DE1251900B - Process for removing nitrogen compounds from gases - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

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German class: 26 d- 9/01

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1251900
K49240IVc / 26d
March 20, 1963
October 12, 1967

COUNTRIES

The present invention relates to a method for removing nitrogen compounds (hydrocyanic acid, Nitrogen oxide) from gases by means of a washing process.

There are numerous technical gases, e.g. B. synthesis gas, water gas, generator gas, coal distillation gas and the like, which in addition to the desired components also contain nitrogen compounds as impurities, especially hydrogen cyanide and nitrogen oxide. These nitrogen compounds tend to work along with other ingredients of the gas, especially together with unsaturated hydrocarbons, for gum formation, whereby the compression of such gases is made very difficult, often even impossible. Further the gum formation ensures the proper functioning of the measuring devices installed in the gas pipes and control devices impaired.

Efforts so far made to remove nitrogen compounds from gases, though technically successful by and large, but not satisfactory because of one thing in comparison large amount of detergent (mostly alkalized water) or equipment (electrical tuft field; Radiation lamps) an increase in the price of the cleaned one that does not correspond to the limited success Gas enters.

The invention has set itself the task of removing the nitrogen compounds from gases with To carry out the help of a washing process in which not only a practically complete cleaning of the Gases in terms of these impurities is achieved, but also the purification because of the avoidance of undesired side reactions takes place under highly economical conditions.

The inventive method for removing nitrogen compounds (hydrocyanic acid, nitrogen oxide) from gases by washing the gas at essentially normal temperature, whereby the nitrogen compounds are absorbed in the washing solution and then desorbed again, for. B. by venting and / or heating the washing solution, which is then used again in the circuit, is characterized in that ß as a washing solution an aqueous solution of a chelate compound , which is a ScTiwerme tallion from the IV . Period of the Periodic System of each element that contains "is.""""' ^{Tir111 T} ""*" *

Chelate complexes (see Römpp "Chemie-Lexikon", 5th edition, 1962) are generally understood to mean an organic body with a more or less complex composition, which contains one or more metal ions, which range from several to five to methods for removing
Nitrogen compounds from gases

Applicant:

Heinrich Koppers

Company with limited liability,

Essen, Moltkestr. 29

Named as inventor:
Ortwin Gogolin, Munich

ao six-membered rings are enclosed like scissors or pliers, the ones in these rings Oxygen, nitrogen or sulfur atoms each have electrons to the one they enclose Release metal ion. The resulting

The bond between the metal ion and the mentioned oxygen, nitrogen or sulfur atoms of the rings is called a coordination bond, in contrast to the usual valence bond.
The chelate complex compounds with the above-mentioned general characteristics are extremely diverse and differ from one another, depending on the type and number of rings and the coordinatively bound metal ion, by their physical and chemical properties.

The investigations have shown that chelate complex compounds are used for leaching the nitrogen compounds The carboxylic acid groups in the complex-forming anion, if appropriate, are advantageous their alkali or alkaline earth salts, including in particular those chelate complexes, in which aminocarboxylic acids or their salts are present.

A well-known in analytical chemistry representative of this chelate containing amino carboxylic acids, goes from the Äthylendiaminotetra acid (EDTA ^ respectively. Alkali metal or alkaline earth * salt "Aeus. Put? One of Äthylendiami notetraess igsä acid sen_ example, the tetrasodium salt with egg ( III) -sulf af um, so bildefsi'cn'eih 'CneTatKbmplex, in

what a baer partially through several iron ions real valence bonds and additionally bound by coordinative bonds. The watery one

709677/335

Solution of the EDTA iron (lll) chelate is deep red, the of the EDTA iron (lI) chelate colored yellow.

Other representatives of this class include: Hydroxyäthyldiaminoäthylenetriacetic acid, Diethylenetriaminepentaacetic acid, ethylenediaminedi (O-hydroxyphenyl) acetic acid, Diaminoethyl ether tetraacetic acid, ethylene glycol - bis (aminoethyl ether) - tetra acetic acid, l ^ -diaminocyclohexanetetraacetic acid, uramildiacetic acid, Hydroxyäthylnitrilodiacetic acid, anilinediacetic acid and their mono-, di- or polybasic alkali or Alkaline earth salts and other aminocarboxylic salts.

In addition to the carboxylic acids and aminocarboxylic acids already mentioned, other organic Groups, especially nitrogen-containing complexes, used as chelate complex-forming anions will.

Examples include: ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylene pentamine and higher polyethylene amines; also 1,2-diamines, such as propylenediamine and dipropylenetriamine etc., and 1,2-, 3,4-tetramines such as butadiene tetramines etc.

For the selection of the most appropriate »chelate complex for a specific application, nor the point of view essential that the main components of the gas to be purified, such as Hydrogen, carbon dioxide, carbon dioxide, aromatics, saturated and unsaturated aliphatics, etc., none exert a detrimental effect on the stability of the chelate complex. It was in this context found that chelate complexes with high water solubility, especially those with at least two carboxylic acid groups per complex, from the main components of the usual technical Gases are practically not influenced.

The washing solution expediently has a pH value between 6 and 8. More alkaline solutions however, can often achieve better results.

The easiest way to regenerate the washing solution is to use aeration. The ventilation causes at the same time reoxidation of the chelate complex and expulsion of nitrogen compounds. The nitric oxide is in this case, if the washing solution by any circumstances in a reduced form is present, partly reduced to nitrogen, optionally reduced to ammonia. The hydrocyanic acid is in the general not changed. So hydrogen cyanide escapes with the ventilation air. A warming of the Washing solution at temperatures below 100 ° C is also sufficient for regeneration in most cases.

example

A desulfurized coke oven gas contained 60 g hydrogen cyanide per 100 Nm ³ . The gas was washed at a temperature of 25 ° C. with an aqueous solution of Fe ₂ (III) Na ₀ (EDTA) ₃ in an amount of 1.5 m ^{8 of} solution per 1000 Nm ^{3 of} gas. The concentration of the solution was 0.2 mol of chelate complex per liter. After washing, the hydrogen cyanide content of the gas was still about 1 g per 100 Nm ³ . The degree of leaching was accordingly 98.5%.

In another case, a residual gas from a chemical process was treated, the hydrogen cyanide content of which was 330 g per 100 Nm ³ . The washing took place under otherwise identical conditions. A degree of leaching of 77.9% could be achieved.

Contained a largely purified coke oven gas

Nitrogen oxide in an amount of] 2 cubic centimeters per Nm ³ gas. Among those already described above

Under certain conditions, the gas is scrubbed with chelate solution. The nitrogen content of the gas decreased to about 0.6 cubic centimeters per Nm ^{s of} gas. The degree of leaching was accordingly about 95%.

If the chelate solution was reduced by the simultaneous presence of hydrogen sulfide, so the degree of leaching of nitrogen oxide increased to 98 to 99%.

Claims (2)

Patent claims: 1. Process for removing nitrogen compounds (hydrocyanic acid, nitrogen oxide) from gases by scrubbing the gas at substantially normal temperature, thereby removing the nitrogen compounds absorbed in the washing solution and then desorbed again, e.g. B. by venting and / or heating the washing solution, which is then used again in the cycle, characterized in that an aqueous solution of a washing solution Chelate complex compound that is a heavy metal ion from the IV period of the Periodic Table containing elements is used. 2. The method according to claim 1, characterized in that in particular such chelate complex compounds are used that contain carboxylic acids or aminocarboxylic acids in the complex-forming anion. Considered publications:
French patent specification No. 1302767.