Design and optimization of a slot antenna for microwave heating of agglomerates.

Purpose The microwave heating technique can be used in the production of iron for productivity improvement when the consumption of low-quality iron ore increases. Iron-containing dust agglomerates are an important source of iron; however, the crushing strength of raw agglomerates is low, which decreases the yield owing to breaking. Therefore, they need to be dried using a “band dryer” to reduce the amount of excess water and improve their crushing strength. This paper aims to present the structure of an antenna that efficiently provides microwave energy to the agglomerate layer inside the band dryer.Design/methodology/approach Electromagnetic field analysis and experiments that simulate inside the band dryer were performed to evaluate the radiation efficiency of the slot antenna for microwave heating of the agglomerate layer in the presence of a metal conveyor.Findings The results show that slot height should be larger than the antenna position from the metal conveyor and smaller than the sum of the antenna position and quarter of the guide wavelength, to maximize the radiation efficiency of the antenna. By satisfying this condition, the radiation efficiency was higher than 75 per cent in the experiments.Originality/value This paper presents for the first time the optimum relation between slot height and antenna position to apply the microwave heating technique to iron-containing agglomerates in a band dryer. [ABSTRACT FROM AUTHOR]