RU2595125C1 - Method of producing activated bentonite powder - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of activated bentonite powder, which is used in drilling, metallurgy, construction, adsorption and catalysis processes. Technical result of the proposed method is higher efficiency, as well as reduced duration of activation process due to reduction of the equipment used in production of activated bentonite powder. Proposed method involves after crushing in a roll crusher at room temperature bentonite is first transfered to a propeller mixer with preset clay-to-water ratio and intensely mixed for one hour to obtain a homogeneous suspension, and then the obtained suspension is added with Na₂CO₃ in the amount of 1.5-2 % of the bentonite weight and stirred for 30 more minutes.

EFFECT: proposed method allows to increase efficiency and simplify the technology of producing activated bentonite powder, as well as reduce duration of the activation process.

1 cl, 2 ex, 1 tbl, 2 dwg

Description

The invention relates to a technology for producing activated bentonite powder, which is used in drilling, metallurgy, construction, adsorption and catalysis processes.

A known method of activation of clay materials in two stages. At the first stage, simple salts and / or bases of sodium-containing compounds are introduced into the moistened clay material as an activator in order to replace sodium cations adsorbed on the clay surface with sodium cations. In the second stage, complexing compounds of sodium are introduced under stirring conditions in order to replace sodium cations of magnesium and iron cations remaining in bentonite. The number of introduced activators is determined by the formulas that take into account the composition and concentration of the exchange cations. After completion of the second stage, the bentonite paste is dried, then ground in a ball mill and used in the manufacture of foundry molds [RF Patent 32044587, B22C 1/00, publ. 09/27/1995]. The disadvantages of this method is the complexity of the activation technology in two stages and the use of two types of salt.

A known method of activating bentonite clay by mixing it at a moisture content of 20-45% with sodium-containing reagents - activators. During this process, the action of steam increases the humidity and temperature of the mixture to 40-75 ° C. This increases the solubility of the activator and the diffusion rate of sodium cations to the exchange positions. Activated bentonite is dried to a residual moisture content of 10%, crushed, and the physicomechanical and colloidal chemical properties are determined. [RF patent No. 2199504, С04В 33/04, publ. 02.27.2003]. The proposed method is time-consuming, since it requires continuous monitoring and regulation of the humidity and temperature of bentonite clay with water vapor, which is complicated by the large volumes of activated clay, which takes place under industrial conditions.

A known method of producing activated bentonite, including preliminary crushing of bentonite clay and its subsequent joint grinding with rhombic crystalline hydrate of soda Na ₂ CO ₃ H ₂ O (or mineral - termonatrite) in an amount of 1.5-2% by weight of clay for 0.5- 1.0 hours [RF Patent No. 2297434, C1, C04B 33/04, publ. 04/20/2007]. The disadvantages of this method are the need to create an independent technology for the production of activator Na ₂ CO ₃ H ₂ O and the requirement to obtain fractions of bentonite particles with dimensions of 0.071-0.08 mm for joint grinding of sodium-containing activator and clay,

As a prototype, a method of activating bentonite clay was adopted, including grinding it in a roller mill, chemical modification in two stages with sodium salt (1.25%) in an aqueous medium at room temperature and a clay: water ratio of 1: 1.35. The first stage involves 40-50 minutes of mixing clay, water and sodium salt in a wet ball mill. For the second stage, a suspension of bentonite with an activator from a ball mill is transferred to a container with a propeller stirrer and activation is continued for 120 minutes. The suspension is then fed to a tower spray dryer to obtain a powder. [RF patent №2101258, C1, С04В 33/04, publ. 01/10/1998]. The disadvantages of this method are the three-hour duration of the processes of activation and dispersion of bentonite in the presence of an activator, which is a coagulant and counteracts the grinding of clay, as well as the presence in the technology of the energy-intensive stage of wet grinding of clay in a ball mill of low efficiency under the conditions of the coagulant.

The technical result of the proposed method is to increase the efficiency of the technology, as well as reducing the duration of the activation process by reducing the equipment used in the production of activated bentonite powder.

The technical result is achieved due to the proposed method, where, after grinding in a roll crusher at room temperature, bentonite is first transferred to a propeller mixer at a given clay-water ratio and intensively mixed for one hour until a homogeneous suspension is obtained, and then Na is added to the resulting suspension ₂ CO ₃ in an amount of 1.5-2% by weight of bentonite and stirred for another 30 minutes

Bentonite after grinding in a roll crusher at room temperature is transferred to a propeller mixer at a given clay-water ratio (for example, 1: 1.35) and intensively mixed in the absence of Na ₂ CO ₃ until a homogeneous suspension is obtained. Moreover, over a period of less than an hour, clay disperses with a stirrer and water (blooming) and the specific surface area of bentonite particles grows. After that, in order to activate the clay, Na ₂ CO ₃ in the amount of 1.5-2% by weight of bentonite is fed into the propeller mixer during mixing. Moreover, the high specific surface of bentonite particles in suspension contributes to an increase in the rate of cation exchange and a rapid decrease in the concentration of coagulating cations on a solid surface. The activation process ends 30 minutes after the introduction of Na ₂ CO ₃ . Next, the suspension is fed to a tower spray dryer.

The dependences of bentonite colloidality on the concentration of Na ₂ CO ₃ and activation time are shown in FIG. 1 and FIG. 2.

Powdered bentonite obtained by the proposed method, in comparison with the prototype, has a higher swelling index (Table. 1).

Example 1

40 g of natural bentonite clay, crushed in a roller crusher to a piece size of not more than 7 mm and a moisture content of 20%, is mixed with water at a ratio of bentonite and water of 1: 1.35, obtaining a concentrated suspension. The suspension is then mixed in a container with a 3-blade propeller stirrer for 60 minutes. During this time, pieces of bentonite manage to disperse. Next, 2% Na ₂ CO _{3 was} added to the suspension and stirring was continued for another 30 minutes. Then bentonite is dried.

Example 2

One kilogram of natural bentonite clay, crushed in a roller crusher to a piece size of not more than 7 mm and a moisture content of 20%, is mixed with water at a ratio of bentonite and water of 1: 1.35, obtaining a concentrated suspension. The suspension is then mixed in a container with a paddle propeller stirrer for 60 minutes. During this time, pieces of bentonite manage to disperse. Next, 2% Na ₂ CO _{3 was} added to the suspension and stirring was continued for another 30 minutes. Then bentonite is dried.

Claims (1)

A method of obtaining activated bentonite powder, including grinding clay in a roller mill, subsequent dispersion and activation with a sodium salt in a propeller stirrer with a clay to water ratio of 1: 1.35, drying the resulting suspension in a tower spray dryer, characterized in that after grinding in a roller mill at room temperature, bentonite is first transferred to a propeller stirrer at a given clay-water ratio and stirred vigorously for one hour until a homogeneous suspension is obtained. ligation, and then Na ₂ CO ₃ in the amount of 1.5-2% by weight of bentonite is added to the resulting suspension and stirred for another 30 minutes.

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