Mark E. Casada

Fringing Field Capacitance Sensor for Measuring the Moisture Content of Agricultural Commodities

A fringing field capacitive sensor is described for measuring the moisture content (MC) and temperature of agricultural commodities. Sensor performance was characterized by mounting the device on handheld probes and in acrylic canisters to determine the dielectric constant and MC of wheat and corn. The handheld probes demonstrated a promising capability to measure the MC of grain in hoppers, truck beds, and cargo holds. It is proposed that the sensors be supported on cables in grain silos and storage bins to acquire in situ data for grain storage management and control of aeration systems. The sensor is watertight and constructed with corrosion resistant materials which allow MC measurements to be made of industrial materials, chemicals, and fuels.

Applications of Discrete Element Method in Modeling of Grain Postharvest Operations

Grain kernels are finite and discrete materials. Although flowing grain can behave like a continuum fluid at times, the discontinuous behavior exhibited by grain kernels cannot be simulated solely with conventional continuum-based computer modeling such as finite-element or finite-difference methods. The discrete element method (DEM) is a proven numerical method that can model discrete particles like grain kernels by tracking the motion of individual particles. DEM has been used extensively in the field of rock mechanics. Its application is gaining popularity in grain postharvest operations, but it has not been applied widely. This paper reviews existing applications of DEM in grain postharvest operations. Published literature that uses DEM to simulate postharvest processing is reviewed, as are applications in handling and processing of grain such as soybean, corn, wheat, rice, rapeseed, and the grain coproduct distillers dried grains with solubles (DDGS). Simulations of grain drying that involve particles in both free-flowing and confined-flow conditions are also included. Review of the existing literature indicates that DEM is a promising approach in the study of the behavior of deformable soft particulates such as grain and coproducts, and it could benefit from the development of improved particle models for these complex-shaped particles.

Durability and Breakage of Feed Pellets during Repeated Elevator Handling

Pelleting of animal feeds is important for improved feeding efficiency and for convenience of handling. Pellet quality impacts the feeding benefits for the animals and pellet integrity during handling. To determine the effect of repeated handling on feed pellet breakage and durability, a 22.6-t (1000-bu) lot of feed pellets made from corn meal was transferred alternately between two storage bins in the USDA- ARS, Grain Marketing and Production Research Center research elevator at Manhattan, Kansas, at an average flow rate of 62.2 t/h. Samples from a diverter-type sampler were analyzed for particle size distribution (by sieving) and durability (by the tumbling box method). The apparent geometric mean diameter of samples decreased with repeated transfers, whereas the mass of accumulated broken pellets increased with repeated transfers. The percentage of broken pellets increased by an average of 4.0% with each transfer from an initial value of 17.5%, which was within the range of published values for shelled corn obtained from the same elevator. The pellet durability index averaged 92.9% (standard deviation=0.6%) and did not change significantly (p>0.05) during the transfers. The high pellet durability index indicates that the pellets can withstand repeated transfers in feed handling systems.

Size distribution and rate of dust generated during grain elevator handling

Dust generated during grain handling can pose a safety and health hazard and is an air pollutant. This study was conducted to characterize the particle size distribution (PSD) of dust generated during handling of wheat and shelled corn in the research elevator of the USDA Grain Marketing and Production Research Center and determine the effects of grain lot, repeated transfer, and grain types on the PSD. Dust samples were collected on glass fiber filters with high volume samplers from the lower and upper ducts upstream of the cyclone dust collectors. A laser diffraction analyzer was used to measure the PSD of the collected dust. For wheat, the size distribution of dust from the upper and lower ducts showed similar trends among grain lots but differed between the two ducts. The percentages of particulate matter (PM)-2.5, PM-4, and PM-10 were 5.19%, 9.81%, and 34.1% of the total wheat dust, respectively. The total dust mass flow rate was 0.94 g/s (equivalent to 64.6 g/t of wheat handled). For shelled corn, the size distributions of the dust samples from the upper and lower ducts also showed similar trends among transfers but differed between the two ducts. The percentages of PM-2.5, PM-4, and PM-10 were 7.45%, 9.98%, and 28.8% of the total shelled corn dust, respectively. The total dust mass flow rate was 2.91 g/s (equivalent to 185.1 g/t of corn handled). Overall, the corn and wheat differed significantly in the size distribution and the rate of total dust generated.

