Patent Publication Number: US-2010107439-A1

Title: High efficiency drier

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/198,036, filed Oct. 31, 2008 and incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to improvements in driers and methods of drying used to dry various materials, including newly harvested grain, wood pellets, and particulate materials of all types and, in particular, to driers that utilize fluid to heat the material, cool and dry the material with generally overall countercurrent air flow and recover and utilize a comparatively high percentage of the energy used in the drying process. 
     The drying industry is very large and utilizes significant amounts of both fossil fuels and electricity to dry various materials. While the grain industry is not the only industry that requires significant drying, it is indicative of the problems that exist. Just the United States corn crop amounts to over nine billion bushels annually. At least part of the moisture present at harvest must be removed in order to allow the grain to be stored without significant loss due to mold, mildew and rot, all caused by excess retained moisture. 
     In theory, each pound of water removed from the grain has a latent heat of vaporization of about 1160 British thermal units (Btu) per pound. In an extremely effective drier system, the drier could import exactly this theoretical amount of energy per pound of water to be removed from the material to be dried. In reality, the material to be dried also takes on sensible heat and rises in temperature, the flow of heated air or the like is often not uniform, the material is often heated more on one side of the drier than the other, etc., such that the efficiency of all types of conventional driers is comparatively low. For example, conventional cross flow grain driers usually require approximately more than 2000 Btu per pound of water removed versus the theoretical amount of 1160 Btu per pound. 
     Because just the corn industry in the United States consumes approximately 900 million gallons of propane and over 3200 million kilowatt-hours of electricity per year just to dry the corn and because this produces nearly two million tons of carbon dioxide exhaust gases per year due to the burning of fossil fuels, it is seen that any improvement in drying efficiency can amount to significant savings in fuel, energy and emissions. Corn is only one type of grain that must be dried. Further, there are many other solids, semi-solids and initially liquid compositions that are dried each year at considerable costs in terms of fuel, energy and undesired emissions due to combustion of the fuels. 
     It is further noted that for some materials the manner of drying is important to prevent excessive shock to the product being dried and/or to reduce inconsistency in the dried material. For example, grain kernels can be cracked by cooling or heating too quickly, which can lead to degradation of the grain. While conventional driers may produce a chosen average moisture content, the content may not be consistent throughout the grain. Consequently, problems are encountered generally in many types of conventional grain cross flow driers, where the grain is heated and dried by air passing perpendicularly to the flow of the grain. In such driers, the grain on one side of the drier that first encounters the heated air is overly dried and may be dried too quickly or cooled too quickly so as to cause cracking and the grain on the opposite or on the air discharge side tends to be too wet. 
     In some circumstances, it is also desirable to provide a closed recycle system for gas used in the drying process to reduce dust or other undesirable emissions. 
     SUMMARY OF THE INVENTION 
     A high efficiency drier for drying materials, especially particulate material of all types, that recovers and reutilizes a substantial portion of the heat used in the drying process, such that only a comparatively small amount of makeup heat must be added to the process. 
     The drier includes a generally enclosed drying chamber, a heating fluid recirculation system, a drying fluid circulation system, a regenerator, and a makeup heater. 
     The drying chamber of this application is preferably a vertical column through which material to be dried passes due to gravity under control of a discharge mechanism. The various embodiments include multiple bags within the chamber through which the material passes sequentially. In some of the embodiments the bays are in combined heating and drying regions. In other embodiments bays are in separate heating and drying regions. The heating fluid enters the drying chamber in a hot state and the recirculation system circulates the heating fluid sequentially through each heating compartment or bay along the path of the material to be dried. The heating fluid exits the drying chamber in a comparatively cool state and is conveyed by the heating fluid recirculation system to the regenerator. The heating fluid is preheated in the regenerator by heat exchange with the drying fluid. The regenerator is preferably a shell and tube heat exchanger; however, in some embodiments the regenerator is a heat pump system or a primary tube and shell heat exchanger with an auxiliary heat pump system. It is foreseen that other types of heat transfer regenerators could be used in the various embodiments. The heating fluid can be gaseous (such as air, nitrogen or the like) or liquid (such as oil); however, the heating fluid is often preferably water. In some embodiments a portion of the heating may be accomplished by the heat pump system used to preheat the material to be dried or selected early heating regions. 
