Patent Application
20150354895
The present disclosure relates to processes, systems, and apparatus for grain drying using equilibrium moisture air.
This section provides background information related to the present disclosure which is not necessarily prior art.
Grain in a grain bin can be aerated or partially dried or conditioned within a grain bin. This can be done using equilibrium moisture principles. The temperature and relative humidity of air equilibrates to a corresponding grain moisture content if exposed to that temperature and relative humidity air for a sufficient amount of time. The equilibrium moisture values are different for different grains.
Thus, grain can be aerated or conditioned while stored in a grain bin when the air is at an equilibrium moisture value or range that corresponds to the desired grain moisture content. Unfortunately, the temperature and relative humidity of the ambient air varies throughout the year (
Sometimes grain storage bins are provided with small heaters to heat the ambient air passing through the fans, which can move ambient air slightly outside the equilibrium moisture values to equilibrium moisture air. This somewhat extends the times at which the grain can be aerated or conditioned. The grain bin fan, however, still cycles on and off throughout the day, weeks, and months.
One problem with the grain bin fan repeatedly cycling off is the failure to aerate or condition the grain, and any drying front stagnates in the grain during such “off” periods. This can mean there is not enough time to fully condition the grain so that it is at the correct moisture content when it is time to go to market. This can also mean that mold or other problems appear at the stagnated drying front or elsewhere in the grain. Thus, the grain can be sold at unfavorable prices, or can spoil so it is not suitable for market at all.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
In accordance with an aspect of this disclosure, an equilibrium moisture grain drying system includes a grain drying controller electronically coupled to a variable speed fan and to one of a heater and a heat pump associated with an air plenum to supply air through the plenum and through grain in a grain bin. An ambient temperature sensor and an ambient humidity sensor can each be positioned outside the grain bin and electronically coupled to the grain drying controller. An internal plenum temperature sensor and an internal plenum humidity sensor can also each be positioned within the plenum and electronically coupled to the grain drying controller. The grain drying controller includes instructions to adjust a fan speed of the variable speed fan in combination with operation of the one of the heater and heat pump to achieve internal plenum temperature sensor data from the internal plenum temperature sensor corresponding to a target equilibrium moisture temperature during a first period when the sensor data from the ambient sensors indicates ambient air is outside the equilibrium moisture target. The grain drying controller includes instructions to operate the variable speed fan at a predetermined minimum speed during a second period when the sensor data from the ambient sensors indicates ambient air is outside the equilibrium moisture target, and the grain drying controller is unable to obtain air in the plenum within the equilibrium moisture target in view of operational limits of the variable speed fan and the one of the heater and heat pump. When the variable speed fan passes air within the equilibrium moisture target through the plenum and through the grain, the equilibrium moisture grain drying system adjusts the moisture content of grain in the grain bin toward a desired target grain moisture content corresponding to the equilibrium moisture target.
In accordance with another aspect of this disclosure, a process of operating an equilibrium moisture grain drying system is provided. The equilibrium moisture grain drying system includes a grain drying controller coupled to each of a variable speed fan and one of a heater and a heat pump to supply air through an air plenum and through grain in a grain bin, an ambient temperature sensor and an ambient humidity sensor, each positioned outside the grain bin; and an internal plenum temperature sensor and an internal plenum humidity sensor, each positioned within the plenum. The process includes adjusting a fan speed of the variable speed fan in combination with operating the one of the heater and heat pump to achieve internal plenum temperature sensor data from the internal plenum temperature sensor corresponding to a target equilibrium moisture temperature during a first period when the sensor data from the ambient sensors indicates ambient air is outside the equilibrium moisture target. Operating the variable speed fan at a predetermined minimum speed during a second period when the sensor data from the ambient sensors indicates ambient air is outside the equilibrium moisture target, and the grain drying controller is unable to obtain conditioned air in the plenum within the equilibrium moisture target in view of operational limits of the variable speed fan and the one of the heater and heat pump. When the variable speed fan passes air within the equilibrium moisture target through the plenum and through the grain, the moisture content of grain in the grain bin moves toward a desired target grain moisture content corresponding to the equilibrium moisture target.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
The present technology relates to the aeration of grain bin storage devices, and methods and systems for controlling the same. Aeration of grain bin storage devices is important in maintaining proper moisture levels in order to safely keep grain in storage for a prolonged period of time.
