RU2449948C1 - Method of producing active coal - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to production of active coals. Proposed method comprises crushing initial coal raw stock, mixing it with binding agent, i.e. coal-tar resin, and inorganic admixture, i.e. potassium hydroxide solution, granulation of produced pulp, carbonising granules and their activation. Note here that 20-40% of total amount of potassium hydroxide are pre-added to binding agent while 80-60% are introduced in coal-resin pulp in mixing. Total amount of added potassium hydroxide makes preferably 1.2 to 2.5 wt %.

EFFECT: high dichloroethane absorption, reduced time interval of activation to preset porosity.

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Description

The invention relates to the field of production of active carbons (AC) and can be used in the coal, graphite and coke industry.

A known method of producing activated carbon based on brown coal, including grinding it to a fraction of 1-2 mm, mixing the obtained grains with solid potassium or sodium hydroxide in a mass ratio of 1: 1-1: 5, carbonization, activation at 600-800 ° C for 1 hour in an inert atmosphere, followed by washing the target product with water, then an acid solution and then again with water to a neutral medium and drying (see US Pat. RF No. 2359904, CL 01/31, published on June 27, 2009) .

The disadvantage of this method is the complexity of the process and a large amount of liquid waste.

The closest to the proposed method in terms of technical nature and the achieved result is a method for producing activated carbon based on low-reaction carbon-containing raw materials, coal and petroleum asphaltites, in which the crushed feedstock is mixed with wood resin and sodium hydroxide solution in the ratio (40-45) :( 18-20) :( 33-35) :( 5-6) until a homogeneous paste is formed; then the mixture is granulated, the obtained granules are carbonized in an atmosphere of carbon dioxide and activated with water vapor, achieving a reduction in the activation process time by 20% (see RF patent No. 20133368, class C01B 31/08, published on 05/30/1994).

The disadvantage of the prototype is the insufficiently significant reduction in activation time, as well as the low adsorption capacity of the resulting activated carbon for the absorption of dichloroethane (DCE) vapors from air at a level of 18-20 wt.%.

The technical result (the purpose of the invention) is to shorten the activation time and increase the adsorption capacity of the resulting activated carbon in pairs of dichloroethane.

The goal is achieved by the proposed method, including grinding the original coal raw material, mixing it with a binder and an inorganic additive, granulating the resulting paste, carbonizing the granules and activating them with water vapor, using coal tar as a binder, and potassium oxide hydrate as an inorganic additive moreover, 20-40% of its amount is preliminarily introduced into the binder, and 80-60% into the coal tar paste at the mixing stage, while the total amount of potassium oxide hydrate introduced is S THE 1.2-2.5 wt.%.

The difference of the proposed method from the known one is that coal tar is used as a binder, and potassium oxide hydrate is used as an inorganic additive, with 20-40% of its amount pre-injected into a binder, and 80-60% in coal tar paste at the mixing stage, while the total amount of potassium oxide hydrate introduced is 1.2-2.5 wt.%.

From the scientific and technical literature, the authors do not know a method for producing activated carbon, in which coal tar is used as a binder, and potassium oxide hydrate is used as an inorganic additive, with 20-40% of its amount preliminarily added to the binder, and 80-60% in the coal tar paste at the mixing stage, while the total amount of potassium oxide hydrate introduced is 1.2-2.5 wt.%.

The essence of the invention is as follows. Reducing the activation time of carbonized granules when used as an activator of water vapor by reaction

C + H ₂ O ↑ = CO ↑ + H ₂ ↑

catalyzed by alkali metal ions, which is part of the oxide hydrate. At the same time, a larger potassium molecule is introduced at the stage of carbonization into the crystallite structure, expanding interplanar spacings and loosening the crystallite structure. Loosened layers are activated much more easily, and therefore the total effect of reducing activation time can be significantly increased. However, when introducing an alkali metal oxide hydrate, it must be remembered that with its low content this effect will be insignificant, and a large amount of its additives will increase the surface burn and sharply reduce the mechanical strength. Numerous experiments have found that the optimal amount of KOH additive to obtain the desired technical result is 1.2-2.5 wt.%.

