Abstract:
A vacuum kiln apparatus and method of using same are disclosed for use in drying corn, other grains, seeds and legumes. The vacuum kiln apparatus can include a support base, a wall, a vacuum pump system, a pressure valve, a top hatch, a machinery access hatch, an anti-overload baffle, a conveyor system, a motor, a chamber vent valve, an air outlet manifold and an air compressor. The wall defines an internal chamber for receiving the grain. The vacuum pump system is used to draw down the pressure within the internal chamber which drives moisture out of the corn while maintaining the integrity of the corn, i.e., drying the corn with little or no cracking. The air outlet manifold along with the air compressor are used to flush high pressure air through the piles of corn to strips off any residual water that may be clinging onto the exterior of the corn grains.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present invention relates kilns, more particularly to a vacuum kilm for use in reducing residual moisture in grain such as corn or seeds, legumes or other agricultural products that require drying. 
       BACKGROUND 
       [0002]    It is preferable to lower the amount of latent moisture in grains in order to extend their shelf life. Drying grains inhibits molds, such as,  Diplodia, Gibberella, Fusarium, Aspergillus , and  Alfatoxin  from compromising the integrity of the grains prior to consumption. 
         [0003]    Conventional drying methods for treating freshly harvested grains have been to thermally drive latent moisture water out of the grain by burning fossil fuels and even burning discarded construction materials. These forced hot air methods are expensive and waste and require vast amounts of expensive fuels. As a result, conventional drying methods can exhibit very negative effects, such as releasing untold amounts of pollutants/carbons which in turn contribute to global warming. Accordingly, there is a need to dry grains by using a more economical and ecological means. 
       SUMMARY 
       [0004]    The vacuum kiln apparatus and method of using the same, according to the principles of the present invention, overcomes a number of the shortcomings of the prior art by providing a novel vacuum kiln apparatus and method for use in drying corn and other types of grains, seeds and legumes for longer storage life. 
         [0005]    This method uses a chamber capable of pulling a vacuum to extract the moisture from grain, legumes, seeds and nuts and uses forced high-pressure air to remove the moisture from the tank. It will also be capable of being insulated/heated if necessary. The vacuum kiln will be preferably made of stainless steel for a long operational usage against the vacuum, but other alloys and coatings may be suitable. The electrical needs are customary for a normal installation of this kind being 240 v single phase. 
         [0006]    The vacuum kiln apparatus includes a support base, a wall, a vacuum pump system, a pressure valve, a top hatch, a machinery access hatch, an anti-overload baffle, a conveyor system, a motor, a chamber vent valve, an air outlet manifold and an air compressor. The wall defines an internal chamber for receiving the grain. The vacuum pump system is used to draw down the pressure within the internal chamber which drives moisture out of the corn while maintaining the integrity of the corn, i.e., drying the corn with little or no cracking, no heat damage and less damage due to excess movement. The air outlet manifold along with the air compressor are used to produced a pulse of elevated air pressure that strips off any residual water that may be clinging onto the exterior of the corn. The method of using includes the steps of collecting, closing, detaching, dispensing, elevating, evacuating, forcing, maintaining, measuring, obtaining, opening, removing, repeating, retrieving, testing, turning off, and venting. 
         [0007]    The steps in operation for this system are generally as follows. First the media—typically grain, but other crops may be used—are loaded in the chamber while removing any unwanted material using the compressor and the venture in combination. Second the pressure in the chamber is reduced through the use of a vacuum pump. This second step will evaporate the moisture trapped inside the media. Third, moisture level inside the chamber will be monitored until a substantially constant moisture reading is achieved. While the time duration will vary based on volume and type of grain, with a specific moisture level versus time, it is expected that 30 minutes will typically be suitable. Fourth, after the constant moisture reading described is achieved, the vacuum will be released. Extracted moisture will be removed from the chamber with forced air. The foregoing steps two through five can be repeated as necessary until the desired final moisture level achieved. As a final step, after the desired final moisture level is achieved the media may be removed. 
