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Publication numberUS3617042 A
Publication typeGrant
Publication dateNov 2, 1971
Filing dateAug 12, 1968
Priority dateAug 14, 1967
Also published asDE1758814A1, DE1758814B2
Publication numberUS 3617042 A, US 3617042A, US-A-3617042, US3617042 A, US3617042A
InventorsRyuichi Nakagawa
Original AssigneeNat Res Inst Metals
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Apparatus for continuous refining of molten metals
US 3617042 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Inventor Ryuichi Nakagawa Tokyo, Japan Appl. No. 752,015

Filed Aug. 12, 1968 Patented Nov. 2, 1971 'Assignee Director of National Research Institute for Metals Tokyo, Japan Priority Aug. 14, 1967 Japan APPARATUS FOR CONTINUOUS REFINING OF MOLTEN METALS 6 Claims, 5 Drawing Figs.

U.S. Cl. 266/34 R, 75/52 Int. Cl. C21c 7/00 Field of Search 266/34, 34

I T, 34.2, 35, 36 P, 37, 24, 33, 11; 75/45, 52, 60

r I IIIIIIIIIIIIIIII4 I IlII/IIIIIII/III [56] References Cited UNITED STATES PATENTS 1,886,937 11/1932 Brett 266/37 2,622,977 12/1952 Kalling et a1. 75/55 2,741,556 5/1956 Schwartz 75/55 3,275,432 9/1966 Alexandrovsky 75/52 3,463,472 8/1969 Worner 266/34 FOREIGN PATENTS 543,245 2/1942 Great Britain 266/34 Primary ExaminerGerald A. Dost Attorney-Sherman and Shalloway PATENTEnuuv 2 Ian SHEET 10F 2 FIG] FIG.2

INVENTOR RYUICHI NAKAGAWA ATTORNEYS m 2 Ian 3,617, 042

' SHEET 2 [IF 2 INVENTOR RYUICHI NAKAGAWA ATTORNEYS APPARATUS FOR CONTINUOUS REFINING OF MOLTEN METALS This invention relates to an apparatus for continuous refining of a molten metal and to a method of continuous refining of pig iron by means of the apparatus.

The invention provides an apparatus for continuous refining of a molten metal comprising at least two trough type furnaces arranged in series so as to conduct a molten metal from one furnace to the next furnace, each of said furnaces including a flow inlet for a molten metal at one end, a flow outlet for an overflow of a refined molten metal at the opposite end, a blowing zone provided with at least one lance capable of feeding oxygen and a slag forming material into said zone, a flow zone immediately adjacent thereto, each of said zonesbeing situated between said inlet and outlet, said blow zone being a zone wherein a molten metal is vigorously mixed and reacted with fed oxygen and slag forming material and said flow zone being a zone wherein the molten metal and the resulting slag are reacted while flowing concurrently or countercurrently and the slag is separated from the molten metal as a separate layer, a slag-off hole and a gas exhaust within said flow zone disposed near the end of the flow zone which is farthest away from said blow zone and at a position higher than the levelof said flow outlet, and a skimmer for separating the slag and exhaust gas from a stream of molten metal provided in the vicinity of said slag-off hole and gas exhaust and extending to below the level of the molten metal.

