Concentration Measurement of Urea Ammonium Nitrate

In the worlds largest and most modern nitrogen production facility in Luisiana, United States, three major nitrogen fertilizers - ammonia, urea and nitrogen solutions - are produced in world-scale quantities.

One of the principal products in the nitrogen fertilizer production is Urea Ammonium Nitrate solution (UAN).

The concentration of the UAN solution needs to be maintained at precisely 32% in order for the end product to have the right properties. To obtain this concentration measurement, a conventional in-line critical angle refractometer had been employed for some time. These readings were backed up by periodic product sample tests conducted in the plant’s laboratory.

One of the problems Quality Control had to deal with was the refractometer’s drift: UAN tends to deposit a film on the refractometer’s prism so much that it had to be cleaned daily. Various self-cleaning methods had been tried without success.

The newly installed PIOX R transit light refractometer provides a true drift free measurement. Instead of being reflected or refracted on a prism surface, the light beam is refracted only after having travelled through the entire liquid sample. Coating of the prism can be tolerated and drift and maintenance issues are avoided. Furthermore, the accuracy compared to the critical angle method is improved by a factor of 10. After a test lasting several months, the plant gave FLEXIM its stamp of approval for the instrument – saving maintenance costs and helping to avoid reject batches.  

Advantages:

• Continuous process control
• Precise measurement with transit light refractometry
• True drift free performance
• Higher precision and better control of end product quality
• Avoidance of waste batches
• Cost savings by elimination of instrument maintenance