Patent Publication Number: US-10767926-B2

Title: Mixed-flow grain dryer with cross-flow vacuum cool heat recovery system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of U.S. Utility application Ser. No. 15/131,865 which was filed on Apr. 18, 2016, as well as published on Oct. 19, 2017 as Pub. No. 2017/0299263, the entirety of which is incorporated herein fully by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates to generally to the grain handling, grain storage and grain conditioning arts. More specifically and without limitation, this disclosure relates to the grain drying arts. More specifically and without limitation, this disclosure relates to an improved grain dryer and grain drying system known as a mixed-flow grain dryer with a cross-flow vacuum cool heat recovery system. 
     BACKGROUND OF THE INVENTION 
     Grain dryers are old and well known in the art. Grain dryers are commonly used to dry various types of grain, such as corn, wheat, rice, sorghum, and the like, so as to allow the grain to be stored in bulk, such as in a grain bin, tote or other bulk grain storage device, for extended periods of time. If grain is stored in bulk with a moisture content that is too high, the grain will spoil. As such, particular care is taken to ensure that grain that is to be stored does not too high a moisture content. 
     Optimally drying grain is a particularly complex, difficult and delicate matter. Care must be taken to ensure that the grain is dried enough to have a low enough moisture content to ensure that it does not spoil while being stored. However it is also undesirable to overly dry grain. 
     Overly drying grain is wasteful in various ways. Overly drying grain consumes additional and unnecessary fuel used to dry the grain beyond the moisture content level that is needed for stable storage. Overly drying grain often takes additional and unnecessary time to dry the grain beyond the moisture content level that is needed for stable storage. Overly drying grain can damage the grain by causing it to be burned, cracked or otherwise damaged, which can reduce the value of the grain. Overly drying grain can reduce the test weight of the grain thereby causing a deduction in the price of the grain when it is sold. For these and other reasons, overly drying grain is undesirable. 
     As such, optimally drying grain requires striking a delicate balance between overly drying grain on one side, and not drying grain enough on the other side. 
     Various configurations of grain dryers have been developed to help facilitate efficient grain drying. However all of the presently available grain dryers suffer from various disadvantages. 
     Cross-Flow Grain Dryers: 
     One form of a grain dryer is what is known as a cross-flow grain dryer. Cross-flow grain dryers are known for having a pair of grain columns on each side that are formed by perforated screens. A plenum, or open space, is positioned between the grain columns. Wet grain is loaded into the grain columns using a loading system. The wet grain travels down the grain columns under the force of gravity, between the perforated screens. As the wet grain travels down the grain columns, between the perforated screens, heated air is blown into the plenum. This heated air flows outward from the plenum and through the columns of grain. As the heated air blows through the columns of grain, the heated air warms the grain and carries away moisture from the grain. Dry grain is unloaded from the grain columns using an unloading system. In this way, the grain is dried. 
     Cross-flow grain dryers suffer from many disadvantages. One disadvantage of cross-flow grain dryers is that they are relatively harsh on grain. This is because the grain toward the interior side of the grain columns is often exposed to high levels of heat which can cause the interior-positioned grain to crack, burn, and/or be overly dried. Another disadvantage of cross-flow grain dryers is that the grain within the grain columns tends to dry in an uneven manner. That is, the grain positioned toward the interior side of the grain column has a tendency to be dried more than the grain positioned toward the exterior side of the grain column. Another disadvantage of cross-flow is that they tend to require relatively high operating pressures and high air-flow. Another disadvantage of cross-flow grain dryers is that they tend to consume a lot of fuel, or said another way they are energy inefficient. Another disadvantage of cross-flow grain dryers is the screens tend to get covered and plugged with fines from the grain which affects the operational characteristics of the grain dryer as well as requires periodic cleaning. 
     For these and other reasons, cross-flow grain dryers suffer from many disadvantages and are undesirable to use. 
     Mixed-Flow Grain Dryers: 
     One form of a grain dryer is what is known as a mixed-flow grain dryer. Mixed-flow grain dryers are known for having a pair of grain columns on each side that have a plurality inlet ducts and exhaust ducts that extend across the grain column. A plenum, or open space, is positioned between the grain columns. Wet grain is loaded into the grain columns using a loading system. The wet grain travels down the grain columns under the force of gravity. As the wet grain travels down the grain columns, between the interior wall and exterior wall of the grain columns, heated air is blown into the plenum. This heated air flows into the inlet ducts through the columns of grain and out the exhaust ducts. As the heated air blows through the columns of grain, the heated air warms the grain and carries away moisture from the grain. Dry grain is unloaded from the lower end of each of the grain columns using an unloading system. In this way, the grain is dried. 
     Mixed-flow grain dryers suffer from many disadvantages. One disadvantage of mixed-flow grain dryers is that they do not allow for heat recovery and as such they waste energy and consume unnecessary fuel. Another disadvantage of mixed-flow grain dryers is that each column requires its own unload system. 
     For these and other reasons, mixed-flow grain dryers suffer from many disadvantages and are undesirable to use. 
     Therefore, for all the reasons stated above, and the reasons stated below, there is a need in the art for a grain drying system that improves upon the state of the art. 
     Thus, it is a primary objective of the disclosure to provide a grain dryer system that improves upon the state of the art. 
     Another object of the disclosure is to provide a grain dryer system that is efficient to use. 
     Yet another object of the disclosure is to provide a grain dryer system that facilitates heat recovery. 
     Another object of the disclosure is to provide a grain dryer system that reduces fuel consumption. 
     Yet another object of the disclosure is to provide a grain dryer system that is gentle on grain. 
     Another object of the disclosure is to provide a grain dryer system does not damage grain when drying. 
     Yet another object of the disclosure is to provide a grain dryer system that does not overly dry grain. 
     Another object of the disclosure is to provide a grain dryer system that facilitates cooling of grain before it is discharged. 
     Yet another object of the disclosure is to provide a grain dryer system that evenly dries grain. 
     Another object of the disclosure is to provide a grain dryer system that does not have variability of grain quality across the grain column. 
     Yet another object of the disclosure is to provide a grain dryer system that does not have variability of moisture across the grain column. 
     Another object of the disclosure is to provide a grain dryer system that can be precisely controlled. 
     Yet another object of the disclosure is to provide a grain dryer system that provides optimum results. 
     Another object of the disclosure is to provide a grain dryer system that facilitates unloading of grain from the dryer at a single point. 
     Yet another object of the disclosure is to provide a grain dryer system that is relatively compact. 
     Another object of the disclosure is to provide a grain dryer system that is relatively inexpensive. 
     Yet another object of the disclosure is to provide a grain dryer system that can be used with all kinds of grain. 
     Another object of the disclosure is to provide a grain dryer system that that minimizes maintenance. 
     Yet another object of the disclosure is to provide a grain dryer system that requires less cleaning. 
     Another object of the disclosure is to provide a grain dryer system that is cleaner to use than prior art systems. 
     Yet another object of the disclosure is to provide a grain dryer system that is safe to use. 
     Another object of the disclosure is to provide a grain dryer system that reduces the potential for a fire. 
     Yet another object of the disclosure is to provide a grain dryer system that requires less air pressure. 
     Another object of the disclosure is to provide a grain dryer system that requires less air flow. 
     Yet another object of the disclosure is to provide a grain dryer system that provides improved grain quality. 
     Another object of the disclosure is to provide a grain dryer system that is easy to use. 
     Yet another object of the disclosure is to provide a grain dryer system that has a robust design. 
     Another object of the disclosure is to provide a grain dryer system that is high quality. 
     Yet another object of the disclosure is to provide a grain dryer system that incorporates the benefits of mixed-flow grain dying with the benefits of cross-flow vacuum cooling. 
