# Development of Electrode of Electric Impulse Chamber for Coal Grinding
## 1 Introduction  
Coal is one of the main energy and fuel resources in the world, which plays an important strategic role in the development of energy and the economy of various countries. The world's largest coal deposits are located in 70 countries, 50 of which are engaged in industrial coal mining [1]. Despite the fact that there are alternative energy sources, they cannot meet the growing human demand for energy. In addition, a large amount of waste has accumulated in the world, which worsens the environmental situation and at the same time has energy value. As a rule, this is waste from coal mining enterprises, oil companies, etc. [1]. In the case of traditional coal combustion, the minerals contained in it are emitted as ash. Ash is removed from boilers or particulate matter-trapping devices. However, some of them are released into the atmosphere as particulate matter. This causes various negative impacts on the environment. Such emissions can be particulate matter, SOx, NOx, greenhouse gases, and toxic metals [2, 3, 4]. To reduce these environmental problems, environmentally friendly use of coal is necessary. As can be seen from the practices, methods of converting coal into liquid fuel are being considered. Coal liquefaction is not a new technology. It has been developed and used since the beginning of the 20 th century. A number of experimental studies show that adding water to the coal combustion process helps to significantly reduce the content of harmful substances and reduce dependence on oil. This contributes to environmental safety, economic benefits, and energy diversification [5]. There are many works which consider the technologies and possible applications of coal-water suspension (CWS), which involves the use of coal-water fuel (CWF) as an alternative fuel source [6]. Coal-water fuel is a product of the transformation of a mixture of finely ground coal and water in proportions. This ensures that the resulting composition remains stable without separation for an extended period [7; 8]. Depending on the conditions for preparing coal-water fuel, its stability can also be ensured by adding a small amount of special stabilizing additives into the composition [9]. The advantages of implementing this technology include: the possibility of transportation via pipeline, minimizing risk of explosions and fires, the possibility of burning various types of coal, a high degree of carbon burnout, a low level of harmful emissions (NOx, SOx, CO), and the possibility of using low-calorie coals from coal preparation to obtain coal-water fuel. Despite the fact that the caloric content of fuel decreases by approximately 3 times when water is added, this processing technology is considered promising due to its high environmental friendliness [10]. For the production the coal powder product used in coal-water fuel (CWF), various methods of coal grinding are used to achieve the required particle size. The main methods are: mechanical, impact, abrasive, hydraulic, ultrasonic, reactive (jet), cryogenic, and electric impulse grinding. The development of technologies for the production of coal-water fuel is a pressing issue, as it contributes to improving the environmental situation and ensuring sustainable energy based on renewable sources. Among modern methods, the electric impulse method stands out as an effective way to obtain coal with high reactivity. Electric impulse grinding (EPG) is a modern technology based on the use of high-voltage electrical discharges to destroy solid materials. The principle of the method is to generate an electric field that causes discharges in the interelectrode space. The discharges create local mechanical stresses. This leads to the destruction of the material along natural cracks and boundaries. The key parameters of the process are the discharge energy, the conductivity of the material, and the design of the electrodes. Optimization of these parameters allows for a significant increase in the efficiency of grinding.