Abstract:
An apparatus for recovering valuable elements is provided herein. In some embodiments, the apparatus having a conveyor; a container configured to be moved on the conveyor, wherein the container has an open surface; a paper package which contains a mixture containing valuable elements, the paper package being configured to be disposed in the container and to be combusted; a cover that covers the open surface of the container, the cover having an opening for discharging valuable elements vaporized from the mixture; a microwave oven through which the container having the cover and the paper package passes, wherein the microwave oven having a microwave generator and a discharging opening for discharging the valuable elements vaporized from the mixture; and a condenser coupled to the discharge opening, wherein the condenser recovers the valuable elements vaporized from the mixture.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0104582 filed in the Korean Intellectual Property Office on Oct. 30, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to an apparatus for recovering valuable elements. More particularly, the present invention relates to an apparatus for recovering valuable elements such as zinc, iron, and so on from waste discharged from an iron making plant such as iron dust, sludge, slag and so on. 
     (b) Description of the Related Art 
     A large amount of waste such as dust, sludge, slag, and scales are generated in an iron making plant in which molten iron is manufactured by reducing iron ore. The waste contains a large amount of metals such as iron and zinc and valuable elements such as phosphor. Research and development have been vigorously conducted for recycling the metals among the elements and using them as a resource for manufacturing molten iron. 
     Most of the waste such as dust, sludge, slag, scales, and so on is easily e scattered since they exist as powders. Therefore, it is necessary to heat the waste without scattering them in order to recover the metals contained in the waste by heating and reducing the waste. For this, a method for heating them by using a microwave has been used. The waste is not scattered since it can be heated in a stationary state by using the above method. 
     SUMMARY OF THE INVENTION 
     An apparatus for recovering valuable elements containing metals such as zinc, iron and so on by using microwave is provided. 
     An exemplary embodiment of the present invention provides an apparatus for recovering valuable elements, including: i) a conveyor; ii) a microwave oven that is located on the conveyor and that radiates microwaves; iii) a container of which a surface is opened; and iv) a cover that covers the surface of the container. The container passes through the microwave oven while being moved on the conveyor, and is configured to contain a mixture containing carbonaceous materials and waste discharged from an iron making plant therein. The microwave oven includes a casing that blocks the microwaves from the outside. The casing includes i) a lower portion that is opened to be opposed to the conveyor, and ii) an upper portion on which a discharging opening for discharging metal vaporized from the mixture is formed. The upper portion opposes the lower portion. The valuable elements contained in the mixture are configured to be recovered by heating the mixture by the microwaves. 
     The width of the container may be less than the height of the container. A ratio of the width of the container to the height of the container may be in a range of 5 to 20. 
     The apparatus for recovering valuable elements according to an embodiment of the present invention may further include a packaging device that neighbors the conveyor and supplies the mixture to the container after packaging the mixture. The container, before passing by the microwave oven, may contain the mixture packaged in a package made of paper. The apparatus for recovering valuable elements according to an embodiment of the present invention may further include a mixture supplying device that supplies the carbonaceous materials and the waste discharged from the iron making plant to the packing device after mixing the carbonaceous materials and the waste discharged from the iron making plant. 
     The apparatus for recovering valuable elements according to an embodiment of the present invention may further include a plurality of fans that are installed at a side portion of the casing to be spaced apart from each other along a transferring direction of the conveyor. The conveyor may include i) a pair of driving motors that are spaced apart from each other, and ii) a conveyor belt that is combined with the pair of the driving motors and that is configured to move the container. A plurality of depressions may be formed on the conveyor belt side by side along a transferring direction of the conveyor belt, and into which the container is inserted to be fixed. The apparatus for recovering valuable elements according to an embodiment of the present invention may further include a magnetic separator that neighbors the conveyor and that is configured to recover valuable elements contained in the container that passed through the microwave oven. 
     A recovery ratio of the metals such as zinc, iron, and so on can therefore be raised. The iron can be easily separated from the slag by using microwaves when zinc, iron, and so on are recovered. 
     In some embodiments, an apparatus for recovering valuable elements comprises a conveyor; a container configured to be moved on the conveyor, wherein the container has an open surface; a paper package which contains a mixture containing valuable elements, the paper package being configured to be disposed in the container and to be combusted; a cover that covers the open surface of the container, the cover having an opening for discharging valuable elements vaporized from the mixture; a microwave oven through which the container having the cover and paper package passes, wherein the microwave oven comprises a microwave generator and a discharging opening for discharging the valuable elements vaporized from the mixture; and a condenser coupled to the discharge opening, wherein the condenser recovers the valuable elements vaporized from the mixture; wherein the width of the container is greater than the height of the container, and wherein a ratio of the width of the container to the height of the container is in a range of 5 to 20. 
     In some embodiments, the apparatus further comprises a packaging device that neighbors the conveyor and is configured to package the mixture in the paper package and to supply the paper package containing the mixture to the container. 
     In some embodiments, the apparatus further comprises a mixture supplying device configured to supply the mixture to a packing device. 
     In some embodiments, the microwave oven further comprises a plurality of fans spaced apart from each other along a transferring direction of the conveyor. 
     In some embodiments, the conveyor comprises a pair of driving motors that are spaced apart from each other; and a conveyor belt driven by the pair of the driving motors and is configured to move the container, wherein a plurality of depressions are formed on the conveyor belt side by side along a transferring direction of the conveyor belt, wherein the container is configured to be inserted into one of the plurality of depressions. 
