Abstract:
The adjustable heat exchanger provides precise control of oven temperature in a pyrolysis reaction. The heat exchanger includes two sets of hollow non-circular discs, the discs of a movable set being interleaved with the discs of a stationary set. A first working fluid circulates through a heat source oven and through the hollow stationary discs, and a second working fluid circulates through the hollow rotating discs and a pyrolysis oven. The two fluids do not mix with one another, but are always completely separate from one another. Heat transfer depends upon the relative surface area of the rotary discs interleaved between the stationary discs. Minimum heat transfer occurs when the rotary discs are rotated to a position clear of the stationary discs, and maximum heat transfer occurs when the rotary discs are completely interleaved with the stationary discs.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to devices for controlling the temperature of pyrolysis reactions, and particularly to an adjustable heat exchanger having a plurality of alternating discs for transferring heat from one set to the other. 
         [0003]    2. Description Of The Related Art 
         [0004]    Pyrolysis is the process of chemically breaking down or altering a substance by heat in an essentially oxygen-free environment. Pyrolysis is used in the manufacture of various materials and in the production of lighter fractions from crude oil, as well as in other industries. The process often requires very precise control of the temperature during the pyrolysis process in order to achieve the specific chemistry of the desired end result. 
         [0005]    To date it has been extremely difficult to achieve such precisely controlled temperatures (other than in electric ovens), particularly in fluid-based ovens required for successful pyrolysis. Thus, an adjustable heat exchanger solving the aforementioned problems is desired. 
       SUMMARY OF THE INVENTION 
       [0006]    The adjustable heat exchanger provides precise heat transfer, and therefore temperature control, from a high temperature heat source oven to a controlled temperature pyrolysis oven. The heat exchanger has a plurality of fixed discs and a plurality of rotating discs, which are interleaved in an alternating array. Each disc is hollow, and heat transfer fluid circulates therethrough. A first heat transfer fluid circulates from the high temperature heat source oven through the fixed discs, and a second heat transfer fluid circulates through the rotating discs and pyrolysis oven. The two fluids do not mix with one another, but are kept completely separate. Separate pumps are used to circulate the fluids through their respective discs and ovens. Any suitable fluid may be used as the working fluids in the two disc assemblies and their ovens, but helium gas is a preferred fluid, while a lithium-lead compound has been used in certain specialized heat transfer apparatus and applications. 
         [0007]    The two sets of discs are semicircular in shape, and rotation of the rotating discs results in greater or less surface area being exposed beyond the stationary discs. This results in lesser or greater heat transfer between the stationary discs and the rotary discs, respectively. Since the discs are semicircular, the rotation of the rotary discs to a position 180° opposite the fixed discs results in maximal spatial separation between the fixed and rotating discs and minimal heat transfer between the two. Partial rotation of the rotating discs between the fixed discs results in somewhat greater heat transfer, and continued rotation of the rotary discs completely between the fixed discs results in maximum heat transfer from the fixed discs to the rotary discs, and thus to the pyrolysis oven. 
         [0008]    These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a diagrammatic view of an adjustable heat exchanger according to the present invention, illustrating its general configuration and connection to input (high temperature sink) and output (pyrolysis) ovens. 
           [0010]      FIG. 2  is a perspective view of the stationary disc portion of the adjustable heat exchanger of  FIG. 1 . 
           [0011]      FIG. 3  is a perspective view of the rotating disc portion of the adjustable heat exchanger according to  FIG. 1 , the stationary disc portion being shown in broken lines. 
           [0012]      FIG. 4  is a perspective view of an exemplary heat exchanger disc of the adjustable heat exchanger of  FIG. 1 , a portion of one disc face being broken away to show the internal baffle configuration. 
           [0013]      FIG. 5  is a top plan view of the adjustable heat exchanger of  FIG. 1 , illustrating the relationship between the alternating stationary and rotating discs and the interconnection between the discs of each set. 
