UAN is a mixture of ammonium nitrate, urea and water. Standard solutions contain 28%, 30% or 32% nitrogen, and may also be enriched with soluble plant nutrients, such as sulfur, boron and calcium compounds. A typical UAN composition with 32% nitrogen would have a 45:35:20 ratio of ammonium nitrate, urea and water. Depending on the specific composition, the salting-out temperature can be well below 0° C so transport and storage are unproblematic, even in cold climates. This property has helped UAN fertilizers to gain significant market shares, especially in North America. With two process alternatives in our portfolio we have designed single-train UAN plants with capacities up to to 4,300 metric tons per day (mtpd).
Ammonium nitrate neutralization
Ammonium nitrate (AN) is produced by the uhde® ammonium nitrate neutralization process. The AN solution is then mixed with urea solution and water in a specially designed UAN mixing unit to obtain the required nitrogen content and then adjusted to an alkaline pH. After cooling and addition of a corrosion inhibitor, the final UAN solution can be easily stored and handled. The contaminant level in the process condensate is normally below 15 ppmw of nitrogen.
Neutralization of urea off-gas
When implementing a once-through urea synthesis, the ammonia-rich off-gas can be used to drive the ammonium nitrate neutralization reaction. As a result of the high CO2 content of the off-gas, the neutralization reaction is performed in a natural circulation loop. This is followed by the UAN preparation steps described above. With a sophisticated scrubbing system installed, ammonia losses in the vent gas can be reduced to 0.013 kg/tAN.
Benefits
Our portfolio covers everything from basic engineering to execution on an EPC lump-sum basis. Customers benefit from our uhde® Technologies through its great reliability and high on-stream time, cost effectiveness, energy efficiency, excellent safety standards, and low emissions, as the wet scrubbing system complies with environment regulations and best available technology levels.