Abstract:
A method and apparatus for heating materials is described. The apparatus is a furnace that includes multiple gravity-feed trays and a heat transfer fluid that heats material by the heat evolved during phase change. The apparatus also includes moving paddles that urge the material through each tray. The method provides for the torrefying of the material using a phase-change heat-transfer fluid by providing the material sequentially to at least two trays, where the at least two trays are substantially horizontal and disposed at different vertical heights; condensing the vapor phase at a temperature; and providing heat from the condensing the vapor phase to the material, where the temperature is sufficient to torrefy the material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/654,014, filed May 31, 2012, hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to dryers, and more particularly to a method and system for drying solid material 
         [0004]    2. Discussion of the Background 
         [0005]    Existing dryers and roasters either transfer heat directly (when the heat transfer medium is in contact with and mixes with the process materials and products), or indirectly (when the heat exchange medium remains separated from the process materials and process products). 
         [0006]    The direct heating approach benefits from low thermal resistance and high surface area contact, often with high driving temperatures. If the heat transfer medium is hot air, the risk of fire or partial combustion exists, placing limits on the driving temperature. These limits may be overcome by either using an inert gas or oxygen depleted combustion gas as the heat transfer medium; however this leads to a more complicated system. 
         [0007]    In any case, the gases produced, which includes steam and combustible gases, are mixed with the heat exchange medium. A combustion system to use the chemical energy in the gases (to create process heat) becomes problematic because of the low Btu value of the mixed gas. 
         [0008]    The indirect heating approach benefits from the high Btu value of the produced gases, having not been diluted into the heat transfer medium. This allows the gases to be combusted at high temperatures, ultimately providing a superior heating source. The process materials are more easily kept in an oxygen depleted or oxygen free environment. 
         [0009]    Thus there is a need in the art for a method and apparatus that permits the more efficient use of material and energy in the drying of solid materials. Such a method and apparatus should be compact, easy to control, and be relatively maintenance-free. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention overcomes the disadvantages of prior art by using a furnace that utilizes a phase-change heat transfer fluid to heat a material. 
         [0011]    It is one aspect of the present invention to provide a furnace having an input adapted to accept a material to be processed, an output adapted to provide processed material. The furnace includes a first volume and a second volume. The first volume contains a fluid, where the fluid is a phase-change heat-transfer fluid, and where the fluid includes a vapor of the fluid and a liquid of the fluid. The second volume contains the material to be processed. The first volume and the second volume have a separating wall that is a fluid barrier between the first volume and the second volume and which provides for heat transfer between condensing vapor of the fluid and material contained within the second volume. The second volume includes at least two trays, where said at least two trays are substantially horizontal and disposed at different vertical heights, and at least one passageway between two of said at least two trays. 
         [0012]    It is another aspect of the present invention to provide a method of torrefying a material using a fluid, where the fluid is a phase-change heat-transfer fluid and includes a liquid phase of the fluid and a vapor phase of the fluid. The method includes providing the material sequentially to at least two trays, where said at least two trays are substantially horizontal and disposed at different vertical heights; condensing the vapor phase at a temperature; and providing heat from said condensing the vapor phase to the material. The temperature is sufficient to torrefy the material. 
         [0013]    These features together with the various ancillary provisions and features which will become apparent to those skilled in the art from the following detailed description, are attained by the furnace of the present invention, preferred embodiments thereof being shown with reference to the accompanying drawings, by way of example only, wherein: 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]      FIG. 1  is a schematic of a first embodiment furnace; 
           [0015]      FIG. 2  is a perspective view of the furnace of  FIG. 1 ; 
           [0016]      FIG. 3  is a sectional view  3 - 3  of a first embodiment heater and vaporizer of  FIG. 2 ; 
           [0017]      FIG. 4  is a sectional view  4 - 4  of the heater and vaporizer of  FIG. 3 ; 
           [0018]      FIG. 5  is a detailed view of the heater of  FIG. 3 ; 
           [0019]      FIG. 6  is a sectional view  6 - 6  of a heater tray of  FIG. 5 ; 
           [0020]      FIG. 7  is a sectional view  7 - 7  the region between two heater trays of  FIG. 5 ; 
           [0021]      FIG. 8  is a sectional view  8 - 8  of a heater tray of  FIG. 5 ; 
           [0022]      FIG. 9  is a sectional view  9 - 9  the region between two heater trays of  FIG. 5 ; 
           [0023]      FIG. 10  is an exploded sectional view of a portion of the heater of  FIG. 3 ; and 
           [0024]      FIGS. 11A and 11B  are a top and side view, respectively, of the paddle of the heater tray of  FIG. 6 ; 
           [0025]      FIGS. 11C and 11D  are a top and side view, respectively, of the paddle of the heater tray of  FIG. 8 ; and 
           [0026]      FIG. 12  is a sectional view  12 - 12  of the vaporizer of  FIG. 4 . 
