Engineering & Mining Journal

MAY 2019

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36 E&MJ • MAY 2019 www.e-mj.com One of the world's top 10 fertilizer pro- ducers, the Russian company EuroChem, is increasing its production capacity for phosphate rock-based fertilizer products with the development of mining and pri- mary ore treatment for the Kok-Djon de- posit in southern Kazakhstan. The project is being developed in two stages. During the first stage, production facilities for crushing, drying and grinding of phosphate rock, mined in the nearby open pit, came on stream in 2016. The product will serve as the raw material for a new chemical processing and fer- tilizer-production plant that will be built during the second stage. Upon com- pletion, the complex will produce about 3.2 million metric tons per year (mt/y) of first-class high-grade mineral fertilizer and associated products for local and in- ternational markets, making it the biggest fertilizer producer in Kazakhstan. Difficult environmental conditions, as well as various process and product related requirements, have turned the processing of the material into a complex task that can be solved very efficiently by vertical roller mill (VRM) technology. With more than 2,500 installations worldwide, Loesche GmbH is a leader in designing and supplying mineral processing plants with VRM technology. The company's core competence is the development and implementation of crushing, grinding and drying plants with a high level of process engineering. It has frequently been the first company to introduce its technolo- gy in various industries, including several installations for grinding phosphate rock and phosphate rock concentrates. After being approached by EuroChem to develop a dry comminution process based on VRM technology, Loesche per- formed extensive test work at its research center and won the contract. Since completion of the commis- sioning in February 2016, the 650,000- mt/y phosphate rock grinding plant, en- gineered, delivered and assembled by Loesche, operates to EuroChem's com- plete satisfaction. As the project combined demanding requirements with a relatively hard and abrasive material, it was an ex- cellent opportunity to introduce a number of modifications to the VRM technology for pro- cessing hard ores and minerals that Loesche has developed in re- cent years. Loesche's Technology VRMs are usually op- erated in closed circuit with a dynamic classi- fier mounted above the grinding table. The work- ing principle requires a constant flow of process gas through the housing, with the application of hot gases allowing com- bined grinding, drying and classification (See Figure 1). After an obligatory tramp metal remov- al, the material to be ground is fed to the mill and led into the center of the grind- ing table (1). Driven by centrifugal force, the material moves outward to the edge of the rotating table. On its way, the material is drawn into the grinding gap between grinding table and hydro-pneumatically spring-loaded grinding rollers (2). Under compression in the grinding gap, the ma- terial bed is compacted by shifting the particles into existing gaps before particle breakage starts to prevail. The breakage is induced mainly by compression, sup- ported by small amounts of shear, result- ing in optimum size reduction and min- GRINDING CIRCUITS GRINDING CIRCUITS By Markus Stapelmann, Dr. Carsten Gerold and Alexey Smirnov dry product in a difficult environment Major fertilizer producer uses vertical roller mill to produce a consistent, Phosphate Ore Dry Comminution of Hard-rock EuroChem, a Russian fertilizer producer, uses Loesche's VRM technology at its phosphate rock processing complex near Zhanatas, Kazakhstan. Figure 1—Sectional drawing of a Loesche VRM with dynamic classifier.

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