Cost and Risk Analysis of Heat and Chemical Treatments

Abstract An economic evaluation of newly developed methods for disinfesting empty grain storage bins by heat treatment will be a useful tool for decision-making by grain storage managers. An economic empirical model of heat treatment and chemical applications was developed using minimization of costs at a target risk level associated with the grain-damaging insects Tribolium castaneum (Herbst), Sitophilus oryzae (L.), and Rhyzopertha dominica (F.). Risk was measured as a deviation below a target mortality goal (Target MOTAD). Insect mortality and air temperature during heat treatment were evaluated for empty storage bins with a full drying floor, along with a similar evaluation of insect mortality for two application rates of a contact pyrethroid insecticide, cyfluthrin 20% active ingredient (AI) wettable powder. A high-output propane heater (29 kW) had the lowest cost and risk level of all heating systems and produced 100% mortality in 2 h for the three insect species at all test locations. An electric duct-heater system (18 kW) also produced 100% mortality at all test locations after 40 h, but it had significantly higher costs. The other heating system configurations in the study had significantly higher risk levels of insect mortality, and the electric systems were not cost-effective. Both chemical rates had low costs and risk levels, with high mortality results.

HANDLING EFFECTS ON COMMINGLING AND RESIDUAL GRAIN IN AN ELEVATOR

Grain handlers have responded to an increased use of specialty grain and the resulting need for grain segregation without the benefit of experimental data in the literature quantifying the commingling that may occur during grain handling. This study was conducted to evaluate the effects of handling equipment on commingling and residual grain at an average grain flow rate of 47 t h -1 (1852 bu h -1) in the research elevator at the USDA-ARS Grain Marketing and Production Research Center in Manhattan, Kansas. Tests were done by first moving white corn through selected pieces of cleaned elevator equipment followed by moving yellow corn through the same equipment without any special clean out between the two operations. Commingling was calculated as the percentage of white kernels mixed in the yellow corn samples collected at selected time intervals during the second operation. Commingling was greater than 1% during no more than the first 38 sec and always decreased to less than 0.5% within the first metric ton of load (76 sec) for all tested equipment. The highest cumulative commingling for tests of one truckload (ca. 7.3 t) was 0.24% for the grain cleaner. Mean cumulative commingling values for the other handling equipment were 0.22%, 0.01%, and 0.18% for the weighing scale, grain scalper, and the combined effect of dump pit and boot, respectively. The residual grain obtained from cleaning the equipment after the test was highest at the elevator boot (120 kg), followed by the receiving pit (20 kg). The amounts of residual grain collected from the weighing scale, grain cleaner, and grain scalper were negligible (<1 kg) by comparison.

Thermal Conductivity of Baled Burley Tobacco

ABSTRACT The effective thermal conductivity of baled burley tobacco was determined with a thermal conductivity probe as a function of the major parameters expected to influence the conductivity. The mean value of effective thermal conductivity of baled burley tobacco was higher parallel to the leaf (0.0762 W/m°C) than it was perpendicular to the leaf (0.0453 W/m°C) because the heat was conducted through continuous solid leaf material in the parallel direction while it had to pass through successive air spaces in the perpendicular direction. The effective thermal conductivity increased linearly with increasing moisture content and increasing bulk density. The effective thermal conductivity was highest at the center of the bale and progressively lower toward the edge of the bale..

