Choice of structural materials for equipment and pipelines of a vacuum crystallization unit for potassium chloride production

The article is devoted to choice of structural material for equipping a projected vacuum crystallization unit (VCU) for salt crystallization with intense solution concentration. Results of studies show that the low corrosion resistance of steel 12Kh18N10T, 10Kh17N13M3T, 08Kh22N6T, 08Kh21N6M2T, and alloy 06KhN28MDT specimens in vapor phases and solutions under operating conditions for the projected VCU do not permit their application for manufacturing equipment and pipelines operating in contact with weakly acid saturated potassium chloride solutions and vapor phases of these solutions boiling under vacuum. Under the operating conditions for the projected VCU titanium is the sole metallic material that has in a broad metallurgical range high production and mechanical properties, and corrosion resistance, which makes it possible to provide a standard service life both for individual assemblies and a VCU as a whole. Successful experience of using titanium as the main structural material for evaporation unit equipment in the Slavyansk and Mozyr Salt Extraction Combines, Uralkalii, the Ufalei Nickel Combine, and a number of other producers for over 35 years demonstrates the high reliability of using titanium for manufacturing equipment of a projected VCU, processing corrosive weakly-acid saturated potassium, manganese, and sodium chloride solutions, containing a solid phase in the form of salt crystals. In order to manufacture vessels for a projected VCU, operating at atmospheric pressure, it is possible to use nonmetallic materials or carbon steel with coating. The greatest chemical resistance, according to results of research in saturated chloride solutions with a solid phase as applied to equipment and pipeline operating conditions for a projected VCU, applies to a Dion 9400 coating produced by the companies Reichold and Asplit Dupont.