     The makeup heater provides heat to the heating fluid to raise the temperature thereof to a preselected range or specific temperature prior to entering the drying chamber. Preferably, the heating fluid recirculation system returns the heating fluid from the regenerator to the drying chamber through the makeup heater; however, heat can be added at other locations such as directly to the material prior to entering the drying chamber, especially by a heat pump system withdrawing residual heat from gas exiting a primary heat exchanger. 
     The drying fluid circulation system circulates a drying fluid sequentially through the drying bays generally in reverse order or counterflow to the flow of material through the drying bays. Preferably, the drying fluid is air and further preferably the drying fluid is ambient air, although other fluids such as nitrogen may be used, if necessitated by the processing needs. The drying fluid must be able to absorb, carry, or take up moisture released by the material. With air as the drying fluid, the air becomes heated as it passes though the material previously heated in the heating regions or by the heating fluid system and becomes saturated or at least partially saturated with moisture. In some embodiments the heating fluid bypasses the drying regions and the drying fluid preferably at least in part bypasses or substantially bypasses the heating regions. In other embodiments heating and drying occur in the same bays or in some common bays. 
     The drying fluid enters the drying chamber in a cool preferably comparatively dry state and exits the drying chamber in a warm wet state. The terms dry and wet are not intended to indicate relative humidity or saturation at a particular temperature, but rather the total moisture content of the drying fluid entering and exiting the drying chamber. That is, the drying fluid contains more total moisture when exiting the drying chamber than when entering the drying chamber. Upon exiting the drying chamber, the drying fluid is transported by the drying fluid circulation system to the regenerator wherein the drying fluid in a warm state transfers heat to the heating fluid that enters the regenerator in a comparatively cool state. In certain embodiments the drying fluid upon exiting the primary regenerator may be passed through a secondary or auxiliary heat pump system to withdraw more heat to transfer to the material being dried. Condensation that collects due to the cooling of the drying fluid in the regenerator is collected and discharged. 
     The drying fluid is most often discharged from the regenerator into the air. However, in some instances the drying fluid may carry too much pollution, such as dust, or may be too expensive to waste and, in such situations, the drying fluid exiting the regenerator may be returned to the drying chamber. In such circumstances a chiller with a condensate drain may be required to chill the drying fluid returning to the drying chamber a small amount to assure that the temperature of the drying fluid is decreased to or maintained at a preselected temperature, such as 70° F., prior to reintroduction to the drying chamber. If the temperature of the recycled drying fluid is not reduced between the regenerator and the drying chamber, the drying potential of the chamber may be markedly decreased. Chilling may be through a refrigeration unit, a heat pump or the like. A heat pump, when used for this purpose, has the advantage of recapturing the energy removed from the recycled drying fluid for reintroduction of the heat to the heating fluid in the region between the regenerator and the makeup heater or to the material to be dried in a preheater prior to the first heating compartment or elsewhere in the drier. 
     The drying fluid flows generally overall counter currently to the flow of material in the drier. However, the drying fluid can be in countercurrent, concurrent, cross, mixed or other flow relative to the material in each individual drying regions or compartment. 
     The drier and drying process of the invention are especially advantageous in consistently and uniformly removing moisture with low stress from a material with a minimal input of heat. Further, the drier and process provide the advantage of being adaptable to a closed system to reduce undesirable emissions to the air. 
     OBJECTS AND ADVANTAGES OF THE INVENTION 
     Therefore, the objects of the invention are: to provide a drier that is highly efficient with respect to use of energy; to provide such a drier wherein heat is recovered and reused; to provide such a drier wherein heating fluid and drying fluid is flowed concurrently, countercurrently, cross, mixed or otherwise through heating compartments and/or drying compartments; to provide such a drier wherein drying fluid exiting the drier is utilized to preheat heating fluid entering the drier; to provide such a drier that is comparatively inexpensive to operate, easy to use and especially well adapted for the intended usage thereof and to provide a process for effectively utilizing such a drier. 
     Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. 