         [0008]    There has thus been outlined, rather broadly, certain features of the invention in order that the detailed description thereof that follows may be understood, and in order that the present contribution to the art may be appreciated. 
         [0009]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be better understood and aspects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
           [0011]      FIG. 1A  is a cross sectional side view of a first embodiment of a vertical embodiment of the vacuum kiln apparatus; 
           [0012]      FIG. 1B  is a cross sectional side view of the upper portion of the first embodiment of a vertical embodiment of the vacuum kiln apparatus; 
           [0013]      FIG. 1C  is a cross sectional side view of the wall construction of the first embodiment of a vertical embodiment of the vacuum kiln apparatus; 
           [0014]      FIG. 2  is a cross sectional side view of a second embodiment of a vertical embodiment of the vacuum kiln apparatus; 
           [0015]      FIG. 3  is a cross sectional side view of a horizontal embodiment the present vacuum kiln apparatus; and 
           [0016]      FIG. 4  is a cross sectional front view of the horizontal embodiment of the vacuum kiln apparatus. 
       
    
    
       [0017]    The same reference numerals refer to the same parts throughout the various figures. 
       DETAILED DESCRIPTION 
       [0018]    The present disclosure will now be described more fully with reference to the accompanying drawings, in which examples of the disclosure are shown. The disclosure may be, however, embodied in many different forms and should not be construed as being limited to these variations as set forth herein; rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those of ordinary skill in the art. 
         [0019]    The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order to more clearly depict certain features of the disclosure. Further, it should be understood that, although various steps of various the disclosed methods may be shown and described as being in a sequence or temporal order, the steps of any such method are not necessarily limited to being carried out in any particular sequence or order, absent an indication otherwise. That is, the method steps are to be considered to be capable of being carried out in any sequential combination or permutation order while still falling within the scope of the present disclosure. 
         [0020]    Various features described herein can be combined in various embodiment of the vacuum kiln apparatus  10 . The apparatus has a support base  30 , a wall  40 , a vacuum pump system  80 , a pressure valve  90 , a top hatch  100 , a machinery access hatch, a conveyor system  120 , a bottom array  130 , a motor  140 , a chamber vent valve  150 , and an air compressor  160 . The wall  40  is attached to the support base  30  in which the wall  40  has a top access opening  50  and a machinery access opening  60  such that the wall  40  defines an internal chamber  70 . The vacuum pump system  80  is in communication with the internal chamber  70 . The pressure valve  90  is in communications with the internal chamber  70 . The top hatch  100  is attached to the wall  40  in which the top hatch  100  is configured to hermetically seal the top access opening  50  of the wall  40 . The machinery access hatch is attached to the wall  40  in which the machinery access port  110  is configured to hermetically seal the machinery access opening  60  of the wall  40 . The conveyor system  120  is mounted within the internal chamber  70 . The bottom array  130  is mounted within the internal chamber  70  of the wall  40  such that the bottom array  130  is configured to deliver grain  20  to the conveyor system  120 . The motor  140  is coupled to the conveyor system  120  and mounted within the internal chamber  70 . The chamber vent valve  150  is in communications with the internal chamber  70 . The air compressor  160  is in communications with the internal chamber  70 . 
         [0021]    The apparatus  10  may additionally comprise a top baffle array  170  mounted within the internal chamber  70  of the wall  40  such that the top baffle array  170  is configured to receive grain  20  from the conveyor system  120 . 
         [0022]    The apparatus  10  may additionally be fitted with an anti-overload baffle  180 , an air outlet manifold  440 , and an off-load port  200 . The anti-overload baffle  180  is mounted within the internal chamber  70  of the wall  40 . The air outlet manifold  440  is mounted within the internal chamber  70  such that the air outlet manifold  440  is coupled to the air compressor  160 . The off-load port  200  is attached to the wall  40  such that the off-load access opening  190  can be hermetically sealed at the off-load port  200 . 
