Experiments and parameter optimization of almond shell and kernel air separation device

Abstract: This study aims to explore the aerodynamic characteristics of almond shells, thereby optimizing the structure parameters in an air separation device. The finite element (FE) simulation was also performed on ANSYS 16.0-fluent flow field platform. A single-factor orthogonal test was selected to determine the optimal parameters for better performance of air separation and higher index of cleaning rate. Taking the Shache No.18 as the research object, the density and moisture content of almond shells and kernels were measured in a field test. A suspension speed test bed was used to optimize the aerodynamic characteristics of almond shells and kernels at the Agricultural Mechanization Research Institute of Xinjiang Academy of Agricultural Sciences, China. A field test was also performed on the mixture of cracked shell kernels in an air separation device with an optimized structure. A Design Expert 10.0 software was used to calculate for a better parameter combination of the air separation device. The results showed that there was a great variation in the suspension velocities of a large shell, medium shell, small shell and kernel of Shache 18 almond, ranging from 9.92 to 11.03, 8.86 to 9.66, 8.27 to 8.85, and 13.10 to 13.96 m/s, respectively. The flow field simulation showed that the distribution of air velocity was higher on the vibrating screen surface of the air separation device, particularly in the center and low around. Subsequently, a systematic optimization was made on the feeding and discharging ports of the air separation device after the simulation. The single factor test showed that there was a great influence of feed rate and cleaning fan speed on the loss rate of the material. Additionally, since the loss rate of the material under each factor was within the acceptable range during the test, the orthogonal test did not consider the loss rate so far. Correspondingly, the orthogonal test demonstrated that the influence of working parameters on the cleaning rate was ranked in order from large to small: screen vibration frequency, cleaning fan speed, corrugated screen inclination angle, and feeding amount in the air separation device. Consequently, an optimal parameter combination of high cleaning rate was also calculated as follows: the feeding amount of 6 kg/min, cleaning fan speed of 1 160 r/min, screen vibration frequency of 47 Hz, inclination angle of 3° for the vibrating screen, and the speed of centrifugal fan was 1 275 r/min, particularly combining with the orthogonal test and optimization function of shell kernels in an air separation device. A verification test was then conducted to calculate the average of parameters in the optimal combination under the same test environment and conditions. It was found that the cleaning rate reached 99.144%. The findings can provide sound theoretical support to the development and optimization of air separation equipment for the shell and kernel of almond.