Energies 2022, 15, 899. https://doi.org/10.3390/en15030899 www.mdpi.com/journal/energies Article Numerical Study of the Erosion Process and Transport of Pulverized Coal–Air Mixture in the Mill‐Duct System Bartłomiej Hernik Department of Power Engineering and Turbomachinery, Silesian University of Technology, Konarskiego 18, 44‐100 Gliwice, Poland; bartlomiej.hernik@polsl.pl; Tel.: +48‐32‐237‐1196 Abstract: One of the main causes of damage to the elements of coal‐fired boilers installations, lead‐ ing to breakdowns and, consequently, a shutdown of the block, are erosive processes. Unfortu‐ nately, there is not much research conducted on dust erosion of the dust ducts supplying the air– dust mixture to the burners. The problem of erosion of the dust ducts supplying the pulverized coal–air mixture to the burners was presented in this paper. This study was performed for the pre‐ liminary feasibility design. The destruction of the material of the dust ducts results in a failure due to erosion, resulting in the mill being shut down from an operation, which in turn may lead to the shutdown of the power plant unit. Therefore, it is important to identify places exposed to pulverized coal erosion. In order to perform calculations, numerical modeling in the commercial program An‐ sys.Fluent (Ansys Fluent, Computational Fluid Dynamics, Ansys Inc., Pittsburgh, PA, USA) was used. The parameters obtained as a result of laboratory tests were used in the erosion model. The places where erosion is expected are indicated. The highest erosive wear occurred for the M3 mill dust ducts for the case coal 1 and amounted to 45.6 mm/5200 h. On the other hand, the lowest erosive wear occurred for the M2 mill dust ducts powered by coal 3 and amounted to 20.9 mm/5200 h. The identification of places where erosion is expected can be used to protect these places from erosion adequately. Nevertheless, a dispersion threshold should also be placed where there is a high con‐ centration of pulverized coal contributing to increased erosion. The numerical calculations provided information on the velocity of the medium and the behavior of the dust in the dust duct. The nu‐ merical calculations also provided information on where dust lacing has occurred. It was shown that coal dust particles with a diameter greater than 100 μm largely erode the dust duct’s wall. A model is presented for the calculation of the erosion process to be used in the dust ducts of the power plant. Keywords: erosion; pulverized coal; mill‐duct system; failure 1. Introduction One of the main causes of damage of the elements of coal‐fired power boilers instal‐ lations leading to breakdowns, and consequently to the shutdown of the unit, are erosive processes. Erosion occurs mainly in dust ducts feeding the pulverized coal–air mixture to the burners as well as in the second pass of the boiler on the surfaces of convection bundle tubes. The erosion process is associated with the presence in the continuous phase of par‐ ticles with a diameter exceeding 25 μm [1]. The erosion rate increases with the exponent of the particle velocity (usually equal to the velocity of the continuous phase) [1–7]. A comparison of this exponent determined experimentally by various researchers is pro‐ vided in [1,5]. It varies from 2.4 to 3.5 for metal and about 3 for ceramics to 5 for polymers. The exponent of velocity also depends on other parameters, such as particle size and the shape of eroding particles. The value of the velocity exponent also depends on the angle of impact—for steel values lower than 2 (1.4–1.6) at perpendicular inflow [6]. However, the value of the exponent depends on the method of determining the amount of solid Citation: Hernik, B. Numerical Study of the Erosion Process and Transport of Pulverized Coal–Air Mixture in the Mill‐Duct System. Energies 2022, 15, 899. https://doi.org/10.3390/en15030899 Academic Editors: Simone Salvadori, Paweł Ocłoń and Piotr Cisek Received: 29 November 2021 Accepted: 21 January 2022 Published: 26 January 2022 Publisher’s Note: MDPI stays neu‐ tral with regard to jurisdictional claims in published maps and institu‐ tional affiliations. Copyright: © 2022 by the authors. Li‐ censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con‐ ditions of the Creative Commons At‐ tribution (CC BY) license (https://cre‐ ativecommons.org/licenses/by/4.0/).