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Fluid Journal : Winter 2013
15 The Fluid Journal Winter 2013 Michael Orr is President of Specialty Process Consulting, LLC in Pocatello, Idaho, and Dr. Leikam is President of the Fluid Fertilizer Foundation in Manhattan, Kansas. Figure 4. Urea : Ammonium Nitrate Solubility. Figure 5. UAN (32-0 -0) & APP Compatibility Issue, spring 2012. Figure 4. Urea:Ammonium Nitrate Solubility. Figure 5. UAN (32-0-0) & APP Compatibility Issue, spring 2012. Figure 6. UAN : APP : KCL Solubility Diagram. especially in late-winter to early-spring when product temperatures may be very cold: • The first is the use of a hydrometer to check specific gravity (estimates N content) • The second is testing the pH with a properly calibrated pH meter. This important information allows the user to be aware of composition variations in advance so that adjustment can be made when co-mingling with other products. Clogging Figure 5 presents a picture of a tank manway from the spring of 2012 that was opened within a few hours of blending UAN and ammonium polyphosphate. As is seen in the picture, these two products solidified quickly and the resulting precipitates were not flowable enough to be pumped out of the tank. This situation tends to happen most often at the first to mid-part of the planting season when dealers are receiving loads of cold product that are not being mixed with warmer product in storage before being blended for field application. One recommendation is to have enough individual product volumes to be laid into storage prior to the early part of the season to dampen slight pH and specific gravity variations. Familiarize yourself While some variability in the specific formulation of UAN has been around since the initial development of the UAN industry, the increased reliance on imported product has exacerbated this variability and subsequent compatibility issues. It seems to occur more often with unseasoned personnel or when not enough volume is in the storage tanks to minimize ratio variations and/ or free ammonia and product are shipped out immediately. In the past, some manufacturers of UAN have, in fact, had UAN summer blends and UAN winter blends, seasonally altering the ratios of urea to ammonium nitrate. When one thinks about that, the product is relative to the location of the facility involved, whether it is located in a northern climate or a southern one. Take time to familiarize yourself with the product you are receiving. Solubility Another factor affecting UAN-APP compatibility is simply the overall solubility when UAN and APP are directly blended together (no additional water), especially during times of the year when product and air temperatures are cold. While UAN and APP are generally thought of as completely compatible, the solubility of the UAN-APP system is drastically affected by the ratio of UAN to APP in the blend. Figure 6 presents the UAN-APP-KCl solubility diagram developed by the National Fertilizer Development Center (NFDC- TVA) during the early years of the fluid industry. The portion of the graph circled in green (left side of triangular diagram) illustrates that total nutrient solubility (N + P2O5 + K2O) decreases drastically as the proportion of UAN increases in UAN-APP mixes while the potential for precipitation formation increases (forming less soluble ammonium tri- polyphosphates). This problem rarely occurs when 28 percent UAN is used for these mixes rather than 32 percent UAN and occurs more frequently for 11-37-0 APP than for 10-34-0 APP. Previously discussed variations in UAN product analysis, pH and urea:ammonium nitrate ratio makeup further increase the potential for unanticipated compatibility issues. Finally... The information provided herein is not to assign blame or liability. It is simply educational in order that dealers and wholesales better understand the problematic issues that can occur with even the simplest blending of UAN and ammonium polyphosphates.
Early Spring 2013