Patent Publication Number: US-10329690-B2

Title: Drying seed cotton in a feed controller

Description:
This application is partly based on Provisional Patent Application Ser. No. 61/190,106 filed Aug. 26, 2008 on which priority is claimed. This application is a continuation of application Ser. No. 14/121,031 filed Jul. 21, 2014, which is based on application Ser. No. 13/066,690 filed Apr. 22, 2011, which in turn is based on application Ser. No. 12/455,725, filed Jun. 5, 2009, now U.S. Pat. No. 8,046,877. 
    
    
     This invention relates to the drying of seed cotton and other crops. 
     BACKGROUND OF THE INVENTION 
     Cotton, wheat, corn, sorghum, soybeans, and hay or silage are typical crops that are widely grown. Harvesting these crops cannot be started in the morning until the sun has warmed the plants sufficiently to drive off dew or other moisture. Harvesting can continue until dew falls in late evening, typically long after the sun has gone down. Thus, there is a long period—often about 12 hours a day—when most crops cannot be harvested because the crop is too wet. The exact moisture conditions differ somewhat for different crops but the overall problem is the same, i.e. if the crop is too wet, harvesting has to wait because the wet crop will rot. Sorghum, corn and other grains are a particular problem because, when harvested too wet, they cannot be fed even to livestock because of the production of certain aflatoxins. 
     When cotton is picked or stripped in the field, a wide variety of things accumulate a cotton module that is transported to a gin for ginning. Picked or stripped seed cotton produces a collection of cotton lint, motes, cotton seed and gin trash, which is the industry term for dirt, leaves, stems, weeds and weed seeds. Currently, seed cotton is dumped from a picker or stripper into a module builder on the edge of a field where a large rectangular module is created by tamping the seed cotton in a large metal container. A new generation of cotton pickers produces a module which is discharged on the field, eliminating the need for a separate module builder. One of the new generation of cotton pickers produces a plastic wrapped round module. 
     Picking of cotton from the field does not normally start until the morning sun warms the plants sufficiently to drive off any dew or other moisture. A moisture sensor is typically used to determine the moisture content of the plant so picking can be delayed until the moisture content in the seed cotton and debris falls below some predetermined value, typically around 12%. The reason is that, at higher moisture levels, there is a risk of plant debris rotting or excessive moisture causing microbial changes in cotton fibers resulting in staining which cannot be removed before the cotton is ginned because there is often a delay of up to several months from the time cotton is picked until it is ginned. When considerable rotting or staining occurs, the cotton fibers are degraded thereby reducing the grade of the ginned cotton and thus the price obtained for it. 
     The cotton modules are delivered to a cotton gin where the module is stored until the gin is ready for the particular module. The module is delivered onto the conveyor of a module feeder where it is disintegrated so cotton clumps pass into the gin where the lint is separated from cotton seeds and gin trash. One of the operations in a conventional cotton gin is to heat the unprocessed cotton enough to further reduce the moisture content. This is desirable because it is much easier to separate cotton and seed from leaves, stems and the like at low moisture levels as opposed to higher moisture levels. For example, conventional gin stands operate efficiently at moisture levels in the 4-6% range while roller gin stands operate best at much lower moisture levels. In the past, almost all gins have used a natural gas fired heater to heat the seed cotton and evaporate some or most of the water from the stream passing through the dryer. 
     It is known in the prior art to use microwaves to heat ginned cotton to counteract the effects of honeydew an cotton as shown in U.S. Pat. Nos. 4,896,400; 4,999,926; 5,008,978 and 5,048,156. It is known in the prior art to incorporate dryers in harvesters of hay, U.S. Pat. Nos. 4,912,914 and 5,105,563, and grains, U.S. Pat. Nos. 4,038,758; 4,509,273; 5,156,570; and 6,536,133. Of more general interest are the disclosures in U.S. Pat. Nos. 3,940,885; 4,640,020; 4,649,055 and 5,153,968. At least one attempt has been made to dry seed cotton in a cotton gin environment with microwaves but was unsuccessful because it popped the cotton seeds and the attempt was abandoned. Conventional domestic microwave ovens and conventional radio frequency ovens have been used to dry seed cotton in a laboratory in a research project to estimate cotton yields early in the season at a time before the bolls open. 
     SUMMARY OF THE INVENTION 
     It would clearly toe a great advantage to farmers, and particularly to custom harvesters, to operate crop harvesters for longer periods and thereby increase the productivity of their equipment. 
     The newest diesel engines, particularly so called Tier 4 engines, produce an exhaust that is remarkably non-polluting, i.e it contains very little soot, unburned hydrocarbons or other pollutants. One concept is to use the exhaust from Tier 3 and Tier 4 diesel engines to dry products, particularly crops such as cotton, wheat, corn, sorghum, soybeans, hay or silage, almonds, pistachios and the like as they are being harvested by directly contacting the crop with the hot exhaust gas. There is nothing in the exhaust that will damage the products or impart an objectionable odor to the crop. In addition, the ability to remove moisture at the time of harvesting in a simple, inexpensive manner has many advantages. Using exhaust gases from newer diesel engines accomplishes this, either alone or in combination with heated air from other sources as discussed below, can accomplish this. 
     Another broad concept is to use heat given off on the exterior of the engine for drying crops. This is accomplished by providing a shroud on the outside of the engine and/or on the outside of the engine radiator and drawing atmospheric air through the shroud. This heated air, either alone or in combination with the diesel exhaust, is used on a harvester to dry crops. 
