Recycling method of dihydrate gypsum from waste gypsum boards

Patent metadata

Field	Value
Publication number	US-2020123055-A1
Application number	US-201916659598-A
Country	US
Kind code	A1
Filing date	Oct 22, 2019
Priority date	Oct 23, 2018
Publication date	Apr 23, 2020
Grant date	—

Abstract

Gypsum derived from waste gypsum boards is calcined and converted into gypsum granules including hemihydrate and/or anhydrous type III gypsum. The calcined gypsum granules are dropped into water to prepare a gypsum slurry. Then, dihydrate gypsum particles are crystalized in the slurry. The temperature of the gypsum granules just before being dropped into the water is 90° C. or higher.

First claim

What is claimed is:

1 . A method of recycling dihydrate gypsum from waste gypsum boards, the method comprising:
calcining gypsum derived from waste gypsum boards to convert the gypsum into hemihydrate and/or anhydrous type III gypsum granules; dropping the gypsum granules after calcination into water to mix the gypsum granules with water to prepare a gypsum slurry; and crystalizing dihydrate gypsum particles in the gypsum slurry; wherein a temperature of the gypsum granules just before being dropped into the water is 90° C. or higher.

2 . The recycling method of dihydrate gypsum from waste gypsum boards according to claim 1 , wherein the gypsum granules are dropped into the water without being pulverized after the step of calcining.

3 . The recycling method of dihydrate gypsum from waste gypsum boards according to claim 2 , wherein the temperature of the gypsum granules just before being dropped into the water is maintained at 90° C. or higher due to residual heat from the step of calcining.

Assignees

• Tokuyama Corp

Inventors

• Hiranaka Shingo
• Matsuo Kentaro
• Kataoka Makoto

Classifications

• C04B11/032

  for the wet process, e.g. dehydrating in solution or under saturated vapour conditions, {i.e. to obtain alpha-hemihydrate (C04B11/0281 - C04B11/0288 take precedence)} · CPC title

• C04B11/262 Primary

  waste gypsum other than phosphogypsum · CPC title

• C04B28/14

  containing calcium sulfate cements {(gypsum-paper plates E04C)} · CPC title

• C04B11/26 Primary

  {strating from chemical gypsum}; starting from phosphogypsum or from waste, e.g. purification products of smoke (C04B11/02 takes precedence; chemical purification of smoke, fumes or exhaust gases B01D53/00 {purification of gypsum C01F11/46}) · CPC title