JPH0686296B2 - α-type hemihydrate gypsum manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing α-type hemihydrate gypsum by continuously subjecting a dihydrate gypsum slurry to hydrothermal treatment under pressure.

[Conventional technology]

Since α-type hemihydrate gypsum obtained by heat treatment under pressure has fluidity with a smaller amount of water mixed than calcined gypsum (β-type hemihydrate gypsum), it is possible to reduce the cost of drying when producing gypsum board, and It is considered to be a promising raw material for the production of gypsum board because of its high strength after Japanese setting.

As the α-type hemihydrate gypsum production method, a pressurized aqueous solution method and a pressurized steam method are known, but all of them are batch type and unsuitable as a large-capacity production method.

The present inventors relate to a method for continuously producing an industrially large-capacity α-type hemihydrate gypsum by continuously converting a conventional batch-type production method into an amount of sodium citrate used as a habit modifier. Slurry maintained below 0.01 wt% 140
We proposed a method of continuous hydrothermal treatment under pressure so that it stays at a temperature above ℃ for a suitable time. (See Japanese Examined Patent Publication No. 59-3406) When manufacturing α-type hemihydrate gypsum by the method already proposed above, 140 ° C
A method for solid-liquid separation of the above α-type hemihydrate gypsum slurry under pressure has been used. However, the solid-liquid separation device under pressure has a problem that there are many troubles particularly in extracting solids, which is an obstacle to continuous operation.

[Problems to be solved by the invention]

100 ℃ for slurry above 140 ℃ extracted from the pressurized hydrothermal bath
Only the heat is recovered and the rest is released to the atmosphere as vapor. This is because it is said that α-type hemihydrate gypsum rapidly transforms into dihydrate gypsum at temperatures below 100 ° C, and it is necessary to perform solid-liquid separation at the highest temperature possible. If solid-liquid separation is attempted at 100 ° C or higher, solid-liquid separation will inevitably occur in the pressure vessel, and handling of the solid side will be extremely difficult, apart from the liquid.

[Object of the Invention]

In view of the above-mentioned state of the art, the present invention aims to provide a method for producing α-type hemihydrate gypsum that can solve the above problems.

[Means for solving problems]

The present invention relates to a method for producing α-type hemihydrate gypsum by continuously subjecting a dihydrate gypsum slurry to a pressurized hydrothermal treatment, wherein an α-hemihydrate gypsum slurry flowing out from a pressurized hydrothermal treatment tank and a dihydrate gypsum slurry supplied to the heated water treatment tank A heat exchanger is installed between the α-hemihydrate gypsum slurry temperature of 90 to 10
A method for producing α-type hemihydrate gypsum, which is characterized in that solid-liquid separation is performed under atmospheric pressure at 0 ° C.

That is, according to the present invention, when solid-liquid separation of α-type hemihydrate gypsum slurry is performed, the α-type hemihydrate gypsum is extracted from the pressurized hydrothermal treatment tank at 140 ° C. or higher.
A heat exchanger is provided between the mold hemihydrate gypsum slurry line and the dihydrate gypsum slurry line supplied to the pressurized hydrothermal treatment tank for heat exchange, and if necessary, a cooler is provided at the α hemihydrate gypsum slurry outlet line of the heat exchanger. Finally, the α-type hemihydrate gypsum slurry at 100 ° C. to 90 ° C. is sent to the solid-liquid separation step for solid-liquid separation under atmospheric pressure.

[Action]

(1) Since an α-type hemihydrate gypsum slurry at 100 ° C or less is obtained, solid-liquid separation can be performed under atmospheric pressure.

(2) If the temperature is 90 ° C. or higher, there is no concern about the transfer from α-type hemihydrate gypsum to dihydrate gypsum (it transfers at 90 ° C. or lower). An embodiment of the present invention will be described with reference to the flowchart shown in FIG. To do.

Gypsum dihydrate is supplied from line 1, sodium citrate is supplied from line 2, and water is supplied from the line 3 to a dihydrate gypsum slurry adjusting tank 4, where a homogeneous dihydrate gypsum slurry containing a desired amount of sodium citrate is prepared. This slurry is sent to the heat exchange gas 6 via the line 5 to recover heat, and continuously sent to the pressurized hydrothermal tank 8 via the line 7. In the pressurized hydrothermal tank 8, the gypsum dihydrate crystals dissolve and transfer to α-type hemihydrate gypsum.

The generated α-type hemihydrate gypsum slurry passes through line 9 and heat exchange air 6
Is finally cooled to 100 ° C. to 90 ° C. in a cooler 11 via a line 10 which is sent to and heat is recovered, and is sent to a solid-liquid separator 13 via a line 12 to be solid-liquid separated under atmospheric pressure to obtain a solid. Α
The type hemihydrate gypsum is sent to a dryer 15 via a line 14 to be dried, and further sent to a crusher 17 via a line 16 to be crushed to obtain a product α-type hemihydrate gypsum from a line 18.

On the other hand, the liquid separated by the solid-liquid separator 13 is returned to the dihydrate gypsum adjusting tank 4 through the line 19 and reused as make-up water.

Next, examples will be given to show the effects of the present invention.

〔Example〕

The hydration rate of the α-type hemihydrate gypsum slurry was measured, and the results shown in FIG. 2 were obtained. It can be seen that α-type hemihydrate gypsum is stable without conversion to dihydrate gypsum at 90 ° C or higher, but dihydration proceeds at 90 ° C or lower.

〔The invention's effect〕

As described above, the present invention enables efficient solid-liquid separation under atmospheric pressure by maintaining the α-type hemihydrate gypsum slurry withdrawn from the pressurized hydrothermal treatment tank at 90 ° C to 100 ° C.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention, and FIG. 2 is an explanatory view of the embodiment.

Claims (1)

[Claims] 1. A method for producing α-type hemihydrate gypsum by continuously subjecting a dihydrate gypsum slurry to hydrothermal treatment under pressure, wherein α-hemihydrate gypsum slurry flowing out from a hydrothermal treatment tank under pressure and dihydrate supplied to the heated water treatment tank A heat exchanger was installed between the gypsum slurry and the temperature of α-hemihydrate gypsum slurry flowing out of the pressurized hydrothermal treatment tank at 90
A method for producing α-type hemihydrate gypsum, which comprises maintaining the temperature at -100 ° C and performing solid-liquid separation under atmospheric pressure.