           [0014]      FIG. 6A  is an end view of the adjustable heat exchanger of  FIG. 1 , showing the rotary discs rotated clear of the stationary discs for minimal heat transfer therebetween. 
           [0015]      FIG. 6B  is an end view of the adjustable heat exchanger of  FIG. 1 , showing the rotary discs partially interleaved with the stationary discs for partial heat transfer therebetween. 
           [0016]      FIG. 6C  is an end view of the adjustable heat exchanger of  FIG. 1 , showing the rotary discs having the majority of their areas interleaved with the stationary discs for relatively high heat transfer therebetween. 
           [0017]      FIG. 6D  is an end view of the adjustable heat exchanger of  FIG. 1 , showing the rotary discs completely interleaved with the stationary discs for maximal heat transfer therebetween. 
       
    
    
       [0018]    Similar reference characters denote corresponding features consistently throughout the attached drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The adjustable heat exchanger provides precise temperature control for pyrolysis reactions involving the breakdown of various organic compounds in a reducing atmosphere. The heat exchanger is disposed between a heat source oven providing relatively higher heat and a pyrolysis oven. Adjusting the heat exchanger provides precise heat transfer from the heat source oven to the pyrolysis oven for precise control of the reactions taking place within the pyrolysis oven. 
         [0020]      FIG. 1  of the drawings provides a schematic view of an exemplary installation of the adjustable heat exchanger  10  in an installation having a first oven or heat source oven  12  and a second oven or pyrolysis oven  14 . The ovens  12  and  14  are shown partially in  FIG. 1  in order to provide a reasonable scale, but it will be understood that each oven  12  and  14  is a closed unit when in operation. Similarly, the heat exchanger  10  is shown open, but it will be understood that it is completely enclosed by a thermally insulated housing  16  when in operation. 
         [0021]    The adjustable heat exchanger  10  contains a first plurality of fixed hollow discs, e.g., discs  18   a  through  18   l,  in a parallel array to one another. The fixed discs  18   a  through  18   l  are spaced apart from one another to allow the placement of a movable disc between each of the fixed discs. A second plurality of mutually parallel, movable hollow discs, e.g.,  20   a  through  20   k,  is disposed in a radial array along a rotating shaft  22 . Other than being fixed to a rotating shaft  22 , the movable discs  20   a  through  20   k  are substantially identical to the fixed discs  18   a  through  18   l.  The movable discs  20   a  through  20   k  are also spaced apart from one another to allow placement of the movable discs between the fixed discs  18   a  through  18   l,  so that the fixed discs  18   a  through  18   l  and the movable discs  20   a  through  20   l  are interleaved with one another in an alternating array when the movable discs  20   a  through  20   l  are rotated between the fixed discs  18   a  through  18   l.    
         [0022]    The spacing between the alternating fixed discs  18   a  through  18   l  and movable discs  20   a  through  20   k  is preferably quite close, leaving just sufficient room or space to preclude physical contact between the fixed and moving discs. This greatly improves the heat transfer between the fixed and moving discs. The discs  18   a  through  18   l  and  20   a  through  20   k  are preferably semicircular in form as shown in the various drawings, but may be any suitable shape or form, so long as rotation of the movable discs  20   a  through  20   k  relative to the stationary discs  18   a  through  18   l  results in variation in the closely adjacent surface area between the stationary and movable discs in order to adjust the heat transfer therebetween. It will be seen that the twelve fixed discs  18   a  through  18   l  and the eleven movable discs  20   a  through  20   k  are exemplary in number, and more or fewer discs may make up each set of fixed and rotating discs, 
         [0023]      FIG. 2  provides a detailed perspective view of the fixed discs  18   a  through  18   l.  Each of the fixed discs includes a central channel  24  therein. The aligned channels  24  of the discs  18   a  through  18   l  provide for the placement of the rotary shaft  22  therein. The shaft  22  is illustrated in  FIGS. 1 ,  3 ,  5 , and  6 A through  6 D of the drawings. The discs  18   a  through  18   l  are supported by legs  26 , which, in turn, rest within the housing  16 , shown in  FIGS. 1 and 5  of the drawings. A plurality of peripherally disposed interconnecting tubes  28  extend between adjacent fixed discs  18   a  through  18   l,  and connect each of the fixed discs in sequence. That is to say, the first fixed disc  18   a  is fluidly connected directly to the second fixed disc  18   b,  the second fixed disc  18   b  communicates fluidly with the third disc  18   c,  and so on, in sequence. Thus, fluid flowing through the first fixed disc  18   a  must flow through the second fixed disc  18   b  in order to reach the third fixed disc  18   c,  etc. 
