CS243945B1 - The method of capturing ammonia from the offgas - Google Patents

Abstract

The invention relates to chemistry. It provides a method for capturing ammonia from exhaust gases, whereby the ammonia is absorbed in a suspension or in an aqueous solution of phenoxyacetic acids. Ammonia reacts with phenoxyacetic acids to form the ammonium salt of phenoxyacetic acids. Phenoxyacetic acids contain 50 to 100% by weight of 2-methyl-4-chlorophenoxyacetic acid. The process can advantageously be carried out continuously in an absorption column. The absorption solution obtained is used to dilute ammonium salts of phenoxyacetic acids (Dikotex 40). The invention finds application primarily in the production of ammonium salts of phenoxyacetic acids, which are used as herbicides in agriculture.

Description

The invention relates to chemistry.

It solves the method of capturing ammonia from off-gases, whereby ammonia is absorbed in the suspension or in an aqueous solution of phenoxyacetic acids.

Ammonia with phenoxyacetic acids reacts to form ammonium salts of phenoxyacetic acids. Phenoxyacetic acids contain 50 to 100 wt. 2-methyl-4-chlorophenoxyacetic acid. It is preferred to carry out the process continuously on an absorption column. The absorption solution obtained is used to dilute the ammonium salts of phenoxyacetic acids (Dikotex 40).

The invention finds particular application in the production of ammonium salts of phenoxyacetic acids which are used as herbicides in agriculture. 243945 3 243945

The present invention provides a method for recovering ammonia from gases which are used in the manufacture of products where they are used as raw materials.

Often, in the production or processing of ammonia, degasses are produced which contain ammonia and cannot be discharged into the air in terms of economy and the environment. At higher concentrations, ammonia is absorbed from the gases to form ammonia water at varying concentrations of ammonia. Of the diluted gases, ammonia is most commonly absorbed, with the subsequent chemical reaction of ammonia and absorbent being frequently used. As an example, we can capture the off-gas from coke production where the flue gases are trapped in sulfuric acid, with ammonium sulfate being used as a by-product, which is used as a fertilizer in pornhospoids. Sometimes ammonia gas is trapped in nitrate solutions to form ammonia. An example is ammonium nitrate ammonia, which is used for the production of fertilizers. In the above-mentioned cases, the use of ammonia from the flue gas generates mainly by-products, often with difficulty in disposing of them.

The aforementioned drawbacks are alleviated by the process of capturing ammonia from gases, which is characterized in that it is absorbed in an aqueous solution or suspension of phenoxyacetic acids. Phenoxyacetic acids - a mixture of 2-methyl-4-chlorophenoxyacetic acid, 2-methyl-4,6-dichlorophenoxyacetic acid, 2-methyl-6-chlorophenoxyacetic acid and 2-methylphenoxyacetic acid. Upon absorption, ammonia is reacted with phenoxyacetic acids to form the ammonium salt of phenoxyacetic acids.

Phenoxyacetic acids contain 50 to 100 pounds. wt. 2-methyl-4-chlorophenoxyacetic acid. Preferably, the absorption can be carried out on the absorption column. An advantage of the process of using ammonia from the gases of the invention is that the ammonium salt of the phenoxyacetic acids which can be used as a herbicide is obtained. It is preferred to use the process in a process where the ammonium salt of phenoxyacetic acids is prepared and the absorption solution can be used, for example, to dilute it to a prescribed concentration. Since a chemical reaction takes place during absorption, the absorption from the absorption is practically free of ammonia, and ammonia is used at 100 < 0 >. The absorption does not result in the formation of byproducts. Example 1 Ammonia was absorbed in a 4 cm diameter, 70 cm high absorption column filled with Raschig rings. A suspension of about 1 wt. % of phenoxyacetic acids, of which 57.3 wt. 2-methyl-4-chloro-phenoxy-acetic acid. The flow rate was 0.5 l / min. A gas containing ammonia in the range of 0.1 to 0.35 was fed countercurrently from the bottom of the column. wt. The gas was removed from the top of the column. Absorption continued until the pH of the absorbent solution reached 5.5. The absorption was then stopped and the absorption solution was used to dilute ammonium phenoxyacetate (Dikotex 40). Example 2

The procedure of Example 1 was followed except that after reaching pH 3, phenoxyacetic acids were added to the solution again to give about 0.5 wt. phenoxyacetic acid suspension.

After absorption, the solution was used to adjust the ammonium phenoxyacetate concentration (Dikotex 40). P r i k 1 and d 3

Example 1 was followed except that the phenoxyacetic acids contained 98.6 wt. 2-methyl-4-chlorophenoxyacetic acid. The resulting absorption solution was used to dilute ammonium phenoxyacetate (Dikotex 40). P r i k 1 a d 4

The procedure of Example 1 was followed except that an aqueous solution of phenoxyacetic acids at a concentration of 5.4 g / L was used instead of the slurry. The absorption solution obtained was used to dilute ammonium phenoxyacetate (Dikotex 40).

The invention can be used in the absorption of off-gases from the production of ammonium phenoxyacetate. The advantage is that ammonia is captured from virtually any degassing agent, causing unpleasant odors even in small quantities, thereby improving the environment.

Claims (2)

1. A method for collecting ammonia from off-gases, characterized in that the ammonia is absorbed in an aqueous solution or suspension of a mixture of phenoxyacetic acids containing 2-methylphenoxyacetic acids, 2-methyl-4-chlorophenoxyacetic acids, 2-methyl-4,6- 2-methyl-6-chlorophenoxyacetyl acetate, wherein the phenoxyacetic acids contain 50 to 100 wt. of 2-methyl-4-chlorophenoxyacetic acid. 2. The method according to claim 1, wherein the absorption is carried out continuously on the absorption column.