Device and method for recovering a precipitated solid inorganic final product consisting of phosphorus, nitrogen and an element X

Abstract

The present invention relates to a device and a method for recovering a large and dry precipitated solid inorganic final product (3D), consisting of phosphorus, nitrogen and an element X selected from the alkaline-earth metals, from a first fluid (1) consisting of at least one divalent cation X2+ mixed with a second fluid (2) containing phosphorus and nitrogen, said device including at least one first reactor (19) which is intended for a primary crystallization reaction, has any shape, and is connected to a second spiral-shaped reactor (20) for secondary crystallization/deposition.

Claims

1. A device for recovering a large and dry precipitated solid inorganic final product (3D) consisting of phosphorus, nitrogen and of an element X selected from among alkaline-earth metals Be, Mg, Ca, Sr, Ba, Ra, formed from a first phosphorus- and nitrogen-containing fluid (1) mixed with a second fluid (2) consisting of at least one divalent cation X.sup.2+ selected from among Be.sup.2+, Mg.sup.2+, Ca.sup.2+, Sr.sup.2+, Ba.sup.2+, Ra.sup.2+, said device comprising: at least one first reactor (19) for primary reaction-crystallization, at least one apparatus (5) for separating particles and discharging the secondary remnant (6B), at least one apparatus for adjusting the pH (40B), at least one apparatus (30) for injecting a gas (18), at least one apparatus (15) for providing the first fluid (1), and at least one apparatus (16) for providing the second fluid (2), wherein said device comprises at least one second reactor (20) for secondary crystallization decantation having a spiraled geometrical shape, said second reactor (20) being directly connected to said first reactor (19) through at least one valve (51) allowing the reaction bed of the first reactor (19), containing a small (3A) and intermediate (3B) solid inorganic product becoming gradually bigger, to be transferred into the reactor (20) for performing therein secondary crystallization before precipitating in order to obtain a wet and large precipitated solid inorganic final product (3C).

2. The device according to claim 1, wherein at least one initiation channel (17) containing said small (3A) and intermediate (3B) solid inorganic product, connects said apparatus (5) for separating particles and discharging the secondary remnant (6B) to at least an injection conduit (15A) for the first fluid (1) in the first reactor (19) for initiating the growth of said small (3A) and intermediate (3B) solid inorganic product in the first reactor (19) and in the second reactor (20) in order to obtain a wet and large precipitated solid inorganic final product (3C).

3. The device according to claim 1, wherein at least one conduit (52) for suction of the gas upper volume of the apparatus (5) connects the apparatus (5) to said apparatus (30) for injecting a gas (18) for promoting the recovery of said small (3A) solid inorganic product.

4. The device according to claim 1, wherein said second reactor (20) includes at least one reaction conduit (7A, 7B, 7C, 7D) forming a plurality of turns (4) of variable diameter.

5. The device according to claim 4, wherein the plurality of turns (4) have a radius which may vary between 0.2 m and 4.0 m.

6. The device according to claim 4, wherein said at least one reaction conduit (7A, 7B, 7C, 7D) of the second reactor (20) has a passage section comprised between 20 cm.sup.2 and 2,000 cm.sup.2.

7. The device according to claim 1, wherein said second reactor (20) is of an elongated shape defining a substantially vertical longitudinal axis (10).

8. The device according to claim 1, wherein the second spiral reactor (20) for secondary crystallization-decantation surrounds the first reactor (19) for primary reaction-crystallization.

9. The device according to claim 1, wherein the second reactor (20) for secondary crystallization-decantation is integrated to the inside of the first reactor (19) for primary reaction-crystallization.

10. The device according to claim 1, wherein the first reactor (19) is of a cylindrical, cylindro-frustoconical, conical, truncated conical, rectangular, square, or spiral shape.