As used herein, a grain bin storage device refers to and includes any large container for storing something in bulk, such as grain, typically found on farms and/or used in commercial agricultural applications. Grain or feed bin storage devices may be any appropriate housing configured for grain or feed storage. They typically include sidewalls and a roof. Such bins can be generally round structures that include a raised floor creating an air plenum beneath the grain or feed. The floor can be perforated so that air can pass from the plenum through the floor and grain to remove moisture from the grain and/or adjust the temperature. Typically, a large number of small perforations is preferred to a smaller number of larger perforations for the same amount of opening in the plenum. Multiple fans can be arranged around the bin to push air into and out of the air plenum.
As used herein, the terms grain and feed, whether used singly or in combination, refer to and include various farm and/or agricultural products and materials useful with the present technology, including as non-limiting examples: all types of grains, seeds, corn, beans, rice, wheat, oats, barley, pods, potatoes, nuts, etc.
Hot air holds more moisture than cold air. Accordingly, air temperature affects the overall water-carrying capacity of the drying air. By way of example, one pound of air at 40° F. can hold about 40 grains of moisture, while one pound of air at 80° F. can hold a four-fold increase of about 155 grains. Relative humidity also plays an important part in the drying process. For example, air at 100° F. and 50% relative humidity can absorb 60 more grains of moisture per pound of air than 100° F. air can at 75% relative humidity. Thus, the amount of moisture to be removed varies with temperature and humidity of the supplied air, as well as the temperature difference of the grain and the supplied air.
Grain within a storage bin will maintain its moisture content and temperature over a period of time due to the semi-isolated environment of the storage bin and the inherent insulative properties of the grain mass. It is known that for a given type of grain, the ambient temperature and relative humidity determine an equilibrium moisture content, which represents the moisture content that the grain will equalize to if exposed for a prolonged period of time to that temperature and relative humidity condition. The equilibrium moisture content can be determined either from a table of known values, or from a mathematical formulation that approximates the data in such a table. The present technology makes this type of information for various grains available through a process controller. Alternatively, this information may be entered by a user, or obtained through various sources using internet communications or the like.
Referring to
Moisture cables 34 can also be spaced throughout the interior of grain bin 10 as diagramed in
A pressure sensor 25 may also be provided in the plenum 12 in order to be able to calculate the actual cubic feet per minute (CFM) of airflow that the fans are moving through the grain. Additional details regarding the use of measuring airflow (CFM) passing through the grain using such a pressure sensor 25 is provided in commonly owned patent application Ser. No. 13/180,797 filed Jul. 12, 2011 and published as US2013/0015251 on Jan. 17, 2013, which is hereby incorporated herein in its entirety.
A processor or controller 26, including electrical circuits in the form of a microprocessor 28 and memory 30, can be configured to receive user input and/or grain bin storage device parameters. Controller 26 is programmed as desired to have certain data (for example in memory 30) and to perform various steps. For example, such programming can include information received by controller 26 into memory from a user or from the manufacturer. Programming may also be provided by the physical design of microprocessor 28 of controller 26, by the use of software loaded into the controller 26, or a combination of hardware and software design.
The controller 26 is also operably coupled to any heater or heat pump 21, internal temperature sensor 23 and relative humidity sensor 24, external temperature sensor 23 and relative humidity sensor 24, any pressure sensor 25, any moisture cables 34 (e.g., via data collector 36), and the variable speed fan motors 22. The coupling of the various components to the controller can, for example, be via any combination of wired or wireless connections.
Referring to
The external temperature sensor 31 and humidity sensor 32 provide data or signals to the controller 26, which are converted to a measured EMC of the ambient air at box 100. Again, a formula or look-up table can be used by the controller 26 to make this conversion. If the ambient EMC (or EQM) is within the stored target range as indicated at box 102, then the controller sends a signal causing the fan 20 to operate at maximum speed as indicated at box 104.
If the ambient EMC is greater than the target EMC range, or less than the target EMC range, then the controller sends a signal causing the fan 20 to operate at a minimum speed. This minimum speed can be a set fan or motor revolutions per minute (rpm). For example, the fan may simply be operated at about one-third of the normal full speed. As another option, the controller may be programmed to use the pressure sensor 25 to calculate and operate the fan at a desired or specified minimum or low airflow rate (CFM). For example, the controller can adjust the fan speed to achieve and maintain an airflow rate through the bin of about 5000 CFM.