Feasibility of Summer Aeration to Control Insects in Stored Wheat

Temperature profiles and insect populations were compared in wheat that had been aerated with low airflow rates during the summer in addition to two autumn aeration cycles, versus wheat aerated in autumn only or unaerated wheat. Tests were conducted in 2000-2001, 2001-2002, and 2002-2003, and data were analyzed separately for each year. Grain mass temperature profiles at depths of 0.9 and 1.8 m from the surface in the grain mass showed distinct declines in temperature for each aeration cycle during the first two years of the study, however, summer aeration did not result in as large of temperature declines in 2002-2003, partly because the summer aerated bin was loaded with warmer grain. The effectiveness of summer aeration was estimated using confined insect populations in tube cages placed on the surface of the grain and by sampling the grain for natural insect populations using pitfall probe traps. At the conclusion of the summer aeration cycle, the number of lesser grain borer, Rhyzopertha dominica (Fabricius), red flour beetle, Tribolium castaneum (Herbst), and rice weevil, Sitophilus oryzae (L.) in the tube cages were consistently lower in bins that had not been aerated during the summer. Pitfall trap catch of rusty grain beetles, Cryptolestes ferrugineus (Stephens), hairy fungus beetle, Typhaea stercorea (L.), foreign grain beetle, Ahasverus advena (Walt), and lesser grain borer was consistently lower in bins with summer aeration, indicating a reduction in natural insect populations. Field data support modeling simulation studies that predict lower insect populations when a summer aeration cycle is included.

Temperature Monitoring and Aeration Strategies for Stored Wheat in the Central Plains

Two aeration strategies were compared to non-aeration in field tests of stored wheat in Kansas. An additional summer aeration cycle before the usual two autumn cycles produced better temperatures for insect control in the grain. Both aeration strategies yielded much better temperatures for insect control than did the naturally cooled, non-aerated bin (ca. 3,500 bu bin). In two years of tests with wheat aerated with low airflow rates in summer immediately after harvest, there were sufficient hours with air temperatures below 24°C (75°F) to cool the grain with an airflow rate of 0.11 m3/min-t (0.1 cfm/bu). However, during one year, high humidities during these nighttime periods of low temperatures resulted in final temperatures higher than 24°C due to the heating effect when the grain was slightly rewetted by the high humidity air. These results indicate the importance of looking at both temperature and humidity together to evaluate whether weather conditions are acceptable for adequate aeration cooling, especially during summer aeration when air temperatures are near the upper acceptable limit.

3-D and quasi-2-D discrete element modeling of grain commingling in a bucket elevator boot system

Unwanted grain commingling impedes new quality-based grain handling systems and has proven to be an expensive and time-consuming issue to study experimentally. Experimentally validated models may reduce the time and expense of studying grain commingling while providing additional insight into details of the particle flow. In this study, grain commingling in a pilot-scale bucket elevator boot was first modeled in three-dimensional (3-D) discrete element method (DEM) simulations. Experiments on the pilot-scale boot were performed using red-dyed and clear (uncolored) soybeans to validate the 3-D DEM model. Predicted results from the 3-D boot model generally followed the experimental data but tended to underpredict commingling early in the process. To reduce computational time, quasi-two-dimensional (quasi-2-D) DEM simulations were also evaluated. Comparison of predicted average commingling of five quasi-2-D boot models with reduced control volumes (i.e., with boot widths from four to seven times the mean particle diameter) led to the selection of the quasi-2-D model with a boot width of 5.6 times the mean particle diameter (i.e., 5.6d) to reduce computational time. In addition, the 3-D and quasi-2-D (5.6d) models were refined by accounting for the initial surge of particles at the beginning of each test and correcting for the effective dynamic gap between the bucket cups and the boot wall. The quasi-2-D (5.6d) models reduced simulation run time by approximately 70% compared to the 3-D model of the pilot-scale boot. Results of this study can be used to accurately predict commingling levels and improve grain handling, which can help farmers and grain handlers reduce costs and maintain grain purity during transport and export of grain.