Since the preparation of a well-formed paste is associated with enveloping as many dust particles of the binder as possible, the preliminary introduction of KOH into the binder (coal tar) favors its better distribution in the mass of granules than with the introduction of potassium oxide hydrate in the paste.

But since in addition to the uniformity of its distribution, it is necessary to provide a large amount of the necessary micropores formed in the mass of coal itself, the introduction of another part of the necessary amount of alkali into the paste facilitates the introduction of potassium into the interplanar space of crystallites, which leads to the development of micropores of optimal sizes for absorption dichloroethane vapor. To increase the adsorption capacity for DCE vapors related to medium boiling solvents (boiling point from 60 to 100 ° C), it is necessary to develop a sufficient volume of large micropores (with a size of 1.0-1.4 nm).

The method is as follows.

Coal ground to a size less than 100 microns is taken and dosed into a mixer. Then a binder (coal tar) is prepared by heating it in a reactor with a stirrer to a temperature of 50-75 ° C and KOH is metered into a heated binder in the form of an aqueous solution with a concentration of 40 wt.%, And the amount of potassium oxide hydrate should be 20-40% of its general content. The mixer is turned on and the binder and KOH are mixed for 15-20 minutes. Then include a paddle mixer, which was previously loaded with coal dust, and meter the binder therein with the addition of KOH. The ratio of coal dust and binder is maintained in the proportion of 70:30. After 3-5 minutes of mixing, the remaining amount of KOH (80-60% of its total content) is metered into the mixer in the form of an aqueous solution with a concentration of 40 wt.%. Stirring is continued for another 15-20 minutes until a homogeneous paste is obtained. The total amount of potassium oxide hydrate introduced should be 1.2-2.5 wt.%. Then they turn on a screw granulator, on which dies are installed with a hole diameter of 1-5 mm, and the resulting paste is molded. The granules leaving the screw granulator are dried in a stream of hot air at a temperature of 80-100 ° C for 1.0-1.5 hours. Dry granules are carbonized at a temperature of 450 ° C with a heating rate to this temperature of 10-12 ° C / min and volatilized at a temperature of 750 ° C. Activation is carried out at a temperature of 870 ° C with superheated steam supplied at the rate of 5-7 kg per 1 kg of AC until the total porosity of 0.8-1.0 cm ³ / g develops.

The reduction in activation time to the development of a given total porosity (0.8-1.0 cm ³ / g) was 40-60% compared with the activation time of the same sample without the addition of potassium oxide hydrate. The adsorption capacity for DCE vapors of the obtained activated carbon was 35-50 wt.%.

The sizes of micropores and other types of pores are determined by measuring adsorption isotherms with subsequent calculation of micropore parameters according to the Dubinin-Radushkevich equation (see N. Keltsev, “Fundamentals of adsorption technology.” - M .: Chemistry, 1984. - p.31, 32 65-68).

The determination of the total pore volume is carried out according to GOST 17219-71 "Method for determining the total pore volume by water".

Determination of the adsorption capacity for pairs of DCE is carried out on a dynamic device described in a monograph by V. Mukhin. (Mukhin V.M., Tarasov A.V., Klushin V.N. “Active coals of Russia.” - M .: Metallurgy, 2000. - p. 146) under the following conditions:

- air temperature 25 ° C;

- layer length 10 cm;

- air flow rate 0.2 m / s;

- concentration of dichloroethane 20 mg / l.

The breakthrough of dichloroethane is fixed chromatographically.