     Another object of the disclosure is to provide a grain dryer system that provides a unique solution to grain drying needs. 
     SUMMARY OF THE DISCLOSURE 
     An improved mixed-flow grain dryer with cross-flow vacuum cool heat recovery system is presented. The grain dryer system includes a loading system positioned at its upper end and an unloading system positioned at its lower end. Once loaded into the dryer, grain passes through the grain dryer under the force of gravity in a grain column positioned on each side of a centrally positioned plenum. A wet holding section is positioned at the upper end of the grain dryer and receives wet grain from the loading system. The wet holding section directs the grain into the grain columns. A heating section is positioned just below the wet holding section and receives wet grain from the wet grain section. The grain column of the heating section is formed by a solid interior wall and a solid exterior wall. A plurality of inlet ducts is connected to openings in the interior wall that facilitate air flow into the grain column from the heated and pressurized heat plenum. A plurality of exhaust ducts is connected to openings in the exterior wall that facilitate air flow out of the grain column. In this way, air flows from the heated and pressurized heat plenum, through the openings in the interior wall and into the connected inlet duct, through the grain column, into the exhaust ducts and out the connected openings in the exterior wall. In this way, the heated and pressurized air in the heat plenum gently flows through the grain column thereby heating and drying the grain. A tempering section is positioned just below the heating section and receives heated and dried grain from the heating section. The tempering section has a solid interior wall and a solid exterior wall that prevents air flow through the grain column in the tempering section. A cooling section is positioned just below the tempering section and receives heated and dried grain from the tempering section. The grain column of the cooling section is formed by a perforated interior wall and a perforated exterior wall. Air is pulled through the perforated exterior wall, through the grain column and through the perforated interior wall and into the cool plenum under vacuum formed by a fan connected to the cool plenum of the cooling section. As the air is pulled through the grain column of the cooling section, the grain is cooled and the air is heated. An unloading system is positioned just below the cooling section and receives cooled and dried grain from the cooling section. The unloading system unloads the grain from the drain dryer system. A fan having adjustable louvers is connected to the cool plenum of the cooling section. The fan pulls air through the grain column of the cooling section which heats the air while cooling the grain. This heated air is heated further by a heater. This heated air is then blown into the heat plenum thereby pressurizing the heat plenum. In this way, a mixed-flow grain dryer with cross-flow vacuum cool is presented that harnesses the benefits of mixed-flow heating and cross-flow vacuum cooling that provides gentler drying and increased efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view of a mixed-flow grain dryer with cross-flow vacuum cool heat recovery system. 
         FIG. 2  is a perspective sectional view of a mixed-flow grain dryer with cross-flow vacuum cool heat recovery system. 
         FIG. 3  is a perspective view of a mixed-flow grain dryer with cross-flow vacuum cool heat recovery system. 
         FIG. 4  is a close up view of the upper end of  FIG. 1 . 
         FIG. 5  is a close up view of the middle portion of  FIG. 1 , the view showing the mixed-flow heating section. 
         FIG. 6  is a close up view of the upper portion of  FIG. 5 , the view showing the upper portion of the mixed-flow heating section. 
         FIG. 7  is a close up view of the lower portion of  FIG. 5 , the view showing the lower portion of the mixed-flow heating section. 
         FIG. 8  is a close up view of the lower portion of  FIG. 1 . 
         FIG. 9  is a close up view of the lower portion of  FIG. 8 . 
         FIG. 10  is a close up view of the upper portion of  FIG. 2 . 
         FIG. 11  is a close up view of the middle portion of  FIG. 2 . 
         FIG. 12  is a close up view of the lower portion of  FIG. 2 . 
         FIG. 13  is a close up view of the middle portion of the left side of  FIG. 2 . 
         FIG. 14  is a close up view of the middle portion of the right side of  FIG. 2 . 
         FIG. 15  is a close up view of the upper portion of  FIG. 3 . 
         FIG. 16  is a close up view of the upper right portion of  FIG. 3 . 
         FIG. 17  is a close up view of the middle left portion of  FIG. 3 . 
         FIG. 18  is a close up view of the lower left portion of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that mechanical, procedural, and other changes may be made without departing from the spirit and scope of the disclosure(s). The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the disclosure(s) is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     As used herein, the terminology such as vertical, horizontal, top, bottom, front, back, end, sides, left, right, and the like are referenced according to the views, pieces, parts, components and figures presented. It should be understood, however, that the terms are used only for purposes of description, and are not intended to be used as limitations. Accordingly, orientation of an object or a combination of objects may change without departing from the scope of the disclosure. 
     System: 
     With reference to the figures, a mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10 , or simply system  10 , is presented that extends vertically from an upper end  12  to a lower end  14 , extends a width between opposing sides  16 , and extends a depth between an opposing forward end  18  and an opposing rearward end  20 . Mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  is formed of any suitable size, shape and design and is configured to gently and efficiently cool grain while providing a single loading point, a single unloading point and heat recovery. In the arrangement shown, as one example, system  10  includes a pair of grain columns  22  having an exterior wall  24  and an interior wall  26  separated by a plenum  28 , a loading system  30 , a wet hold section  32 , a mixed-flow heating section  34 , a tempering section  36 , a cross-flow cooling section  38 , an unloading system  40 , an air handling system  42  having a fan system  44 , a heating system  46  and louvers  48 , and a support system  50 , among other components, structures and features as is further described herein. 
     In the arrangement shown, as one example, to facilitate even air flow across the system  10 , the system  10  is generally symmetric along a vertically extending line that runs through the center of the system  10  between opposing sides  16 . 
     Grain Columns: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes at least one grain column  22 . Grain columns  22  are formed of any suitable size, shape and design and are configured to hold grain therein while the grain moves vertically through the system  10  under the force of gravity while being exposed to heating of the mixed-flow heating section  34  and cooling of the cross-flow cooling section  38 . 
     In the arrangement shown, as one example system  10  includes a pair of grain columns  22 , with one grain column  22  positioned on each side  16  of system  10 . In the arrangement shown, as one example, grain columns  22  extend laterally a width and are bounded on one side by exterior wall  24  and bounded on the opposite side by interior wall  26 . Grain columns  22  are bounded at their ends by end walls  52 . The interior sides of grain columns  22  are separated by plenum  28 . The exterior sides of grain columns  22  connect with the atmosphere surrounding system  10 . 
     In the arrangement shown, as one example, grain columns  22  extend vertically from the lower end of loading system  30  to the upper end of unloading system  40  in a continuous and uninterrupted manner. In this way, when grain enters one of the two of the opposing grain columns  22 , the grain travels vertically through the grain column  22  from its upper end to its lower end under the force of gravity while being exposed to the air flow of mixed-flow heating section  34  and cross-flow cooling section  38 . 
     In the arrangement shown, as one example, the grain columns  22  are wider at the mixed-flow heating section  34  than they are at the cross-flow cooling section  38 . In the arrangement shown, as one example, the width of grain columns  22  remains generally constant and consistent throughout the length of the heating section  34 . In the arrangement shown, as one example, the width of grain columns  22  remains generally constant throughout the length of the cooling section  38 , albeit with a turn or angle positioned within the cooling section  38 . In the arrangement shown, as one example, tempering section  36  narrows the width of the grain columns  22  by angling the interior wall  26  and exterior wall  24  toward one another such that tempering section  36  transitions the width of the grain column  22  from the wider heating section  34  to the narrower cooling section  38 . 
     While two opposing grain columns  22  are shown in use with system  10 , any number of grain columns  22  are hereby contemplated for use such as one, two, three, four, five, six or more. As any other shape or configuration of grain columns  22 . 
     Plenum: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a plenum  28 . Plenum  28  is formed of any suitable size, shape and design and is configured to provide a space between grain columns  22  so as to facilitate airflow through grain columns  22 . 