     The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially schematic front elevational view of a first drier in accordance with the present invention. 
         FIG. 2  is an enlarged cross sectional view of a drying chamber of the first drier, taken along line  2 - 2  of  FIG. 1 , with portions broken away to show detail thereof. 
         FIG. 3  is an enlarged cross sectional view of the drying chamber of the first drier, taken along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a partially schematic front elevational view of a second drier in accordance with the present invention. 
         FIG. 5  is an enlarged cross sectional view of a drying chamber of the second drier, taken along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is an enlarged cross sectional view of the drying chamber of the second drier, taken along line  6 - 6  of  FIG. 5 . 
         FIG. 7  is a partially schematic front elevational view of a third drier in accordance with the present invention. 
         FIG. 8  is an enlarged cross sectional view of a drying chamber of the third drier, taken along line  8 - 8  of  FIG. 7 . 
         FIG. 9  is an enlarged cross sectional view of the drying chamber of the third drier, taken along line  9 - 9  of  FIG. 8 . 
         FIG. 10  is a partially schematic front elevational view of a fourth drier in accordance with the present invention. 
         FIG. 11  is a partially schematic front elevational view of a fifth drier in accordance with the present invention. 
         FIG. 12  is a partially schematic front elevational view of a sixth drier in accordance with the present invention. 
         FIG. 13  is a partially schematic front elevational view of a seventh drier in accordance with the present invention. 
         FIG. 14  is a partially schematic front elevational view of an eighth drier in accordance with the present invention. 
         FIG. 15  is a partially schematic front elevational view of a ninth drier in accordance with the present invention. 
         FIG. 16  is a schematic drawing showing flow that is generally countercurrent, but sectionally concurrent. 
         FIG. 17  is a schematic drawing showing flow that is generally countercurrent, but sectionally cross flow. 
         FIG. 18  is a schematic drawing showing flow that is generally countercurrent, but that is sectionally mixed flow. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     Shown in  FIGS. 1 to 3  is a drier in accordance with the present invention that is generally indicated by the reference numeral  1 . 
     The drier  1  includes a drying chamber  5 , a heating fluid recirculation system  6 , a drying fluid circulation system  7 , a regenerator  8  and a makeup heater  9 . 
     The drying chamber  5  includes a vertical column  10  having an upper inlet end  11  and a lower outlet end  12 . Material to be dried and generally indicated by downward directed arrows labeled  14  throughout the chamber  5  flows into the inlet end  11  and through the chamber  5  due to gravity and out the outlet end  12 . 
     The chamber  5  includes an upper section  21  and a lower section  22 . Both sections  21  and  22  are subdivided into equal numbers of regions that in the lower section  22  are alternatively drying regions  23  and heating regions  24 . The upper section  21  is divided also into heating regions  25  and steeping regions  26 . It is foreseen that vibratory mechanisms rotating paddles and the like may be located in the vertical column to aid the flow of material therethrough. 
     The heating fluid recirculation system  6  includes or conduit or piping  27  located within each heating region  24  and conduit or piping  28  located in each heating region  25  and positioned so as to be adjacent to the material  14  therein. A discharge conduit  29  with a pump  30  joins the conduit  27  with a tube side  31  of the regenerator  8 . A second conduit  32  flow connects the conduit  28  with the pump  30 . The regenerator  8  is flow connected with the makeup heater  9  by a conduit  35  and the makeup heater  9  which in turn flow connects with the conduits  25  and  26  of the heating regions respectfully through conduit  37 . 
     The drying fluid circulation system  7  includes an inlet  40  for drawing drying fluid identified by the reference arrow  42  throughout the drier  1  into the chamber  5  by operation of a blower or fan  44 . In the drier  1  the drying fluid is circulated by blowers  50  in each heating region  24  and through the material  14  that is held in the central part of the column  10  by screens  55  in each heating region  24 . Drying fluid  42 , after generally flowing counter current to the material  14  in the lower section  21  and picking up moisture therein while becoming warmer, is discharged from the chamber  5  through an outlet conduit  58  which flow connects with a shell side  59  of the regenerator  8 . The drying fluid  42  exits the regenerator  8  through an outlet  60 . The shell side  59  of the regenerator  8  also collects condensate that is discharged through a drain  61 . The drying fluid  42  flows generally counter current to the material in the lower section  22 , but flows also in a mixed cross flow in each of the heating regions  24 . 
