Abstract:
A grain dryer is provided with a housing, and a hot air source connected to the housing so as to dry grain in the housing. A rehydration source is connected to the housing to add moisture, in the form of steam or hot water, to grain which is over-dried. A conveyor moves the grain through the housing during the drying and rehydration processes.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Three general types of grain drying systems are known in the art. The first system is a batch operation which dries a fixed quantity or volume of grain in a single batch in a dryer, and then discharges the dried grain batch before introducing a new batch of grain for drying. A second type of grain dryer is a vertical or gravity feed dryer, wherein the grain flows downwardly through a housing while being exposed to hot air so as to dry the grain. The third type of dryer is a horizontal dryer, wherein the grain is carried by a conveyor through a housing and dried therein by the application of hot air. Each system has certain benefits over the other systems.  
         [0002]     One problem associated with all three systems is over-drying of the grain. Normally, it is desirable to maintain a certain moisture level in the grain, depending upon the type of grain, for both storage and selling purposes. For example, an optimal percentage moisture for soybean is 13% by weight per bushel. If the grain resides in the dryer too long, or the dryer is too hot, the grain will become too dry. Also grain may be too dry coming in from the field.  
         [0003]     Accordingly, a primary objective of the present invention is the provision of a grain dryer having the ability to rehydrate grain which has been over-dried or is too dry coming in from the field.  
         [0004]     Another objective of the present invention is the provision of a grain dryer which can selectively supply steam or hot water to the grain so as to control the moisture content of the dried grain.  
         [0005]     Another objective of the present invention is the provision of a method of drying grain which includes rehydration of the grain if the dryness drops below a preset value.  
         [0006]     Still another objective of the present invention is the provision of an improved horizontal grain dryer.  
         [0007]     A further objective of the present invention is the provision of a portable grain dryer.  
         [0008]     These and other objectives become apparent from the following description of the invention.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     A grain dryer is provided with a housing, with a source of hot air operatively connected to the housing to dry grain within the housing. In a preferred embodiment, the grain is continuously moved through the housing on a conveyor. The dryer includes a rehydration source operatively connected to the housing to add moisture to over-dried grain.  
         [0010]     The grain drying method comprises moving grain into the housing, introducing hot air into the housing to dry the grain, measuring the moisture content of the dried grain, and adding moisture to the dried grain if the measured moisture content is less than a predetermined value. The measured moisture is fed back into a PLC control system, which in turn controls heat and grain flow in the dryer. The grain is then discharged from the housing. The method may also include the application of a treatment, such as an insecticide or fungicide, to the grain within the housing prior to discharge. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic view showing one embodiment of the grain dryer of the present invention having a belt conveyor.  
         [0012]      FIG. 2  is a schematic view showing how a grain dryer similar to that shown in  FIG. 1  is easily mounted on a flatbed truck so as to be portable.  
         [0013]      FIG. 3  is a schematic view showing another embodiment of a grain dryer of the present invention having a conveyor auger. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     The grain drying system of the present invention is generally designated in the drawings by the reference numeral  10 . The dryer  10  generally includes a housing  12  with air inlet plenums  14  and air outlet or exhaust plenums  16 . In  FIG. 1 , the inlet plenums  14  are shown to be on the bottom of the housing  12 , while the outlet plenums  16  are shown to be on the top of the housing  12 . It is understood that the arrangement of these plenums may be modified or reversed without departing from the scope of the present invention. Also, the number of inlet and outlet plenums may be varied, with one or more inlet and outlet plenums. An air inlet duct or line  18  extends from a blower or fan  20 , through a heater  22  and is connected to the inlet plenums  14 . An air outlet duct  24  extends from the outlet plenums  16  and includes an exhaust blower or fan  26 . One or both of the blowers  20 ,  26  may be used. A negative pressure is preferably maintained in the housing  12 .  
         [0015]     In a preferred embodiment of the invention, the dryer  10  is horizontal and a belt conveyor  28  extends substantially along the length of the housing  12 . Preferably, the belt is perforated. The belt conveyor  28  is adapted to carry grain through the housing for drying by the hot air. The housing  12  includes a product inlet chute  30  at one end and a product discharge chute  32  at the other end. The chute  30  is connected to an adjustable product slide gate, which is controlled manually or via a PLC so as to set and maintain grain bed depth inside the dryer. A product feed hopper  34  is provided adjacent the inlet chute  30 . A receiving bin or hopper  36  is provided adjacent the discharge chute  32 . As shown in  FIG. 1 , a conveyor  38  resides between the discharge chute  32  and the receiving bin  36  so as to carry dried grain from the housing  12  to the receiving bin  36 .  