     In the arrangement shown, as one example plenum  28  is a generally centrally positioned space that extends between the opposing interior walls  26  of grain columns  22  and extends between the interior surfaces of end walls  52 . In the arrangement shown, as one example, the upper end of plenum  28  is bounded by the angled lower walls of wet hold section  32 . In the arrangement shown, as one example, the lower end of plenum  28  is bounded by the angled upper walls  56  of unloading system  40  and/or divider  58  positioned adjacent upper walls  56  of unloading system  40 . In this way, plenum  28  extends the entire interior height of system  10 . 
     In the arrangement shown, as one example, a divider  60  extends across plenum  28 . Divider  60  separates plenum  28  into a heat plenum  62 , which is positioned above divider  60 , and a cool plenum  64 , which is positioned below divider  60 . 
     Heat Plenum: 
     Heat plenum  62  is formed of any suitable size, shape and design and is configured to receive heated air from air handling system  42  which is blown outward through the grain column  22  of the heating section  34 . In the arrangement shown, as one example, heat plenum  62  is bounded on its lower end by divider  60 , is bounded on its exterior sides by interior walls  26  of heating section  34 , is bounded on its upper end by lower walls  54  of wet hold section  32 , and is bounded at its ends by interior surfaces of end walls  52 . In the arrangement shown, as one example, the width of heat plenum  62  remains generally constant from its upper end to its lower end, albeit with a peak at its upper end formed by the angled lower walls  54  of wet hold section  32 . 
     In the arrangement shown, as one example, a plurality of structural members  66  extend across heat plenum  62 . Structural members  66  are formed of any suitable size, shape and design and are configured to connect the opposing sides of system  10  so as to provide structural support and rigidity and strength to the large and tall system  10 . In the arrangement shown, as one example, a plurality of structural members  66  extend between opposing interior walls  26  of heat plenum  62 . More specifically, in the arrangement shown, three sets of three structural members  66  are placed in an X-formation with a centrally extending structural member  66  extending through the center of each X-formation. In this way structural members  66  bridge the width of heat plenum  62  thereby connecting opposing interior sides of heat plenum  62  while not inhibiting air flow through heat plenum  62 . Any other configuration of structural members  66  is hereby contemplated for use. 
     In the arrangement shown, as one example, heat plenum  62  is connected to and receives output from air handling system  42 , or more specifically fan system  44  and heating system  46 . In this way, heat plenum  62  receives heated and pressurized air from air handling system  42 . This heated and pressurized air is pushed or blown outward through the grain column of mixed-flow heating section  34  as is further described herein. 
     Cool Plenum: 
     Cool plenum  64  is formed of any suitable size, shape and design and is configured to receive vacuum from air handling system  42  which causes air to be pulled through the grain column  22  of the cooling section  38  and into cool plenum  64 . In the arrangement shown, as one example, cool plenum  64  is bounded on its upper end by divider  60 , is bounded on its exterior sides by interior walls  26  of cooling section  38 , is bounded on its lower end by upper walls  56  of unloading system  40  as well as divider  58 , and is bounded at its ends by interior surfaces of end walls  52 . In the arrangement shown, as one example, the width of cool plenum  64  varies as the interior wall  26  angles outward at the upper end of tempering section  36 , extends vertically at the upper end of cooling section  38 , angles inward at the lower end of cooling section  38 , and is bounded at its lower end by the upper surface of divider  58  that extends in generally parallel spaced relation to divider  60 . 
     In the arrangement shown, as one example, cool plenum  64  does not include any structural members  66  that extend across the cool plenum  64 . In an alternative arrangement, cool plenum  64  includes one or more structural members  66  that extend across cool plenum  64  similar to the heat plenum  62 . 
     In the arrangement shown, as one example, cool plenum  64  is connected to the input of air handling system  42 , or more specifically fan system  44 . In this way, cool plenum  64  feeds air into air handling system  42  and therefore cool plenum  64  is under vacuum or negative pressure. The vacuum or negative pressure of cool plenum  64  causes air to be drawn, pulled or sucked through the grain column of cross-flow cooling section  38  as is further described herein. 
     Loading System: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a loading system  30 . Loading system  30  is formed of any suitable size, shape and design and is configured to facilitate loading of wet grain into system  10 . 
     Any form of a grain loading system is hereby contemplated for use as loading system  30 . In the arrangement shown, as one example loading system  30  is an auger system having an input  68 , that receives grain from a chute or other device. A shaft  70  with flighting  71  extends across the upper end of system  10 . The shaft  70  with flighting  71  is connected to a motor  72  by a pulley and belt system and is configured to rotate the shaft  70  with flighting  71 . A housing  74  is positioned over and around the shaft  70  with flighting  71  so as to constrain the grain moved by the shaft  70  with flighting  71 . In the arrangement shown, housing  74  is generally square or rectangular with an open lower end that connects to wet hold section  32  so as to facilitate the transfer of grain from the loading system  30  to the wet hold section  32 . 
     In operation, as motor  72  operates, while grain is loaded into loading system  30 , the shaft  70  with flighting  71  rotates thereby moving the grain across the upper end of system  10  evenly distributing wet grain across the upper end of system  10 , or more specifically across the upper end of wet hold section  32 . In the arrangement shown, as one example, a sensor  76  is positioned adjacent one end of loading system  30 , or more specifically adjacent one end of shaft  70  with flighting  71 . When loading system  30  and/or wet hold section  32  is filled with grain, sensor  76  detects this filled condition. This information is then used to stop the rotation of loading system  30  and/or to stop loading grain into input  68  and/or to shut down or stop any other component of the system. Once the grain is consumed from the area around sensor  76 , loading system  30  may again resume operation and the loading of grain. In the arrangement shown, as one example, one or more sensors  76  are positioned on an end of shaft  70  with flighting  71  opposite input  68 . 
     While in the arrangement shown, only a single auger, or shaft  70  with flighting  71  is used, it is hereby contemplated that multiple augers or multiple shafts  70  with flighting  71  are used in loading system  30 . Also, while in the arrangement shown, the input  68  is positioned adjacent one end of the loading system  30  and the sensor  76  is positioned adjacent the opposite end of the loading system  30 , it is hereby contemplated that grain may be loaded at the middle of loading system  30  and moved outward to the ends using shaft  70  with flighting  71 . Alternatively, a gravity fill system is hereby contemplated for use. Alternatively, a belt, a conveyor, a paddle sweep and/or a drag chain system is hereby contemplated for use as loading system  30 . Any other structure or configuration of a system for loading grain is hereby contemplated for use as loading system  30 . 
     Wet Hold Section: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a wet hold section  32 . Wet hold section  32  is formed of any suitable size, shape and design and is configured to hold and stage a quantity of wet grain prior to the grain passing through the grain columns  22 . 
     In the arrangement shown, as one example, wet hold section  32  connects at its upper end to the lower end of loading system  30 , and connects at its lower end to the upper end of mixed-flow heating section  34 . In the arrangement shown, as one example, wet hold section  32  starts the formation of grain columns  22 . 
     In the arrangement shown, as one example, the upper side of wet hold section  32  includes upper sidewalls  78  and upper end walls  80  that enclose the upper end of wet hold section  32 . In the arrangement shown, as one example, upper sidewalls  78  connect at their upper end to the lower end of the sides of housing  74  of loading system  30 , and upper sidewalls  78  connect at their lower end to the upper end of exterior walls  24 . Similarly, in the arrangement shown, as one example, upper end walls  80  connect at their upper end to the lower end of the ends of housing  74  of loading system  30 , and upper end walls  80  connect at their lower end to the upper end of end walls  52 . In the arrangement shown, as one example, upper side walls  78  and upper end walls  80  extend downward at an angle as they extend outward thereby forming a sloped roof at the upper end of system  10 . 
