Inorganic Chemicals Industry ›› 2025, Vol. 57 ›› Issue (2): 92-97.doi: 10.19964/j.issn.1006-4990.2024-0188

• Research & Development • Previous Articles     Next Articles

Determination of potassium salt solubility at low temperature and study of liquid fertilizer formula

DONG Nan1(), WANG Nan1, JI Lijun1(), SHENG Yong2   

  1. 1.East China of Science and Technology,Shanghai 200237,China
    2.Sinochem Yunlong Co. Ltd. ,Kunming 655204,China
  • Received:2024-03-29 Online:2025-02-10 Published:2025-02-20
  • Contact: JI Lijun E-mail:13013063723@163.com;jilijun@ecust.edu.cn

Abstract:

The crystallization of potassium salts in high-potassium-content liquid fertilizer at relatively low temperature is closely related to the solubility of potassium salt.In this study,the liquid-solid equilibrium data of KH2PO4-KNO3-H2O at the low temperature of 278.15 K and 288.15 K,and that of KH2PO4-KCl-H2O at 278.15 K were measured using the isothermal dissolution equilibrium method,and the data was plotted in the phase diagrams with specified crystallization regimes.The results showed that the two systems were simple co-saturated and no double salt or solid solution forms.In two systems,the solubility of potassium salts was increased with the increase of temperature,and according to phase diagrams the K2O content of co-saturated point was maximum at 278.15 K and 288.15 K.Based on the content requirement of macro-nutrition,highlighted in the NY 1106—2010 standard,the formula of the high-potassium-content liquid fertilizer was analyzed,using the solid-liquid equilibrium data.The results showed that,it was often difficult at the ambient temperature regions,and was not viable at the low temperature regions to meet the required NPK content by only using KH2PO4 and KNO3.The formulas of the liquid fertilizer were designed by adding liquid ammonium polyphosphate(APP) to increase NPK content,the results were validated by experiment.This study could provide reference for the formula design of liquid fertilizer in potassium salt system at low temperature.

Key words: liquid-solid phase equilibrium, liquid fertilizer, formula, potassium dihydrogen phosphate, potassium nitrate

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