Study of Equipment Corrosion Resistance in the Production of Potash by a Halurgical Method

Abstract

The problem of equipment corrosion in halurgical production of potash has existed from the time of generation of this industry. In 1927 in a bulletin about the development of the potassium industry in Germany and France Rice and Davis [1] provided data about a requirement for replacing equipment for dissolving ore every three years. Loss due to corrosion (in equipment depreciation) comprised up to one third of the final product's cost. In a handbook [2], there are data about a requirement for performing major overhaul of equipment after each 8460 h of operation with replacement of the main parts of equipment, and this ultimately leads to an increase in potash cost. Thus, the task of improving corrosion resistance of equipment in potash production remains important.The production process for preparing potash by a halurgical method consists of extracting soluble substance from solid material (sylvinite ore) by means of a solvent (mother liquor). The method is based on combined dissolution of potassium chloride (KCl) and sodium chloride (NaCl) in water at different temperatures. During cooling of saturated solution, KCl crystallizes from it.In halurgical production of potash, a three-stage direct leaching scheme is used. Hot leaching of potassium chloride is performed in two stages with recuperation of halite tailings heat in three stages. The equipment operates by a direct flow scheme and is installed successively. Sylvinite ore is charged into the first equipment, within which there is heating to the mother liquor dissolution temperature. After this, the ore is fed into the second equipment for final dissolution by liquor, whose temperature exceeds 100°C. The residue from the second equipment is loaded by an elevator with a screw dissolver, intended for recuperating halite tailings heat.Working media contain chloride salts and solid phase, causing pitting corrosion and corrosive-erosive wear, respectively (Table 1). The high corrosion and erosion activity of working media is strengthened at high temperature.