Patent Publication Number: US-2009236233-A1

Title: Aluminum electrolysis cell electrolyte containment systems and apparatus and methods relating to the same

Description:
BACKGROUND 
     Aluminum is generally produced via the Hall process, which entails passing current through an electrolytic bath comprising alumina and cryolite to reduce the alumina to aluminum metal. An electrolysis cell generally holds the electrolytic bath and includes a plurality of anodes that pass current through the bath to a cathode. Conventional anodes are made of carbon and are thus consumed during the electrolysis process. Efforts have been made to utilize non-consumable anodes for use in electrolysis cells. Such anodes are typically metal or metal-oxide based and are referred to as “inert anodes” since they are both dimensionally stable, compared to carbon anodes, and electrically conductive at normal electrolysis temperatures. 
     SUMMARY OF THE DISCLOSURE 
     Broadly, the instant disclosure relates to systems and methods for containing the electrolytic bath within an aluminum electrolysis cell. During conventional aluminum production processes, a crust generally develops over the electrolytic bath. Crust that develops on the sidewall is called a ledge. The ledge may protect the sidewall and may prevent the electrolytic bath from leaking out of the cell via cracks between sidewall members. Maintenance of the ledge results in significant heat loss, and attempts to insulate the system to conserve this heat loss generally result in loss of the ledge (e.g., via melting). Thus, it is desirable to eliminate reliance on the ledge for bath containment purposes, especially with the use of inert anodes, which may facilitate operation of electrolysis cells at lower temperatures. 
     In one approach, an aluminum electrolysis cell is provided. The aluminum electrolysis cell may include an outer shell, a bottom (e.g., a cathode), and a plurality of bath resistant blocks defining a surrounding wall. The bottom and the plurality of bath resistant blocks may define a chamber adapted for holding a molten salt electrolyte. The cell may further include at least one spring member coupled to at least one of the plurality of bath resistant blocks and the outer shell. In one embodiment, a spring member is maintained at least some of the bath resistant blocks in a substantially leak-tight configuration. For example, a spring-member may be used to accommodate the differential expansion that may be realized between one or more bath resistant blocks and the steel shell as a result of differential coefficients of thermal expansion. In one embodiment, a spring member is adapted to expand and/or contract during operation of the aluminum electrolysis cell. In one embodiment, the plurality of bath resistant blocks includes a corner block, and at least one spring member is coupled to the corner block (e.g., via the outer shell). 
     In one embodiment, the plurality of bath resistant blocks includes both corner blocks and side blocks, where at least one corner block is located between adjacent side blocks. In one embodiment, a first set of side blocks defines a first inner sidewall. In a related embodiment, a second set of side blocks defines a second inner sidewall. In one embodiment, the first sidewall is parallel the second sidewall. In one embodiment, the first sidewall is transverse (e.g., orthogonal) the second sidewall. In one embodiment, a corner block joins the first sidewall to the second sidewall. 
     In one embodiment, at least some of the plurality of bath resistant blocks define an inner row and an outer row. In one embodiment, a spring member assists in maintaining the inner row in a substantially leak-tight configuration. In one embodiment, a spring member assists in maintaining the outer row in a substantially leak-tight configuration. In one embodiment, at least some of the plurality of bath resistant blocks define an upper row and a lower row. In one embodiment, a spring member assists in maintaining the upper row in a substantially leak-tight configuration. In one embodiment, a spring member assists in maintaining the lower row in a substantially leak-tight configuration. 
     In one embodiment, at least two spring members are coupled to a corner block and the outer shell. In one embodiment, the spring members are restrictively coupled to the outer shell (e.g., via mechanical restraints, such as bolts). In one embodiment, the spring members are coupled to the corner block via simple physical contact (e.g., not via mechanical restraints). The physical contact may be facilitated, for example, via a head of the spring member, which is interconnected to a spring. Thus, the spring members may remain coupled to the corner block over various operating temperatures, and may expand and/or contract, as necessary to maintain physical contact with the corner block. In one embodiment, a corner block may include a first surface and a second surface. In one embodiment, a first spring member is coupled to the first surface of the corner block, and a second spring member is coupled to the second surface of the corner block. Thus, application of a responsive force in at least two directions may be facilitated. In one embodiment, an axis of the first surface of the corner block is transverse (e.g., non-parallel to, such as orthogonal to) an axis of the second surface of the corner block. 
