RU2147924C1 - Sorbent for absorption of mercury vapor and method of its producing - Google Patents

Abstract

FIELD: chemical technology, sorbents. SUBSTANCE: invention relates to production of sorbents based on activated carbon and used for scrubbing technological and ventilation exhausting gases from mercury vapor. Sorbent consists of activated carbon (total pore volume is 0.5-0.75 cm³/g) and insoluble sulfur applied on its in the amount 2-10 wt.-% of carbon mass. Sorbent is prepared by treatment of activated carbon taken mainly as granules (size is 1.0-5.0 mm) at first with carbon disulfide vapor or air-steam mixture with carbon sulfide for 9-10 h and then with steam for 1 h at vapors temperature 100-120 C. EFFECT: increased absorbing capacity of sorbent, broadened exploitation pattern. 3 cl, 3 ex

Description

 The invention relates to the production of carbon-based sorbents, in particular to the production of activated carbon (AC) sorbents for purifying process and ventilation exhaust gases from mercury.

 AC as a sorbent is widely used due to the possibility of achieving the necessary degree of purification due to the porous structure and the possibility of regeneration of the spent product. In its pure form, it has a low mercury absorption capacity. Therefore, it is used with numerous mercury-binding additives. One of the known additives is sulfur.

 A number of modifications of AC sulfur are known as a result of the addition of sulfur to AC (EP 0271618, class B 01 J 20/20, publ. 06/19/86), the use of AC in the form of a suspension in an aqueous solution of sulfuric acid (SU aut. Certificate. N 292356, class B 01 D 53/02, publ. 05.05.75), sulfur deposition on AC when heating a mixture of AC with fine sulfur powder (GB application N 2122916, class B 01 D 53/02, publ. 25.01.84; EP application N 0102467, CL B 01 J 20/20, publ. 14.03.84), treatment of AC with sulfur dioxide or hydrogen sulfide (Finnish patent N 57907, CL B 01 D 53/02, publ. 10.05.77).

 In known sorbents, AC contains elemental crystalline sulfur on the surface and in the pores, which, as is known, is well soluble in carbon disulfide, benzene, toluene, and alcohols.

 When extracting mercury by known sorbents, media in which these substances are present, especially carbon disulfide, should be avoided, which limits the scope of application of these sorbents. In addition, the degree of extraction of mercury with their help is not more than 84-88%.

 Closest to the proposed invention is a sorbent for the absorption of mercury vapor, containing AC and sulfur, according to patent EP 0271618. This sorbent is selected as the closest analogue (prototype).

 A known method of producing a sorbent for the absorption of mercury vapor, including treating the AC with a solution of elemental sulfur in carbon disulfide as a solvent, removing excess solvent by filtration and drying (EP 0271618, class B 01 J 20/20, 1986).

 The disadvantage of this method is the impossibility of using it to precipitate sulfur which is insoluble in the above substances on AC.

 This method is selected as the closest analogue (prototype).

 The technical problem to which the present invention is directed is the development of a sorbent for the absorption of mercury vapor, which is capable of adsorption even in the presence of carbon disulfide, benzene, toluene and alcohols in the treatment facilities.

 The technical result that can be obtained using the inventions is to increase the absorption capacity of the sorbent and the expansion of operational capabilities.

The problem is solved in that the sorbent for the absorption of mercury vapor, containing AC and sulfur, according to the invention contains sulfur-insoluble sulfur in the amount of 2-10 wt.% By weight of AC, while AC has a total pore volume of 0.5-0.75 cm ³ / g

In the method for producing a sorbent for absorbing mercury vapor, comprising treating AC with carbon disulfide, according to the invention, carbon disulfide vapors or their mixture with air are passed through AC for 9-10 hours, after which they are treated with water vapor for 1 hour at 100-120 ^o C, moreover, in a preferred embodiment, AC is used in the form of granules with a size of 1.0-5.0 mm

Distinctive features of the proposed sorbent are the following features:
- the content of sulfur insoluble in carbon disulfide,
- in an amount of 2-10 wt.% by weight of AC,
- the total pore volume of AC, equal to 0.5-0.75 cm ³ / year

Distinctive features of the method are the following features:
- transmission of carbon disulfide vapors or mixtures thereof with air through the AC for 9-10 hours,
- treatment with water vapor for 1 hour at 100-120 ^o C, and also in a preferred embodiment,
- the use of AC in the form of granules with a size of 1.0-5.0 mm

 The inventive sorbent is based on the known insolubility of the used type of sulfur in carbon disulfide, benzene, toluene and alcohols. This allows mercury to be extracted almost completely from any medium. The product of the interaction of insoluble sulfur with mercury is mercury sulfide, easily removable, chemically and thermally stable.

