DE1278060B - Process for removing nitrogen oxide from gas mixtures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY ^ GERMAN mj9G & PATENT OFFICE . CL:

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EDITORIAL

German class: 26 d- 8/01

Number: 1278 060

File number: P 12 78 060.8-43 (G 28308)

Registration date : November 5, 1959

Opening day: September 19, 1968

The invention relates to a method for removing nitrogen oxide from gas mixtures, such as coke oven gas, Remote gas or the like, whereby the nitrogen oxide initially through the action of silent electrical discharges, Ozone or the like, oxidized and the reaction products, such as nitrogen dioxide, nitrosates, etc., then can be removed by washing with an alkaline aqueous solution.

The practical tests on coke oven gas treated in this way have shown that, although the NO concentration the deposits of nitrosates and resins that are characteristic of NO have been reduced cannot be prevented to a sufficient extent. It is true that a significant proportion of these are separated Reaction products already in the part of the apparatus in which the gas, for example by an electrical Brush discharge is treated, but it is unsatisfactory that z. B. in the decomposition of the coke oven gas by freezing, NO resins accumulate in the exchange cross-section of the ethylene fraction and there, as is known, cause the danger of an explosion.

One of the oldest known methods of removing the nitrogen oxide contained in the coke oven gas consists in scrubbing the gas with alkaline solutions of lower oxides of sulfur, whereby it is assumed that the nitrogen oxide bound during the wash essentially as nitrosohydroxylamine sulfonate will. However, this known method has not proven itself in practice because of this reaction runs very imperfectly.

In the majority of the known methods for removing nitrogen oxide from other gases, the NO is first _{oxidized to NO 2} and this is washed out of the gas with a suitable scrubbing agent.

One of the earliest of these processes involves the use of chromate solutions for oxidation in the later mainly oxygen or ozone are used, which latter either the gas added in the form of ozonated oxygen or by irradiation with ultraviolet light from the in combustible gases almost always present oxygen is generated. Similar implementations of the Nitrogen oxides with the oxygen contained in the gas are increased with a long residence time of the gas Temperature (100 ° C).

In the known processes, oil washes or lye washes are used to remove the reaction products.

It has been shown, however, that it is not possible with these means alone to remove the NO or the process for removing nitrogen oxide from it
Gas mixtures

Applicant:

Linde Aktiengesellschaft, 6200 Wiesbaden

Named as inventor:

Dr.-Ing. Ernst Karwat, 8023 Pullach

resulting reaction products reliably from the downstream system parts, for example from the low-temperature part a coke oven gas separation plant, and that the well-known lye washes no guarantee for a complete washing out of all disruptive components, including the Resin formers polymerize to suspended solids

ao offer the gas.

The invention is therefore based on the object of avoiding the disadvantages of the known methods and to provide a method which reliably removes the nitrogen oxide and its reaction products made possible from gas mixtures.

This is achieved according to the invention in that a detergent for the reaction products alkaline reducing agent solution is used.

In the process of the invention, the reaction products formed after the oxidation of the nitrogen oxide are removed by an alkaline reducing wash. The reducing additive, which preferably consists of thiosulfate, prevents the NO _{2 from} disproportionating and thereby releasing NO, which would run counter to the purpose of NO removal. In addition, this addition increases the rate of absorption of the NO ₂ in the washing liquor.

In the case of the low-temperature decomposition of the coke oven gas, the NO is before the one to be carried out anyway Lye washing is oxidized by electrical discharges or the addition of ozone and the washing lye, preferably alkali, the corresponding thiosulfate in a concentration of preferably about n / 20 added.

In the case of the oxidation of NO in long-distance gas, soda solution mixed with thiosulphate is preferably used as the scrubbing agent. The soda solution changes into bicarbonate solution during washing, which has _{equilibrated with the CO 2 of} the long-distance gas and consequently no CO _{2 when the gas is further passed through}

809 617/447

absorbs more, but NO ₂ , whose decomposition with H ₂ O to NO is prevented by thiosulfate.

Gases treated in this way can be used in a cryogenic separation plant without the risk of explosions are fed.

Claims (1)

Claim: Process for removing nitrogen oxide from gas mixtures, such as coke oven gas, remote gas or the like., where the nitrogen oxide initially through the action of silent electrical discharges, ozone or the like., and the reaction products, such as nitrogen dioxide, nitrosates, etc., then can be removed by washing with an alkaline aqueous solution, characterized in that that as a detergent for the reaction products, an alkaline solution of a reducing Agent is used. Considered publications:
German Patent Nos. 875 849, 851107, 798, 520793, 521031, 712449;
German interpretative document No. 1 085 640. 809 617/447 9.68 © Bundesdruckerei Berlin