       
    
    
       [0027]    Reference symbols are used in the Figures to indicate certain components, aspects or features shown therein, with reference symbols common to more than one Figure indicating like components, aspects or features shown therein. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0028]      FIGS. 1 and 2  are a schematic and a perspective view, respectively, of a first embodiment furnace  100 , which includes a heater  110 , a vaporizer  120 , a preheater  130 , and a heat source  140 . Furnace  100  also includes a first blower  101  to provide air to preheater  130 , a second blower  103  to provide auxiliary air to heat source  140 , and several outputs through which gases exit to the environment: a first stack  105  for reaction products from preheater  130 , a second stack  107  for reaction products from heat source  140 , and an optional port  119  for primarily humid air from heater  110 . 
         [0029]    Furnace  100  is particularly well suited to the heating of material M at a controlled temperature and environment. The material is shown as an input and output to heater  110  as an input Mi and an output Mo, respectively. Examples of material M include, but are not limited to, forest product residuals, agricultural residuals, and foodstuffs (ie. raw, coffee beans, cocoa, grains, etc.). The processed (heated) material may be used in a variety of uses including, but not limited to biofuels, filler for plastics, or food products. In certain embodiments, material M is processed to drive off volatile compounds that have a heating value that may be used to drive the processing of the material. 
         [0030]      FIG. 1  also illustrates that furnace  100  may include other optional devices that are shown, without limitation, as one or more of dryer  20 , coolers  30  or  40 , press  150 , heat transfer loop  50 , one or more load locks  62 ,  64  and diagnostics  160 . Examples of dryers and coolers used in the processing of material M, are shown, for example and without limitation, in co-owned U.S. patent application Ser. No. 13/221,497 filed on Aug. 30, 2011 and published as United States Patent Publication No. 2012-0117815 (the &#39;497 application), U.S. patent application Ser. No. 13/042,356 filed on Mar. 7, 2011 and published as United States Patent Publication No. 2011-0214343 (the &#39;356 application), and U.S. patent application Ser. No. 12/576,157 filed on Oct. 8, 2009 and published as United States Patent Publication No. 2010-0101141 (the &#39;157 application), the contents of which are hereby incorporated by reference. 
         [0031]    Thus, for example and without limitation: dryer  20  of the present application could be dryer reactor 320 of the &#39;157 application, biomass dryer 310 of the &#39;356 or &#39;497 applications; cooler  30  or  40  of the present application could be cooling reactor 340 of the &#39;157 application, biomass cooler 330 of the &#39;356 or &#39;497 applications; press  150  of the present application could be pelletizer 350 of the &#39;157 application, biomass cooler 330 biomass compression portion 340 of the &#39;356 or &#39;497 applications. Furnace  100  may also include additional processing equipment, such as a load-lock to maintain material within volume  112  at a pressure that is higher or lower than atmospheric pressure and as discussed in the &#39;157, &#39;356, and &#39;497 applications, a biomass preparation portion 301 and/or a biomass metering portion 303 of the &#39;356 or &#39;497 applications. 
         [0032]    Material M is indicated at different states or conditions as M 1 , M 2 , M 3 , and M 4 . When dryer  20  is present, M 1  is the input material and Mi is the dried input material. Mo is the heated (torrefied) material, when cooler  30  or  40  are present, M 2  or M 4  are cooled torrefied material, respectively, and if press  150  is present M 3  is densified material. When load locks  62  and/or  64  are present, the pressure P in volume  112  may be greater than or less than atmospheric pressure 
         [0033]    Heater  110  has an outer shell  118  that includes two internal volumes: a volume  112  for conducting a material M, and a volume  114  for containing a heat exchange fluid F. A common wall  116  between volumes  112  and  114  separates the volumes. In general, a material M may be provided to a material input  111 , which passes through volume  112  to a material output  113 , from which heated material M exits furnace  100 . Heat transfer fluid F contained within volume  114  conducts heat through wall  116  to heat, react, or torrefy a material M passing through volume  112 . 
