DE1118169B - Process for the degassing and oxidation of nitrogen oxide and water containing nitric acid - Google Patents

Description

GERMAN

PATENT OFFICE

INTERNAT.KL. C Ol b

S63893IVa / 12i

REGISTRATION DATE: JULY 13, 1959

NOTICE THE REGISTRATION ANDOUTPUTE EDITORIAL: NOVEMBER 30, 1961

The invention relates to a method for degassing and oxidizing a nitrogen oxide and water containing Nitric acid to increase the concentration of nitric acid by treating the Mixture with oxygen or gases containing oxygen.

Processes of this type are known. They all suffer from the deficiency that degassing and oxidation contribute must be carried out significantly above atmospheric pressure. In many cases the oxidation is also separated from the degassing in an uneconomical manner.

In contrast, the method according to the invention which avoids these deficiencies is characterized in that that degassing and oxidation at atmospheric or only slightly above pressure together be carried out in a column equipped with random packings or trays that the nitrogen oxide and water-containing nitric acid applied cold at the top, the flow of oxygen passed from the bottom to the top and heat is indirectly supplied to the reactants approximately in the middle of the column.

In addition, nitrogen oxides are preferably introduced in liquid or gaseous form approximately into the middle of the column.

The figure shows a system for carrying out the method according to the invention.

In the upper and lower part of the column 1 shown in the figure there are packing elements or Floors. The nitrogen oxide and water-containing nitric acid mixture to be oxidized and degassed is at 8 the Column fed and trickles from top to bottom through the column. The bottom is over a side Approach 4 of the column is supplied with oxygen, which flows from the bottom up through the column. In the middle area the column, the mixture is temporarily withdrawn, passed through a heating coil 6 and then reintroduced into the column, where it trickles onto the lower part of the packing or the trays. At the concentrated acid is drawn off from the lowest point 2 of the column; from the top 10 the column exits the exhaust gases. Nitrogen oxides can be liquid or gaseous through the connection 16 be initiated.

For example, at 8 a mixture consisting of 46 percent by weight HNO ₃ , 31 percent by weight H ₈ O _3, 23 percent by weight N ₂ O ₄ + N ₂ O ₃ or, in other words, consisting of 77 percent by weight of a 60% acid and 23 percent by weight N ₂ O ₄ HN ₂ O ₃ , continuously applied at a temperature between 0 and -10 ° C., and oxygen is continuously ^{blown in at 4 in an amount of about 0.5 m 3} / kg of nitrogen oxides added. Those from the above procedure for degassing and oxidation

one containing nitrogen oxide and water

nitric acid

Applicant:

South German calcium cyanamide works

Corporation,

Trostberg (Obb.)

Dipl.-Ing. Thomas Fischer, Trostberg (Obb.),
has been named as the inventor

Acid flowing off part of the column is heated to about 60 to 70 ° C. in the heating coil 6 before it is returned to the upper part of the lower column. _{An acid with a concentration of 69% HNO 3} , which is practically free from nitrogen oxides, is then obtained at the lowest point 2 of the column.

Depending on the concentration to be achieved and especially when working without overpressure, it has turned out to be shown advantageous, in addition nitrogen oxides in liquefied or in gaseous form about in the middle of the Initiate column, i.e. where the heat is also supplied. Contrary to previous practice, according to which, when working under pressure, the oxidation proceeds best when one is in that of liquid filled space works, it has been found that when working without excess pressure or at a slight excess pressure the nitrogen oxides react faster in gaseous form than in the dissolved form. In this version According to the invention, there is a maximum possible reaction between nitrogen oxide gases, acid and oxygen Required because, on the one hand, unreacted gases escape from the cold acid trickling down upwards difficult and on the other hand, by the degassing effect, entrainment of nitrogen oxides through the acid leaving the column is prevented.

This combination of oxidation and degassing carried out in this way has the great advantage, especially with acids of over 68%, that a maximum acid concentration can be obtained with a certain _{nitrogen oxide-HNO 3} -water mixture.

109 747/506

Claims (2)

PATENT CLAIMS: 1. A method for degassing and oxidizing a nitrogen oxide and water-containing nitric acid to increase the concentration of nitric acid by treating the mixture with oxygen or oxygen-containing gases, characterized in that degassing and oxidation at atmospheric or only slightly above pressure together in one with packing or trays equipped column are carried out so that the nitrogen oxide and water-containing nitric acid is abandoned cold at the top, the oxygen stream is passed from the bottom to the top and heat is indirectly supplied to the reactants approximately in the middle of the column. 2. The method according to claim 1, characterized in that in addition liquid or nitrogen oxides be introduced in gaseous form approximately in the middle of the column. Considered publications:
U.S. Patent No. 2,046,162;
Chem. Zentralblatt, 19371, 2842. For this purpose, 1 sheet of drawings © 109 747/506 11.61