11. The device according to claim 1, wherein said wet and large precipitated solid inorganic final product (3C) is recovered by the apparatus for separating particles (5) after precipitation in said second crystallization-decantation reactor (20) and in said first reactor (19), said device comprising: at least one apparatus (15) for providing the first fluid (1) giving the possibility of injecting said first fluid (1) through an injection conduit (15A) in said first reactor (19), at least one apparatus (16) for providing the second fluid (2) giving the possibility of injecting said second fluid (2) through an injection conduit (16A) in said first reactor (19), at least one apparatus (40B) for adjusting the pH connected to said first reactor (19) through a conduit (41), the at least one valve (51) connecting the first reactor (19) and the second reactor (20), the at least one valve (51) being dispersed along the totality of the height of said first reactor (19) and of said second reactor (20), the height being measured relatively to the second reactor (20) of elongated shape defining a substantially vertical longitudinal axis (10), the small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger, falling by gravity precipitation in said at least one conduit (7A, 7B, 7C, 7D) of the second reactor (20) as soon as the weight of said small (3A) and intermediate (3B) solid inorganic product gives the possibility of overcoming the rising flow of the mixture of the first fluid (1) and of the second fluid (2) and the downflowing small (3A) and intermediate (3B) solid inorganic product is conveyed by gravity by sliding along the walls of said second reactor (20) and through at least one transfer conduit (22) towards the bottom of the first reactor (19) in order to end up with a wet and large precipitated solid inorganic final product (3C) being discharged towards the apparatus for separating particles and discharging the secondary remnant (5), at least one conduit (18A) for injecting gas (18) into said first reactor (19).

12. The device according to claim 1, wherein said first fluid (1) is mixed with said second fluid (2) in the upper portion of said first reactor (19) in order to form a small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger, before injecting said small (3A) and intermediate (3B) solid inorganic product into the second reactor (20), where the ascent rate of the first fluid (1) mixed with said second fluid (2) is comprised between 0.01 m/s and 3 m/s.

13. The device according to claim 1, wherein said at least one spiral reaction conduit (7A, 7B, 7C, 7D) of the second reactor (20) has a tilt angle (10A) of the turns preferably comprised between 10 and 70, the tilt angle (10A) being defined relatively to a horizontal axis (10B) substantially parallel to the ground.

14. The device according to claim 1, wherein the second reactor (20) comprises at least one spiral-shaped reaction conduit (7A, 7B, 7C, 7D) for which the number of turns (4) is comprised between 1 and 20 relatively to the height of the second reactor (20) of elongated shape defining a substantially vertical longitudinal axis (10).

Description

(1) The present invention is accompanied by the following figures:

(2) FIG. 1: block diagram of the device of the present invention showing a substantially vertical axis (10)

(3) FIG. 2: left view of the device of the present invention

(4) FIG. 3: right view of the device of the present invention

(5) FIG. 4: top view of the device of the present invention

(6) FIG. 5: perspective view of the device of the present invention

(7) FIG. 6: front view of the device of the present invention showing a substantially horizontal axis (10B) and a tilt angle (10A) of a turn (4).

(8) FIG. 7: perspective view of the bottom of the device of the present invention

(9) FIG. 8: rear view of the device of the present invention

(10) FIG. 9: in order to ensure proper dosage of the reagents, and therefore maximalization of the economical cost-effectiveness of the laboratory or site tests have to be carried out.

(11) These tests (here as a Jar-test) give the possibility of defining the optimum amount of soda (NaOH) and of magnesium (MgCl or MgO) which has to be added.

(12) FIG. 10: shows dry NH.sub.4PO.sub.4X, i.e. crystals of the precipitated solid inorganic final product (3) consisting of phosphorus, nitrogen and an element X.

(13) The present invention relates to a device for recovering a large and dry (3D) precipitated solid inorganic final product consisting of phosphorus, nitrogen and of an element X selected from among earth-alkaline metals Be, Mg, Ca, Sr, Ba, Ra formed from a first phosphorus- and nitrogen-containing fluid (1) mixed with a second fluid (2) consisting of at least one divalent cation X.sup.2+ selected from among Be.sup.2+, Mg.sup.2+, Ca.sup.2+, Sr.sup.2+, Ba.sup.2+, Ra.sup.2+, said device comprises the following means: at least one first reactor (19) for primary reaction-crystallization, at least one apparatus (5) for separating particles and discharging the secondary remnant (6B), at least one apparatus for adjusting the pH (40B), at least one apparatus for injecting (30) a gas (18), at least one apparatus (15) for providing the first fluid (1), at least one apparatus (16) for providing the second fluid (2),
characterized in that said device comprises at least one second reactor (20) for secondary crystallizationdecantation having a spiraled geometrical shape, said second reactor (20) being directly connected to said first reactor (19) through at least one valve (51) allowing the reaction bed of the first reactor (19), containing a small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger, to be transferred into the reactor (20) for performing therein secondary crystallization before precipitating in order to obtain a wet and large precipitated solid inorganic final product (3C).