     In the arrangement shown, as one example, a door  82  is positioned in one or both upper end walls  80 . Door  82  is formed of any suitable size, shape and design and is configured to provide access to the hollow interior of wet hold section  32  so as to facilitate repair and cleaning of the components of wet hold section  32 . Additional doors  82  may be placed in other parts wet hold section  32 , such as upper side walls  78 , or for that matter in any other part of system  10  such as the interior wall  26  of grain columns  22  as well as any other place or position. 
     In the arrangement shown, as one example, the lower side of wet hold section  32  includes lower walls  54  that enclose the lower end of wet hold section  32 . In the arrangement shown, as one example, lower walls  54  connect at their upper end to one another thereby forming a peak at the approximate upper center end of plenum  28 . This peak divides or directs the grain held within wet hold section  32  into one or the other grain columns  22 . Similarly, in the arrangement shown, as one example, lower walls  54  connect at their lower end to the upper end of interior wall  26 . 
     As grain moves through wet hold section  32  from loading system  30  and into grain columns  22 , grain is directed by the angling of the upper side walls  78  and upper end walls  80  on the upper side, and the lower walls  54  on the lower side. The volumetric holding capacity of wet hold section  32  ensures that an adequate buffer of wet grain is on hand at all times to ensure the grain columns  22  are always filled while accommodating loading variability during use. In this way, wet hold section  32  stages grain for drying in grain columns  22  as well as directs grain into grain columns  22  under the force of gravity. To be clear, in a manner of speaking, grain columns  22  begin in wet hold section  32  between upper side walls  78  and lower walls  54 . 
     Mixed-Flow Heating Section: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a mixed-flow heating section  34 . Mixed-flow heating section  34  is formed of any suitable size, shape and design and is configured to facilitate drying of grain in grain columns  22  in a gentle and efficient manner. 
     In the arrangement shown, as one example mixed-flow heating section  34  extends vertically from its upper end  84 , at the lower end of wet hold section  32 , to its lower end  86 , at the upper end of tempering section  36 . Mixed-flow heating section  34  is defined at its outward sides by the exterior surface of exterior walls  24 . Mixed-flow heating section  34  is defined at its outward ends by the exterior surface of end walls  52 . 
     In the arrangement shown, as one example, grain columns  22  extend through mixed-flow heating section  34  from its upper end  84  to its lower end  86 . More specifically, in the arrangement shown, as one example, grain columns  22  of heating section  34  have a generally consistent width and shape from upper end  84  to lower end  86 . That is, grain columns  22  of heating section  34  are defined at their outward sides by the interior surface of exterior walls  24  and at their inward sides by the interior surface of interior walls  26 , wherein exterior walls  24  and interior walls  26  extend in approximate parallel spaced relationship to one another from upper end  84  to lower end  86 . Similarly, grain columns  22  of heating section  34  are defined at their outward ends by the interior surface end walls  52 , wherein end walls  52  extend in approximate perpendicular relationship to exterior walls  24  and interior walls from upper end  84  to lower end  86 . In this way, grain columns  22  of heating section  34  are generally square or rectangular in shape. 
     In the arrangement shown, as one example, the interior ends of opposing grain columns  22  of mixed-flow heating section  34  are separated from one another by heat plenum  62  of plenum  28 . To provide enhanced strength and rigidity, a plurality of structural members  66  extend across heat plenum  62  in a crossing pattern thereby connecting one grain column  22  to the other grain column  22 . Heat plenum  62  receives heated and pressurized air from air handling system  42 . This heated and pressurized air received by heat plenum  62  passes through a series of inlet ducts  88 , through the grain in grain column  22 , and through a series of exhaust ducts  90 . 
     Inlet ducts  88  and exhaust ducts  90  may be formed of any suitable size, shape and design and are configured to allow the flow of heated air through the grain in grain column  22  of heating section  34  so as to facilitate gentle heating and drying of the grain. In the arrangement shown, as one example, when viewed from a side  16 , inlet ducts  88  and exhaust ducts  90  are generally triangular shaped members having a pair of opposing walls  92  that connect to one another at their upper end at a peak  94  and extend outward and downward from the peak  94  at an angle before terminating their lower ends. The lower ends of inlet ducts  88  and exhaust ducts  90  are open, thereby allowing for the free flow of air into the inlet ducts  88  and exhaust ducts  90  from their open lower end. 
     In one arrangement, the lower end of inlet ducts  88  and exhaust ducts  90  are completely open. This configuration of having an open lower end of inlet ducts  88  and exhaust ducts  90  is acceptable in many applications due to the manner in which grain moves through grain columns  22  under the force of gravity which prevents the grain from escaping through the open lower end of inlet ducts  88  and exhaust ducts  90 . In another arrangement the lower end of inlet ducts  88  and exhaust ducts  90  are covered by a screen, a perforated sheet or another component that allows air flow there through while preventing animals and birds from entering the grain column  22  and/or heat plenum  62  and/or preventing grain from escaping inlet ducts  88  and exhaust ducts  90 . 
     Inlet ducts  88  and exhaust ducts  90  extend a length between opposing ends. In the arrangement shown, as on example, inlet ducts  88  and exhaust ducts  90  extend approximately the width of grain column  22  of heating section  34 . In this way, the interior end of inlet ducts  88  and exhaust ducts  90  is positioned at, in or adjacent to the interior wall  26  of grain columns  22 . Similarly, the exterior end of inlet ducts  88  and exhaust ducts  90  is positioned at, in or adjacent to the exterior wall  24  of grain columns  22 . In the arrangement shown, as one example, the interior end of inlet ducts  88  and exhaust ducts  90  is connected to the interior wall  26  of grain columns  22 , and the exterior end of inlet ducts  88  and exhaust ducts  90  is connected to exterior wall  24 . In this way, the interior end and exterior end of inlet ducts  88  and exhaust ducts  90  are rigidly supported within grain column  22 . 
     In the arrangement shown, as one example, inlet ducts  88  and exhaust ducts  90  are arranged in rows or tiers  96  that extend from the forward end  18  of heating section  34  to the rearward end  20  of heating section  34  with each inlet duct  88  or exhaust duct  90  spaced from the inlet duct  88  or exhaust duct  90  on either side. In the arrangement shown, as one example, inlet ducts  88  are arranged in tiers  96 , and exhaust ducts  90  are arranged in tiers  96 . In the arrangement shown, as one example, heating section  34  is formed of alternating tiers  96  of inlet ducts  88  and tiers  96  of exhaust ducts  90 . Or, said another way, each tier  96  includes only inlet ducts  88  or exhaust ducts  90 , and each tier  96  of inlet ducts  88  has a tier  96  of exhaust ducts  90  above as well as below the tier  96  of inlet ducts  88 , and similarly, each tier  96  of exhaust ducts  90  has a tier  96  of inlet ducts  88  above as well as below the tier  96  of exhaust ducts  90 . 
     However, any other configuration or arrangement of inlet ducts  88  and exhaust ducts  90  is hereby contemplated for use such as tiers  96  having an alternating pattern of an inlet duct  88  next to an exhaust duct  90  or any other arrangement or configuration. 
