JPS6227358A - Manufacture of alpha type hemihydrate gypsum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for converting dihydrate gypsum slurry into α-type hemihydrate gypsum by treating it with pressurized water, and in particular, a method that allows the operation to be performed continuously. Regarding the method.

(Prior art) α-type hemihydrate gypsum is not only a type of gypsum that is promising as a new building material because of its high strength after setting, but also has very low expansion and contraction after setting and hardening, so it is used for automobiles, etc. It is often used for aircraft models (form material).

Known manufacturing methods include a pressurized aqueous solution method and a pressurized steam method, but both are batch-type and unsuitable for large-volume production.

The present inventors have developed a method for continuously producing large-capacity α-type hemihydrate gypsum by converting the conventional batch-type production method into a continuous method. A method was proposed in which a slurry whose amount was maintained at 101% by weight or less was subjected to one continuous pressurized hydrothermal treatment so as to remain at a temperature of 140'0 or more for an appropriate period of time. (Tokuko Showa 5
(Refer to Publication No. 9-3406) However, when α-type hemihydrate gypsum is continuously produced by the method proposed above, a small amount of raw material dihydrate gypsum is often mixed in the α-type hemihydrate gypsum produced. observed.

(Problems to be Solved by the Invention) The present invention seeks to provide a method for producing α-type hemihydrate gypsum that can eliminate the drawbacks of the methods already proposed by the present inventors.

(Means for Solving the Problems) That is, the present invention involves changing the sodium citrate content to (1, (M weight, Gypsum dihydrate slurry maintained at the following temperature was continuously subjected to pressure hydrothermal treatment in a high pressure hydrothermal treatment tank so that it remained at a temperature of 140 °C or higher for an appropriate time.
In the method for producing type hemihydrate gypsum, the α-type hemihydrate gypsum production method is characterized in that sequential pressurized hydrothermal treatment is performed in a plurality of nine pressurized hydrothermal treatment tanks arranged in series.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

Supply gypsum from line 1, sodium citrate from line 2, and water from line 3 to dihydrate gypsum slurry adjustment tank 4, where a homogeneous dihydrate gypsum slurry containing the desired amount of sodium citrate is adjusted. This slurry is sent to the first pressurized hydrothermal treatment tank 6 via line 5, where it is subjected to pressurized hydrothermal treatment at a temperature of 140°C or higher under an appropriate pressure, and the average residence time of the slurry in the nuclide 6 is determined. Continuous 1c at a rate such that it is 1 to 1.5 hours! 2 is supplied to the pressurized hydrothermal treatment tank 8 via line 7. In the second pressurized hydrothermal treatment tank 8, the slurry is also subjected to pressurized hydrothermal treatment under appropriate pressure and at a temperature of 140° O or higher, at a rate such that the average residence time of the slurry in the nuclide 8 is 1 to 1.5 hours. The produced α-type hemihydrate gypsum slurry is continuously extracted through line 9 while being pressurized.

The extracted α-type hemihydrate gypsum slurry is also guided to a liquid cyclone or thickener 10 under pressure and concentrated, and the concentrated slurry is passed through a line 11 to a dryer 13.
The gypsum is sent through a line 14 to a crusher 15 for pulverization, and through a line 16 a product α-type hemihydrate gypsum is obtained.

On the other hand, the F liquid separated by the liquid cyclone or thickener 10 is transferred to the line 12, and is transferred to the dihydrate gypsum slurry adjustment tank 4.
The water is then sent back to the factory and reused as metered water.

Next, a reference example and an example will be given to demonstrate the effects of the present invention.

[Reference Example 1] When dihydrate gypsum slurry was subjected to pressurized hydrothermal treatment under the following conditions in the first stage of pressurized hydrothermal treatment tank, a small amount of the raw material dihydrate gypsum was observed in the outlet slurry without being transferred to 0 temperature. Sura IJ-a degree Citric sodium concentration Residence time 140°0 20i1 [11csO, Ofii4
1 hour [Example] When pressurized hydrothermal treatment tanks were connected in series in two stages of KL and dihydrate gypsum was subjected to pressure hydrothermal treatment under the following conditions, the morphology of the stone in the loss slurry from the second stage was all α-type hemihydrate gypsum. No dihydrate gypsum, a raw material, was observed.

1st stage 140°0. 2Qij-J1% 0.0
1wt% 1 hour 2nd stage 140°0 2Qij amount%
[101 weight skin 1 hour (effect) As described above, the present inventor installed multiple stages of pressurized hydrothermal treatment tanks in series to transfer all of the raw material dihydrate gypsum to α-type hemihydrate gypsum, and in the product, This is to prevent contamination with gypsum dihydrate.

[Brief explanation of drawings]

The accompanying drawings are flow diagrams illustrating embodiments of the invention. Sub-agent: 1) Akira Sub-agent Ryo Hagi Hara - Sub-agent Atsuo Yasunishi

Claims (1)

[Claims] When transferring dihydrate gypsum slurry to α-type hemihydrate gypsum through pressure hydrothermal treatment, the sodium citrate content was reduced to 0.01.
In a method for producing α-type hemihydrate gypsum by continuously pressurized hydrothermal treatment in a pressurized hydrothermal treatment tank so that dihydrate gypsum slurry maintained at a weight percent or less is retained at a temperature of 140° C. or higher for an appropriate time, a plurality of gypsum dihydrates arranged in series are used. A method for producing α-type hemihydrate gypsum, characterized by sequentially performing pressurized hydrothermal treatment in a pressurized hydrothermal treatment tank.