     Methods of operating aluminum electrolysis cells are also provided. In one embodiment, a method includes the steps of passing electricity through a molten salt electrolyte comprising alumina via an anode and cathode of an electrolysis cell, maintaining a plurality of bath resistant blocks in a substantially leak-tight configuration, thereby at least assisting in containing the molten salt electrolyte within the electrolysis cell, and producing alumina in the electrolysis cell in the absence of a ledge. In one embodiment, the maintaining step includes the step of applying a force to at least one of the plurality of blocks via a spring member. In one embodiment, during the maintaining step, the spring member is responsive to fluctuating operating conditions of the electrolysis cell. 
     These and other aspects, advantages, and novel features of the invention are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, cross-sectional view illustrating one embodiment of a conventional aluminum electrolysis cell. 
         FIG. 2   a  is a top, schematic view illustrating one embodiment of an aluminum electrolysis in accordance with the instant disclosure. 
         FIG. 2   b  is a side, cross-sectional view of the aluminum electrolysis of  FIG. 2   a.    
         FIG. 3   a  is a top, view illustrating one embodiment of a corner of an aluminum electrolysis cell. 
         FIG. 3   b  is a side, cross-sectional view of the corner of  FIG. 3   a.    
         FIG. 4  is a side, cross-sectional view of one embodiment of a spring member. 
         FIG. 5  is a side, design view illustrating one embodiment of a sidewall arrangement of an aluminum electrolysis. 
         FIG. 6  is a top, design view illustrating another embodiment of a sidewall arrangement of an aluminum electrolysis. 
         FIG. 7  is a top, design view illustrating another embodiment of a sidewall arrangement of an aluminum electrolysis. 
         FIG. 8  is a top, design view illustrating another embodiment of a sidewall arrangement of an aluminum electrolysis. 
         FIG. 9  is a top, design view illustrating another embodiment of a sidewall arrangement of an aluminum electrolysis. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is now made to the accompanying drawings, which at least assist in illustrating various pertinent features of the instant disclosure. 
     As noted above, the instant disclosure relates to systems and methods for containing an electrolytic bath in an aluminum electrolysis cell in the absence of a ledge. Conventional aluminum electrolysis cells generally include anodes, a cathode and a plurality of blocks. The arrangement of the plurality of blocks defines a sidewall. During conventional aluminum production processes, a crust generally develops over the electrolytic bath. Crust that develops on the sidewall is often referred to as a ledge. The ledge may protect the sidewall and may prevent the electrolytic bath from leaking out of the cell via cracks between the blocks. 
     One embodiment of a conventional aluminum electrolysis cell is illustrated in  FIG. 1 . In the illustrated embodiment, the cell  1  includes an outer shell  18  containing a conventional sidewall  12 . The cell  1  further includes a cathode  11 . Anodes (not illustrated) pass current to the cathode  11  through the molten salt electrolyte  15  to produce aluminum metal  17 , and a current collector  19  carries current from the cathode  11 . The sidewalls  12  are covered by a ledge  14 , which prevents the molten salt electrolyte  15  and the aluminum metal  17  from leaking out of the cell  2  via gaps between blocks of the sidewall  12  and/or leaking out of the cell  2  via gaps between the cathode  11  and the blocks of the sidewall  12 . 
