|Publication number||US3598888 A|
|Publication date||Aug 10, 1971|
|Filing date||Oct 3, 1969|
|Priority date||Oct 3, 1968|
|Also published as||DE1948291A1, DE1948291B2|
|Publication number||US 3598888 A, US 3598888A, US-A-3598888, US3598888 A, US3598888A|
|Inventors||Yasunobu Hosoi, Fukio Katsumata, Yoshinosuke Tada|
|Original Assignee||Fukio Katsumata, Yasunobu Hosoi, Yoshinosuke Tada|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (5), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent  inventors Minami-ku, Nagoya,
 ELECTRIC SMELTING FURNACE 2 Claims, 4 Drawing Figs.
 U.S.Cl 13/33 ] lut.Cl F27d3/l0  FieldolSearch l3/2,9,33,
 References Cited UNITED STATES PATENTS 1.807.090 5/l93l Pistor 13/33 $163,520 l2/l'964 Collin etal. l3/33 Primary Examiner Bernard A, Gilheany Assistant Examiner-R. N. Envall, Jr. A1l0rney-Waters. Roditi and Schwartz ABSTRACT: A three-phase electric smelting furnace having three electrodes arranged to form the apices of a triangle, and having material chargers. Each electrode has a plurality of the material chargers exclusively and operatively connected thereto. The lower end openings of the material chargers for each electrode are disposed along a concentric circle in symmetrical spacing with each other. The lower end openings of different groups of material charger for different electrodes are also disposed symmetrically with respect to the groups. Each material charger has a means for measuring or measuringr'and recording the change in the quantity of the materials therein. it is possible to attach a pretreating means to the material chargers for preheating, drying, calcining, or prereducing the materials.
PATENTEU Aum Olen 3,588,888
sum 1 [IF-3 PATENTED AUG] 01971 SHEET 2 [IF 3 FIG.3
ELECTRIC SMELTING FURNACE This invention relates to a three-phase electric smelting furnace having three electrodes arranged to each form the apex of a triangle for smelting pig iron, ferroalloy, nonferrous metals and chemical products, such as calcium carbide, and more particularly to a closed type electric smelting furnace having special means for charging the materials to be smelted therein.
An object of the present invention is to provide an electric smelting furnace characterized in that the furnace comprises electrodes, groups of material chargers, each group of said charge equipments belonging exclusively to corresponding one of said electrodes, respectively, and arranged in such a manner that lower end or discharge openings of said material chargers in each group are disposed along a concentric circle around the corresponding electrode in symmetry with respect to the electrode, and at the same time to lower end openings of adjacent groups of said material chargers with each other, and a means for substantially continuously measuring or recording the feeding rate, or the change in the quantity of the materials stored in each ofsaid material chargers, whereby the material consumption for each electrode and material chargers can be observed continuously-as smelting proceeds.
In a preferred embodiment of the present invention, high temperature gas substantially free from oxygen is delivered through the materials in each of said material chargers, whereby the materials are preheated and/or pretreated.
Other objects and a fuller understanding of the present invention may be had by referring to the following description taken in conjunction with the accompanying drawings, in which:
FIGS. 1 and 2 are examples of sectional plans of the roof level of an electric smelting furnace having three electrodes and actuated by a three phase A.C.- power source, according to the present invention;
FIG. 3 is a sectional elevation taken along a line abode of FIG. 1; and
HG. 4 is a chart showing an example ofcurves recorded by measuring the weight change of the materials stored in each material charger assigned for each electrode.
Like members and parts are designated by like numerals and symbols throughout the drawings.
In the following description of the present invention, an embodiment is described with reference to a closed type electric smelting furnace with three electrodes actuated by a three phase AC power source, each electrode having six material chargers belonging exclusively thereto. It should be understood that the embodiment is described and illustrated by mere way of an example, and the present invention is not restricted to such embodiment.
Referring to FIGS. 1 and 2, illustrating plans at the roof level of the furnace, three vertical electrodes I, II, and III are disposed in the space defined by a furnace wall 7, in a conventional manner, so as to form apices of an equilateral triangle. The figures also illustrate the disposition of the lower end openings of the material chargers operatively connected to each electrode.