     In another aspect, a method and apparatus used in a cotton gin differs from the prior art by recognizing that popping of the cotton seeds was caused by too high energy levels concentrated in a small space, i.e. using a single high power magnetron or using multiple high power magnetrons which concentrated all of the power in a small space, was the cause of popping. 
     In some embodiments, seed cotton may be dried by the application of wave energy from the electromagnetic spectrum, specifically by what is known as radio frequency heating and/or microwave heating. It has been found that wave energy heating is considerably more efficient than natural gas fired heaters in this application. Calculations done after short field trials using microwave magnetrons as the energy source suggest that energy savings are in the range of 40-70%. There are a variety of cumulative reasons which account for the magnitude of the savings. 
     From tests run in a gin with an early prototype microwave heater, it is apparent that separation of cotton seed and lint from gin trash is much easier and more efficient than with conventional natural gas fired dryers. Without being bound by any theory, it appears that this improvement is due to the dielectric properties of lint, trash and seed. 
     In some embodiments, an array of wave energy generators is used to produce a dispersed energy field having am energy density in the range of 0.2-6 kilowatts per pound of seed cotton. It has been learned that energy densities less than two tenths kilowatt per pound of seed cotton are not very effective in reducing moisture in seed cotton. Concentrated wave energy or energy densities greater than six kilowatts per pound of seed cotton tend to heat the seed cotton so much that the cotton seeds pop like popcorn and popped cotton seeds are not salable. In addition, modern cotton gins are not equipped to separate lint from popped cotton seeds. 
     In a cotton gin environment, some of the dryer embodiments of may be housed in conduits between conventional equipment in the gin or, preferably, in a feed controller near the upstream end of the gin. In some embodiments, the conduit or feed controller may be of metal having flat sides, such as square or rectangular conduit, and may be lined with a material of a type that prevents arcing when stray metal pieces pass through the dryer. One reason the preferred location for the dryer may be in the feed controller is because the conventional air locks upstream and downstream of the feed controller may be modified in accordance with some embodiments to prevent escape of microwaves past the air looks. 
     In a cotton picker/stripper environment, an important advantage of the dryer is that picking or stripping can be started before the sun warms the plant sufficiently to lower the moisture content enough to prevent rotting. Indeed, sufficient drying can be accomplished to allow picking or stripping throughout the day and/or night thereby increasing the utilization of equipment and thereby lowering unit costs. In addition, it will be apparent that 24 hour operation is overwhelmingly attractive in areas that are subject to hurricanes. Cotton farmers become exceedingly antsy with a crop in the field and a tropical storm en route. Long periods of operation are also overwhelmingly attractive to custom harvesters. 
     Another important advantage of the seed cotton dryer, in a cotton gin environment, is the complete absence of combustion products, except in unusual situations where the cotton is so wet that conventional natural gas heating is also required or in the situation where diesel exhaust is used as a primary or supplementary heating source, as disclosed in greater detail hereinafter. In any event, there is a substantial reduction in pollutants escaping to the atmosphere. This is particularly advantageous in areas such as California where increasingly strict regulations restrict the use of natural gas fired dryers and/or increase their cost of operation. 
     It is an object of this invention to provide an improved method and apparatus for drying seed cotton. 
     Another object of this invention is to provide an improved method and apparatus for drying seed cotton either on a picker/stripper or in a cotton gin. 
     A further object of this invention is to provide an improved method and apparatus for drying seed cotton which promotes separation of the cotton and seed from leaves, stems and other plant parts. 
     Another object of this invention is to provide an improved method and apparatus for drying crops using the exhaust from diesel engines. 
     These and other objects and advantages of this invention will become more fully apparent as this description proceeds. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of part of a cotton gin illustrating one embodiment of a seed cotton dryer; 
         FIG. 2  is an enlarged view of the upper end of the flow controller of  FIG. 1 , partly in section, illustrating an air lock and several magnetrons; 
         FIG. 3  is an isometric rear view of a feed controller into which a dryer is incorporated; 
         FIG. 4  is a cross-sectional view of a conventional belt conveyor into which a dryer is incorporated; and 
         FIG. 5  is a cross-sectional view of a cotton picker equipped with a seed cotton dryer; 
         FIG. 6  is a side view of a cotton picker that has been modified to incorporate a new drying technique, certain parts being broken away to illustrate some of the components of the dryer; 
         FIG. 7  is a schematic view of one embodiment of a drying system; 
         FIG. 8  is a schematic view of another embodiment of a drying system; 
         FIG. 9  is a schematic view of a preferred drying system; and 
         FIG. 10  is a schematic view of another drying system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-3 , there is illustrated part of a conventional cotton gin  10  comprising, as major components, a module feeder  12  for disintegrating a cotton module  14 , a transport system  16  for delivering cotton clumps from the module feeder  12  through the various components of the gin  10 , a feed controller  18 , a series of separators or cleaners  20 ,  22  for separating cotton seed and lint from plant debris, one or more gin stands  24  for separating cotton seed from lint and one or more separators or cyclones  26  for separating gin trash from conveying air. 
