OXIDATION PROCESS

Abstract

A process for the removal of residual sulfur compounds from rich liquid caustic is disclosed where a single column containing two reaction zones catalytically oxidizes mercaptans to disulfide oils. The second reaction zone utilizes a bundle of vertical hanging fibers and is maintained as a gas continuous phase comprising from about 20% to about 100% by volume vapor. This process is especially useful as part of a hydrocarbon desulfurization process flow scheme.

Claims

1. A method of oxidizing mercaptans to disulfide oil comprising: providing a liquid stream containing mercaptans and a catalyst to a top portion of a column containing a bundle of vertical hanging fibers; mixing an oxygen containing gas with the liquid stream to form an admixture prior to contacting the admixture with the vertical hanging fibers; directing the admixture to flow down the fibers and to enter a gas continuous phase reaction zone comprising from about 20% to about 100% by volume vapor; oxidizing the mercaptans to disulfide oil as the admixture flows down the fibers in the reaction zone; collecting, separating and removing the disulfide oil from the column.

2. A method for regenerating a caustic solution comprising: providing a rich caustic liquid containing mercaptans; mixing the rich caustic liquid with a liquid catalyst to form a liquid caustic catalyst admixture; directing the liquid caustic catalyst admixture into a bottom section of a vertical column configured to cause the liquid caustic catalyst admixture to flow upward inside the column; injecting an oxygen containing gas into the liquid caustic catalyst admixture to form a gas liquid mix that flows upward inside the column entering a first reaction zone; oxidizing the mercaptans to disulfide oil in the first reaction zone forming an oxidized gas liquid mix; directing the oxidized gas liquid mix into a conduit positioned between a top tray and a bottom tray such that a liquid mix of disulfide oil and caustic exits the conduit onto a upper surface of the top tray that is fixedly attached to an upper section of the column; directing the liquid mix of disulfide oil and caustic into a shroud connected to a lower surface of the top tray where the liquid mix of disulfide oil and caustic contacts a bundle of vertical hanging fibers such that the liquid mix of disulfide oil and caustic flows down individual fibers in the bundle and into a second reaction zone; maintaining the second reaction zone as a gas continuous phase comprising from about 20% to about 100% by volume vapor; oxidizing mercaptans in the liquid mix of disulfide oil and caustic while the liquid mix of disulfide oil and caustic flows down the fibers in the second reaction zone to form a regenerated caustic and disulfide oil admixture; collecting the regenerated caustic and disulfide oil admixture on the bottom tray to allow separation of the disulfide oil from the regenerated caustic; and separately removing from the column a continuous stream of disulfide oil and a stream of regenerated caustic.

3. The method of claim 1 wherein the gas liquid mix flowing into the first reaction zone contacts supported packing material.

4. The method of claim 1 where the liquid catalyst is formed by mixing water, alkali metal hydroxide, and a chelated polyvalent metal catalyst.

5. The method of claim 4 wherein the chelated polyvalent metal catalyst is selected from the group consisting of cobalt phthalocyanine, iron phthalocyanine, vanadium phthalocyanine, and mixtures thereof.

6. The method of claim 1 wherein the oxygen containing gas is injected to achieve an oxygen concentration that is approximately equal to or exceeds the stoichiometric requirement for full oxidation of mercaptans into disulfide oil.

7. The method of claim 1 wherein an interior portion of the upper section of the column above the top tray is maintained as a nonexplosive environment.

8. The method of claim 7 where fuel gas or inert gas is introduced into the interior portion of the upper section.

9. The method of claim 1 where an off gas stream is removed from the upper section.

10. The method of claim 1 where an off gas stream is removed from the second reaction zone.

11. An oxidation reactor comprising; a column having a vertical axis, an upper section and a lower section; a first reaction zone positioned above the lower section; a second reaction zone above the first reaction zone and below the upper section, where the second reaction zone is defined by a top tray and a bottom tray, both trays fixedly attached to the column and both trays having upper and lower surfaces; a conduit positioned between the top and bottom trays configured to provide fluid communication between the lower surface of the bottom tray and the upper surface of the top tray; a shroud extending vertically downward from the lower surface of the top tray, where the shroud provides fluid communication between the upper surface of top tray and the second reaction zone; and a plurality of hanging fibers positioned parallel to the vertical axis contained within the shroud and extending down below a lower end of the shroud into the second reaction zone.