Example 1

Take 7 kg of crushed coal brand SS (GOST R 51588-2000) and place it in the chamber of a two-blade mixer. Then, 3 kg of coal tar (KUS) (GOST 14-7-100-89) is poured into the reactor (GOST 14-7-100-89), it is heated to a temperature of 50-75 ° C. Take 24 g of alkali and dissolve in 36 ml of water to obtain a solution of KOH with a concentration of 40 wt.%. The resulting KOH solution is metered into the reactor and the stirrer is turned on. Mixing lead 15-20 minutes. They include a paddle mixer, in which coal dust is loaded, and a binder (coal tar) with KOH additive is dosed there. After 3-5 minutes of mixing, a pre-prepared solution containing 96 g of KOH in the form of an aqueous solution with a concentration of 40 wt.% Is added to the mixer, while the total amount of KOH introduced is 1.2 wt.%. Stirring is continued for 15-20 minutes until a homogeneous paste is obtained. They include a screw granulator, on which dies with 3 mm diameter holes are installed, and paste is formed. The obtained granules are dried in a stream of hot air at a temperature of 80-100 ° C for 1-1.5 hours. Dry granules are carbonized at a temperature of 450 ° C with a heating rate of 10-12 ° C / min and volatilized at a temperature of 750 ° C. Activation is carried out at a temperature of 870 ° C with superheated steam supplied at the rate of 5-7 kg per 1 kg of AC before the development of a total porosity of 0.92 cm ³ / g.

The reduction in activation time to the development of a given total porosity (0.92 cm ³ ) was 40% compared with the activation time of the same sample without the addition of potassium oxide hydrate. The adsorption capacity of the obtained activated carbon for DCE vapor was 35 wt.%.

Example 2

The implementation of the method as in example 1, except that the amount of KOH introduced is 2.5 wt.%, Which required its introduction into the KUS in the amount of 100 g, and into the paste - 150 g. The resulting activated carbon had a vapor adsorption capacity dichloroethane 42 wt.%, and the reduction in activation time to the development of a given total porosity (0.92 cm ³ / g) was 50% compared with the activation time of the same sample without the addition of potassium oxide hydrate.

Example 3

The implementation of the method as in example 1, except that the amount of KOH introduced is 1.8 wt.%, Which required its introduction in KUS in the amount of 54 g, and in the paste - 126 g. The resulting activated carbon had a vapor adsorption capacity dichloroethane 50 wt.%, and the reduction in activation time to the development of a given total porosity (0.92 cm ³ / g) was 60% compared with the activation time of the same sample without the addition of potassium oxide hydrate.

The proposed method allows to reduce the activation time by a factor of 2–3 until a predetermined total porosity is achieved and to increase the adsorption capacity of the obtained activated carbon by dichloroethane vapor by 15–30% as compared to the prototype (see RF patent No. 20133368, CL 01/31, publ. 05/30/1994).

The introduction of potassium oxide hydrate into the coal tar ensures uniform development of the microporous structure in the entire volume of the granules. Moreover, if its quantity introduced into the resin is less than 20 wt.%, Then there is insufficient uniformity of its distribution, thereby reducing the adsorption capacity and increasing the development time of the total porosity. And in the case of introducing into the resin the amount of the initial KOH of more than 40 wt.%, Mainly large macropores develop, which are ballasts and give a low adsorption capacity for DCE.

The introduction of more than 80 wt.%, Total KOH into the coal tar composition at the stage of pasta preparation leads to the development of both the necessary micropores and larger mesopores with a size of more than 2 nm having a lower adsorption potential, and therefore, the adsorption capacity for dichloroethane is reduced . If less than 60 wt.% Of the total KOH is added to the coal tar composition, the volume of potassium ions is deficient for introduction of crystallites into the interplanar space.

Claims (2)

1. A method of producing activated carbon, including grinding the original coal raw material, mixing it with a binder and an inorganic additive, granulating the resulting paste, carbonizing the granules and activating them, characterized in that coal tar is used as a binder, and oxide hydrate is used as an inorganic additive potassium in the form of an aqueous solution, wherein 20-40% of the potassium oxide hydrate is preliminarily introduced into the binder, and 80-60% into the coal tar paste at the mixing stage. 2. The method according to claim 1, characterized in that the total amount of potassium oxide hydrate introduced is 1.2-2.5 wt%.