     The module feeder  12  may be of any conventional type and typically includes an inlet conveyor  28  on which a rectangular or round module  14  is moved toward a plurality of disperser drums  32  which disintegrate the module  14 . Cotton clumps from the module  14  are moved by the transport system  16  through the various components of the gin  10 . 
     In some embodiments, the transport system  16  is pneumatic in the sense of having an air inlet  34  and a fan  36  pushing air through a series of conduits  38  provided by the transport system  16  thereby moving the cotton clumps toward or through the various components of the gin  10 . 
     Most, but not all, conventional cotton gins include a separator/cleaner  20  near the module feeder  12  for removing large trash from the stream of material exiting the module feeder. Many gins include a feed controller  18 , which is sometimes known as a BIG J, which is a trademark of one brand feed controller, or a steady flow which is a generic term, near the inlet end of the transport system  16  having the capability of accumulating seed cotton and then withdrawing the accumulated seed cotton for the purpose of keeping the gin stands  24  full. To this end, manipulating a series of feed rollers  40 , constituting a flow regulator, near the discharge end of the feed controller  18  increases or decreases the flow of seed cotton from the controller  18  typically in response to a feedback loop from the gin stands  24 . Air locks  42 ,  44  are conventionally provided in gins employing air conveyed cotton near the inlet and outlet ends of the feed controller conduit  46  to prevent loss of conveying air while allowing cotton to continue moving through the gin  10 . 
     Air locks work by sealing an elongate conveyance area, which is round in cross-section, with a rotary array of rubber wipers that allow seed cotton and trash to pass through a round chamber while sealing off the conveyance area and thereby preventing air loss. It is possible that standard air locks might leak microwave or radio frequency energy so, in some embodiments, the interior of the arcuate housing  48  is designed to prevent wave energy leakage. If this is a problem, the wipers  54  and metal housing  48  are made to such close tolerances that there is no leakage. 
     As shown best by a comparison of  FIGS. 1 and 4 , in some embodiments the feed controller conduit  46  is of rectangular cross-section having a funnel shaped inlet  56  spanning the width of the air lock  42 , a pair of flat parallel side walls  58 , a pair of flat parallel end walls  60  and an outlet  62  which can be of any suitable shape, including a conventional funnel, in which the feed rollers  40  are located. The optimal shape of the conduit  46  may vary and much depends on the capacity of the gin or the speed of cotton moving through the conduit  46 . The depth of penetration of the waves is a function of the frequency of the wave generator and it is desirable for the wave energy to penetrate the seed cotton moving in the conduit  46 . In many embodiments, feed controller conduits  46  are much wider than they are deep, as shown best by a comparison of  FIGS. 2 and 3 . In many embodiments, the side and end walls  58 ,  60  need not be square or rectangular but they are preferably some type polygon because the angle between flat walls scatter wave energy better than round or smoothly curved walls. 
     Conventionally, the unprocessed seed cotton and plant debris is dried by burning natural gas and delivering the hot combustion products to the inlet  34  of the transport system  16  so the seed cotton is heated to evaporate some or west of the water absorbed on the seed cotton and plant parts. Typically, there is considerable heat loss because of conduction, convection and radiation from the conduits transporting the combustion products plus heat loss from air leaks which can reach as high as 30%. 
     In some embodiments, seed cotton and trash are heated by wave energy in the electromagnetic spectrum. In some embodiments, the wave energy generators can be placed in the conduits  38  of the transport system  16  or in a belt dryer as disclosed hereinafter. Preferably, the wave generators are placed upstream from a cleaner or stick machine because dried seed cotton separates much more easily from trash than moist seed cotton and seed cotton dried by the application of wave energy separates much better than seed cotton dried by natural gas fired heaters. One of the unusual features of cotton dried by wave energy is the ease of separating trash from seed cotton. Preferably, the wave energy generators are located in or are a part of the feed controller  18  or, in gins not having a feed controller, near the module feeder so the first cleaner works better. Regardless of the position of the dryer  64 , it is much preferred that the conduit to which wave energy generators are attached comprise a series of flat connected walls. Round or smoothly curved conduits, although operative, do not scatter wave energy as effectively as flat walled conduits. In some embodiments a multiplicity of relatively small capacity wave energy generators  66  are placed in a grid or array on one of the large flat side walls  58  of the feed controller conduit  46 . As will become more fully apparent hereinafter, the wave energy source is preferably dispersed to provide a relatively large area that is heated thereby preventing overheating of cotton seed to the extent that the seed pops. 
     In some embodiments, the wave energy generator are radio frequency generators producing frequencies, for example, preferably in the range of 13.56-40.68 mHz. In some embodiments, the wave energy generators are microwave magnetrons producing frequencies, preferably in the range of 915-2450 mHz or wave lengths in the range of 24-4.5 inches which is a very small part of the electromagnetic spectrum of 300 mHz to 3 gHz. It will be apparent that there is a very wide range of frequencies that are operative to heat water on the seed cotton passing through the dryer. 