12. The reactor of claim 11 where the shroud further comprises a coalescing zone having one or more openings that are configured to allow liquid within the shroud to exit the shroud through the one or more openings following a flow path that is not parallel to the vertical axis.

13. A method of retrofitting an existing oxidation reactor comprising: inventorying the internals of an existing pre-used oxidation reactor having a vertical axis to determine existing components; measuring the internal dimensions of the reactor; installing new components or modifying the existing components in the reactor such that the reactor comprises: a top tray and a bottom tray located in an upper section of the reactor, both trays having upper and lower surfaces; a conduit positioned between the top and bottom trays configured to provide fluid communication between the lower surface of the bottom tray and the upper surface of the top tray; a shroud extending vertically downward from the lower surface of the top tray, where the shroud provides fluid communication between the upper surface of top tray and the top surface of the bottom tray; and a plurality of hanging fibers positioned parallel with the vertical axis contained within the shroud and extending down below a lower end of the shroud and above the top surface of the top tray.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] FIG. 1 schematically illustrates one possible application of my improved oxidation process as part of a hydrocarbon desulfurization process;

[0024] FIG. 2 is a cross-sectional view of one embodiment of my oxidation column;

[0025] FIG. 3 is a schematic representation of one possible design of the disengagement device connected to a shroud and defining a coalescing zone; and

[0026] FIG. 4 is a schematic representation of a cross-section portion of the disengagement device illustrated in FIG. 3.

DETAILED DESCRIPTION

[0027] As stated, my invention concerns a novel process for converting mercaptans to disulfide oils (DSO) using an oxidation reaction. This process can be integrated into a hydrocarbon desulfurization process as part of the caustic regeneration step that is designed to remove the sulfur compounds from rich caustic that were extracted from the rich hydrocarbon feed. More specifically, my invention eliminates the need for multiple excess vessels and additional unit operations by using a single column or other vessel to perform both the oxidation of mercaptans and the separation of the DSO formed from the treated caustic. The treated caustic preferably has less than 7.5 ppm by weight sulfur compounds and is suitable for recycle back to a hydrocarbon desulfurization process. My process utilizes a reaction zone maintained as a gas continuous phase comprising from about 20% to about 100% by volume vapor and utilizing vertically hanging fibers.

[0028] FIG. 1 illustrates one embodiment of my invention integrated into a hydrocarbon desulfurization process 100. However, my invention could be a stand-alone oxidation process that receives rich caustic form a number of varying sources. FIG. 1 shows a rich hydrocarbon feed 1, being treated in a counter current multiple stage extraction process. Typically, the rich hydrocarbon 1 is contaminated with mercaptan compounds, for example methyl and ethyl mercaptide. Lean or regenerated caustic 4 is fed to a last stage 2b where the lean caustic extracts the mercaptans from the hydrocarbons entering stage 2b after first being treated in stage 2a. The caustic is removed from the second stage as stream 5 where it contacts the incoming feed of rich hydrocarbons 1 in the first stage 2a. A rich or spent caustic is removed from stage 2a and the treated lean hydrocarbon is removed as desulfurized hydrocarbon 3 for further processing, for example, in an alkylation unit. The desulfurized hydrocarbon 3 is now substantially sulfur free, meaning the hydrocarbon has a sulfur level of <150 ppm total sulfur, preferably <30 ppm total sulfur and more preferably <10 ppm total sulfur.

[0029] The specific design of the hydrocarbon/caustic treatment section is not critical to my invention; however, a preferred design includes staged contactors operating in a counter-current configuration as schematically illustrated in FIG. 1, with a most preferred contactor configuration using fiber film liquid-liquid contactors to assist in the mass transfer of the mercaptans from the hydrocarbons into the caustic treatment solution. These as well as other contactor configurations are known to those skilled in the art. The caustic 4 can be any type known to the art of sweetening hydrocarbons, including solutions comprising NaOH, KOH, Ca(OH)2, Na2CO3, ammonia, extraction of organic acids, or mixtures thereof. Preferably, the caustic comprises aqueous potassium hydroxide solutions and aqueous sodium hydroxide solutions having concentration of from about 1% to about 50%, more preferably from about 3% to about 25%, still more preferably from about 5% to about 20%, by weight alkali hydroxide.

