| 农业有机废弃物压制绿化基质砖成型机理与试验 |
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| 引用本文： | 刘德军,王家鑫,周艳吉,刘天奇,李宇鸽,孙嘉忆,刘子晖.农业有机废弃物压制绿化基质砖成型机理与试验[J].农业工程学报,2022,38(12):243-252. |
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| 作者姓名： | 刘德军 王家鑫 周艳吉 刘天奇 李宇鸽 孙嘉忆 刘子晖 |
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| 作者单位： | 沈阳农业大学工程学院，沈阳 110866 |
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| 基金项目： | 国家自然科学基金资助项目（No.32171900）；辽宁省农业农村厅关于北方设施蔬菜全程机械化科研基地建设项目（辽农机[2021]202号） |
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| 摘 要： | 为了解决农业有机废弃物污染，促进其综合开发和高值化利用，以发酵腐熟后的水稻秸秆和牲畜粪便为主要原料，利用特制的压缩成型模具和试验机，以基质原料含水率、压缩应力、压缩时间、牛粪质量分数为试验因素，对绿化基质砖压缩成型机理和工艺参数进行了试验研究。通过有限元分析、孔隙通道模型构建等方法，分析了压缩成型过程中力的变化、位移变化和微观结构变化；在单因素试验基础上，利用响应面分析了不同成型条件对绿化基质砖成型质量的影响，获得绿化基质砖成型最优工艺参数：基质原料含水率75.7%，压缩应力0.29 MPa，压缩时间2.5 min，且牛粪质量分数为30%时能够充分获得营养，绿化基质砖成型效果好。该研究为绿化基质砖的生产和农业有机废弃物综合利用及城市绿化产品升级提供了依据。
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| 关 键 词： | 水稻 秸秆 基质 农业有机废弃物 绿化 有限元法 孔隙 牛粪 |
| 收稿时间： | 2021/12/25 0:00:00 |
| 修稿时间： | 2022/4/20 0:00:00 |
Forming mechanism and experiment of greening substrate bricks pressed by using agricultural organic waste |
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| Liu Dejun,Wang Jiaxin,Zhou Yanji,Liu Tianqi,Li Yuge,Sun Jiayi,Liu Zihui.Forming mechanism and experiment of greening substrate bricks pressed by using agricultural organic waste[J].Transactions of the Chinese Society of Agricultural Engineering,2022,38(12):243-252. |
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| Authors: | Liu Dejun Wang Jiaxin Zhou Yanji Liu Tianqi Li Yuge Sun Jiayi Liu Zihui |
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| Institution: | Engineering College, Shenyang Agricultural University, Shenyang 110866, China |
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| Abstract: | Abstract: This study aims to explore the compression forming of greening substrate bricks, covering the raw material preparation, pressing procedure, bricks characterization, finite element method (FEM) simulation, and the parameter optimization. (1) Raw material preparation: The rice straw was crushed by the grinder to mix with the cow dung. The aerobic fermentation was adopted to be completely decomposed the materials. Among them, the premixed materials was hold by hand and molded for reserve. Polyacrylic acid sodium, insecticide and fungicide were mixed to dissolve as the premixed liquid. The premixed materials and liquid were mixed in the proportion for the raw material of greening substrate bricks. (2) Pressing procedure: A pressing process of three-layer composite was utilized to make the greening substrate bricks. Among them, three layers was in the middle, including the upper and lower matrix layer, as well as the greening substrate layer. The greening substrate brick was made and dried below 60°C for the subsequent transportation and storage. (3) Bricks characterization: The physical properties were characterized for the greening substrate bricks after molding and drying. Specifically, the bulk density, the total porosity, and the aeration porosity were 0.62 g/cm3, 63.09%, and 27.78%, respectively. The material properties of greening substrate brick were fully met the needs of plant growth, such as the bulk density and porosity. The physical and chemical indexes were within a reasonable range (pH=7) to balance the nutrition of greening substrate brick. (4) FEM simulation: A three-dimensional numerical model was established, where the materials to be compressed and naturally stacked in the forming mold were selected as the research objects. A systematic investigation was made to determine the variation in the stress along the height during compression and extrusion at different times. The distribution of compression stress was found: the extrusion pressure and friction force, the inner wall of the forming die produced the radial pressure on the material. The material was first extruded from the upper and outer layers to the central layer, and then flowed to the lower layer. (5) Parameter optimization: A pore channel model was constructed to determine the internal pore connectivity and dynamic water migration during compression. A pore channel and a skeleton were included, where the former was a solid matrix bonded and wound by the rice straw and cow dung, while, the pore channel included the channels and blind channels with the divergence and permeability. The compression molding of greening substrate brick was divided into the loose, compaction, pressure maintaining, combined with the pore channel model. It was verified the relationship between the pore coefficient ratio of the model and the porosity of the greening substrate brick after molding with the different holding time, indicating that the holding time posed an important influence on the compression molding. The longer the holding time was, the better the compression molding and molding stability were, particularly with the reduced total porosity. (6) The optimal molding process parameters of greening substrate brick were achieved using the single factor test method. Specifically, the moisture content of materials, compression time, compression stress, and cow dung mass percentage were taken as the experimental factors, whereas, the drying time, water absorption after drying and destructive strength were taken as experimental indexes. An optimal combination was achieved, where the moisture content was 60.4-80.8%, the compression stress was 0.17-0.33 MPa, the compression time was 2-4 min, and the mass percentage of cow dung was 20-40%. A four-element quadratic orthogonal rotation combination test was designed for the variance analysis and response surface analysis using Design-Expert 12.0 and Excel 2016 software. The optimal parameters were as follows: the moisture content of material was 75.7%, the compression stress was 0.29 MPa, the compression time was 2.5min, the mass percentage of cow dung was 31.0%, the drying time of greening substrate brick was 656.9min, the water absorption after drying was 3.9%, and the destructive strength after drying was 11.8 N. The forming and cultivation tests were conducted to verify the optimal parameters. The germination rate of greening substrate brick was maintained at 88%, and the number of repeated water absorption was more than 50 times. The plant grew well and the root system was developed, which met the requirements of normal growth and development of plants. This finding can provide a strong reference for the production of greening substrate bricks, the comprehensive utilization of agricultural organic wastes for the upgrading of urban greening products. |
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| Keywords: | rice straw matrix agricultural organic waste greening finite element method pore cow dung |
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