     The power output of each individual wave energy generator can vary considerably, depending on the design volume throughput, the assumption made about inlet moisture content, the desired outlet moisture content, the spacing between the various generators  66  in the array and the exact pattern of the generators  66 . In some embodiments, the array is a series of lines of generators where each line is offset by one half the spacing between generators, as shown in  FIG. 4 . In some embodiments, as shown in  FIG. 4 , the generators  66  are offset or staggered in the direction  67  of movement through the feed controller  18  and perpendicular to the direction  67 . In embodiments where the generators  66  are of the same capacity, the pattern of the generators  66  tends to be regular, i.e. spaced equidistantly from each other. In embodiments where the generators are of different capacity, the pattern may be substantially nonuniform. One factor increasing the efficiency of the dryer is that the heat source is directly on the conduit  46  transporting cotton clumps in contrast to the conventional situation where the natural gas fired dryer is necessarily many feet away from the transport conduit. This inherently reduces heat losses from conduction, convection, radiation and air leaks. 
     There are upper and lower limits for the effective use of wave energy heating of seed cotton. There are a number of ways of expressing these limits. One problem is that no reasonably accurate measurements are made in a gin environment of the total weight of material being processed. Weight or volume measurements are made of cotton lint, seed cotton and cotton seeds. Roughly 1500 pounds of seed cotton produces 500 pounds of lint, 700-800 pounds of seed and 200 pounds of trash, condensed water and motes. Given the quantity of cotton lint being ginned, experienced people can make a reasonable estimate of the range of cotton seeds and gin trash being handled. Thus, it is estimated that the quantity of cotton seeds and gin trash in normal picked cotton is about 200% by weight of the amount of cotton lint. Stripped seed cotton, as contrasted to picked cotton, contains considerably more trash, e.g. 20-30% more than in picked seed cotton. What is known in a gin environment is the weight and/or volume of cotton lint being produced by the gin and is normally expressed in bales/hour. Currently, a bale is nominally 500 pounds of cotton lint. 
     A convenient expression for power output is the wattage of the wave energy generators. As is apparent from the particular pattern of  FIG. 4 , the generators produce a dispersed, as contrasted to a concentrated, energy that is reasonably averaged, both by the number and pattern of the generators  66  and because of scattering of energy waves inside the conduit  46 . In effect, there is a energy distributing zone  68  where the energy delivered by the generators  66  is more-or-less constant per unit area. 
     In some embodiments, the wave energy generators  66  produce a dispersed energy field having an energy density in the range of 0.2-6 kilowatts per pound of seed cotton. It has been learned that energy densities less than two tenths of a kilowatt per pound of seed cotton is not very effective in reducing moisture in seed cotton. Energy densities greater than six kilowatts per pound of seed cotton tends to heat the seed cotton so much that the cotton seeds pop like popcorn. 
     Another way of expressing the energy density of the wave energy source is in kilowatts per unit area of an energy distributing zone  68  where the outer boundaries are about one half the distance between generators  66 . It will be realized that the residence time of seed cotton in the conduit  46  has a substantial bearing on the total amount of energy delivered to the seed cotton. Residence time accordingly has a place in controlling or limiting the amount of wave energy applied to the seed cotton. It has been found with reasonable residence times that energy densities of less than about 0.3 kilowatts per square foot are not very effective to reduce moisture content in seed cotton while energy densities of greater than ten kilowatts per square foot is so great that overheating of the seed cotton is likely. In a prototype, having the generator array of  FIG. 4 , the energy distributing zone  68  had the capacity to deliver 48,000 watts over an area of twenty one square feet or an average of 2.286 kilowatts per square foot. This prototype was tested in a gin having a throughput of about 5000 pounds or ten bales of lint per hour which is about 15,000 pounds of seed cotton per hour, meaning that the energy density of the prototype was about 230 watts per square foot per bale of lint per hour or about 0.0153 watts per square foot per pound of seed cotton per hour. Short test runs reduced the moisture content of seed cotton significantly by amounts that correlated with the energy input from the generators  66 . 
     Another factor affecting the desired amount of energy input is the depth of the conduit  46  in a direction perpendicular to the side walls  58  or parallel to the end walls  60 . It will be apparent there is some distance perpendicular to the side walls  58  where wave energy will largely be absorbed before it reaches the opposite side wall. In these circumstances, there will be a tendency for seed cotton near the wall having the array of generators to be overheated while seed cotton near the opposite wall will be underheated. Although both side walls  58  might be equipped with an array of wave energy generators, it is preferred to make the conduit  46  relatively thin as shown by the contrast of the size of the side and end walls  58 ,  62 . This spreads the stream of seed cotton sufficiently for the generators  66  to effectively heat the absorbed water thereby promoting the efficiency of the dryer  64 . Although the depth of the conduit  46 , i.e. the size of the end walls  60 , may vary considerably, a depth of 6-12 inches for a dryer with generators  66  only on one side seems satisfactory for a microwave generator operating at a frequency of 2450 mHz. This, of course, is subject to considerable variation depending on a variety of factors, one of which is the frequency of the wave energy generator and another of which is the rate of cotton movement through the conduit  46 . 