     In the upper section  21  the drying fluid generally flows in cross flow past the heating conduits  27  to transfer heat from the heating fluid flowing counter currently to the material  14  in the upper section  21 . 
     In this manner, the material  14  flows generally overall countercurrently with respect to the heating fluid in the upper section  21  and concurrently with the heating fluid through the lower section  22  while in the chamber  5 , although it is foreseen that the actual segment of flow in each heating region may be concurrent, cross flow, countercurrent or mixed flow. The flow of drying fluid  42  overall is generally countercurrent to the flow of material  14  in the lower section  22 , but is generally cross flow within each separate heating region  24 . The drying fluid  42  exiting the chamber  5  is utilized to preheat the heating fluid in the regenerator  8  and makeup heat is added to the heating fluid in the makeup heater  9 . 
     It is foreseen in some instances that drying fluid from the regenerator  8  may be recycled through a chiller by a conduit (now shown) and returned to the inlet  40  to maintain a generally uniform temperature of drying fluid  42  entering the chamber  5  while reusing the drying fluid  42 . It is foreseen that a heat pump may be used instead of a heat exchanger for the regenerator or for a chiller with heat transferred from the heat pump to the heating fluid and/or directly to the material  14  to be dried. 
     It is foreseen that the regenerator used in any embodiment herein may be other than a shell and tube heat exchanger, and may be any type of exchangers that is capable of transferring heat from the drying fluid to the heating fluid function within the scope of the invention. 
     While a continuous counter flow process is described for the drying chamber and the regeneration systems in the embodiments described, it is foreseen that batch processes could be utilized using one or a series of sequential batch operations. 
     It is foreseen that in addition to gravity conveyance of the material to be dried through the chamber may be aided by other types of conveyance systems including, but not limited to augers, belts and the like. It is foreseen that the overall drying chamber can be of a wide variety of shapes and sizes so as to provide for the required flow of material to be dried. 
     While air and nitrogen are the most likely fluids to be used in a process of this type, it is foreseen that other fluids such as argon or the like may be used. Furthermore, while particular materials to be dried are generally mentioned herein, it is foreseen that a wide variety of materials may be dried, including particulates and other granular materials, powders, flakes, pastes, slurries, and solids in general. Such materials are not restricted to but may be represented by foodstuffs, such as grains, including corn, beans, dog food, mixes, meals and flours; chemicals such as clays, coals, sand; and processed materials, such as paper and the like. 
     It is foreseen that the drying chamber and the regenerator can be operated under vacuum or pressurized in certain embodiments with or without heating the material to be dried to higher temperature. 
     As used herein the phrase “substantially overall counter currently” with respect to flow of the material to be dried and/or the heating fluid relative to the drying fluid, means that both the material and heating fluid enter the chamber at or near one end and exit the chamber near at or near the other end and that the drying fluid enters the chamber at or near the exit of the material and exits at or near the entry of the material, but during travel through the chamber, segments or portions of the drying fluid may flow in cross flow, counter current flow, concurrent flow or mixed flow relative to the material and/or the heating. The term “near” does not mean exactly at one end, but rather closer to such end than the other end. 
     As used herein the phrase “substantially overall concurrently” with respect to flow of the heating fluid relative to the material to be dried, means that both enter the chamber near one end and exit the chamber near the opposite end but during travel through the chamber, segments or portions of the drying fluid may flow in cross flow, counter current flow, concurrent flow or mixed flow relative to the material. 
     Illustrated in  FIGS. 4 to 6  is a second drier in accordance with the present invention generally indicated by the reference numeral  100 . The drier  100  is for drying a material indicated by x&#39;s and thick arrows and is indicated by the reference numeral  102 . The drier  100  comprises a vertically aligned drying chamber  105 , a heating fluid recirculation system  106 , a drying fluid circulation system  107 , a regenerator  108  and a makeup heater  109 . 