         [0034]    Heater  110  also includes a port  115  for the transfer, both into and from volume  114 , of heat exchange fluid F, and a port  117  in fluid communication with volume  112  (and not volume  114 ) for the exiting of combustible gases from the heated material. Optional port  119  is also in fluid communication with volume  112  (and not volume  114 ) to transport gases that are primarily humid air from heated material M. 
         [0035]    As shown in  FIG. 2 , heater  110  also includes a number of ports  212  that provide access to the volume  112 , where the ports may be used to clean and/or service volume  112 . As shown in  FIG. 2 , several ports  212  are connected by pipes  225  and  227  to port  119  and several other ports  212  are connected by pipes  221  and  223  to port  117 . In certain embodiment, port  119  accumulates gases from the initial heating of material M, which consist primarily of humid air, and port  117  accumulates gases from the later heating of the material, where those gases consist primarily of volatile gases having some heating value which is extracted in heat source  140 . 
         [0036]    Heat exchange fluid F is preferably a phase-change fluid that may be in either a vapor phase V or a liquid phase L. In one embodiment, heat exchange fluid F is DOWTHERM™ A (Dow Chemical Company, Midland, Mich.), an organic heat transfer fluid that is a eutectic mixture of biphenyl (C 12 H 10 ) and diphenyl oxide (C 12 H 10 O). The saturated DOWTHERM™ A vapor has a temperature that ranges from 205° C. at 0.28 atmosphere, 260° C. at one atmosphere, and 305° C. at 2.6 atmospheres of pressure. In a second embodiment, heat exchange fluid F is a parafin fluid, ie. XCELTHERM® XT (Radco Industries, Batavia, Ill.). XCELTHERM® XT can be used for higher temperatures, as it has a higher temperature than DOWTHERM™ A at the same vapor pressure. 
         [0037]    In one embodiment, the pressure PV within volumes  114  and  122  is maintained so that the temperature TV can achieve the proper temperature for material M within volume  112 . Heater  100  may include diagnostics  155  that may be used to monitor the pressure and temperature of fluid F within volume  114 . As shown schematically in  FIG. 1 , heat exchange fluid F from port  115  includes vapor V that rises within volume  114 , condenses on wall  116 , and transfers heat Q through the wall into volume  112 , and thus material M flowing there through. Thus, for example and without limitation, torrefaction of agricultural waste products torrefy in a temperature range of 200° C. to 350° C. By maintaining the pressure of PV DOWTHERM™ A at a pressure of 2.6 bars absolute, and a temperature of 305° C., and heat Q will be transferred into material M in volume  112  at that temperature. If it is determined that the temperature TV is too high for example, then pressure PV can be lowered to lower the vapor temperature of fluid F. 
         [0038]    Heat source  140  has inputs that supply various gases that are reacted with the heat source and outputs that provide hot, reacted gases. In one embodiment heat source  140  provides gases to a thermal oxidizer  143  via an air intake port  149  and a combustible gas intake port  148 . The oxidized gases exit the thermal oxidizer at an output  147 . In another embodiment heat source  140  provides gases to a burner  141  via an auxiliary air input port  142   a  that accepts air from blower  103  and an auxiliary fuel input  142   b  that accepts fuel from an auxiliary fuel source  102 . The combusted gases exit burner  131  at an output  145 . Gases from outputs  145  and  147  are combined and exit heat source  140  at output port  146 . The combined outputs  145  and  147  also exit heat source  140  at a second output port  144 . The flow through second output port  144  is controlled by valve  109  and exits furnace  100  via stack  107 . The gas provided by output port  146  and  144  may thus include reaction products of the thermally oxidized combustible gases and the combusted auxiliary fuel. 
