Patent Abstract:
Chemical processing apparatuses which incorporate a process vessel, such as a crucible or retort, and which include a gas separation or filtration system. Various embodiments incorporate such features as loose filtration material, semi-rigid filtration material, and structured filtration material. The vessel may include material that is a microwave susceptor. Filtration media may be selected so that if it inadvertently mixes with the chemical process or the reaction products of such process, it would not adversely affect the results of the chemical process.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent application claims priority from and is related to U.S. Provisional Patent Application Ser. No. 60/528,369, “Vessel with Filter and Method of Use,” Jonathan S. Morrell, Edward B. Ripley, and David M. Cecala, filed Dec. 10, 2003. This U.S. Provisional Patent Application is incorporated by reference in its entirety herein. 

   The U.S. Government has rights to this invention pursuant to contract number DE-AC05-00OR22800 between the U.S. Department of Energy and BWXT Y-12, L.L.C. 

   FIELD OF THE INVENTION 
   This invention relates to chemical processing apparatuses which incorporate a process vessel, such as a crucible or retort, and which include a gas separation or filtration system. 
   BACKGROUND 
   Many chemical processes result in the creation of gases for which filtration is desired prior to their release to the atmosphere. Various means of trapping or absorbing various components of such gas streams, including particulates, have been developed for this purpose. In some systems granular beds of materials such as activated alumina or molecular sieves are sometimes used to filter the gas stream. Commercial, off-the-shelf high-efficiency particulate air (HEPA) filters are also sometimes used for this purpose. Other systems that may be used include wet scrubbing systems in which gases are dissolved in a fluid, and cold-finger traps where volatile organics are condensed and removed as liquids. However, these systems typically permit off-gas contamination of extensive portions of the processing apparatus. Furthermore, existing systems are generally not compatible with advanced heating technology such as microwave furnaces and infrared heating systems. What is needed, therefore, is an apparatus for processing chemicals that has a self-contained filtration system and that is compatible with advanced process heating devices. 
   SUMMARY 
   Many of the foregoing and other needs are met by an apparatus comprised of a vessel having a base and a wall extending upward from the base. The wall has a lip which defines an opening. The apparatus also includes a cover placed over the opening, the cover having a lateral flange, where the position and dimensions of the lateral flange are of sufficient extent in all lateral directions so that at least the lateral flange substantially overlaps the opening. Loose filtration material is disposed between the lip of the vessel and the lateral flange. In a preferred embodiment, the lip of the vessel has a circumferential groove, the cover has a rim that extends downward from the lateral flange and partially fits into the groove, and the loose filtration material is dispersed in the groove between the bottom of the groove and the rim. 
   In an alternate preferred embodiment, loose filtration material is dispersed on a horizontal surface, a first vessel having an opening is placed with its base on the loose filtration material such that the opening is above the surface of the loose filtration material, and a second inverted vessel having a base and a wall extending downward from the base of the second vessel in its inverted position with the wall having a lip which defines an opening and where the lateral dimensions of the wall are sufficient in all lateral dimensions to permit the second vessel in its inverted position to fit over the first vessel when the second vessel is placed over the first vessel and where the combination of the height of the loose filtration material and the length of the wall of the second inverted vessel are such that substantially all of the circumferential segments of the edge of the lip of the inverted second vessel rest on the loose filtration material. 
   In an alternate embodiment, an apparatus comprises a vessel that is comprised of a material that is a susceptor of microwaves and the vessel has a lip that defines an opening. A cover is placed over the opening, the cover having a lateral flange, where the position and lateral dimensions of the lateral flange are of sufficient extent in all lateral directions to at least substantially overlap the opening in the vessel, and filtration media is disposed between the lip and the lateral flange. 
   In another embodiment, a vessel is used where the vessel is comprised of a material that is a susceptor of microwaves and the vessel has a lip which defines an opening. A cover is placed over the opening, where the cover is sized to be smaller in all lateral dimensions than the opening, and the cover is positioned in the opening, Filtration media is disposed between the lip and the cover. 
   In a further embodiment, the apparatus comprises a vessel that is comprised of a material that is a susceptor of microwaves and where the vessel has a lip which defines an opening, a cover is placed over the opening, where the lateral dimensions of the cover are of sufficient extent in all lateral directions to substantially fill the opening in the vessel and where the cover has a hole established by a cutout edge in the cover, and filtration media is disposed across the hole in the cover. 
   In a further variation, a vessel having an upward wall with a lip that defines an opening is used, where the vessel is comprised of a material that is a susceptor of microwaves, and filtration media is disposed across the opening. 