 The required content of the indicated sulfur on the AC as a carrier was determined experimentally.

 As it turned out, the declared limit of 2-10 wt.% Is sufficient to extract 99-99.9% of mercury.

 A concentration below 2% does not provide the necessary sorbent capacity, and above 10% it is not advisable due to a decrease in the degree of purification due to clogging of the porous structure of the AC sulfur.

The method is suitable for the deposition of insoluble sulfur on any type of AC (powdery, lumpy, granular, etc.), but the best results were achieved on AC in the form of granules, whose surface is immeasurably more developed. The optimal granule sizes were determined to achieve the total pore volume, which, as it turned out, is necessary and sufficient in the range of 0.5-0.75 cm ³ / g.

 Sorbent is prepared as follows.

Vapor disulfide vapor or a steam-air mixture containing carbon disulfide is passed through a granular AC layer, which is more economical. After 9-10 hours of treatment, water vapor is passed at a temperature of 100-120 ^° C. for one hour to distill off unreacted carbon disulfide. To achieve the required sulfur content, the treatment is repeated, and the maximum required sulfur content (10 wt.%) Is obtained in 5-7 cycles.

As a result of the interaction of these reagents, insoluble sulfur deposited on the AC is obtained. At the same time, the pore volume of AC decreases slightly (to 0.5-0.55 cm ³ / g at 10 wt.% - the sulfur content).

 The resulting sorbent is resistant to solvents, hydrophobic, high absorption capacity.

Example 1. An air mixture containing 5 g / m ^{3 of} carbon disulfide is passed through a 10-cm-high layer of AC grade ART in a column with a diameter of 25 mm. The temperature of the mixture is 20 ^o C. After 9 hours, the gas mixture is stopped, and water vapor with a temperature of 110 ^o C is passed through the AC layer saturated with carbon disulfide for 60 minutes. After distillation of the carbon disulfide (unreacted), the supply of water vapor is stopped.

The resulting sorbent contains 2 wt.% Insoluble in carbon disulfide sulfur. It is tested for the efficiency of trapping mercury vapor by passing hydrogen through it containing 10 mg / m ^{3 of} mercury and 100 mg / m ^{3 of} carbon disulfide. The degree of purification of the vapor-gas mixture from mercury is 99.7%. The sorbent capacity for mercury is 2 wt.%.

 Example 2. Use a granular AC with a grain size of 1.0-5.0 mm The processing conditions are the same as in example 1, and the treatment is repeated 6 times to achieve an insoluble sulfur content of 10 wt.%.

 The test conditions are the same as in example 1. The degree of purification of the vapor-gas mixture from mercury is 99.0%. The sorbent capacity for mercury is 10 wt.%.

 Example 3. Use a granular AC, as in example 2. Its processing under the conditions described in example 1, is repeated until the insoluble sulfur content of 11 wt.%. The test results according to the conditions of example 1 show a degree of purification equal to 85%, and the capacity of the sorbent for mercury 8 wt.%.

 Examples confirm the possibility of extracting mercury from gases containing carbon disulfide. An example of such a gas mixture is the production of caustic soda.

 As for the sorbents for the prototypes, they generally cannot be used for the purification of gases containing carbon disulfide, since the active part of the sorbent, crystalline sulfur, is dissolved in it.

 The inventive sorbent is produced in an industrial environment using chemical equipment.

Claims (3)

1. Sorbent for the absorption of mercury vapor, containing activated carbon and sulfur, characterized in that as sulfur it contains insoluble sulfur in an amount of 2 to 10 wt.% By weight of coal, while activated carbon has a total pore volume of 0.5 - 0 75 cm ³ / g 2. A method of producing a sorbent for absorbing mercury vapor, including treating activated carbon with carbon disulfide, characterized in that the carbon disulfide vapor or a mixture thereof with air is passed through activated carbon for 9 to 10 hours, after which it is treated with water vapor for 1 hour at a temperature vapor 100 - 120 ^o C.  3. The method according to claim 2, characterized in that the activated carbon is used in the form of granules with a size of 1.0 to 5.0 mm