         [0039]    The heat source  140  may, for example and without limitation, be the combined thermal oxidizer/burner fabricated by Clark Griffith Consulting, of Lansdale, Pa. This device includes both burner  141  and thermal oxidizer  143  in one package, allowing for start-up or extra operating temperature with an alternative fuel source  102  (i.e. propane), 
         [0040]    Vaporizer  120  accepts hot gas at a temperature T 1  from output port  146  into an input port  121  and through tubing  125  before exiting the vaporizer at exit port  123  at a lower temperature, T 2 . Vaporizer  120  also includes a volume  122  separate from tubing  125 , which contains a heat exchange fluid F. Volume  122  is in fluid communication with volume  114  of the heater, through ports  115  and  127 , to allow liquid L and vapor V to flow between heater  110  and vaporizer  120 . 
         [0041]    A lower portion of volume  122  includes liquid phase L, and an upper portion of volume  122  includes a combination of liquid phase L and vapor phase V. The gases within tubing  125  provide heat Q to heat liquid L, causing a portion of the liquid to vaporize into vapor V. Heat provided by conduction from the hot gas provided at input port  121  heats the liquid L, which vaporizes at a temperature Tv determined by the pressure of within volume  122  and  114  according to the thermal properties of fluid F. Vapor V in volume  114  condenses on wall  116 , providing heat by conduction at approximately the vaporization temperature Tv of fluid F. 
         [0042]    Preheater  130  has an input port  131  for accepting gas from exit port  123  of vaporizer  120 , an input port  133  for accepting air from a blower  101 , an exit port  137  that provides gas to a stack  105  that exits furnace  100 , and an exit port  135 . Preheater  130  is a heat exchanger that recovers heat not used by vaporizer  120  to preheat air that is provided to thermal oxidizer  143 . 
         [0043]    Preheater  130  may be, for example and without limitation, a flat plate heat exchanger, which is well known in the field, and are manufactured, for example, by Southwest Thermal Technology, Inc, Camarillo, Calif. 
         [0044]    In alternative embodiments, energy may be removed from furnace  100  for other processing or energy production uses. Thus, for example, stack  107  may be replaced with a device for recovering thermal energy and/or optional cooling loop  50  through vapor V may remove heat from fluid F at a temperature TV. Such heat may be used as process heat, as through a heat exchanger, or may be used for generating electricity or mechanical work, as in the power generator 230 of the &#39;356 application, which may include a Rankine cycle (OCR) engine model UTC 2800, manufactured by UTC Power (United Technologies Corporation, South Windsor, Conn.), or a turbine. 
         [0045]      FIG. 2  shows the connections between various components. Thus,  FIG. 2  shows pipe  201 , which connects port  117  with port  148 , pipe  203 , which connects port  131  to port  123 , pipe  205 , which connects port  146  and  121 , pipe  207 , which connects port  135  to port  149 , paddle drive  211 , and access ports  212 . The various blowers, valves, and piping are sized to accommodate the flow of materials and temperatures required. 
         [0046]    The heat exchange fluid is contained within a closed, constant volume within heater  110  and vaporizer  120  and does not mix with either the material that passes though heater  110  or gases from heat source  140 . Furnace  100  thus provides for the indirect heating of material, where the temperature is controlled though the uses of a phase-change heat exchange fluid. 
         [0047]    Furnace  100  may, in certain embodiments, provide material M to a press  150  to compact the heated material. Press  150  may, for example and without limitation, be an extrusion press. As an example, the heated material from output  113  may be first ground, if necessary, to pieces on the order of, for example and without limitation, 5 mm, and subsequently be fed into a screw press, where the material is extruded to the desired format, which may be, for example and without limitation, between 25 mm and 100 mm in diameter. The heated material may then be cooling and stored. By properly coordinating the speed of the extrusion screw with the process material flow, the extrusion screw remains full and the process output is sealed from the environment. 
         [0048]    In certain other embodiments, diagnostics  160  may be utilized to monitor the material before, during or after pressing. Diagnostics  160  may, for example and without limitation, utilize spectroscopy to monitor the densified material M 3 . Examples of such a diagnostic technique are described, for example and without limitation, in the “&#39;497 application, which describes a method of measuring the fuel value and other physical properties of the process products(s) using IR spectroscopy. Thus, for example, an Attenuated Total Reflectance (ATR) crystal may be positioned in the extrusion barrel. The process material is forced against the crystal, and an IR spectrometer continuously records the spectrum. This information may be used to control the process and to provide continuous process history. 