         [0024]    A similar sequential flow path is provided for the rotary discs  20   a  through  20   k,  as shown in  FIG. 3  of the drawings. The various rotary discs  20   a  through  20   k  are affixed to the shaft  22 , and extend radially therefrom to rotate with the shaft. The heat transfer fluid flows into an axial entry port  30  at one end of the shaft  22 , and thence through a radially disposed passage  32  into a notch or channel  34  formed axially along the length of the shaft. A plurality of lateral ports  36   a  and  36   b  and corresponding transfer tubes  38   a  and  38   b  allow the heat transfer fluid to flow from the shaft channel  34  to each of the rotary discs  20   a  through  20   k,  and back from each of the discs into the channel  34 . A plurality of channel baffles  40   a  through  40   k  extend laterally across the shaft channel  34  to prevent flow of the heat transfer fluid along the channel  34  without passing through each of the discs  20   a  through  20   k  in sequence. 
         [0025]    Thus, the heat transfer fluid enters the entry port  30  of the shaft  22  and flows through the inlet passage  32  into the first or entry end of the channel  34 . The first baffle  40   a  precludes axial travel of the fluid along the channel  34 , so the fluid must flow into the lateral passage  36   a  and corresponding transfer tube  38   a  to the first rotary disc  20   a.  After the fluid flows through the first rotary disc  20   a,  it passes through the transfer tube  38   b  and lateral passage  36   b,  which is on the opposite side of the first baffle  40  from the first lateral passage  36   a.  As the fluid cannot flow back to the first lateral passage due to the first baffle  40   a,  it must flow into the second lateral passage  36   b  and its transfer tube  38   b  to flow into the second rotary disc  20   b.  After flowing through the second rotary disc  20   b,  the fluid flows through the transfer tube and lateral passage into the next channel chamber defined by the first and second baffles  40   a  and  40   b.  The process continues with the heat transfer fluid flowing through each of the rotary discs  20   a  through  20   k,  finally flowing from the last disc  20   k  through the last transfer tube  38   b  and outlet passage  36   b  into the channel  34  between the last baffle  40   k  and the radial exit passage  42  to depart the axial exit port  44  (shown in  FIGS. 1 and 5 ) of the shaft  22 . 
         [0026]    The internal structure of an exemplary one of the discs  18   a  through  18   l  and  20   a  through  20   k  is illustrated in  FIG. 4  of the drawings. This exemplary disc is designated as disc  19  in order to avoid implication that it is a specific member of either the set of fixed discs or rotating discs. However, the structure of the disc  19  of  FIG. 4  is substantially identical to the structures of each of the fixed discs  18   a  through  18   l  and each of the rotating discs  20   a  through  20   k.  All of the fixed and rotary discs, as exemplified by the disc  19 , comprise a thin hollow member having mutually opposed, parallel first and second plates  46   a  and  46   b  defining an interior  48 . The two plates  46   a  and  46   b  are surrounded by a semicircular outer wall  50  that surrounds the outer peripheries  52  of the plates and a wall  54  that extends across the diametric inner peripheries  56  of the two plates  46   a,    46   b  and the central channel  24 . The interior  48  of this closed structure only communicates with the external environment by means of the interconnecting transfer tubes  28  (in the case of the fixed discs  18   a  through  18   l ) or the inlet and outlet transfer tubes  38   a  and  38   b  to and from the shaft  22  (in the case of the rotating discs  20   a  through  20   k ). 
