US3687430A - Method of and apparatus for desulfurizing pig iron - Google Patents

Method of and apparatus for desulfurizing pig iron Download PDF

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Publication number
US3687430A
US3687430A US69600A US3687430DA US3687430A US 3687430 A US3687430 A US 3687430A US 69600 A US69600 A US 69600A US 3687430D A US3687430D A US 3687430DA US 3687430 A US3687430 A US 3687430A
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United States
Prior art keywords
vessel
pig iron
outlet
desulfurizing
inlet
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Expired - Lifetime
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US69600A
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English (en)
Inventor
Hans-Peter Schulz
Jorn Mandel
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Rheinstahl Huettenwerke AG
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Rheinstahl Huettenwerke AG
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00—Refining of pig-iron; Cast iron
    • C21C1/02—Dephosphorising or desulfurising

Definitions

  • ABSTRACT Pig iron in the tap spout of a blast furnace is desulfurized by passing it through a vessel containing a rotating inverted T-shaped stirring element which mixes the pig iron and a desulfurizing agent as they pass from the inlet to the outlet of the vessel. From the outlet, a trough conveys the treated pig iron to a flue with an overflow edge located at a level above the bottom surface of the outlet. The flue is arranged to separate the pig iron from the spent desulfurizing agent.
  • the present invention is directed to an apparatus for and a method of desulfurizing pig iron and, more particularly, it is directed to an arrangement for stirring the pig iron and a desulfurizing agent as it passes through a vessel in the tap spout of a blast furnace.
  • ladle desulfurization methods have been used only in a few special cases, for example, in smelting silica-rich iron ores to reduce the specific amount of slag to economical values, and in the production of low-sulfur special steels or for reducing excessive sulfur contents to avoid problems in the operation of the furnace.
  • the primary object of the present invention is to afford a safe method and apparatus for desulfurizing pig iron in a blast furnace tap spout by adding a desulfurizing agent which permits a uniform and considerable reduction in the sulfur content, even with a greatly varying tapping rate of the pig iron because of a particularly high reaction velocity.
  • the arrangement is also suitable for processing the entire pig iron production of a large blast furnace and it is not limited to the use of soda as a desulfurizing agent.
  • a vessel having a refractory lining is located in the tap spout of a blast furnace and contains an inlet and outlet to provide through flow of the pig iron.
  • the bottom surface of the outlet is substantially at the level of the bottom surface of the vessel.
  • a trough conveys the flow of pig iron to a flue with an overflow edge located at a level above the bottom surface of the outlet.
  • a stirring element of inverted T-shaped construction is arranged to rotate about its vertical axis with its transverse head or blade rotating in the path of flow of the pig iron between the inlet and the outlet.
  • the desulfurizing agent is supplied into the vessel so that it is mixed with the pig iron by means of the stirring member.
  • the intensive mixing of the desulfurizing agent and the pig iron flowing through the vessel achieved by means of the stirring member produces such a high reaction velocity that the desulfurization is completed to the desired degree even where variations in the pig iron flow occur due to frequent variations in the tapping rate.
  • the rotation of the drum effects a thorough Y mixing of the desulfurizing agent with the pig iron melt and the stay period of the unit volumes of pig iron and slag passing through the rotating drum are the same for a certain rate of flow of the pig iron.
  • the extent of desulfurization is unsatisfactory at high tapping rates. Therefore, it.
  • the range of the dwell period prevents the achievement of a total low sulfur content since the unit volumes only briefly desulfurized would be fed with a relatively high sulfur content from the apparatus and the unit volumes which are desulfurized'for a much longer time would have a relatively much lower sulfur content and the desulfurization rate would be hardly more effective than with a medium dwell period because of the approximation with equilibrium values. Consequently, it would be expected that the unit volumes desulfurized for a longer period of time would afford no compensation for those unit volumes which were only briefly desulfurized.
  • the method of the present invention can be carried out to effect a very thorough mixing of the pig iron and desulfurizing agent, and thereby attain a rapid desulfurization, by using a stirring member having an inverted T-shaped form with the bottom beam-shaped portion of the stirring element sheathed in refractory material.
  • a stirring member having an inverted T-shaped form with the bottom beam-shaped portion of the stirring element sheathed in refractory material.
  • the bottom surface of the inlet for flowing pig iron into the vessel is located at the level of the bottom inner surface of the vessel, and that the top surface of the inlet is lower than the overflow edge of the flue while the top surface of the outlet is slightly higher than the overflow edge.
  • the vessel contains an opening for adding the desulfurizing agent for mixture with the pig iron.
  • the level of the pig iron within the vessel is kept constant by the overflow edge of the flue. Accordingly, the top surface of the outlet retains the desulfurizing agent so that it exits from the vessel at a somewhat lower rate than the pig iron. This feature enhances the effective utilization of the desulfurizing agent.