[0030] The rich caustic 6 removed from the hydrocarbon desulfurization process is mixed with a liquid catalyst 7, preferably as a fresh make-up stream of the liquid catalyst in order to supplement the catalyst that is lost through degradation as the catalyst moves with the caustic throughout process 100. A preferred liquid catalyst is made by adding metal phthalocyanine catalyst to an aqueous solution of alkali metal hydroxide. Another preferred liquid catalyst solution further contains an alcohol and at least one carboxylic acid, such as naphthenic or ethylhexanoic acid.

[0031] In one alternative embodiment of my invention a small volume solvent stream 13 can be added to the rich caustic 6. Preferably, this solvent stream 13 is obtained from a downstream solvent washing step 15 and may contain a small amount of DSO. The solvent stream can be mixed with the rich caustic prior to entering the single oxidizer column 8 or it could injected as a separate stream into the bottom of the single oxidizer column 8. The solvent can be any light hydrocarbon or mixture of light hydrocarbons that will assist in the separation of the DSO from the caustic solution after oxidation of the mercaptans, however, preferred solvents included naphtha and kerosene. Although the exact mechanism of how the solvent improves the separation of DSO from the oxidized caustic is not specifically known, one theory is that the solvent has a much higher solubility for DSO than does caustic, with their differential of solubility providing an extractive driving force. This effect is further magnified because the single oxidizer column, as will be explained in more detail below, utilizes fiber-film technology that provides higher interfacial surface area than other forms of contacting devices. The amount of solvent, based on the volume percent of the rich caustic feed, introduced into the oxidizer, either with the rich caustic or separately, is not especially critical to my invention as long as a minimum amount is used so as to maximize separation performance within the single column oxidizer 8. As mentioned only a small volume of solvent is needed, with a preferred range of minimum solvent injection from about 0.1 vol % to about 10.0 vol %, preferably from about 0.5 vol. % to about 5.0 vol. %, of the rich caustic feed 6.

[0032] In addition to the rich caustic, the liquid catalyst and solvent that are fed to the single column oxidizer 8, an oxidant 9, such as air, hydrogen peroxide, or other oxygen containing gas(es), is also introduced to the single column oxidizer 8. The amount of oxidant added to the oxidizer is sufficient to achieve 90+% oxidation and conversion of the mercaptans originally present in the rich hydrocarbon to disulfide compounds, most preferably 99+% oxidation. A second, optional, oxidant feed 80 (see FIG. 2) may be added to oxidizer 8 in order to maintain a second reaction zone in a gas continuous phase comprising from about 20% to about 100% by volume vapor.

[0033] A preferred range of operating conditions for the single column oxidizer 8 includes a temperature of from about 75° F. to about 200° F. and a caustic flow rate of as high as 60 LHSV, but preferably from about 100° F. to about 150° F. and less than 5 LHSV. The operating pressure of my process can be from atmospheric to about 100 psig.

[0034] The oxidized or lean caustic 14 removed from the the single column oxidizer 8 can be subsequently treated in a solvent washing process 15 where solvent 16 is contacted with the lean caustic 14, preferably in a counter current flow configuration to remove any residual DSO that was not separated in the single column oxidizer 8. A fully regenerated caustic 18 is removed from the the solvent washing step 15. An amount of make-up fresh caustic 19 can be added before the generated caustic 4 is recycled back to the extraction stages 2a & 2b.

[0035] Turning next to the specifics of the single column oxidizer 8, FIG. 2 schematically illustrates one embodiment of my invention where catalytic oxidation of the mercaptans to DSO along with separation of the oxidized caustic occurs in a single vessel. In other words, no other vessels or equipment are needed to process a rich caustic streaming containing up to 50,000 ppm total sulfur compounds and produce an oxidized caustic stream having less than 5 ppm mercaptans and less than 400 ppm total sulfur compounds. The oxidizer 8 is preferably a vertical column having a vertical axis 8a. Column 8 has a lower section 29 where the liquid caustic catalyst admixture 6b is introduced. As mentioned this liquid admixture 6b can comprise rich caustic, liquid catalyst, and solvent. The liquid admixture 6b is directed up flow within column 8 where it is mixed with oxidant 9, preferably air, that is introduced into the lower section 29 through one or more spargers 20. The rate of oxidant flow is such that the oxidant is adequately distributed throughout the column's first reaction zone 22. The resulting gas liquid mix flows upward in column in column 8 and enters a first reaction zone 22. This reaction zone can be filled with random packing material such as balls, rings or saddles, structured packing such as corrugated plates, knitted fibers, or hanging fibers supported as a bed of solids between optional bed supports 21 and 23. The packing material provides a high surface area for improved gas/liquid contacting. Oxidation of the mercaptans begins to occur in the first reaction zone 22 as the gas liquid mix moves upward through column 8.