         [0023]    The conveyor system  120  can be any commercially known conveyor system  120  such an Archimedes screw conveyor system  120  comprising a helical screw  210  coupled to the motor  140  and a sheath  220  surrounding the helical screw  210 . Another variant of the conveyor is that it is a belt system  230  coupled to the motor  140  in which the belt system  230  may operate in conjunction with a vented platform  240 . 
         [0024]    In this first vertical embodiment, the apparatus  10  may further comprise a support arm  250 , a discharge conduit  260 , and a sealing adaptor  290 . The support arm  250  is configured to be attached to the wall  40 . The discharge conduit  260  preferably comprises an inner end  270  and a chute  280 . The sealing adaptor  290  is configured to be coupled to the inner end  270  of the discharge conduit  260  and to the conveyor system  120  for receiving grain  20  from the conveyor system  120 , wherein the sealing adaptor  290  is also configured to be mounted to the top access opening  50  of the wall  40 . 
         [0025]    The apparatus  10 , in various embodiments, may also have a drive mechanism  300  that is configured to couple together the motor  140  to the conveyor system  120 . 
         [0026]    The apparatus  10  may also comprise a heater  310  mounted within the internal chamber  70  of the wall  40 . 
         [0027]    The wall  40  may be constructed of any commercially known wall  40  configuration as long as it is able to maintain a internal chamber  70  reduced pressure of about one thirtieth of an atmosphere. One preferred variant of the wall  40  is that it comprises: an outer skin  320 , a plenum  330 , a plenum valve  340  in communications with the plenum  330 , an insulative layer  350 , and an inner skin  360 . The insulative layer  350  and the outer skin  320  define the plenum  330  therebetween. The wall  40  may further comprise: a screen  370  secured to the inner skin  360 , and a gap  380  defined between the screen  370  and the inner skin  360 . 
         [0028]    The insulative layer  350  may be made of any known insulative material such as those selected from the group consisting of polyethylene-polypropylene, polynitrile, polystyrene-polybutadiene, polybutadiene, natural rubber, polychloroprene, polyurethane, polyisocyanurate, polyphenolic, polyvinyl chloride, polyurea-aldehyde, polymelamine-aldehyde, polystyrene, polypropylene, polyethylene, cellulose acetate, polyepoxy, polyacrylonitrile, polysilicone, polyethylene terephthalate, polyurethane, cotton, and fiberglass. 
         [0029]    The apparatus  10  may further comprise a control panel  390  which is configured to control the chamber vent valve  150 , and the air compressor  160 . 
         [0030]    The apparatus  10  may also further comprise a humidity detector  400  configured to detect humidity within the internal chamber  70 . 
         [0031]    The apparatus  10  can be configured to dry grain  20  such as those selected from the group consisting of corn, rice, wheat, oats, barley, quinoa and mixtures thereof. Preferably the grain  20  is corn. 
         [0032]    The apparatus  10  may further include a drying unit  410  in communication with the air compressor  160  for reducing the humidity of the ambient air being pressured. The drying unit  410  may charged with active material selected from the group consisting of activated carbon, ammonium chloride, silica, calcium chloride, calcium oxide, calcium sulfate, molecular sieves, zeolites, magnesium sulfate, sodium phosphate di-basic, potassium carbonate, potassium aluminum disulfate, magnesium chloride, diammonium sulfate, sodium nitrate, sodium chloride, potassium bromide, clays and blends of these materials. It is preferable that the bottom array  130  has a plurality of perforations  420 . 
         [0033]    Vacuum pump system  80 , can use vacuum pump  82  connected to chamber  70  through vacuum lines  84 . As described, vacuum causes moisture in grain  20  to migrate to the surface of each individual piece. When the selected moisture parameters, also described herein, are met, that surface moisture can be migrated away from the grain  20  using high pressure air through manifold  440  and thereafter. Air passage is enhanced by supporting grain  20  on vented platform  240 . The moisture laden higher pressure air can be exhausted from chamber  70  and grain  20  removed through discharge valve or port  262 . 
