Patent Application
20090121397
The invention relates to a vacuum smelting apparatus and, more particularly, to a reduction retort and reduction furnace for smelting metal under reduced pressure.
The structure of a conventional vacuum smelting reduction furnace is composed of, as shown in
Furthermore, in the metal production process by vacuum smelting reduction method, after charging the reduction retort with the reactant material, depending on the type of metal and reducing agent used, the reduction reaction temperature is generally maintained between 1000 and 1200□ and the pressure is reduced to vacuum for the reduction reaction to take place. The reduction reaction temperature can be attained by heating the reduction retort with fuel or electricity. The conventional reduction retort is of a tubular structure. In the reduction process, heat is transferred from the inner wall of the reduction retort to the reactant material that is in direct contact with the wall. As for the reactant material that is not in direct contact with the inner wall of the reduction retort, heat is transferred thereto through radiation or from other reactant material through conduction. Because of the low thermal conductivity of the reactant material, it is apparent that the temperature of reactant material that is in direct contact with the inner wall of the reduction retort would be elevated much faster than the temperature of the reactant material that has to rely on the heat transfer from the reactant material next to them. Hence, it takes very long time for all the reactant material to reach the needed reduction reaction temperature. The reduction time, from the charging of material to the completion of reduction reaction, for metal production process by vacuum smelting reduction method using conventional reduction retort is generally between 6 and 15 hours. Obviously, long reduction time, low production efficiency and output, large energy wastage and high cost are the shortcomings of the conventional reduction retort.
Moreover, in the metal production process by vacuum smelting reduction method mentioned above, the internal pressure of the reduction retort is generally required to be less than 100 Pa. The metallic vapor constantly travels from the reactant material to the condenser during the reduction reaction process. Regional pressure may build up if the metallic vapor is trapped and accumulated within the reactant material pile. The build-up of the regional pressure to more than 100 Pa in the region where the reactant material are thickly piled will inhibit further reduction reaction from taking place, affecting the normal course of reduction reaction, and hence resulting in lower production output and wastage of energy.
Furthermore, the operating condition for a reduction retort in a metal production process by vacuum smelting reduction method is very severe, therefore refractory material is needed to make reduction retorts. However, heat-resisting metal that is resistant to higher temperature and suitable for long duration of use is very expensive. Conventionally, the general material used to make reduction retorts is heat resisting nickel-chrome-steel alloy that has a maximum working temperature of 1200□ under vacuum condition. This type of reduction retort has a short service life. It is easy to sustain damages like oxidation, creep, tear, etc. at high temperature. Therefore, large quantity of heat-resisting metal is needed to make a reduction retort, leading to high smelting cost. Not only is the need for constant turning and changing of such reduction retort very labor-intensive and time-consuming in production, it also leads to heat loss of the reduction furnace. Besides, the reduction time of metal production process by using such reduction retort, which has a maximum working temperature of 1200□, is significantly longer as compared to the reduction time of the same process carried outat a temperature much higher than 1200□.
An object of the invention is to provide a reduction retort. The reduction retort can increase the charging speed of reactant material and the discharging speed of spent residue in a metal production process by vacuum smelting reduction method and effectively increase the fill rate of the reduction retort, whereby, the production efficiency and output of a reduction furnace is enhanced while the production cost is reduced.
Another object of the invention is to provide a reduction retort that is resistant to the oxidation, creep, and tear phenomenon at high temperature, that are easily incurred in the conventional reduction retort made by heat resisting nickel-chrome-steel alloy. As a result, the service life of the reduction retort is prolonged.
The invention discloses a reduction retort that is for use in a vacuum smelting reduction furnace. The reduction retort includes: a reducing portion made of silicon carbide-based material; a condenser disposed at one end of the reducing portion; an inlet closure hermetically-connected to the condenser; and an outlet closure at the other end of the reducing portion. The reduction retort is disposed at an angle in the reduction furnace, wherein the end of the reduction retort with the inlet closure is placed at a higher position and the other end of the reduction retort with the outlet closure is placed at a lower position.
One embodiment of the invention includes heat conductors, which are solidly bonded to the inner wall of the reducing portion of the reduction retort. The heat conductors increase the heat transfer from the wall of the reducing portion of the reduction retort to the reactant material during the metal production process by vacuum smelting reduction method, thereby shortens the reduction reaction time.
Another embodiment of the invention includes vapor passages provided inside the reducing portion of the aforementioned reduction retort to timely and quickly eliminate high metallic vapor pressure formed in some parts of the reduction retort, thereby shortens the time for reduction reaction. The metallic vapor could escape from the reactant material pile to the condenser by traveling along the vapor passages quickly.
Yet in another embodiment of the invention, the aforementioned reduction retort includes a heat-insulating plug provided inside the reduction retort above the outlet closure for reducing heat dissipation. Besides, the heat-insulating plug is used to hold the reactant material in the reducing portion of the reduction retort so that the reactant material stays within the chamber of the reduction furnace throughout a metal production process by vacuum smelting reduction method. In addition, heat-insulating portion(s) can be included between the reducing portion of the reduction retort and the condenser of the reduction retort, or(and) between the reducing portion of the reduction retort and the outlet closure, to minimize heat loss.