     The drying chamber  105  is bifurcated into spaced first and second portions  115  and  116 . Material  102  to be dried is fed by a feeder  117  at the top of the chamber  105  into each of the portions  115  and  116  through which the material  102  descends principally due to gravity to a discharge apparatus  118  which controls the speed of descent of the material  102  through the chamber  105 . Porous side walls  120  of each of the chamber portions  115  and  116  are formed of screen mesh, perforated metal or the like that allows the passage of a fluid, especially air, therethrough, but which maintains the material  102  in the chamber portions  115  and  116 . 
     The chamber  5  outside the portions  115  and  116  is segregated into a series of stacked bays  114 . In each bay  114  and located between the chamber portions  115  and  116  is a channel  125  that flow connects with adjacent areas of the chamber portions  115  and  116  through the porous side walls  120  in which fans  126  are mounted. The chamber portions  115  and  116  are also flow connected to exterior channels  130  through the outer side walls  120  and also with the fans  126  located in a cross channel  127 . In this manner, the fans  126  create drying fluid flow through the material and associated channels  125 ,  127  and  126  in a continuous circulating loop in each bay  114 . 
     The heating fluid system  106  comprises recirculation conduit  132  and a pump  133 . The conduit  132  includes a first pipe  134  flow connecting the pump  133  with a tube side of the regenerator  108 , a second pipe  135  flow connecting the regenerator  108  with the make up heater  109  and a third pipe  136  flow connecting the make up heater  109  to the chamber  105  at a bifurcation  137 . At the bifurcation  137  a fourth pipe  139  flow connects with the third pipe  136  and follows a pathway downward through a majority of the chamber  105  with a serpentine loop  140  located at the intersection of the channels  125  and  127  such that the respective fans  126  urge gaseous drying fluid flow past the loops  140  so as to heat the gaseous drying fluid  155  from the heating fluid and therefrom heat the material  102  that the gaseous fluid recirculates through. 
     The fourth pipe  139  exits near the lower end of the chamber  105  and flow connects with the pump  133 . 
     A fifth pipe  144  flow connects with the bifurcation  137  and enters the chamber  105  near the upper end thereof and in this embodiment where an upper two bays  146  out of a total of fifteen bays  146  are located, each bay  146  being associated with a fan  125  and respective channels  125 ,  127  and  130 . The fifth pipe  144  also has respective serpentine loops  148  positioned to receive flow of gaseous fluid as circulated by the fan  126  in each upper bay  146 . The fifth pipe  144  exits the chamber  105  near the upper end thereof and returns to the pump  133 . Thus, the pump  133  pumps heating fluid generally counter flow to the material  102  in the two upper bays  146  and generally concurrent flow with the material  102  in the thirteen lower bays  114 . The heating fluid is heated while passing through the regenerator  108  and make up heater  109  to a preselected temperature. 
     The drying fluid circulation system  107  draws drying fluid, which in this embodiment is ambient air in through an intake  150  located in the lower end of the chamber  105  utilizing a fan  151 . The drying fluid flow is designated by arrows  155 . The drying fluid  155  flows both in a recycle path through each bay  114  and  146  while passing through and heating the material  102  in a cross flow while also flowing upwardly through the lower thirteen bays  114  and exiting the chamber  105  through an outlet pipe  160 . The outlet pipe  160  flow connects the drying fluid  155  with a shell side of the regenerator  108  wherein the drying fluid exchanges heat with and heats the heating fluid. The drying fluid  155  flows from the regenerator  108  through a discharge  162  and condensation collected in the regenerator  108  drains through a drain  163 . While in the chamber  105  the drying fluid  155  removes moisture from the material  102  while becoming heated above the temperature thereof at the entrance into the chamber  105 . 
     The drying fluid  155  also circulates through the material  102  in the top two bays  146 ; however, in the top two bays  146  the function of the drying fluid is only minimally to dry, but mainly to convey heat by convection from the heating fluid recirculation system to the material  102  so as to somewhat preheat and steep the material  102 . 
