The HydroFloat technology was specifically developed to upgrade phosphate sands that are too coarse to be efficiently recovered by conventional flotation methods. In this novel process, classified feed is suspended in a fluidized-bed and then aerated. The reagentized phosphate particles become buoyant and report to the product launder after encountering and attaching to the rising air bubbles. Simultaneously, the hydrophilic particles are rejected as a high solids content (65-70%) underflow. The fluidized bed acts as a "resistant" layer through which no bubble/particle aggregates can penetrate. As a result, the HydroFloat also acts as a density separator that is capable of treating much coarser particles as compared to traditional flotation processes. In addition, the high solids content of the teeter bed promotes bubble-particle attachment and reduces the cell volume required to achieve a given capacity. To fully evaluate the potential advantages of the HydroFloat technology, a 5-tph test circuit was installed and evaluated in an industrial phosphate beneficiation plant. Feed to the test circuit was continuously classified, conditioned and upgraded using the HydroFloat technology. The test results indicated that the HydroFloat could produce a high-grade phosphate product in a single stage of separation. Product quality ranged between 70-72% BPL (bone phosphate of lime = 2.185 x %P2O5) and 5-10% insols (acid insoluble solids). BPL recoveries exceeded 98% at feed rates greater than 2.0 tph per ft^2 of separator cross-sectional area. These results were superior to traditional column flotation, which recovered less than 90% of the valuable product at a capacity of less than 1 tph per ft^2. / Master of Science

Possibilities for increasing the upper limit of floatable particle sizs in the froth flotation process have been examined since the early beginnings of mineral flotation. The economic implications of such an incresae are far ranging; from decreased grinding costs and increased recoveries to simplified flow-sheet design and increased throughput, all leading to increased revenue. Bubble-particle detachment has been studied to better understand the factors influencing the strength of attachment and the energies involved. Direct measurements of bubble particle detachment were performed using a hanging balance apparatus (KSV Sigma 70 tensiometer) and using a submerged hydrophobic plate in water. Three experiments were used; direct force measurement of bubble-particle detachment, detachment force and energy of a bubble from a submerged hydrophobic plate, and detachment force and energy of a cetyltrimethylammonium bromide coated silica sphere from a flat bubble. Octadecyltrichlorosilane was used as a hydrophobic coating in the first two experimental methods. These experiments were recorded with a CCD camera to identify the detachment processes involved. Energies for both methods were calculated and divided into the two main steps of the detachment process: Three-Phase-Contact pinning and three phase contact line sliding. The first step represents the energy barrier which must be overcome before detachment can begin. It is directly related to contact angle hysteresis. Detachment occurs during the second step, where the solid-vapor interface is replaced by solid-liquid and liquid-vapor. This step corresponds to the work of adhesion. The effects of surface tension, contact angle and hysteresis were well demonstrated with the three experimental methods. Good correlation was found between theoretical work of adhesion and measured energies. / Master of Science