Determination of SOT of Liquid Fertilizers

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1 Determination of SOT of Liquid Fertilizers AAPFCO Winter Annual Savannah, GA Feb 2017 Dr. Michael Hojjatie R&D Director, TKI

2 Market share, % USA fertilizer market share by class y = x x R² = *Excludes dir. appl. anhydrous ammonia Data source: Commercial Fertilizers, AAPFCO & TFI Dry 61.5% Fluid 31.0%* Ammonia 7.5%

3 Liquid Fertilizers Fertilizer Grade Triazone N Fertilizer Ammonium Thiosulfate S CAN Ca Calcium Nitrate Liquid UAN Ammonium Polyphosphate and Potassium Thiosulfate S 3

4 Liquid Fertilizers Easier to prepare Easier to apply Applies easily to the irrigation lines Can be blended with other nutrients in one application Furthers 4R Crop Nutrition Disadvantage - May salt out in cold temperatures 4

5 Crystallization Temperature: The crystallization temperature is the temperature at which a solid phase begins to form, resulting in a mixture of solid particles and solution. These solids may be salt crystals or water crystals (ice). Figure 1 shows a typical crystallization temperature curve for a Salt solution. Note that the left side of the curve slopes downward with increasing salt concentration levels. This side of the curve is labeled Solution + Ice Crystals. It represents the freezing point of the salt, where ice crystals would begin to form. The right side of the curve is labeled Solution + Salt Crystals. It represents the phase boundary of the salt, below which salt crystals begin to form. The minimum point where the two curves intersect is known as the eutectic point. It is the point at which the minimum crystallization temperature can be realized. In essence, it is the lowest temperature at which a solid free solution can exist. 5

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7 7 Typical Crystallization curve FCTA = First Crystal to Appear TCT = True Crystallization Temperature (the formation of salt crystals generates a small amount of heat, which causes a slight rise in the solution s temperature) LCTD = Last Crystal to Dissolve

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9 9 Fertilizer Solutions Salt-out is an issue in many environments and SOT should be known Warm water has ability to dissolve more salts than cold water Salt-out occurs when salt content exceeds solubility at a given product temperature Crystals form on tank walls as temperature cools Eventually salts accumulate at tank bottom Salts will re-dissolve with sufficient heat and recirculation in most cases.

10 SOT Measurement Methods There are multiple methods used to measure SOT which makes product comparissons difficult Lack of consistency among methods and no standards: 1. Dauncy & Still Optical Method, J. F. Luternauer, J. Agri. Food Chem. 1967, 15(3), Polythermal/Thawing Method, Kadam, et.al., Chem. Engineering Science, 1970, Vol 2, 2012, ASTM D97 4. UAN (Different per industry) 10

11 A few Current SOT Methods No Universal Method Available 11

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13 KOCH METHOD 13

14 ASTM METHODS ASTM D6660 Determination of freezing point of aq. Ethylene glycol base engine coolants by atomic phase transition method. ASTM D Determination of freezing point of aqueous engine coolants. 14

15 ASTM D97 POUR POINT ASTM D97 Pour Point 15

16 CF-UAN (B. WHITE PROVIDED) 16

17 2. Poly thermal Method (TVA) SOT Measurement Methods 17

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19 Salt Out Temperatures (SOT)-Examples We have tried SOT of a commonly used blend of ATS & UAN, namely S with two different in house methods: SOT of Ammonium Thiosulfate is 42º F SOT of UAN 32 is reported to be 32º F Grade is popular Accurate SOT measurement in critical 19

20 Source 1 Source 2 Source3 ph Comparison of Testing Methods 20º F %N %ATS %SO %Alkalinity as NH 4 OH SOT ºC Polythermal Method 8.4 ( 47.1 o F) 7.3 ( 45 o F) 6.5 (43.7 o F) SOT ºC cooling/thawing 6 (42.8 o F) 7 (44.6 o F) 5 (41 o F) (UAN 32) gm ATS gm UAN gm Water (DI) SOT ºC Polythermal Method ( o F) -33 (-27.4 o F) -32 (-25.5 o F) SOT ºC cooling/thawing (2.3 o F) (7.7 o F) -15 (5 o F) (UAN 28) gm ATS gm UAN gm Water (DI) SOT ºC Polythermal Method -33 (-27.4 o F) ( o F) -32 (-25.5 o F) SOT ºC Cooling/thawing -17 (1.4 o F) -13 (8.6 o F) -16 (3.2 o F) 20

21 SOT Measurement Methods 1. Cooling/Thawing Method 21

22 SOT MEASUREMENTS OF FLUID FERTILIZERS 22

23 SOT MEASUREMENT METHOD NEEDS FOR UNIVERSAL/HARMONIZED METHOD? 23

24 PROPSAL: SALT OUT TEMPERATURE (SOT) DEFINITION The temperature of a liquid fertilizer at which the salt content of the liquid exceeds its solubility. At this temperature, a solid phase begins to form, resulting in a mixture of solid particles and solution. The preferred test for SOT determination is by cooling/thawing method. 24