   In yet another embodiment, the apparatus comprises a vessel that is comprised of material that is a susceptor of microwaves. The vessel has a wall with a longitudinal section with a lip that defines an opening. The wall has a hole established by a cutout edge. The apparatus further comprises a cover placed over the opening, the cover having a lateral flange, where the lateral dimensions of the lateral flange are of sufficient extent in all lateral directions to entirely overlap the opening in the vessel and where the lateral flange is positioned to form a substantially gap-less seal between the lip of the vessel and the cover, and filtration material disposed across the hole. 
   In a different embodiment, a container having a port defined by a cutout edge is used, and a chemically stable filter medium is disposed across the port. 
   In a still further embodiment, the apparatus comprises a container that is comprised of a material that is a susceptor of microwaves and the container has at least one orifice passageway. Semi-rigid filtration material comprised of a chemically stable filter medium is disposed across the orifice passageway. 
   A method according to the invention involves placing a charge in a container which, except for at least one orifice passageway, provides a substantially gas-tight environment. The orifice passageway is substantially filled with filtration media and the container is comprised of material that is a susceptor of microwaves. The method continues with a step of surrounding the container with a thermal insulating casket that is transparent to microwaves. The method then involves exposing the charge, the container, and the casket to microwaves at least until a desired chemical reaction in the charge occurs. 
   An alternate method for chemical processing comprises placing a charge in an apparatus comprising a container. The container comprises a vessel where the vessel is comprised of material that is a susceptor of microwaves and the vessel has a lip which defines an opening. The container further comprises a cover placed over the opening, the cover having a lateral flange. The dimensions of the cover are of sufficient extent in all directions so that at least the lateral flange substantially overlaps the opening in the vessel. The apparatus further comprises filtration media disposed between the lip and the lateral flange. The method concludes with exposing the apparatus to microwaves. 
   Another method for chemical processing comprises placing a charge in an apparatus comprising a vessel where the vessel is comprised of material that is a susceptor of microwaves. The vessel has a lip which defines an opening. The apparatus further comprises a cover placed over the opening, the cover having a lateral flange that is larger in all lateral dimensions than the opening and the cover also has a plug that is smaller than the opening. The plug is positioned in the opening. The apparatus further comprises filtration media disposed between the lip and the cover. The method concludes with exposing the apparatus to microwaves. 
   A further method for chemical processing comprises placing a charge in an apparatus comprising a container. The container comprises a vessel, and the vessel is comprised of material that is a susceptor of microwaves. The vessel has a lip which defines an opening. The container further comprises a cover placed over the opening, where the lateral dimensions of the cover are of sufficient extent in all lateral directions to substantially fill the opening in the vessel, and the cover has a hole established by a cutout edge in the cover, The apparatus further comprises filtration media disposed across the hole in the cover. The method concludes with exposing the apparatus to microwaves. 
   Another method for chemical processing comprises placing a charge in an apparatus comprising a vessel. The vessel has an upward wall with a lip which defines an opening. The vessel is comprised of material that is a susceptor of microwaves. The apparatus further comprises filtration media disposed across the opening. The method concludes with exposing the apparatus to microwaves. 
   In another method for chemical processing the first step comprises placing a charge in an apparatus comprising a container. The container comprises a vessel having a wall with a longitudinal section with a lip which defines an opening. The wall also has a hole established by a cutout edge. Further, the vessel is comprised of material that is a susceptor of microwaves. The container further comprises a cover placed over the opening, the cover having a lateral flange, where the lateral dimensions of the lateral flange are of sufficient extent in all lateral directions to substantially overlap the opening in the vessel and where the lateral flange is positioned to form a substantially gap-less seal between the lip of the vessel and the cover. The apparatus further comprises filtration media disposed across the hole. The method concludes by exposing the apparatus to microwaves. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the invention are apparent by reference to the detailed description in conjunction with the figures, wherein elements are not to scale so as to more clearly show the details, and wherein like reference numbers indicate like elements throughout the several views. It will be understood that the various embodiments shown are intended as examples and do not limit the scope of the invention. 
       FIG. 1  provides a cross-sectional view of a vessel according to one embodiment of the invention.  FIG. 1A  is a top view of the vessel according to  FIG. 1 . 
       FIG. 2  provides a side cross-sectional view of a vessel according to another embodiment of the invention.  FIG. 2A  provides an enlarged cross-sectional view of certain features according to the embodiment of  FIG. 2 .  FIG. 2B  provides a top view of the embodiment of  FIG. 2 .  FIG. 2C  is an enlarged cross-sectional view of certain features of an alternate embodiment. 
       FIG. 3  provides a cross-sectional view of another embodiment of the invention. 
       FIG. 4  provides a cross-sectional view of another embodiment of the invention.  FIG. 4A  provides an enlarged cross-sectional view of certain features of the embodiment of  FIG. 4 . 