         [0034]    The high pressure air is pressurized by compressor  160  through air lines or conduits  442 . Solenoid valves  444  at predetermined locations control closing or opening conduits  442  in communication with chamber  70 . Venturi conduits  446  can be fitted to high pressure conduits  442  in order to utilize pressurized airflow through conduits  442 / 446  to impart a relative vacuum to provide increased efficiency in pressure management in chamber  70 . 
         [0035]    Vertical or horizontal units may be usable for drying grain  20 . Horizontal units may have support base  30 , a wall  40 , a vacuum pump system  80 , a pressure valve  90 , a top hatch or hatches  100 , an off-load port  190 , a humidity sensor or detector  400 , a conveyor system  120 , a bottom array  130 , a chamber vent valve  150 , an air compressor  160 , an anti-overload baffle  180 , an air outlet manifold  440  mounted, and a control panel  390 . The wall  40  is attached to the support base  30  in which the wall  40  has a top access opening  50 , a machinery access opening  60 , and an off-load access opening  190  in which the wall  40  defines an internal chamber  70 . Perforated vented platform  240  supports the grain  20  permitting air circulation and directing the grain  20  to conveyor  120 . 
         [0036]    The vacuum pump system  80  can be configured to be in communication with the internal chamber  70  using compressor  82  and vacuum lines  84 . A pressure valve  90  is configured to be in communication with the internal chamber  70 . The top hatch  100  is attached to the wall  40  such that the top hatch  100  is configured to hermetically seal the top access opening  50  of the wall  40 . The machinery access hatch is attached to the wall  40  in which the machinery access port  110  is configured to hermetically seal the machinery access opening  60  of the wall  40 . The off-load port  200  is attached to the end wall  40 , visible in  FIG. 3 , in which the off-load port  200  is configured to hermetically seal the off-load access opening  190  of the wall  40 . The humidity detector  400  is configured to detect humidity within the internal chamber  70 . The motor  140  is mounted within the internal chamber  70 . The conveyor system  120  is mounted within the internal chamber  70  such that the conveyor system  120  comprises a belt system  230  coupled to the motor  140 . Air circulation through grain  20  is promoted by vented platform  240 . The bottom array  130  is mounted within the internal chamber  70  of the wall  40  and the bottom array  130  is configured to deliver grain  20  to the conveyor system  120  and the bottom array  130  has a plurality of perforations  420 . The chamber vent valve  150  is configured to be in communications with the internal chamber  70 . At the bottom of chamber  70  is located pit cock drain solenoid valve  448  which will enable draining of condensed moisture. 
         [0037]    The air compressor  160  is configured to be in communications with the internal chamber  70 . The anti-overload baffle  180  is mounted within the internal chamber  70  of the wall  40  and is configured to control a height of the grain  20  on the conveyor system  120 . The compressed air manifold  440  is mounted within the internal chamber  70  and manifold  440  is coupled to the air compressor  160  through lines  440  and valves  444  so that a high pressure dose of air in the internal chamber  70  can be provided to enhance displacement out through the chamber  70  of moisture clinging on the surface of the individual grain  20 . The control panel  390  is configured to control the chamber vent valve  150  and the air compressor  160 . 
