Evolution of phosphine from aluminum phosphide pellets

Authors: ELSAYED, SHERIF - Kansas State University; Casada, Mark; MAGHIRANG, RONALDO - University Of Illinois; WEI, MINGJUN - Kansas State University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2020
Publication Date: 2/1/2021
Citation: Elsayed, S., Casada, M.E., Maghirang, R., Wei, M. 2021. Evolution of phosphine from aluminum phosphide pellets. Transactions of the ASABE. 64(2):615-624. https://doi.org/10.13031/trans.14326.
DOI: https://doi.org/10.13031/trans.14326

Interpretive Summary: Phosphine is widely used as a fumigant for stored product insect infestations due to its relatively low price and the absence of residual chemical left on the grain. Understanding the behavior of phosphine gas inside the fumigated space is crucial to maintaining a lethal dosage and protecting stored grain from subsequent insect damage. Phosphine is available in either gas form or when produced from solid material, in pellets or tablets, that reacts with water in the air. The solid form is the most commonly used; however, limited information is available on the rate of phosphine gas generated from the solid material. A mathematical equation was formulated to describe the rate, based on previous studies in the literature, and incorporated in a computer model to predict the phosphine concentration within fumigated grain. The model accounted for temperature, relative humidity, and the amount of phosphine absorbed by wheat that reduces the overall gas concentration. Results from a laboratory experiment using a single pellet with wheat in a sealed barrel were used to validate the mathematical model. The gas generation model will enable accurate computer simulations of phosphine fumigations that will help improve understanding of factors affecting the fumigation process, lead to better control of those factors, and help ensure phosphine fumigation effectiveness.

Technical Abstract: Phosphine gas (PH3) is widely used as a fumigant for stored product insect infestations due to its relatively low price and the absence of residual chemical on the grain. Understanding the behavior of phosphine gas inside the fumigated space is crucial to maintaining a lethal dosage and protecting stored grain from subsequent insect damage. Phosphine is available in either gas form or when produced from solid material, in pellets or tablets, that reacts with water in the air. The solid form is the most commonly used; however, limited information is available on the rate of phosphine gas generated from the solid material. A mathematical equation was formulated, based on previous studies in the literature, to describe the rate. This equation was incorporated in a computational model using ANSYS Fluent 19.1, a renown commercial software for Computational Fluid Dynamics (CFD) analysis. The computational model developed here allows prediction of the phosphine concentration within a fumigated grain bulk. The gas generated by a single pellet was measured in laboratory experiments in a 0.208 m^3 sealed barrel. The measurements from the laboratory experiments confirmed the mathematical model and computational results.