A calcined gypsum treatment apparatus has an agitating type of cooler provided with a cooling region for cooling the calcined gypsum, and a moisture supplying device for incorporating moisture into the calcined gypsum. The moisture supplying device includes a humid gas-feeding port which introduces humid gas including moisture or steam, directly into the cooling region. The calcined gypsum is introduced through a calcined gypsum introduction port into the cooling region, and the moisture is incorporated into the calcined gypsum to modify the calcined gypsum. The humid gas-feeding port is positioned in vicinity to the calcined gypsum introduction port so as to allow the spouted or delivered flow of the humid gas to be brought into contact with the calcined gypsum immediately after introduced into the cooling region.

A multitubular rotary heat exchanger has a stationary shielding unit. The shielding unit is positioned in close proximity to a tube plate outside a heating or cooling region. A stationary surface of the shielding unit is positioned in opposition to and in close proximity to an end opening of a heat transfer tube moving in an upper zone of the heating or cooling region, thereby transiently reducing or restricting the flow rate of the thermal medium fluid flowing through the heat transfer tube moving in the upper zone.

The invention pertains to a method for stabilizing stucco wherein a fresh stucco is provided; water is added to the fresh stucco to obtain moistened stucco, and the moistened stucco is maintained at a temperature of at least 30 C. for a time interval of at least 30 minutes to obtain a stabilized stucco.

The process allows inter alia for an easy adjustment of the activity of the stabilized stucco, which is useful to e.g. adjust setting time of a corresponding stucco slurry. The invention further pertains to a method for producing gypsum plasterboards, wherein a stabilized stucco obtained with the above method is used.

A method for continuously forming gypsum-based panels of high fixing strength comprises the steps of: forming a mixture comprising stucco, non-pregelatinized migratory starch, glass fibre, fluidizer and water; casting the mixture in a continuous band; maintaining the band under conditions sufficient for the stucco to form an interlocking matrix of set gypsum; cutting the band to form one or more wet panel precursors; and drying the wet panel precursor to form one or more gypsum-based panels. The weight ratio of water to stucco in the mixture is less than 0.7; the stucco is present in the mixture in an amount of over 60 wt % relative to the total solids content of the mixture; the starch is present in the mixture in an amount of over 3 wt % relative to the the stucco; the glass fibre is present in the mixture in an amount of over 1 wt % relative to the stucco; the fluidizer is is present in the mixture in an amount of at least 0.1 wt % relative to the stucco; and the density of the gypsum-based panel is greater than 700 kg/m.

A method for continuously forming gypsum-based panels of high fixing strength comprises the steps of: forming a mixture comprising stucco, non-pregelatinized migratory starch, glass fibre, fluidizer and water; casting the mixture in a continuous band; maintaining the band under conditions sufficient for the stucco to form an interlocking matrix of set gypsum; cutting the band to form one or more wet panel precursors; and drying the wet panel precursor to form one or more gypsum-based panels. The weight ratio of water to stucco in the mixture is less than 0.7; the stucco is present in the mixture in an amount of over 60 wt % relative to the total solids content of the mixture; the starch is present in the mixture in an amount of over 3 wt % relative to the the stucco; the glass fibre is present in the mixture in an amount of over 1 wt % relative to the stucco; the fluidizer is is present in the mixture in an amount of at least 0.1 wt % relative to the stucco; and the density of the gypsum-based panel is greater than 700 kg/m.

Additives including sulfur-containing compounds are used in methods of treating synthetic gypsum. The additives can thermally stabilize heavy metals, such as mercury. This thermal stabilization reduces mercury release from the synthetic gypsum. Illustrative, non-limiting examples of sulfur-containing compounds include inorganic sulfides, organic sulfides, organic compounds containing nitrogen and sulfur, organic compounds containing oxygen and sulfur, and polymers containing sulfur.

Additives including sulfur-containing compounds are used in methods of treating synthetic gypsum. The additives can thermally stabilize heavy metals, such as mercury. This thermal stabilization reduces mercury release from the synthetic gypsum. Illustrative, non-limiting examples of sulfur-containing compounds include inorganic sulfides, organic sulfides, organic compounds containing nitrogen and sulfur, organic compounds containing oxygen and sulfur, and polymers containing sulfur.

A system for conditioning stucco particulate material includes a vessel having separation chamber in communication with a holding chamber having a holding volume therein. The conditioning system includes the holding volume sufficient to condition the stucco particulate material therein and/or a control system configured to delay discharge of the stucco particulate material from the holding chamber. The system for conditioning stucco particulate material is configured to increase residence time of the stucco particulate material in the holding chamber to promote calcining conditioning therein.

Additives including sulfur-containing compounds are used in methods of treating synthetic gypsum. The additives can thermally stabilize heavy metals, such as mercury. This thermal stabilization reduces mercury release from the synthetic gypsum. Illustrative, non-limiting examples of sulfur-containing compounds include inorganic sulfides, organic sulfides, organic compounds containing nitrogen and sulfur, organic compounds containing oxygen and sulfur, and polymers containing sulfur.

Additives including sulfur-containing compounds are used in methods of treating synthetic gypsum. The additives can thermally stabilize heavy metals, such as mercury. This thermal stabilization reduces mercury release from the synthetic gypsum. Illustrative, non-limiting examples of sulfur-containing compounds include inorganic sulfides, organic sulfides, organic compounds containing nitrogen and sulfur, organic compounds containing oxygen and sulfur, and polymers containing sulfur.