         [0049]    Furnace  100  may also include a computer or other electronic control system  10 . System  10  includes inputs from diagnostics  155  and  160  to acquire data concerning heat transfer fluid F (that is, the pressure Pv and temperature Tv of fluid F within volume  114 ), and processed material M, such as the density, temperature of processed material M, including data from diagnostics  160  Other process information can be made available to the system  10 , including but not limited to, data from an emission analyzer system, (ie. ENERAC of Holbrook, N.Y.) which may include excess Oxygen, CO2 and total combustible gases as measured in stack  107  and/or  105 . Thermocouples and pressure sensors, well known in the art, can be located at various process positions and made accessible to system  10 . System  10  may then provide control signals to blowers  101  and  103 , value  109 , auxiliary fuel source  102 , and paddle drive  211 . 
         [0050]    Details of heater  110  and vaporizer  120  are now described in greater detail, where  FIG. 3  is a sectional view  3 - 3  of a first embodiment heater and vaporizer of  FIG. 2 , and  FIG. 4  is a sectional view  4 - 4  of the heater and vaporizer of  FIG. 3 . As described subsequently in greater detail, heater  110  includes an alternating structure of volumes  112  and  114  to facilitate mixing of material M moving through volume  112  and heat transfer between material M and heat exchange fluid F. Paddle drive  211  is attached to a shaft  301  that also facilitates mixing of the material within volume  112 . 
         [0051]    Heater  120  is shown in greater detail in  FIG. 5  as a detailed view of the heater of  FIG. 3 . Volume  112  includes horizontal trays  510  and  520 , which form wall  116 , and that are alternately arranged vertically and connected by vertical passageways  532 ,  534 . Trays  510  and  520  are generally circular with an outer perimeter  511 ,  521 , respectively, and centerline near or on a centerline C of shaft  301 . Material is provided to each tray  510  from passageway  534  (or input  111 ) near outer perimeter  511 , and exits the tray closer to centerline C into passageway  532 . Material then enters tray  520 , and exits the tray near the outer perimeter  521  to passageway  534 . The material thus flows back and forth, from input  111  to output  113 . 
         [0052]    Trays  510  and  520  are shown in greater detail in  FIGS. 6-10 , where  FIG. 6  is a sectional view  6 - 6  of heater tray  510  of  FIG. 5 ,  FIG. 7  is a sectional view  7 - 7  the region between two heater trays  510 ,  520  of  FIG. 5 ,  FIG. 8  is a sectional view  8 - 8  of heater tray  520  of  FIG. 5 ,  FIG. 9  is a sectional view  9 - 9  the region between two heater trays  520 ,  510  of  FIG. 5 , and  FIG. 10  is an exploded sectional view of a portion of heater  120 . 
         [0053]    The interior of trays  510  and  520  are shown in  FIGS. 6 ,  8 , and  10 . As shown in  FIG. 10 , tray  510  includes an upper portion  1010  that includes an upper wall  1011  having a hole  1013 , outer perimeter  511 , and portion  1015  that transitions to port  212 , and tray  520  includes an upper portion  1020  that includes an upper wall  1021 , outer perimeter  521 , and portion  1025  that transitions to port  212 . As shown in  FIGS. 6 and 8 , each tray  510 ,  520  includes a hole  601 ,  801 , respectively through which material M may exit the tray, a paddle  603 , and  803 , respectively, that is configured to move the material to hole  601 ,  801 , and a bottom  605 ,  805 , on which the material moves. 
         [0054]    Paddles  603 ,  803  move in the same direction, but are oriented relative to shaft  301  to move material toward the differently located holes. The orientation of paddle  603  is shown in  FIGS. 11A and 11B  as a top and side view, respectively, of paddle  603  of the heater tray  510 , and  FIGS. 11C and 11D  are a top and side view, respectively, of paddle  803  of the heater tray  520 . The paddles have a height t of, without limitation of ¼ to 2 inches, and a length R equal to just short of the radius RT of the tray. The paddles and are offset to sweep material into holes  601 ,  801 , respectively. Shaft  301  is sealed with seals  1001  at each surface it crosses, which may include seals into and out of trays  510  and  520 , using methods well known in the art, to keep fluid F and material M separate within heater  110 . 
