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残膜干法制粒装置设计与试验

Design and experiment of residual film dry granulation device

  • 摘要: 针对残膜水洗熔融制粒装置能耗高、用水量大和易造成微塑料污染,难以在西北干旱和半干旱农业区普及应用的问题,该研究基于现有水洗熔融制粒装置的技术特点,结合干法清杂后的残膜物料特性,设计了一种残膜干法制粒装置。通过理论分析和试验相结合的方法,对筒体、动刀和定刀等关键部件进行结构参数设计。通过对残膜粒化的主要过程进行运动学和力学分析,确定了影响残膜干法制粒装置作业性能的关键因素及其取值范围。利用仿真软件分别对喂料和搅粒过程进行数值模拟,对残膜干法制粒装置结构设计的合理性进行验证。为验证残膜干法制粒装置的作业性能,以动刀转速、定刀楔角、搅拌叶片上端长度为试验因素,残膜喂入率和粒化率为评价指标。设计单因素试验缩小各试验因素的取值范围,获得各个因素的较优取值范围。利用响应曲面试验得到试验因素与评价指标的响应面回归模型,通过多元回归拟合分析得出最优参数组合:动刀转速754.5 r/min,定刀楔角39.57°,搅拌叶片上端长度97.2 mm,残膜喂入率为92.77%,残膜粒化率为95.56%。样机试验表明:动刀转速755 r/min,定刀楔角40°,搅拌叶片上端长度97 mm时,平均残膜喂入率、粒化率分别为91.71%、94.16%,与理论预测值分别相差1.14和1.46个百分点。研究结果可为新疆等地区解决残膜堆存问题提供参考,对国内干旱和半干旱农业区的残膜污染治理具有积极作用。

     

    Abstract: Residual film can be recycled by the water-washing and melt granulation equipment in modern agriculture. However, three challenges have severely restricted its application in the arid and semi-arid agricultural regions of Northwest China, such as the high energy consumption, substantial water requirements, and a significant tendency to generate microplastic pollution. Particularly, the water resources are scarce in the sustainable environment, such as Xinjiang. In this research, a dry granulation device was specifically developed to process the residual film after dry cleaning. Existing water-based systems were also incorporated to effectively treat the dry-cleaned residual film, according to the unique material properties. Theoretical analysis was also integrated with the experimental validation. A systematic optimization was performed on the structural parameters using engineering calculations and iterations. Key components were then optimized, including the granulation barrel, rotating moving blade assembly, and stationary fixed blade system. The influencing factors on the equipment performance were also identified using kinematic and mechanical analysis of the granulation. Their operational ranges were precisely determined using advanced analytical and experimental data. Numerical simulations were conducted to verify the structural and functional performance. Experimental verification was performed on the film feeding dynamics and the particle mixing behavior under various conditions. Three parameters were taken as the test factors: rotational speed of the moving blade, wedge angle of the fixed blade, and the length of the upper end of the stirring blade. The residual film feeding rate and granulation efficiency were selected as the primary evaluation indicators to assess the performance. A single-factor test was carried out to determine the preliminary parameter ranges. The testing efficiency was optimized to reduce the overall experimental costs. Subsequently, the response surface method (RSM) was also implemented to explore the relationships between the parameters and performance indicators. Accurate regression models were obtained after multivariate regression and optimization. The optimal combination of the parameters was determined to be: the rotating blade speed of 754.5 r/min, fixed blade wedge angle of 39.57°, and upper stirring blade length of 97.2 mm. The remarkable performance was then achieved with a film feeding rate of 92.77% and a granulation rate of 95.56%, indicating the excellent processing. Prototype tests were also conducted with the parameters of 755 r/min blade speed, 40° wedge angle, and 97 mm stirring blade length, in order to accommodate the manufacturing tolerances during operation. The results demonstrated that there was outstanding performance with the average feeding and granulation rates of 91.71% and 94.16%, respectively. The minimal deviations of only 1.06 and 1.40 percentage points from the theoretical predictions indicate the high accuracy and reliability of the improved models. Consequently, the dry granulation effectively eliminated the water consumption and energy requirements, thus providing a practical and efficient technical solution to the residual film accumulation in Northwestern regions. Secondary microplastic pollution was also prevented in the conventional water-based systems. A sustainable and environmentally responsible approach was offered to manage the agricultural plastic wastes under the water-sensitive environments, in order to promote the advanced agricultural practices in dryland farming regions. Sustainable waste management can greatly contribute to the circular economy in agricultural production.

     

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