       FIG. 5  provides a cross-sectional view of another embodiment of the invention.  FIG. 5A  provides an enlarged cross-sectional view of certain features according to the embodiment of  FIG. 5 .  FIGS. 5B and 5C  provide cross-sectional details of further embodiments, with  FIG. 5C  providing both a side and a top view of an embodiment. 
       FIG. 6  provides a side cross-sectional view and a top view of another embodiment of the invention.  FIG. 6A  provides an enlarged cross-sectional portion of certain features of the embodiment according to  FIG. 6 . 
       FIG. 7  provides a cross-sectional view of another embodiment of the invention.  FIG. 7A  provides an enlarged cross-sectional view of certain features of the embodiment of  FIG. 7 . 
       FIG. 8  provides a cross-sectional view of another embodiment of the invention.  FIG. 8A  provides an enlarged cross-sectional portion of certain features of the embodiment of  FIG. 8 . 
       FIG. 9  is a flow chart of a method according to the invention. 
       FIG. 10  is a flow chart of an alternate method according to the invention. 
       FIG. 11  is a flow chart of an alternate method according to the invention. 
       FIG. 12  is a flow chart of an alternate method according to the invention. 
       FIG. 13  is a flow chart of an alternate method according to the invention. 
       FIG. 14  is a flow chart of an alternate method according to the invention. 
   

   DETAILED DESCRIPTION 
   Described next are several embodiments of this invention. 
     FIG. 1  illustrates a cross-sectional view of one embodiment of this invention. In this and other embodiments, the apparatus resides within an external physical environment which includes a “surrounding atmosphere.” For example, the external physical environment may be the interior of a furnace, and, for example, the surrounding atmosphere may be characterized as a partial atmospheric vacuum, or as an inert gas, or as ambient air. In this particular embodiment a container  100  is comprised of a vessel  10  and a cover  30 . The vessel  10  is comprised of a base  11  and a longitudinal wall  12 . The longitudinal wall  12  is a laterally-enclosed tubular structure which is sealed at one end by the base  11 , and which is typically cylindrical, or conical, or polygonal in shape. For illustrative purposes in this and other figures the vessel is shown to contain a charge  20  which comprises chemicals to be processed using this apparatus. An example of a charge  20  is a mixture of titanium dioxide and lithium powders for which a reduction reaction is desired. In the embodiment of  FIG. 1 , a lip  13  is formed as a lateral extension of the longitudinal wall  12 . In variations of this and other embodiments, a lip may be formed by broadening the thickness of the vessel at the upward end of a longitudinal wall, or by making the entire longitudinal wall sufficiently thick to accomplish the desired functions of a lip. 
   In the embodiment illustrated in  FIG. 1 , the apparatus further comprises a cover  30  which is comprised of a lateral flange  31 , and a plug  32  which, in this embodiment, fits snugly between lateral portions of longitudinal wall  12  that establish lip  13 . In variations of this and other embodiments the plug  32  may fit loosely. In some embodiments, the plug  32  may be eliminated, and lateral flange  31  alone substantially comprises the sealing mechanism of cover  30 .  FIG. 1A  further illustrates the relationship between components of vessel  10 . For simplicity, charge  20  and loose filtration material  40  (to be described later) are not depicted. Viewed as in  FIG. 1A  from above vessel  10  looking down, the only visible features are lip  13  and flange  31 . Lip  13  forms an opening  14  and plug  32  fits loosely into opening  14 . 
   The space between the lateral flange  31  of the cover  30  and the lip  13  as depicted in  FIG. 1  plus the space between opening  14  and plug  32  as depicted in  FIG. 1A , establish an orifice passageway  90 . The orifice passageway ( 90  in this case) provides a path for gasses, vapors, liquids, and particles to enter into or exit from the interior volume  101  of the container  100  as chemical processing of the charge  20  takes place. 
   The container  100  is characterized as having an element or a combination of elements (elements  10  and  30  in this case) which, except for one or more orifice passageways ( 90 , in this case), provide a substantially liquid- and gas-tight environment for the charge  20 . 