The invention also provides a method of continuous refining of pig iron, which comprises feeding a molten pig iron continuously into a first furnace comprising a blowing zone to which oxygen and a slag forming material are being added and a flow zone immediately adjacent thereto, said blow zone being a zone wherein the molten pig iron is vigorously mixed, and reacted with the oxygen and slag forming material and said flow zone being a zone wherein the molten pig iron and the resulting slag are reacted while flowing concurrently or countercurrently and the slag is separated from the molten iron as a separate layer, passing said molten pig iron through said first furnace for a mean residence time of about I 'to l minutes while controlling an amount of said slag forming material fed into said blow zone per unit time within the range of one-sixticth to onefifteenth of the amount of the molten pig iron fed into the first furnace per unit time and the temperature of the molten iron leaving the first furnace to below about l,550 C., withdrawing the molten ironand the slag from the first furnace separately, thereafter feeding the so withdrawn molten iron continuously into a second furnace comprising a blow zone to which oxygen, and if desired, a slag forming material are being added and a flow zone immediately adjacent thereto, said blow zone being a zone wherein the molten iron is vigorously mixed, and reacted with the oxygen and if desired, the slag forming material and said flow zone being a zone wherein the molten iron and the resulting slag are reacted while flowing concurrently or countercurrently and the slag is separated from the molten iron as a separate layer, passing said molten pig iron through said second furnace for a mean residence time of about l to minutes while controlling the temperature of the molten iron leaving the second furnace within l,550 to l,700 C., and withdrawing the molten iron and the slag from the second furnace separately.

Referring to the accompanying drawings,

FIG. 1 is illustrative of one example of a unit furnace of the apparatus of the invention and shows its vertical section in the longitudinal direction;

H6. 2 is illustrative of another example of a unit furnace of the apparatus of the invention and shows its vertical section in the longitudinal direction;

FIG. 3 is illustrative of one embodiment of the invention whereinfour unit furnaces shown in FIG. 1 are arranged in series;

FIG. 4 is illustrative of another embodiment of the invention wherein four unit furnaces shown in FIG. 1 are connected in series;

and FIG. 5 shows another embodiment of the invention wherein an interbath is disposed between unit furnaces.

In FIG. 1, a main body 1 of the furnace is made of refractories in a trough or similar shape, for instance, tubular. in the vicinity of the left end of the furnace, there is a flow inlet 2 for a molten metal into which a molten metal, for instance, molten pig iron, to be refined is continuously fed. At the right end opposite thereto is a flow outlet for a reacted molten metal. The molten metal flows in the furnace from left to right. A holdup of molten metal in the furnace depends upon the level of the flow outlet 3. Throughout the specification and claims, a quotient obtained by dividing a holdup of a molten metal by a flow rate of a molten metal is termed a mean residence time. A series of lances 4 for blowing oxygen and a slag forming material into a molten metal in the furnace are located in the vicinity of the flow inlet of the furnace. It is preferred that the lances should be arranged inclined at a suitable angle,. as shown in the drawings, in order for the oxygen to collide with the molten metal at a suitable angle. The slag forming material may be supplied by a means different from that for feeding the oxygen, but it is convenient and advantageous to feed it in the form of fine powder together with oxygen under pressure. The oxygen and the slag forming material are reacted with the molten metal while being mixed vigorously in the zone where the oxygen and slag forming material are blown in. The molten metal and the resulting slag which have left the blow zone are further reacted while flowing concurrently in the flow zone immediately adjacent thereto. At the terminal portion of said flow zone, the slag is separated from the layer of the molten metal as a separate layer. It is imperative that the blow zone should be directly adjacent to the flow zone. This means that there should be no such material as a barrier between them which will be substantially detrimental to the flow of the metal and slag. A suitable length of the flow zone depends upon the scale of the furnace, angle of the lance and the flow velocity of the molten metal, but should be longer than one necessary to settle the disturbance from the blow zone. Near the end of the flow zone which is farthest away from the blow zone are provided a slag-off hole 6 perforated in the sidewall of the furnace and a gas exhaust 7 for discharging gas from the ceiling of the furnace to outside the furnace. The lowest level of the slag-off hole 6 should be above the level of the overflow dam 3 of the molten metal so as not to cause the flowout of the metal from the slag-off hole 6. Downstream of the slag-off hole 6 and gas exhaust 7 is provided a skimmer extending to below the level of the molten metal via the surface of the slag layer and molten metal from the upper portion of the furnace, which makes it possible to separate the slag and exhaust gas from a stream of molten metal, and discharge them from the slag-off hole 6 and the gas exhaust 7, respectively. The molten metal passes between the lower end of the skimmer 5 and the furnace bottom and is withdrawn from the flow outlet 3 to outside the furnace. It is preferable that a supplementary barrier 8 should be provided in the vicinity of the slag-off hole to prevent the molten metal from getting into the slag-off hole 6.