[0036] As the gas liquid mix exits the first reaction zone 22 it is directed to and flows into conduit 25. The lower opening of conduit 25 is at or below a lower surface 24a of bottom tray 24 and provides a fluid path from below the bottom tray 24 and upper surface 31b of top tray 31 and the upper section 27 of column 8. At the upper end of conduit 25 is preferably a cap 26 that functions to prevent carryover of liquid into the excess off-gas 12. Preferably, upper section 27 of column 8 is maintained as a nonexplosive environment by introducing a gas 10, for example fuel gas, inert gas or mixture of such gases. Excess gas is removed as an off-gas 12 and is typically sent for disposal, for example, by incineration.

[0037] The liquid mix of disulfide oil and caustic exiting conduit 25 onto the upper surface 31b of top tray 31 is directed to an opening in in the top tray an into a shroud 30 connected to the lower surface 31a of the top tray. Within shroud 30 is a plurality or bundle of vertical hanging fibers 45 that are generally aligned, i.e., generally parallel, with longitudinal axis 8a of column 8. The bundle of vertical hanging fibers provides a large surface area to allow the reactants to contact and to eventually separate the resultant immiscible liquids formed.

[0038] Preferably, the vertical hanging fibers comprise long thin filaments or ribbons made of materials selected from a group consisting of, but not limited to, metal fibers, glass fibers, polymer fibers, graphite fibers and carbon fibers that meet two criteria: (1) the fiber material must be preferentially wetted by the admixture of at least two immiscible liquids; and (2) the fibers must be of a material that will not contaminate the process or be destroyed by it, such as by corrosion. Further, must allow mass transfer and separation in a non-dispersive manner.

[0039] The lower end or bottom of the shroud 30 terminates in a separation zone 52 that is defined between a liquid hydrocarbon top surface 79, i.e. a mix of DSO and solvent, and the lower surface 31a of the top tray 31. Optionally, a second stream of oxidant 80 can be injected or otherwise mixed with the liquid mix of disulfide oil and caustic as it enters the top of shroud 30. The liquid mix of disulfide oil and caustic contacts a bundle of vertical hanging fibers such that the liquid mix of disulfide oil and caustic flows down individual fibers in the bundle composing a second reaction zone.

[0040] The second reaction zone contained inside the shroud 30 is maintained as a gas continuous phase comprising from about 20% to about 100% by volume vapor. The excess of oxidant in this vapor continuous phase provides excellent mass transport conditions for the oxidation of remaining mercaptans. Because the flow of gas and liquid are co-current, there is no restriction on flow rate due to flooding. The opening of the shroud must be located above the liquid hydrocarbon phase 51. The remaining mercaptans in the caustic are oxidized and converted to DSO in the second reaction zone. The upper surface 24b of bottom tray 24 collects the liquid mix in the separation zone 52. The collection of the liquid mix is allowed to separate into a hydrocarbon upper layer 51 and a lower aqueous layer 50. The upper hydrocarbon layer 51 comprises DSO and/or solvent, and the lower aqueous layer 50 comprises the liquid catalyst and the oxidized, substantially sulfur free, lean/regenerated caustic solution. The upper layer 51 and lower layer 50 are removed from column 8 via lines 11 and 14, respectively, at variable flow rates in order to maintain a residence time sufficient to achieve separation of the two layers defined by boundary interface 72. The removed DSO and solvent in the upper layer is sent to storage or for further processing. The removed caustic and catalyst from the lower layer is preferably sent to a solvent wash step 15 (see FIG. 1). Any excess gas in the separation zone 52 is removed via line 40.