         [0027]    A plurality of baffles are installed within the interior  48  of each of the discs in a radial array. The baffles guide or control the flow of the heat exchange fluid through the discs. All of the baffles are identical to one another, but are designated differently according to their positions within the disc. Each baffle  58   a  of a first plurality of baffles has its inner end  60   a  adjacent the inner periphery of the disc, specifically the portion of the wall  54  forming the channel  24 , its opposite outer end  62   a  being spaced inward from the outer circumferential wall  50  and outer peripheries  52  of the two plates  46   a,    46   b.  Each baffle  58   b  of a second plurality of baffles has its inner end  60   b  spaced apart from the inner portion of the wall  54  forming the channel  24  of the disc, its opposite outer end  62   b  being adjacent to the outer circumferential wall  50  and outer peripheries  52  of the two plates  46   a,    46   b.    
         [0028]    The baffles  58   a  and  58   b  are interleaved with one another in an alternating array in the disc, e.g., a second baffle  58   b,  a first baffle  58   a,  another second baffle  58   b,  another first baffle  58   a,  etc. In this manner, heat exchange fluid entering at one edge of the disc flows generally radially inward and outward between the baffles  58   a  and  58   b  in a sinusoidal path  64  (this path represents the working fluid, e.g., helium, lithium-lead compound, etc.), to exit the disc opposite its entrance point. The baffle arrangement illustrated in the example of  FIG. 4  is exemplary of one of the fixed discs  18   a  through  18   l  where the fluid enters and exits the outer edge of the disc, but it will be seen that the reversal of the locations of the baffles  58   a  and  58   b,  i.e., relocating the baffles  58   a  to the locations illustrated for the baffles  58   b  and vice versa, would provide the desired flow path when the flow enters and exits the disc adjacent the channel  24 , as in the case of the rotating discs  20   a  through  20   k.    
         [0029]      FIGS. 6A through 6D  illustrate the variable relationship between the fixed and rotary discs in providing heat transfer between the two types of discs. In  FIGS. 6A through 6D  the single fixed disc illustrated is designated as disc  18  and represents all of the discs  18   a  through  18   l,  while the single rotating disc is designated as disc  20  and represents all of the rotating discs  20   a  through  20   k.  The various internal baffles are shown in broken lines in both discs  18  and  20 , and the rotating disc  20  is stippled to differentiate it from the fixed disc  18  throughout  FIGS. 6A through 6D . The housing  16  is not shown in  FIGS. 6A through 6D  for clarity in the drawings. 
         [0030]    In  FIG. 6A , the rotating disc  20  is shown rotated 180° from the fixed disc  10 , so that there is no engagement or interleaving between the two discs. This results in minimal heat transfer between the two discs. However, in  FIG. 6B , the rotating disc  20  is shown rotated counterclockwise approximately 30°, thereby engaging about one-sixth of the surface of the rotating disc  20  adjacent the surface of the fixed disc  18  (or, interleaving about one-sixth of the surfaces of the rotating discs  20   a  through  20   k  between the fixed discs  18   a  through  18   l ). This results in some moderate amount of heat transfer between the fixed and rotating discs. 
         [0031]    In  FIG. 6C , the rotating disc  20  has been rotated through about 150° counterclockwise from the initial position shown in  FIG. 6A . This results in about five-sixths of the area of the rotating disc  20  overlapping the fixed disc  18 , and thus producing significantly greater heat transfer than that shown in  FIG. 6B . Finally, in  FIG. 6D  the rotating disc  20  has been rotated through 180° from its initial position, shown in  FIG. 6A , so that the two discs  18  and  20  completely overlap one another in  FIG. 6D . Thus, one hundred percent of their disc surfaces are immediately adjacent one another to produce the maximum amount of heat transfer possible between the two discs. 