Another option is for the minimum fan speed to correspond to a desired low or minimum airflow rate per bushel of grain in the grain bin. For example, data or signals from the moisture cables 34 can be used to calculate the amount of grain in the grain bin and the pressure sensor 25 actual airflow rate to determine the actual CFM/Bushel and adjust the fan speed to achieve the desired minimum or low CFM/Bushel as detailed in the previously-identified commonly owned patents. Such a low or minimum CFM/Bushel can be about 0.1 CFM/Bushel, which is typically sufficient to avoid stagnation of the drying front. Alternatively, the minimum CFM/Bushel can be between about 1/14 and 1/7 CFM/Bushel, which is typically sufficient to keep the grain fresh and remove any heat caused by self-heating of the grain.
Referring to
When dT is the difference between the ambient air and the temperature of the grain even though the ambient air EMC is within the target range, if the temperature of the ambient or heated air is, for example, more than 10 degrees F. above the temperature of the grain, the fan would not run. This is in an effort to avoid drastically changing grain temperature during one abnormal day. This check will be done whether heating, cooling, or using ambient air.
Similarly, when dT is the difference in temperature of the grain over a predetermined period resulting from operating the fan, or fan and heater, then for example, if the grain temperature increases more than 10 degrees F. over a 24 hour period, the fan, heater, or both would cease running or return to some minimal state. Again, this is in an effort to avoid drastically changing grain temperature during one abnormal day, and could be done whether heating, cooling, or using ambient air.
dT can also be the temperature difference between the ambient air and the heated air (i.e., the amount of temperature change to the air caused by the heater or cooler). For example, if it is early in the drying process and there is plenty of time left to accomplish the drying target, the controller can be set to only heat/cool the air up to, for example, +/−3 degrees F. to achieve the desired EMC. If the proper conditions for drying do not occur often enough and there is still a significant amount of drying needed, then the limits can be opened up to allow, for example, +/−7 degrees F. or more heating cooling to occur. Similarly, each of the various temperature differential limits discussed above may be set wider to achieve more full-speed run time. Again, each of the various dT ranges or limits can be used alone or in any combination.
The center and right paths of
Referring to
Referring to
Examples of various equations or calculations that the controller may use in the processes are provided below.
1. Using (Ambient Temp+Fan Temp Increase) and RH to Find EMC
ASAE D245.5 Moisture Relationships of Plant-based Agricultural Products
6.a RH=1−exp[−A(T+C)(MCD)̂B]
6.b RH=exp[(−A/(T+C)exp(−B(MCD))]
2. Convert to Moisture content on a wet basis
Typically, in the grain industry, moisture content is discussed as MCw(Moisture content on a Wet Basis)
MC
w=100(MCD/(100+MCD))
Equilibrium Moisture content=MCw=EQM=EMC
In the flowchart, we abbreviated Equilibrium Moisture content as EQM. The industry accepted abbreviation is EMC. We will have used both EMC and EQM interchangeably.
3. Set Limits on EMC of Plenum Air
In this example without a heater, the upper and lower EMC limits within which the fan operates at full speed are set. The plenum air can be measured to insure it is within a certain number of degrees of the grain temp.
Outside those limits, the fan can run at a reduced/minimum CFM or fan speed.
3. Set limits on EMC of plenum air
If the EMC is within the upper and lower EMC limits, and air temp is within set degrees of grain temperature, we run the fan.
If EMC is above target, heat can be added to raise temp and lower RH of the air. If the EMC of unheated plenum air is 17.0%, heat can be added to bring EMC down to 15%. Because of the nature of equations 6.a and 6.b, it is difficult, but possible to directly solve for the ΔT that the heater needs to add. Alternatively, determining the amount of heat/degrees to add can be done in one of two ways.
The equation is as follows.
Both methods here could work equally well; however, the first enables the controller to determine how much T will be needed without actually heating the air and/or running the fan. This may be particularly desirable if the heat input required exceeds the capacity of the heater or if the temperature increase in degrees exceeds the heat/cool degree limits that were set. This above paragraph summarizes condition B from the flow chart. If the T increase required exceeds the set limit, we will end up at condition H where fan speed will be set at minimum CFM and heater will maintain temperature required to achieve desired EMC.
Back at condition B, if the heat demand from the heater exceeds that which the heater can output, we will instead arrive at condition C.
In both of these scenarios, if we determine that the heater cannot output the required heat, our next step will be to reduce fan speed. The fan speed will be reduced until heater output is sufficient to achieve proper EMC.
Keep in mind, for all these scenarios we can always be checking that the plenum air temperature is within a set number of degrees of the grain temperature. If it is outside the set range, again, the fan can be operated at the minimum airflow setting.
The conditions noted above are shown in the chart below.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
This application claims the benefit of U.S. Provisional Application No. 62/010229, filed on Jun. 10, 2014. The entire disclosure of the above application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62010229 | Jun 2014 | US |
