CN114506872A

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

Info

Publication number: CN114506872A
Application number: CN202210006295.8A
Authority: CN
Inventors: 张静; 王春雳; 李文静
Original assignee: University of Chinese Academy of Sciences
Current assignee: University of Chinese Academy of Sciences
Priority date: 2022-01-05
Filing date: 2022-01-05
Publication date: 2022-05-17

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

Method for preparing anhydrous gypsum at normal temperature and pressure

Technical Field

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

Background

Anhydrous gypsum is used in a wide variety of industries, for example, as a polishing powder, a paper filler, a gas desiccant, and a medical plaster bandage, and also in metallurgy, agriculture, and the like. Anhydrous gypsum can be crushed for soil treatment instead of gypsum, and one ton of anhydrous gypsum contains more calcium than one ton of gypsum during soil treatment because gypsum contains about 21% water. The anhydrous gypsum also has higher solubility, and is beneficial to the rapid absorption of calcium ions by soil. In addition, anhydrite is also used with gypsum as construction gypsum, joint compounds, wallboard, and other products. Anhydrite is also used as a source of sulfur in sulfuric acid production.

The traditional anhydrous gypsum production approaches are mainly to dehydrate hydrated gypsum and mine anhydrous gypsum raw ore under high temperature and high pressure, and have high requirements on equipment, complex operation and extremely high energy consumption, and the abundance of the anhydrous gypsum raw ore is far less than that of gypsum.

Disclosure of Invention

Aiming at the defects and shortcomings of the prior art, the invention aims to provide a gypsum dehydration method which is different from the high-temperature high-pressure method. The method provided by the invention is to wet the hydrated gypsum by a sulfuric acid solution at normal temperature and normal pressure to realize the phase change from gypsum to anhydrous gypsum. The method is simple to operate, and the solid product after phase change is washed by water or organic solution to obtain the anhydrous gypsum.

The technical scheme for solving the technical problems is as follows:

a process for preparing anhydrous gypsum at ordinary temp and pressure includes such steps as adding sulfuric acid solution to the surface of hydrated gypsum, laying aside to generate anhydrous gypsum, and washing the solid product with alcohol or methanol. The specific operation steps are as follows:

1. preparing 1-9 mol/kg of sulfuric acid solution, and wetting hydrated gypsum with the sulfuric acid solution to obtain a wetted solid;

2. standing the solid obtained in the step 1);

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

Drawings

FIG. 1 is a SEM photograph of a sample before being processed in example 1 of the present invention.

FIG. 2 is an SEM photograph of the treated film of example 1.

FIG. 3 is a comparison graph of XRD and standard cards before treatment in examples 1-3 of the present invention, and PDF # 00-033-.

FIG. 4 is a comparison of XRD and standard card after treatment in examples 1-3 of the present invention, and PDF # 00-037-.

Detailed Description

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

Example 1

A method for preparing anhydrous gypsum at normal temperature and normal pressure comprises the following specific operation steps:

0.1 g of dihydrate gypsum is wetted with 20 mu L of 1.8 mol/kg sulfuric acid solution, the solid-to-liquid ratio is 4.6, and the mixture is kept stand for 24 h at 25 ℃. The solid product obtained after standing was washed and subjected to the relevant SEM and XRD tests (figures 1-4). Test results show that the dihydrate gypsum is converted into an anhydrous gypsum phase under the action of interfacial sulfuric acid.

Example 2

0.1 g of dihydrate gypsum is wetted with 20 mu L of 3.2 mol/kg sulfuric acid solution with the solid-liquid ratio of 4.3, and is kept stand for 12 h at 25 ℃. The results of the tests show that dihydrate gypsum is converted into the anhydrous gypsum phase by the action of interfacial sulfuric acid (fig. 4).

Example 3

0.1 g of dihydrate gypsum is wetted with 20 mu L of 5.6 mol/kg sulfuric acid solution with the solid-liquid ratio of 3.8, and is kept stand for 4 h at 25 ℃. The results of the tests show that the dihydrate gypsum is converted into the anhydrous gypsum phase by the action of the interfacial sulfuric acid (figure 4).

Claims

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.