     Illustrated in  FIGS. 7 ,  8  and  9  is a third embodiment of a drier in accordance with the present invention generally indicated by the reference numeral  200  for drying a material  202  indicated by dots and dark flow arrows. The drier  200  includes a drying chamber  205 , a heating recirculation system  206 , a drying fluid circulation system  207 , a regenerator  208  and a makeup heater  209 . 
     The drier  200  differs from the previous drier  100  in that the steeping bays of the prior embodiment are not included and there are alternating heating and drying regions in drier  200 . 
     In particular, the chamber  205  has alternating vertical regions with the lowest being a drying region  210 , the next a heating region  211  and subsequent alternation of drying and heating regions  210  and  211 . Each of the regions  210  and  211  include bays  214 . There are two bays  214  in each drying region  210  and three bays  214  in each heating region  211 . 
     The chamber  205  includes two spaced columns or portions  215  and  216  through which the material  202  flows after entering the chamber  215  through feed mechanism  220 . The material  202  flows mainly due to gravity down through the chamber  205  under control of a discharge mechanism  221  and agitators  222 . 
     Each bay  214  includes an inner channel  225  located between the portions  215  and  216  and separated therefrom by a porous divider wall or screen  226 . An outer set of channels  228  is also separated from the material  202  in the chamber portions  215  and  216  by a porous divider wall or screen  230 . The channels  225  and  228  are joined in the heating region bays  214  by a cross channel  231  within which a gaseous fluid driving fan  232  is located for circulating the fluid through the heating region bays  214  and the material  202  therein. 
     The heating recirculation system  206  includes a fluid pump  235  and an interconnected flow conduit  236 . The conduit  236  includes a first pipe  240  flow joining the pump  206  to a tube side of a heat exchanger of the regenerator  208 , a second pipe  241  joining the regenerator with the makeup heater  209  and a third pipe  242  discharging from the makeup heater  209  and splitting into three sub pipes  244 ,  245  and  246  each of which enter the chamber  205  in a heating region  211 . 
     The sub pipes  244 ,  245  and  246  each circulate through each bay  214  in a respective heating region  211 . The sub pipes  244 ,  245  and  246  each have serpentine regions  250  that are positioned to receive gaseous fluid flow from respective fans  232  which is heated thereby and in turn heats the material  202  as the drying fluid, represented by arrows  255 , circulates in the bays  214  associated with the heating regions  211 . The sub pipes  244 ,  245  and  246  join in pipe  256  and the heating fluid therein is returned to the pump  206 . The heating fluid, as indicated by arrows  257 , thus starts at the pump  206  relatively cool, is heated in the regenerator  208 , is thereafter heated in the makeup heater  209  to a preselected temperature, for example 140 to 170° F. depending on the material  202  being dried, after which the heating fluid  257  enters the heating regions  211  and heats the gaseous drying fluid  255  therein which in turn heats the material  202 . The heating fluid  257 , at this point in a comparatively cooler state, for example 75°, returns to the pump  206 . 
     The drying fluid  255 , here gaseous and especially ambient air, enters the drying chamber  205  through multiple vertically spaced inlets  260  of the drying fluid recirculation system  207 . Each of the inlets  260  is associated with a drying region  210  and in the illustrated embodiment there are three. 
     The drying fluid  255 , initially at a comparatively cool temperature especially ambient temperature, for example 70° F., passes upward through the material  202  in respective drying regions  210  and then exits the chamber  205  through outlets  270  after the drying fluid  255  becomes warmer and at least partially saturated with moisture from the material  202 . The exiting drying fluid  255 , for example may be at 140° F., but the temperature can vary so as to be warmer or cooler depending upon the type of material  202  being dried. The outlets  270  are joined into a pipe  272  which flows into a shell side of the regenerator  208  wherein the drying fluid  255  heats the heating fluid  257  and exits an outlet  274 . Condensate is drained from the regenerator  208  through a drain  275 . 
     Shown in  FIG. 10  is a fourth embodiment of a drier in accordance with the present invention generally indicated by the reference numeral  300  for drying material  302 . The drier  300  includes a drying chamber  305 , a heating fluid recirculation system  306 , a drying fluid circulation system  307 , a regenerator system  308  and a makeup heater system  309 . 
