Methods for Forming Silicates of Calcium

A method includes forming a reaction bed containing feed agglomerates in a reaction chamber by heating the feed agglomerates. Individual feed agglomerates initially contain particles of a gypsum source and of a silicon source approximately homogeneously distributed throughout the individual agglomerates. The gypsum and silicon in the feed agglomerates react during the heating in the reaction chamber and, thereby, form processed agglomerates that contain silicates of calcium and an increased amount of amorphous silicon compared to the feed agglomerates before the heating. The method includes generating off gas from the reaction bed, the off gas containing oxides of sulfur, and removing the processed agglomerates from the reaction chamber.