     In some embodiments, the apparatus further comprises a magnetic separator that neighbors the conveyor, wherein the magnetic separator is configured to recover valuable elements contained in the container after the container passes through the microwave oven. 
     In some embodiments, the valuable elements are selected from the group consisting of zinc, iron, and phosphor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an apparatus for recovering valuable elements according to a first embodiment of the present invention. 
         FIG. 2  is a schematic partial perspective view of the apparatus for recovering valuable elements of  FIG. 1 . 
         FIG. 3  is a schematic exploded view of a container and a cover of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The embodiments of the present invention described with reference to perspective views and sectional views substantially represent the ideal embodiments of the present invention. Consequently, illustrations are expected to be variously modified, that is, manufacturing methods and/or specifications are expected to be modified. Thus, the embodiments are not limited to a particular form of illustrated regions and, for example, modifications of forms according to manufacturing are also included. For example, a region illustrated or described to be flat may generally be rough or have rough and nonlinear characteristics. Also, a portion illustrated to have a pointed angle may be rounded. Thus, regions illustrated in the drawings are merely rough and broad, and their forms are not meant to be precisely illustrated or meant to narrow the scope of the present invention. 
     The technical terms used herein are to simply mention a particular embodiment and are not meant to limit the present invention. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present invention, it is to be understood that the terms such as “including”, “having,” etc., are intended to indicate the existence of the features, numbers, operations, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, operations, actions, components, parts, or combinations thereof may exist or may be added. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     The terms “first”, “second”, and “third” are used to explain various parts, components, regions, layers and/or sections, but it should be understood that they are not limited thereto. These terms are used only to discriminate one portion, component, region, layer, or section from another portion, component, region, layer, or section. Thus, a first portion, component, region, layer, or section may be referred to as a second portion, component, region, layer, or section without departing from the scope of the present invention. 
     Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those with ordinary knowledge in the field of art to which the present invention belongs. Such terms as those defined in a generally used dictionary are to be interpreted to have the meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted to have idealized or excessively formal meanings unless clearly defined in the present application. 
     Terms indicating relative spaces such as “below”, “above”, and the like may be used to easily describe the relationships between elements illustrated in drawings. Such terms may be intended to include different meanings or operations of a device in use along with meanings intended by the drawings. For example, if a device on a drawing is reversed, it would be described that one element described to be “under” or “below” the other element may be described to be “on” or “above” the other element. Thus, terms illustrative of “under” or “below” may include all the downward and upward directions. A device may be rotated by 90° or other angles, and terms representing a relative space may be interpreted accordingly. 
     The term “carbonaceous material” used below means all materials containing carbon. Therefore, the carbonaceous material is interpreted as carbon, black carbon, waste carbon, fine coal, coke, or coal. The term “valuable elements” used below means all elements disclosed in the periodic table and compounds thereof. Therefore, the valuable elements are interpreted to include all elements capable of being recovered and recycled, and compounds thereof. 
     “Waste of an iron making plant” used below includes the waste discharged from the iron making plant. The term “waste” means all by-products discharged from the iron making plant such as dust, wasted carbon, wasted cokes, slag, and so on. Furthermore, the waste of an iron making plant is interpreted to include all waste that is expected to be discharged from the iron making plant among the waste. 
       FIG. 1  schematically shows the apparatus for recovering valuable elements  100  according to an embodiment of the present invention. The apparatus for recovering valuable elements  100  of  FIG. 1  is merely to illustrate the present invention, and the present invention is not limited thereto. Therefore, the apparatus for recovering valuable elements  100  of  FIG. 1  can have other forms. In addition, since a detailed operating structure of the apparatus for recovering valuable elements  100  of  FIG. 1  can be understood by those skilled in the art in a technical field of the present invention, detailed description thereof is omitted. 
     As shown in  FIG. 1 , the apparatus for recovering valuable elements  100  includes a container  10 , a cover  20 , a microwave oven  30 , and a conveyor  40 . The apparatus for recovering valuable elements  100  further includes a condenser  50 , a packaging device  60 , a mixture supplying device  70 , and a magnetic separator  80 . The devices described above may be partially omitted. In addition, the apparatus for recovering valuable elements  100  may further include other devices if necessary. A process for recovering valuable elements by using the apparatus for recovering valuable elements  100  will be explained below along a flow direction of the conveyor  40  indicated by an arrow, that is, the −x axis direction. 
     Firstly, the mixture supplying device  70  stirs and mixes the carbonaceous material and the waste of the iron making plant. Slag can be additionally mixed with the carbonaceous material and the iron dust. The mixture supplying device  70  includes a mixing bin  701  and a mixer  703 . The carbonaceous material and the waste discharged from the iron making plant charged into the mixing bin  701  are uniformly mixed with each other by the rotating mixer  703 . Since a detailed specific structure of the mixture supplying device  70  can be easily understood by those skilled in the art in a technical field of the present invention, a detailed description thereof is omitted. 
     Materials containing carbon that are recovered from the iron making plant such as waste carbon, fine coal, coke, and coal, may be used as the carbonaceous material. Meanwhile, the iron dust is recovered by collecting fine particles generated from the iron making plant, and an exemplary composition thereof is described in Table 1 below. In addition, an exemplary composition of the iron making slag generated from the iron making plant is described in Table 2 below. Furthermore, various wastes containing valuable elements such as sludge and mill scales generated from the iron making plant can be used as a resource. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Elements 
               
