On-line measurement of average pellet size with spatial frequency analysis

The authors report a novel method of online measurement of pellet size with an image processing technique. The moment of the power spectrum of the pellet image is proposed as a new index of pellet size. Experimental results clearly indicate that this new index corresponds to the real size of the pellet. This method has several advantages: the average size of pellets accumulated in a pile is measured; the index has good correspondence to human senses; and the index covers a wide measurement range. This method was applied to the pelletizing system in the ferroalloy works at NKK Corporation and made automated operation of the pelletizer possible