FIG. 2 illustrates other typical unit furnace usable in the invention. In this type of furnace, a stream of molten metal is countercurrent to that of a slag. A molten metal to be refined which has been fed from the flow inlet 2 is first contacted countercurrently with a stream of a slag in a flow zone of the furnace, subjected to the blowing of oxygen and a slag forming material in a blow zone, and flows from the flow outlet through the lower portion of the skimmer 5 on the right side. On the other hand, the slag resulting in the blow zone and molten slag fed together with molten metal from the flow inlet 2 are pushed in a direction opposite to that of a stream of molten metal by the jetting of gas from lances 4, and are discharged from the slag-off hole 6 disposed in the vicinity of the flow inlet 2. The gas exhaust 7 is located in proximity to the slag-off hole 6, and downstream of the gas exhaust 7 and slag-off hole 6 with respect to a stream of gas and a stream of slag is provided the skimmer 5 extending from the upper portion of the furnace to below the level of the molten metal.

FIG. 3 illustrates one embodiment of the invention wherein four unit furnaces shown in FIG. 1 are aligned in series. A molten metal flows from one furnace to another by the action of an overflowing stream and terrestrial gravity. It is also possible to arrange the furnaces on one plane and flow a molten metal from one furnace to another by such a suitable transferring means as a magnetic pump. Also, it is possible to arrange a plurality of furnaces of the type shown in FIG. 2 in series, instead of the furnaces shown in FIG. 1.

The apparatus of the invention is suitable for use in the refining of a molten metal, particularly, the refining of a mol' ten pig iron, i.e., steelmaking. Explanation will now be made about an example of continuous manufacture of steel from pig iron by using a multistaged furnace as shown in FIG. 2. A molten pig iron is continuously fed into a first furnace from flow inlet 2, and is passed through the first furnace for a mean residence time of about 1 to 15 minutes. In the example shown in FIG. 3, the molten pig iron is reacted with the blown oxygen and slag forming material in the blow zone while being vigorously mixed with them. No particular means for mixing is necessary, and the mixing is sufficiently effected by blowing oxygen at a gauge pressure of about 2 to l kg./cm.from a lance placed at a height of about 5 to 20 cm, for instance, from the surface of the molten iron. Although it is advantageous to feed the slag forming material, together with oxygen, in the form of fine powder, it may be added to molten pig iron by another means. The slag forming material consists of lime and its equivalent (for instance, slaked lime and limestone), but it is often preferable to use a small amount of fluorspar and/or bauxite, etc. The molten pig iron which has left the blow zone is reacted in the flow zone while flowing cocurrently, and the slag is separated as a separate layer from the molten iron. The flow zone has a length at least the same as that of the blow zone. It is preferable that the ratio of the lengths of both should be 2 or more.

As already described, the flow zone is immediately adjacent to the blow zone, and there is no member between them which may interrupt the flowing of molten pig iron and slag. An amount per unit time of the slag forming material (i.e., lime or its equivalent) to be added to molten pig iron may be one-sixtieth to one-fifteenth calculated at CaO, of the weight of molten pig iron fed into the first furnace per unit time. In contrast to the fact that the addition of about 70 to 120 Kg. of a slagforming material per ton ofa molten pig iron is necessary in an ordinary steelmaking, it will be noted that the amount of slagforming material in the present invention is relatively small. The temperature of a molten iron leaving the first furnace should be controlled below about 1,550 C. Ordinarily, it should preferably be controlled within a temperature range of about l,300 to l,500 C., preferably l,350l,400 C. If the above conditions are observed, mainly dephosphorization, silicon removal, removal of manganese and a minor degree of decarburization can be effectively conducted. For instance, it is possible to continuously achieve a dephosphorization degree of about 50 to 70 percent, a silicon removal degree of about 70 to 90 percent, a manganese removal degree of about 60 to 90 percent and a decarburization degree of about to 30 percent.

