Abstract:
A vacuum refining furnace, including a furnace body, a graphite heater, an electrode, and a sealed furnace housing. The furnace body includes an evaporation laminate, a graphite condensing casing, and a graphite insulating casing. The evaporation laminate includes a plurality of evaporators. The evaporation laminate is nested within the graphite insulating casing, and the graphite insulating casing includes a plurality of through holes. At least two graphite condensing casings having different diameters are provided. The graphite insulating casing is nested within the graphite condensing casing having a smallest diameter, and the graphite condensing casing having a relatively small diameter is nested within the graphite condensing casing having a relatively large diameter. All the graphite condensing casings except for the graphite condensing casing having the largest diameter include a plurality of through holes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of International Patent Application No. PCT/CN2011/081087 with an international filing date of Oct. 21, 2011, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 201110318915.3 filed Oct. 19, 2011. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document or the related applications should be directed to: Matthias Scholl P.C., Attn.: Dr. Matthias Scholl Esq., 14781 Memorial Drive, Suite 1319, Houston, Tex. 77079. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a vacuum refining furnace. 
         [0004]    2. Description of the Related Art 
         [0005]    A typical refining furnace operates to separate and purify non-ferrous alloys based on the different vaporization and condensation properties of different metal elements. The liquid alloy material successively enters different layers of evaporators in the refining furnace, and is heated to a much higher temperature by the graphite heater. During the above process, the metal having low boiling point is transformed from a liquid state to a gas state by evaporation, then condensed to the liquid state again on the graphite condensing casing, and finally collected by a confluence plate. The final liquid is discharged by a discharge pipe while a non-evaporated liquid metal residue is discharged by a residue pipe. 
         [0006]    To improve the alloy treatment capacity, conventional refining furnaces are generally equipped with a graphite heater having a much higher power. However, this results in problems such as too high temperature of the graphite condensing casing and a decrease of the condensing efficiency. Some metal vapors requiring a relatively low condensing temperature cannot be condensed and the metal vapors spread randomly, thereby obstructing the exhaust pipe or resulting in short circuit, and shortening the service life of the refining furnace. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the above-described problems, it is one objective of the invention to provide a vacuum refining furnace having a high yield, high separation efficiency, and low energy consumption. The vacuum refining furnace is capable of purifying and separating multicomponent alloys comprising a Pb—Sn alloy and Pb—Sb—Sn alloy continuously. 
         [0008]    In view of the above-described problems, it is one objective of the invention to provide a vacuum refining furnace comprises a furnace body comprising an evaporation laminate, a graphite condensing casing, and a graphite insulating casing. The evaporation laminate is nested within the graphite insulating casing, and the graphite insulating casing comprises a plurality of through holes. At least two graphite condensing casings having different diameters are provided. The graphite insulating casing is nested within the graphite condensing casing having a smallest diameter, and the graphite condensing casing having a relatively small diameter is nested within the graphite condensing casing having a relatively large diameter. All the graphite condensing casings except for the graphite condensing casing having the largest diameter comprise a plurality of through holes. 
         [0009]    Design principle of the invention is as follows: the high temperature metal vapor flows from the evaporation laminate and successively exchanges heat with the graphite condensing casings of different layers after passing through the through holes arranged on the graphite insulating casing and the graphite condensing casing. For the metal having a relatively high condensing temperature, the vapor thereof is condensed on the graphite condensing casing disposed relatively close to the evaporation laminate; whereas for the metal having a relatively low condensing temperature, the vapor thereof passes through the through holes of the graphite condensing casing having a relatively small diameter and is condensed on the graphite condensing casing having a relatively large diameter, or even passes through the through holes of a plurality of the graphite condensing casings and is finally condensed on the graphite condensing casing having the largest diameter. A total condensing area within the refining furnace is largely increased after being equipped with a plurality of graphite condensing casings, and the condensing area of each graphite condensing casing varies in an ascending order. The temperature of each graphite condensing casing is progressively decreased in a ladder-type, and the magnitude of the temperature difference is relatively large, thereby being conducive to the separation of at least one metal from the liquid alloy material, broadening the condensable range of the refining furnace, and realizing the refining of the multicomponent alloy. To prevent the temperature of the graphite condensing casing closest to the evaporation laminate from being too high thereby loosing the condensing effect after the refining furnace is provided with the graphite heater having a large power, a graphite insulating casing is disposed between the graphite condensing casing having the smallest diameter and the evaporation laminate. A plurality of the through hole arranged on the graphite are capable of allowing the metal vapor to flow out. The primary functions of the graphite insulating casing are that on one hand the heat quantity from the graphite heater and the evaporation laminate is obstructed, and the temperature of the graphite condensing casing is controlled to be not too high; on the other hand, the temperature of the evaporation laminate is preserved and the evaporation of the liquid alloy material is facilitated. Thus, the heating efficiency and condensation efficiency are enhanced, and the yield is increased under the same energy consumption, so that the refining furnace is capable of condensing a plurality of metals that are difficult to condense, such as antimony, arsenic. 