         [0016]     The dryer  10  also includes a rehydration system which is used in the event that the grain becomes over-dried. More particularly, the rehydration system includes a water tank  40  and a pump  42  connected to a water supply line  44 . The water supply line  44  terminates in or adjacent to the air inlet plenums  14  so as to supply steam or hot water to the grain within the housing  12 . Preferably, the water supply line  44  includes one or more spray nozzles for applying the steam or hot water to the grain. Also, the spray nozzles are preferably located in the downstream path of the housing  12 . Sensors (not shown) are provided in the housing to determine the moisture content of the grain. If the moisture content falls below a pre-set value, the pump  42  is actuated so as to apply steam or hot water to the over-dried grain.  
         [0017]      FIG. 2  shows a dryer  10 A similar to that shown in  FIG. 1 . The dryer  10 A shows an increased number of smaller air inlet plenums  14 A and air outlet plenums  16 A. The dryer  10 A is mounted on a flatbed trailer  46 , so as to be portable. The dryer  10 A functions similarly to the dryer  10 , described above.  
         [0018]      FIG. 3  shows an alternative embodiment of a dryer  50 . The dryer  50  includes a housing  52  with an air inlet plenum  54  and an air outlet or exhaust plenum  56 . An air inlet duct  58  extends between a blower  60  and the inlet plenums  54 , with a heater  62  disposed in the duct  58 . An air outlet duct  64  extends from the exhaust plenum  56  to direct air from the housing  52 . An exhaust blower  66  facilitates the drawing of air from the housing  52 .  
         [0019]     The housing  52  includes an auger conveyor  68  extending therethrough. A grain inlet chute  70  is provided at one end of the housing  62 , with a grain outlet chute  72  being located at the opposite end of the housing  52 .  
         [0020]     A grain feed hopper  74  directs product into the inlet chute  70  for passage through the housing  52 . As shown in  FIG. 3 , as an option, the air outlet duct  64  may direct air into the feed hopper  74  so as to preheat the grain.  
         [0021]     A grain receiving bin similar to that described with respect to  FIG. 1  is provided adjacent the grain outlet chute, but is not shown in  FIG. 3 .  
         [0022]     The dryer  50  also includes the rehydration system, similar to the dryer  10 . More particularly, the rehydration system for the dryer  50  includes a water tank  76 , a pump  78 , and a supply line  80 . The supply line  80  extends into the heater  62  of the dryer  50 . The supply line  80  terminates in or adjacent to the air inlet plenum  54 , preferably in the downstream half of the dryer  50 . One or more spray nozzles may be provided on the terminal end of the supply line  80  so as to apply steam or hot water to over-dried grain carried by the auger conveyor  68 . One or more sensors are provided in the housing  52  to detect the moisture content of the grain. Preferably, the sensors are located at least at the midpoint of the housing  52 , but may be located elsewhere along the length of the housing  52 .  
         [0023]     The grain drying method of the present invention includes the steps of moving the grain into the housing  12 ,  52  and supplying heated drying air via the air inlet duct  24 ,  64  and the inlet plenums  14 ,  54 . The hot air passes through the grain so as to dry the grain. The moisture content, or dryness of the grain is measured with the sensors, at least at the midpoint of the housing  12 ,  52 . If the moisture content is below a predetermined, desirable value, the pump  42 ,  78  is actuated to supply steam or hot water to the over-dried grain within the housing  12 ,  52 . The grain is then discharged via the discharge chute  32 ,  72 .  
         [0024]     In the preferred embodiment, the dryers  10 ,  50  are continuous horizontal dryers. It is understood that the rehydration system of the present invention can also be utilized on batch dryers or gravity dryers, so as to rehydrate over-dried grain. In each embodiment, insecticide, pesticide and/or fungicide treatment may be applied to the grain in the dryer, such as by fumigation.  
         [0025]     The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.