[0041] In a further embodiment of my invention, the shroud that comprises the second reaction zone may further comprise two zones; an upper contact zone and an enhanced coalescing zone (ECZ). The ECZ is located at the bottom of the shroud and is defined by a disengagement device configured to allow a portion of the admixture of liquids within the shroud to flow radially outward to exit the shroud through the one or more openings following a flow path that is not parallel to the vertical axis to contact a coalescing surface associated with the disengagement device. The upper contact zone is defined by the upper portion of the shroud. Within the upper contact zone of the shroud the admixture of liquids fed to the vertical hanging fibers is contained within the shroud and contacts the fibers as the liquids flow downward parallel to the vertical axis of column 8. The walls of the shroud in the upper and lower contact zones are solid (i.e., contain no openings) and can take the form of a tube-like or conduit like structure that can be round, oval, square, rectangular or any shape that ensures contact of the hanging fibers with the admixture of liquids. The actual cross-sectional shape of the shroud is not important to the invention and the shroud may or may not have the same diameter or shape as the disengagement device. Because the upper contact zone of the shroud has no openings in the wall, the admixture of liquids must flow downward, parallel to the vertical axis.

[0042] The disengagement device can be an extension of the bottom section of the shroud and defines the ECZ. The hanging fibers are positioned vertically within the shroud and within the disengagement device hanging generally parallel to the vertical axis of the column. The fibers within the disengagement device can be a separate independent bundle or an extension of the fiber bundle that is contained within the upper contact zone.

[0043] In the ECZ, a portion of the admixture of liquids exits the disengagement device following a radial flow path that is not parallel to the vertical axis defined by the hanging fibers. As the portion of the admixture of liquids exits the disengagement device, a portion of one of the immiscible liquids coalesces to form a coalesced liquid. Depending on the properties of the coalesced liquid, droplets, rivulets or small steams are formed that fall downward on the outside of the disengagement device and parallel to the vertical axis. The coalesced liquid, if it was originally a portion of the higher density liquid, will flow downward and will settle into the lower phase layer at the bottom of the vessel interior.

[0044] The disengagement device can be a separate structure connected to the shroud or an extension of the shroud provided that it allows the admixture of liquids to exit both radially through one or more openings and through an open end parallel to the vertical axis as opposed to the radial flow path that is not parallel to the vertical axis. The open end of the disengagement device prevents pressure drop problems associated with prior art attempts to eliminate or reduce dispersions caused by low interfacial tension systems. A preferred disengagement device comprises a vertical segment connected to the bottom of the shroud at the end of the lower contact zone and having one or more side openings or holes that allow non-parallel flow of a portion of the admixture of liquids. The disengagement device can be a perforated extension of the shroud at the bottom of the lower contact zone, preferably in the form an annulus or alternatively, it can be a wire screen or other cage-like support structure. Most preferably, the disengagement device has associated therewith a coalescing surface configured to contact the portion of the admixture of liquids that exits radially from the disengagement device following a flow path that is roughly perpendicular or at approximately a right angle relative to the vertical axis.

[0045] The coalescing surface is selected from the group consisting of wire grid, porous metal wall, open-celled sponge, woven wire screen, knitted wire mesh, woven or non-woven fibrous material of metal, polymer resins or combinations of metal and polymer resins, multiple co-woven filaments, packing, fiber filters, and combinations of media layer on each other. Materials used to fabricate the coalescing surface include, stainless steels, Duplex steels, alloys, plastics, fluoropolymers, fibrous components (polyolefin, polyesters, glass fibers, and like materials), and mixtures of same. The coalescing surface is most advantageously configured to interact with one of the liquids in the admixture and to form small droplets. These droplets then grow in size to larger droplets of the heavier phase that can then be easily settled out from the lighter liquid by gravity. The volumetric void fraction of the coalescing surface should be less than 98% and most preferably less than or equal to 96%.

[0046] Wire mesh coalescing surfaces can comprise a combination of wires and fibers in order to create a maximum surface area for droplets to coalesce. In many cases the wire and fiber are from a different construction material, where one is hydrophilic (e.g. metal) and the other is hydrophobic (for example, polyolefin or fluoropolymer) which enhances the separation. There is an increased coalescence effect at the junction point between both materials. Therefore, using both the metal and polymeric materials will increase coalescing efficiency significantly. The coalescence surface of our invention can take the form of a physical wrapping around, or positioned adjacent to, slots, holes, perforations, or other openings in the disengagement device. This wrapped coalescence surface is held in place by bands, ties, clamps or other fasteners attached to the external surface of the disengagement device provided that the exiting admixture of liquids is forced to contact the coalescing surface.

