SU1590118A1 - Method of cleaning waste gases from nitrogen oxides - Google Patents

Abstract

The invention relates to a technology for the catalytic purification of gaseous emissions of NO X in the presence of CH 4, used in the chemical industry and power engineering and allowing a reduction in the concentration of combustible impurities. The exhaust gases are mixed with flue gases, then with natural gas and passed through a PD / AL 2 O 3 catalyst at 700 - 750 ° C, where NO X is reduced to N 2. Then excess air is added to the gases relative to combustible impurities. m and the mixture of gases withstand at least 0.05 s. After that, the gas to be purified is passed through the second catalyst of the GIAP-3 brand - a catalyst for methane conversion based on NIO / AL 2O 3, where the oxidation of combustible is taking place. The temperature in the oxidation zone is maintained 20-40 ° C higher than in the zone of the first catalyst. The content of combustible (CO + H 2 + CH 4) in the exhaust gases is reduced to 0.002% by volume, the concentration of CO is reduced to (1-5) .10 -3% by volume.

Description

The invention relates to the field of purification of gas emissions from nitrogen oxides and can be used in the chemical industry, as well as energy. the geek.

The purpose of the invention is to reduce the concentration of combustible impurities.

An example. The tail gases of the production of nitric acid in the amount of 30 thousand, content 0.25. vol.% NOy, 2.8 vol.% 0, the rest nitrogen, under a pressure of 3.0 atm, is fed to the tail gas cleaning unit. When mixed with flue gases (4,600 nm / h) and natural gas for reduction (330), tail gases acquire temperature.

Then they pass the first recovery zone. Here on the catalyst APK-2 (palladium on) the redox reaction is carried out at 700-750 ° C. At the exit of. the first zone gases have a composition, vol.% Wx 5-10 3; ,one; Co 0.12, - CH4.0.2; HgOJL. These gases are mixed with air (1200 nm / h). The residence time of gases from the point of entry of air to the catalyst of the oxidation zone is 0.05 s. In the oxidation zone, 3 tons of methane conversion catalyst GIAP-3-6N (5% H10 / A1203) are placed. At the outlet of the oxidation zone, the gases have a temperature of 740-770 ° C and contain, vol.%: Sc 5, -10, Oa 0.2; , CO is less than 0.001; CH, less than 0.0005j

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$ 2 less than 0.0005. The experiments were conducted for 240 h. The unit continued to operate for / fOOO h and more.

The conditions of work given in Example 1 ensure that the purity of the exhaust gases is achieved in accordance with modern requirements. The CO content is less than the maximum permissible concentration (MPC), the degree of purification for nitrogen oxides is not lower than 98%. j Example 2. Same as: and with hjiepe 1, but natural gas consumption for reduction 310. At the outlet of the first zone, the composition of the gases changes, em-, vol.%: CO 0.06; SN. OZ. At the outlet of the oxidation zone, the temperature of the gases is 720 ° C, the content of vol.%: NOx I lO 02 0.25, CO 0.05, CH. 0.001, Hi 0.001 .-

 Example 3. The same as in Nera 1, but the tail gas flow rate is 45 thousand, the flow rate — reflux gases Y 900 nm / h, natural gas to the conversion is 500 nm / h. The residence time of gases from the point of entry to the catalyst of the oxidation zone is 0.04 s. The composition of the gases after the oxidation zone, vol,%:

N0 5-10 0 0.5; CO CH 0,002; H 2. less than 0.0005. CO content is greater than the MPC.

Example 4. Same as in example 1, but the air flow rate is 790, the gas temperature after the first catcher is 700 ° C, after the second layer C. The concentration of CO at the outlet is 0.06% by volume, t . higher MPC,

The proposed method allows to reduce the content of combustible () in the exhaust gas to 0.002% by volume compared to 0.06% by volume in the known, and the content of toxic carbon monoxide is reduced (1-5).% Compared to 0 , 05 in the well-known ,, reaches values below the MPC. The oxidation reaction partially proceeds in the homogeneous phase, which makes it possible to successfully use at the oxidation stage a simple catalytic system GIAP-3, widely used in industry for the conversion of methane.

Claims (1)

Formula isob R ee n i A method of purifying waste gases from nitrogen oxides, including passing them in a mixture with natural gas through a catalyst containing palladium on alumina at a temperature of 700-750 C and then through a second catalyst, characterized in that, in order to reduce the concentration of combustible impurities, before the second catalyst air is added to the gas to be purified in excess with respect to combustible impurities and the mixture is kept for at least 0.05 s. A methane-based conversion catalyst based on nickel oxide on ox-oxide is used as the second catalyst. yes aluminum -No temperature in the second catalyst zone is maintained at 20-40 with Bbmie, than in the first catalyst zone.