Conditions for the formation of ammonium carbonate (ammonium bicarbonate)

The pure substance is obtained by passing ammonia and carbon dioxide into water and then cooling it to induce crystallization. Industrial products are obtained by reacting sulfuric acid an or ammonium chloride with calcium carbonate. Production method of ammonium bicarbonate: Concentrated ammonia water comes into countercurrent contact with carbon dioxide in the secondary tower of the carbonation tower to produce carbonated ammonia water. This carbonated ammonia water then enters the top of the main tower of the carbonation tower, where it again comes into countercurrent contact with carbon dioxide to form an ammonium bicarbonate slurry, which is subsequently processed to yield ammonium bicarbonate. Ammonium carbonate and ammonium bicarbonate may precipitate during certain production processes; the main factor influencing this is temperature, as (NH4)2CO3 decomposes rapidly at 58°C into ammonia, carbon dioxide, and water. Ammonium bicarbonate decomposes significantly at temperatures above 30°C. The decomposition products of ammonium bicarbonate are ammonia, carbon dioxide, and water. In other words, ammonium bicarbonate can be formed at temperatures below 30 degrees, while ammonium carbonate is formed at temperatures below 58 degrees. Therefore, these two temperature points should be avoided during production to prevent crystallization.

Thank you very much! I would also like to ask you: does the crystallization temperature you mentioned refer to conditions at atmospheric pressure? Could you please help me find out what the crystallization temperature is at 0.42 MPa?