     It may be useful to operate an aluminum electrolysis cell in the absence of a ledge. In such an embodiment, it is important that the sidewall have a leak-tight configuration. In this regard, improved aluminum electrolysis cells are disclosed herein. One embodiment of an aluminum electrolysis in accordance with the instant disclosure is illustrated in  FIG. 2   a - 2   b . In the illustrated embodiment, the electrolysis cell  2  includes anode assemblies  80 , a cathode  11 , a current collector  19  (not illustrated in  FIG. 2   a  for purposes of illustration) and an outer shell  60 . The cell  2  further includes a plurality of bath resistant blocks  30 ,  40  that define a surrounding wall. The plurality of bath resistant blocks generally include corner blocks  30  and inner blocks  40 . A row of inner sidewall blocks generally defines an inner sidewall portion (e.g., sidewall  43 ). Each of the rows, in conjunction with the corner blocks  30 , makes up a surrounding perimeter, referred to herein as the inner sidewall. The plurality of blocks may optionally include outer blocks  50 . The inner sidewalls, in combination with the cathode  11  defines a cavity adapted to hold a molten salt electrolyte  15  and aluminum metal  17 . Spring members  20  are used to maintain at least some of the inner blocks  40  and the corner blocks  30  in a substantially leak-tight configuration. More particularly, the spring members  20  provide a force, such as a spring force, a compressive force, or an elastic force, to name few, that forces at least some of the inner blocks  40  and the corner blocks  30  together and into the substantially leak-tight configuration. In one embodiment, the force provided by the spring members  20  is responsive to the dynamic operating conditions of the electrolysis cell  2  (e.g., temperature fluctuations), and the spring members  20  are able to provide more force or less force, as necessary, based on cell operating conditions. In one embodiment, the force provided by the spring members  20  is sufficient to prevent/restrict any appreciable amount of molten salt electrolyte  15  from exiting the cell via gaps between members of the inner blocks  40  and/or via gaps between the inner blocks  40  and the corner blocks  30 . Thus, the cell  2  may be operated in the absence of a ledge. 
     As used herein, “ledge” means a solid phase form of the salt electrolyte that is generally located between the molten salt electrolyte (also sometimes referred to as “bath”) and one or more portions of the inner sidewall of an aluminum electrolysis cell. In this regard, the ledge is sometimes referred to as “frozen electrolyte”. As used herein, “molten salt electrolyte” means an electrolyte comprising alumina (Al 2 O 3 ) and cryolite (Na 3 AlF 6 ), and which is in a liquid/molten phase. The aluminum may be in dissolved form. The molten salt electrolyte may include other additives. As used herein, “spring member” means any apparatus capable of applying a force to at least one of the plurality of blocks to at least assist in maintaining at least some of the blocks in a substantially leak-tight configuration. 
     In one embodiment, the cell  2  is operated in the absence of a ledge and produces aluminum at commercial viable rates (e.g., from about 100,000 to 300,000 amperes and at a current efficiency of at least about 90%]. In one embodiment, the cell  2  produces commercial purity aluminum. As used herein, “commercial purity aluminum” means aluminum produced by an electrolytic process that meets generally accepted commercial purity standards. In one embodiment, the commercial purity aluminum includes not greater than of 0.2 wt. % Fe, such as not greater than 0.15 wt. % Fe, or even not greater than 0.13 wt. % Fe. In one embodiment, the commercial purity aluminum includes not greater than 0.1 wt. % Cu, such as not greater than 0.034 wt. % Cu, or even not greater than 0.03 wt. % Cu. In one embodiment, the commercial purity aluminum includes not greater than 0.034 wt. % Ni, such as not greater than 0.03 wt. % Ni. In one embodiment, the commercial purity aluminum includes not greater than 0.2 wt. % Si, such as not greater than 0.15 wt. % Si, or even not greater than 0.10 wt. % Si. In one embodiment, the commercial purity aluminum includes a not greater than 0.03 wt. % Zn and/or and not greater than 0.03 wt. % Co. In one embodiment, the cell  2  is operated in the absence of a ledge and at reduced temperatures relative to conventional electrolysis cells. In one embodiment, the temperature of the molten salt electrolyte is not greater than 900° C., such as from about 700° C. to 900° C. 
     In the illustrated embodiment, the inner blocks  40  are in the form of rows, but may be configured in any suitable orientation (e.g., elliptical/circular). The outer blocks  50  may be used to support the inner blocks  40  and are generally configured coincidental to the configuration of the inner blocks  40 . In the illustrated embodiment, the cell  2  includes first and second layers of blocks  40 ,  50 , respectively. In other embodiments, an electrolysis cell  2  may include only a single layer of blocks. In other embodiments, an electrolysis cell  2  may include more than two layers of blocks. In one embodiment, each corner block  30  is located between adjacent rows of inner blocks  40 . That is, a first row of inner blocks  40  may be adjoined to another row of inner blocks  40  via a corner block  30 . 