         [0038]    One preferred embodiment of a method of removing excess moisture in grain  20  to extend a shelf life of the dried grain  20 , the method comprising the steps of collecting, closing, detaching, dispensing, evacuating, flushing, maintaining, measuring, obtaining, opening, removing, repeating, retrieving, testing, turning off, and venting. The obtaining step comprises obtaining a vacuum kiln apparatus  10  for drying the grain  20  to an acceptable moisture level, the apparatus  10  comprises: a support base  30 ; a wall  40  attached to the support base  30 , the wall  40  having a top access opening  50  and a machinery access opening  60  an off-load access opening  190 , wherein the wall  40  defines an internal chamber  70 ; a vacuum pump system  80  in communication with the internal chamber  70 ; a pressure valve  90  in communications with the internal chamber  70 ; a top hatch  100  attached to the wall  40 , wherein the top hatch  100  is configured to hermetically seal the top access opening  50  of the wall  40 ; a machinery access hatch attached to the wall  40 , wherein the machinery access port  110  is configured to hermetically seal the machinery access opening  60  of the wall  40 ; an off-load port  200  attached to the wall  40 , wherein the off-load port  200  configured to hermetically seal the off-load access opening  190  of the wall  40 ; a humidity detector  400  configured to detect humidity within the internal chamber  70 ; a motor  140  mounted within the internal chamber  70 ; a conveyor system  120  mounted within the internal chamber  70 , wherein the conveyor system  120  comprises a belt system  230  coupled to the motor  140  in which the belt system  230  comprises a vented platform  240 ; a bottom array  130  mounted within the internal chamber  70  of the wall  40 , the bottom array  130  configured to deliver grain  20  to the conveyor system  120  and the bottom array  130  has a plurality of perforations  420 ; a chamber vent valve  150  in communications with the internal chamber  70 ; an air compressor  160  in communications with the internal chamber  70 ; an anti-overload baffle  180  mounted within the internal chamber  70  of the wall  40 ; an air outlet manifold  440  mounted within the internal chamber  70 , wherein the air outlet manifold  440  is coupled to the air compressor  160 ; and a control panel  390  configured to control the chamber vent valve  150 , and the air compressor  160 . 
         [0039]    The opening step comprises opening the top hatch  100  to unseal and to open up the top access opening  50  of the wall  40 . The dispensing step comprises dispensing grain  20  into the internal chamber  70  of the apparatus  10  onto the conveyor system  120  so that a portion of the grain  20  is on the vented platform  240  of the belt system  230 . The closing step comprises closing the opened top hatch  100  to hermetically seal the top access opening  50  of the wall  40 . 
         [0040]    The evacuating step comprises evacuating the internal chamber  70  of the apparatus  10  to reduce a pressure within internal chamber  70  while the grain  20  is on the vented platform  240  of the belt system  230  by turning on the vacuum pump system  80 . The measuring step comprises measuring the pressure within the internal chamber  70  with the pressure valve  90 . The turning off step comprises turning off the vacuum pump system  80  after a reduced pressure within the internal chamber  70  has been reached. The maintaining step comprises maintaining the reduced pressure within the internal chamber  70  for an extended period of time to slowly pull out water from the grain  20 . The venting step comprises the internal chamber  70  by opening up the pressure value  90  to allow ambient air into the internal chamber  70 . The flushing step comprises flushing the internal chamber  70  after venting the pressured air into the internal chamber to reduce residual humidity in the internal chamber. The evacuating, measuring, turning off, maintaining, venting and flushing steps can be performed repetitively, or cycled, until a desired final moisture content over time is achieved, once benchmark performance parameters are defined. 
         [0041]    The detaching step comprises detaching the off-load port  200  to unseal the off-load access opening  190  and to gain access into the internal chamber  70 . The retrieving step comprises retrieving a sample of the grain  20  through the off-load access opening  190 . The testing step comprises testing a level of moisture in the retrieved grain  20 . The repeating step comprises repeating the steps of evacuating, measuring, turning off, maintaining, elevating, forcing, and venting, when the tested level of moisture in the retrieved grain  20  is above a suitable level. The removing step comprises removing the grain  20  from the internal chamber  70  when the tested level of moisture in the retrieved grain  20  is at or below a suitable level. The collecting step comprises collecting the removed grain  20  in a hopper  430 . 
         [0042]    As alternative embodiments, the off-loading an repeating steps may be performed and recorded to define benchmark time, pressure and moisture parameters for particular crops and conditions. As another alternative, the off-loading step can comprise a sampling step whereby not all of the grain is off-loaded, the sample determining if further cycles on grain remaining resident is necessary. 