   Finally, in this and some other embodiments, loose filtration material  40  is preferably disposed across the orifice passageway  90  depicted in  FIG. 1 , so that it is disposed between the lateral flange  31  of the cover  30  and the lip  13 . Loose filtration material is an example of filtration media. The loose filtration material  40  may consist of various granular, or fibrous, or porous materials, or combinations thereof. Examples of such materials include silica powder, carbon powder, cellulose fibers, and metal filaments. Such material is typically selected for a particular chemical process from various alternatives because the selected material is known to substantially trap selected gases, vapors, liquids, or particles as they pass between the interior volume of the vessel  10  and the external atmosphere, where the passage of such chemicals is not desired. Also, when vessel  10  is heated with microwaves, the loose filtration material prevents escape of metal vapors which may cause arcing or plasma formation in the microwave chamber. Loose filtration material is further characterized by dispersal in a manner where the material is at least partially not constrained in one or more directions either by its own structure or by an external physical structure. For example, in  FIG. 1  the loose filtration material  40  is comprised of loose granules that are not constrained by a physical structure in the radial direction outward from the plug  32 . The intent is that the loose filtration material forms a substantially gap-less porous filter between the lateral flange  31  of the cover and the lip  13 . The term “gap-less porous filter” refers to a configuration where, within the expected operating pressures for the apparatus, if the ambient gas, vapor, or liquid pressure on one side of the filtration media (e.g., loose filtration material  40 , in this case) is higher than the pressure on the other side of the filtration media, substantially all of the gas, liquid, and entrained particles on the high pressure side of the filtration media that move to the low pressure side as a result of the pressure differential will flow through the filtration media (loose filtration material  40 , in this case). 
   The term “disposed across” an element means that the filtration media (for example, loose filtration material  40 ) forms an interconnection across the element such that substantially all gas, vapor, liquid or particles passing through the element to and from the internal volume of the vessel and the surrounding atmosphere pass through the filtration media. The “element” referred to here may be an orifice passageway, a port, a hole, an opening, or a similar element. In some embodiments this interconnection of the filtration media across an element may be enhanced by bonding, welding, brazing, threading, pressure-fitting, or similar techniques. 
   The term “disposed between” two or more elements means that the filtration media (loose filtration material  40 , for example) forms an interconnection between two elements (the lateral flange  31  of the cover  30  and the lip  13 , in this case) such that substantially all gas, vapor, liquid or particles passing between these elements to and from the internal volume  101  of vessel  100  and the surrounding atmosphere pass through the filtration media. 
   In a second embodiment of this invention, as illustrated in  FIG. 2 , a container  102  is comprised of a vessel  110  and a cover  130 . Container  102  has a base  111  and a longitudinal wall  112 . A charge  20  is placed in the vessel  110 . In a preferred embodiment the vessel  110  is comprised of material that is a susceptor to microwaves. Preferably, a circumferential groove  116  (detailed in  FIG. 2A ) is machined into the lip  113  of the vessel  10 . In an alternate embodiment comprising a metal vessel the circumferential groove  116  could be formed by flaring (mechanically bending) the lip  113  laterally inward or outward, and forming a circumferential groove in the flared section. Note that  FIG. 1 , lip  13  is horizontal whereas in  FIG. 2A , lip  113  is substantially vertical. A distinguishing feature of a “lip” in a vessel is its proximity to an opening, not its orientation. For example, horizontal lip  13  in  FIGS. 1 and 1A  is proximal to opening  14  (labeled in  FIG. 1A ). Substantially vertical lip  113  in  FIGS. 2 ,  2 A, and  2 B is proximal to opening  114  (labeled in  FIG. 2B ). Further, in the embodiment detailed in  FIG. 2A , the lateral flange  131  of the cover  130  has a circumferential rim  132  with a “v” cross-section which projects downward from the lateral flange  131  so that the rim  132  is configured to conform to and fit in part into circumferential groove  116 . The space between the circumferential groove  116  and the rim  132  in  FIG. 2A  defines an orifice passageway  91 . The container  102  is characterized by having an element or a combination of elements (elements  110  and  130  in this case) which, except for one or more orifice passageways ( 91 , in this case), provide a substantially leak-tight environment for the charge  20 . 
   In this embodiment the loose filtration material  40 , preferably substantially comprised of a chemically stable filter medium, is placed within the circumferential groove  116  such that it is disposed across the orifice passageway  91 , that is, disposed between the circumferential groove  116  and the rim  132 . In a preferred embodiment the cover would also be comprised of material that is a susceptor of microwaves, and the weight of the cover would be sufficient to substantially maintain the position of the rim  132  relative to the groove  116  during the chemical reaction that takes place when the apparatus is placed in an oven and heated.  FIG. 2C  illustrates an alternate embodiment of a cover  130 A having edge portion  131 A with a circumferential groove  116 A, circumferential rim  132 A, and orifice passageway  91 A. Loose filtration material  40  is disposed between groove  116 A and rim  132 A. 
   In an alternate embodiment depicted in  FIG. 3 , a container  104  is comprised of a first vessel  50 , a second inverted vessel  80 , and a tray  70 . In this embodiment, the first vessel  50  having a base  51 , longitudinal wall  52  with lip  53  is placed in loose filtration material  40  which had been placed on a generally horizontal surface  71  of the tray  70 , such that the loose filtration material  40  substantially circumferentially surrounds the first vessel  50 . Lip  53  defines an opening in first vessel  50 . A charge  20  such as titanium dioxide and lithium powders is placed in the first vessel  50 . The second inverted vessel  80  is comprised of a base  81  and a longitudinal wall  82  with a lip  83 , and the second inverted vessel is placed over the first vessel  50  such that substantially all of the circumferential segments of the edge of the lip  83  of the second vessel  80  are resting in or on the loose filtration material  40 . The space between the lip  53  of the first vessel  50 , the lip  83  of the second vessel  80 , and the horizontal surface  71  in  FIG. 3  establishes an orifice passageway  92 . The container  104  is characterized by having an element or a combination of elements (elements  50 ,  80  and  70  in this case) which, except for one or more orifice passageways ( 92  in this case), provide a substantially leak-tight environment for the charge  20 . 