             
          
           
               
                   
                 Al 
                 Ca 
                 Fe 
                 K 
                 Mg 
                 Na 
                 Pb 
                 Cr 
                 S 
                 Zn 
                 Si 
               
               
                   
                   
               
             
          
           
               
                 content 
                 0.2026 
                 2.738 
                 25.17 
                 2.422 
                 1.750 
                 1.875 
                 1.096 
                 0.2261 
                 0.6514 
                 20.17 
                 2.021 
               
               
                 (wt %) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 Elements 
               
             
          
           
               
                   
                 T · Fe 
                 FeO 
                 Fe 2 O 3   
                 SiO 2   
                 CaO 
                 MnO 
                 P 2 O 5   
                 Al 2 O 3   
                 MgO 
                 TiO 2   
               
               
                   
                   
               
             
          
           
               
                 content 
                 15.705 
                 17.180 
                 3.346 
                 29.6 
                 28.94 
                 9.186 
                 3.4 
                 3.28 
                 3.13 
                 1.18 
               
               
                 (wt %) 
               
               
                   
               
             
          
         
       
     
     As described in Tables 1 and 2, the iron dust and slag contain the valuable elements such as iron, and the iron exists to be oxidized. Therefore, the carbonaceous materials function as a reducing agent of the oxidized iron by being mixed with the iron dust. 
     As shown in  FIG. 1 , the mixture of the carbonaceous material and the waste discharged from the iron making plant is discharged toward a lower direction, that is, along a −z-axis direction by a valve  705  that regularly operates to be opened and closed. That is, the mixture of the carbonaceous material and the waste discharged from the iron making plant is supplied to the packaging device  60  that neighbors the mixture supplying device  70 . 
     The packaging device  60  includes a conveyor  601  for transferring the package P and a packaging sealing device  603 . The conveyor  601  for transferring the package supplies the mixture supplied from an upper portion thereof to the package P in order while transferring the package P along a direction indicated by an arrow. For example, the package P is made of paper that can be easily combusted. Therefore, the package P for packaging the mixture before passing the microwave oven  30  may be combusted to be eliminated by the microwaves radiated by the microwave oven  30  in a following process. For example, a cement package may be used as the package P. The mixture can be easily charged into the package P since an upper portion of the package P is opened. For example, the dimensions of the package can be 600 mm×400 mm×80 mm, and may be changed depending on an operating state. The package P in which the mixture is contained is sealed to be packaged by a package sealing device  603  while being transferred along the −x-axis direction. Therefore, the mixture does not leak outside of the package P. 
     A large amount of dust is generated from the mixture when the mixture is charged and heated without using the package P. The generated dust is attached to inner and outer sides of the container  10  and the cover  20 . In addition, the dust can be scattered outside to be attached to inside of the microwave oven  30 . To make matters worse, the microwave heats the dust attached to the inner and outer sides of the container  10  and the cover  20  and the inner surface of the microwave oven  30  while passing the container  10  through the microwave oven  30 . Therefore, the heating effect of the mixture is deteriorated. On the contrary, according to an embodiment of the present invention, the dust can be suppressed from being generated and the heating effect of the microwave on the mixture can be largely increased by using the package P. Since the microwave penetrates the package P made of a paper, the container  10 , and the cover  20 , the mixture is effectively heated. 
     As shown in  FIG. 1 , the package P in which the mixture is packaged falls on the conveyor  40  by way of the packaging device  60  that neighbors the conveyor  40 . Therefore, the package P is supplied to the container  10  that is transferred by the conveyor  40  along the −x-axis direction. The container  10  transmits the microwaves and insulates heat. Since the container  10  has sufficient space to contain the package P, the package P is stably contained in the container  10 . Particularly, the package P is laid to be contained in the container  10  in order to stably contain the package P and enhance the heating effect of the microwave oven  30 . 
