Analysis and experiment of feeding material process of Hermetia illucens L. frass bucket wheel based on DEM

Abstract

• The parameters of bucket wheel operating for Hermetia illucens sand are analyzed. • EDEM is used during the study of bucket wheel shoveling process. • Computer simulation is used in the analysis of the bucket wheel shoveling and unloading Hermetia illucens sand. • The optimal operation parameters affecting the bucket wheel working performance are obtained through the DOE. This study aims to improve the load factor and reduce the residual rate of the Hermetia illucens L. feeding bucket. Based on the sand bucket feeding conveyor designed in the early stage, the technological characteristics of biotransformation of pig manure with Hermetia illucens L., and the mechanism of the bucket shape feeding and transport, the 4-day-old Hermetia illucens L. larvae was firstly inoculated in the pig manure environment with a water content of 75% at 26℃. Then, the single factor experiment was conducted to compare the effect of pig-manure bulking thickness on the biotransformation efficiency of Hermetia illucens L. The results demonstrated that when the thickness of pig manure was 0.10–0.15 m, the biotransformation efficiency of Hermetia illucens L. was relatively high, and the weight loss rate of pig manure was more than 50%. Hence, the thickness of pig manure was an essential factor influencing the efficiency of bucket feeding transportation. On this basis, the physical parameters such as shape size, particle size distribution, and water content of the Hermetia illucens L. sand particles after biotransformation of pig manure were determined. Furthermore, the discrete element method was adopted to establish the numerical simulation model of the bucket shape feeding conveyer under the combination of discrete element simulation and bench test, so as to simulate the bucket shape feeding transport process with insect sands after cleaning the Hermetia illucens L. larva as the test object. Meanwhile, a mechanics and kinematics analysis was conducted for the stress of the horizontal and vertical directions, the mass of materials in the bucket, and the leakage area of the bucket to reveal the mechanism of feeding filling conveying and leakage bucket. Additionally, the main factors influencing the bucket material feeding transport efficiency were comprehensively determined, including feed speed, bucket rotating speed, and feeding depth. The test indicators such as bucket load factor, variation coefficient, and residual rate were established. Besides, a three-factor three-level orthogonal combination experiment was conducted by combining with the Box-Behnken test method. Then, the regression mathematical model between the indexes and factors was set up to analyze the influence law of various factors on the evaluation indicators. The parameters were optimized with the regression model. The model validation test results suggested that the bucket rotating speed was 6.5r·min-1 when the feed speed was 45 mm·s −1 ; the experimental values of the load factor, variation coefficient, and residual rate were consistent with the theoretical optimization values when the feeding depth was 15 cm, with the relative errors of 2.14%, 5.84%, and 6.40%, respectively. Thus, the model optimization is reliable. Under the condition of the optimization parameters, the bench test equipment was established, and the experiment was performed. With the mixture of Hermetia illucens L. insect sand as the experimental material, its load factor, variation coefficient, sand retention rate, and larvae loss rate were 81.23%, 1.48%, 1.85%, and 3.75%, respectively, which met the experimental and actual production requirements. The research results provided a theoretical reference for the design and optimization of the bucket shape feeding conveying machinery of Hermetia illucens L. insect sand.