   In any embodiment employing a tray  70 , it is preferred, as illustrated in  FIG. 3 , to provide vertical risers  72  attached to the horizontal surface  71  of the tray  70  to partially confine the lateral dispersion of the loose filtration material  40 . Preferably tray  70  is a third vessel that is larger in diameter than the other two vessels. In a preferred embodiment the second vessel  80  and the tray  70  are comprised of materials such as alumina that are transparent to microwaves. It is seen that in this configuration substantially all gases, vapors, liquids, or particles passing through the orifice passageway  92  between the surrounding atmosphere and the first vessel  50  will pass through the loose filtration material  40 . 
     FIG. 4  illustrates another embodiment in which a container  105  is comprised of a vessel  210  and a cover  230 . For reference, a charge  20  representing chemicals to be processed in the apparatus is illustrated. The vessel  210  which comprises a base  211 , a longitudinal wall  212  and a lip  213  is provided. A cover  230  which comprises a lateral flange  231  is also provided. The space between the lip  213  of the vessel  210  and the lateral flange  231  of the cover  230  in  FIG. 4  establishes an orifice passageway  93 . Structured filtration material  245  is disposed between the lip  213  and the lateral flange  231 , that is, disposed across the orifice passageway  93 . In preferred embodiments, structured filtration material  245  is a ceramic filter having open pores. Structured filtration material is another example of filtration media. In some embodiments, semi-rigid materials such as fiberglass or metal mesh materials may be used. Such semi-rigid materials are other examples of filtration media. 
   Container  105  is characterized by having an element or a combination of elements (elements  210 , and  230  in this case) which, except for one or more orifice passageways ( 93  in this case) provide a substantially leak-tight environment for the charge  20 . 
   In some embodiments of the type illustrated in  FIG. 4 , the weight of the cover  230  is sufficient to seal the interfaces between an edge portion  231  of the cover  230  and the structured filtration material  245 , and between the lip  213  and the structured filtration material  245  such that substantially all gases, vapors, liquids, or particles passing between the vessel  210  and the surrounding atmosphere pass through the structured filtration material  245 . To further ensure such a seal, as illustrated in  FIG. 4A , in some embodiments bonding material  61  may be applied between the lip  213  and the structured filtration material  245 , and bonding material  62  may be applied between the lateral flange  231  and the structured filtration material  245 . Bonding material  61  and bonding material  62  may comprise the same physical material or different physical material. Such bonding material may comprise adhesives, tapes, mechanical fasteners, or soldered, brazed or welded materials. In embodiments using the bonding material  61  and the bonding material  62 , the charge  20  should be placed in the vessel  210  before the bonding materials are applied. When the chemical process for which this apparatus is designed is completed, it is generally convenient to de-bond at least one of the bonding materials  61  or  62  to remove the chemical reaction products. Consequently, in preferred embodiments the bonding material(s)  61  and/or  62  that are to be de-bonded are selected from materials that are easily fractured or dissolved. Examples would be chemically soluble or low-strength adhesives. 
     FIG. 5  illustrates a further embodiment where a container  106  is comprised of a vessel  310  and a cover  330 . The space between the lip  313  of the vessel  310  and the lateral flange  331  of the cover  330  establishes an orifice passageway  94 . In this example, the structured filtration material  345  is placed laterally between the edge of the lip  313  which defines the opening in the vessel  310  and the lateral flange  331  of the cover  330 , across the orifice passageway  94 . 
   Some embodiments utilize semi-rigid filtration material  347 , such as depicted in  FIG. 5B . In these embodiments it is helpful for facilitating the assembly of the apparatus to have the edge of the lip  314  beveled so that it has a somewhat upward-oriented face, and to have the edge portion  334  of the cover  332  beveled so that it has a somewhat downward-oriented face that approximately matches the incline of the face of the edge of the lip  314 . Semi-rigid filtration material  347  is shown disposed between lip  314  and edge portion  334 . 
   Container  106  of  FIG. 5  is characterized by having an element or combination of elements (elements  310 , and  330  in this case) which, except for any orifice passageways ( 94  in this case) provide a substantially leak-tight environment for the charge  20 . 