         [0043]    The method may also further comprise the steps of entering, exiting, performing, resealing, and unsealing. The unsealing step comprises unsealing the machinery access hatch to unseal and open up the machinery access opening  60  of the wall  40 . The entering step comprises entering into the internal chamber  70  through the machinery access hatch when the machinery access opening  60  is unsealed. The performing step comprises performing maintenance on the motor  140  when the machinery access opening  60  is unsealed. The exiting step comprises exiting from the internal chamber  70  through the machinery access hatch when the machinery access opening  60  is unsealed. The resealing step comprises resealing the machinery access hatch to hermetically seal the machinery access opening  60  of the wall  40 . 
         [0044]    With respect to the specific embodiments illustrating the apparatus, while these have been described generally, with alternative or optional features, the specific drawings can be now described. 
         [0045]      FIG. 1A  depicts a cross sectional view of a vertical alignment embodiment of the vacuum kiln apparatus  10  comprising a support base  30 , a wall  40 , a vacuum pump system  80 , a pressure valve  90 , a top hatch  100 , a machinery access hatch  110 , a conveyor system  120 , a top baffle array  170 , a bottom array  130 , a motor  140 , a chamber vent valve  150 , a plenum valve, a pressure valve, a heater  310 , a control panel  390 , an air compressor  160 , a support arm  250 , a discharge conduit  260 . The wall  40  is shown attached to the support base  30  in which the wall  40  has a top access opening  50  and a machinery access opening  60  such that the wall  40  defines an internal chamber  70 . The vacuum pump system  80  is shown in communication with the internal chamber  70 . The pressure valve  90  is shown in communications with the internal chamber  70 . The top hatch  100  is shown hermetically sealing the top access opening  50  of the wall  40 . The machinery access hatch is shown hermetically sealing the machinery access opening  60  of the wall  40 . The conveyor system  120  is shown as an Archimedes screw conveyor system  120  mounted vertically within the internal chamber  70 . The Archimedes screw conveyor system  120  is shown comprising a helical screw  210  coupled to the motor  140  and a sheath  220  surrounding the helical screw  210 . The bottom array  130  is shown mounted within the internal chamber  70  of the wall  40  so that the bottom array  130  is configured to deliver grain  20  to the conveyor system  120 . The motor  140  is shown coupled to the conveyor system  120  and mounted within the internal chamber  70 . The chamber vent valve  150  shown is in communications with the internal chamber  70 . The air compressor  160  is shown in communications with the internal chamber  70 . 
         [0046]      FIG. 1B  depicts a cross sectional view of the vacuum kiln apparatus  10  comprising the sealing adaptor  290  coupled to the top access opening  50  with the top hatch  100  hinged away. The sealing adaptor  290  is also shown coupled to the inner end  270  of the discharge conduit  260  and to the conveyor system  120  for receiving grain  20  from the conveyor system  120   
         [0047]      FIG. 1C  depicts a cross sectional view of the wall  40  comprising an outer skin  320 , a plenum  330 , a plenum valve  340  in communications with the plenum  330 , an insulative layer  350 , and an inner skin  360 . The insulative layer  350  and the outer skin  320  define the plenum  330  therebetween. The wall  40  is also shown comprising a screen  370  secured to the inner skin  360  and a gap  380  defined between the screen  370  and the inner skin  360 . 
         [0048]      FIG. 2  depicts an alternative vertical embodiment of the vacuum dryer  10 . Vacuum pump system  80 , uses vacuum pump  82  connected through vacuum lines  84 . Chamber  70  is subject to vacuum and selectively to high pressure air pressurized by compressor  160  to manifold  440  through air lines or conduits  442 . Solenoid valves  444  control closing or opening conduits  442 . Air passage is enhanced by supporting grain  20  on vented platform  240 . Venturi conduits  446  can utilize pressurized airflow to impart a relative vacuum. Grain  20  is removed through discharge valve or port  262 . 