The invention also discloses a reduction retort manufacture method, which includes: forming a reducing portion of the reduction retort, the reducing portion being made of silicon carbide-based material; disposing a condenser at one end of the reducing portion; hermetically-connecting an inlet closure to the condenser; and disposing an outlet closure at the other end of the reducing portion.
The reduction retort is formed by mixing silicon carbide-based refractory material with 4% to 8 % of water and then casting in a mold. A reduction retort with reducing portion formed as such has strengthened resistance to compression, bending, and tension, and so its service life is prolonged while the usage and manufacture cost thereof are reduced.
The invention further discloses a vacuum smelting reduction furnace, which includes: an aforementioned reduction retort and a chamber structure. There are supports at the two sides of the chamber structure, wherein the support at one side of the chamber structure is higher than the support at the other side. The end of the reduction retort at where the condenser is disposed is placed on the higher support while the other end of the reduction retort with the outlet closure is placed on the lower support.
The invention solves the shortcomings found in conventional technology, these shortcomings including the small volume of reactant material being charged into the reduction retort, low metal output, and heavy workload for workers due to inconveniences in charging of reactant material and discharging of spent residue. The invention further exhibits other improvements, which are increased raw material fill rate in the reduction retort, shortened reduction time, enhanced production efficiency and output of the reduction furnace, and lowered production cost. The invention is applicable to metal production of magnesium, strontium, zinc, beryllium, and other metal that can be produced by vacuum smelting reduction method.
The method of operation of the reduction retort 11 is described below. When reactant material needs to be charged for a vacuum smelting process, the inlet closure 14 is opened and reactant material is charged into the reduction retort 11 from the opening of the condenser 13. Since the reactant material could fall into the reduction retort 11 automatically due to self-weight, not only the workload for charging reactant material is lightened, the amount of charged reactant material for the reduction retort 11 is more than that for a horizontally disposed reduction retort. Thus, the fill rate of materials in the reduction retort is increased and it is easier to manage the volume of reactant material charged into the reduction retort; these factors are good for the realization of a complete reduction reaction and subsequently the heat utilization rate is increased. After the material is added, the inlet closure 14 is closed hermetically and a reduction reaction is carried out. After the reaction is complete, the outlet closure 15 is opened to remove spent residue. Since the outlet closure 15 is facing downward with an angle, the spent residue, due to self-weight, is very easily removed out of the reduction retort 11, resulting in a decrease in workload. Therefore, in comparison to conventional technology, the invention can increase the charging speed of the reactant material and the discharging speed of the spent residue in the metal production process by vacuum smelting reduction method, effectively increase the fill rate in the reduction retort, and in turn enhance the production efficiency and output of the reduction furnace with reduced production cost.
In order to improve deficiencies of conventional technology—long heating time for reduction reaction, low production efficiency and output per unit time, large consumption of energy, and high production cost, heat conductors are introduced in another embodiment of the invention. The heat conductors are provided inside the reducing portion 12 of the aforementioned reduction retort 11 and are solidly bonded to the inner wall of the reduction retort 11. The solid bonding is achieved by casting the heat conductors and the reducing portion 12 of the reduction retort 11 in a single mold. The aforementioned heat conductors can be any shape and in any arrangement so long as heat conduction effect is enhanced. For example, as shown in
In yet another embodiment of the invention, vapor passages are provided in the reducing portion 12 of the aforementioned reduction retort 11, for timely and quickly elimination of high metallic vapor pressure formed in some parts of the reduction retort 11 during a reduction reaction process, whereby the metallic vapor travels along the vapor passages and escapes to the condenser 13. The aforementioned vapor passages can be any structure and in any form that is suitable for gases to flow through quickly. For example, the vapor passages can be radially-arranged structures 31 having grooves 35 or T-shaped structures 32 having grooves 35 as shown in
In addition, the width of the aforementioned grooves and the diameter of the aforementioned through holes are preferably smaller than the briquette size of the reactant material as to prevent the reactant material from entering the grooves or the through holes. Furthermore, for an effective elimination of high metallic vapor pressure formed at some parts of the reduction retort, the shape and arrangement of the aforementioned vapor passages should be such that the distance between any reactant material and the closest groove, or the closest through hole, is not greater than 15 cm, and preferably, 10 cm. In comparison with conventional technology, this embodiment can timely and effectively eliminate regional pressure formed by the metallic vapor escaped from the reactant material in the reduction reaction, guaranteeing a normal and continuous course of the reduction reaction. As a result, the production efficiency and output per unit time are increased while the energy consumption and the production cost are lowered.