     The bath resistant blocks  30 ,  40 ,  50  generally comprise materials that are suited for use in the electrolysis cell  2 . In one approach, at least some of the blocks  30 ,  40 , and/or  50  comprise a material that is resistant to degradation when exposed to the bath of the electrolysis cell  2  (the bath generally comprising alumina, cryolite, and metal aluminum). In one embodiment, at least some of the bath resistant blocks comprise a refractory material. In one embodiment, at least some of the blocks comprise metal oxides and/or metal nitrides. In one embodiment, at least some of the bath resistant blocks comprise graphite. 
     The cell  2  generally includes at least one anode assembly, but may include many anode assemblies, such as the plurality of anode assemblies  80  illustrated in  FIGS. 2   a - 2   b . The anode assemblies generally comprise inert anodes  81 , but in other embodiments may include carbon anodes. As used herein, “inert anode” means an electrode that: (i) is dimensionally stable (as compared to conventional carbon anodes) in a molten salt electrolyte, and (ii) conducts electrical current at molten salt electrolyte temperatures of from about 600° C. to about 1000° C. and at electrical conduction rates sufficient to achieve commercially viable aluminum production rates (e.g., an electrical conductivity of at least about 120 ohm −1  cm −1 ). Inert anode materials are well known and may comprise, for example, conductive metals and/or metal oxides. In operation, current passes through the molten salt electrolyte  15 , via cathode  11  and anodes  81 , to reduce the alumina to aluminum metal  17 . Aluminum metal  17  may be periodically tapped from the cell  2 . In one embodiment, the tapped aluminum metal is commercial purity aluminum. 
     The inert anodes  81  are fastened to conductors  82  (e.g., metal conductors rods) which may pass through a protective cover  83  (e.g., a ceramic cover) and/or insulation  84 . The conductors  82  may be attached to a distribution plate  85 . The distribution plate  85  may be supported by a support beam  86 , which can be used to raise or lower the anode assemblies  80 . The distribution plate  85  may provide a current path between the support beam  86  and the conductors  82 . The protective cover  83  and insulation  84  may provide environmental and thermal protection. For example, the protective cover  83  may be made from a highly corrosion resistant ceramic material capable of being exposed to the corrosive environment of the molten salt electrolyte  15 . 
     The electrolysis cell  2  may include any number of spring members  20  necessary to maintain the plurality of blocks in a substantially leak-tight configuration. In the illustrated embodiment, the electrolysis cell  2  includes two spring members  20  per corner, with a first spring members applying a force in a first vector, and a second spring member applying a force in a second vector, which is different than the first vector. In the illustrated embodiment, the first vector is coincidental to a first sidewall (e.g., a first row of blocks) and the second vector is coincidental to a second sidewall (e.g., a second row of blocks). In one embodiment, the first and second force vectors are transverse, such as orthogonal. In one embodiment, the first and second force vectors are parallel (e.g., via two spring members located coincidental to one another, such as on the same side of a corner block). In one embodiment, at least one spring member per corner of the electrolysis cell is utilized. Other configurations may be employed. Thus, the spring members may be located at a plurality of locations within/relative to electrolysis cell  2 , and surfaces of the spring members  20  may compressively engage surfaces of one or more blocks to facilitate compression of at least some of the blocks into a substantially leak-tight configuration. 
     One particular spring member arrangement is illustrated in  FIGS. 3   a - 3   b . In the illustrated embodiment, the cell  2  includes a plurality of spring members  20 , such as a set of first spring members  20   a  and a set of second spring members  20   b . Each of the spring members are coupled to a corner block  30  via a corner portion  62  of an outer shell  60 . In particular, the first spring members  20   a  compressively engage a first surface  31  of the corner block  30 , thereby compressing a first inner block  40  and a first outer block  50  relative to the corner block  30 . Likewise, the second spring members  20   b  compressively engage a second surface  33  of the corner block  30 , thereby compressing a second inner block  42  and a second outer block  52  relative to the corner block  30 . 