         [0055]    The space between trays  510 ,  520 , through which fluid F flows in volume  114 , is shown in  FIGS. 7 and 9 . Spacing elements  501  are used to provide structural support to the trays. 
         [0056]    In one embodiment, furnace  100  is sized to process 1000 kg/hr of wood chips. Trays  510  and  520  have a height H of 100 mm, and a radius RT of 1.8 m, and are spaced apart by a distance S of 50 mm. The heater has a radius of RH of 1.9 m, providing a gap RH-RT of 0.1 m for fluid F. Paddle drive  211  is operated to urge the material from one tray to another. In one embodiment, the angle θ is 30 degrees, oriented to move the material towards the open holes at the bottom of trays  510  and  520 , and is rotated at 60 rpm. 
         [0057]      FIG. 12  is a sectional view  12 - 12  of the vaporizer of  FIG. 4 . Tubes  203  and  205  are pipes for transport of fluid F, which may flow through ports  121  and  123 , and then through individual tubes  225 . 
         [0058]    The operation of furnace  100  is illustrated with reference  FIGS. 1-12 . Furnace  100  may be started by system  10  turning on blower  103 , turning off valve  109 , and providing an auxiliary fuel to burner  141 . Combustion products generated in burner  141  are then provided to vaporizer  120 , where they flow through pipes  125 , heating heat exchanger fluid F, and exiting the vaporizer at port  123 . The cooler gases then flow through preheater  130 , where heat is exchanged with air from blower  101 , when that blower is operated. 
         [0059]    Eventually, the temperature of gas entering port  121  is hot enough to vaporize heat exchanger fluid F, and vapor rises from volume  122  of vaporizer  120  into volume  114  of heater  110 . When the temperature Tv, as measured by diagnostics  155 , reaches a set point, furnace  100  is ready to process material M. Blower  101  and paddle drive  211  are turned on by system  10  and material M is provided to input  110 . As material M flows through volume  112 , it is heated and gives off gases that may be recovered. Material M preferably will generate volatile gases which are recovered at port  117  and provided for mixing with preheated air from blower  101  in thermal oxidizer  143 , and the products of oxidization are mixed with those of burner  141  and provided back to vaporizer  120 . 
         [0060]    In certain embodiments, furnace  100  is controlled by system  10 . Thus, for example, if a sufficient amount of combustible gases are provided to thermal oxidizer  143 , then system  10  may reduce the flow of auxiliary fuel  102 , or shut off the auxiliary fuel and blower  103 . If too much heat is generated in heat source  140 , then valve  109  may be partially or fully opened to release heat from furnace  100 . Process parameters determined by diagnostic  160  may be used to increase or decrease heat and/or material flow to maintain desired conditions. 
         [0061]    In certain operating conditions, for instance torrefying a material M that is dry wood, at between 250° C. and 300° C. with a residence time of between 5 and 30 minutes, the product gas has more chemical energy than required by the heating process. If heat is not removed from the system, then the process throughput will be limited, as will the allowable process set points. For oily feedstocks, with rapid processing rates, chemical energy is in significant excess, and recovering this energy is attractive. 
         [0062]    A critical aspect of the indirect heated roaster of heater  110  is the handling of the process off gases, which may contain condensable hydrocarbons (CxHyOz), steam, non-condensable gases, and particulates. A second critical aspect are the methods to provide an oxygen free process, while preventing all off gas leakage to atmosphere. In the present invention, volume  112  of heater  110  can be operated at either ambient pressure, or slightly above ambient pressure (i.e. 4 inches H 2 O), or slightly below ambient pressure. In a preferred embodiment, volume  112  is operated at slightly above the pressure of thermal oxidizer, promoting flow from the volume into heat source  140 . 
         [0063]    Examples of the conditions required for torrefaction of materials is described in the related &#39;497, &#39;356, and &#39;157 applications. More specifically, the following is a table of operating conditions for different feedstock materials M. 
         [0064]    Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments. 
         [0065]    Thus, while there has been described what is believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. Similarly, it should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby expressly incorporated into this description, with each claim standing on its own as a separate embodiment of this invention.