The product obtained through the dephosphorization, silicon removal and manganese removal in the first furnace is caused to flow into a flow inlet 2 of the second furnace from the flow outlet 3 of the first furnace. The structure of the second furnace may be the same as that of the first furnace. Since, however, the second furnace is intended for decarburization and has a high temperature inside, it is desirable to use a different refractory material to construct the furnace. This is one of the advantages which can be realized by the employment of a multistaged furnace. The molten iron is passed through the second furnace for a residence time of l to minutes, preferably about 6-8 minutes. The addition of a slag forming material to the blowing zone of the second furnace is not always necessary. Even if it is added, an amount less than about one-fortieth of the amount of molten iron fed, for instance about 20 to 25 Kg. per ton of the molten pig iron, is sufficient in most cases. The temperature of molten iron leaving the second furnace is controlled within the range of about l,550 to 1700 C., preferably about l,620 to l,650 C. Thus, a high degree of decarburization and a minor degree of silicon removal, manganese removal and dephosphorization are effectively accomplished in the second furnace. By the refining in the first and second furnaces, a decarburization degree of about 95 percent or more, a silicon removal degree of about 95 to 99 percent and a manganese removal degree of about 70 to percent in total can be continuously achieved, for instance. There is hardly any appreciable dephosphorization effect in the second furnace. A part of sulfur is transferred into the slag or oxidized and removed. In general, there is a tendency that at a high treating temperature such as about 1,550 C. to l,700 C., phosphorus which has once been removed from a molten iron again returns to the molten iron. ln the practice of the invention, however, phosphorus is removed from molten pig iron in the first furnace and separated as a slag, and there is no such disadvantage as the increase in the phosphorus content of the iron in the high-temperature operation in the second furnace. This is also one of the advantages of the invention.

The product from which phosphorus, decarburization manganese and carbon have been removed in the first and second furnaces is caused to flow into a third furnace from a flow inlet 2", where a final decarburization and desulfurization are effected. The structure of the third furnace may be the same as that of the second furnace. When the third furnace is operated under the same operational conditions, a decarburization degree of as high as about 99 percent and a desulfurization degree of about 50 to 70 percent in total can be achieved. The product which has left the third furnace is then conveyed to a fourth furnace where deoxygenation and composition finishing are conducted. Usually, oxygen blowing is not necessary in the fourth furnace.

The method of the invention has been described above with reference to a four-staged furnace, but the furnace usable in the practice of the method of the invention may consist of two unit furnaces or of a plurality of unit furnaces. For instance, the removal of phosphorus, silicon and manganese if effected in a first furnace; the removal of carbon and sulfur is effected in a second step; and successively deoxygenation and composition finishing are carried out in a third furnace. Also, it is possible to conduct the operation of the first furnace as explained above with the use of two furnaces, conduct the operation of the second furnace as explained above in one or more furnaces, and finally carry out deoxygenation and composition finishing. Furthermore, a predesulfurized pig iron may be subjected to the said treatment in the first furnace followed by said treatment in the second furnace in accordance with the invention. It should be understood that a step of deoxygenation and composition finishing may be carried out with the use of an ordinary electric furnace or another type of furnace such as open hearth.

The description of commercially available steel amounts to several thousands or more. lt is often disadvantageous, and sometimes impossible, because of the necessity of stopping the operation for a while or for some other reasons, to vary steelmaking conditions and, in some cases, the construction of the furnace according to the composition, etc. of the desired product. According to the present invention, a base steel of a predetermined composition is produced by practicing the method of the invention constantly up to the second stage or to a certain stage thereafter, and a subsequent refining and/or composition finishing can be applied to the base steel so as to obtain a final product which a customer desired. By so doing, it is possible to meet various requests.

