SU1722544A1 - Method of cleaning effluent gases from mercury - Google Patents

Abstract

The invention relates to a mercury gas purification technology used in the metallurgical industry and allowing an increase in the degree of purification. The gas to be purified, containing mercury, is in contact with a bubble-foam gas scrubber with an aqueous solution of an inorganic salt or acid. The feed rate of the purified gases is 0.35-0.70 m / s. The volume ratio of the aqueous solution and gas is (1: 350) - (1: 530). The temperature of the aqueous solution is from 5 to minus 5 ° C. The degree of purification from mercury is 96.2% when using a solution of n-nitric acid and 97.7-99.0% when using a solution of sodium polysulfide or hydrochloric acid, table 1.

Description

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The invention relates to methods for purifying waste process gases from mercury and can be used in the metallurgical and other industries.

A known method of purifying waste process gases from mercury containing sulfur dioxide, sodium thiocyanate, dissolved in an aqueous solution of sulfuric acid. Sulfuric acid solution has acidity that oxidizes mercury.

The disadvantage of this method is the low degree of purification of gases from mercury (88%) and, as a result, significant emissions of mercury into the atmosphere, since the gas is not brought to sanitary standards for mercury content.

The closest to the proposed method is the method of purifying gases from mercury by the halide method. In this method, the purification is carried out with an irrigated aqueous solution of NaCI, KJ, CuCIa, in the presence of activated carbon or a solution of HM03.

The disadvantage of this method is the low degree of gas purification from mercury (up to 68.0%).

The aim of the invention is to increase the degree of purification.

This goal is achieved by the fact that according to the method of purification of waste process gases from mercury, including supplying the gas to be purified, supplying the sorbent, contacting the gas with the sorbent and trapping mercury, cleaning the gas is carried out with a layer of mobile foam with a sorbent cooled to (+5) - (-5) ° C, with a feed gas flow rate of 0.35-0.70 m / s, while the volume ratio of the sorbent solution and gas is from 1: 350 to 1: 530.

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The essence of the proposed method is as follows.

The purification of waste process gases from mercury is carried out in the apparatus of the foam mode, the gas through the diffuser podvoits with a speed of 0.35-0.7 m / s (in full section of the apparatus) in the sublattice space. Lattice - perforated sheet with regularly spaced holes of any shape. A sorbent solution (irrigating liquid) is fed to the grate cooled to (+5) - (- 5) ° C at an irrigation intensity of 3.4-6.0 m / m2 h and in a liquid: gas ratio of 1: 350-1: 530 . Passing through the openings of the lattice, the gas foams the liquid on it. The foam layer, which absorbs mercury from the gas, moves along the grate to the overflow threshold and is poured through it into the receiving tank, where the foam, which does not have static stability, is destroyed. From the receiving tank, it is pumped by the pump into the tank where the irrigating fluid is located. After a 7- to 10-fold turnover, the irrigating liquid is removed from the process for sedimentation and further processing.

This not only increases the degree of mercury capture, but also reduces the consumption of sorbent, as in the proposed technological mode, the sorbent solution is able to pass gas in a volume 10 times larger than the prototype. By increasing the speed of the passed process gas to 0.35-0.7 m / s, the productivity of the process is doubled.

PRI me R. A mercury-containing gas with a mercury content of 40.7 mg / m3 and a volume of 30 l / min is fed into the sublattice area of the foam apparatus. The gas is introduced into the sublattice region at a rate. 0.7 m / s in the full cross section of the bubble-foam apparatus. A 5% solution of sodium polysulfide, cooled to a MINUS of 5 ° C, with an irrigation rate of 4.0 m / m2 h, is fed to the apparatus grate. The gas, the passage through the holes of the lattice, foams the liquid on the lattice, forming a layer of mobile foam, thereby increasing the contact surface of the gas with the solution of sorbent (sodium polysulfide). The foam, which absorbs the mercury from the gas and cleans it, is drained through the overflow threshold. to the receiving tank, where it is settled and pumped again for irrigation to the foam apparatus. The purified gas to control the residual mercury content is passed through wet filters with an absorption solution (solution of aqua regia). In this example, the residual mercury content in the purified gas is 0.41 mg / m3, and the degree of mercury capture is respectively -99.0%.

Similar results were obtained when

conducting research with various sorbents, for example, with a 2% aqueous solution of hydrochloric acid, with a 2% aqueous solution of nitric acid, with a 2% aqueous solution of sodium polysulfide, etc.

The results of the experiments are given

in the table.

As can be seen from the table, as the temperature of the sorbent solution decreases, its absorption capacity increases. but

at temperatures below minus 5 ° C, the viscosity of the sorbent solution increases, and therefore, process gas overshoot is observed, which drastically reduces the degree of mercury trapping. Increase gas feed rate

and the ratio of sorbent: gas above the proposed limit also reduces the degree of mercury trapping, since the sorbent solution does not cope with such a volume of gas. If the gas velocity and the volume ratio of the sorbent: gas are below the proposed limit, shrinking of the layer of moving foam is observed, the stability of the foam bubbles is deteriorated, thereby reducing the interfacial contact surface, which leads to a decrease in the degree of mercury trapping.

Thus, the use of the proposed method of purification of mercury process off-gases makes it possible to increase the degree of

Claims (1)

capture of mercury up to 96.2% versus 68.0% when using NMO3 and up to 97.7-99.0%. when using other reagents. The invention of the method of purification of exhaust gases from mercury, including contacting the gases to be purified with an aqueous solution of an inorganic salt or acid, characterized in that, in order to increase the degree of purification, the process of contacting lead in a bubble-foam gas scrubber at a feed rate of purified gases of 0.35-0.70 m / s, volume ratio of aqueous solution and gas (1: 350) - (1: 530) and temperature of the aqueous solution in the range of +5 to -5 ° C. Editor T. Laeorenko Tehred M. Morgenthal Order 1013 Circulation: Subscription VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab 4/5 Production and Publishing Combine Patent, Uzhgorod, Gagarin st., 101 Proofreader M. Pojo