磷化氢熏蒸对周边环境空气的影响

为研究烟叶醇化库使用磷化氢熏蒸杀虫对周边环境空气的影响,现场采集杀虫前、投药、密闭、散气4个阶段的周边环境空气样品,采用GBZ/T 160.30—2004中的方法测定了2007—2016年连续10年的烟叶醇化库周边环境空气样品中的磷化氢浓度。结果表明:(1)杀虫前、投药、密闭、散气4个阶段,库区周边环境空气中磷化氢浓度分别为未检出～0.13、未检出～0.18、未检出～0.12、未检出～0.67 mg/m3。(2)磷化氢熏蒸杀虫的散气阶段对周边环境影响最大,在磷化氢的净化技术还不成熟的2008年,其最高浓度为0.67 mg/m3。将磷化氢熏蒸过程的散气阶段作为重点防控,可有效降低对周边环境的影响。     

磷化氢横向环流熏蒸技术在稻谷储藏中的应用

研究了18 m跨度平房仓磷化氢横向环流熏蒸系统设计方案和横向环流熏蒸技术在稻谷储藏中的应用工艺。粮堆内部磷化氢浓度检测结果表明,在磷化氢横向环流时粮堆内各竖直截面和水平层面磷化氢浓度分布均匀,变化趋势一致,没有熏蒸死角。与传统整仓熏蒸相比,采用横向环流熏蒸技术熏蒸粮堆时,磷化氢浓度均匀,熏蒸时间短,能够快速达到杀虫浓度;且覆膜密闭,能延长磷化氢浓度的保持时间,有效降低磷化氢用药量。     

浅圆仓熏蒸过程中磷化氢扩散和分布特性研究

在直径27 m、装粮线高度18 m,仓内体积12 000 m3,压力半衰期为600 s的浅圆仓中,采用粮面药袋投药和两侧梳型风道环流熏蒸,研究了浅圆仓粮堆纵向和横向上磷化氢扩散及分布特性,评估了粮堆内部不同部位磷化氢Ct值。结果表明,浅圆仓粮堆内磷化氢浓度衰减阶段的浓度呈指数下降趋势,磷化氢浓度衰减阶段浓度和时间符合指数模型C=1 061.7e-0.071t模型（R2=0.917 1）其中C为磷化氢浓度,mL/m3;t为熏蒸时间,d;e为自然指数）。环流熏蒸系统促进粮堆内磷化氢的均匀分布,可以避免因过高浓度造成的不利,但粮堆内磷化氢在不同区域浓度仍然存在差异,且难以避免熏蒸死角的存在。在浅圆仓熏蒸初期,从横向方向看,磷化氢在中轴聚集,浓度以中轴为中心向仓壁递减;从纵向方向看,磷化氢从上到下浓度依次降低,粮堆内表层和中轴处磷化氢浓度相对较高。在磷化氢浓度衰减阶段,粮堆中间层和中轴处磷化氢浓度相对较高。浅圆仓环流熏蒸系统A面管、B面管和仓底取样口Ct值低于平均浓度累积值,存在害虫防治隐患。在实际工作中可通过优化改进环流熏蒸风道可以改变粮堆内磷化氢气体的分布。     

小麦高大平房仓磷化氢横向环流熏蒸技术研究

研究了60 m×21 m平房仓磷化氢横向环流熏蒸系统设计方案和横向环流熏蒸技术在小麦储藏中的应用工艺。密闭小麦粮堆内部磷化氢浓度检测结果表明,在磷化氢横向环流时粮堆内各竖直截面和水平层面磷化氢浓度分布均匀,变化趋势一致,没有熏蒸死角。与传统整仓熏蒸相比,采用横向环流熏蒸技术熏蒸时,磷化氢浓度均匀,熏蒸时间短,能够快速达到杀虫浓度;且覆膜密闭,能延长磷化氢浓度的保持时间,有效降低磷化氢用药量。     

浅圆仓磷化氢双侧内环流熏蒸效果研究

采用粮面投药,双侧环流熏蒸的方式测试,研究了浅圆仓不同粮层、粮面空间、出粮口、环流管道中磷化氢浓度的分布变化,分析了磷化氢在粮堆内分布扩散规律。结果表明,浅圆仓粮堆内部磷化氢浓度在第6天才能达到0.6的均匀度,虽然两侧环流管内的磷化氢浓度只需1~2天即达到200 mL/m~3以上,但仓底出粮口的磷化氢浓度到第八天仍未达到200 mL/m~3。因此,只检测环流管和粮面空间的磷化氢浓度不能表明粮堆内各处浓度都达到相同水平,不能保证熏蒸杀虫效果,同时也不能以此来决定环流停止的时间,因为粮堆浓度达到均匀的时间远远滞后于环流管内浓度达到熏蒸要求的时间。这一结果对指导浅圆仓环流熏蒸,保证熏蒸杀虫效果具有重要意义,具有较大实用价值。     

