A process for the continuous preparation of alpha-calcium sulphate hemihydrate and a particulate gypsum

Patent metadata

Field	Value
Publication number	US-2024116810-A1
Application number	US-202218263033-A
Country	US
Kind code	A1
Filing date	Feb 22, 2022
Priority date	Mar 19, 2021
Publication date	Apr 11, 2024
Grant date	—

Abstract

The present application describes a process for the continuous production of alpha-calcium sulphate hemihydrate, the process comprising the steps of: providing particulate gypsum; providing water; mixing the particulate gypsum and the water to form a gypsum slurry; and maintaining said gypsum slurry under raised pressure and temperature to convert the particulate gypsum into alpha-calcium sulphate hemihydrate and provide an alpha-calcium sulphate hemihydrate slurry. Additionally, the particulate gypsum comprises a D10 value greater than or equal to 2 μm, a D90 value smaller than or equal to 90 μm and a D50 value smaller than or equal to 25 μm. Particulate gypsum for use in the process is also provided.

First claim

1 - 15 . (canceled)

16 . A process for the continuous production of alpha-calcium sulphate hemihydrate, the process comprising:
providing particulate gypsum; providing water; mixing said particulate gypsum and said water to form a gypsum slurry; and maintaining said gypsum slurry under raised pressure and temperature to convert said particulate gypsum into alpha-calcium sulphate hemihydrate and provide an alpha-calcium sulphate hemihydrate slurry, wherein said particulate gypsum has a D10 value greater than or equal to 2 μm, a D90 value smaller than or equal to 90 μm and a D50 value smaller than or equal to 25 μm.

17 . The process of claim 16 , wherein said particulate gypsum has a D50 value smaller than or equal to 20 μm.

18 . The process of claim 17 , wherein said particulate gypsum has a D50 value smaller than or equal to 15 μm.

19 . The process of claim 16 , wherein said raised temperature is in the range 110° C. to 170° C. inclusive.

20 . The process of claim 16 , wherein said raised pressure is in the range 0.15 MPa to 0.80 MPa inclusive.

21 . The process of claim 16 , wherein a gypsum particle within said gypsum slurry is maintained under conditions of raised temperature and pressure for a mean residence time within the range 10 minutes to 120 minutes inclusive.

22 . The process of claim 16 , wherein said gypsum slurry comprises a water to gypsum ratio of between 0.4 and 1.5 by weight inclusive.

23 . The process of claim 16 , wherein said gypsum slurry comprises a Brookfield viscosity in the range of 15 to 0.5 cP inclusive at 80° C.

24 . The process of claim 16 , wherein the process further comprises grinding said particulate gypsum to reduce the size of particles therein.

25 . The process of claim 16 , wherein providing particulate gypsum comprises substantially continuously providing particulate gypsum.

26 . The process of claim 16 , wherein the providing of water comprises substantially continuously providing water.

27 . The process of claim 16 , wherein the maintaining said gypsum slurry under raised pressure and temperature to convert said particulate gypsum into alpha-calcium sulphate hemihydrate and provide an alpha-calcium sulphate hemihydrate slurry comprises holding said gypsum slurry within a calcination vessel.

28 . The process of claim 16 , wherein the process comprises removing water from said alpha-calcium sulphate hemihydrate slurry.

29 . The process of claim 28 , wherein the providing water comprises mixing the water removed from the alpha-calcium sulphate hemihydrate slurry with additional water.

30 . Particulate gypsum for use in the process of claim 16 , said particulate gypsum having a D10 value greater than or equal to 2 μm, a D90 value smaller than or equal to 90 μm and a D50 value smaller than or equal to 25 μm.

Assignees

• Saint Gobain Placo

Inventors

• Francy Olivier
• Magaud Lionel
• Colombo Jöel
• Tran Binh

Classifications

• C04B11/06 Primary

  starting from anhydrite · CPC title

• C04B11/002

  Mixtures of different CaSO4-modifications, e.g. plaster of Paris and anhydrite, used as cements · CPC title

• C04B11/0282 Primary

  Autoclaves, e.g. using chariots · CPC title