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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #321204
Title: Real-time monitoring of peanut drying parameters in semitrailers

Author
item Lewis, Micah
item Trabelsi, Samir
item NELSON, STUART - Former ARS Employee

Submitted to: Drying Technology: An International Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2016
Publication Date: 3/23/2017
Citation: Lewis, M.A., Trabelsi, S., Nelson, S.O. 2017. Real-time monitoring of peanut drying parameters in semitrailers. Drying Technology: An International Journal. 35(6):747-753.

Interpretive Summary: Peanut drying is an essential task that takes place at peanut buying stations and shelling plants, preceding the grading process. Although peanuts are left in windrows to dry naturally before being harvested with combines, they arrive at buying stations considerably high in moisture content. Therefore, it is imperative for peanuts to be dried below 10.5percent kernel moisture content for grading, sale and storage purposes. To facilitate the drying process, peanuts are loaded into drying wagons or drying trailers. Then, dryers using propane or natural gas fuels are connected to the wagons and trailers through canvas ducts, and heated air is blown into the airspace below the bed of peanuts. The air is forced up through the peanuts to decrease their moisture content. Peanuts are dried in this fashion until they are expected to have less than 10.5percent moisture content. Knowledge of pertinent peanut drying parameters such as temperature and relative humidity of the ambient air, temperature and relative humidity of the air being blown into the peanuts, and kernel moisture content is essential in managing the dryer for optimal drying rate. The optimal drying rate is required to preserve quality and desired flavor. In the current peanut drying process, such parameters are elusive in real-time and are either not measured or only measured periodically by an operator. A peanut drying monitoring system, controlled by an embedded microcontroller, consisting of relative humidity and temperature sensors and a microwave moisture sensor was developed to monitor drying parameters in real-time. It was deployed during the 2014 peanut harvest season at a peanut buying point in central Georgia. It was placed in 45-ft drying semitrailers to monitor in-shell kernel moisture content, temperature of the drying peanuts, temperature and relative humidity of the exhaust air from the peanuts and relative humidity of the air being blown into the peanuts. In-shell kernel moisture content was monitored with a microwave moisture sensor with an accuracy of about ½percent moisture content. In these trials, data were assessed to evaluate the uniformity of peanut drying. The movement of the drying front through the peanut bed was captured by real-time monitoring. Real-time monitoring of the drying parameters was also able to capture periods of nonbeneficial drying. During such periods kernel moisture content was observed to either remain constant or increase slightly, and relative humidity of the air being blown into the peanuts was above 70percent. Eliminating these periods of nonbeneficial drying can save an average size buying point $22,000 annually. The peanut drying monitoring system is a valuable aid in providing the buying point personnel with real-time data that would allow them to make better informed decisions; therefore improving the efficiency of peanut drying by eliminating underdrying, overdrying and nonbeneficial drying. The monitoring system could also be incorporated into the drying system control to automate the operation with even better efficiency, saving operating costs and providing improved peanut quality for the benefit of growers, handlers, marketers and consumers.

Technical Abstract: Knowledge of peanut drying parameters such as temperature and relative humidity of the ambient air, temperature and relative humidity of the air being blown into the peanuts and kernel moisture content is essential in managing the dryer for optimal drying rate. The optimal drying rate is required to preserve quality and desired flavor. In the current peanut drying process, such parameters are elusive in real-time and are either not measured or only measured periodically by an operator. A peanut drying monitoring system, controlled by an embedded microcontroller, consisting of relative humidity and temperature sensors and a microwave moisture sensor was developed to monitor drying parameters in real-time. It was deployed during the 2014 peanut harvest season at a peanut buying point in central Georgia. It was placed in 45-ft drying semitrailers to monitor in-shell kernel moisture content, temperature of the drying peanuts, temperature and relative humidity of the exhaust air from the peanuts and relative humidity of the air being blown into the peanuts in real-time. In-shell kernel moisture content was determined with a standard error of performance of 0.55percent moisture content when compared to the reference oven-drying method. Data from drying parameters were time-stamped and stored on a CompactFlash card every 12 seconds and were used to assess the efficiency of dryer control settings. In some cases, two monitoring systems were placed in a single semitrailer with one near the front and one near the back. In such trials, data were assessed to evaluate the uniformity of peanut drying. Results of the study support the value of such a monitoring system and show that implementation of the system for dryer control has the potential for saving a buying station as much as $22,000 annually in electric energy and propane costs.