Quality Control of Liquids and Suspensions

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The analysis and quality control of solid fertilizers has been extensively studied. In contrast, liquid and suspension fertilizers have often been assumed to be less prone to quality control issues due to their relatively homogeneous nature. However, control officials' reports indicate that such assumptions are unfounded. This publication investigates the impurities in raw materials, particularly phosphate sources, used in fluid fertilizer production and highlights their contribution to quality control challenges. The study draws upon research conducted by the Tennessee Valley Authority (TVA), revealing the presence of insoluble compounds derived from impurities in phosphate rock and wet-process phosphoric acid production in raw materials used for fluid fertilizer production. A profound understanding of the fundamental principles underlying liquid and suspension fertilizers is crucial to establish an effective quality control program. The publication clarifies the significance of a solubility curve representing the relative solubility of ammonium phosphates during fertilization. Furthermore, it emphasizes the importance of selecting appropriate potash grades for suspensions, considering criteria such as size specifications and impurity content. The publication also provides insights into preparing carriers for suspensions, focusing on the commonly used attapulgite clay as a suspending agent. It highlights the necessity of properly shearing and gelling the clay to prevent settling and crystal growth in suspensions. The recommended shearing process involves multiple passes through a centrifugal pump, ensuring optimal orientation of clay particles. Additionally, the publication explores the electrical charge characteristics of attapulgite clay, which contribute to its ability to prevent solids from settling. Sampling techniques for fluid fertilizers are addressed to ensure accurate chemical analysis. Proper sampling procedures are outlined, including the importance of recirculating the fertilizer through the pump to obtain representative samples. The publication suggests determining the optimal recirculation time experimentally or with assistance from control officials, ensuring reliable and consistent sampling.
Suspensions, Quality control