     Also, in the arrangement shown, as one example, the tiers  96  of inlet ducts  88  and exhaust ducts  90  are laterally offset from one another. That is, the inlet ducts  88  are laterally offset from the exhaust ducts  90  of the adjacent tiers  96 . Or, said another way, inlet ducts  88  of one tier  96  are not positioned directly above or below the exhaust ducts  90  of adjacent tiers  96 . Instead, inlet ducts  88  of one tier  96  are positioned between the exhaust ducts  90  of vertically adjacent tiers  96 , and similarly exhaust ducts  90  of one tier  96  are positioned between the inlet ducts  88  of adjacent tiers  96 . This lateral offsetting of vertically adjacent inlet ducts  88  and exhaust ducts  90  helps to cause mixing air flow through the grain in grain column  22 . This lateral offsetting of vertically adjacent inlet ducts  88  and exhaust ducts  90  helps to cause the grain to move within grain column  22  as it travels vertically through the grain column  22  by engaging the offset inlet ducts  88  and exhaust ducts  90 . This mixing of the airflow as well as mixing of the grain in heat section  34  facilitates consistent and gentle drying of the grain. 
     In the arrangement shown, as one example, inlet ducts  88  have an open interior end that connects to heat plenum  62 . Or, said another way, the interior end of inlet ducts  88  connect to an opening in the interior wall  26 . In this way, the open interior end of inlet ducts  88  allow air flow from the pressurized heat plenum  62  and into the inlet ducts  88 . Then, due to the open lower end of inlet ducts  88  air passes through the open lower end of inlet ducts  88  and into the grain of grain column  22 . 
     Similarly, in the arrangement shown, as one example, exhaust ducts  90  have an open exterior end that connects to the atmosphere or vents outside of the system  10 . Or, said another way, the exterior end of exhaust ducts  90  connect to an opening in the exterior wall  24 . In this way, the open lower end of exhaust ducts  90  allows pressurized air flow from the grain column  22  to enter into the exhaust ducts  90 . Then, due to the open exterior end of exhaust ducts  90  air passes through the open exterior end of exhaust ducts  90  and into the atmosphere thereby carrying with it moisture from the heated grain. 
     In the arrangement shown, as one example, heating section  34  is formed by a plurality of panels  98  that form exterior wall  24  as well as interior wall  26 . Panels  98  may also be used for end wall  52  as well as other components of the system  10 . Each panel  98  includes a plurality of inlet ducts  88  and a plurality of exhaust ducts  90 . In the arrangement shown, as one example, each panel  98  includes a tier  96  of exhaust ducts  90  at the lower side of the panel  98  and a tier  96  of inlet ducts  88  at the upper side of the panel  98 . However the opposite arrangement is hereby contemplated for use. These panels  98  are then stacked on top of one another as well as connected to laterally adjacent and vertically adjacent panels  98  thereby forming the grain columns  22  of heat section  34  in a quick and easy and secure manner. 
     Also, in the arrangement shown, as one example, one tier  96  of exhaust ducts  90  are positioned adjacent the lower end of wet hold section  32 . Due to the inward sloping of upper side walls  78  of wet hold section  32 , the outer end of exhaust ducts  90  in wet hold section  32  protrude upward out of the exterior sides of upper side walls  78 . In the arrangement shown, as one example, mixed-flow heating section  34  is formed of panels  98  stacked six high and four across, each panel  98  having exhaust ducts  90  positioned at their lower end and inlet ducts  88  positioned at their upper end. 
     In the arrangement shown, the exterior walls  24 , interior walls  26  and end walls  52  of grain column  22  of mixed-flow heating section  34  are solid thereby preventing air flow through the exterior walls  24 , interior walls  26  and end walls  52  of grain column  22 . This is other than the openings in interior walls  26  that inlet ducts  88  connect to and the openings in exterior walls  24  that exterior ducts  90  connect to. 
     In the arrangement show, as one example, the lower end of mixed-flow heating section  34  connects to the upper end of tempering section  36 . The lower end of mixed-flow heating section  34  is enclosed by the upper surface of divider  60 . In the arrangement shown, a tier of exhaust ducts  90  are positioned a distance above the lower end  86  of heating section  34 . 
     Tempering Section: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a tempering section  36 . Tempering section  36  is formed of any suitable size, shape and design and is configured to facilitate the transition of grain from the mixed-flow heating section  34  to the cross-flow cooling section  38 . 
     In the arrangement shown, as one example tempering section  36  extends vertically from its upper end, at the lower end  86  of mixed-flow heating section  34 , to its lower end  100 , at the upper end of unloading system  40 . Tempering section  36  is defined at its outward sides by the exterior surface of exterior walls  24 . Tempering section  36  is defined at its outward ends by the exterior surface of end walls  52 . 
     In the arrangement shown, as one example, grain columns  22  extend through tempering section  36  from its upper end to its lower end. In the arrangement shown, as one example, grain columns  22  of tempering section  36  vary in width from their upper end to their lower end. That is, the width of the grain column  22  at the upper end of tempering section  36  is wider than the width of the grain column  22  at the lower end of tempering section  36 . This is because, due to the operational nature of the mixed-flow heating section  34 , the grain columns  22  are wider in the mixed-flow heating section  34  as compared to the grain columns  22  of the cross-flow cooling section  38 . This difference in the width of grain columns  22  between the mixed-flow heating section  34  and the cross-flow cooling section  38  causes the grain to remain in the grain column  22  of the mixed-flow heating section  34  longer than the grain remains in the grain column  22  of the cross-flow cooling section  38 . Or, said another way, the grain moves through the narrower grain columns  22  of the cross-flow cooling section  38  faster than the grain moves through the wider grain columns  22  of the mixed-flow heating section  34 . The speed at which the grain moves the grain columns  22  of the mixed-flow heating section  34  the cross-flow cooling section  38  is also varied by the height of these portions of the grain columns  22  as well as the speed at which the unloading system  40  operates. In this way, optimal operational performance may be achieved by varying the height of the various portions of the grain columns  22 , the width of the various portions of the grain columns  22 , the unload speed of the unloading system  40 , as well as other features such as the temperature of the air blown into the heat plenum  62 , the pressure applied by fan system  44  to both the cool plenum  64  and heat plenum  62 , the size, shape, position, density and configuration of the inlet ducts  88  and exhaust ducts  90  and the size, shape, density and configuration of the perforations in the exterior wall  24  and interior wall  26  of cross-flow cooling section  38 . the height of the sections of the grain columns  22  between the mixed-flow heating section  34  and the cross-flow cooling section  38  causes the grain to remain in the grain column  22  of the mixed-flow heating section  34  longer than the grain remains in the grain column  22  of the cross-flow cooling section  38 . 
     In the arrangement shown, as one example, grain columns  22  of tempering section  36  are defined at their outward sides by the interior surface of exterior walls  24  and at their inward sides by the interior surface of interior walls  26 . Similarly, grain columns  22  of tempering section  36  are defined at their outward ends by the interior surface end walls  52 . 
     As mentioned, tempering section  36  narrows the width of grain column  22  as it extends downward from mixed-flow heating section  34  to cross-flow cooling section  38 . In the arrangement shown, as one example, the exterior wall  24  of tempering section  36  extends slightly inward at an angle from its upper end (at the lower end  86  of mixed-flow heating section  34 ) to midpoint  102  positioned approximately two thirds of the way down the tempering section  36  and about one third of the way above the lower end  100  of tempering section  36 . In the arrangement shown, as one example, the exterior wall  24  of tempering section  36  extends approximately vertically between midpoint  102  and the lower end  100  of tempering section  36 . Similarly, In the arrangement shown, as one example, the interior wall  26  of tempering section  36  extends inward at an angle from its upper end (at the lower end  86  of mixed-flow heating section  34 ) to midpoint  102  positioned approximately two thirds of the way down the tempering section  36  and about one third of the way above the lower end  100  of tempering section  36 . In the arrangement shown, as one example, the interior wall  26  of tempering section  36  extends approximately vertically between midpoint  102  and the lower end  100  of tempering section  36 . In the arrangement shown, as one example, the angle of interior wall  26  is substantially greater than the angle of exterior wall  24 . However any other configuration of is hereby contemplated for use as tempering section  36 . 