   As with the embodiment previously depicted in  FIG. 4 , and also shown in detail in  FIG. 5A  for the embodiment of  FIG. 5 , bonding materials  61  and  62  may be applied to ensure proper sealing of the vessel  310 , structured filtration material  345 , and cover  330 . Alternately in some embodiments, these seals may be enhanced by the use of conforming threads. See for example  FIG. 5C  where conforming threads are used between the outer edge of threaded filtration material  349  and the edge of the lip  315 , and the lateral flange  337  of the cover 336  and the inner edge of the threaded structured filtration material  349  such that the structured filtration material  349  and or the cover  336  and or the lip  315  are screwed together. 
     FIG. 6  depicts another embodiment where a container  107  is comprised of a vessel  410  and a cover  430 . Vessel  410  has a base  411 , a longitudinal wall  412  and a lip  413 . In this embodiment, the cover  430  has a hole defined by a cutout edge  435 , and the hole establishes an orifice passageway  95 . The structured filtration material  445  is disposed across the hole in the cover  430  defined by the cutout edge  435 , that is, it is disposed across the orifice passageway  95 . 
   The container  107  is characterized by having an element or a combination of elements (elements  410 , and  430  in this case) which, except for any orifice passageways ( 95  in this case) provide a substantially leak-tight environment for the charge  20 . 
   In the embodiment of  FIG. 6 , the structured filtration material  445  is substantially structurally rigid. Structured filtration material  245  in  FIG. 4  and structured filtration material  345  in  FIG. 5  are also substantially structurally rigid. Such rigidity may be achieved by solidification of the filtration media itself, such as by sintering it or incorporating it in a matrix material, or such rigidity may be achieved by employing a configuration in which the structured filtration material  245 ,  345 ,  445  is comprised of a device such as a disk-shaped canister or tray to confine loose filtration material. In some embodiments such as depicted in  FIG. 6  the structured filtration material  445  may be comprised of non-rigid fibrous material (such as metal filament packing) that is wedged into the hole defined by the cutout edge  435  of the cover  430 . In such embodiments using non-rigid fibrous materials it is helpful if the quantity of structured filtration material  445  and the size of the hole defined by the cutout edge  435  are matched appropriately so that the structured filtration material  445  stays attached (wedged) in the hole defined by the cutout edge  435 . In some embodiments the assembly of the apparatus may be enhanced by providing conforming threaded surfaces (not shown) on the edge of the lip  413  and the outside edge of the cover  430  such that the cover  430  is screwed onto the vessel  410 . In some embodiments, as illustrated in  FIG. 6A , bonding material  61  may be applied between the lip  413  and the cover  430 , and/or bonding material  62  may be applied between the cutout edge  435  of the cover  430  and the structured filtration material  445 . In some embodiments cover  430  may comprise surface enhancement elements (not shown) such as a bezel, a collar, a glaze, bonding material, adhesives, or other structures used to improve the sealing function of the interface between the cutout edge  435  and the apparatus elements (e.g., vessel  410  and structured filtration material  445 ) attached to it. 
   In an embodiment illustrated in  FIG. 7 , a container  108  is comprised of a vessel  510  having a base  511  and longitudinal wall  512 . The vessel  510  has a lip  513  which establishes an orifice passageway  96 . Structured filtration material  545  is disposed across the orifice passageway  96 . To enhance the attachment of the structured filtration material  545  to the lip  513 , in some embodiments the lip  513  may comprise surface enhancement elements (not shown) such as a bezel, a collar, a glaze, bonding material, adhesives, or other structures used to improve the sealing function of the interface between the lip  513  and the structured filtration material  545 . In some embodiments, as illustrated in  FIG. 7A , the attachment may be enhanced by bonding material  61  applied between the lip  513  and the structured filtration material  545 . The container  108  is characterized an element (element  510  in this case) or a combination of elements which, except for any orifice passageways ( 96  in this case) provide a substantially leak-tight environment for the charge  20 . 
     FIG. 8  illustrates another embodiment in which a container  109  is comprised of a vessel  610  and a cover  630 . Vessel  610  has a base  611 , a longitudinal wall  612  and a lip  613 . In this embodiment the cover  630  is connected to the vessel  610  using bonding material  63  in a manner which forms a gap-less seal. The term “gap-less seal” means that within the range of expected operating pressures for the apparatus, if the ambient gas, vapor, or liquid pressure on one side of the interface between the combination of elements (the cover  630  and the vessel  610 , in this case) is higher than the pressure on the other side of the interface between the combination of elements, substantially none of the undesired gas, liquid, or entrained particles on the high pressure side of the filter will flow through the interface between the combination of the elements. In some variations this seal is accomplished by a mechanical connection, such as a pressure fit or a threaded connection. In other variations, such as illustrated in  FIG. 8 , bonding material  63  is applied between the lateral flange  631  of the cover  630  and the lip  613  of the vessel  610 . In other variations the bonding material  63  may be applied between the edge of the lip  613  and a plug  632  on the cover  630 . 
