Cement Americas

FAL 2018

Cement Americas provides comprehensive coverage of the North and South American cement markets from raw material extraction to delivery and tranportation to end user.

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Page 44 of 51

www.cementamericas.com • Fall 2018 • CEMENT AMERICAS 43 FEATURE Considering the Vortex Layer The Promising Application of Vortex Layer Devices with Ferromagnetic Elements for Cement Improvement. By Frank May C ement is one of the most widely used construction mate- rials. Every year, both production and consumption of cement increase. Cement quality defines the quality of con- crete and durability of concrete structures. Some of the cement particles, 70 micron and larger, are not fully engaged in hydration and not hydrated in the concrete. There are estimates that as much as 20 to 40 percent of cement take no part in solidifying and formation of a con- crete structure. Efficiency of cement is also reduced in long-term storage, when particles gather into larger lumps. The materials is hydrated by atmospheric moisture: cement may lose up to 20 percent of its efficiency after only three months of storage, and up to 40 percent after one year in the warehouse. Increased consumption of cement can be avoided by grinding the cement again, which increases the mean surface area of the grains, accelerates hydration and improves strength. Equipment Used For Cement Grinding There are three types of equipment that can perform fine and superfine cement grinding: •  Impact-action equipment (jet mills, hammer mills, cen- trifugal mills, etc). •  Grinding-action equipment (roller mills, bead mills, over- runner mills, ring mills, pan mills, etc). •  Combined impact and grinding equipment (ball mills, vibration mills, bead mills, attritors, planetary mills, col- loid mills, etc). In theory, all of the above can be used to pulverize construc- tion materials, but not all can change their chemical activity by mechanical means. Besides, industrial mills consume a lot of electric power and are often very noisy. For instance, activation of cement by vibration mills may require as much 90 kWh/ton power, while a centrifugal mill may consume 78 kWh/ton. One promising type of equipment for pulverization and activation of cement are magnetic mills with a vortex layer of ferromagnetic particles. These units feature comparatively low power consumption, small sizes and are easily retrofitted into existing production lines, improving their efficiency by subjecting the processed media to several factors and intensifying all processes. How the Vortex Layer Device Operates In simple terms, the vortex layer device (Figure 1) is simi- lar to an induction motor without the rotor. Instead of the rotor, there is the active chamber 4, made of non-magnetic material. The chamber contains cylindrical ferromagnetic particles (5), in the amount anywhere from several dozen to s eve ra l h u n d re d , d e p e n d i n g o n c h a m b e r vo l u m e . When the induction coil (2) is energized, it generates a rotating electromagnetic field, which interacts with the ferromagnetic particles, driving them on complex trajectories. The particles collide with one another and the chamber walls, forming the vortex layer. Figure 1 – Ferromagnetic particles vortex layer unit: 1) protective collar; 2) rotating EM field induction coil; 3) induction coil case; 4) non-magnetic active chamber; 5) ferromagnetic particles.

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