     In the arrangement shown, as one example, exterior wall  24  and interior wall  26  of tempering section  36  are solid from their upper end to their lower end. As such, air flow is prevented through exterior wall  24  and interior wall  26  of tempering section  36  which substantially reduces, prevents and/or wholly stops air flow through the grain column  22  in tempering section  36 . This is important in that the tempering section  36  separates the mixed-flow heating section  34  from the cross-flow cooling section  38  and the mixed-flow heating section  34  operates by air being forced outward through the grain column  22  while the cross-flow cooling section  38  operates by air being pulled inward through the grain column  22 . By having the exterior wall  24  and interior wall  26  of tempering section  36  be of requisite height as well as be solid, this reduces, prevents or stops the bleeding of air flow from one of the cross-flow cooling section  38  and the mixed-flow heating section  34  to the other of the cross-flow cooling section  38  and the mixed-flow heating section  34 . In this way, the solid exterior wall  24  and interior wall  26  of tempering section  36  serves to separate the reverse air flows of mixed-flow heating section  34  from the cross-flow cooling section  38 . 
     In the arrangement shown, as one example, the upper end of tempering section  36  approximately aligns with the plane formed by divider  60  which separates heat plenum  62  from cool plenum  64 . The presence of divider  60  at the upper end of tempering section  36  further helps to limit the bleeding of air flow from one of the cross-flow cooling section  38  and the mixed-flow heating section  34  to the other of the cross-flow cooling section  38  and the mixed-flow heating section  34 . 
     In the arrangement shown, as one example a baffle  104  is positioned within the grain column  22  of tempering section  36 . Baffle  104  is formed of any suitable size, shape and design and is configured to help direct grain flow from the grain column  22  of mixed-flow heating section  34  to the grain column  22  of the cross-flow cooling section  38  in an even and consistent manner such that grain flows evenly across the width of the grain column  22  of mixed-flow heating section  34  so as to facilitate even heating and drying. In one arrangement baffle  104  is useful in evening the flow of grain from grain column  22  of mixed-flow heating section  34  due to the narrowing of the grain column  22  in tempering section  36  and/or the varying angles of exterior wall  24  and interior wall  26  of tempering section  36 . 
     In the arrangement shown, as one example, a single baffle  104  is positioned in the grain column  22  of tempering section  36 , however any number of baffles  104  are hereby contemplated for use such as none, two, three, four or more. In the arrangement shown, as one example, baffle  104  is a generally flat and straight planar member that extends the length of tempering section  36  from end wall  52  to end wall  52 , however any other size shape and configuration is hereby contemplated for use. In the arrangement shown, as one example, the upper end of baffle  104  is positioned in approximate alignment with the upper end of tempering section  36  and the lower end of baffle  104  terminates in approximate alignment with the midpoint  102 , which coincides with the grain column resuming vertically extending exterior walls  24  and interior walls  26 . In this way, baffle  104  evenly transitions the flow of grain from the vertically extending straight exterior walls  24  and interior walls  26  of mixed-flow heating section  34  to the vertically extending straight exterior walls  24  and interior walls  26  of cross-flow cooling section  38 . As baffle  104  is itself a solid member, baffle  104  also serves to reduce cross-flow air movement within grain column  22 . 
     If it were not for divider and the solid exterior walls  24  and interior walls  26  of tempering section  36 , the vacuum air pressure of cross-flow cooling section  38  would draw air in from the mixed-flow heating section  34 . By separating cross-flow cooling section  38  from the mixed-flow heating section  34  by the length of the solid exterior walls  24  and interior walls  26  of tempering section  36  this reduces or prevents cross-contamination of air flow between cross-flow cooling section  38  and mixed-flow heating section  34 . 
     The lower end  100  of tempering section  36  connects to the upper end of cross-flow cooling section  38 . 
     In one arrangement, the width of grain column  22  in the mixed-flow heating section  34  is approximately thirty inches wide, whereas the width of the grain column  22  in the cross-flow cooling section  38  is approximately fourteen inches wide. As such, in this arrangement, as one example, the width of the grain column  22  in the cross-flow cooling section  38  is less than half the width of the grain column  22  in the mixed-flow heating section  34 . Any other configuration or dimensions are hereby contemplated for use. 
     Cross-Flow Cooling Section: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a cross-flow cooling section  38 . Cross-flow cooling section  38  is formed of any suitable size, shape and design and is configured to facilitate cooling of grain in grain columns  22  as well as facilitating heat recovery to improve energy efficiency of the system  10 . 
     In the arrangement shown, as one example cross-flow cooling section  38  extends vertically from its upper end, at the lower end  100  of tempering section  36 , to its lower end  106 , at the upper end of unloading system  40 . Cross-flow cooling section  38  is defined at its outward sides by the exterior surface of exterior walls  24 . Cross-flow cooling section  38  is defined at its outward ends by the exterior surface of end walls  52 . 
     In the arrangement shown, as one example, grain columns  22  extend through cross-flow cooling section  38  from its upper end to its lower end  106 . More specifically, in the arrangement shown, as one example, grain columns  22  of cross-flow cooling section  38  have a generally consistent width and shape from the lower end  100  of tempering section  36  to a transition point  108  midway between the upper end of cross-flow cooling section  38  and the lower end  106  cross-flow cooling section  38 . That is, grain columns  22  of cross-flow cooling section  38  are defined at their outward sides by the interior surface of exterior walls  24  and at their inward sides by the interior surface of interior walls  26 , wherein exterior walls  24  and interior walls  26  extend in approximate parallel spaced relationship to one another from upper end of cross-flow cooling section  38  to lower end  106  of cross-flow cooling section  38 . Similarly, grain columns  22  of cross-flow cooling section  38  are defined at their outward ends by the interior surface end walls  52 . In this way, grain columns  22  of cross-flow cooling section  38  above transition point  108  are generally square or rectangular in shape and extend vertically. 
     In the arrangement shown, as one example, at transition point  108 , grain columns  22  transition from vertical extension to an angled inward extension toward the generally centrally positioned unloading system  40 . More specifically, the exterior walls  24  and interior walls  26  angle inward at transition point  108 . Notably, the width of grain columns  22  remain constant above and below transition point  108  and the transition point  108  in interior wall  26  is positioned slightly above the transition point  108  in exterior wall  24 , so as to maintain a consistent width of grain column  22  above and below transition point  108 . 
     In the arrangement shown, as one example, exterior wall  24  and interior wall  26  of cross-flow cooling section  38  facilitate airflow through the grain columns  22 . In one arrangement, exterior wall  24  and interior wall  26  of cross-flow cooling section  38  are formed of perforated sheets of material, however any other configuration of a barrier that prevents the passage of grain there through while allowing for air flow there through is hereby contemplated for use. 
     The lower end  106  of cross-flow cooling section  38  connects to and feeds grain to the upper end of unloading system  40 . 
     In use, air handling system  42  is fluidly connected to the hollow interior of cool plenum  64 . Air handling system  42  applies a vacuum to cool plenum  64  thereby sucking or pulling air out of cool plenum  64 . This vacuum applied to cool plenum  64  causes air to be drawn through the air-permeable exterior wall  24  of cross-flow cooling section  38 , the air is then drawn through the grain in the grain column  22  of cross-flow cooling section  38 , the air is then drawn through the air-permeable interior wall  26  and into the cool plenum  64 . Air handling system  42 , using fan system  44  then pulls air out of the cool plenum  64  and blows it under pressure into heat plenum  62  along with heat added by heating system  46 . 
