Direct injection of dry flowable agricultural pesticides
Abstract
A prototype system was designed to inject dry flowable formulations of agricultural pesticides directly into the hydraulic conduit of a liquid spraying system. Initial design considerations dealt with the variability of dry flowable formulations due to particle size and potential problems associated with the interface between the dry formulation and the liquid carrier. Primary objectives were to design a direct injection system that would accurately meter and mix dry flowable formulations with liquid carriers in an agricultural environment. Representative samples of dry flowable pesticides were evaluated to quantify physical properties that affected liquid dispersion times and metering characteristics. Particle size distributions and bulk densities were determined for each pesticide formulation. Results indicated that particle distributions and bulk densities were consistent within each formulation, but varied substantially between pesticide formulations. Laboratory tests were conducted to quantify dispersion times for each pesticide formulation at recommended label rates. Results indicated that the dispersion times for packaged formulations were slow, but were reduced with liquid carrier agitation. Pesticide formulations were crushed with a mortar and pestle to investigate dispersion times as a function of particle size. Crushed formulations dispersed almost immediately upon contact with agitated water samples. A prototype system was designed and assembled to continuously meter and mix dry flowable pesticide formulations with a liquid carrier. Tests were performed to evaluate the accuracy and repeatability of the metering unit with different pesticide compounds. Metering rates were found to be dependent on the pesticide formulation, apparatus screw position and screw speed. Metering rates for a given pesticide formulation were linear for screw positions over a given operating range. The prototype unit was not compatible with all pesticide formulations tested. A laboratory test apparatus was assembled to evaluate the overall performance of the system on an agricultural sprayer. The prototype unit successfully metered and mixed Lorox$\sp\circler$ DF on a laboratory scaled agricultural sprayer. No measurable traces of pesticide residue were found on either the in-line or nozzle strainers at the closest screw setting. Some visible residue did appear at a larger screw setting. Overall performance of the system proved to be satisfactory. The prototype system was found to affect the liquid pump priming and was sensitive to reservoir liquid levels during startup procedures. An alternate metering/crushing screw design was investigated to reduce operating temperatures and broadening the range of compatible pesticides. Results indicated reduced metering rates and comparable operating temperatures. In some instances, increased operating temperatures were observed. The unit was successful in broadening the range of compatible pesticide formulations.
Degree
Ph.D.
Advisors
Gaultney, Purdue University.
Subject Area
Agricultural engineering
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