It has been found that the use of a unit furnace having a flow zone where a molten pig iron and a slag flow countercurrently with each other is often advantageous. In this case, the amount ofa slag forming material necessary in the first furnace may be far less, and sufficiently be about one-half to two-thirds of that necessary in a unit furnace of the type shown in FIG. 1. Hence, there is an advantage that the amount of a slag discharged is small and the loss of iron contained in it is smaller.

The provision of interbaths 9, 9' and 9" between adjacent furnaces as shown in FIG. 5 is advantageous. In the interbaths, molten iron flowing out from a furnace is received and left to stand, thereby effecting the homogenization of the molten iron and, if necessary, conducting slag-off. By utilizing a time interval during the transferring of molten iron from one furnace to another, the composition and the temperature, etc. of molten iron are determined. The results together with analytical values for exhaust gas are transmitted as signals to a suitable automatic control device (not shown) so that the operational conditions of the next furnace may be automatically controlled. The shape of the interbath is not particularly restricted, but to homogenize the flow of molten iron therein, it is preferable to provide baffles l0, l0 and The interbath need not always be provided for every furnace, and where to provide it will have to be decided according to the respective situation.

One characteristic feature of the invention is that the silicon removal reaction, dephosphorization reaction and decarburization reaction, etc. can each be conducted in a designated furnace by adjusting the operational conditions in each unit furnace. Thus, in the present invention, each unit furnace of the apparatus can be constructed by a refractory material which is suitable for each reaction. If erosion of a certain unit furnace occurs, it is necessary to repair that furnace alone. If a furnace is likely to undergo a considerable damage, two of such furnaces are arranged in parallel to use one of them interchangeably. Consequently, unlike the conventional batch method, it is not necessary to stop the operation of the entire apparatus when repairing is necessary. This means the curtailment of great deal of expenses, and is one of the advantages obtained by the present invention.

EXAMPLE 1.

The apparatus used is the type shown in FIG. 1 wherein three unit furnaces having a length of 400 cm. are arranged in series. Each of a first furnace and a second furnace has a blowing zone with a length of 110 cm. and a flow zone of 210 cm. In the blowing zone, seven copper lances with a nozzle diameter of 5 mm. having external cooling means are aligned at intervals of 18 cm. at an angle to the flow direction of 5 with the distance between the stationary bath surface and the tip of the nozzles being 5 cm. A slag and a metal were caused to flow concurrently. A third furnace has a blowing zone with a length of cm. and a flow zone with a length of 280 cm. In the blow zone, three lances are aligned at the same level, angle and interval as in the first furnace.

. TABLE 3 In this example, the molten pig irons indicated in table 1 Nun1b01- were each fed continuously into the first furnace at a rate of sqarpmg 120 Kg. per minute, and passed through each of the furnaces 1 2 3 successively for a residence time of about 7 minutes for each gxy e i (ms/minutes) 3. 0; 3. 1 o s; furnace. The refining conditions in each furnace and the comgg a fgg h jg 8 2 position and temperature in a constant cond1t1on of a product 'l emperature C.) 1, 360 1,520 1,650 1,610 leaving each furnace are shown in table l. 1 g); 6O 0. 30 10 s1 0.88 0.21; 0. 02 0. TABLE 1 Mn 0.54 0.21 0.2 0.3. P... 1.01 0.2 0. 03 0. 0 I Number 8 0. 00 0.04 0. 02 0. 0 ta g Additive pig iron 1 2 3 1 Ferromanganesc, ferrosilicon. Oxygen (mfi/rninutes) 2. 74 3.0 1.4 C110 (kg./minutes). 6.3 0.8 0.8 CaFz (kg./minutes).. 0. 5 0.4 0.4 EXAMPLE 4 Temperature C.) 1,370 1, 450 1, 680 1, 700 g 3 69 2 50 0 30 0 08 In this example, the apparatus used includes two furnaces of 1.1 0.20 0.02 0.1 the slag-metal countercurrent type as shown in FIG. 2 and the third furnace used in exam le 1, which are ali ned in series. 0.18 0. 03 0. 0a 0. 03 P g 0.05 0. 01 0.01 The first and second furnaces have a blow zone and a flow l Ferromanganese, ferrosflleon.