     Because it is desirable to spread out the seed cotton passing through the dryer  64 , there is a range of desirable shapes for the conduit  46 . Typically, the width of the conduit  46  is preferably on the order of 4-10 times the depth. In other words, the side walls  58  are preferably 4-10 times the size of the end walls  60  and the length or height of the conduit  46  determines the average residence time in the dryer. 
     Another important advantage of wave energy heating, particularly in the microwave range, is the tendency of water to absorb the energy of microwaves in preference to oils, sugars or fats which are also present in the seed, seed coating, leaves, stems and other plant parts which is believed to be a function of their dielectric properties. Accordingly, cotton seed doesn&#39;t heat up so much because water preferentially absorbs the wave energy. This is thought to be a substantial factor in the improved efficiency of wave energy drying of seed cotton because the weight of cotton seed is such a large fraction, typically about half, of the total weight through the dryer. Thus, microwaves preferentially heat water and thereby efficiently evaporate water from the seed cotton and trash passing through the dryer. This undoubtedly contributes to the efficiency of wave energy heating when contrasted to heating with conventional natural gas dryers along with the difference in surface moisture and hygroscopic traits of cotton fibers. In tests run through the prototype device, gin trash seemed to jump away from seed cotton. The correct explanation for the tendency of gin trash to separate from unginned cotton bolls is not known but it is believed to be related to a lower moisture content than is normally achieved with natural gas fired dryers and may be due to the ability of microwave energy to removed moisture embedded deeply within seed cotton and trash. Without being bound by any theory, it appeared almost as if the gin trash had an opposite static electric charge than the unginned cotton bolls although this explanation is difficult to believe. How this could be is not known. To improve separation of trash from seed cotton, it is desirable that the wave energy dryers be located upstream from the separators. 
     Another important advantage of some embodiments is shown in  FIG. 2  where the inside of the conduit walls  58 ,  60  includes a lining  70 , usually plastic, having non-arcing properties. Metal pieces or particles are occasionally found in seed cotton modules. These pieces were either picked up off the ground during harvesting or were originally part of the harvesting and/or module building equipment. Even though magnetic separators can be incorporated into the separator/cleaner  20 , or further upstream, it is possible for both magnetic and especially non-magnetic metal particles, such as aluminum, to pass into the gin  10 . When metal particles appear adjacent the microwave generators  66 , in the absence of some type arcing protection, arcing can occur inside the conduit  46  thereby creating a fire hazard because of the wealth of small flammable particles and air inside the conduit  46 . To overcome this problem, the liner  70  is provided of non-arcing material of a suitable thickness to keep stray metal away from the walls of the conduit  46  and providing the additional advantage of isolating the magnetrons  66  from dust and debris in the conveyed seed cotton. Although there are a wide variety of non-arcing materials for this purpose, a suitable material is known, as UHMW which is ultrahigh molecular weight polyethylene. Other suitable materials generally have dielectric properties similar to or less than ultrahigh molecular weight polyethylene. For example, plexiglass proved not to be suitable because the plexiglass burned. 
     It will accordingly be seen that incorporating the dryer  64  into the flow controller  18  has the effect of using several components for different functions. For example, the conduit  46  acts as a surge capacity for the gin  10  in the normal manner of a flow controller, as does the conveyor of  FIG. 4  as will be apparent hereinafter, and also acts as the drying zone and as an anchor for the generators  66 . Similarly, the air locks  42 ,  44  prevent the loss of air from the transportation system  16  and also provides a safety feature by preventing the escape of microwave energy. In embodiments where the generators  66  are microwave generators, they may be mounted on wave guides  72  affixed to the wall  58  of the flow control conduit  46  as shown best in  FIG. 2 . 
     A major advantage of wave energy drying of seed cotton is the ability to quickly adjust the amount of energy being delivered to the seed cotton. As shown in  FIGS. 1 and 2 , a sensor  74  may be provided in the conduit  38  downstream of the heater  64  to measure the temperature, the humidity or other parameters related to drying of the seed cotton. The sensor  74  connects to a control unit  76  having an input  78  for indicating a desired value for one or more of the control parameters and an output  80  for controlling the amount of energy delivered to the generators  66  in response to inputs from the sensor  74 . It will evident that the time lapse between adjusting the energy input to the heater  64  and seeing a change in the parameter is much shorter than with conventional gas fired dryers. 
     Another major advantage of using wave energy for drying seed cotton is the absence of combustion products. This is in contrast to conventional natural gas fired heaters which produce a great deal of carbon dioxide in a short ginning season. 
     A further advantage of using wave energy for drying seed cotton is an improvement in drying efficiency, i.e. producing more moisture reduction for less energy expenditure. This is a function of a variety of factors, such as the reduction in heat losses from the location where it is generated to the location where it is used, the tendency of wave energy to be preferentially absorbed by water so the effect of the applied energy is focused on what is desired to be removed and the ability to quickly adjust the amount of energy applied to seed cotton as temperature and moisture content of the crop varies. Tests run during short field trials using microwave magnetrons as the energy source produced results such as shown in Table 1: 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                   
                 In a gin operating at 10 bales/hour, thirty two magnetrons 
               