     The drier  300  is similar in many respects to drier  100  so repetitive parts will not be described in detail and reference is made to drier  100  for greater explanation of common elements. 
     The drier  300  differs from drier  100  mainly in that the drier  300  uses a different regenerator  308  and a slightly different heat recirculation system  306 . 
     The heat recirculation system includes a fluid reservoir  380  that holds excess heating fluid  381 . Heating fluid piping  383  from the reservoir  380  diverges into sub pipes  385  and  386  each having a pump  387  and  388  and a makeup heater  390  and  391  respectively. The sub pipe  385  feeds the upper heating fluid requirements of a heating zone  393  (top three bays  394  of the chamber  305 ) and sub pipe  386  feeds remaining bays  395  of a lower drying zone  397 . 
     In this manner, the heating fluid can be maintained at different temperatures at the entry to the zones  393  and  397 . The heating fluid pipes  385  and  386  rejoin and return to the reservoir  381 . 
     The regenerator  308  of this embodiment is generally a heat pump  398  as opposed to a tube and shell heat exchanger of drier  100 . The heat pump  398  includes a condensing coil  399   a  for heating the heating fluid, an evaporator coil  399   b  for removing heat from the drying fluid after passage through the chamber  305  and a pump  399   c  for circulating heat pump fluid between the coils  399  a and b. 
     Shown in  FIG. 11  is a fifth embodiment of a drier in accordance with the present invention generally indicated by the reference numeral  400  for drying a material  402 . The drier  400  has a heating chamber  405 , a heating fluid recirculation system  406 , a drying fluid circulation system  407 , a regenerator  408  and a makeup heater  409 . Many aspects of the drier  400  are the same as driers  100  and  300 , so certain redundant elements will not be discussed in detail, rather reference is made to the earlier driers  100  and  300  for additional explanation. 
     The drier  400  differs from the driers  100  and  300  principally with respect to the manner in which an upper heating zone  470  of the chamber  405  is heated and that the regenerator heat exchanger of drier  100  is supplemented or augmented by a heat pump system  472 . The heat recirculating system  406  is utilized to circulate heating fluid through a lower combined heating and drying zone  473  of the chamber  405  and then through the regenerator  408  for partially reheating the heating fluid. The drying fluid exiting the regenerator  408  is conveyed by a pipe  475  to a second auxiliary regenerator  476  wherein an evaporator coil of the heat pump system  472  removes additional residual heat from the exhaust leaving the regenerator  408 . The heat pump system  472  includes condensation coils  480  and a pump  481  for circulating fluid between the condensation coils  480  and the evaporator coil  476 . The condensation coils  480  are placed in the circulating path of fans  481  so as to transfer heat from the fluid therein to the fluid being circulated in the heating zone  470  thereby preheating the material  402  from heat scavenged from the drying fluid exiting the regenerator  408 . It is foreseen that a second heat pump could be used in place of the regenerator  408  to perform the same function. 
       FIG. 12  illustrates a sixth embodiment of a direr in accordance with the present invention generally designated by the reference numeral  500 . The drier  500  has a chamber  505 , a heating fluid recirculation system  506 , a drying fluid circulation system  507 , a regenerator  508 , a makeup heater  509  and a heat pump system  572 . The drier  500  is substantially equivalent in many aspects to driers  200  and  400  and other previous driers and attention is directed to the previous driers for description of additional detail that is not repeated with respect to this embodiment. 
     In this embodiment there is the option for multiple heating regions  570  and alternating multiple drying regions  571  as in drier  200  in the upper part of chamber  505 . The lower part of the chamber  505  is similar to drier  300  wherein the heating fluid system  506  flows heated fluid through a plurality of bays  514  to heat the material  502  concurrently while drying fluid is conveyed by the drying fluid system  507  countercurrently relative to the material  502 . 
     In the upper part of the chamber  505 , the heat pump system  572  is utilized to heat material  502  in the heating regions  570  and drying fluid in passed through the drying regions  572 . The heat pump system  572  removes residual heat from drying fluid exiting the regenerator  508 . The present embodiment shows two pairs of heating and drying regions  570  and  572  in the upper part of the chamber  505  (one in solid lines and one in phantom lines), but the number can be increased as need be for the material  502  being dried and in view of the heat available from the heat pump system  572 . 