In the first furnace niost of Si, P and S and a part of Mn were 5 conducted. A very mild steel was produced. The yield of Fe was 96 percent.

EXAMPLE 2 0 In this example, the reaction in the first furnace as shown in example 1 was conducted in two furnaces. A greater part of Si and a part of P can C were removed in the first furnace, and a greater part of P, a greater part of the remaining Si, and a part of C were removed in the second furnace. A greater part of the remaining C was removed in the third furnace, and in the fourth furnace, the composition was finished by addition of ferromanganese and ferrosilicon. The fourth furnace did not have any lance. The structure and the mode of arranging lances of the first, second and third furnaces were the same as 0 those described in example 1 with respect to the first furnace except that the number of lances was six for the first furnace, four for the second, and five for the third.

The refining conditions and the composition and temperature in a constant condition of the product leaving each fur- 25 nace are shown in table 2. Operations other than those indicated in table 2 were the same as in example 1.

In this example, the apparatus described in example I was used, and pig iron having a high phosphorus content was 45 treated under the refining conditions indicated in table 3.

Otherwise, the procedures in example 1 were repeated. In dealing with pig iron having a relatively high-phosphorus content, it is advantageous to use a slag forming material in the first furnace in a somewhat larger amount, and adjust the mm 50 perature of molten pig iron leaving the first furnace to a somewhat higher point. The results are shown in table 3.

zone whose positions are reversed, and except the provision of a gas exhaust and a slag-off hole in the vicinity of a molten metal flow inlet, have the same dimension and lance providing conditions as those of the first furnace used in example 1. The

direction of inclining of the lance is however opposite. Between the first and second furnaces, and between the second and third furnaces, an interbath containing a baffle is located, and there the homogenization and additional removal ofa slag are conducted.

Pig iron having a high phosphorus content were treated under the conditions indicated in table 4 at a rate of about 120 Kg. per minute. The results are shown in the following table. The mean residence time in each furnace was about 7 minutes, and a residence time in each interbath was about 2 minutes.

TABLE 4 Number- Starting pig iron 2 3 Oxygen (m /minutes) CaO (kg/minutes). CaFz (kg/minutes)... Temperature C.) Perccant:

9. 92 ONMHUW mosh-o OUOUI H IwlOQUIUI OP-UIO l Ferrosillcon, ferromanganeso.

EXAMPLE The apparatus used includes three unit furnaces aligned in series each of which has a total length of 440 cm., a blow zone with a length of 130 cm. and a flow zone with a length of 80 cm., and a capacity of receiving 800 Kg. of iron. In each unit furnace, nine lances with an inner diameter of 5 mm. are arranged at intervals of cm., at an inclined angle of 5. The depth of molten pig iron was 15 cm., and a mean residence time for each unit furnace of 6 minutes. The feed pressure of oxygen was 3 KgJcm. gauge. The operation was conducted smoothly. The results are shown in table 5.

TABLE 5 Number- Starting H A pig iron 1 3 e Scrap 3 1 1 Oxygen (mF/minutes) CaO (kg/minutes)... CaF: (kg/minutes) Temperature C.) Percent:

Si Mn sIIIIIIIIIIII Additive Basicity Iclaim:

1. An apparatus for continuous refining of a molten metal comprising at least two trough type furnaces arranged in series so as to conduct a molten metal from one furnace to the next furnace, each of said furnaces including a flow inlet for a molten metal at one end, a flow outlet for an overflow of a refined molten metal at the opposite end, a blowing zone provided with at least one lance capable of feeding oxygen and a slag forming material into said zone, a flow zone immediately adjacent said blowing zone and contiguous therewith, the ratio of the length of said flow zone to the length of said blowing zone being at least 1:1, each of said zones being situated between said inlet and outlet, said blowing zone being a zone wherein a molten metal is vigorously mixed and reacted with said oxygen and slag forming material, said flow zone being a zone wherein the molten metal and the resulting slag are reacted and the slag is separated from the molten metal as a separate layer, a slag-off hole and a gas exhaust within said flow zone disposed near the end of said flow zone which is farthest away from said blow zone and at a position higher than the level of said flow outlet, and a skimmer for separating the slag and exhaust gas from a stream of molten metal provided in the vicinity of said slag-off hole and gas exhaust and extending to below the level of the molten metal.

2. The apparatus for continuous refining of a molten metal according to claim 1 wherein a reservoir for the molten metal is provided between one furnace and another furnace adjacent thereto, said reservoir having a capacity for temporarily holding a flowing molten metal halfways in a path through which a molten metal from one furnace is continuously transferred into a flow inlet of the next furnace.

3. The apparatus for continuous refining of a molten metal according to claim 1 wherein said blowing zone in the furnace is located on the side near said flow inlet for the molten metal and said flow zone is located on the side near said flow outlet for the molten metal.

4. The apparatus for continuous refining of a molten metal according to claim 1 wherein said blowing zone in the furnace is located on the side near said flow outlet for the molten metal, and lances are provided inclined so that oxygen may be blown in a direction opposite to the direction of movement of the stream of molten metal.

5. The apparatus of claim 1 wherein said lance of said blowing zone and said flow inlet and flow outlet are so positioned that said molten metal and resulting slag flow concurrently.

6. The apparatus of claim 1 wherein said lance of said blowing zone and said flow inlet and flow outlet are so positioned that said molten metal and resulting slag flow countercurrently.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3822871 *Jan 18, 1972Jul 9, 1974T MorisakiApparatus for continuous processing of sulfide ores and apparatus therefor
US3901489 *Dec 28, 1973Aug 26, 1975Mitsubishi Kizoku Kabushiki KaContinuous process for refining sulfide ores
US3912501 *May 19, 1972Oct 14, 1975De Castejon Javier GonzalezMethod for the production of iron and steel
US5045112 *Aug 22, 1988Sep 3, 1991Northern States Power CompanyCogeneration process for production of energy and iron materials, including steel
US5055131 *Oct 16, 1989Oct 8, 1991Northern States Power CompanyCogeneration process for production of energy and iron materials
US5064174 *Feb 8, 1988Nov 12, 1991Northern States Power CompanyApparatus for production of energy and iron materials, including steel
US5066325 *Feb 24, 1989Nov 19, 1991Northern States Power CompanyCogeneration process for production of energy and iron materials, including steel
US5217527 *Nov 20, 1991Jun 8, 1993Mitsubishi Materials CorporationProcess for continuous copper smelting
US5258054 *Nov 6, 1991Nov 2, 1993Ebenfelt Li WMethod for continuously producing steel or semi-steel
US5398915 *Oct 29, 1993Mar 21, 1995Mitsubishi Materials CorporationApparatus for continuous copper smelting
US5431710 *Apr 14, 1993Jul 11, 1995Ebenfelt; Li W.Method for continuously producing iron, steel or semi-steel and energy
US5733358 *Sep 11, 1995Mar 31, 1998Usx Corporation And Praxair Technology, Inc.Process and apparatus for the manufacture of steel from iron carbide
US5925165 *Sep 14, 1995Jul 20, 1999Von Roll Umwelttechnik AgProcess and apparatus for the 3-stage treatment of solid residues from refuse incineration plants
Classifications
U.S. Classification266/215, 266/225, 75/957, 266/230, 75/539
International ClassificationC21C5/56
Cooperative ClassificationY10S75/957, C21C5/567
European ClassificationC21C5/56D