               
                   
                 were used at 1500 watts each to dry seed cotton. This is 48 kw at 
               
               
                   
                 a then current cost of $.08 cents/kwhr to dry 5000 pounds of lint 
               
               
                   
                 which amounts to an energy cost of $.38/bale. 
               
               
                   
                 The microwave heater used replaced a gas fired heater using an 
               
               
                   
                 average of 2.5 therms/bale at a then current cost of $.61/therm for 
               
               
                   
                 an energy cost of $.81/bale. 
               
               
                   
               
            
           
         
       
     
     As shown in  FIG. 1 , in some embodiments, the heater  64  may be provided with a shroud  82  having an inlet opening  84  and an outlet opening  86  connected to the air inlet  34  by a suitable conduit  88 . Air flowing through the shroud  82  picks up heat produced by the wave generators  66  and becomes part of the conveying air transporting seed cotton to the heater  64  thereby preheating the seed cotton and improving overall efficiency to here 
     Operation of the gin  10  should now be apparent. The module feeder  12  digests the cotton module  14  so conveying air from the fan  36  transports seed cotton through the separator  20 , in those gins having a separator at this location, where large trash is removed from the seed cotton. Sometimes, the seed cotton passes rapidly through the feed controller  18  and sometimes there is a longer residence time in the controller  18 . In any event, the wave generators  66  deliver wave energy through the distributing zone  68  and heat the seed cotton in the conduit  46 . This causes some liquid water in the seed cotton to evaporate, the amount of which depends on the amount of energy applied to the seed cotton, the time that energy is applied, the geometry of the heating chamber and a number of other factors as will be apparent to those skilled in the art. 
     Heated seed cotton and high humidity air exit the conduit  46  and pass through the air lock  44  and into the conduit  38  downstream of the air lock  44 . It is necessary to separate the high humidity air from the seed cotton so the evaporated moisture does not recondense on the seed cotton. This is analogous to the current situation where natural gas combustion products are used to heat seed cotton and the solutions are substantially the same. In other words, air is allowed to escape from the conduit  38  in a conventional manner at conventional locations, such as in the inclined cleaner  22 , in other cleaners downstream from the heater  64 , from conventional battery condensers (not shown) and the like. In general, the sooner the water evaporated off the seed cotton is allowed to escape from the gin conduits and components, the better because there is less chance of the water recondensing on the seed cotton. In practice, allowing the water vapor to escape through the inclined cleaner  22  has proven satisfactory, at least partly because it takes only 4-5 seconds for cotton to reach the inclined cleaner  22  from the heater  64 . 
     Connected to the inclined cleaner  22  is a cotton outlet  90  leading to the gin stands  24 . Cotton exiting from the gin stands  24  passes through a conduit  92 , through additional cleaning equipment (not shown) and then to a baler  94 . In other words, the seed cotton, downstream of the heater  64 , is handled in a conventional manner. Air exiting from the inclined cleaner  22  may pass through a fan  94  and then into the cyclone  26  where conveying air is separated from dust and trash to prevent a large dust cloud emitting from the gin  10 . 
     It is desirable to rehumidify cotton lint before or during baling because extremely dry cotton lint does not pack readily into bales. A preferred source for water vapor to rehumidify cotton lint is any location where high humidity air is being vented from the air conveying system  16 , e.g. downstream of the inclined cleaner  22  through a conduit  96  having a control valve  98  therein. 
     It will be apparent that the wave energy heater may be incorporated into one or more of the ducts  38 , preferably upstream of the first separator  20 . As suggested previously, it is desirable to use polygonal ducts, such as square or rectangular rather than circular, as a conduit for the heater. to here 
     In some embodiments, the wave energy heater may be located at other locations or in conjunction with other equipment in a conventional cotton gin. Referring to  FIG. 4 , a conventional belt or chain conveyor  100  includes an enclosed housing  102  inside which a belt or chain  104  is driven around a pair of pulleys  106 ,  108 . At an inlet end  110  of the conveyor  100  is an air lock  112  while an air lock  114  is at an outlet end  116  of the conveyor  100 . The belt or chain conveyor  100  will be recognized by those skilled in the art as conventional. In some embodiments, the housing  102  conveniently includes a relatively flat upper wall  113  on which are mounted a series of wave generators  120 , such as microwave generators, mounted on wave guides  122 . The capacity and dispersion of the wave generators  120  is essentially the same as with the wave generators  66 . The belt conveyor  100  may be used to transport seed cotton in a conventional manner in a conventional location in a cotton gin while the wave generators  120  convert the conveyor  100  into a combined conveyor and heater. The belt conveyor  100  can be substituted for a feed controller because it can be slowed down to accumulate seed cotton or speeded up to keep the gin stands loaded. 
     Referring to  FIG. 5 , there is shown a conventional cotton picker  130  that is illustrated in greater detail in U.S. Pat. No. 6,263,650, to which reference is made for a more complete description of the conventional aspects thereof. The particular cotton picker  130  illustrated in U.S. Pat. No. 6,263,650 includes a main frame  132  supported for movement by forward drive wheels  134  and rear steerable wheels  136 . An operator&#39;s station  138  is supported at the front end of the main frame  132  above forwardly mounted harvesting structure  140  which removes cotton from plants and directs the removed cotton into a duct  142 , which preferably has flat sides, of an air conveying system  144 . The air conveying system  144  delivers seed cotton and trash into an accumulator  146  which includes an upright box having an open or screened top  147 , side walls  148 , a front wall  150  and a rear wall  152 , which are conveniently flat. Seed cotton and trash collecting in the accumulator  146  are ultimately fed into a hopper  154  where the seed cotton is formed into a round module  156  at least partially enclosed by a plastic cover (not shown). When, the module  156  is completely formed, a closure  158  of the hopper  154  opens thereby discharging the module  156  to the rear of the picker  130 . 
     Those skilled in the art will recognize the device of  FIG. 1  as being exemplary of modern cotton pickers. 
     To incorporate a wave energy drying technique to some embodiments of the picker  130 , advantage is taken of the size, location and shape of the accumulator  146 . Specifically, a series of wave energy generators  160  can be affixed to one or more of the accumulator walls  148 ,  150 ,  152 , depending on ease of installation and access. In some embodiments, the generators  160  are fixed to the front wall  150  to heat seed cotton and trash and thereby reduce its moisture content. 
