@PhdThesis{duepublico_mods_00047621,
  author = 	{Luczak, Bartholom{\"a}us},
  title = 	{Flow conditions inside spiral jet mills and impact on grinding performance},
  year = 	{2018},
  month = 	{Dec},
  day = 	{10},
  keywords = 	{Milling; Grinding; Comminution; Jet mill; Spiral jet mill; Particle Image Velocimetry; Mahlung; Zerkleinerung; Strahlm{\"u}hle; Spiralstrahlm{\"u}hle},
  abstract = 	{Within the scope of comminution, spiral jet milling is still of great importance and even without alternatives in many fields of application. The number of parameters affecting the grinding process in the spiral jet mill is huge, while the general effects and coherences are most commonly unknown or discussed controversially. Insights about the flow conditions inside spiral jet mills are of particular importance for the exploration of the processes inside the mill, however these insights have a lack of transferability if they are considered individually. In this work, a substantial gain of knowledge of the processes and coherences is achieved due to the fact that the flow conditions inside the grinding chamber are investigated and correlated with corresponding investigations of the grinding performance. Since the purpose-built experimental spiral jet mill apparatus is constructed in an optically accessible way, the particle movement and net air flow inside the mill can be measured via the non-invasive particle image velocimetry (PIV) technique. Additionally, the apparatus is fully operative concerning the grinding ability, which enables the correlation of flow conditions and grinding performance. Further grinding investigations are conducted at an industrial spiral jet mill test facility and industrial spiral jet mill plant, which confirms the determined coherences and proves the practical transferability.
The processes inside the grinding chamber are clearly revealed, resulting in a sharp segmentation in comminution zone and classifying zone via an abrupt loss of velocity and turbulent kinetic energy, with the location being dependent on the mill configuration. However, the comminution is mainly located in the nozzle jets and minorly at the front side of the jets. The velocity at the grinding nozzle jets and consequently the total size of the grinding nozzle jets are attributed as crucial factors of influence regarding the comminution and thus the product particle fineness. The particle velocity near the product outlet tube is characterized as essentially affecting the classifying and thus the width of the product particle size distribution and the mill parameters are investigated towards their influence on this process. All the investigations point out three main options for increasing the energy efficiency in spiral jet milling: i) decreasing the number of grinding nozzles, ii) deploying of Laval type instead of convergent grinding nozzles and iii) increasing the solid feed mass flow rate with simultaneous increase of the total gas mass flow rate. Due to the detailed description and correlation of the flow conditions and the impact on the grinding performance, this work can be considered as a guideline for further spiral jet mill research and development.},
  url = 	{https://duepublico2.uni-due.de/receive/duepublico_mods_00047621},
  file = 	{:https://duepublico2.uni-due.de/servlets/MCRFileNodeServlet/duepublico_derivate_00046719/DissBartholomaeusLuczak.pdf:PDF},
  language = 	{en}
}