储粮熏蒸过程中磷化氢浓度的分布模型及验证研究

谷物在长期储存过程中会受到害虫的侵扰,通常需要使用诸如磷化氢等适量的熏蒸剂对仓储粮食进行熏蒸,从而杀死害虫,同时又要避免害虫产生耐药性和熏蒸剂的残留。本研究首先建立和验证了熏蒸剂(磷化氢)的对流扩散和吸附模型,并采用计算流体动力学方法对圆筒仓内谷物熏蒸过程中磷化氢质量浓度进行了数值预测,分析了熏蒸过程中磷化氢的质量浓度分布规律,得出熏蒸过程中磷化氢质量浓度分布是不均匀的,并且受到谷物吸附和不可逆化学反应的双重影响。     

高大平房仓不同熏蒸方式浓度分布研究

本研究通过膜下环流熏蒸、氮气气调、氮气与磷化氢混合熏蒸三种熏蒸方式,来分析在高大平方仓中这三种方式施药后,熏蒸气体的空间浓度分布情况。结果表明,覆膜环流熏蒸仓房底部磷化氢浓度在第3 d达到最大,较常规熏蒸快2～4 d。氮气和磷化氢混合熏蒸在环流6 h后各层粮堆内气体分布基本达到均匀,整个熏蒸过程中磷化氢最低浓度与最高浓度的比值范围为0.37～0.67,氮气浓度始终保持在83%～87%之间。混合熏蒸与膜下环流熏蒸相比,可以减少用药量10.8%;同时,解决了氮气气调对气密性要求严苛以及运营成本高的难题,供粮食仓储企业在实际熏蒸杀虫工作中参考。     

实仓与模拟熏蒸完全致死磷化氢抗性锈赤扁谷盗试验研究

锈赤扁谷盗是当前普遍发生且采用磷化氢熏蒸难以有效治理的储粮害虫,为了探讨抗性锈赤扁谷盗的实仓治理效果,在大型浅圆仓中采用磷化氢与二氧化碳仓外施药环流熏蒸实仓,研究了对5个高抗性锈赤扁谷盗品系的现场杀虫效果,并比较了室内模拟熏蒸条件下磷化氢对高抗性锈赤扁谷盗的致死情况。试验结果为:在实仓条件下,磷化氢浓度在700ml/m~3以上维持3d,在500ml/m~3以上维持11d,抗性系数为560~668倍的5个强抗性锈赤扁谷盗品系在15d内完全死亡;在模拟熏蒸条件下,保持磷化氢浓度500ml/m~3,完全杀死同样抗性的锈赤扁谷盗品系需要24d。在实仓熏蒸下,采用磷化氢和二氧化碳仓外施药、环流并保持磷化氢浓度在760~370ml/m~3的浓度变化水平,可在15d的时间内完全致死强抗性锈赤扁谷盗,且致死效果明显好于模拟条件下单独采用500ml/m~3磷化氢浓度的杀虫效果,仓外施药中二氧化碳和较高磷化氢浓度有利于促进对抗性锈赤扁谷盗的熏蒸治理。     

储烟害虫防治过程中减少磷化氢使用量和排放量的措施

为了减少烟草仓贮害虫防治过程中磷化氢的使用量和向大气的直接排放量,考察了不同清洁隔离措施对仓内虫口数量的影响,开展了不同温度条件下低剂量磷化铝熏蒸试验及熏蒸余气磷化氢的化学吸收处理试验。结果发现:1)隔离仓间内的虫口数量远低于普通仓间;2)在夏季较高温度条件下,磷化铝熏蒸的用药量可以由常规的6.0 g/m3左右降低至4.0 g/m3左右;3)饱和漂粉精溶液能有效吸收磷化氢,但在大规模试验中难以实现一次性的彻底净化。研究表明,减少磷化氢的使用量和排放量,应当从加强清洁隔离、适当降低磷化铝熏蒸的单位体积用药量、对熏蒸余气进行净化处理等三个方面采取综合措施。     