     In other embodiments, the generators  160  are affixed to two or more of the walls  148 ,  150 ,  152  to obtain adequate penetration of the wave energy into seed cotton in the accumulator  146  because conventional accumulators tend to be large rectangles, such as 2′-3′×8′ and quite deep rather than flat, as in the case of the heating conduit  46  and the belt conveyor  100 . Heating the seed cotton in the accumulator  146  causes some of the moisture to evaporate. Because there is a tendency for moisture to build up in the accumulator  146 , moist air may be removed through a screen in the bottom of the accumulator  146  or some other suitable location. 
     In some embodiments, generators  162  can be affixed to the duct  142  to heat the seed cotton before it enters the accumulator  146 . This is of particular advantage because the top  147  of the accumulator  146  is typically open or screened thereby allowing the conveying air and evaporated water to exit from the picker  130 . 
     Drying seed cotton immediately after being harvested has a number of advantages. When seed cotton is picked from the boll, it is as fluffy as it will ever be, meaning that air flow through or around the picked tuft has the easiest time circulating adjacent water droplets adhering to the cotton fibers. Cotton fibers are highly absorbent, or hygroscopic, meaning that water becomes intertwined with the cotton on a molecular level. The longer a water droplet remains in contact with the fibers, and the more the crop is compacted, the more water is absorbed and the more difficult it is to finally remove toy heating. Drying crops as they are being harvested minimizes the absorption of water into the body of the crop and makes thermal drying more effective. 
     It is not necessary to remove all, or even a majority, of the water content of agricultural products as they are being harvested. Many advantages accrue to reducing the water content, even modestly. It often happens that harvesting is delayed in the mornings for a hour or so, waiting for the measured water content of the product to decline 1% from just over an accepted value to the maximum accepted value. Use of wave energy dryers in pickers allows considerably longer harvesting operations during each day because harvesting will no longer be quite so restricted by high moisture content of crops. This feature is particularly desirable to custom picker operations and to Gulf Coast farmers where the potential of hurricanes sometimes makes picking for long hours particularly desirable. At times of pending inclement weather where the crops must be harvested or lossy, the ability to dry seed cotton as it is being harvested may add as much as ten percent to the value of the cotton lint because there is much less loss of quality. 
     Referring to  FIG. 6 , there is shown another view of the conventional cotton picker that is illustrated in greater detail in U.S. Pat. No. 6,263,650, to which reference is made for a more complete description of the conventional aspects thereof. The particular cotton picker  170  includes a main frame  172  supported for movement by suitable front drive wheels  174  and steerable rear wheels  176 . An operator&#39;s station  178  is supported at the front end of the main frame  172  above forwardly mounted harvesting structure  180  which removes cotton from plants and directs the removed cotton into a flat sided duct  182  of an air conveying system  184 . As shown in  FIGS. 6 and 7 , an engine  186  is provided to propel the cotton picker  170  and provide a source of power for the auxiliary energy consuming components of the cotton picker. Those skilled in the art will recognize the device of  FIG. 6 , as heretofore described, as being exemplary of modern cotton pickers. 
     In some embodiments, the engine  186  is a Tier 3, Tier 4 or less polluting diesel engine. A shroud  188  covers the engine  186  and/or its conventional radiator  187 . One or more fans  190  draw air across the engine  186  and/or its radiator and through the shroud  188  and force the air through a conduit  192  into a venturi like device  194  inside the duct  192 . It will be seen that air drawn through the shroud  188  is heated by the hot engine  186  or its radiator  187 . Those skilled in the art will recognize the venturi like device  194  because it is similar or identical to that used in conventional air conveying systems  184 . Thus, a large quantity of heated conveying air causes a low pressure area in the duct  192  adjacent the harvesting structure  180 . Atmospheric air is thereby drawn through the harvesting structure  180  and a mixture of heated conveying air from the duct  192 , atmospheric air, seed cotton and trash are delivered through the duct  195  into the downstream components of the cotton picker  170 . 
     It will be recognized that the cotton picker  170  is exemplary of devices that produce a round or generally cylindrical cotton module wrapped with a plastic cover although it will also be recognized that this apparatus can be used on other style cotton pickers, grain combines and other harvesting equipment that are powered by modern diesel engines where it is desirable to dry, or partially dry, the crop during harvesting. The conveyed seed cotton, trash and heated conveying air are separated in or adjacent the accumulator  196  in the same manner as cotton pickers are currently operated. It will be recognized that some of the conveying air used in the system  184  may come from a fan (not shown) delivering air through a duct  198  having an outlet in the harvesting structure  180  in a conventional manner. 
     In some embodiments, as shown in  FIG. 8 , hot exhaust gas from a Tier 3, Tier 4 or less polluting diesel engine  200  passes through an exhaust  202  and is delivered through a valve  204  having one outlet connected to a conventional muffler  206  and exhaust pipe  208 . Thus, with the valve  204  directing exhaust gas to the muffler  206 , the cotton picker operates in a conventional manner. In some embodiments, a separate conveying air system, analogous to  FIG. 7 , may be provided so the conveyed seed cotton, trash and conveying gas are separated in or adjacent the accumulator in the same manner as cotton pickers are currently operated. 
     With the valve  204  in the position shown in  FIG. 8 , hot exhaust gas from the diesel engine  200  is propelled by a fan  210  into a duct  212  which connects to the venturi like device  214 , analogous to the device  194 , inside the duct  216 . Thus, the device of  FIG. 8  operates to provide hot exhaust gas as all or part of the conveying gas to produce a low pressure area adjacent the harvesting structure  218  to thereby propel seed cotton and trash toward the downstream elements of the cotton picker, namely toward its accumulator. Preferably, the location of the venturi like device  214  is as close as possible to the harvesting structure  218  so the amount of atmospheric air drawn in with the cotton is small when compared to the amount of hot exhaust gas from the fan  210 . This minimizes the amount of potentially high humidity air drawn in with the seed cotton and trash. A substantial advantage of the venturi like device  214  is that it produces slippage, i.e. a high velocity hot exhaust gas that is moving faster than the seed cotton and trash drawn into the duct  216 . Because of the higher velocity of the hot exhaust gas, the seed cotton and trash is exposed to more drying gas. In some embodiments, one or more pressure relief valves  220  can be incorporated to deal with overpressure situations in a manner that relieves any back pressure on the engine  200  without affecting the harvesting operation. 
     Because the conveying gas is partly or wholly hot diesel exhaust, considerable drying of the crop will occur during transit toward the accumulator. It will be seen that the conveyed seed cotton, trash and conveying gas are separated in or adjacent the accumulator in the same manner as cotton pickers are currently operated because the top of the accumulator is either open or screened. 
     Tier 3 and Tier 4 diesel engines produce an exhaust having the following pollutant profiles:
         Tier 3 diesel engines       