     As ambient air is drawn through the heated grain in grain column  22  of cross-flow cooling section  38 , the ambient air cools the grain and is itself warmed. This air flow also helps to carry away moisture from the heated grain thereby further drying the grain. The result is that the air that is fed into the air handling system  42  is warmed thereby harnessing the principles of heat conservation, and recycling heat. This means that the air that is blown into the heat plenum  62  must be warmed to a lesser degree than it would otherwise be if ambient air was used. As the air blown into heat plenum  62  needs to be heated to a lesser degree to achieve the desired temperature due to the conservation of heat and recycling of heat, lets energy is used to dry the grain. Another benefit is that the temperature of the grain that is discharged from the cross-flow cooling section  38  is cooler than it would otherwise be if it were not passed through the cross-flow cooling section  38 . Cooling the grain before it is stored improves the stability of the grain in long term storage and requires less handling precautions. 
     Another substantial benefit of the cross-flow cooling section  38  is that angles inward at its lower end thereby facilitating unloading of the grain at a single unload point, which is unloading system  40 . 
     Unloading System: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes an unloading system  40 . Unloading system  40  is formed of any suitable size, shape and design and is configured to facilitate unloading of dry grain from system  10 . 
     Any form of a grain unloading system is hereby contemplated for use as unloading system  40 . In the arrangement shown, as one example, unloading system  40  is an auger system that receives grain from the ends of each grain column  22 . A shaft  70  with flighting  71  extends across the lower end of system  10 . The shaft  70  with flighting  71  is connected to a motor  72  (not shown) by a pulley and belt system (also not shown) and is configured to rotate the shaft  70  with flighting  71 . Unloading system  40  facilitates the discharge of grain at a single discharge point  110 . 
     In the arrangement shown, as one example, the exterior walls  24  angle inward from the lower end  106  of cross-flow cooling section  38  to the point where they connect to one another just below the center of unloading system  40 , or more specifically the center of shaft  70  with flighting  71 . Similarly, in the arrangement shown, as one example, the interior walls  26  angle inward from the lower end  106  of cross-flow cooling section  38  to the point where they connect to one another just above the center of unloading system  40 , or more specifically the center of shaft  70  with flighting  71 . In this way, the adjacent grain columns  22  converge with one another at unloading system  40 . 
     In the arrangement shown, as one example, a baffle  112  is positioned in grain column  22  a distance upstream of shaft  70  with flighting  71 . Baffle  112  is connected at its upward end to the interior surface of interior wall  26  and angles downward therefrom, across grain column  22 , before terminating at a free end adjacent metering roll  114 . Baffle  112  serves to direct grain from grain column  22  to metering roll  114  in such a way that the grain is evenly removed from grain column  22 . 
     Metering roll  114  is formed of any suitable size, shape and design and is configured to control the speed at which grain is metered out of the lower end of grain column  22  and into the unloading system  40  for discharge out of the system  10 . In the arrangement shown, as one example, metering rolls  114  include a shaft  116  having flights  118 . As the metering rolls  114  rotate, a quantity of grain is discharged to be unloaded. As such, the faster the metering rolls  114  rotate the faster the grain is discharged. The faster the metering rolls  114  rotate, the faster the grain moves through grain columns  22 . In the arrangement shown, baffles  112  and metering rolls  114  extend the forward to back length of system  10  from front end wall  52  to rear end wall  52 . 
     In the arrangement shown, as one example, a single baffle  112  and a single metering roll  114  is shown the grain column  22  on each side of unloading system  40 . However it is hereby contemplated for use to use two or more baffles and/or metering rolls  114 , which can provide operational advantages, such as independent control and increased discharge rates, among other advantages. 
     In operation, when grain in grain columns  22  reach the unloading system  40  the grain is directed by baffle  112  towards metering roll  114 . The shape, position and configuration of baffle  112  serves to ensure that grain is evenly moved from grain column  22 . As metering roll  114  rotates, as each flight  118  rotates, an amount of grain is moved passed baffle  112  and metering roll  114 . This grain, slides under the force of gravity along the interior lower surface of exterior wall  24  until it reaches the shaft  70  with flighting  71 . As the shaft  70  with flighting  71  rotates, the grain is moved along the length of system  10  to a discharge point  110  at which point the grain exits system  10 . 
     While in the arrangement shown, only a single auger, or shaft  70  with flighting  71  is used, it is hereby contemplated that multiple augers or multiple shafts  70  with flighting  71  are used in unloading system  40 . Alternatively, a belt, a conveyor, a paddle sweep and/or a drag chain system is hereby contemplated for use as unloading system  40 . Any other structure or configuration of a system for loading grain is hereby contemplated for use as unloading system  40 . 
     Air Handling System: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes an air handling system  42 . Air handling system  42  is formed of any suitable size, shape and design and is configured to facilitate air flow through the system  10  using fan system  44  as well as facilitating heating of that air flow using heating system  46 . 
     In the arrangement shown, as one example, air handling system  42  is connected to the forward end wall  52  of system  10 . More specifically, air handling system  42  is connected to both the cool plenum  64  as well as the heat plenum  62 . 
     In the arrangement shown, as one example, air handling system  42  includes a fan system  44 . Fan system  44  is formed of any suitable size shape and design and is configured to provide air flow through the system  10 . Fan system  44  may be formed of a single fan, or a plurality of fans or any other device that facilitates air flow. 
     In the arrangement shown, fan system  44  is fluidly connected to cool plenum  64  at its input end. In this way, when in operation, fan system  44  applies a vacuum to cool plenum  64  which has the effect of pulling or drawing air into the cool plenum  64  through the air permeable exterior wall  24  of cross-flow cooling section  38 , through the grain held in the grain column  22  of cross-flow cooling section  38 , and through the interior wall  26  of cross-flow cooling section  38  and into cool plenum  64 . 
     In the arrangement shown, fan system  44  is fluidly connected to heat plenum  62  at its output end. In this way, when in operation, fan system  44  applies pressurized air flow to heat plenum  62  which has the effect of forcing air into heat plenum  62 , through the open interior ends of inlet ducts  88 , out the open lower ends of inlet ducts  88  and into the grain column  22 , through the grain column  22 , into the open lower ends of exhaust ducts  90 , and out the open exterior end of the exhaust ducts  90  where it is vented to the environment. 
     In the arrangement shown, as one example, air handling system  42  includes a heating system  46 . Heating system  46  is formed of any suitable size shape and design and is configured to provide heat to heat the air flow through the system  10 . In one configuration, heating system  42  is placed at the output end of fan system  44  and is formed of one or more burners. When in operation, heating system  46  heats the air flow that is blown into heat plenum  62  of mixed-flow heating section  34 . 
     In the arrangement shown, as one example, air handling system  42  includes louvers  48 . Louvers  48  are formed of any suitable size, shape and design and are configured to control the amount of air that is pulled through cool plenum  64  as compared to the amount of air that is pulled from the surrounding environment. As louvers  48  are closed, more air is drawn through the cool plenum  64 , which means more air is drawn through the grain in grain column  22  of the cross-flow cooling section  38  thereby cooling the grain to a greater amount and recycling more heat. As louvers  48  are opened, more air is drawn from the surrounding environment, which means less air is drawn through the grain in grain column  22  of the cross-flow cooling section  38  thereby cooling the grain to a lesser amount and recycling less heat. 
     In the arrangement shown, as one example, air handling system  42  is fluidly connected to the end wall  52  by a duct system  120  that forms an air passage way from cool plenum  64  to the input end of air handling system  42  as well as forms an air passage way from the output end of air handling system  42  to the heat plenum  62 . Through the air passage ways formed by duct system  120  air is passed from cool plenum  64  to air handling system  42  to heat plenum  62 . 
     Also, in the arrangement shown, air handling system  42  has a housing  122  that surrounds the exterior of air handling system  42 . This housing  122  serves to prevent and/or control the air flow into and out of the air handling system  42 . In the arrangement shown, as one example, louvers  48  selectively cover openings in this housing  122 . 