         [0010]    Advantages of the invention are summarized as follows: 
         [0011]    1) the power of the graphite heater is up to 450 kW; 2) the refining furnace can treat any proportional Pb—Sn alloy and the lead residue can be controlled at below 5 ppm; 3) the refining furnace can treat a Pb—Sb—Sn alloy comprising equal to or less than 50 wt. % of antimony; 4) the refining furnace can treat a Pb—Sn—Bi alloy, an In—Sn alloy, and a multicomponent alloy comprising more than 96 wt. % of lead, the rest being gold, silver, platinum, rhenium, iridium, copper, antimony, and bismuth; 5) the refining furnace has small heat loss and high evaporating and condensing efficiency; and 6) the refining furnace has a prolonged service life, low energy consumption, high direct yield of the metal, good production environment, and stable and reliable function. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a cross-sectional view of a vacuum refining furnace in accordance with one embodiment of the invention; 
           [0013]      FIG. 2  is a cross-sectional view of an evaporation laminate; 
           [0014]      FIG. 3  is a front view of an evaporator; 
           [0015]      FIG. 4  is a cross-sectional view taken from part A-A of  FIG. 3 ; 
           [0016]      FIG. 5  is a cross-sectional view taken from part B-B of  FIG. 3 ; 
           [0017]      FIG. 6  is a connecting structure diagram between a graphite heater and a connecting base of a heater. 
       
    
    
       [0018]    In the drawings, the following reference numbers are used:  1 . Furnace body;  2 . Graphite heater;  3 . Connecting base of heater;  4 . Electrode;  5 . Sealed furnace housing;  6 . Feed pipe;  7 . Exhaust pipe;  8 . Discharge pipe;  9 . Residue pipe;  10 . First graphite condensing cover;  11 . Second graphite condensing cover;  12 . Graphite feed hoper;  13 . Evaporation laminate;  14 . Graphite insulating casing;  15 . First condensing casing;  16 . Second graphite condensing casing;  17 . Third graphite condensing casing;  18 . Confluence plate;  19 . Top plate;  20 . Bottom plate;  21 . Evaporator;  22 . Through hole of heater;  23 . Evaporation tank;  24 . Front of evaporation tank;  25 . Rear of evaporation tank;  26 . Evaporation tank grate;  27 . Material discharge hole;  28 . Supporting ring of insulating hoop;  29 . Insulating hoop;  30 . Steel casing;  31 . Graphite liner;  32 . Fire-proof filler;  33 . Heating pin;  34 . Graphite bolt;  35 . Positioning member;  36 . Liquid cooling cavity;  37 . Liquid inlet;  38 . Liquid outlet;  39 . Stopper piece;  40 . Upper cover of furnace housing; and  41 . Bottom plate of furnace housing. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0019]    For further illustrating the invention, experiments detailing a vacuum refining furnace for nonferrous metal multicomponent alloy are described hereinbelow combined with the drawings. 