     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                   
                 quantity 
               
               
                   
                 pollutant  
                 grams/kilowatt-hour 
               
               
                   
                   
               
             
            
               
                   
                 non-methane hydrocarbons + 
                 4.0 
               
               
                   
                 oxides of nitrogen 
                   
               
               
                   
                 carbon monoxide 
                 3.5 
               
               
                   
                 particulate matter 
                 0.2 
               
               
                   
                   
               
            
           
         
       
         
         
           
             Tier 4 diesel engines 
           
         
       
    
                                                 quantity           pollutant    grams/kilowatt-hour                          non-methane hydrocarbons    0.19           oxides of nitrogen   3.5           carbon monoxide   0.4                        
It will accordingly be seen that directly contacting crops with the exhaust from Tier 3, Tier 4 or less polluting diesel engines causes considerable drying of the crop without damaging the crop or imparting an objectionable odor to the crop.
 
     Referring to  FIG. 9 , there is illustrated a system combining hot diesel exhaust and conveying air drawn from around a Tier 3 or Tier 4 or less polluting diesel engine  222  and/or its radiator  223  inside a shroud  224 . To these ends, the fans  226 ,  228  connect to ducts  230 ,  232  connected to a proportioning valve  234  that mixes air from the fan  226  and exhaust gas from the fan  228  in suitable proportions in any suitable manner, as by a control device  236  acting to speed up or slow down one or more of the fans  226 ,  228 . Operation of the proportioning valve  234  is preferably controlled automatically by a control device  236  such as a computer or calculating unit having an input  238  which may be adjusted by the operator to select a desired temperature, and/or a desired humidity level and/or other parameters. It will be apparent that the proportioning valve  234  may be eliminated provided the control unit  236  has the capacity to individually adjust operation of the fan  226 , i.e. taking all the exhaust gas from the fan  228  and mixing it was some or all of the air from the fan  226 . 
     The control unit  236  also includes an input  240  from a sensor  242  located at an appropriate location, such as in the duct  244 , which measures temperature, humidity and/or other parameters. A mixture of conveying air and diesel exhaust leaves the proportioning valve  234  and is delivered to the duct  246 , the venturi like device  248  and the duct  244  to propel seed cotton and trash from the harvesting structure  250  toward the accumulator. As in the embodiment of  FIG. 8 , the diesel engine exhaust may be equipped with a control valve  252 , conventional muffler  254  and exhaust pipe  256  to provide for conventional operation. One or more pressure relief valves  258  can be incorporated to deal with overpressure situations in a manner that relieves any back pressure on the engine  222  without affecting the harvesting operation. One or more pressure relief valves  258  can be incorporated to deal with overpressure situations in a manner that relieves any back pressure on the engine  12  without affecting the harvesting operation. 
     In other embodiments, exhaust gas from the fan  228  and air from the fan  226  may be separately connected to one or more venturi like devices in the duct  244  leading to the accumulator of the cotton picker. 
     Referring to  FIG. 10 , a suitably non-polluting diesel engine  260  delivers exhaust gas to a control valve  262  and then to a fan  264  connected into or immediately upstream of the accumulator  266  of the cotton picker to dry seed cotton temporarily in the accumulator  264 . As in other embodiments, the engine  260  may be provided with a conventional muffler  268  and exhaust pipe  270 . 
     Operation of the various embodiments will now be apparent. Hot conveying gas is delivered through the duct into the venturi like device thereby creating a low pressure area in the duct and drawing atmospheric air across the harvesting structure thereby propelling seed cotton and trash through the duct into the accumulator. 
     Thus, in the cotton pickers shown in  FIGS. 8-9 , exhaust gas from the diesel engines  200 ,  222  simultaneously conveys and heats seed cotton in transit between the harvesting structures  218 ,  250  and the accumulators. In the preferred cotton picker of  FIG. 9 , the amount of exhaust gas from the fan  228  and/or the amount of air from the fan  226  can be adjusted to produce a mixture that is (1) low enough in temperature so as not to damage the cotton lint or the cotton seed, (2) high enough in temperature to evaporate water off of the seed cotton and trash and (3) low enough in relative humidity to carry off the evaporated water without allowing it to recondense. In other embodiments having an auxiliary diesel engine used to power auxiliary equipment, the exhaust gas from the auxiliary diesel engine may be used for these purposes. 
     It will also be recognized that these drying mechanisms can be incorporated into other types of cotton pickers other than the type producing a round module wrapped with a plastic cover. 
     In a combine of the type used to harvest grain crops, the diesel exhaust may be directed into a chute or conduit where grain is being conveyed away from the header or into a bin where the grain is temporarily collected. Similarly, this technique may be incorporated into a nut harvester, such as those used to harvest almonds or pistachios, by directing the hot diesel exhaust into a chute or conduit where the nuts are being conveyed away from the harvesting structure or into a bin where the nuts are temporarily collected. 
     One may initially think that running the exhaust gas from the diesel engine through such a system will produce too much back pressure on the engine thereby degrading its performance. It will be seen that the fan  228 , for example, produces a sufficiently low pressure to allow the engine  222  to operate efficiently. It may be advantageous to operate the drying capability of such a picker at all times or it may be advantageous to turn off the drying capability after the crop naturally dries out from the sun. This may be accomplished, of course, by manipulating the valves  204 ,  252  and delivering exhaust gas through the mufflers  206 ,  254  and exhaust pipe  208 ,  256  to the atmosphere. It may be advantageous to warm up the diesel engine  200 ,  222  at the beginning of operations and purge the ducts and/or accumulator of any water that condensed from the previous day&#39;s operations. 
     Drying cotton, grains, hay or silage and nuts immediately after being harvested, has a number of advantages. When seed cotton is picked from the boll, it is as fluffy as it will ever be, meaning that air flow through or around the picked tuft has the easiest time circulating adjacent water droplets adhering to the cotton fibers. Cotton fibers are highly absorbent, or hygroscopic, meaning that water becomes intertwined with the cotton on a molecular level. The longer a water droplet remains in contact with the fibers, and the more the crop is compacted, the more water is absorbed and the more difficult it is to finally remove by heating. Drying crops as they are being harvested minimizes the absorption of water into the body of the crop and makes thermal drying more effective. 
     It is not necessary to remove all, or even a majority, of the water content of agricultural products as they are being harvested. Many advantages accrue to reducing the water content, even modestly. It often happens that harvesting is delayed in the mornings for a hour or so, waiting for the measured water content of the product to decline some modest amount, e.g. 1%, from just over an accepted value to the maximum accepted value. Drying crops in this manner allows considerably longer harvesting operations during each day because harvesting will no longer be quite so restricted by high moisture content of crops. 
     There is not thought to be any substantial fire hazard for a variety of reasons. First, in gin operations, conventional natural gas fired heaters expose seed cotton and trash to elevated temperatures in the presence of air without scorching the cotton fibers or starting fires. Second, the diesel exhaust can be mixed with ambient air to provide a relatively hot gas stream that is oxygen deficient because the oxygen in the exhaust gas is much reduced when compared with normal oxygen in air. 
     Although Tier 3 and certainly Tier 4 diesel engines produce an exhaust which can acceptably be directly contacted with a crop, including those for human consumption, it is possible to retrofit earlier model diesel engines with a heat exchanger heated by hot exhaust gases to provide a source of heat for drying crops during harvesting. In such an embodiment, air heated by the heat exchanger is directly contacted with the harvested crop to thereby reduce its moisture content. 
     Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.