In general, reduction retorts are worked under a condition of a temperature over 1000□ and an internal pressure less than 110 Pa. If the reactant material at the outlet end of the reduction retort resides outside of the chamber of reduction furnace, not only would the heat in the reduction retort be transferred out of the chamber, but a part of the reactant material would not subject to direct heating in the chamber. Consequently, the required reduction reaction temperature cannot be reached, and the normal course of the reaction is affected, causing a waste of the reactant material and energy. The inventor improved the aforementioned reduction retort of first embodiment to solve this problem.
In this embodiment, a heat-insulating plug is provided in the reducing portion above the outlet closure, and thereby the heat loss in the reduction retort is greatly reduced while the reactant material at the outlet end of the reduction retort is held to stay within the chamber of the reduction furnace and subjected to direct heating. Thus energy consumption and production cost are reduced.
In the aforementioned first and second embodiments, if the portion of the reduction retort that is exposed outside the chamber of a reduction furnace is made of the same high heat-conducting material as the portion of the reducing portion that is retained within the chamber, heat in the chamber would be massively transferred out, affecting the reduction reaction. In addition, the transferred heat would increase the difficulty of hermetic sealing between the reduction retort and outlet closure, which are at high temperature. The inventor made further improvements to the reduction retort mentioned above to solve this problem.
In this embodiment, since the heat-insulating portions are separately disposed between the reducing portion and the condenser, and between the reducing portion and the outlet closure, the heat loss in the chamber of the reduction furnace is greatly reduced, solving the high temperature hermetic sealing problem. Consequently, the energy consumption and the production cost are reduced.
The reducing portion of the reduction retort of the aforementioned embodiments can be made of any refractory heat-conducting material such as refractory alloy steel. Particularly, it can be prepared with silicon carbide-based material, the use of which improves the oxidation, creep and tear phenomenon that easily occur, at high temperature, in conventional reduction retorts made of heat resisting nickel-chrome-steel alloy. The silicon carbide-based material can be a silicon carbide-based refractory cast material having a composition of 85 to 98 weight percentage of silicon carbide-based raw material, 2 to 15 weight percentage of aluminate cement, and 0.05 to 1.0 weight percentage of water reducing agent. The reduction retort with silicon carbide reducing portion has much better resistance to compression, bending, and tension, which helps in prolonging its service life, and in turn the problems originated from the frequent needs to turn or change retorts are solved. A reduction retort with silicon carbide reducing portion can work and be operated at above 1200□ but under 1500□, a temperature range which is high enough to shorten the reduction time, leading to a decrease in the cost and the usage of reduction retorts.
A manufacture method of reduction retort of the invention is as shown in
Secondly, a condenser is disposed at one end of the reducing portion (S2), and then the condenser is hermetically-connected with an inlet closure (S3). Finally, an outlet closure is disposed at the other end of the reducing portion (S4) to complete the making of a reduction retort. It is to be noted that flanges are used to couple the condenser and the reducing portion, the inlet closure and the condenser, and the outlet closure and the reducing portion.
The manufacture method of reduction retort mentioned above is just a general description; the steps can be varied according to acquired functions of the reduction retort. For instance, if the speed at which reactant material in the reduction retort is heated is to be increased, heat conductors can be provided inside the reducing portion and solidly bonded to the inner wall of the reducing portion. Also, if the high metallic vapor pressure formed regionally in the reduction retort is to be eliminated, vapor passages can be provided inside the reducing portion of the reduction retort so that the metallic vapor can escape from the reducing portion along the vapor passages to the condenser. As well, if the heat loss in the reduction retort is to be minimized, a heat-insulating plug can be provided inside the reducing portion above the outlet closure, for holding the reactant material in the reduction retort so that the reactant material stays within the chamber of the reduction furnace throughout the entire reduction process. In addition, at least one heat-insulating portion can be disposed between the reducing portion and the condenser, and/or between the reducing portion and the outlet closure, for reducing heat loss.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretations so as to encompass all such modifications and similar arrangements.
The invention discloses a reduction retort with specially arranged heat conductors solidly bonded to the inner wall of the reduction retort, vapor passages, and heat-insulating plug to increase heating speed and reduce heat dissipation, and in turn the reduction reaction time is shortened. The reduction retort is further disposed at an angle in a reduction furnace, whereby making the charging of material and discharging of spent residue more convenient for workers. Hence, the production efficiency and output of the reduction furnace are enhanced while the production cost is lowered.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200610200692.X | Jul 2006 | CN | national |
| 200610200710.4 | Jul 2006 | CN | national |
| 200610200740.5 | Jul 2006 | CN | national |
| 200610200800.3 | Aug 2006 | CN | national |
| 200610200827.2 | Aug 2006 | CN | national |
| 200610200830.4 | Aug 2006 | CN | national |
| 200610200831.9 | Aug 2006 | CN | national |
| 200610051274.9 | Nov 2006 | CN | national |
This application claims priority under 35 U.S.C. §§ 120 and 365(c) as a continuation application of prior International Application PCT/CN2007/001856, which was filed on Jun. 12, 2007, and which was not published in English under PCT Article 21(2). The disclosure of the prior international application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2007/001856 | Jun 2007 | US |
| Child | 12352564 | US |