粮堆磷化氢浓度衰减阶段数学模型及验证研究

研究了压力半衰期为158 s的高大平房仓中磷化氢熏蒸后的浓度变化规律,建立了粮堆内磷化氢浓度和熏蒸时间的关系模型。经压力半衰期分别为105、96、69 s的三个高大平房仓磷化氢浓度变化的实仓验证,表明粮堆内磷化氢浓度衰减阶段的浓度呈指数下降趋势,磷化氢浓度衰减阶段浓度和时间符合指数模型C=ae~(-bt)(a0;b0)(其中C为磷化氢浓度,m L/m~3;t为熏蒸时间,d;e为自然指数;a、b为常数)。该模型可用于计算不同磷化氢浓度对应的熏蒸时间、不同熏蒸时间对应的磷化氢浓度、预测粮堆的补药时间等。结合气体发生阶段模型还可以计算磷化氢熏蒸最大浓度、最低熏蒸浓度下的有效熏蒸时间以及磷化氢浓度半数衰减时间HLT。     

磷化氢环流熏蒸生产性应用研究

以高大房式仓散存硬麦为实验对象,运用磷化氢环流熏蒸装备,分别采用仓外施药、仓外与粮面施药相结合、仓外与粮面间歇投药法不同方式生产性应用。根据不同区域和厂房条件,可以制定经济、安全、有效的熏蒸工艺,节省熏蒸时间,且浓度均匀,杀虫效果好。     

Developing and verifying a fumigant loss model for bulk stored grain to predict phosphine concentrations by taking into account fumigant leakage and sorption

To ensure fumigation effectiveness and address phosphine resistance concerns, fumigant concentrations and movement in a grain storage silo need to be understood. A mathematically accurate fumigation model was developed that is capable of predicting fumigant concentration and movement throughout a grain storage silo that takes into account fumigant loss from leakage and sorption, and was verified with experimental fumigation data. Equations estimating fumigant leakage and sorption were developed based on literature values and added to an existing finite element model. Fumigation data was used from a fumigation conducted on an Australian made silo filled with 45.5 tonnes of maize in Manhattan, Kansas. Two verifications were conducted based on phosphine concentration release times of 24 h and 30 h, with both verifications demonstrating accurate prediction of phosphine fumigant values and trends. The two verifications resulted in concentration-time products that were within 0.9% and 4.3% of the experimental values, respectively. The fumigation model is most accurate during the times of highest phosphine concentration. However, the model under predicted phosphine concentrations during the first 12 h of fumigation and over predicted phosphine concentrations beyond the first six days of fumigation. This fumigation model was found to be sufficiently accurate to allow for future experimentation on predicting fumigant concentrations as a function of environmental conditions and operational variable.     

Mathematical modelling and numerical simulation of phosphine flow during grain fumigation in leaky cylindrical silos

The phosphine distribution in a cylindrical silo containing grain is predicted. A three-dimensional mathematical model, which accounts for multicomponent gas phase transport and the sorption of phosphine into the grain kernel is developed. In addition, a simple model is presented to describe the death of insects within the grain as a function of their exposure to phosphine gas. The proposed model is solved using the commercially available computational fluid dynamics (CFD) software, FLUENT, together with our own C code to customize the solver in order to incorporate the models for sorption and insect extinction. Two types of fumigation delivery are studied, namely, fan-forced from the base of the silo and tablet from the top of the silo. An analysis of the predicted phosphine distribution shows that during fan forced fumigation, the position of the leaky area is very important to the development of the gas flow field and the phosphine distribution in the silo. If the leak is in the lower section of the silo, insects that exist near the top of the silo may not be eradicated. However, the position of a leak does not affect phosphine distribution during tablet fumigation. For such fumigation in a typical silo configuration, phosphine concentrations remain low near the base of the silo. Furthermore, we find that half-life pressure test readings are not an indicator of phosphine distribution during tablet fumigation.     

不同施药方式硫酰氟熏蒸高大平房仓效果比较研究（网络首发、推荐阅读）

通过比较分析3种不同实仓施药方式硫酰氟熏蒸高大平房仓的穿透力、均匀性和杀虫效果,探索硫酰氟在实仓熏蒸的最佳工艺。结果表明,硫酰氟气体可在2.5 h内自然扩散穿透粮堆,24 h左右达到整仓基本均匀。环流熏蒸可以加速气体均匀,但此次实验环流过程中导致了一定药剂损失。在整仓熏蒸、膜下上行环流和膜下下行环流的3种熏蒸方式中,整仓熏蒸操作最为简便,可用于快速杀灭成虫;膜下上行环流方式,药剂损耗量较大;膜下下行环流,浓度均匀速度快,用药量较整仓小,药剂浓度保持时间长,杀虫效果好。     

