microwave irradiation used for ore benefication
Author: langfeng Time: 2018-08-21
Microwave heating inside a cavity depends on various factors such as a cavity design, dielectric properties of treated material, etc., and for efficient heating the cavity needs to be specially designed for its purpose. Progress in the computer industry (hardware which is much faster and significantly cheaper than 10 years ago) and development of software, which is capable of simulation of the bulk material response to MW heating, gives an opportunity to speed up the process of designing a cavity; computer modelling reduces the need for building expensive model of prototype cavities and experimental testing.
As the dimensions of the cavity increase (which would be the case for the large tonnage throughput capacity needed in MW/IR ore sorting), the cavity supports many modes and the cavity is then called a multimode cavity. By definition a multimode cavity cannot provide total uniform heating. It is important that some qualification about this is achieved for this type of applicator. Non-uniform heating for batch processing multimode cavity is quantified with a smoothness parameter (Georghiou, Ehlers et al. 2006), but in applications such as MW/IR sorting it is desirable to have a parameter that will quantify non-uniform heating for continuous processing cavities. The heating of a particle inside a cavity depends, not only on cavity design, but also, on other particles inside a cavity as indicated in chapter 2; therefore there is a need for better understanding of MW heating in terms of interaction of particles. Regarding that MW heating, in context of MW/IR ore sorting, is used for selective heating so sorting based on their temperature can be done. The non-uniform heating caused by the MW applicator can be considered as a systematic error and it is of interest to separate the effect of the MW applicator from the material response. If this is possible, the correcting of temperature readings at the end of the MW applicator, could take into account non-uniform heating due to the applicator design and particles interaction. This will, particularly, be relevant for the sorting of particles with a moderate amount of MW absorbed minerals.