基于EDEM的分仓立式好氧堆肥反应器设计与试验

    Design and experiments of a vertical aerobic composting reactor based on EDEM

    • 摘要: 针对好氧堆肥周期长、腐熟均一化程度低以及反应器利用效率低等问题,该研究设计了一种单层发酵室有效容积为120 L、3层相互独立的好氧堆肥反应器,可对堆肥过程的各阶段进行控制且缩短堆肥周期,实现连续进出料堆肥。利用ANSYS对搅拌系统校核分析,搅拌轴的最大应力为75.288 MPa,最大变形为3.680 mm,强度符合设计要求;应用EDEM和Fluent仿真分析,结果表明:搅拌轴转速为20 r/min时,反应器下料率为98.14%,反应器曝气时混合物料的气体体积分数均在90%以上,下料及曝气效果良好。采用鸡粪与玉米秸秆1:4(干质量比)混合原料进行堆肥试验,结果表明:对于连续投放的3个批次物料,同一层物料温度差异不显著(P>0.05),且高温期温度高于50 ℃的时间分别为9、7和5 d,达到无害化要求;3个批次物料的pH值均在8.0~9.0之间,电导率均在2.0~3.0 mS/cm之间,各层之间差异显著(P<0.05),各批次物料间差异不显著(P>0.05)。堆肥结束后,种子发芽率均大于100%,挥发性固体降解率分别为14.99%、16.03%和13.24%,各批次堆肥产品性质稳定,反应器堆肥性能良好。该堆肥反应器的设计可为农业废弃物的资源化处理提供支撑。

       

      Abstract: Aerobic composting has been one of the fastest ways to fertilize soil products via organic decomposition under an oxygen-rich environment. Among them, the aerobic composting reactor can be one of the most important facilities during aerobic composting in recent years. However, some challenges are still remained in the aerobic composting reactor, including the long duration, low maturity homogenization, and utilization efficiency. In this study, an optimal vertical reactor of aerobic composting was designed with three independent layers using E-Discrete Element Method (EDEM) and Fluent simulation. An effective volume of 120 L was also obtained in the developed reactor. A series of simulations and experiments was implemented to verify the structural parameters. Each stage was also controlled to shorten the duration of the composting process in this reactor. The continuous process of feeding in and out of feedstocks was established, according to the actual requirement of the reactor during aerobic composting. ANSYS platform was finally used to verify the mixing system of the reactor. The results showed the maximum stress and deformation of the reactor were 75.288 MPa and 3.680 mm during aerobic composting, respectively, fully meeting the high requirements of standard design. At the same time, the EDEM and Fluent simulation were then used to analyze the movement of materials during aeration and discharging. The results showed that the discharge rate of the reactor was 98.14% at the string speed of 20 r/min, and the gas volume fraction was above 90% during aeration. Better performance of the reactor was achieved in the discharge and aeration system during this time. A series of experiments was carried out on aerobic composting, particularly with the chicken manure and corn straw that were mixed at a ratio of 1:4 (dry weight basis). It was found that there was no significant difference in the temperature of the same layer during composting of the three batches (P>0.05). Specifically, the duration of the high-temperature period (higher than 50 °C) was maintained 9, 7 and 5 days, respectively, for the three raw materials. It infers that the composting fully met the ecological demand of harmless in this case. More importantly, the pH values were between 8.0 and 9.0, whereas, the electrical conductivity (EC) values were between 2.0 and 3.0 mS/cm during composting of three batches. There was a significant difference in the pH and EC values of each layer (P<0.05). However, there was no significance (P>0.05) at the same layer during the three batches. Moreover, the seed germination rates were also all above 100%. In addition, the degradation rates of volatile solid (VS) were 14.99%, 16.03%, and 13.24%, respectively, in the three batches. Hence, the stable properties of composting were achieved in the excellent performance of the developed reactor. Therefore, the improved composting reactor can be expected to serve as the aerobic composting reactor in the utilization of agricultural wastes.

       

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