     The corner block  30  may be designed to engage spring member(s)  20  and at least two inner blocks  40 ,  42  of an electrolysis cell  2 . Thus, the corner block  30  may include surfaces that facilitate mating engagement with spring member(s)  20  and inner blocks  40 ,  42 . The corner block  30  may also engage additional blocks, such as outer blocks  50 ,  52 , and/or additional spring members. In the illustrated embodiment, the corner block  30  is offset from inner blocks  40 ,  42  and outer blocks  50 ,  52  and includes planar surfaces for mating with corresponding planar surfaces of the inner and outer blocks. The corner block  30  also includes a first surface  31  configured for engagement with the first spring members  20   a  and a second surface  33  configured for engagement with the second spring members  20   b . In the illustrated embodiment, the first spring members  20   a  are offset from the second spring members  20   b , and the first and second surfaces  31 ,  33  may be correspondingly offset from one another so as to facilitate engagement with the spring members  20   a ,  20   b . In the illustrated embodiment, the first surface  31  is offset from the second surface  33  via a joining surface  35 . In one embodiment, the first surface  31  has an axis that is transverse to an axis of the second surface  33 . In the illustrated embodiment, the intersection of the axis of the first surface  31  with the axis of the second surface  33  is orthogonal. However, the intersection of the axis may define any non-parallel configuration so long as they provide surfaces that facilitate engagement with spring members. In one embodiment, the first and/or second surfaces  31 ,  33  are oriented orthogonal to the force vector produced by its corresponding spring member. 
     The inner blocks  40 ,  42  are configured in conjunction with the corner block  30  to facilitate containment of the molten salt electrolyte  15  within the electrolysis cell  2 . Thus, the inner blocks  40 ,  42 , in conjunction with other inner blocks and corner blocks  30 , may define a surrounding perimeter. In conjunction with a cathode, the surrounding perimeter may define a substantially leak-tight container adapted to contain the molten salt electrolyte  15 . The inner blocks may be of any shape. In one embodiment, the inner blocks are of a rectangular-solid shape. 
     The inner blocks  40 ,  42  and/or outer blocks  50 ,  52  may expand and contract due to heat fluctuations within the electrolysis cell, such as during the transition from startup to production conditions, and vice-versa. Thus, some of the blocks may expand from a first size to a second size, or may shrink from a first size to a second size. Likewise, the spring members  20  may apply various forces and/or be oriented in various states depending on the operating conditions of electrolysis cell  2 . For example, during startup the spring members  20  may apply a first force and/or be in a first compressive state, such as no or little compression. During production conditions, the spring members  20  may apply a second force or be in a second compressive state, such as a moderate to full compressive state due to expansion of the inner blocks  40 ,  42  and/or outer blocks  50 ,  52 . 
     Expansion of the inner blocks  40 ,  42  and/or outer blocks  50 ,  52  may also be realized in directions not coincidental to the compression of the spring members  20 . For example, one or more of the blocks may expand in a direction towards or away from the bath  15  and/or towards or away from the outer shell  60 . To facilitate such expansion, a gap  75  may be provided between the outer shell  60  and one or more of the blocks. 
     Like the inner blocks  40 ,  42 , the outer blocks  50 ,  52  may be of any shape. The outer blocks  50 ,  52  may provide a second layer of containment and/or support one or more inner blocks. The outer blocks  50 ,  52  may be coupled to the outer shell  60 . The outer blocks  50 ,  52  may comprise any suitable material. The outer blocks  50 ,  52  may be compressed via one or more spring members  20 , or may be free of compression from the spring members. 
     The inner sidewalls  40 , outer sidewalls  50  and/or corner blocks  30 , may be at least partially supported by an outer shell  60 . The outer shell  60  generally surrounds and supports at least some of the blocks, and may be made of any material suited to hold and support at least some of the blocks. In one embodiment, the outer shell  60  comprises a steel material. In the illustrated embodiment, the outer shell  60  surrounds the outer blocks  50 ,  52 , which surround the inner blocks  40 ,  42 . The outer shell  60  may also facilitate engagement of the spring members  20  with one or more blocks. For example, and as illustrated, the spring members  20   a ,  20   b  may be interconnected with the outer shell  60 , such as restrictively coupled to the outer shell  60 , to facilitate engagement of the spring members  20   a ,  20   b  with the corner blocks, inner blocks and/or outer blocks of the electrolysis cell  2 . In this regard, the outer shell  60  may include a corner portion  62  adapted to restrictively hold the spring members  20   a ,  20   b  in position during operation of electrolysis cell  2 . A top  64  may also be included to assist in vapor/heat control. 
