Production of industrial ammonia from ammonium carbide solution

Ammonium carbide solution is decomposed, and then reabsorbed to form industrial ammonia water.

Thank you. Could you be more specific?

This job isn’t very easy. I wonder how experts do it. But here’s a suggestion. First of all, it should be understood that both ammonia and carbon dioxide are volatile, with carbon dioxide having a higher degree of volatility. The basicity of ammonia is stronger than the acidity of carbon dioxide. Therefore, the pH value of an aqueous ammonium carbonate solution is around 9.0 (it depends on concentration and temperature), and the solution contains components such as H+, OH-, CO2, NH3, NH4+, H2CO3, HCO3-, CO32-, NH2COO-, and NH2COOH. Therefore, the mathematical model describing the ammonia-carbon dioxide aqueous solution is very complex. Therefore, if one wants to separate carbon dioxide from ammonia water, it is first necessary to know their respective concentrations. If the concentration of ammonia is much higher than that of carbon dioxide, a simple distillation column can produce pure ammonia water at the top, while at the bottom an mixture of ammonium carbonate and a small amount of ammonia water is obtained. It is unlikely that the concentration of carbon dioxide in an aqueous solution could be much higher than that of ammonia, as the partial pressure of carbon dioxide is too high. If the molar ratio of ammonia to carbon dioxide in the feed solution is below 3:1, it is recommended to first distill to obtain a highly concentrated solution at the top of the tower, while clean water is obtained at the bottom. The concentrated solution at the top of the tower is mixed with ethanolamine solution (ammonia has a pKa of 9.25, while ethanolamine has a pKa of 9.50; it is more basic and its boiling point is above 180 degrees). Further distillation can yield high-purity ammonia water. The absorbed carbon dioxide can be removed through conventional high-temperature (reduced-pressure) distillation, and the ethanolamine aqueous solution can be reused. Alkalis and non-volatiles using monoethanolamine (MEA) are not sufficient; therefore, diethanolamine (DEA), dipropylenediamine, or alkaline amino acids (synthetically produced) would work better.

Of course, membrane separation can also be used. First, the feed liquid is distilled, and at the top of the tower a mixture of high-concentration ammonia and carbon dioxide is obtained. Heated again to a gaseous state, ammonia and water vapor pass through a silicone rubber membrane, with a selectivity for carbon dioxide of around 3. Not too high.

Could it be something simple? Is it okay to add lime milk? I tried adding lime milk at room temperature, but there was no reaction at all; its specific gravity also didn’t change. Logically, carbon dioxide should react with lime milk. If anyone knows why this is the case, please let me know. Is it simply not feasible? My chemistry skills are too poor; I’m hoping experts will come and help