The material chargers belonging exclusively to the electrode I, ll and ill have the lower end openings 1,2, 3, 4, 5, 6, l', 2', 3', 4', 5', 6', and l", 2", 3", 4", 5", 6", respectively.
The material chargers belonging exclusively to the corresponding electrode have the lower end openings disposed along a concentric circle, and in symmetry with respect to the axis ofeach electrode. The lower end openings ofthe material chargers belonging exclusively to adjacent electrodes, e.g., l and II, respectively, are also disposed in symmetry with each other. Due to said arrangement of the lower end openings, each material charger can exclusively feed the materials to the corresponding electrode uniformly along symmetrical directions and substantially not to the other electrodes.
Referring to FIG. 3, illustrating a sectional elevation along the line abcde of FIG. 1, each material charger of the illustrated embodiment of the invention comprises a storage tank for temporarily storing the materials, and a trough pipe for feeding the materials from the storage tank to the furnace. In the figure, it is apparent from the disposition that the materials stored in the storage tank 8, passing through the trough pipe 12 and the lower end opening 4 at the side of the furnace wall 7, are fed exclusively to the electrode I. In the same way, the materials stored in the storage tank 8' are fed exclusively to the electrode II.
In the following description, for the sake of simplicity, the storage tanks and the trough pipes are unified and referred to as the materials charger, unless otherwise specified.
The lower end openings 6 and 2' of the material charger disposed between the electrodes 1 and I] feed the materials exclusively to the corresponding electrodes I and II, respectively, and substantially not to the other electrodes, due to the positions of the lower end openings of the material charger relative to the corresponding electrodes as well as the angle of repose of the materials fed in the furnace, unless disturbances, such as hanging of the materials, take place.
Referring to FIGS. 1 and 2, those material chargers which are disposed closer to the center of the furnace than the rest, i.e. material chargers having the lower end openings 1, l, l" in FIG. land 1,1, 1",6, 6, 6" in FIG. 2 are also disposed in such a manner that they feed the materials exclusively to the corresponding electrodes, and substantially not to the others, although they are not shown in FIG. 3. Furthermore, due to the symmetrical disposition of the group of material chargers belonging to one electrode with respect to the other groups belonging to the adjacent electrodes, each electrode receive the entire quantity of the materials to be smelted by the electrode from those material chargers belonging thereto.
The number of the material chargers for each electrode is not restricted to six, as depicted in FIGS. 1 and 2, but four or more material chargers can be used for each electrode, depending on the size of the furnace. It is preferable, however, to use not less than live material chargers per one electrode.
In the illustrated embodiment, the lower end openings belonging to a particular electrode are disposed symmetrically along a circle around the electrode, but the disposition of the lower end openings according tothe present invention is not always limited to strictly symmetrical one. For instance, if the pressure of the materials fed from each lower end opening into the furnace is balanced and does not act to force the electrode away, the lower end openings belonging to an electrode do not always need to be arranged exactly along a concentric circle around the electrode, or to be symmetrically disposed at equal intervals.
It has been widely practiced to provide material chargers in electric smelting furnaces. However, except single phase electric smelting furnaces, the usable space above the furnace is extremely limited due to the electric bus conductor arrangement with a conventional construction, for instance in the case of three phase-three electrode furnace. Accordingly, the number of material chargers for each electrode is also limited. In fact, in conventional furnaces, a common material charger is usually disposed in the space between adjacent electrodes or at the center of the furnace for feeding the materials to two or three electrodes in common. There have not yet been any known polyphase electric smelting furnaces having a plurality of material chargers belonging exclusively to individual electrodes, respectively.
Thus, the electric smelting furnace, according to the present invention, is featured firstly in that there is provided a plurality of material chargers belonging exclusively to each electrode. The second feature ofthe electric smelting furnace, according to the present invention, is in that the weight change of the materials in each material charger or the feeding rate of the materials through each material charger into the furnace is continuously measured for watching. By combining these two features, outstanding effects can be achieved in controlling the operation of the electric smelting furnace.
