Results of the reduction system
Two powder coatings with different particle size distributions, already ground, were available for the tests. Both powder coatings were whites with a titanium dioxide content of approximately 60%. Fig. 3 shows the particle size distributions of the feed material.
To investigate the influence of the dust load on the process, the mass flow of the ground powder coating and the feed volume flow were varied at process temperatures of 35 °C and 5 °C, respectively. Tests with dust loading of between 155 g/m³ - 1009 g/m³ were performed. Fig. 4 shows the TiO2 fine dust content of the treated powder coating end product. On the primary ordinate, the dust load in gpowder coat/m³ air is plotted as columns, and on the secondary ordinate the TiO2 fine dust content in the powder coating end product is shown as a graph in percent. The aim is to achieve a TiO2 fine dust content of less than 1%.
From the results presented, it is clear that the final content of TiO2 fine dust depends on both the dust load and the process temperature. The higher the dust loading of the product stream, the lower the TiO2 fine dust content in the powder coating final product. At a process temperature of 35 °C, the TiO2 fine dust content is approximately 43% lower with a dust load of 1009 g/m³ than with a dust load of 155 g/m³.
The temperature also has a great influence on the TiO2 reduction process. At a process temperature of 35 °C, the maximum limit of 1% of the TiO2 fine dust content in the powder coating end product is not reached. In contrast, at the process temperature of 5 °C, the TiO2 fine dust content in product A is between 0.6% and 0.99% with a dust load of 329 g/m³ to 1009 g/m³. For product B, the limit of 1% TiO2 fine dust content is also met at a process temperature of 5 °C with dust loads between 416 g/m³ and 878 g/m³.