Optimization of rice straw disassembly process parameters and fiber self-interweaving structure

Rice straw is an important renewable resource. Under the circumstance of global resource shortage and energy shortage, it is of great significance to vigorously develop comprehensive utilization of straw. It is not only an important way to realize agricultural circular economy and low-carbon economy, but also involves sustainable development issues such as soil fertility, environmental security and efficient utilization of renewable resources in the entire agricultural ecosystem. Straw fiber ecological blanket has a good function of air permeability and water permeability, and has a significant positive effect on the ecological protection of soil surface microenvironment. Mechanical kneading is the key technology for the dismantling and optimization of agricultural waste straw fiber. In this study, the optimal process input is the spindle speed, hammer tooth clearance and material water content, and the output is the straw silk rate and calibrated unit productivity. An intelligent model was developed using Box-Behnken response surface method (RSM) to determine the functional relationship between input and output parameters. The three evaluation index models all have high reliability, and the determination coefficients are R² > 0.95 and R² > 0.84, respectively. The variance analysis of RSM regression model clarified that the influence of various factors on straw silk ratio was in the order of spindle speed > water content > hammer tooth clearance, and the linear relationship between spindle speed and straw silk ratio was increasing. The significant influence on the calibrated unit power productivity of the kneading machine is in the order of hammer tooth clearance > spindle speed > moisture content. When the hammer tooth clearance is constant, it decreases first and then increases with the spindle speed and straw moisture content. The results of factor interaction analysis showed that when the water content of straw was 40%, the spindle speed was 2 500 r/min, and the hammer tooth clearance was 13 mm, the silk ratio of rice straw was 96.75%. When the straw moisture content is 60%, the spindle speed is 2 300 r/min, and the hammer tooth clearance is 11.08 mm, the maximum calibrated unit power productivity is 29.96 kg/(kW·h). Mathematical model process parameters optimization: straw moisture content is 41.2%, spindle speed is 2498 r/min, hammer tooth clearance is 12.84 mm. Under the combination of these parameters, the rice straw silk ratio is 96.93%, and the calibrated unit power productivity is 29.33 kg/(kW·h). Under optimized conditions, the proportion of fibers with length of 40-70 mm and > 70 mm showed an increasing trend, especially the fiber with length of > 70 mm increased by 120.55%. The proportion of fiber length-to-width ratio > 50-80 and > 80 increased from 17.39% and 6.52% to 38.64% and 16.01%, respectively. Ultra depth of field microscopy showed that the self-interweaving formability of kneaded straw fiber was significantly improved. The optimized mechanical kneading cost of straw fiber can be reduced by 27.50 yuan/t. The mechanical kneading technology strategy of the RSM model developed in this paper is effective for improving the decomposition rate of biomass straw and reducing the consumption of biomass straw, and can be widely used in the production of high-value agricultural products based on large fiber bundles of straw. The mechanical kneading technique strategy of the RSM model developed in this paper is effective for improving the decomposing silk rate and reducing the consumption of biomass straw, and can be widely used in the production of large-size fiber bundle straw based high-value agricultural products.