The quantity or amount of the materials in each storage tank can be measured by the volume, height, or weight of the materials therein. There are a number of known methods for measuring them; namely, a method using suspending weight, a method using static capacitance, a method using the piezoelectric effects due to the weight, a method using isotopes, etc. Among conventional measuring methods, those for measuring the weight of the materials are preferably used, in the electric smelting furnace according to the present invention, for continuous measurement ofthe material quantity, and for recording the change of the amount of the materials as a continuous curve. The same effects are achieved by intermittent measuring and/or recording with appropriate time intervals, instead of absolutely continuous.
In the illustrated embodiment, a weight measuring means is mounted on each storage tank as shown in FIG. 3. The weight measuring means will now be described on the measuring means mounted on the storage tank 8 corresponding to the lower end opening 4 belonging exclusively to the electrode 1, which is substantially the same as the measuring means mounted on the other material chargers.
In FIG. 3, the bottom of the storage tank 8 is contracted in a funnel shape, and a weight measuring means 10, such as a strain-electroresisting element, is mounted on a support structure 9. The funnel shape bottom of the storage tank 8 is connected to the trough pipe 12 by a flexible joint 11 such as a bellows type, and the lower end of the trough pipe 12 is fastened to a furnace roof 13 to form the lower end opening 4 of the material charger.
The funnel shape bottom of the storage tank 8 is made to facilitate the measurement of the weight of the materials therein. By properly designing the funnel shape bottom of the tank 8, based on soil mechanics, which is not essential to the present invention and not described in detail here, the weight of the materials in the storage tank 8 can fairly accurately be measured without disturbing the smooth feeding of the materials therethrough. 7
When it is difficult to dispose the trough pipe I2 vertically in alignment with the axis of the storage tank 8, due to space limitation above the furnace caused by the electric bus conductor arrangement, the trough pipe 12 can be slanted at a suitable angle, which may be larger than the angle of repose of the materials. And the storage tank 8 can be disposed outside the periphery of the furnace roof 13. The storage tank 8 and the trough pipe 12 are not always restricted to be a straight shape, but if due care is taken in design, curved shape can be adopted. When there is a sufficient space for the material chargers above the furnace, the trough pipe 12 can be shortened or dispensed with by connecting the flexible joint 11 to the furnace roof 13 for directly delivering the materials from the storage tank 8 into the furnace.
The weight measuring means is connected to a weight indicator and preferably to a weight recorder, so that the change in the amount of the materials in the storage tank 8 in response to the progress of smelting can be continuously indicated and/or recorded. FIG. 4 illustrates an example of a weight recording chart thus measured.
In the chart of FIG. 4, the materials in the storage tanks corresponding to the lower end openings l, 2, 3, 4, 5, and 6 belonging exclusively to the electrode 1 decrease in weight almost at the same rate, which clearly shows a fact that the electrode l carries out smelting uniformly all around the electrode.
The chart of FIG. 4 also shows that the storage tanks are recharged with the materials after three hours.
Referring to the curves related to the electrode II, the materials through the lower end openings 3', 4, and 5' are smelted substantially at the same rate as those of the electrode 1, but the materials through the lower end openings 1, 2, and 6' slower. Thus, smelting around the electrode II is not quite smooth and somewhat slower than that around the electrode 1.
As regards the electrode lll, smooth smelting is carried out at first, but smelting of the materials through the lower end openings 3", 4", and 5" becomes somewhat slowed down after one hour to two, and the materials to be smelted through such troubles are left as they are, the furnace condition becomes worse and some serious accidents may be resulted. Therefore, proper and corrective treatments must be taken quickly.
Thus, continuous measurement of the amount of the materials in each material charger belonging exclusively to corresponding electrodes makes it possible to watch exactly and control effectively the smelting conditions at various portions around each electrode.
In the preceding description, the change in the amount of the materials is measured continuously, but the measurement can also be made intermittently with short intervals, although continuous measurement and recording are preferable.
