Method of Industrial Automated Optical-Electronic Control of Granulometric Composition of Mineral Fertilizers

The article describes the solution of the operational control problem of particle size composition of industrially produced mineral fertilizers by the optical-electronic method. The device and algorithm for automated online control in industrial conditions is proposed. This scheme consists of three independent parts: the system of sampling from the conveyor belt, the system of sampling in the field of analysis (feeder) and the block of optical-electronic detection of granules. The peculiarities of the proposed scheme include online control of the fraction of granules (granulometric composition, which was calibrated by mass or optical distribution) and several abilities (to analyze the shape and color of granules; to work in industrial conditions and to transfer data into the factory information system - "PISystem"). Sampling from the conveyor belt is carried out by a robotic rotary system. The transfer of the sample to the analysis area was performed by the linear vibrations of the sample feed system. The integrated computer controls the entire sampling and feeding scheme. Furthermore, the algorithm for calculating parameters of granules was developed. It consists of obtaining an optical-electronic image (three-dimensional Red-Green-Blue matrix of pixel intensities), image pre-processing (smoothing, binaryization and morphology), calculation of closed contours, approximation of the found contours by ellipses and calculation of ellipse parameters (long and short axis, axis ratios, average color). All stages of receiving and processing of the information are automated and implemented on programming language Python 3.7. Statistical indicators of the proposed method are calculated and the results are compared with the laboratory techniques of granulometric composition analyses. The linear correlation map of different parameters of technological process (calculated granulometric composition, raw material consumption, work of drum dryer-granulator, vibrating screen and crushers) is given.