DEGRADATION OF POTASSIUM FERROCYANIDE USED AS AN ANTI-CAKING AGENT

Abstract

The relevance. Improving the quality of potash fertilizers supplied abroad, the indicators of which include the value of caking, is an urgent problem. As an anticaking agent for potassium chloride, potassium ferrocyanide can be used, which has a significant drawback, which is that during the storage of the KCl product in the warehouse during the day, degradation and decrease in the content of potassium ferrocyanide by 20 % are observed, which subsequently during transportation by sea or rail transport leads to product caking and consumer complaints. Analysis of the causes of degradation showed that hydrolysis of ferrocyanides can occur in aqueous solutions. The aim of the research is to determine the reasons for degradation and decrease in potassium ferrocyanide content on the surface of the crystals of the potassium chloride product. Methods. To establish the degradation of potassium ferrocyanide aqueous solution, a theoretical analysis of the literature data on the mechanism of potassium ferrocyanide decomposition, methods of thermodynamic, synchronous thermal, chemical analysis and electron microscopy were used. Results. By theoretical analysis and experimentally, it has been established that the chemical degradation of potassium ferrocyanide occurs mainly during thermal treatment of aqueous solution of an anticaking agent with the formation of a precipitate of iron hydroxide and hydrocyanic acid. Since the anticaking agent solution is sprayed on the hot KCl product under industrial conditions, experiments were carried out in which solutions of potassium ferrocyanide with different concentrations were applied to potassium chloride and subjected to heat treatment. It was found that with an increase in processing temperature of the KCl product from 60 to 120 °C, the degradation of the anti-caking agent increases, and the residual content of potassium ferrocyanide in the product decreases. With the increase in the heat treatment temperature and the concentration of potassium ferrocyanide in the anti-caking agent solution, its losses on potassium chloride increase. At the same time, the increased temperature of the hot potassium chloride product coming from the drying apparatus accelerates the drying of the anti-caking agent solution, which worsens its distribution on the surface of the KCl product crystals.

Keywords

• potassium chloride
• anti-caking agent
• potassium ferrocyanide
• aqueous solution
• degradation