Abstract: The Rio Capim Kaolin deposit contains a lower bed of soft kaolin clay that averages 10 meters thick, and an upper bed of “hard” kaolin (“RCC hard kaolin”) that may be as thick as 6 to 8 meters. Due to their high impurity content fine particle size, cementetious nature, and high degree of particle aggregation, hard kaolins are difficult to process. Disclosed herein are compositions comprising kaolin having a particle size distribution such that at least about 90% of the kaolin has a particle size of less than 1 micron and a GE brightness of at least about 91, where the kaolin may be derived from a crude kaolin having a Fe2O3 content of at least about 1.0% by weight, and optionally comprises titania in an amount of at least about 1.5% by weight. Also disclosed herein are methods of refining the hard kaolins, such as RCC hard kaolins, by dispersing the kaolin with at least one anionic organic dispersant and at least one inorganic dispersant.

Abstract: Disclosed herein is a method of heat-treating particulate material, such as kaolin. The method comprises providing a feed mixture comprising a particulate material, such as hydrous kaolin, wherein at least a portion of the particulate feed is coated with an additive/liquid fuel mixture comprising at least one additive dispersed in liquid fuel. The method further comprises heating the particulate feed to heat treat, e.g., calcine, the particulate feed and burn the liquid fuel to form a heat-treated product. The liquid fuel coating can act as a secondary, indirect heat source for heat treating.

Abstract: The Rio Capim Kaolin deposit contains a lower bed of soft kaolin clay that averages 10 meters thick, and an upper bed of “hard” kaolin (“RCC hard kaolin”) that may be as thick as 6 to 8 meters. Due to their high impurity content fine particle size, cementetious nature, and high degree of particle aggregation, hard kaolins are difficult to process. Disclosed herein are compositions comprising kaolin having a particle size distribution such that at least about 90% of the kaolin has a particle size of less than 1 micron and a GE brightness of at least about 91, where the kaolin may be derived from a crude kaolin having a Fe2O3 content of at least about 1.0% by weight, and optionally comprises titania in an amount of at least about 1.5% by weight. Also disclosed herein are methods of refining the hard kaolins, such as RCC hard kaolins, by dispersing the kaolin with at least one anionic organic dispersant and at least one inorganic dispersant.