If there should be any symptom of abnormal conditions, such abnormality is easily noted at the early stage, so that proper countermeasures can be taken quickly, such as additional charge of reducing agents, poking, etc. It is also possible to change the mixing ratio of the materials to be fed to the specific portions of the furnace according to the smelting conditions. It should be noted that such change can be carried out without affecting the other portions. Thus, the abnormality of such portions can be removed quickly at the earliest stage.
Generally speaking, in a closed type electric smelting furnace with known methods of material feeding, it is impossible to inspect directly the inside of the furnace with the eyes, and the conditions within the furnace are conjectured barely by temperatures measured under the furnace roof and the other deficient methods. Such temperatures may be affected by heat from the other portions within the furnace, so that exact temperatures at the specified part cannot be obtained. Thus, it is difficult to take proper countermeasures for abnormal conditions at the early stage, and as a result serious troubles are apt to take place rather frequently.
The inventors succeeded in constructing and operating a large closed type electric smelting furnace for 50 percent Si ferrosilicon with a capacity of 45,000 KVA, which is the largest in the world at the present. In order to ensure sufficient space above the furnace for disposing the charge equipments, it is preferable to use the electric bus conductor arrangement according to the invention A Bus Conductor System for a Three Phase Electric Furnace filed under the application number of U.S. Pat. application Ser. No. 740,237. In fact, the electric bus conductor arrangement according to said inventions was applied to said large capacity electric smelting furnace, so as to arrange the bus conductors in orderly and compact fashion. 7
Besides, with the arrangement according to said inventions, the smelting electric load characteristics can be easily be balanced among respective electrodes in the furnace, so that the conditions within the furnace can be controlled smoothly.
The electric smelting furnace according to the present invention has other interesting effects. By continuously measuring the weight change of the materials fed into the furnace, the smelting rate can continuously be determined exactly. Thus, the smelting rate or productivity for respective electrode and for the entire furnace can be readily calculated. It is also possible to determine instantaneous electric power consumption per unit weight of products by dividing the electric power load by the productivity. Thus, various data useful for the control of the furnace operation can easily be obtained.
Apart from said method, similar effects may be obtained, for instance, by measuring continuously or frequently the weight of the materials before charge into the material chargers, keeping a stock level of the materials therein constant.
The material chargers according to the present invention can also be utilized for pretreatments of the materials, such as drying, preheating, calcining and prereducing, etc., so as to save electric power consumption and reducing agents as well as to increase the productivity. By utilizing such pretreatments, the effects of the present invention can be remarkably improved. Referring to FIG. 3, for instance, such pretreatments can be conducted as follows, A closing bell 16 is provided at a funnellike hopper at the top of the storage tank 8, and gastightly closes the upper end opening of the storage tank 8, except the period of charging the materials into the storage tank 8 through the hopper 15, while providing a gas inlet 17 at a funnellike receiving hopper 14 secured at the top of the trough pipe 12 and connected to the storage tank 8 by the flexible joint 11. A gas outlet is mounted at the upper part of the storage tank 8. The materials in the storage tank 8 can be pretreated by introducing hot gas from the gas inlet 17 and discharging it from the gas outlet 18.
Under usual conditions, where the pressures at the upper part of the storage tank 8 and the lower end opening 4 are substantially equal and the flow resistance through the trough pipe 12 is high due to a narrow sectional area thereof, only small amount of the gas goes into the trough pipe 12, while most of the gas into the storage tank 8. In case of a closed furnace, the hot gas thus entered into the furnace is treated together with the furnace gas through a cleaning system (not shown).
As the hot gases for the pretreatments, gas recovered from the furnace or other gases are used after heated by a heatexchanger or burnt partially. It is essential that the hot gas is chemically reducing or inactive and substantially free from oxygen, because if the hot gas contains oxygen in excess ofa certain limit, the carbons in the materials, such as coke and coal, tend to be ignited and burned. On the contrary, the hot gas containing a large amount of reducing gas, such as carbon monoxide and hydrogen, not only dries and heats the materials depending on the temperature and the amount thereof, but also effects preliminary reduction and calcination.
The exhaust gas from the gas outlet 18 may be purged off after suitable treatment, depending on the properties thereof. If the exhaust gashas other utilities, it may be reused after applying a suitable treatment, or by introducing into the cleaning system of the furnace gas in case ofa closed furnace.