Modeling post-fumigation desorption of phosphine in bulk stored grain

Phosphine is a dangerous gas commonly used in fumigations of stored grains throughout the world. Grain that has not fully released the phosphine it absorbed during fumigation may continue to desorb phosphine into the headspace of a shipping container or storage. USOSHA standards for handling phosphine state the acceptable Threshold Limit Value (TLV) of 0.3 ppm. In many cases, during grain transport and handling, the level of phosphine in work environments can exceed the 0.3 ppm TLV which resulted from desorption of phosphine from fumigated grains. It is also important to note that desorbing grain, with low concentrations of phosphine, can facilitate insect resistance. Therefore, it is important to understand the process of phosphine venting and desorption in order to ensure safe handling of fumigated grain. In order to achieve this, the venting and release of phosphine was studied on location in a well-sealed grain silo in Lake Grace, Western Australia. The data set served for verification of a 3D finite element ecosystem model and were compared to the predicted results. Results were calculated using two different fumigant desorption models based on previous literature, i.e., a reversed sorption model and an air-grain equilibrium model. Simulations reproduced accurate trends of desorption but did not accurately reproduce the quantity of fumigant, with 55.5% error for the model based on reversed sorption equations, and 86.3% error for the air-grain equilibrium based model. For both models, additional simulations were conducted to compare the effectiveness of existing grain venting regulations at producing grain that is within post-fumigation safe handling limits. Results revealed that current U.S. standards may be insufficient to guarantee safety based on minimum venting times needed. These results highlight the necessity for continued research into phosphine desorption and the importance for establishing realistic post-fumigation venting guidelines.     

基于PyroSim的粮食储备库火灾仿真模拟分析（网络首发、推荐阅读）

为研究粮食储备库发生火灾后对作业人员的影响,应用PyroSim软件对粮食储备库进行火灾模拟。选取应用较为广泛的平房仓为研究对象建立物理模型,针对磷化氢熏蒸口引起的火灾场景,分析火灾烟气发展和温度分布情况,并提出预防措施。结果表明：烟气形成阶段和向上发展阶段为灭火和作业人员疏散的最佳时期,此时烟气尚未弥漫至整个仓房;烟气在顶部扩散时作业人员应马上撤离;烟气充满仓房时作业人员严禁进入仓内;10~100 s之间是火灾发生和发展阶段,1.5 m以下范围仓房温度未达到人员极限忍受范围;100 s到10 min由于燃烧物充分燃烧,温度不断升高,作业人员面临烧伤风险。     

硫酰氟熏蒸在砖圆仓应用效果评价研究（网络首发、推荐阅读）

为探索砖圆仓硫酰氟熏蒸杀虫和防护效果,分别在3个不同气密性仓房,分别采用整仓不环流熏蒸和环流熏蒸,以及采用不同的熏蒸药剂浓度,通过分析比较气体均匀性,浓度保持时间和杀虫防护效果进行评价。试验结果表明,硫酰氟气体可在4 h内自然扩散穿透10 m粮堆,并在24 h内达到整仓气体均匀。环流熏蒸由于环流管道老化造成药剂损失,气体浓度保持时间短。5 g/m3的药剂浓度即可实现较好的快速杀灭4种主要储粮害虫的效果。     

PH3 residues in hazelnuts, soybeans and wheat following phosphine fumigation with non-constant concentrations

In model tests hazelnuts, soy beans and wheat were fumigated with phosphine (PH3) at non constant concentrations. The influence of different concentration characteristics on the fumigation and the decomposition of phosphine residues was investigated in accordance with the fumigation technique. At the beginning the concentration increases, and after attaining the maximum gradually decreases to zero. The level of residues during the fumigation as well as the behaviour of residues during the storage of the fumigated products was monitored with a gas chromatographic method. The residues correlate with the concentration of phosphine, they also pass through a peak. The rate of decomposition of residues which had been formed in the phase of increasing concentration is greater than the rate of residues of equal magnitude which had been formed during the decreasing phase. When the concentration is even the maximum residue occurs later than the maximum concentration; when there is a steep trend both maximums coincide. This behaviour can be explained by the sorption and diffusion of phosphine. A comparison is made with the phosphine concentration which occurs during fumigation in practice. The parameters which produce a constant concentration trend with only one maximum and a non constant trend with an often increasing and decreasing concentration are discussed. The different behaviour of residues in these cases is described. Conclusions are drawn for the practice of fumigation.