Processing equipment and method for a pulverulent calcium sulphate material and novel hydraulic binder
OwnerChristian Dusselinventor
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Abstract
A method for processing a pulverulent calcium sulphate material in order to obtain a hydraulic binder is described, including combining the following two successive processing steps: (a) heating the pulverulent material in a curing tunnel (1) at a temperature of 220-360° C., under conditions suitable for primarily forming an α-type calcium sulphate, and (b) subjecting the heated material to a thermal quenching step in a cooling apparatus (2), with a cold, dry gas to stabilise the α anhydrite and to prevent its conversion into other crystallographic types. The method provides a novel hydraulic binder with an α anhydrite content of more than 35 wt. %, and with improved strength and behavior in fire resistance properties.
Claims17
A process for treatment of a pulverulent material comprising calcium sulfate so as to prepare a hydraulic binder comprising a stable mixture of α anhydrite and bassanite, in which a weight proportion of a anhydrite is greater than 35%, wherein the two following successive treatment steps are performed in combination:
- (a) heating the pulverulent material to a temperature between 220° C. and 360° C. in the presence of water vapor to form mostly calcium sulfate of a variety,
- (b) subjecting the heated pulverulent material to thermal quenching by cooling by at least 150° C. in less than 15 minutes by means of a gas injected under pressure.
An apparatus for the treatment of an initial material present in pulverulent form comprising:
- a heating tunnel having an upstream and a downstream end,
- means for supplying the initial pulverulent material to the upstream end of said heating tunnel,
- longitudinal troughs juxtaposed in the heating tunnel,
- combs of a heat conductive material inserted in the troughs and of such shape as to divide the mass of pulverulent material contained in the troughs,
- adjustable means for vibrating said troughs to cause movement of the pulverulent material from the upstream end toward the downstream end,
- adjustable heaters located above the troughs in the heating tunnel,
- a cooling device having an upstream end and a downstream end and located at a lower level relative to the heating tunnel,
- a receptacle of elongated form extending in the cooling device to contain the pulverulent material,
- adjustable means for vibrating said receptacle so as to cause movement of the pulverulent material from the upstream toward the downstream end of the receptacle,
- means for passage by gravity of the pulverulent material from the downstream end of the heating tunnel into the upstream end of the cooling device,
- means for injecting cold dry compressed air into the passage means, the cold dry compressed air having a water vapor content less than about 5% mass of vapor relative to total mass of the gas, and a temperature less than about 50° C.,
- means for injection of compressed air into the cooling device, and
- means for removing the pulverulent material from the downstream end of the cooling device.
A hydraulic binder containing calcium sulfate, said calcium sulfate comprising a stable mixture of α anhydrite and of bassanite, in which a weight proportion of α anhydrite is greater than 35%.
Dependencies are inferred from the claim text.