         [0032]    Returning to  FIG. 1 , the complete adjustable heat exchanger system is shown diagrammatically. The first or heat source oven  12  provides a source of heat at least slightly greater than that desired for the pyrolysis oven  14 . A first heat transfer fluid, e.g., helium gas or a compound, such as lithium-lead (represented by the flow path  64  shown in  FIG. 4 ), flows from a first fluid supply line  66   a  from the first oven  12  by means of a first fluid pump  68   a,  and thence to an inlet line  70   a  to the first fixed disc  18   a.  This fluid flows through the first fixed disc  18   a  following the sinusoidal path illustrated in  FIG. 4 , and passes to the second fixed disc  18   b  through the peripheral interconnecting tube  28  between the first and second fixed discs  18   a  and  18   b.  The fluid then flows through the sinusoidal path within the second disc  18   b,  thence transferring to the third disc  18   c  by mean of the interconnecting tube between the two discs  18   b  and  18   c.  This flow path continues with the heat transfer fluid flowing through each of the discs in sequence, finally exiting the last fixed disc  18   l  to return to the first oven  12  via the return line  72   a  for reheating in the first oven  12 . 
         [0033]    A second heat transfer fluid, preferably identical to the first fluid flowing through the first oven  12  and fixed or stationary discs  18   a  through  18   l,  flows from the second or pyrolysis oven  14  by means of a second fluid supply line  66   b  and second pump  68   b.  The pump  68   b  pumps the fluid to the entry port  30  of the rotary shaft  22  through a second fluid inlet line  70   b.  The second heat transfer fluid then flows into the channel  24  of the shaft  22  and outward to the first rotating disc  20   a  through the first outlet passage  36   a  and transfer tube  38   a  adjacent the first baffle  40   a,  shown in  FIG. 3  of the drawings. The flow continues in a sinusoidal path defined by the baffles  58   a  and  58   b  as shown in  FIG. 4 , thence passing through the outlet transfer tube  38   b  and passage  36   b  and back into the channel  24  of the shaft between the first and second channel baffles  40   a  and  40   b.  The flow path continues in the same manner, with the heat transfer fluid flowing progressively through each of the stationary or fixed discs  20   b  through  20   k  in sequence. Finally, the heat transfer fluid flows into the channel  24  of the shaft  22  through the last passage  36   b  between the final channel baffle  40   k  and the radially disposed exit passage  42 , as shown in  FIG. 3 , and out the exit port  44  of the shaft  22  to the second return line  72   b  to flow back to the second or pyrolysis oven  14 . 
         [0034]    It will be seen that the two heat transfer fluids, i.e., the first fluid that flows through the first oven  12  and the fixed discs  18   a  through  18   l  and the second fluid that flows through the second oven  14  and the rotating discs  20   a  through  20   k,  never mix, but are maintained completely separate from one another. The essentially constant high heat provided by the first or heat source oven  12  is transferred to the first heat transfer fluid and thence to the fixed discs  18   a  through  18   l,  where the variable interleaving of the rotating discs  20   a  through  20   k  with the first discs provides precise control of the temperature of the second heat transfer fluid that circulates through the rotating discs, and thence to the second or pyrolysis oven  14 . While the system described above provides very precise control of the heat delivered to the pyrolysis oven, it will be seen that certain modifications may be made to the system. For example, the first or heat source oven may be connected to the rotating disc assembly and the second or pyrolysis oven may be connected to the fixed discs, if desired. Also, it will be seen that the twelve fixed discs  18   a  through  18   l  and the eleven rotating discs  20   a  through  20   k  are exemplary in number, and that a greater (or smaller) number of fixed and rotating discs may be assembled to form the adjustable heat exchanger. Also, while two specific examples of heat exchange fluid have been described herein, it will be seen that numerous other fluids may be used. 
         [0035]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.