(14) The device according to present invention has at least one initiation channel (17) containing said small (3A) and intermediate (3B) solid inorganic product, connecting said apparatus (5) for separating particles and discharging the secondary remnant (6B) to at least a conduit (15A) for injecting the first fluid (1) into the first reactor (19) for initiating the filling volume of said small (3A) and intermediate (3B) solid inorganic product in the first reactor (19) and in the second reactor (20) in order to obtain a wet and large precipitated solid inorganic final product (3C).

(15) The device according to the present invention has at least one conduit (52) for suction of the gas upper volume of the apparatus (5) connecting the apparatus (5) to said apparatus (30) for injecting a gas (18) in order to promote recovery of said small solid inorganic product (3A).

(16) The device according to the present invention comprises a second reactor (20) including at least a reaction conduit (7A, 7B, 7C, 7D) forming a plurality of turns (4) with a variable diameter. Preferably, the second spiral reactor (20) comprises turns (4) having a radius which may vary between 0.2 m and 4.0 m, preferably between 0.4 m and 2.0 m, more preferentially between 0.5 m and 1.0 m.

(17) Preferably, the second spiral reactor (20) comprises at least one reaction conduit (7A, 7B, 7C, 7D) having a passage section comprised between 20 cm.sup.2 and 2,000 cm.sup.2, preferably between 80 cm.sup.2 and 1,300 cm.sup.2, more preferentially between 180 cm.sup.2 and 500 cm.sup.2.

(18) Preferably, the second spiral reactor (20) is of an elongated shape defining a substantially vertical longitudinal axis (10) (+/10%).

(19) Preferably, the second spiral reactor (20) for secondary crystallizationdecantation surrounds the first reactor (19) for primary reaction-crystallization.

(20) Preferably, the second reactor (20) for secondary crystallizationdecantation is comprised inside the first reactor (19) for primary reaction-crystallization.

(21) Preferably, the first reactor (19) is of a cylindrical, truncated cylindro-conical, conical, truncated conical, rectangular, square or spiral-shaped shape.

(22) Preferably the wet and large precipitated solid inorganic final product (3C) is recovered by the apparatus for separating particles (5) after precipitation in said second reactor (20) for crystallization-decantation and in said first reactor (19), said device comprising: at least one apparatus (15) for providing the first fluid (1) giving the possibility of injecting said first fluid (1) through an injection conduit (15A) in said first reactor (19), at least one apparatus (16) for providing the second fluid (2) giving the possibility of injecting said second fluid (2) through an injection conduit (16A) in said first reactor (19), at least one apparatus (40B) for adjusting the pH connected to the first reactor (19) through a conduit (41), at least one connection valve (51) connecting the first reactor (19) and the second reactor (20), said valves (51) being dispersed along the totality of the height of said first reactor (19) and of said second spiral reactor (20), the height being measured relatively to the second reactor (2) of an elongated shape defining a substantially vertical longitudinal axis (10) (+/10%), the small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger while falling by gravity precipitation into said at least one conduit (7A, 7B, 7C, 7D) of the second reactor (20) as soon as the weight of said small (3A) and intermediate (3B) solid inorganic product gives the possibility of overcoming the rising flow of a mixture of the first fluid (1) and of the second fluid (2) and the small (3A) and intermediate (3B) solid inorganic product flowing down is transferred by gravity by sliding along the walls of said second reactor (20) and through at least one transfer conduit (22) towards the bottom of the first reactor (19) in order to end up with a large and wet precipitated solid inorganic final product (3C) being discharged towards the apparatus for particle separation and discharge of the secondary remnant (5), at least one conduit (18A) for injecting gas (18) into said first reactor (19).

(23) The device according to the present invention comprises an element X selected from among Cd, Cr, Co, Cu, Eu, Ge, Fe, Pb, Mn, Ni, Pt, Sn, V, Zn, Ti, Si, Po, Hg, Yb, Sm, Md, No.

(24) The device according to the present invention comprises an element X.sup.2+ selected from among Cd.sup.2+, Cr.sup.2+, Cu.sup.2+, Eu.sup.2+, Ge.sup.2+, Fe.sup.2+, Pb.sup.2+, Mn.sup.2+, Ni.sup.2+, Pt.sup.2+, Sn.sup.2+, V.sup.2+, Zn.sup.2+, Ti.sup.2+, Si.sup.2+, Po.sup.2+, Hg.sup.2+, Yb.sup.2+, Sm.sup.2+, Md.sup.2+, No.sup.2+.

(25) The device according to the present invention comprises a first fluid (1) mixed with said second fluid (2) in the upper portion of said first reactor (19) in order to form a small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger, before injection of said small (3A) and intermediate (3B) solid inorganic product into the second reactor (20), where the ascent rate of the first fluid (1) mixed with said second fluid (2) is comprised between 0.01 m/s and 3 m/s.

(26) The device according to the present invention comprises at least one spiral reaction conduit (7A, 7B, 7C, 7D) of the second reactor (20) having a tilt angle (10A) of the turn preferably comprised between 10 and 70, preferably between 20 and 60, or preferably between 48 and 55, the tilt angle (10A) being defined relatively to a horizontal axis (10B) substantially parallel to the ground (+/10%).

(27) The device according to the present invention comprising a second reactor (20) consisting of at least one spiral-shaped reaction conduit (7A, 7B, 7C, 7D) for which the number of turns (4) is comprised between 1 and 20, preferably between 4 and 10, more preferentially between 4 and 6 relatively to the height of the second reactor (20) of elongated shape defining a substantially vertical longitudinal axis (10) (+/10%).

(28) Preferably, the weight of a single crystal of the large and dry (3D) precipitated solid inorganic final product is comprised between 0.001 g and 1.5 g, 0.005 g and 1.3 g, 0.006 g and 1.2 g, preferably between 0.01 g and 1.0 g, 0.01 g and 0.09 g, 0.01 g and 0.05 g, more preferentially between 0.1 g and 0.9 g, 0.3 g and 0.7 g, 0.4 g and 0.6 g. Preferably said second spiral rector (20) is of an elongated shape defining a substantially vertical longitudinal axis (10) (+/10%).

(29) Preferably, the size of a crystal of said large and dry precipitated solid inorganic final product (3D) is comprised between 1 mm and 10 mm, preferably between 2 mm and 9 mm, more preferentially between 3 mm and 8 mm, still more preferentially between 4 mm and 7 mm, between 5 mm and 6 mm.

(30) The present invention relates to a method for recovering a large and dry precipitated solid inorganic final product (3D) consisting of phosphorus, nitrogen and an element X selected from among the earth-alkaline metals Be, Mg, Ca, Sr, Ba, Ra, formed from a first fluid (1) phosphorus- and nitrogen-containing fluid mixed with a second fluid (2) consisting of at least one divalent cation X.sup.2+ selected from among Be.sup.2+, Mg.sup.2+, Ca.sup.2+, Sr.sup.2+, Ba.sup.2+, Ra.sup.2+, said method operating at a temperature comprised between 20 C. and 90 C., and including the following steps: A) injecting the first fluid (1) through at least an injection point (9) connected to at least one first reactor (19) for primary reaction-crystallization, B) injecting a gas (18) into said first reactor (19) at at least one injection point (50), C) adjusting the pH (40B) by injecting a basic solution, D) injecting the second fluid (2) through at least one injection point (8) connected to said first reactor (19) for primary reaction-crystallization, E) growing crystals of a small (3A) and intermediate (3B) solid inorganic product becoming gradually bigger in the said first reactor (19), F) increasing the dwelling time of the crystals of the small (3A) and intermediate (3B) solid inorganic product by transferring a portion of the first fluid (1), of a portion of the second fluid (2) mixed with the basic solution and of a portion of the crystals of the small (3A) and intermediate (3B) solid inorganic product of the first reactor (19) towards a second spiraled reactor (20) for secondary crystallization-decantation, G) migrating by gravity crystals of a wet and large precipitated solid inorganic final product (3C) of the second spiraled reactor (20) towards the first reactor (19) through a transfer conduit (22) connecting the second reactor (20) to the first reactor (19), H) separating crystals of a wet precipitated solid inorganic final product (3C) and of the secondary remnant (6B) at at least one device (5) for separation of particles and discharge of the secondary remnant, I) drying crystals of the wet and large precipitated solid inorganic final product (3C).

(31) The method according to the present invention may comprise an additional step J) for initiating crystallization by injection into the first reactor (19) of a fraction of the small (3A) and intermediate (3B) solid inorganic product by means of at least one initiation channel (17) connecting said apparatus (5) for separating particles and discharging the secondary remnant (6B) towards said first reactor (19).

(32) The method according to the present invention may comprise an additional step K) for suction of the gas upper volume of the apparatus (5) in which at least one conduit (52) for suction of the gas upper volume of the apparatus (5) connects the apparatus (5) to said apparatus (30) for injecting a gas (18) for promoting recovery of said small solid inorganic product (3A).

(33) Preferably, in step D) the injection point (8) is located at a height greater than that of the valve (51) the highest in height (i.e. the valve the closest to the injection points (8) and (9)).

(34) Preferably, the gas (18) of step B) is selected from among air, biogas, gas poor in CO.sub.2.

(35) Preferably, the pH of step C) attains a pH comprised between 8 and 11, preferably between 9 and 10.

(36) Preferably, said element X is selected from among Cd, Cr, Co, Cu, Eu, Ge, Fe, Pb, Mn, Ni, Pt, Sn, V, Zn, Ti, Si, Po, Hg, Yb, Sm, Md, No.

(37) Preferably X.sup.2+ is selected from among Cd.sup.2+, Cr.sup.2+, Co.sup.2+, Cu.sup.2+, Eu.sup.2+, Ge.sup.2+, Fe.sup.2+, Pb.sup.2+, Mn.sup.2+, Ni.sup.2+, Pt.sup.2+, Sn.sup.2+, V.sup.2+, Zn.sup.2+, Ti.sup.2+, Si.sup.2+, Po.sup.2+, Hg.sup.2+, Yb.sup.2+, Sm.sup.2+, Md.sup.2+, No.sup.2+.

(38) The present invention relates to a large and dry precipitated solid inorganic final product (3D) which may be obtained by the method of the present invention. In the present invention, the large and dry precipitated solid inorganic final product (3D) may be used as a fertilizer.

(39) The extracted crystals (3C) may be sifted with a sieve for which the size of the meshes may vary. The crystals of the wet final product (3C) will then be dried in a specific oven, by injecting hot air from the methanization unit. The passing particles may be reintroduced at the head of the decanter, in the top tank of the reactor (19) in order to sow the solution.

EXAMPLE OF APPLICATIONS

(40) Simple Implementation:

(41) Particularly adapted within the scope of an association with a water extraction unit from the digestion digestates, the first entering fluid (1) is nothing other than the retentate portion of a membrane filtration of the micro-ultra- or nano-filtration type. Before this filtration, the fluid is clarified by sifting with a mesh from 50 to 1,000 m, ideally 200 to 300 m. At the outlet of the module subject of the present invention, the fluid returns into the digester.

Alternative Example 1

(42) Implementation in Series: Alternative 1:

(43) Particularly adapted within the scope of filtration by reverse osmosis, the setting into place of a module subject of the present invention or of several modules in series on the recirculation loop of reverse osmosis gives the possibility of reducing the NH.sub.4.sup.+ concentration of the first fluid (1) to be filtered. Thus, the NH.sub.4.sup.+ forming a molecule which is difficult to retain for the OI BP-MP, the quality of the filtrate being improved and the blocking of the membranes thereby limited.

Exemplary Alternative 2

(44) Operating on a Non-Clarified or Further Clarified Fluid, a Mineral Organic Hybrid Fertilizer

(45) The MAP (Magnesium, Ammonium, Phosphate) composition may be added with value by addition of organic material on the one hand, completing the fertilizing action of the extracted mineral. If the second fluid (2) entering the device subject of the present invention is more or less clarified and/or stemming from a retentate of a more or less reducing filtration, the organic material will then form the central core of the mineral particles which will agglomerate around said core. The extracted MAP will then be an organic/mineral hybrid fertilizer.

Detailed Summary of the Invention

(46) Step 1:

(47) The phosphorus- and nitrogen-containing fluid (1) joins up with the channel (15A) the first reactor (19) via the injection point (9). This first fluid is stirred with a hydraulic transfer pump (15) or by the intrinsic pressure related to the global closed circuit.

(48) Step 2:

(49) A second fluid (2) containing a cation X.sup.2+ is injected into the first reactor (19) via the injection point (8) by means of a hydraulic transfer or dosage pump (16).

(50) Step 3:

(51) At the same time, when the reactor is filled, a gas (18) pour in CO.sub.2, air, is injected through the channel (18A) by means of an apparatus (30).

(52) Step 4:

(53) Following this stripping with air, an adjustment of the pH is possible by means of the apparatus (40B) which injects a basic solution (for example NaOH) via the conduit (41) allowing increase of the pH.

(54) Step 5:

(55) Once the reaction conditions are satisfied (pH and optimum mixing between fluid 1 and fluid 2), the chemical reaction may then occur in the reactor (19), potentially accelerated by means of a conventional stirring method.

(56) Step 6:

(57) Crystals of the small (3A) and intermediate (3B) solid inorganic product gradually becoming bigger fall under the effect of gravity to the bottom of the reactor (19) in the frustoconical portion.

(58) Step 7:

(59) Crystals of small (3A) and intermediate (3B) solid inorganic products and large and wet products (3C) are released at regular intervals by one or several valves (53) located at the bottom of the frustoconical portion of the first reactor (19) and directed towards a separator (5) comprising a first sieve (54) with large meshes in its upper portion and a second sieve (55) with small meshes in its lower portion. The most coarse particles (3C) crossing only the first sieve are discharged by the separator (5) via the discharge conduit (70) and forms the large dry precipitated solid inorganic product (3D) after drying. The small (3A) and intermediate (3B) solid inorganic products crossing the first sieve and the second sieve are re-injected via the initiation channel (17) into the channel for providing the first fluid (15A) in order to sow the initial solution in the first reactor (19). The fluid crossing the separator (5) is free of particles and is depleted in phosphorus. It forms the secondary remnant (6B).

(60) Step 8:

(61) The fluid remaining in the reactor (19) is brought via one of the separator valves (51) of the first reactor (19) towards the spiral reaction conduit (7A, 7B, 7C, 7D) of the second reactor (20). The precipitation reaction may then continue gradually as the fluid moves in the turns. The small (3A) and intermediate (3B) solid inorganic products which continue to become bigger and to precipitate in the turns (4), falling under the action of gravity into the lower portion of the spiral reactor (20) once a wet large solid inorganic product (3C) is formed and joins up with the particles stored (3C) in the frustoconical portion of the first reactor (9) via the channel (22).

(62) Step 9:

(63) The remainder of the fluid contained in the turns and presently depleted in phosphorus joins up with ascent the discharge conduit (14) of the main remnant (6C).

COMPARATIVE EXAMPLES

(64) TABLE-US-00001 Reactors (19) and Conventional column Reactor from WO (20) according to the Nature of the unit reactor 2012/134255 present invention Dimensions of the 8 meters high Reduced: unit diameter of 3 meters, transportable and requires special Plug & Play System premises and civil Height: 2 m to 3 m engineering Capacity per hour Minimum 80 m.sup.3/h (500 kg/d) May be modulated (from 1 m.sup.3/h) Separation method Decantation + vibrating centrifugal Decantation + vibrating sieve or centrifugation decanter sieve rotary drum sieve Sowing With fine struvite By small size grains turned With fine struvite particles or sand upside down in the rotary drum particles, calcium grains, calcium silicate silicate Decantation rate According to the nature 2 to 3 times greater as of the substrate compared with a conventional column reactor Dwelling time 10 to 15 days 4 to 6 mins in the reactor + for 15 to 20 days an unknown period in the drum Dimensions of the About 1 mm 1 mm to 1.5 mm 1 mm to 10 mm crystals Mixing method Vertical hydraulic flow Air injection Hydraulic flow by a vortex + air from the sifting

(65) Certain characteristics of the invention which are described as a separate embodiment, may also be provided in combination with a single embodiment. Conversely, certain characteristics of the invention which are described in an embodiment combined in a single embodiment, may also be provided separately in several separate embodiments. Although the invention has been described in connection with specific embodiments thereof, it is obvious that several alternatives, modifications and variations may be detected by one skilled in the art. Thus, we intend to encompass such alternatives, modifications and variations which fall within the scope of the claims hereafter.