In a closed furnace, the gas pressure under the furnace roof is usually controlled to keep at a level slightly higher than the atmosphere. Accordingly, by properly controlling the pressure, for example, by suctioning, at the upper part of the storage tank 8, the furnace gas can be forced into the material chargers for pretreating the materials. Due care should be taken to keep such pretreatments constant throughout the smelting operation, the extent of which, such as preheating, calcining, and prereduction, affects the electric load characteristics of the materials, such as electric conductivity thereof, as well as the smelting conditions, Continuous measurement and control should be made on the temperature distribution of the materials at various portions in the material chargers, together with the composition of the hot gas introduced therein and the flow rate of the gas at the corresponding portions.
It is possible to use a double mechanism at the funnellike hopper l5 and the closing bell 16, so as to charge the materials into the storage tank 8 without interrupting the hot gas flow. In the case ofa single mechanism, as shown in FIG. 3, the flow of hot gas may be continued or interrupted during the charge of the materials into the storage tank 8, depending on the composition of the hot gas.
It is also possible to provide the material chargers with special facilities for effecting the pretreatments of the materials by circulating hot gas through such facilities.
In addition to said examples, such pretreatments can be applied to the materials in the material chargers by other means.
In any case, if the hot gas temperature is below 200 C. effective pretreatments cannot be achieved, and thus the temperature thereof should preferably be as high as possible.
These portions of the material chargers exposed to high temperature should be provided with suitable protection against heat.
Saving of about 250 KWI-I in electric power consumption per l,000 kg. of smelted product, and at the same time corresponding increase in productivity are achieved, by preheating the materials in the material chargers to 500 C., with the electric smelting furnace of said construction according to the present invention, under the following conditions;
Materials per 1,000 kg. of product 2,500 kg. Average specific heat of the materials 0.25 kcal./kg. C. Average temperature of the materials 500 C.
Heat loss 30 percent Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in details of construction and the combination and arrangements of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.
What we claim is:
l. A three-phase electric smelting furnace having three electrodes arranged to form the apices of a triangle, comprising three groups each including a plurality of means for charging materials to said furnace, each group of charging means being associated with respectively one of said three electrodes, each group being arranged so that the lower end discharge openings of each of said charging means in each said group are positioned in a generally concentric circle about their associated electrode and spaced symmetrically relative thereto and with respect to the lower end discharge openings of the other adjacent groups of said charging means, and means for substantially continuously measuring the change in the quantity of the charging materials contained in each of said charging means.
2. A smelting furnace as claimed in claim 3, comprising means for substantially continuously recording material quantity consumption in said furnace so as to facilitate constant surveillance of furnace operating conditions.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1807090 *||May 17, 1928||May 26, 1931||Ig Farbenindustrie Ag||Charging means for electric furnaces|
|US3163520 *||Dec 15, 1961||Dec 29, 1964||Elektrokemisk As||Process and apparatus for preheating and pre-reduction of charge to electric furnace|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3737554 *||Apr 11, 1972||Jun 5, 1973||Tanabe Kakoki Co||Electric smelting furnace of closed-type having dust removing means fixed to exhaust gas vent pipes thereof|
|US4013401 *||Sep 18, 1975||Mar 22, 1977||Dso "Cherna Metalurgia"||Apparatus for preheating a raw material charge for application to an electric furnace|
|US5479435 *||Apr 14, 1994||Dec 26, 1995||Ishikawajima-Harima Jukogyo Kabushiki Kaisha||DC arc furnace|
|US5658526 *||Nov 1, 1995||Aug 19, 1997||Shell Oil Company||Method to prepare blown films of vinyl aromatic/conjugated diolefin block copolymer|
|EP0771641A2||Oct 31, 1996||May 7, 1997||Shell Internationale Research Maatschappij B.V.||Process to prepare a blown film of a block copolymer composition|
|U.S. Classification||373/80, 373/81|
|International Classification||F27D13/00, F27D11/08, C21C5/52, F27D3/18, F27D3/00|