

The Bottom Line

The leading flotation technology provider, Clariant offers 70 years of process optimization experience.

By relying on our proprietary Flotinor 4815 collector, a Brazilian mine’s reverse flotation circuit…

• Produces a high-quality mineral concentrate with a calcium oxide grade higher than 46% 
• Reduces magnesium oxide content to less than 5%
• Improves calcium carbonate mass recovery
• Produces foam stability specifically designed to mineral characteristics

Objectives

To make its calcium carbonate product for the concrete industry, a large mine in Brazil uses reverse froth flotation to purify the calcite ore feed material containing silicate-magnesium mineral impurities, such as phlogopite. Since magnesium oxide negatively reacts with water in concrete applications, the mine requires an MgO grade of lower than 5.5% in its concentrate.

Foam stability is critical in the reverse flotation of calcium carbonate. The mine’s standard collector, a quaternary ammonium compound, produces foam that remains too stable, which has an undesirable effect on the next mineral processing step. The flotation circuit requires a collector that produces foam that is stable enough to float the impurity mineral particles and break after discharged from the flotation cell, prior to entering the tailings dam.

Beyond meeting grade quality and foam demands, the reagent solution must adhere to the customer’s price-performance balance. In addition to price, the type of raw material, its toxicity, biodegradability and other factors remain important.

Background

One of the most important minerals on the market, calcite is found throughout the world in sedimentary, metamorphic and igneous rocks. In the form of limestone and marble, it makes up a significant portion of the planet’s crust and serves as one of the largest carbon repositories. Calcite’s properties make it extremely useful in abrasives, agricultural soil treatments, cement, pigments, pharmaceuticals and more.

High magnesium silicate minerals found in the feed ore – in excess of 6% in the tailings from the phosphate flotation at the mine – are a limiting factor for economic use, especially with concrete industry. Calcite is successfully used as filling material by the cement industry in many European countries. However, calcite with an MgO grade lower than 5.5% is required to avoid the reaction between the magnesium oxide and water (hydration), which increases water volume and weakens the concrete after hardening.

To produce purified calcium carbonate for its cement customers, the mine uses a reverse flotation process where the silicate-magnesium gangue mineral is floated and a concentrate containing calcium carbonate remains in the flotation cell. The collector adheres to the mineral surface in addition to producing foam. The use of quaternary ammonium compound in this process is well known, but this type of collector produces stable foam, which is undesirable for the next mineral processing step.

Clariant continues to optimize the reverse froth flotation process of purifying calcite ore. While achieving a low magnesium oxide grade is important, the foam formed should only be stable enough to float the impurity mineral particles. The foam should then break after being discharged from the flotation cell, before transitioning to the tailing dam. Our latest collector innovation is an emulsion developed to float the impurity mineral without producing undesirable foam.

Actions

Working with mine ore samples, Clariant techniques conducted standard flotation bench tests on a variety of new collector reagents. During the trials, they analyzed collector performance to develop a new formulation that optimized mineral mass recovery properties while reducing foam stability.

Lab results showed Flotinor 4815 exhibited the most selective interaction with the mineral species. Additionally, the new collector produced adequate foam generation for impurity removal.

The mine’s technicians then conducted pilot trials with Flotinor 4815. They compared results generated by the new Clariant collector against the standard collector (pure quaternary ammonium) at dosage rates of 300 and 400 grams per metric ton. Technicians determined that Flotinor 4815 increased calcite mass recovery by more than 8% over the standard collector, while lower impurity levels to less than 5%.

Results

Flotinor 4815 now gives the mine a collector exhibiting a high mass recovery with a similar magnesium oxide grade compared with the previous collector. Flotinor 4815 also produces less foam than the previous collector, according to comparative Ross Milles tests.

By switching to Flotinor 4815, this mining operation in Brazil…

• Realizes a calcium carbonate mass recovery percentage of greater than 83%
• Reduces silicate magnesium impurity levels to less than 5% for its cement customers
• Eliminates issues caused by foam that is too stable
• Improves calcium carbonate mass recovery compared to its previous collector
• Uses a highly selective, tailor-made collector designed to meet changing feed conditions