The present disclosure relates generally to methods for producing stucco compositions useful in making gypsum products. One aspect of the disclosure is a method for producing a stucco composition using dielectric calcination. Another aspect of the disclosure is a production process for a gypsum product using a stucco composition prepared by dielectric calcination.

In general, the present invention is directed to a method of making a gypsum board. The method comprises: applying a phosphorus containing compound to a first gypsum composition to provide a phosphorus modified gypsum composition; calcining the phosphorus modified gypsum composition to provide a calcined gypsum composition; preparing a gypsum slurry by combining water and the calcined gypsum composition; depositing the gypsum slurry on a first facing material; providing a second facing material on the gypsum slurry; and allowing the calcined gypsum to convert to calcium sulfate dihydrate.

This invention discloses a synthetic gypsum and gypsum boards produced therefrom. Limestone (Calcium Carbonate), slaked lime (calcium hydroxide), water, and sulfuric acid are mixed, and alpha hemihydrate gypsum is optionally added as crystal seed to produce synthetic gypsum. The synthetic gypsum is then used to make gypsum boards. The gypsum board produced according to this invention contains at least 10% alpha hemihydrate gypsum.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.

A process for producing a mineral foam includes (i) separately preparing one or more slurries of cement, and an aqueous foam for which a D50 of bubbles is less than or equal to 400 m; (ii) homogenizing the one or more slurries of cement with the aqueous foam to obtain a slurry of foamed cement; (iii) casting the slurry of foamed cement and leaving the cast slurry of foamed cement to set.

Composition for building materials comprises of fly ash from flue gas desulfurization. The fly ash (CaSO.sub.4 anhydrite), obtained from circulating fluidized bed flue gas desulfurization, is mixed with binder reactants at a ratio of 9:1. It's mainly used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, plasterboards and so on. The binder reactants compose of 70% CaSO.sub.4.H.sub.2O, 10% Na.sub.2SO.sub.4, 10% CaO, 5% NaOH, 05% cement and 05% starch. When the binder reactants are mixed with fly ash and water (30% to 40% of the above total weight), the hydration process of CaSO.sub.4 anhydrite is accelerated.

A method for measuring the weights of phase components in a calcium sulphate material, e.g., gypsum or stucco, in particular for measuring the weights of DH, HH and AIII phases. The method includes (a) weighing a given amount of calcium sulphate material at ambient temperature; (b) placing the weighed calcium sulphate material in a moisture balance at ambient temperature; (c) drying the calcium sulphate material at temperature between 40 C. and 50 C.; (d) waiting until the weight is constant; (e) weighing the dried calcium sulphate material; (f) calculating the weight gain between (a) and (e), the weight gain being related to the amount of AIII phases in the calcium sulphate material.

In the present disclosure, a method of forming a gypsum panel is disclosed. The method comprises: providing a first facing material, forming a starch slurry by combining starch and water at a shear rate of 3,000 rpm or more, providing the starch slurry onto the first facing material, depositing a gypsum slurry comprising stucco and water onto the starch slurry on the first facing material, providing a second facing material on the gypsum slurry, and allowing the stucco to convert to calcium sulfate dihydrate.

A method of recovering desalinated activated alumina (AA) beads from a composition including salt laden (high salt absorbed) activated alumna (AA) beads and free anions and free cations, comprising the step of electrodialysis of the composition to reduce salt content of the activated alumina (AA) beads to produce a stream comprising the desalinated activated alumina (AA) beads.

In the present disclosure, a method of forming a gypsum panel is disclosed. The method comprises: providing a first facing material, forming a starch slurry by combining starch and water at a shear rate of 3,000 rpm or more, providing the starch slurry onto the first facing material, depositing a gypsum slurry comprising stucco and water onto the starch slurry on the first facing material, providing a second facing material on the gypsum slurry, and allowing the stucco to convert to calcium sulfate dihydrate.