CN114506872A - Method for preparing anhydrous gypsum at normal temperature and pressure - Google Patents

Abstract

The invention discloses a method for preparing anhydrous gypsum at normal temperature and normal pressure, and belongs to the technical field of gypsum production. The method comprises the following steps: selecting any hydrated gypsum as a raw material, and preparing a sulfuric acid solution with a certain concentration; fully wetting the hydrated gypsum by using a prepared sulfuric acid solution; reacting the fully wetted gypsum at normal temperature and normal pressure; and washing after the reaction is finished to obtain the anhydrous gypsum product. The method effectively reduces the energy consumption and the time consumption for dehydrating the hydrated gypsum and has higher social benefit and economic benefit.

Description

A kind of method for preparing anhydrite at normal temperature and normal pressure

technical field

The invention belongs to the technical field of gypsum production, and in particular relates to a method for preparing anhydrite at normal temperature and pressure.

Background technique

Anhydrite is widely used in various industries, such as polishing powder, paper filler, gas desiccant, and medical gypsum bandage, as well as metallurgy, agriculture, etc. Anhydrite can be crushed in place of gypsum for soil treatment, and during soil treatment, a ton of anhydrite contains more calcium than a ton of gypsum because gypsum contains about 21% water. Anhydrite also has a higher solubility, which aids the rapid absorption of calcium ions by the soil. In addition, anhydrite is used with gypsum as gypsum in the construction industry, joint compound, wallboard and other products. In sulfuric acid production, anhydrite is also used as a source of sulfur.

The traditional anhydrite production methods are mainly dehydrating hydrated gypsum under high temperature and high pressure and mining anhydrite raw ore. These methods have high equipment requirements, complex operation, huge energy consumption, and the abundance of anhydrite raw ore is far less than that of gypsum.

SUMMARY OF THE INVENTION

In view of the shortcomings and deficiencies existing in the prior art, the purpose of the present invention is to provide a gypsum dehydration method different from the above-mentioned high temperature and high pressure method. The method provided by the invention is to wet the hydrated gypsum with a sulfuric acid solution under normal temperature and normal pressure, so as to realize the phase transition from gypsum to anhydrite. The method is simple to operate, and the solid product after phase transition can be washed with water or organic solution to obtain anhydrite.

The technical scheme that the present invention solves the above-mentioned technical problems is as follows:

A method for preparing anhydrous gypsum at room temperature and normal pressure, adding sulfuric acid solution on the surface of hydrated gypsum at room temperature, standing to generate anhydrite, and washing the solid product with ethanol or methanol to obtain anhydrite. The specific operation steps are as follows:

1. Prepare the sulfuric acid solution of 1~9 mol/kg, and use it to wet the hydrated gypsum to obtain the wetted solid;

2. Let stand the solid obtained in step 1);

3. Wash the solid after standing in step 2) to obtain the product anhydrite solid product.

Description of drawings

Fig. 1 is the SEM image of Example 1 of the present invention before treatment.

FIG. 2 is the SEM image after the treatment of Example 1 of the present invention.

Figure 3 is a comparison diagram of the XRD and standard cards before treatment in Example 1-3 of the present invention. PDF#00-033-0311 is a standard card of dihydrate gypsum. From the figure, it can be seen that the main phases before treatment are two Gypsum.

Figure 4 is a comparison diagram of the XRD and standard cards after treatment in Examples 1-3 of the present invention, PDF#00-037-1496 is a standard card of anhydrite, and it can be seen from the figure that the main phase after treatment is no Gypsum.

Detailed ways

The present invention will be further described below with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1

A method for preparing anhydrite at normal temperature and pressure, the specific operation steps are as follows:

Take 0.1 g of gypsum dihydrate and wet it with 20 μL of 1.8 mol/kg sulfuric acid solution, with a solid-liquid ratio of 4.6, and let it stand at 25 °C for 24 h. The solid product obtained after standing was washed and then subjected to relevant SEM and XRD tests (description of drawings Fig. 1-Fig. 4). The experimental results show that the dihydrate gypsum is transformed into anhydrous gypsum phase under the action of interfacial sulfuric acid.

Example 2

A method for preparing anhydrite at normal temperature and pressure, the specific operation steps are as follows:

Take 0.1 g of gypsum dihydrate, wet it with 20 μL of 3.2 mol/kg sulfuric acid solution, the solid-liquid ratio is 4.3, and stand at 25 °C for 12 h. The experimental results showed that the dihydrate gypsum was transformed into the anhydrite phase under the action of interfacial sulfuric acid (Fig. 4).

Example 3

A method for preparing anhydrite at normal temperature and pressure, the specific operation steps are as follows:

Take 0.1 g of gypsum dihydrate, wet it with 20 μL of 5.6 mol/kg sulfuric acid solution, the solid-liquid ratio is 3.8, and let it stand at 25 °C for 4 h. The experimental results showed that the dihydrate gypsum was transformed into anhydrous gypsum phase under the action of interfacial sulfuric acid (Fig. 4).

Claims (6)

1. The method for preparing the anhydrous gypsum at normal temperature and normal pressure is characterized by comprising the following steps:

preparing a sulfuric acid solution, and wetting the hydrated gypsum solid;

standing the wetted solid of step 1);

washing the solid after standing in the step 2) to obtain the anhydrous gypsum solid product.

2. The method of claim 1, wherein: the hydrated gypsum comprises natural dihydrate or hemihydrate gypsum minerals; comprises flue gas desulfurization gypsum; including gypsum and calcined gypsum produced by natural sources, or the phosphate industry and some other industries.

3. The method as claimed in claim 1, wherein the concentration of sulfuric acid in the sulfuric acid solution in the step 1) is 1-9 mol/kg.

4. The method according to claim 1, wherein the solid-to-liquid ratio of the aqueous gypsum to the sulfuric acid solution in step 1) is 1:1 to 100: 1.

5. The method according to claim 1, wherein the standing temperature in the step 2) is 15-60 ℃ and the time is 0-36 hours.

6. The method of claim 1, wherein the washing solution of step 3) is ethanol or methanol.

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