   In the embodiment of  FIG. 8  as detailed in  FIG. 8A , the vessel  610  is further comprised of a port  695  defined by a cutout edge  635  in an element (i.e. longitudinal wall  612 ) of the vessel  610 . This port  695  defined by the cutout edge  635  is functionally equivalent to the orifice passageway described in other embodiments. In  FIG. 8A  the port defined by a cutout edge  635  is in the longitudinal wall  612  of the vessel  610 , but in other embodiments the port defined by the cutout edge  635  could be in the base  611  or the lip  613 . 
   The apparatus of  FIG. 8  is further comprised of structured filtration material  645  that is disposed across the port  695  defined by the cutout edge  635  in an element of the vessel  610 . As detailed in  FIG. 8A , bonding material  61  may be applied between the cutout edge  635  and the structured filtration material  645  to further ensure that substantially all gases, vapors, liquids, or particles passing between the vessel  610  and the surrounding atmosphere pass through the structured filtration material  645 . The container  109  is characterized as an element or a combination of elements ( 610 , and  630  in this case) which, except for any orifice passageways ( 695  in this case) provide a substantially leak-tight environment for the charge  20 . 
   In preferred embodiments of this invention, the vessel (e.g.,  10 ,  50 ,  110 ,  210 ,  310 ,  410 ,  510 ,  610 ) is comprised of a material such as MgO, ZrO 2  or a nitride or a carbide that is a susceptor to microwaves. Optionally, the cover (e.g.,  30 ,  130 ,  230 ,  330 ,  430 ,  530 ,  630 ) may also be comprised of a material that is a susceptor to microwaves. In some applications a carbonaceous vessel or cover is not preferred because of the potential for a back reaction with the materials being processed. Using microwave suscepting vessels and covers permits the apparatus to be heated in a microwave oven to induce or enhance desired chemical process reactions. In embodiments where microwaves are not used to heat the apparatus, the vessel (e.g.,  10 ,  50 ,  110 ,  210 ,  310 ,  410 ,  510 ,  610 ) and cover (e.g.,  30 ,  130 ,  230 ,  330 ,  430 ,  530 ,  630 ) may be comprised of various refractory materials that are commonly used to make crucibles. In these embodiments the apparatus would typically be heated in a conventional thermal furnace (such as resistive heating), or by infrared radiation, or by induction heating. 
   In some embodiments of the invention, the filtration media may be comprised of loose filtration material such as silica power, carbon powder, cellulose fibers, or metal filaments. Typically these materials are physically confined or contained by other elements of the apparatus to maintain their physical integrity. In other embodiments filtration media may be comprised of semi-rigid filtration material such as woven or non-woven organic or inorganic fibers. In some embodiments the filtration media may be structured filtration material, such as sintered porous metals or oxides, or porous composite materials comprising ceramics, metals, or composites. When semi-rigid filtration media and structured filtration material are used, the filtration media is often substantially structurally rigid by itself, obviating the need for a separate device to confine the material. 
   In preferred embodiments the filtration media is comprised of a chemically stable filter medium. A highly desirable characteristic of a chemically stable filter medium is that it does not melt at the temperatures experienced under the chemical process conducted in the apparatus in which the chemically stable filter medium is used. Another desirable feature of a chemically stable filter medium is that it does not chemically react with the off-gas emissions of the chemical process, although it is generally desirable that emissions (off-gases and particles) will become physically immobilized in the chemically stable filter medium, such as by plating out on the chemically stable filter medium, or by becoming entrapped in the chemically stable filter medium. In a chemical process involving the reduction of titanium dioxide with lithium, for example, calcium oxide would satisfy these preferences but silica would not be a desirable chemically stable filter medium because it would at least partially react with the excess lithium. Another desirable feature of the chemically stable filter medium is that its physical micro-structure should be such that it provides a tortuous path for off-gas emissions or atmospheric intrusions that would occur in a chemical process operated within the apparatus. This can often be achieved by the selection of an appropriate particle size for the medium. Typically, materials with average particle sizes less than 45 microns work well. Larger particle sizes can be used in larger apparatuses where the flow path is longer. A further desirable property of a chemically stable filter medium is that the medium should be a good thermal insulator. Yet a further desirable property of the chemically stable filter medium in embodiments where the apparatus is heated in a microwave furnace, is that the chemically stable filter medium has a more favorable dielectric loss tangent (i.e., it is less a susceptor of microwaves) than the charge, or the apparatus, or the reaction products. This quality is desired in order to favor absorption of the microwaves by these other items. 
