Production of Synthetic Proppants

All ceramic proppant producers use as feedstock essentially bauxite and, to a lesser extent, other industrial minerals with a high alumina content such as kaolin, nepheline syenite, wollastonite, talc, and feldspars. The final spherical shape is obtained by several processing routes currently used in the ceramics industry for producing beads and other particulate materials. The most common of these processes are pelletizing and sintering, atomization, fire polishing, and flame spraying. 

Atomization. This technique involves the melting at high temperatures (i.e., above 1800°C) of raw material particles together to obtain a molten bath of bulk liquid. Usually, the bulk liquid contains more than thousands of times the amount of raw material required to make a single product particle. A thin stream of molten material is atomized by dropping it into a disruptive air jet, subdividing the stream into fine, molten droplets. The droplets are then kept away from one another and from other objects until they have been cooled and solidified. Then they can be recovered as substantially discrete ellipsoidal glassy (i.e., amorphous) particles. 

Fire polishing. In this techniques, discrete solid particles are heated to the softening or melting temperature of the material, usually between 1200 and 1650°C, while suspended and dispersed in a hot gaseous medium (e.g., fluidized bed). As particles become soft or molten, surface tension forms them into an ellipsoidal shape. If kept in suspension until cooled below softening temperature, the particles maybe recovered as spherical grains. 

Flame spraying. In this technique, finely ground raw particles are premixed with a combustible gas mixture, i.e., fuel and oxidant, and the mixture is then introduced into a burner. Hence, in the hot flame, the tiny particles melt or soften, and the surface tension leads them to exhibit an ellipsoidal shape. To prevent molten droplets or soften particles from contacting any surface before cooling, the flame must be allowed to move freely in a large combustion chamber. The droplets or softened particles are then kept away from one another and from the reactor walls until they have been cooled and solidified. 

---