CS243601B1 - Process for preparing ammonium nitrite solution - Google Patents

Abstract

The solution relates to a method for preparing an ammonium nitrite solution on an industrial scale, namely by absorption in an absorption solution containing ammonium nitrite, ammonium bicarbonate, ammonium nitrate and ammonium carbonate. Absorption is carried out at a temperature of 0 to 20 °C at the point of initial contact of nitrous gases with the absorption solution and the composition of the absorption solution is maintained in the range of 150 to 300 g/l ammonium nitrite, 1 to 50 g/l ammonium bicarbonate, 1 to 30 g/l ammonium nitrate and up to 40 g/l ammonium carbonate, while the temperature of the nitrous gases entering the point of initial contact is maintained in the range of 10 to 180 °C.

Description

(54) Method for preparing ammonium nitrite solution

The solution relates to a method for preparing an ammonium nitrite solution on an industrial scale, namely by absorption in an absorption solution containing ammonium nitrite, ammonium bicarbonate, ammonium nitrate and ammonium carbonate. Absorption is carried out at a temperature of 0 to 20 °C at the point of initial contact of nitrous gases with the absorption solution and the composition of the absorption solution is maintained in the range of 150 to 300 g/l ammonium nitrite, 1 to 50 g/l ammonium bicarbonate, 1 to 30 g/l ammonium nitrate and up to 40 g/l ammonium carbonate, while the temperature of the nitrous gases entering the point of initial contact is maintained in the range of 10 to 180 °C.

The invention relates to a method for preparing an ammonium nitrite solution.

Ammonium nitrite, an important intermediate in the production of hydroxylamine sulfate by the Rasohig method, is prepared almost exclusively by the absorption of nitrous gases in a solution of ammonium carbonate (NH^JjCOj and ammonium bicarbonate NH4HCO3. The following reactions take place in the synthesis of ammonium nitrite NH^NOj:

NO + NO ₂ + HjO = 2 HNO ₂ (1)

_{( NH4} ) _2CO3 + _{2HNO2 = NH4NO2} + _CO2 + _H2O (2) _{NH4HCO3 + HN02} = _{NH4NO2 + CO2} + _H2O (3) ( _NH4 ) _2CO3 + _{2NO2 = NH4NO3 + NH4NO2 + CO2} (4)

The temperature increase during the absorption of nitrous gases in a NH^HCO^ solution is only 1.3 °C (equation 3). However, the temperature increase during the absorption of nitrous gases in a (NH ₄ ) ₂ CO ₃ solution is 23 °C (equation 2). The difference in the heat available in the above reactions clearly shows that equation (3) is more advantageous from the point of view of heat balance, since it places significantly lower demands on the removal of reaction heat and reduces the possibility of undesirable side reactions (4), which are additionally suppressed by reducing the vapor pressure of ammonia above the liquid.

Undesirable side reactions include the formation of ammonium nitrate NH^NO^, the inversion of ammonium nitrite to ammonium nitrate, and the formation of elemental nitrogen by the decomposition reaction of ammonium nitrite and nitrogen oxides with ammonia.

According to data in the literature, up to 87% conversion of nitrous gases to ammonium nitrite can be achieved, which represents about 84% yield of ammonium nitrite - calculated on ammonia entering the preparation of nitrous gases.

The methods of preparing ammonium nitrite used so far consist in the absorption of nitrous gases in a solution of ammonium carbonate and ammonium bicarbonate without a more precisely defined ratio of these components by the Rasohig method. The yields reported in the literature are not achieved by these methods.

The above-mentioned deficiency is eliminated by the method of preparing an ammonium nitrite solution according to the invention, the essence of which lies in the fact that when preparing an ammonium nitrite solution with a concentration of 150 to 300 g/1 from nitrous gases with a concentration of 9 to 13% by volume of nitrogen oxide at a pressure of 0.05 to 0.3 MPa, absorption in an absorption solution containing ammonium nitrite, ammonium bicarbonate, ammonium nitrate and ammonium carbonate, absorption at the point of initial contact of nitrous gases with the absorption solution is carried out at a temperature of 0 to 20 °C and the composition of the absorption solution is maintained in the range of 150 to 300 g/1 ammonium nitrite, 1 to 50 g/1 ammonium bicarbonate, 1 to 30 g/1 ammonium nitrate and up to 40 g/1 ammonium carbonate, while the temperature of the nitrous gases entering the point of initial contact is maintained in the range of 10 to 180 °C. The yield of absorption of nitrous gases then increases with decreasing ammonium carbonate content in this sample and, after its elimination, with decreasing ammonium bicarbonate concentration down to the level of 1 g/1.

The advantage of the method for preparing ammonium nitrite solution according to the present invention lies in the increase in yield above the limit of 80% and a yield of over 84% has already been achieved (under operating conditions). Another advantage is the significantly lower thermal coloration of the reaction, thereby reducing energy consumption requirements. The ammonium nitrite solution prepared in this way ensures, by its composition, higher yields in the production of hydroxylamine sulfate, if used.

Examples

Nitrogen oxides obtained by oxidation of ammonia with the help of a catalyst are fed into a packed production column. In the column, they react with an absorption liquid, which is an aqueous solution of nitrite, nitrate, bicarbonate and ammonium carbonate. The absorption of nitrous gases and the released carbon dioxide is completed in scrubbing towers. The scrubbing solution, which contains nitrite, nitrate, hydroxide, ammonium carbonate, flows through the scrubbing towers against the direction of gas flow and is supersaturated with ammonia and carbon dioxide.

The composition of the absorption medium, which is in initial contact with nitrous gases (total monthly balance), is also given.

examples

concentration in g/1 1 2 3 4 5 6 - ammonium nitrite 198 229.1 230.2 230 229.8 230.2 - ammonium nitrate 32.4 22.8 16.8 20.1 18.2 16.8 - ammonium carbonate 27.9 17.4 14.2 29.4 18.8 14.2 - ammonium bicarbonate 32.5 36.5 34.8 35.1 35 34.8 temperature in °C - templates 5 8 10 10 10 10 - nitrous gases 40 82 88 84 84 84 yield (%) 73.93 82.64 84.8 76.3 81.1 84.1 The yield was determined from the material balance sheet and determines % conversion of ammonia entering to oxide·

ammonium nitrite.

Claims (1)

SUBJECT OF THE INVENTION A process for the preparation of a solution of 150 to 300 g / l ammonium nitrite from 9 to 13 S nitrous gases at a pressure of 0.05 to 0.3 MPa by absorption in an absorption solution containing ammonium nitrite, ammonium bicarbonate, ammonium nitrate and carbonate ammonium, characterized in that the absorption at the point of initial contact of the nitrous gases with the absorption solution is carried out at a temperature of 0 to 20 ° C and the composition of the absorption solution is maintained between 150 and 300 g / l ammonium nitrite, 1 to 50 g ammonium bicarbonate; up to 30 g / l of ammonium nitrate and up to 40 g / l of ammonium carbonate, maintaining the temperature of the nitrous gases entering the point of initial contact between 10 and 180 ° C.