     Shown in  FIG. 13  is a seventh embodiment of a drier in accordance with the present invention generally designated by the reference numeral  600 . The drier  600  includes a drying chamber  605 , a heating fluid recirculation system  606 , a drying fluid circulation system  607 , a regenerator  608 , a makeup heater  609  and an auxiliary heat pump system  672 . The drier  600  is similar to drier  200  and includes elements shown in drier  400  as well as other previous driers, consequently elements previously shown and described will not be described in detail and reference is made to the earlier embodiments for greater detail. 
     In the drier  600  there are alternating heating regions  610  and drying regions  611  as in drier  200 . The difference with drier  200  is that the heat pump system  627  removes residual heat from the drying fluid exiting the regenerator  680  and utilizes that heat to preheat the material  602  in the top heating region  610 , as is done with drier  400 . 
     Illustrated in  FIG. 14  is an eighth embodiment of a drier in accordance with the present invention that is indicated by the reference numeral  700 . The drier  700  includes a drying chamber  705 , a heating fluid recirculating system  706 , a drying fluid circulation system  707 , a regenerator  708 , a makeup heater  709  and an auxiliary regenerating heat pump system  727 . This drier  700  is similar to the previous drier  200  and other embodiments such that common details will not be repeated. Reference is made to the earlier embodiments for additional information. 
     In drier  700  there are multiple pairs of heating regions  711  and drying regions  710  that alternate. In a lower part  720  of the chamber  705  the heating fluid is supplied from the regenerator  708 . In an upper part  721  of the chamber  705 , the heating fluid is supplied from the heat pump system  727  that withdraws residual heat from drying fluid being discharged from the regenerator  708 . As many heating region  711  and drying region  710  combination units may be utilized in the chamber  705  to make best use of the heat available from the regenerator  708  and the heat pump system  727   
     Illustrated in  FIG. 15  is an eighth embodiment of a drier in accordance with the present invention that is indicated by the reference numeral  800 . The drier  800  includes a drying chamber  805 , a heating fluid system  806 , a drying fluid system  807 , a regenerator  808  and a makeup heater  809 . This drier  800  is similar to the previous drier  200  and other embodiments such that common details will not be repeated. Reference is made to the earlier embodiments for additional information. 
     Drier  800  is similar to drier  200  except that instead of use of a tube and shell heat exchanger for the regenerator  808 , a heat pump system  827  is utilized for this purpose. The heat pump system  827  has an evaporation coil  860  that removes heat from the drying fluid existing the chamber  805 , a pump  861  that pumps fluid in the system  827  and a condensing coil  862  that transfers heat to the heating fluid that has exited the chamber  805 . The heating fluid is thereafter used to heat material  702  in heating regions  711  that alternate with drying regions  710 . 
       FIGS. 16 ,  17  and  18  are utilized to illustrate the concepts of having overall generally countercurrent flow, but having countercurrent, concurrent, cross or mixed flows within subregions. 
       FIG. 16  shows a drying chamber  900  having regions  901 ,  902  and  903 . Flow of material is indicated by arrow  905  and flow of drying fluid is indicated by arrow  906 . Within each region  901 ,  902  and  903  drying fluid flow  906  is concurrent with respect to material flow  905 , but overall drying fluid flow  906  is countercurrent to material flow  905 . 
       FIG. 17  shows a drying chamber  920  having regions  920 ,  921  and  922 . Flow of material is indicated by arrow  930  and flow of drying fluid is indicated by arrow  931 . Within each region  920 ,  921  and  922  drying fluid flow  931  is cross flow with respect to material flow  930 , but overall drying fluid flow  931  is countercurrent to material flow  930 . 
       FIG. 18  shows a drying chamber  950  having regions  951 ,  952  and  953 . Flow of material is indicated by arrow  960  and flow of drying fluid is indicated by arrow  961 . Within each region  951 ,  952  and  953  drying fluid flow  906  is countercurrent, cross and concurrent flow with respect to material flow  960 , but overall drying fluid flow  960  is countercurrent to material flow  966 . 
     It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.