         [0049]      FIG. 3  depicts a cross sectional side view of a horizontally aligned vacuum kiln apparatus  10  comprising a support base  30 , a wall  40 , a vacuum pump system  80 , a top hatch  100 , a machinery access hatch  110 , an off-load port  200 , a conveyor system  120 , an anti-overload baffle  180 , a drying unit  410 , and an air outlet manifold  440 . 
         [0050]      FIG. 4  depicts a cross sectional side view of a horizontally aligned vacuum kiln apparatus  10  comprising a wall  40  having a internal chamber  70 , a top hatch  100  sealing the top access opening  50 , a machinery access port sealing the bottom access opening  60 , a conveyor system  120  composed of a belt system  230  with a vented platform  240 , an anti-overload baffle  180  mounted about the conveyor system  120 , and an air outlet manifold  440  underneath the conveyor system  120 . 
         [0051]    The foregoing apparatus can be used to perform the method steps. In the course of developing the invention, testing was performed using laboratory/workshop sized equipment and is described in the following examples. 
       Example 1 
     12 Hour Vacuum No Air Purge 
       [0052]    Corn grain, initially having a moisture content of 20.1%, was placed in the vacuum kiln. The pressure inside the vacuum kiln was then reduced by 27.5 inches of mercury and the temperature was maintained at approximately 70° F. After 12 hours of exposure to the vacuum, the corn grain sample was removed and found to have a moisture content of 12.1%. The dried corn grain did not exhibit any cracking. 
       Example 2 
     Two 12 Hour Vacuum Exposures with Air Purges 
       [0053]    Corn grain, initially having a moisture content of 24.5%, was placed in the vacuum kiln. The pressure inside the vacuum kiln was then reduced by about 27 inches of mercury and the temperature was maintained at about 71° F. After 12 hours of exposure to the vacuum, the vacuum kiln was purged with air at approximately 120 psi and then opened. Afterwards, the corn grain was found to have a moisture content of about 18.0%. The corn grain was again subjected to a reduced pressure of about 27.6 inches of mercury in the vacuum kiln and maintained isothermally at about 71° F. After 12 another hours, the vacuum kiln was again purged with air at approximately 120 psi and then opened. The subsequently dried corn grain was found to have a final moisture content of about 14.9%. 
       Example 3 
     Two 8 Hour Vacuum Exposures with Air Purges 
       [0054]    Corn grain, initially having a moisture content of 20.4%, was placed in the vacuum kiln. The pressure inside the vacuum kiln was then reduced by about 27 inches of mercury and the temperature was maintained at about 67° F. After 8 hours of exposure to the vacuum, the vacuum kiln was purged with air at approximately 120 psi and then opened. The pressure inside the vacuum kiln was again reduced by about 27 inches of mercury and the temperature was maintained at about 67° F. After another 8 hours of exposure to the vacuum, the vacuum kiln was again purged with air at approximately 120 psi and then opened. The subsequently dried corn grain was found to have a final moisture content of about 14.9%. 
       Example 4 
     Two 12 Hour Vacuum Exposures with Air Purges 
       [0055]    Corn grain, initially having a moisture content of 20.1%, was placed in the vacuum kiln. The pressure inside the vacuum kiln was then reduced by about 27 inches of mercury and the temperature was maintained at about 67° F. After 12 hours of exposure to the vacuum, the vacuum kiln was purged with air at approximately 120 psi and then opened. At this stage, the corn grain was found to have a moisture content of about 15.9%. The pressure inside the vacuum kiln was again reduced by about 27 inches of mercury and the temperature was maintained at about 68° F. After another 12 hours of exposure to the vacuum, the vacuum kiln was again purged with air at approximately 120 psi and then opened. The subsequently dried corn grain was found to have a final moisture content of about 14.3%. 
         [0056]    While preferred embodiments of the vacuum kiln apparatus have been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. 
         [0057]    Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.