         [0020]    As shown in  FIG. 1 , a vacuum refining furnace for nonferrous metal multicomponent alloy, comprises: a furnace body  1 , a graphite heater  2 , a connecting base  3  of a heater, an electrode  4 , a sealed furnace housing  5 , a feed pipe  6 , an exhaust pipe  7 , a discharge pipe  8 , and a residue pipe  9 , in which: 
         [0021]    1) The furnace body  1  comprises a first graphite condensing cover  10 , a second graphite condensing cover  11 , a graphite feed hoper  12 , an evaporation laminate  13 , a graphite insulating casing  14 , a first condensing casing  15 , a second graphite condensing casing  16 , a third graphite condensing casing  17 , and a confluence plate  18 . The evaporation laminate  13  is disposed on a center of the confluence plate  18 . The evaporation laminate  13  is nested within the graphite insulating casing  14 . The diameters of the first condensing casing  15 , the second graphite condensing casing  16 , and the third graphite condensing casing  17  are in ascending order, The graphite insulating casing  14  is nested within the first condensing casing  15 , the first condensing casing  15  is nested within the second graphite condensing casing  16 , and the second graphite condensing casing  16  is nested within the third graphite condensing casing  17 . The graphite insulating casing  14 , the first condensing casing  15 , and the second graphite condensing casing  16  are all provided with a plurality of through holes. The first graphite condensing cover  10  is disposed on the third graphite condensing casing  17 . The second graphite condensing cover  11  is disposed on the first condensing casing  15 . The graphite feed hoper  12  passes through the first graphite condensing cover  10  and the second graphite condensing cover  11  and is disposed right above an upper part of the evaporation laminate  13 . 
         [0022]    As shown in  FIG. 2 , the evaporation laminate  13  comprises a top plate  19 , a bottom plate  20 , and a plurality of evaporators  21 . The evaporators  21  are disposed between the top plate  19  and the bottom plate  20 , and through holes  22  of heaters are disposed on both the bottom plate  20  and the evaporators  21  for allowing the graphite heater  2  to pass through. As shown in  FIGS. 3-5 , the evaporators  21  are in the shape of a disc. An evaporation tank  23  is circumferentially disposed on the evaporators  21 . One end of the evaporation tank  23  is a front  24  of the evaporation tank, and the other end of the evaporation tank is a rear  25  of the evaporation tank. The front  24  of the evaporation tank and the rear  25  of the evaporation tank are separated by an evaporation tank grate  26 . The rear  25  of evaporation tank comprises a material discharge hole  27 . During the working process, the liquid alloy material falls from the top plate  19  to the front of the evaporation tank on the evaporator of the highest layer, then to the rear of the evaporation tank along the evaporation tank, thereafter flows out from the material discharge hole and falls on the front of evaporation tank of the evaporator of a next layer, and finally falls on the bottom plate  20  after several cycles. As shown in  FIG. 4 , an insulating hoop  29  is mounted on a sidewall of the evaporator  21  via a supporting ring  28  of insulating hoop. The insulating loop  29  mainly functions in conducting heat preservation on the evaporator  21 , ensuring uniformly heating of the liquid alloy material and fixing a circumferential side wall of the evaporator  21 . The evaporation tank of the evaporator has a one-way flow channel. Upon assembly, the upper and the lower evaporators are staggered with each other so that the liquid alloy therein has a enough retention time thereby facilitating the heat exchange and evaporation. 
         [0023]    A bottom of the bottom plate  20  is connected to the residue pipe  9 . The liquid alloy material after high temperature evaporation is discharged from the residue pipe  9 . A bottom of the confluence plate  18  is connected to the discharge pipe  8 , and the liquid metal after being condensed is discharged via the discharge pipe  8 . Because the liquid alloy material after high temperature evaporation or the liquid metal condensed after evaporation is apt to react with both the discharge pipe and the residue pipe made of metal, thus, a newly produced alloy will pollute the product, and meanwhile the discharge pipe or the residue pipe will become thinner or even be perforated. The discharge pipe  8  and the residue pipe  9  employ the following structures: as shown in  FIG. 1 , a graphite liner  31  is fitted within a steel casing  30 , and a fire-proof filler  32  is filled between the steel casing  30  and the graphite liner  31  for binding. The high temperature liquid metal is prevented from contacting with the steel casing of the discharge pipe  8  and the residue pipe  9  of such structures, thereby prolonging the service life thereof. 
         [0024]    2) As shown in  FIG. 6 , the graphite heater  2  comprises a heating pin  33 . The heating pin  33  and the connecting base  3  are connected via a graphite bolt  34 . To position the graphite heater  2 , a positioning member  35  is disposed at a position corresponding to the heating pin  33  on the connecting base  3 . In order to improve the current carrying capacity between the heating pin  33  and the connecting base  3 , the positioning member  35  comprises a contact surface  351  in a vertical direction and the contact surface  351  is attached to a lateral side of the heating pin  33 . The lateral side of the heating pin  33  and the contact surface  351  are bonded by a high temperature conductive filler. Therefore, the contact area between the lateral side of the heating pipe and the contact surface are increased, thereby increasing the current carrying capacity and decreasing the contact resistance. 
