SU971790A1 - Process for producing sorbent for absorbing mercury vapour - Google Patents

Description

The invention relates to a process for the preparation of sorbents for the absorption of mercury vapor and can be used for air purification in the chemical industry.

A known method of making a sorbent for removing mercury vapor from gas mixtures is that a porous carrier, such as activated carbon, silica gel, alumina or magnesium oxide, is impregnated with an aqueous solution of sodium thiosulfate, and then treated with an aqueous solution of mineral acid taken in excess to precipitate colloidal sulfur from. in the pores of the carrier II.

The disadvantage of this method is the presence in the gas cleaning system of corrosive and poisonous solutions of sodium thiosulfate ..

The closest to the proposed technical essence and the achieved result is a method for obtaining a sorbent for capturing mercury vapor, which consists in applying activated carbon to the activated carbon in an amount of 1-11.8 wt.% By treating the activated carbon with a mixture of gases, containing hydrogen sulfide and oxygen in a fluidized bed at 140 ° С f 2.

The disadvantage of this method of sorbent production is clogging of coal with lump sulfur, resulting in a decrease in the sorption capacity of the sorbent. Moreover, the clogging of pores occurs from the very beginning of the process of saturating the coal with sulfur from smaller pores, moreover, more and more large pores are seized. The clogging of the pores of the activated carbon by lump sulfur is a consequence of the fact that the process of interaction of hydrogen and oxygen begins at the moment of contact of their mixture in the coal pores without first redistributing one of the reactants over the active surface of the coal.

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The aim of the invention is to increase the sorption capacity of the sorbent.

The goal is achieved by the fact that according to the method of obtaining a sorbent for the absorption of mercury vapors,

25 treatment of activated carbon is suspended in two stages, the first of which is hydrogen sulfide or a mixture of hydrogen sulfide with an inert gas, and the second is an oxygen-containing oxidant in the presence of water vapor. According to the proposed method, an activated carbon saturates hydrogen sulfide by passing the latter or its mixture with some inert gas, for example hydrogen, through a layer of coal. Then a gas containing oxygen or sulfur dioxide and water vapor is passed through the coal that is already saturated with hydrogen sulfide. wet air with a temperature of 20–100 gs. A microscopic analysis of the fracture of a granule of coal saturated by the claimed method shows the equal presence of sulfur on the walls of even very small capillaries in the form of needle formations, while A rem as a microscopic analysis of coal saturated in the prototype method shows the presence of the amount of sulfur in the form of lump formations suppressed, mainly in large capillaries. Small capillaries in the latter case are filled with precipitated sulfur. Example 1. Through a 20-gram (1mW of the BLU coal is passed through a gas mixture with a temperature containing 1% hydrogen sulfide, the rest is nitrogen. To achieve carbon saturation with hydrogen sulfide (as judged by gas chromatographic analysis data showing the presence of the initial concentration hydrogen sulfide at the outlet of the glass bottle), the gas mixture is stopped. Then, through a portion of coal saturated with hydrogen sulfide, a gas mixture with a relative humidity of 98%, containing 2% sulfur dioxide, and the rest nitrogen, is passed. The temperature of the gas mixture is 95 ° C. As soon as the weight gain reaches 1.56 grams, the coal mix gas supply is stopped. The prepared adsorbent is tested for mercury vapor recovery efficiency. After the MPC reaches the adsorbent, the absorption of mercury is terminated. As a result of weighing the adsorbent, it is determined that the absorbent absorbs 2 g of mercury. Example 2. Through a 20-gram sample of coal BAU pass a gas mixture containing 1.0% of sulfur, and the rest is nitrogen. The temperature of the mixture. When the carbon is saturated with hydrogen sulfide, the gas mixture is stopped. Then through a sample of coal saturated with hydrogen sulfide, ha is passed. This mixture contains 80% oxygen and 20% nitrogen with a relative humidity of 100% and temperature. Upon reaching a gain of 1.6 g, the flow of the gas mixture is stopped. Through the prepared adsorbent air is passed with a mercury vapor content of 10 mg per 1 m of the mixture. The sorbent is saturated with mercury until a mercury vapor concentration of 0.01 mg / m appears in the air at the outlet. After that, the sample is weighed. By weighing it is determined that the adsorbent absorbs 1.9 g of mercury, which is 9.5% by weight of the amount of adsorbent through which mercury containing air flow was passed. The preparation of the sorbent according to a known method is given in examples 3 and 4. Example 3. Through a 20.0-gram weight of BAU coal (GOST 6217-52) enclosed in a glass cylinder, a gas mixture with a relative humidity of 98% and a temperature containing 1% is passed through hydrogen sulfide, 20% oxygen, the rest is nitrogen. The glass bottle is periodically weighed. When the weight gain reaches 1.62 g after the sample is pre-dried, the gas mixture is discontinued. Then, a portion of the prepared sorbent is placed in a glass tube with a diameter of 12 mm and air is passed through it with a mercury vapor content of 7-10 mg per 1 m of the mixture. With a sorbent layer thickness of 100 mm, the linear velocity of the mercury-containing air flow is 0.2 m / s. The saturation of the sorbent with mercury is carried out until the formation of mercury vapor in the air above the maximum permissible concentration (MAC) m). After that, the sorbent sample is weighed. It is obtained that the adsorbent absorbs 0.6 g of mercury. Example 4. Conditions of 1 saturation 20 g of BAC coal with sulfur from a gas mixture containing hydrogen sulfide, oxygen, water vapor and nitrogen are the same as in Example 3. When the weight gain in 6.0 g is reached, the gas mixture is stopped. The adsorbent prepared in this way is tested for the efficiency of mercury vapor absorption according to the method described in Example 1. The concentration of mercury vapors in air has exceeded the MPC since the beginning of the passage of mercury-containing air flow through the adsorbent. Thus, from the beginning of the passage of the airflow, the mercury vapor content at the outlet is 23.mg / m. Comparative data on the effectiveness of the known and proposed methods are presented in the table.

Prototype

Offered (oxidizing oxygen)

Offered (oxidizer - sulfurous anhydride) Note: - porous carrier

Claims (2)

The technical and economic effect of the implementation of the proposed method 30 is due to an increase in the degree of purification of mercury production industrial emissions from mercury vapor and a decrease in the size of adsorbents and is 22180.5 thousand rubles / year. 35 Claims of Invention A method for obtaining a sorbent for absorption of mercury vapor, including treatment of activated carbon with hydrogen sulfide and oxygen-containing oxide, 2 63 50 4.3 29 3.0 10 2.2 1.8 0.0 120 7,8 10.0 9.8 138 8.3 In order to increase the sorption capacity, the treatment is carried out in two stages, the first of which is hydrogen sulfide or a mixture of hydrogen sulfide with an inert gas, the second is an oxygen-containing oxidant in the presence of water vapor. -coal saran. Sources of information taken into account in the examination of Patent CPP 54768, cl. At 01 53/16, 07.06.71. . 2. Carbon 1972, 10, 96, p. 754756 (prototype).