     FIG. 9  illustrates a method  700  according to the invention. The method begins with step  702  in which a charge is placed in a container that is a susceptor of microwaves. The container is substantially gas-tight except for at least one orifice passageway. The orifice passageway is substantially filled with filtration media. Process  700  continues with step  704  which comprises surrounding the container with a thermal insulating casket that is transparent to microwaves. Method  700  concludes with exposing the charge, the container, and the casket to microwaves for a duration of time at least until a desired chemical reaction occurs in the charge. 
     FIG. 10  illustrates an alternate method  710  of the invention. The first step  712  of the method involves assembling a container comprising a susceptor vessel having a lip that defines an opening. The container further comprises a cover, where the cover has a lateral flange, with the lateral dimensions of the cover overlapping the opening of the susceptor vessel. The container also comprises filtration media between the lip and the lateral flange. In step  714  a charge is assembled. In step  716  the charge is placed in the container. In step  718  the container and the charge are exposed to microwaves. 
     FIG. 11  illustrates an alternate method  730  of the invention. The first step  732  of the method involves assembling a container comprising a susceptor vessel having a lip that defines an opening. The container further comprises a cover, where the cover has a lateral flange, with the lateral dimensions of the cover being larger than the opening of the susceptor vessel, and where the cover has a plug and the plug is smaller than the opening and fits into the opening. The container also comprises filtration media between the lip and the lateral flange. In step  734  a charge is assembled. In step  736  the charge is placed in the container. In step  718  the container and the charge are exposed to microwaves. 
     FIG. 12  illustrates an alternate method  750  according to the invention. The first step  752  of the method involves assembling a container comprising a susceptor vessel having a lip that defines an opening. The container further comprises a cover, where the cover has a lateral flange, with the lateral dimensions of the cover being larger than the opening of the susceptor vessel, and the cover has a hole. The container also comprises filtration media installed in the hole. In step  754  a charge is assembled. In step  756  the charge is placed in the container. In step  758  the container and the charge are exposed to microwaves. 
     FIG. 13  illustrates an alternate method  770  according to the invention. The first step  772  of the method involves assembling a container comprising a susceptor vessel having a lip that defines an opening. The container further comprises filtration media installed in the opening of the susceptor vessel. In step  774  a charge is assembled. In step  776  the charge is placed in the container. In step  778  the container and the charge are exposed to microwaves. 
     FIG. 14  illustrates an alternate method  790  according to the invention. The first step  792  of the method involves assembling a container comprising a susceptor vessel having a lip with an opening, and a hole established by a cutout edge in a wall. The container further comprises a cover that has a lateral flange having lateral dimensions sufficient to overlap the opening. The container also comprises filtration media installed in the opening of the susceptor vessel. In step  794  a charge is assembled. In step  796  the charge is placed in the container. In step  798  the container and the charge are exposed to microwaves. 
   EXAMPLE 
   In a test using the embodiment of this invention illustrated in  FIG. 3 , the first vessel  50  was placed in loose filtration material  40  which had been placed on a generally horizontal surface  71  of the tray  70 , such that the loose filtration material substantially circumferentially surrounded the first vessel  50 . The loose filtration material was comprised substantially of calcium oxide. The first vessel  50  was a crucible comprising material (MgO) that is a susceptor to microwaves. A charge  20  comprising titanium dioxide and lithium powders was placed in the first vessel  50 . The second inverted vessel  80  constructed primarily of magnesium oxide, and comprised of a base  81  and a longitudinal wall  82  with a rim  83 , was placed over the first vessel  50  such that substantially all of the circumferential segments of the edge of the rim  83  of the second vessel  80  were resting in or on the loose filtration material  40 . The space between the lip  53  of the first vessel  50 , the rim  83  of the second vessel  80 , and the horizontal surface  71  in  FIG. 3  establishes an orifice passageway  92 . The container  104  is characterized by having an element or a combination of elements (elements  50 ,  80  and  70  in this case) which, except for one or more orifice passageways ( 92  in this case), provide a substantially leak-tight environment for the charge  20 . In the test being described, the vessels and tray were placed in a microwave oven and surrounded by a casket of thermally insulating alumina. The entire apparatus was then heated until an exothermic reaction occurred between the elements of the charge  20 . Metal vapor and other reaction products were produced as a result of the reaction, but no visible amount of such reaction products escaped from the vessels into the surrounding atmosphere. 
   The foregoing description of certain embodiments of this invention has been provided for the purpose of illustration only, and various modifications may be made without affecting the scope of the invention as set forth in the claims that follow. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed. Although some embodiments are shown to include certain features, the inventors specifically contemplate that any feature disclosed herein may be used together or in combination with any other feature on any embodiment of the invention. It is also contemplated that any feature may be specifically excluded from any embodiment of an invention.

Technology Classification (CPC): 1