Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
2001-10-25
2004-06-08
Lo, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C073S073000
Reexamination Certificate
active
06747461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to artificial drying processes, and in particular, to automatically monitoring the moisture content of the material being dried during the drying process.
2. Problems in the Art
Many types of materials must be artificially dried as part of their processing. Some of those materials are porous media. The term “porous media”, as used herein, means any material that has the ability to retain water, including collections of individual pieces of material, whether or not themselves “porous media”. By artificial drying, as used herein, it is meant human or machine adjustable application of thermal energy and/or airflow: not a natural application of heat and/or airflow.
A particular example is seed corn. It must be harvested, handled carefully, and usually artificially dried to remove a portion of water it retains. The artificial drying process must be controlled to maintain seed quality, as opposed to non-artificial drying in the natural field environment.
Sometimes this artificial drying is done after the seed has been separated from its carrier, the cob (shelled). Sometimes it is done while the seed corn is still on the cob. In the latter case, ear corn is normally artificially dried in a large bin. It is desirable that the artificial drying removes moisture from the corn down to a certain level at a certain rate. If moisture is removed too quickly, it could damage seed quality. If moisture is removed too slowly, it could also damage seed quality. This can be extremely important. For example, improperly dried seed may not germinate when planted. Thus, it is important to not only monitor drying temperature, but also drying rate and level of moisture in the seed.
One conventional way of such artificial drying of ear corn is to place a relatively large quantity of ear corn (e.g. several tens of bushels) in a relatively large bin (e.g. 125 to 10,000 cubic feet), and manually adjust airflow and temperature of air through the ear corn. Seed corn weighs roughly 85 lbs./ft.
3
so there would be thousands of pounds of seed corn in each bin of this size. Normally drying is done simultaneously in multiple such bins. Samples are manually removed periodically and tested for moisture content. Airflow and temperature can then be adjusted to maintain the desired rate of moisture removal. General discussions about the drying of seed corn can be found at: Production of Hybrid Seed Corn, pages 565-607, In: Corn and Corn Improvement 3
rd
Edition, Edited by G. F. Sprague and J. W. Dudley, Published by the American Society of Agronomy 1988; Physiology of Drying in Maize. J. S. Burris, Pages 1-7, Proceedings of the Seventeenth Annual Seed Technology Conference. Feb. 21, 1995.
Hybrid seed corn is usually artificially dried to allow it to be harvested prior to frost, before being damaged by insects, infected by fungal pathogens, or before the ear falls off the plant. Typically it will take 3 to 4 days for a bin of freshly harvested corn to dry from an initial moisture content of 36% down to a final moisture content of 12%. This rate is determined by the current moisture of seed within a dryer bin, its genotype, and the demand for dryer capacity.
The maximum rate at which seed may be safely dried is determined by the specific drying injury susceptibility of each genotype. If the dryer's operating conditions are too aggressive, such as too high of temperature or too much airflow, drying injury may occur. These conditions are potentially different for each genotype dried, with harvest moisture interacting with genetic susceptibility in determining ideal drying conditions. Below this maximum rate the seed may be dried at a wide range of possible rates. However, if the dryer's operating conditions (dryer temperature and airflow) are not properly selected, drying may take an unnecessarily long time, resulting in lost drying capacity and increased energy consumption.
Therefore, two goals are a better final product after artificial drying and more efficient drying. In the case of ear corn, to achieve good levels of efficiency, a relatively large bin is needed to artificially dry a batch of a relatively large amount of ear corn together over a relatively long period of time.
The problem with the above-described method of monitoring drying rate is that it is quite cumbersome. To check on moisture levels of the drying ear corn, samples are periodically manually removed from the dryer bin and known laboratory techniques used to derive moisture content of the corn sample. A worker must physically gain entrance to the drying chamber (e.g. through a door) and manually extract one or more sample ears. Some bins are large enough that the worker can substantially enter the bin and grab ears of corn. Others have doors or access openings big enough for the worker to reach into the corn. However, in most cases, the worker can only reach a few feet deep into the pile of corn (e.g. up to his/her elbow) and extract an ear or two. If the ear is grabbed from near the top of the pile, the top is many times the last part of the pile to dry (if heated air is supplied from the bottom). Therefore, ears extracted from the top may not accurately characterize moisture content of the majority of the pile. Thus, many times the worker extracts ears from several places in the pile (e.g. 8 to 10 ears). This greatly increases the manual work involved.
The worker must then remove some seed from each extracted ear (again usually manually). The removed seed must then be manually handled and loaded into a machine or device for analysis (usually by laboratory-type moisture measuring equipment). After the results are obtained (normally after a period of time and not in real time), they can then be used to evaluate the drying process and/or to control the drying process. Many times this means the worker must key the moisture data into a computer.
Not only is the above-described process time-consuming, cumbersome, and labor intensive (drying usually proceeds over several days with moisture measures taken several times each day), it is difficult, if not impossible, to remove actual samples from very deep in the bin. Therefore, it is difficult to really test how drying is proceeding throughout the bin. Moisture readings from ear corn taken from the top, bottom, or a side of the bin may not be accurate for other locations in the bin, such as the middle of the bin. Such readings may mislead and cause application of a moisture removal rate detrimental to the corn. Furthermore, this process is subject to operator errors and accuracy problems. These problems are amplified because typically 72 to 96 dryer bins are run simultaneously to artificially dry a plurality of batches of relatively large amounts of corn.
There have been attempts to automate the drying process. For example, see U.S. Pat. No. 5,893,218 to inventors Hunter, Precetti and Chicoine, incorporated by reference herein. That patent discloses a system that makes it easier to control airflow rate and temperature in such relatively large dryer bins. But it relies on known moisture measuring methods, such as described above.
Therefore, it would be very helpful to also have automated measurement of moisture content or monitoring of drying rate of the ear corn in essentially real-time during the drying process. This intelligence could be used to monitor artificial drying and/or be used by an automated artificial drying apparatus to control the drying process.
Attempts have been made to create devices to measure moisture in porous media, including shelled corn or ear corn. One such example is the use of a radioactive source (e.g. neutron probe). A major problem with such a detector is that it creates safety issues for workers. It also requires special licensing and administrative burdens that are not insubstantial.
Another attempt uses a capacitance probe. Its primary deficiency is that it can only measure moisture near the bottom of the bin.
Microwave instruments, on the order of 1′×1′, have
Corak Steven J.
Hunter James L.
Skaling Whitney
Lair Donald M
Lo N.
Pioneer Hi-Bred International , Inc.
Pioneer-Hi-Bred International, Inc.
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