Enhancing the efficiency of Brown 24 pigment production through continuous microwave heating in conveyor belt and rotary kiln systems: A design and optimization study

In energy intensive industries, the continuous production with microwave technology presents several challenges in achieving high energy efficiency and heating uniformity. In the ceramic pigments sector, the Brown 24 is the ideal candidate for this study due to its susceptibility to thermal runaways and its high temperature to reach total conversion, higher than 1000K. By another hand, most literature related to this field focus on static systems while ignoring the continuous ones which are required by the industry. A coupled model that integrates thermal, electromagnetic and chemical phenomena within an energy system was implemented in COMSOL Multiphysics. Additionally, a MATLAB controller was employed to dynamically adjust the cavity length through a moving plunger, which maximizes the electrical efficiency. The required power is also managed to guarantee a total chemical conversion of the material. The proposed optimization methodology reduces computational costs, and it is applicable to any continuous microwave system processing moving solid materials. In this work, two microwave configurations were optimized. The first one, based on a conveyor belt, achieved a global efficiency close to 70%. While the second one, based on a rotary kiln, achieved a global efficiency of 85% and a production rate of 4.66kg/h, significantly outperforming a previous study by factors of 1.57 and 2.06, respectively. These findings show the potential for substantial improvements in continuous microwave systems.