         [0025]    3) As shown in  FIG. 1 , the graphite heater  2  is connected to the electrode  4  via the connecting base  3 . The electrode  4  both functions in supporting the connecting base  3  and the graphite hater  2 . When using the graphite heater having a high power easily, a very high temperature of the electrode is easily resulted, thus, the electrode herein is cooled by water cooling method. A liquid cooling cavity  36  is disposed inside the electrode  4 . A liquid inlet  37  and a liquid outlet  38  are disposed on an external of the electrode  4  and communicate with the liquid cooling cavity  36 . A stopper member is disposed between the connecting base  3  and the electrode  4  for ensuring a stable connection between the connecting base  3  and the electrode  4 , and the stopper member is a stopper piece  39 . 
         [0026]    4) As shown in  FIG. 1 , the sealed furnace housing  5  is formed by connecting an upper cover  40  of the furnace housing to a bottom plate  41  of furnace housing. The upper cover  40  of the furnace housing is provided with the feed pipe  6  and the exhaust pipe  7 , the feed pipe  6  faces the graphite feed hoper  12 , and the exhaust pipe  7  is connected to a vacuum extraction device. The electrode  4 , the discharge pipe  8 , the residue pipe  9  are all protruded from the bottom plate  41  of the furnace housing and is fixed on the bottom plate  41  of the furnace housing. 
       EXAMPLE 1 
       [0027]    100 tons of a Pb—Sn alloy comprising 5 wt. % of stannum and 95 wt. % of lead was treated in the vacuum refining furnace of the invention. The vacuum degree was controlled at being equal to or less than 10 Pa. The treating capacity was 20 tons per day. After the primary distillation, 9.4 tons of a Sn—Pb alloy comprising 45-50 wt. % of lead and 90.6 tons of lead comprising equal to or less than 0.1 wt. % of stannum were obtained. 
       EXAMPLE 2 
       [0028]    100 tons of a Pb—Sn alloy comprising 70 wt. % of stannum and 30 wt. % of lead was treated in the vacuum refining furnace of the invention. The vacuum degree was controlled at being equal to or less than 10 Pa. The treating capacity was 30 tons per day. After the primary distillation, 74.4 tons of stannum comprising 5-7 wt. % of lead and 25.6 tons of lead comprising equal to or less than 1 wt. % of stannum were obtained. 
       EXAMPLE 3 
       [0029]    100 tons of a Pb—Sn alloy comprising 95 wt. % of stannum and 5 wt. % of lead was treated in the vacuum refining furnace of the invention. The vacuum degree was controlled at being equal to or less than 10 Pa. The treating capacity was 30 tons per day. After the primary distillation, 93 tons of stannum comprising equal to or less than 0.001 wt. % of lead and 7 tons of lead comprising 25-30 wt. % of stannum were obtained. 
       EXAMPLE 4 
       [0030]    100 tons of a Pb—Sb—Sn alloy comprising 42 wt. % of stannum, 40 wt. % of antimony, and 18 wt. % of lead was treated in the vacuum refining furnace of the invention. The vacuum degree was controlled at being equal to or less than 10 Pa. The treating capacity was 20 tons per day. After the primary distillation, 48.4 tons of a Pb—Sb alloy comprising equal to or less than 2 wt. % of stannum and equal to or greater than 60 wt. % of antimony, and 51.6 tons of a Sn—Sb alloy comprising equal to or less than 0.5 wt. % of lead and equal to or less than 20 wt. % of antimony were obtained. Take the Sn—Sb alloy comprising equal to or less than 0.5 wt. % of lead and equal to or less than 20 wt. % of antimony as the material for a secondary distillation, the vacuum degree was controlled at being equal to or less than 10 Pa, and the treating capacity was 10 tons per day. Thereafter, 15.6 tons of a Pb—Sb—Sn alloy comprising 20 wt. % of stannum, 60 wt. % of antimony, and 20 wt. % of lead and 36.4 tons of a crude Sn alloy comprising equal to or less than 1 wt. % of antimony, equal to or less than 0.01 wt. % of lead, and the rest of stannum were obtained. 
         [0031]    While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.