蒸汽消毒管结构参数对红壤消毒加热效率的影响

Effects of steam disinfection pipe structure parameters on the heating efficiency of red loam steam disinfection

为解决云南红壤蒸汽消毒过程中消毒加热效率低的问题,开展了消毒管结构参数对土壤消毒加热效率的影响效应研究,并对消毒管结构参数进行了优化设计。首先,运用图像处理技术构建出土壤孔隙结构离散模型;其次,对消毒管内蒸汽流场土壤蒸汽消毒过程进行了仿真模拟分析;最后,基于土壤蒸汽消毒试验平台,开展了多因素消毒管结构参数优化试验研究。研究结果表明:1)消毒管出气孔周向和轴向孔数对红壤蒸汽消毒加热效率影响极显著(P<0.01);消毒管最佳结构参数为出气孔孔径2 mm、周向孔数为3个、轴向孔数为2个,土壤平均温度达到80℃时的试验消毒时长平均值为394 s,试验结果与预测结果之间的平均误差率为5.3%;2)消毒200 s时,各处理土壤升温速率达到峰值,消毒200 s后加热效率逐渐降低,即消毒200 s时应逐渐减少蒸汽的流量,当土壤温度低于60℃需再次增加蒸汽的流量,依次循环往复保证土壤温度始终在60℃以上,以达到高效灭菌的目的;3)单管红壤高温区域范围主要集中在水平方向0~150 mm,垂直方向0~200 mm。该研究可为土壤蒸汽消毒机消毒管的结构设计和智能消毒作业提供理论依据,并为末端执行装置多管间距的设计奠定理论基础。

Soil continuous cropping has been an ever-increasingly serious threat to modern agriculture in recent years.The soil disinfection method can be expected to effectively alleviate the soil's continuous cropping.Furthermore,the soil steam disinfection can be sown in a short period of time after disinfection,due to the non-toxic,pollution-free,compared with the chemical methods.But the low disinfection and heating efficiency has been limited in the process of red loam steam disinfection in practice.In this study,the disinfection pipe structural parameters were optimized to clarify the influence on the soil disinfection heating efficiency.Firstly,image processing was used to construct a soil pore structure discrete model.Secondly,the simulation was implemented to analyze the steam flow field in the disinfection pipe and the single-factor soil steam disinfection.Finally,the experiment was performed on the optimized structural parameters of multi-factor disinfection pipes using the soil vapor disinfection test platform.The results show that:1)The circumferential and axial outlets of the disinfection pipe posed a significant effect on the heating efficiency of steam disinfection(P<0.01).The optimal structural parameters of the disinfection pipe were achieved:2 mm pore size of the outlet pore,3 circumferential pores,2 axial pores.The average disinfection duration of the test when the average soil temperature reaches 80℃is 394 s,and the average error rate between the test results and the predicted results is 5.3%;2)The soil heating rates of each treatment reached the peak when the steam disinfection was carried out for 200 s.The efficiency of disinfection and heating gradually decreased after 200 s of disinfection.Future practical operations need to be guided by the variation of soil heating rate.Specifically,the steam valve should be gradually closed,the steam flow should be suspended,and the excess water in the soil should be removed to provide the soil pore permeability when the heating rate decreased gradually.Therefore,an intelligent control system can be expected to be combined,when conducting steam disinfection operations on Yunnan red loam in the later stage.The steam flow rate should be gradually reduced when disinfecting for 200 s.The soil temperature was redistributed and gradually decreased,as time increased.Once the soil temperature was below 60℃,the steam flow rate should be increased again,and the flow rate should be reduced and increased in a cyclic manner to ensure that the soil temperature was always above 60℃,in order to achieve the goal of efficient disinfection.The findings can provide a theoretical basis for efficient disinfection operations.3)The range of single-pipe high-temperature areas in each treatment was mainly concentrated in the horizontal direction 0-150 mm and the vertical direction 0-200 mm.This study can provide a theoretical basis for the structural design of the disinfection pipes in the steam sterilizers and the intelligent disinfection operation,and lay a theoretical research foundation for the design of multi-pipe spacing of end actuators.