Recycling method of dihydrate gypsum from waste gypsum boards

Patent metadata

Field	Value
Publication number	US-10947155-B2
Application number	US-201916659598-A
Country	US
Kind code	B2
Filing date	Oct 22, 2019
Priority date	Oct 23, 2018
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

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

• C04B28/14

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

• C04B11/262 Primary

  waste gypsum other than phosphogypsum · CPC title

• 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

• C04B11/26 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