     Meanwhile, the conveyor  40  includes a pair of driving motors  401  and a conveyor belt  403 . The pair of driving motors  401  are located to be spaced apart from each other. The conveyor belt  403  is driven by the pair of driving motors  401 . The conveyor belt  403  transfers the container  10 . 
     As shown in  FIG. 1 , an upper portion of the container  10  is covered with a cover  20  in order to suitably seal an inner portion of the container  10  since an upper portion of the container  10  in which the package P is contained is opened. That is, after a sealing device  91  grasps the cover  20 , it covers the container  10  with the cover  20 . Therefore, the inner portion of the container  10  in which the mixture containing the carbonaceous material and the iron dust is contained can be suitably sealed. Since the container  10  is covered with the cover  20 , the container  10  is insulated for heat, and thereby the inner temperature can be highly maintained. Therefore, the metals can be easily recovered from the mixture by highly maintaining the temperature of the mixture that is heated by the microwave oven  30  and then a reducing reaction is promoted by the carbonaceous materials. 
     More specifically, since radiation heat generated from the mixture in a heat insulation state cannot be discharged outside, the temperature of the mixture is abruptly increased by the radiation heat. That is, the mixture can be quickly heated without using a preheating process. As a result, for example, the mixture is quickly heated to a temperature in a range of 1500° C. to 1700° C. at one time irrespective of a short heating time. Therefore, valuable elements can be easily separated from the mixture by melting them while environmentally hazardous elements can be stably fixed in the slag. 
     As shown in  FIG. 1 , the container  10  transferred on the conveyor  40  moves toward the microwave oven  30 . The microwave oven  30  includes a casing  305  that separates an inner portion thereof from an outer portion thereof. The inner surface of the casing  305  can be made of a steel plate coated with an alumina fiber in order to block the microwaves radiated toward an inner side thereof from the outside thereof. An inlet door  307  and an outlet door  309  are installed at the front and rear sides of the casing  305 , respectively. The inlet door  307  and an outlet door  309  are automatically opened and closed. Therefore, when the container  10  approaches the inlet door  307 , the container  10  enters into the casing  305  while the inlet door  307  is opened. In addition, the container  10  to which microwaves are no longer radiated is discharged outside as the outlet door  309  is opened. Therefore, the valuable elements are contained in the mixture that is contained in the container  10  as the container  10  passes through the microwave oven  30 . A double door (not shown) can be installed at an inlet port and an outlet port of the microwave oven  30  in order to prevent microwaves from leaking outside. 
     The microwave oven  30  includes a plurality of microwave generators  301 . The plurality of microwave generators  301  are arranged side by side along the x-axis, that is, a transferring direction of the conveyor belt  403 . Therefore, the plurality of microwave generators  301  continuously heat the mixture contained in the container  10 . Accordingly, the heating effect of the mixture can be maximized. A low output microwave resonator is used as the microwave generator  301 , and the entire microwave output can be controlled by using a plurality of low output microwave resonators. For reference, specimens in a ceramic sintered furnace with an inner effective volume of 2 m 3  can be heated to 1600° C. or more by using an inexpensive microwave resonator with an output of 90 kW and a frequency of 2.45 GHz. In addition, the mixture can be uniformly heated by using a plurality of microwave generators  301  since air in the microwave oven  30  is circulated by a fan  302  installed at a side surface of the microwave oven  30 . A plurality of fans  302  are installed to be spaced apart from each other side by side at the side surface of the casing  305  along a transferring direction of the conveyor belt  403 , that is, along the x-axis. Therefore, the mixture contained in the container  10 , which moves along a transferring direction of the conveyor belt  403 , is uniformly heated by circulating the air in the casing  305 . 
     As shown in  FIG. 1 , the casing  305  includes a lower portion  3051  and an upper portion  3053 . The lower portion  3051  is opened to be opposed to the conveyor belt  403 . Therefore, the container  10  is heated by the microwaves in the casing  305  while being continuously transferred on the conveyor belt  403  without interference from the casing  305 . 