     The spring members  20  may be suitably adapted to provide the force(s) that maintain the substantially leak-tight arrangement of the plurality of bath resistant blocks. One embodiment of a spring member  20  is illustrated in  FIG. 4 . In the illustrated embodiment, the spring member  20  includes a head  22 , which is coupled to a spring  24  via arm  23 . The head  22  includes a mating surface  25  adapted to mate with a surface of one of the plurality of bath resistant blocks, such as a corner block  30 , in a complimentary fashion. The spring member  20  further includes a container  27  adapted to contain spring  24  and at least partially contain the arm  23 . The container  27  includes sides  28 , which may be adapted for engagement with an outer shell portion of an aluminum electrolysis cell. The spring member  20  also includes a rear  26 , which provides a fixed surface to anchor the spring members  20 , but allow the spring member  20  to transmit the force of the springs. Such spring members  20  are available from, for example, Key Bellvilles. Other suitable spring members may be utilized. 
     As noted above, a variety of bath resistant block arrangements may be utilized in conjunction with spring members to facilitate production of a substantially leak-tight perimeter. Various ones of those arrangements are now described with reference to  FIGS. 5-9 . In one arrangement, and with reference to  FIG. 5 , a corner block arrangement may include an upper block  34  and lower block  36 . A first one of the spring members  20  may exert a force on the upper block  34  and correspondingly on an upper inner block  44 . A second one of the spring members  20  may exert a force on lower block  36  and thus, on lower inner block  46 . 
     In another arrangement, and with reference to  FIG. 6 , a corner block is adapted to only exert certain forces on the inner blocks of the sidewalls. In the illustrated embodiment, spring members  20  exert forces on inner sidewall  640  via corner blocks  30 . Forces are not exerted directly on outer sidewall  650  by spring members  20 . 
     In other arrangements, more than two sidewall layers may be utilized. For example, and with reference to  FIG. 7 , a cell may include an inner sidewall  740 , a middle sidewall  750  and an outer sidewall  760 . Spring members  20  may be oriented to exert forces on only the inner sidewall  740 , such as via corner block  30 . In other arrangements, the spring members  20  may exert forces on any of the middle sidewall  750  and/or outer sidewall  760 . 
     As noted above, various spring member arrangements may be utilized to force the blocks into the substantially leak-tight configuration. One alternative arrangement is illustrated in  FIG. 8 . In the illustrated embodiment, a single spring member  20  is utilized to provide a force on corner block  30 . In turn, corner block  30  applies a force to two inner sidewalls  840  to create the substantially leak-tight configuration. 
     Another spring member arrangement is illustrated in  FIG. 9 . In the illustrated embodiment, the spring members  920  comprise one member  922  attached to an inner portion of the outer shell  60  and another member  924  coupled to the side or outer portions of the outer shell  60  (e.g., corner portion  62 ). The spring members  920  may be utilized similar to that described above, so as to apply a force on corner block  30 , which may in turn apply force to inner sidewalls  940 . Outer sidewalls  950  may be utilized in conjunction with inner sidewalls  940 . 
     Methods of operating aluminum electrolysis cells are also provided. In one embodiment, and with reference to  FIG. 10 , a method includes the steps of maintaining a plurality of bath resistant blocks of an aluminum electrolysis cell in a substantially leak-tight configuration ( 1010 ), passing electricity through a molten salt electrolyte ( 1020 ), and producing aluminum in the aluminum electrolysis cell in the absence of a ledge ( 1030 ). Each of these steps are generally completed concomitant to one another. The step of maintaining the plurality of bath resistant blocks ( 1010 ) and the step of producing aluminum in the absence of a ledge ( 1030 ) may be facilitated via use of the above-described spring members. Thus, in one embodiment, a method includes the steps of applying force to at least some of the plurality of bath resistant blocks of an aluminum electrolysis cell to maintain the bath resistant blocks in a leak-tight configuration and/or produce aluminum in an aluminum electrolysis cell in the absence of a ledge. Other steps, such as many of those described in relation to the above referenced system, may be utilized in accordance with the present methods. 
     Various ones of the above features may be combined to yield various electrolysis cell, and systems and methods for operating an electrolysis cell in the absence of a ledge. Additionally, while the present invention has been described in terms of aluminum electrolysis cells, it will be appreciated that other metal electrolysis cells may utilize the sidewall configuration of the instant disclosure. Moreover, while various embodiments of the present invention have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention.