阅读说明：本技术 一种铝热生产金属镁的制备方法 (Preparation method for producing magnesium metal through aluminothermic process ) 是由 孟浩杰 王鑫健 李峰 赵秀峰 白洋 李波 褚丙武 李长勇 于 2021-08-27 设计创作，主要内容包括：本发明特别涉及一种铝热生产金属镁的制备方法,属于金属镁制备技术领域,方法包括：将含镁矿石进行煅烧,获得煅白；将所述煅白和还原剂进行混合,后进行压制,获得团块；将所述团块进行真空还原,获得金属镁和还原渣料；其中,所述还原剂为含铝还原剂,所述煅白和所述含铝还原剂的质量比为4-6：1；所述还原渣料无需后续处理加工,可直接作为炼钢用精炼渣,将含镁矿石煅烧后与含铝还原剂混合还原,与皮江法相比,采用该工艺还原温度降低50-100℃,还原时间缩短50％以上,能耗降低,镁回收率85％以上,无废渣排放。(The invention particularly relates to a preparation method for producing metal magnesium by aluminothermy, which belongs to the technical field of metal magnesium preparation and comprises the following steps: calcining the magnesium-containing ore to obtain calcined dolomite; mixing the calcined dolomite and a reducing agent, and then pressing to obtain a briquette; carrying out vacuum reduction on the briquette to obtain metal magnesium and reduction slag charge; wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the calcined dolomite to the aluminum-containing reducing agent is 4-6: 1; the reduction slag can be directly used as refining slag for steelmaking without subsequent treatment and processing, magnesium-containing ore is calcined and then is mixed with an aluminum-containing reducing agent for reduction, compared with the Pidgeon process, the reduction temperature is reduced by 50-100 ℃, the reduction time is shortened by more than 50%, the energy consumption is reduced, the magnesium recovery rate is more than 85%, and no waste slag is discharged.)

1. A preparation method for producing metal magnesium by aluminothermy is characterized by comprising the following steps:

calcining the magnesium-containing ore to obtain calcined dolomite;

mixing the calcined dolomite and a reducing agent, and then pressing to obtain a briquette;

carrying out vacuum reduction on the briquette to obtain metal magnesium and reduction slag charge;

directly using the reduction slag charge to refining slag for steelmaking;

wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the calcined dolomite to the aluminum-containing reducing agent is 4-6: 1.

2. the preparation method for thermite production of magnesium metal according to claim 1, wherein the temperature of the vacuum reduction is 1100-1150 ℃, and the time of the vacuum reduction is 2-5 h.

3. The production method for aluminothermy producing metallic magnesium according to claim 1, wherein said aluminum-containing reducing agent is an aluminum powder supported by an aluminum-based printing plate.

4. The production method of thermite-produced magnesium metal according to claim 3, wherein the aluminum-based printing plate is a 1-series alloy in which the Al content is 99% or more by weight.

5. The method of claim 4, wherein the series 1 alloy comprises: 1060 alloy, 1050 alloy, or 1050A alloy.

6. The method for preparing magnesium metal by thermite production according to claim 3, wherein the particle size of the aluminum powder is 150 μm to 355 μm.

7. The production method for thermite production of metallic magnesium according to claim 1, wherein the degree of vacuum of the vacuum reduction is 5Pa to 10 Pa.

8. The preparation method for thermite production of metallic magnesium according to claim 1, wherein the temperature of the calcination is 1100 ℃ to 1200 ℃, and the time of the calcination is 1.5h to 3 h.

9. The method of claim 1, wherein the magnesium-containing ore comprises: dolomite.

Technical Field

The invention belongs to the technical field of metal magnesium preparation, and particularly relates to a preparation method for producing metal magnesium through thermite.

Background

The specific gravity of the metal magnesium is 1.74g/cm³2/3 for aluminum only, 2/5 for titanium, 1/4 for steel. The composite material has the advantages of high specific strength, high specific rigidity, good heat and electricity conducting performance, good electromagnetic shielding, damping, vibration damping, cutting processability, low processing cost, easiness in recycling and the like. As a unique strategic metal and a novel structural material in China, the material plays a greater role in the fields of traffic light weight, new energy materials, environmental protection industry, consumer electronics, ocean engineering, aerospace, military industry matching, military and civil fusion and the like. The rapid development of intercity rail transit for construction and operation in China also makes magnesium alloy castings, profiles and plates have great use.

The main methods for producing magnesium are the electrolysis method and the silicothermic method (Pidgeon method). The electrolytic method is to produce magnesium by electrolyzing magnesium chloride from brine, and the Pidgeon method is to utilize ferrosilicon (Si)>75%) to reduce the calcined dolomite to produce magnesium. Because of low investment cost and simple operation, the Pidgeon process becomes the main method in the industrial thermal magnesium smelting process at present, but the process has the problems of high energy consumption, low resource utilization efficiency and serious environmental pollution at present. In the traditional Pidgeon process of magnesium smelting, 11 tons of dolomite, 30 kilograms of fluorite and 1.05 tons of silicon iron are needed to be consumed for producing 1 ton of magnesium metal, and the energy consumption is 4 tons of standard coal; in addition, the emission of CO is required for every 1 ton of magnesium metal produced₂About 15 tons and about 6.5 tons of waste residues. The development of smelting magnesium by the Pidgeon process is restricted by high energy consumption and high emission.

In the prior art, the chinese patent application CN103184352A proposes a process for producing magnesium metal from dolomite, which comprises the steps of calcining, digesting, filtering, carbonizing, separating solid from liquid, pyrolyzing, drying basic magnesium carbonate, and the like, to prepare an intermediate basic magnesium carbonate, using cheap coke as a reducing agent and adding calcium fluoride as a catalyst, wherein the mixing amount of the coke is C: MgO ═ 1-4: 1, and performing vacuum carbothermic reduction reaction at 1300-1500 ℃ for 90-120min to obtain magnesium vapor, wherein although the process reduces the discharge of waste residues and the cost of raw materials, a large amount of carbon monoxide and carbon dioxide gas is generated, and in addition, the process method has long steps and still discharges the waste residues. The Chinese patent application CN102808089A proposes a method for preparing magnesium metal and magnesium aluminate spinel by using magnesium oxide as raw materials, which adopts magnesium oxide, aluminum powder and aluminum-magnesium alloy powder as raw materials, and carries out reduction reaction at 1100-1400 ℃ for 0.5-8 hours under the vacuum condition after mixed and briquetted, so as to produce gaseous magnesium metal and solid reduction slag, wherein the chemical reaction formula is as follows: 4MgO +2Al ═ 3Mg + MgAl₂O₄Adding magnesium oxide powder into the solid reduction slag charge, wherein the mass ratio of the solid reduction slag charge to the magnesium oxide powder is (1-100): 1, mixing and briquetting, and calcining to obtain a magnesium aluminate spinel finished product or preparing a finished product of the fused magnesium aluminate spinel. Although the reducing slag is utilized, a plurality of processes of material taking, crushing, material feeding, agglomeration, calcination and the like are required, the processes are complex, a large amount of energy consumption is consumed in high-temperature sintering, and in addition, the cost of magnesium smelting is further increased by adopting aluminum powder, aluminum alloy powder and other raw materials with higher price.

Disclosure of Invention

The application aims to provide a preparation method for producing metal magnesium by aluminothermic process, so as to solve the problems of energy, resources and environment in the magnesium industry.

The embodiment of the invention provides a preparation method for producing metal magnesium by thermite, which comprises the following steps:

calcining the magnesium-containing ore to obtain calcined dolomite;

mixing the calcined dolomite and a reducing agent, and then pressing to obtain a briquette;

carrying out vacuum reduction on the briquette to obtain metal magnesium and reduction slag charge;

directly using the reduction slag charge to refining slag for steelmaking;

wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the calcined dolomite to the aluminum-containing reducing agent is 4-6: 1.

optionally, the temperature of the vacuum reduction is 1100-1150 ℃, and the time of the vacuum reduction is 2-5 h.

Optionally, the aluminum-containing reducing agent is aluminum powder supported by an aluminum-based printing plate.

Optionally, the aluminum-based printing plate is a 1-series alloy, wherein, by weight, the Al content is not less than 99%.

Optionally, the 1-series alloy includes: 1060 alloy, 1050 alloy, or 1050A alloy.

Optionally, the particle size of the aluminum powder is 150 μm to 355 μm.

Optionally, the vacuum degree of the vacuum reduction is 5Pa-10 Pa.

Optionally, the magnesium-containing ore comprises: dolomite.

Optionally, the calcining temperature is 1100-1200 ℃, and the calcining time is 1.5-3 h.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the preparation method for producing the metal magnesium by the aluminothermic process, provided by the embodiment of the invention, comprises the following steps: calcining the magnesium-containing ore to obtain calcined dolomite; mixing the calcined dolomite and a reducing agent, and then pressing to obtain a briquette; carrying out vacuum reduction on the briquette to obtain metal magnesium and reduction slag charge; wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the calcined dolomite to the aluminum-containing reducing agent is 4-6: 1, the reduction slag does not need subsequent treatment and processing and can be directly used as refining slag for steelmaking; the magnesium-containing ore is calcined and then mixed with an aluminum-containing reducing agent for reduction, compared with a Pidgeon process, the reduction temperature is reduced by 50-100 ℃, the reduction time is shortened by more than 50%, the energy consumption is reduced, the recovery rate of magnesium is more than 85%, and no waste residue is discharged.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a flow chart provided by an embodiment of the present invention;

fig. 2 is a block diagram provided by an embodiment of the invention.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to an exemplary embodiment of the present invention, there is provided a method for preparing magnesium metal by thermite production, referring to fig. 1, the method including:

s1, calcining magnesium-containing ore to obtain calcined dolomite;

specifically, the magnesium-containing ore is dolomite, and the dolomite is calcined at 1100-1200 ℃ for 1.5-3h to obtain calcined dolomite;

MgCO in dolomite₃The decomposition temperature is 720-800 ℃ and CaCO is required₃The decomposition temperature needs to be 900-930 ℃. In actual production, the calcination temperature is generally set to 1100 ℃ to 1250 ℃, which can be determined by experiment. If the calcination temperature is too low and the calcination time is too short, the decomposition is not completely carried out; when the temperature is too high, the calcination time is too long, and MgO grains grow and gradually lose activity.

S2, mixing the calcined dolomite and a reducing agent, and then pressing to obtain a briquette; wherein the reducing agent is an aluminum-containing reducing agent, and the mass ratio of the calcined dolomite to the aluminum-containing reducing agent is 4-6: 1.

specifically, an aluminum-containing reducing agent is an aluminum-based printing plate, the aluminum-based printing plate is cut and crushed, then, the crushed small particles are sent into a ball mill for grinding by adopting a dry ball milling method, aluminum powder with different particle sizes is obtained after powder classification, the aluminum powder with the particle size of 150-355 microns is selected as the reducing agent, then, dolomite calcined dolomite is ground and mixed with the aluminum powder, and then, the mixture is pressed into briquettes, wherein the mass ratio of the dolomite calcined dolomite to the aluminum powder is (4-6): 1. in actual operation, the aluminum-based printing plate is 1 series 1060, 1050 and 1050A alloy, and the Al content is more than or equal to 99 percent.

The particle size of the aluminum powder is controlled to be 150-355 mu m, the excessive particle size of the aluminum powder can cause insufficient contact with dolomite calcined dolomite, and the excessive particle size is not suitable for economy.

Controlling the mass ratio of calcined dolomite to aluminum powder to be (4-6): the reason for 1 is to ensure that the reducing slag meets the components of the refining slag for steelmaking, the excessive adverse effect of the mass ratio is to cause the content of magnesium oxide and calcium oxide to exceed the standard, and the excessive adverse effect is to cause the poor economy and the excessive content of aluminum oxide.

S3, carrying out vacuum reduction on the briquette to obtain metal magnesium and reduction slag charge;

specifically, the block mass is put into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1100-1150 ℃, and the reduction time is 2-5 h; obtaining the metal magnesium and the reduction slag charge.

The solid reduction slag does not need subsequent treatment and processing, can be directly used as refining slag for steelmaking, and realizes the one-step production of metal magnesium and the refining slag for steelmaking.

In the above process, there may be two chemical reaction formulas, specifically as follows:

3CaO+3MgO+2Al＝3Mg+3CaO·Al₂O₃

12CaO+21MgO+14Al＝21Mg+12CaO·7Al₂O₃

the process is suitable for dolomite with various components, because the Pidgeon magnesium smelting is a solid-solid reaction, the reaction speed is slow, the addition of auxiliaries such as calcium fluoride and the like can increase the reaction energy on the surface of an oxide and promote the reaction to be accelerated, and the application does not need auxiliary materials such as magnesite and other auxiliaries; compared with Pidgeon process, the process has the advantages of reducing the reduction temperature by 50-100 ℃, shortening the reduction time by more than 50%, reducing the energy consumption, recovering the magnesium by more than 85% and discharging no waste residue.

The preparation method of the magnesium metal by thermite production of the present application will be described in detail below with reference to examples, comparative examples and experimental data.

Example 1

The process flow chart of the invention is shown in figure 2, and the process for producing the magnesium metal by-product refining slag for steelmaking by aluminothermy adopts dolomite as a raw material and aluminum powder as a reducing agent and comprises the following steps:

(1) calcining dolomite at 1100 deg.C for 1.5h to obtain calcined dolomite. The dolomite contains 21.29 percent of MgO, 28.57 percent of CaO and 3.51 percent of SiO₂，0.76％Al₂O₃，0.38％Fe₂O₃，45.15％CO₂Wherein the molar ratio of CaO to MgO is 0.959;

(2) cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 150 mu m;

(3) the dolomite calcined dolomite is ground and then mixed with aluminum powder, and then is pressed into briquettes under the pressure of 100MPa, wherein the mass ratio of the dolomite calcined dolomite to the aluminum powder is 4: 1;

(4) and (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1100 ℃, the reduction time is 3h, and the vacuum degree is 5-10 Pa.

Example 2

The process flow chart of the invention is shown in figure 2, and the process for producing the magnesium metal by-product refining slag for steelmaking by aluminothermy adopts dolomite as a raw material and aluminum powder as a reducing agent and comprises the following steps:

(1) calcining dolomite at 1100 deg.C for 3 hr to obtain calcined dolomite. Adopts dolomite containing 20.76 percent of MgO, 30.29 percent of CaO and 0.96 percent of SiO₂，0.35％Al₂O₃，0.56％Fe₂O₃，46.24％CO₂Wherein the molar ratio of CaO to MgO is 1.042;

(2) cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 180 mu m;

(3) the dolomite calcined dolomite is ground and mixed with aluminum powder, and then is pressed into briquettes under the pressure of 122MPa, wherein the mass ratio of the dolomite calcined dolomite to the aluminum powder is 5.2: 1;

(4) and (3) putting the agglomerates into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1100 ℃, the reduction time is 5h, and the vacuum degree is 5-10 Pa.

Example 3

The process flow chart of the invention is shown in figure 2, and the process for producing the magnesium metal by-product refining slag for steelmaking by aluminothermy adopts dolomite as a raw material and aluminum powder as a reducing agent and comprises the following steps:

(1) calcining dolomite at 1200 deg.C for 1.5h to obtain calcined dolomite. Adopts dolomite containing 20.69 percent of MgO, 31.42 percent of CaO and 0.62 percent of SiO₂，0.054％Al₂O₃，0.036％Fe₂O₃，46.14％CO₂Wherein the mass ratio of CaO to MgO is 1.085;

(2) cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 150 mu m;

(3) the dolomite calcined dolomite is ground and then mixed with aluminum powder, and then is pressed into briquettes under the pressure of 150MPa, wherein the mass ratio of the dolomite calcined dolomite to the aluminum powder is 5.5: 1;

(4) and (3) putting the block mass into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1150 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10 Pa.

Example 4

The process flow chart of the invention is shown in figure 2, and the process for producing the magnesium metal by-product refining slag for steelmaking by aluminothermy adopts dolomite as a raw material and aluminum powder as a reducing agent and comprises the following steps:

(1) calcining dolomite at 1200 deg.C for 3 hr to obtain calcined dolomite. Adopts dolomite containing 19.67 percent of MgO, 31.89 percent of CaO and 1.51 percent of SiO₂，0.31％Al₂O₃，0.15％Fe₂O₃，46.23％CO₂Wherein the mass ratio of CaO to MgO is 1.158;

(2) cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 355 mu m;

(3) the dolomite calcined dolomite is ground and then mixed with aluminum powder, and then is pressed into briquettes under the pressure of 190MPa, wherein the mass ratio of the dolomite calcined dolomite to the aluminum powder is 6: 1;

(4) and (3) putting the block mass into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1150 ℃, the reduction time is 3h, and the vacuum degree is 5-10 Pa.

Comparative example 1

Magnesite is used as a raw material, aluminum powder is used as a reducing agent, and the method comprises the following steps:

(1) the magnesite is calcined at 850 ℃ for 1.5 h. Magnesite containing 47.30% of MgO, 0.62% of CaO and 0.42% of SiO₂，0.08％Al₂O₃，0.36％Fe₂O₃，51.02％CO₂；

(2) Cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 150 mu m;

(3) grinding calcined magnesite, mixing the ground calcined magnesite with aluminum powder, and pressing the mixture into briquettes under the pressure of 190MPa, wherein the mass ratio of the calcined magnesite to the aluminum powder is 3: 1;

(4) and (3) putting the block mass into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1150 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10 Pa.

Comparative example 2

The method is characterized in that dolomite and magnesite are used as raw materials, aluminum powder is used as a reducing agent, and the method comprises the following steps:

(1) calcining dolomite at 1200 deg.C for 1.5h to obtain calcined dolomite. Adopts dolomite containing 20.69 percent of MgO, 31.42 percent of CaO and 0.62 percent of SiO₂，0.054％Al₂O₃，0.036％Fe₂O₃，46.14％CO₂Wherein the mass ratio of CaO to MgO is 1.085;

(2) the magnesite is calcined at 850 ℃ for 1.5 h. Magnesite containing 47.30% of MgO, 0.62% of CaO and 0.42% of SiO₂，0.08％Al₂O₃，0.36％Fe₂O₃，51.02％CO₂；

(3) Cutting and crushing the aluminum-based printing plate, then, sending the crushed small particles into a ball mill for grinding by adopting a dry ball milling method, obtaining aluminum powder with different particle sizes after powder classification, and selecting the aluminum powder with the particle size of 150 mu m;

(4) the dolomite calcined dolomite and the calcined magnesite are ground and mixed with aluminum powder, and then are pressed into briquettes under the pressure of 190MPa, wherein the mass ratio of the dolomite calcined dolomite to the calcined magnesite to the aluminum powder is 1: 2: 1;

(5) and (3) putting the block mass into a reduction furnace for vacuum reduction to obtain metal magnesium and solid reduction slag charge, wherein the reduction temperature is 1150 ℃, the reduction time is 2 hours, and the vacuum degree is 5-10 Pa.

Examples of the experiments

The solid reduced slag produced in examples 1 to 4 and comparative examples 1 to 2 were subjected to compositional analysis, and the results are shown in the following table:

	MgO％	Al2O3％	SiO2％	CaO％	Fe2O3％
						example 1	0.98	46.33	5.64	45.02	1.98
Example 2	1.29	45.90	2.92	49.16	1.78
						Example 3	0.34	48.01	1.63	49.87	0.13
Example 4	0.74	36.06	2.57	59.21	0.38
						Comparative example 1	30.7	64.48	1.42	2.64	0.67
Comparative example 2	6.15	72.20	1.02	20.07	0.40

Compared with the prior aluminothermic process, the reduced slag prepared by the method provided by the embodiment of the application meets the component requirements of the refining slag for steelmaking, can be directly used as the refining slag for steelmaking without subsequent treatment, adopts dolomite as a raw material, can provide proper magnesium oxide and calcium oxide, meets the requirements of producing metal magnesium and refining slag products for steelmaking by a one-step method, and is simple in material preparation.

One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:

(1) the method provided by the embodiment of the invention solves the energy, resource and environmental problems in the magnesium industry, and the process has the advantages that on one hand, the reducing agent is produced by using the aluminum-based printing waste plate, on the other hand, the by-product produced by producing the metal magnesium can be directly used as refining slag for steelmaking, the subsequent treatment and processing are not needed, the production of no waste slag in the magnesium smelting production process can be realized, the environment is protected, the energy is saved, and the clean production is realized; meanwhile, the method is also a comprehensive utilization of the aluminum-based printing waste board. (ii) a

(2) Compared with the Pidgeon process, the reduction temperature of the process is reduced by 50-100 ℃, the reduction time is shortened by more than 50%, the energy consumption is reduced, the magnesium recovery rate is more than 85%, and no waste residue is discharged;

(3) compared with the prior aluminothermic method, the method provided by the embodiment of the invention has the advantages that the reducing slag generated in the process of reducing the magnesium can be directly used as refining slag for steelmaking without subsequent treatment; the process adopts dolomite as a raw material, can provide proper magnesium oxide and calcium oxide, meets the requirements of producing metal magnesium and refining slag products for steelmaking by a one-step method, and has simple ingredients; the aluminum powder adopted by the process is the regenerated aluminum powder of the aluminum-based printing plate, and the resources are comprehensively utilized.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.