     The upper portion  3053  opposes the lower portion  3051 . A discharging port  303  is formed at the upper portion  3053 . The metals vaporized from the mixture by the microwaves can be discharged outside through the discharging port  303 . Meanwhile, the discharging port  303  is connected to a condenser  50 . The metals discharged outside through the discharging port  303  are condensed to be recovered by cooling water flowing through the condenser  50 . Therefore, the metals discharged from the mixture, for example zinc whose melting point is lower than that of iron, can be recovered by the condenser  50 . When dust of an iron making plant where an electric furnace is installed is recovered and used, a portion of galvanized steel recovered from a scrapped vehicle among iron scraps used in the electric furnace is high. Therefore, iron dust can include a large amount of zinc. Since a detailed structure of the condenser  50  can be easily understood by those skilled in the art in a technical field of the present invention, a detailed description thereof is omitted. 
     Meanwhile, an opening device  93  grasps the cover  20  and then separates the cover from the container  10  that has passed through the microwave oven  30 . Only a mixture from which the package P is removed exists in the container  10  from which the cover  20  is removed. That is, the package P is combusted to be eliminated by the microwaves generated by the microwave generator  301  while the container  10  passes through the microwave oven  30 . Particularly, since the mixture is heated in the container while being maintained to be sealed at a high temperature therein, iron is united as it is melted. Then, a slag surrounds the melted iron. Therefore, since the iron is naturally separated from the slag, the iron can be easily recovered by being separated from the slag. 
     That is, as shown in  FIG. 1 , the magnetic separator  80  is located to neighbor the conveyor  40 . The magnetic separator  80  recovers the valuable elements contained in the container  10 . That is, the magnetic separator  80  is inserted into the container  10  along a direction indicated by the arrows and then pressure is applied toward a lower side of the container  10 . Then, the metal is separated from the slag, thereby being recovered by attaching it to the magnetic separator  80 . Since a detailed structure of the magnetic separator  80  can be understood by those skilled in the art in a technical field of the present invention, a detailed description thereof is omitted. In addition to the magnetic separator, various separating devices such as a cyclone can be used in order to recover the valuable elements. 
       FIG. 2  is a partial schematic perspective view of the apparatus  100  for recovering valuable elements of  FIG. 1 .  FIG. 2  partially enlarges the conveyor belt  403  of  FIG. 1 . 
     As shown in  FIG. 2 , a plurality of depressions  4031  are formed on the conveyor belt  403 . The plurality of depressions  4031  are formed side by side along a transferring direction of the conveyor belt  403 , that is, an x-axis direction. Therefore, as shown indicated by an arrow in  FIG. 2 , the container  10  is inserted to be fixed in the depression  4031 , thereby being stably located on the conveyor belt  403 . Therefore, there is no possibility for the container  10  to leave the conveyor belt  403  while being transferred by the conveyor belt  403 . 
       FIG. 3  schematically shows an exploded view of the container  10  and the cover  20  of  FIG. 1 . 
     As shown in  FIG. 3 , the package P in which the mixture is contained is covered with the cover  20  after it is contained in the container  10 . The package P is laid down in order to stably contain the package P in the container  10 . Therefore, the container  10  has a shape of which a width W thereof is greater than a height thereof. More specifically, a ratio of the width W of the container  10  to the height h of the container  10  can be in a range from 5 to 20. If the ratio of the height h of the container  10  to the width W thereof is too great, the package P cannot be stably contained since the height h of the container  10  is relatively high. In addition, the reaction temperature of the mixture cannot be sufficiently raised since the microwaves cannot permeate well into the container  10 . On the contrary, if the ratio of the height h of the container  10  to the width W thereof is too small, it is difficult to grasp the container  10  since the height h of the container  10  is insufficient, and thereby the container  10  is completely inserted into the depression  4031  (shown in  FIG. 2 ). Therefore, it is preferable for the ratio of the height h of the container  10  to the width W thereof to be maintained in a range as described above. 
     As shown in  FIG. 3 , an opening  201  is formed at the cover  20  covering an upper surface of the container  10 . The metal vaporized from the mixture contained in the container  10  is discharged outside while the container  10  passes through the microwave oven  30  (shown in  FIG. 1 ). Therefore, a vaporized metal discharged through the opening  201  can be easily recovered. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.