# Experimental Research into the Efficiency of an Electromagnetic Mill
## 1 Introduction  
In the face of climate change, one of the key design aspects is related to the development of energy-saving technologies, as they form an important stage in achieving sustainable development and have a positive effect on the human environment. Therefore, scientific research and research and development in this area form a necessity. The areas taken into account in such processes should include adequate planning of production processes, minimization of material losses, as well as the introduction of innovative technologies that can offer effective and economical use of natural resources. The application of a magnetic field for the purposes of activating substances offers an enhancement in various processes in technology and leads to increasing energy efficiency of these processes. Scientific research carried out in this area demonstrates that minimal energy losses can be achieved as a result of the design of devices that include the conversion of the energy of an electromagnetic field directly into kinetic energy of ferromagnetic bodies. This method of energy conversion is applied, for example, in devices that use methods of communication of materials by application of millstones in their working chambers (WC). Electromagnetic mills (EMMs) are a good example of such devices. Nowadays, in spite of their potential, EMMs are not yet applied on a mass scale. They perform their function by utilizing a rotating magnetic field and moving ferromagnetic bodies (millstones) in the WC of the mill which ensures low energy losses. Mechanical interaction between those bodies and the milled substance (WS) results in grinding and mixing of the substances [1; 2; 3; 4]. Currently, EMMs are applied not only for grinding and mixing solids, but also for emulsifying liquids and mixing gases, obtaining aerosols and increasing chemical activity of solid particles through their grinding in impact or abrasive mode. We can also note certain advantages of EMMs when they are compared to the traditional mill mode, especially in terms of better efficiency, greater accuracy and flexibility in controlling the grinding process [5; 6]. The analysis of experimental research into EMMs revealed a few problems previously discussed in publications, in particular:  
* Establishing the impact of different external factors on the distribution of WS particles depending on the size and finding optimal conditions for achieving the preferred granulometric composition of the ground substance [7; 8; 9];
* Comparison of wet and dry grinding in an EMM with different grinding process parameters, such as grinding time, WS volume, WS particle size, thickness of the suspension, etc. [10; 11]. * Comparison of efficiency indicators of an EMM and a traditional ball mill, taking into consideration the fractions of the obtained ground substance [12]. The particle size in grinding result samples is measured using a laser diffraction method or by digital image recognition systems [13]. The authors of [7; 10; 11] introduce indicators showcasing the efficiency of the grinding process. Research has also been conducted to design EMMs using specific efficiency indicators. The technological process structure and the control system have been developed, which allow for automation of the grinding process and the classification of the end product on the basis of various criteria [11; 14]. Specialized mathematical models for calculation of an optimal ratio of the air transport streams of working substance, which are constantly delivered to the WC in order to obtain desired ground product particle distribution for their size, are also processed [5]. Another area of EMM research is related to its thermal state [15; 16]. The authors of [17] present a method of analysis of EMM thermal processes, which uses the thermal equivalent (TEC) of the active area of an EMM. The latest research also focuses on the use of EMMs in increasing the rate of mechanochemical reactions in solids [1; 2; 18].