[0047] Most preferably, the coalescence surface is incorporated in an annulus or ring that forms part of the vertical length of the disengagement device and defines the enhanced coalescing zone (ECZ). On the inner ring or wall of the annulus are a plurality of holes that allow the admixture of liquids to pass into the inside of annulus where the admixture contacts the coalescing surface that is positioned or packed into the annulus. The outer ring or wall of the annulus likewise has a plurality of holes, slots, perforations, screen or grid openings or other such openings to allow the admixture to pass to the outside of the disengagement device. The type of openings used in the outer wall may or may not be the same as that used on the inner wall. Regardless of whether the coalescing surface is located in an annulus or wrapped around a perforated structure in the disengagement device, the volumetric void fraction of the coalescing surface is preferably in the range of from about 90% to about 99%, more preferably from about 95% to 98%. The coalescing surface should preferably occupy a volume that is sufficient to eliminate dispersion and form a coalesced liquid as either droplets or a continuous liquid stream. The amount of coalescing surface can be varied to increase or decrease the holdup or residence time necessary to form the coalesced liquid. A preferred coalescing material is a co-woven type material comprised of 316 stainless steel and polytetrafluoroethylene (Teflon) fiber filaments, with very fine fiber size and having an installed density of around 15 to 30 lb/ft.sup.3.

[0048] FIG. 3 illustrates one possible embodiment of the disengagement device 60 that is shown as an addition to the bottom of shroud 30. Like reference numbers have the same meaning as previously described. The disengagement device 60 defines an enhanced coalescing zone (ECZ) and has an open end 62. In the particular embodiment shown in FIG. 3, the disengagement device 60 comprises an annulus 64, which becomes an extension of shroud 30 and provides side openings 66 to allow radial flow of the admixture of liquids to exit the disengagement device in flow path that is not parallel to axis 8a. A cross-section of this annulus 64 is illustrated in FIG. 4 showing the bundle of hanging fibers 45 being contained within the inner wall 68 that forms an interior volume 70.

[0049] Both the inner wall 68 and outer wall 60 of the annulus 64 contain one or more side openings 66. Inside the annulus is located the coalescing surface 63. The preferred coalescing surface has a volumetric void fraction in the range of from about 90% to about 99%, more preferably from about 95% to 98%. A preferred coalescing material is a co-woven type material comprised of 316 stainless steel and polytetrafluoroethylene (Teflon) fiber filaments, with very fine fiber size and having an installed density of about 15 to about 30 lb/ft'. The amount of coalescing material added to annulus, or in the cases of a wrapped configuration, is sufficient such that there is enough residence or hold up time of the liquids in the material to cause the liquid to coalesce. The plurality of openings 66 allow a portion of the admixture of liquids to flow through the annulus in a radial flow path that is non-parallel to the vertical axis 8a. Preferably, the one or more openings 66 represent at least a 50% open area in the walls of the annulus. These openings can be slots, holes, punctures, or perforations of any shape or dimension.

[0050] As the admixture passes through the annulus 64 it contacts the coalescing surface 63 whereby any dispersion in the admixture is collapsed to form droplets 75 (see FIG. 2). These droplets 75 continue to grow until they either fall through the coalescing material or re-enter the fiber bundle or exit through the openings 66 in the outer wall 60. In other words, the formation and growing of the droplets 75 is the coalescing of one of the liquids in the admixture, typically the denser liquid. When the droplets are of the denser liquid, they grow and fall, dropping downward to become part of the lower liquid in layer 50. Because little or none of the dispersion survives the coalescing surface 63, a distinct phase interface 72 is formed between the higher density liquid in layer 50 and the lower density layer 51. This eliminates carry over of the higher density liquid and allows for precise control of interface level 72, which avoids pump cavitation and the contamination of the lighter liquid in process line 11.

[0051] While temperature and pressure in the second reaction zone may range from about 75° F. to about 200° F. and from 0 psig to about 500 psig, preferably both reaction zones are maintained at a temperature in the range of about 100° F. to about 150° F. and a pressure in the range of about 0 psig to about 100 psig.

[0052] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various application such specific embodiments without departing from the generic concept, and therefore such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation.

[0053] The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention. Thus, the expressions “means to . . . ” and “means for . . . ”, or any method step language as may be found in the specification above or the claims below, followed by a functional statement, are intended to define and cover whatever structural, physical, chemical or electrical element or structure, or whatever method step, which may now or in the future exist which carries out the recited function, whether or not precisely equivalent to the embodiment or embodiments disclosed in the specification above, i.e., other means or steps for carrying out the same function can be used; and it is intended that such expressions be given their broadest interpretation within the terms of the following claims.