A gypsum board provided with a foamed gypsum core layer, a facing sheet over the foamed gypsum core, and a latex polymer coating layer on an outer surface of the facing sheet. The latex polymer having a glass transition temperature (Tg) of 0 to 35 F. Methods for making the board are also disclosed.

A bone repairing material comprises a composition including an -calcium sulfate hemihydrate and an autologous bone powder, wherein the bone repairing material contains 2060 weight percent of the autologous bone powder and 4080 weight percent of the -calcium sulfate hemihydrate. The bone repairing material has a particle size in the range of 501,000 m. A method for producing the bone repairing material comprises the following steps: producing the -calcium sulfate hemihydrate from a calcium sulfate dihydrate by microwave heating; grinding an autologous bone for generating the autologous bone powder; and, mixing the -calcium sulfate hemihydrate and the autologous bone powder to form the bone repairing material.

The present invention discloses a method for producing the alpha-calcium sulfate hemihydrate bone graft, which comprises the following steps: mixing calcium sulfate dihydrate and deionized water to produce calcium sulfate dihydrate paste; stirring and heating the calcium sulfate dihydrate paste at least 160 C. within 100-350 psi to produce the conversion calcium sulfate hemihydrate, filtering the conversion calcium sulfate hemihydrate with high temperature to produce the filtered calcium sulfate hemihydrate, and washing the filtered calcium sulfate hemihydrate by absolute alcohol to get the alpha-calcium sulfate hemihydrate bone graft. The present invention does not use any catalyst, possesses a high purity, high mechanical strength, and good biocompatibility, facilitates bone growth and angiogenesis, requires only 31 C., the highest temperature, during the curing process. It makes the present invention more secure in the biomedical applications.

Disclosed are various methods for reducing levels of elemental sulfur within gypsum products such as wall board. Gypsum sometimes includes increased levels of elemental sulfur. Such sulfur can be corrosive and otherwise harmful at elevated levels. The disclosure contemplates reacting the elemental sulfur with copper to copper sulfide. This reaction has the benefit of reducing the levels of elemental sulfur present within the final gypsum product. The copper can be added at any of a variety of locations in the manufacturing process. This is a very efficient method for reducing elemental sulfur in the production of gypsum products.

Disclosed are various methods for reducing levels of elemental sulfur within gypsum products such as wall board. Gypsum sometimes includes increased levels of elemental sulfur. Such sulfur can be corrosive and otherwise harmful at elevated levels. The disclosure contemplates reacting the elemental sulfur with copper to copper sulfide. This reaction has the benefit of reducing the levels of elemental sulfur present within the final gypsum product. The copper can be added at any of a variety of locations in the manufacturing process. This is a very efficient method for reducing elemental sulfur in the production of gypsum products.

Wasted gypsum boards are crushed and calcined to gypsum granular solid, and the gypsum granular solid is mixed with water to form gypsum slurry. Gypsum particles are deposited from the gypsum slurry in a crystallization tank. Heated steam is blown into the gypsum slurry at a height from surface of the gypsum slurry and down to upper of the gypsum slurry to heat the gypsum slurry and to eliminate foam on the gypsum slurry.

A method for calcining gypsum includes subjecting a composition including gypsum dihydrate to a predetermined vacuum. The method further includes maintaining the composition under the at least partial vacuum at a calcining temperature for a predetermined calcining time. The calcining temperature may be in a range from 60 C. to 125 C., or in a range from 65 C. to 85 C. The vacuum may be in a range from 25 mbar to 50 mbar. The predetermined calcining time may be in a range from 3 hours to 10 hours. The maintaining is effective to at least partially remove water of crystallization from the gypsum dihydrate to convert the composition to a product including gypsum hemihydrate.

The present disclosure relates to the technical field of phosphogypsum dehydration treatment, and provides a device for harmless treatment of phosphogypsum by calcination using high-temperature ceramsite, including a rotary kiln, a first feeding unit, a second feeding unit and a sorting assembly, where the rotary kiln includes a first rotary kiln drum and a second rotary kiln drum; a first interlayer channel is formed between the first rotary kiln drum and the second rotary kiln drum, and a head end of the first interlayer channel is connected to a head end of the first rotary kiln drum; the first feeding unit is used to input high-temperature ceramsite into the first rotary kiln drum; the second feeding unit is used to input phosphogypsum into the first interlayer channel; the mixture in the first rotary kiln drum and the phosphogypsum in the first interlayer channel can exchange heat to dehydrate the phosphogypsum; the sorting assembly is used to sort the mixture output from the first rotary kiln drum to obtain calcined phosphogypsum. The present disclosure enables high calcination and dehydration efficiency of phosphogypsum, and can achieve low-carbon harmless treatment of phosphogypsum to obtain phosphorus building gypsum.