The Phosphate Beneficiation Process
Phosphorus is required by every living plant and animal cell. It is a primary nutrient for plant growth, and our bodies need phosphorus to form bones and teeth and help make protein. Phosphorus occurs as phosphate in nature, and it cannot be artificially produced. It must be mined. Phosphate beneficiation is a post-extraction step of the phosphorus refinement process where the extracted phosphate matrix is mechanically separated into its mineral components. Only the phosphate in the matrix can be refined into phosphorus, so it is important to remove all of the impurities before chemical refinement begins. In Florida, phosphate matrix—the layer of the earth that contains phosphate--is a mixture of three components—phosphate, clay, and sand. Each of these components have a different average size, with phosphate being the largest and sand being the smallest. When it is extracted, the phosphate matrix is also mixed with small chunks of waste rock that are much larger than the matrix particles.
The first step in the phosphate beneficiation process is to separate the small rocks by soaking the extracted materials in water and then running the resulting slurry through a mesh sieve. The sieve traps the rocks, but allows the rest of the matrixslurry to flow through. This step is repeated with increasingly finer and finer sieves to separate smaller and smaller rocks from the phosphate matrix.
In the second step, the goal is to separate the clay particles from the phosphate and sand particles. This step is easier in Florida than it is in many other states because Floridian phosphate matrix contains lower levels of impurities than phosphate matrixmined elsewhere. In this step, the phosphate matrix and water slurry is put into a large centrifuge and spun until the clay isseparated from the phosphate and sand. The clay is set aside in clay storage areas, and the remaining phosphate and sand slurry moves on to the third step.
The third step of the process is called two-stage flotation. Here, an organic compound is added to the slurry which attaches to the phosphate particles. Then, air is introduced into the mixture in a process called aeration. Because the phosphate particles are now attached to the compound, they float to the surface, where they can be skimmed off the top and collected. The third step is then repeated with a different organic compound that attaches to the remaining sand and removed.
Once all the impurities are removed, the usable phosphate can be chemically processed for end uses, such as phosphorusfertilizer. In the case of HPS, the usable phosphate will be shipped off-site via rail for further processing.