     Support System: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a support system  50 . Support system  50  is formed of any suitable size, shape and design and is configured to provide strength and rigid support for mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10 . 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  has a single point unloading system  40 . This provides many advantages as the grain is unloaded at a single point by a single mechanical device (unloading system  40 ) which reduces mechanical complexity of the system  10  in some ways and eliminates moving parts. While having a single point unload provides some benefits, it also provides some challenges. Namely, due to the inwardly angling exterior walls  24  that connect to unloading system  40 , the lower end of system  10  is not well suited to sit upon the ground or a platform. Instead, due to the configuration of the lower end of the system  10 , a support system  50  is needed to raise the lower end of the system  10  above the ground or platform upon which it rests and/or provide additional stability to the system  10 . 
     In the arrangement shown, as one example, support system  50  is formed of a plurality of horizontal supports  124  and a plurality of vertical supports  126 . Horizontal supports  124  and vertical supports  126  are formed of any suitable size, shape and design and extend between and connect to the platform upon which system  10  sits and/or structural components of the system  10 , and/or horizontal supports  124  and vertical supports  126  connect to one another. In the arrangement shown, as one example the plurality of horizontal supports  124  and plurality of vertical supports  126  raise the main body of system  10  above the ground or platform that system  10  sits upon as well as provides a strong and stable base for system  10 . 
     In Operation: 
     In operation, wet grain is supplied to the input  68  of loading system  30 . The as the motor  72  operates this causes the shaft  70  with flighting  71  to rotate which causes the grain to evenly move across the upper end of the wet hold section  32 . When the wet grain is added to the wet hold section  32  the grain travels down under the force of gravity between exterior wall  24  and interior wall  26 . The grain is separated into a pair of grain columns  22  which exist on each side of a plenum  28 . As the grain exits the lower end of the wet hold section  32  the grain enters the upper end of the mixed-flow heating section  34 . 
     As the grain travels down the mixed-flow heating section  34  the grain travels downward within the grain column  22  between the exterior wall  24  and interior wall  26  and between end walls  52 . As the grain travels downward within the grain column  22  of mixed-flow heating section  34  the grain encounters the triangular shaped inlet ducts  88  and exhaust ducts  90  that extend across the grain columns  22 . As the grain encounters the triangular shaped inlet ducts  88  and exhaust ducts  90  the grain is directed to one side or the other due to the triangular shaped inlet ducts  88  and exhaust ducts  90 . It is important to note that due to the off-set position of vertically adjacent inlet ducts  88  and exhaust ducts  90 , the grain is moved laterally within the grain column  22 . This lateral movement, as the grain moves vertically, has a mixing effect on the grain, which facilitates gentle and even heating of the grain. 
     As the grain passes through the grain column  22  of the mixed-flow heating section  34 , heated air is blown by the air handling system  42  into the heat plenum  62 . This heated pressurized air flow to heat plenum  62  is forced through the open interior ends of inlet ducts  88  that connect with interior wall  26 . This heated pressurized air flow is then forced along the length of inlet ducts  88  until it passes out the open lower end of inlet ducts  88  and into the grain of grain column  22 . This heated pressurized air flow passes through the grain in the grain column  22  there by heating and drying the grain. This heated pressurized air flow finds its way into the open lower end of exhaust ducts  90 . This heated pressurized air is then forced along the length of exhaust ducts  90  until it passes out the open exterior end of exhaust ducts  90  at which point it is vented to the atmosphere. 
     As the grain travels downward and passes the lower end of mixed-flow heating section  34  the grain enters the tempering section  36 . As the grain enters the tempering section  36  the grain engages the inward angling exterior wall  24  and interior wall  26  which narrows the width of the grain column  22  from the wider mixed-flow heating section  34  to the narrower cross-flow cooling section  38 . In this transition, the grain engages baffle  104  which ensures the grain is evenly removed from the mixed-flow heating section  34 . Due to the interior wall  26  and exterior wall  24  of tempering section  36  being solid and air impermeable, little or no air flows through the grain in grain column of tempering section  36 . 
     As the grain travels downward and passes the lower end of tempering section  36  the grain enters the cross-flow cooling section  38 . As the grain travels down the grain column in the cross-flow cooling section  38  air is pulled through the air permeable exterior wall  24 , through the grain in the grain column  22  thereby cooling and further drying the grain, and through the air permeable interior wall  26 , and into the cool plenum  64 . This warmed air is then recycled by air handling system  42  up to the heat plenum  62  of the mixed-flow heating section  34  with supplemental heat added by heating system  46  and so the cycle is repeated. 
     As the grain exits the lower end of the cross-flow cooling section  38  the grain enters the unloading system  40 . As the grain travels down the grain column  22  of the unloading system  40  the grain engages and is directed by the baffle  112  toward metering roll  114 . As the metering roll  114  rotates grain is dispensed to the auger system having a shaft  70  and flighting  71 . As the shaft  70  with fighting  71  rotates the grain is moved along the length of the system  10  until it passes out the discharge point  110 . 
     In this way, grain is heated and dried in an efficient and gentle manner using mixed-flow heating section  34 , tempering section  36  and cross-flow cooling section  38  of mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10 . 
     Central Controller: 
     In the arrangement shown, as one example, mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10  includes a central controller that controls operation of the mixed-flow grain dryer with cross-flow vacuum cool heat recovery system  10 , or more specifically controls operation of the loading system  30 , the unloading system  40 , the air handling system  42  including fan system  44 , heating system  46  and louvers  48 , and any other electrical and/or controllable component of the system  10 . 
     Second Mixed-Flow Heating Section: 
     In one arrangement, a second mixed-flow heating section  34  with its own air handling system  42  is positioned on top of the first mixed-flow heating section  34 . In this arrangement, the heat plenum  62  of the first mixed-flow heating section  34  and the heat plenum  62  of the second mixed-flow heating section  34  are separated by a divider  60 . For all intents and purposes the second mixed-flow heating section  34  and air handling system  42  operate similarly if not identically to the first mixed-flow heating section  34  and air handling system  42  described herein with the biggest difference being that there is no heat recovery associated with the second air handling system  42 . That is, the second air handling system  42  simply blows heated air into the heat plenum  62  of the second mixed-flow heating section  34 . The addition of a second mixed-flow heating section  34  increases capacity of the system  10 . 
     It is hereby contemplated that any number of additional mixed-flow heating sections  34  with their own air handling systems  42  may be stacked onto the system  10  presented herein to add capacity to the system  10  such as two, three, four, five, six or more additional mixed-flow heating sections  34  with their own air handling systems  42 . 
     From the above discussion it will be appreciated that the mixed-flow grain dryer with cross-flow heat recovery system presented herein improves upon the state of the art. More specifically, and without limitation, it will be appreciated that the mixed-flow grain dryer with cross-flow heat recovery system presented herein: is efficient to use; facilitates heat recovery; reduces fuel consumption; is gentle on grain; does not damage grain when drying; does not overly dry grain; facilitates cooling of grain before it is discharged; evenly dries grain; does not have variability of grain quality across the grain column; does not have variability of moisture across the grain column; can be precisely controlled; that provides optimum results; that facilitates unloading of grain from the dryer at a single point; is relatively compact; is relatively inexpensive; can be used with all kinds of grain; that minimizes maintenance; requires less cleaning; is cleaner to use than prior art systems; is safe to use; reduces the potential for a fire; requires less air pressure; requires less air flow; provides improved grain quality; is easy to use; has a robust design; is high quality; incorporates the benefits of mixed-flow grain dying with the benefits of cross-flow vacuum cooling, among countless other advantages and improvements. 
     It will be appreciated by those skilled in the art that other various modifications could be made to the device without parting from the spirit and scope of this disclosure. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby.