3 Critical Barriers for UAN Quality – Which One Is the Weakest Link?

UAN production must strictly comply with the agricultural industry standard NY/T 2670-2020 Urea Ammonium Nitrate Solution and Application Procedures. The standard specifies that the total nitrogen content shall be ≥32.0%, with amide nitrogen ≥16.0%, nitrate nitrogen 7.2–8.4%, and ammonium nitrogen 15.6–17.7% (note: the ratio range for amide nitrogen is repeated in the source text; the key is the total N ≥32.0%), and a pH range of 5.5–7.5.

The core of production lies in precisely mixing urea solution and ammonium nitrate solution in the correct proportions. This process requires:

• Precise control of raw material flow rates—Even minor deviations in the mix ratio can lead to product crystallization or failure to meet quality specifications.
• Strict control of process parameters—especially pH and temperature. The final product pH is adjusted to the target range by adding Dilute Nitric Acid, while impurities and by products such as biuret must be effectively removed and controlled.
• On line real time monitoring—Modern UAN plants are commonly equipped with on line refractometers or sonic velocity measurement systems that continuously monitor concentration, allowing deviations to be detected and corrected immediately without waiting for laboratory results.

Before finished product enters the storage tank, key indicators such as refractive index are also checked to ensure every batch meets quality standards before leaving the plant.

Transportation is a critical point where UAN quality is most susceptible to external factors. The focus is on preventing contamination or degradation of UAN during transfer.

• Cleaning and inspection of transport equipment—Prior to loading, tank cars (rail or road) must undergo rigorous cleanliness and suitability checks, ensuring the inner surface is clean and all fasteners and seals are intact.
• [Critical] Cleaning and certification of transport vehicles—If the vehicle has previously carried other products, the tank must be thoroughly cleaned by a qualified professional cleaning service before loading UAN. After cleaning, the service provider shall issue a cleaning certificate to the customer. Carriers should choose cleaning facilities that meet the required standards, and shippers may also specify cleaning clauses in transport agreements or contracts.
• Supervision during loading/unloading and sampling—Loading must be supervised by trained personnel, and samples should be taken according to established procedures for laboratory analysis.
• Key indicator testing—Prior to and after transport, critical parameters such as total nitrogen content, nitrogen form ratios, crystallization temperature, pH, and density must be tested to confirm that quality has not been compromised.

Storage tanks are the final line of defense for UAN quality control—and corrosion is the greatest enemy. UAN solutions are highly corrosive to ordinary carbon steel. Without proper treatment, they can cause damage to tanks, pipelines, rail cars, and application equipment, resulting in discoloration, sludge deposition, and even pitting perforation.

• Use of corrosion resistant materials—Tanks should be constructed of corrosion resistant materials such as polyethylene or fiberglass reinforced plastic (FRP). If carbon steel tanks are used, specially formulated corrosion inhibitors (e.g., monoAmmonium Phosphate) must be added.
• [Critical] Cleaning and certification of tanks and pipelines—Before first use, or when switching stored product types, the tanks and associated pipelines must be thoroughly cleaned by a qualified professional firm. After cleaning, acceptance inspection shall be carried out, and the tank operator shall provide a cleaning certificate to confirm that the facilities are clean, safe, and compliant with UAN storage requirements.
• Temperature management—Storage temperature should be maintained within the recommended range of 10°C to 47°C. Excessive temperature accelerates corrosion, while too low a temperature may lead to crystallization.
• Regular cleaning—Tanks should be drained and thoroughly cleaned at least every two years to remove surface corrosion sludge and prevent the more serious "under deposit pitting". Residual small amounts of UAN solution (“heel”) must not be allowed to remain in the tank for extended periods.
• No mixing—It is absolutely forbidden to mix UAN solutions containing different corrosion inhibitors, as this may render the inhibitors ineffective and dramatically increase corrosion risk.