  • the inner surface of the inlet due to its relative position to the overflow edge mentioned above, is lower than the constant pig iron level in the vessel so that the ejection of desulfurizing agents by the stirring member as well as the introduction of blast furnace slag into the vessel are avoided.
  • the inlet for the pig iron into the vessel is arranged in its cover and the top surface of the outlet is located slightly higher than the overflow edge of the flue for the pig iron.
  • the kinetic energy of the pig iron jet falling freely into the pig iron bath in the vessel is also used for mixing the pig iron and the desulfurizing agent. Also, the desulfurizing agent is added into the pig iron jet as it falls into the vessel.
  • the bottom edge of the beam-shaped stirring element is arranged between 2 and 10 cm above the bottom of the vessel, as under 2 cm, the danger of striking against slag residue is too great, and above 10 cm there is a risk that short circuiting might occur.
  • the stirring member With these dimensions of the stirring member, a vigorous and rapid mixing of the desulfurizing agent and the pig iron is achieved with a resultant high reaction velocity. With lower tapping rates of up to 3 t/min., the same result is attained if the interior diameter of the vessel is less than 1.5 m and the length of the beamshaped stirring element is 0.45 to 0.80 times the inside diameter of the vessel.
  • the speed of revolution of the stirring member is advantageously between and rpm.
  • a long contact period between the pig iron and the additive can be achieved if the inlet for the pig iron is aligned in the direction of the axis of the vessel and if the outlet for the pig iron is arranged in the third quadrant of the vessel, counting the quadrants in the direction of rotation starting from the inlet in the direction of rotation of the stirring member, and with the opening for the addition of the desulfurizing agent located in the fourth quadrant.
  • This arrangement of flow through the vessel counteracts any direct passage by encouraging the formation of circular currents within the vessel.
  • the inlet for the desulfurizing agent is located in the fourth quadrant, initially the additive is moved by the stirring element, away from the outlet, and is mixed with the pig iron in the range of the inlet by the turbulence with the entering flow of pig iron.
  • its upper edge is arranged at least 60 cm above the upper edge of the pig iron outlet.
  • vessel diameters of 1.2 m are advisable, for tapping rates of 6 t/min the vessel diameter should be about 2 m.
  • the invention provides that with a blast furnace slag with a base degree of CaO/SiO which is less than 1.2, even when using coke with a high-sulfur content of over 1 percent, it is possible to reduce the sulfur content to lower sulfur values.
  • Sulfur contents of less than 0.010 percent can be reliably achieved with the present method disclosed herein and the furnace output is increased by to percent compared to conventional methods; additional cost savings are possible by utilizing cheap high-sulfur coke.
  • FIG. I is a vertical sectional view of apparatus for desulfurizing pig iron, in accordance with the present invention, with a horizontal inlet for the pig iron into a vessel forming a part of the apparatus;
  • FIG. 2 is a vertical sectional view, similar to FIG. 1, illustrating another embodiment of the present invention with a pig iron inlet located in the upper end of the vessel;
  • FIG. 3 is a horizontal sectional view through the vessel shown in FIG. 1.
  • FIG. 1 apparatus for desulfurizing pig iron in the tap spout of a blast furnace is disclosed in which a desulfurizing agent 1 is supplied into a vessel 2 through an opening 12 located in the upper surface of the vessel and pig iron is admitted into the vessel through an inlet 3 located at the bottom of the vessel and an outlet 4 for the treated pig iron is located on the bottom of the vessel on the opposite side from the inlet.
  • a trough extends from the outlet 4 to a flue 6 having an overflow edge 7 for the treated pig iron.
  • a stirring member 8 which rotates about its vertical axis and has a vertically depending shaft 8a and a horizontally disposed beam-shaped stirring part 9 attached to the lower end of the shaft and forming, in combination therewith, an inverted T-shaped structure.
  • the stirring part 9 is covered with refractory material and a gear motor 10 is mounted on the upper surface of the vessel 2 for rotating the shaft 8a and stirring part 9 about the vertical axis.
  • the pig iron inlet 3 and outlet 4 are located at about the same level and the lower surface of each is flush with the bot tom interior surface 5 of the vessel 2.
  • the bottom surface 5 of the vessel and the outlet 4 are slightly inclined in the direction of flow to facilitate the emptying of the vessel after the tapping operation is completed.
  • the direction of rotation of the stirring member 8 is shown by the arcuate arrows and considering the inlet 3 as located on the radius between the first and fourth quadrants, counting the quadrants in the direction of rotation of the stirring member, the outlet 4 is located in the third quadrant. Further, as shown in FIG. 3, the outlet 4 conically widens or diverges toward the outside to a trough 20 to avoid any scaffolding of the slag.
  • the bottom surface 11 of the beam-shaped stirring part 9 of the stirring member is positioned closely above the bottom surface 5 of the vessel, that is, about 5 cm. With this arrangement any short circuiting of the pig iron between the inlet and outlet without reaction with the desulfurizing agent is avoided. As indicated in FIG.
  • the pig iron inlet 3 is located on one of the diameters of the vessel 2.
  • the desulfurizing agents 1 are added through the opening 12 in the top of the vessel into the pig iron entering through the inlet and the opening 12 is located in the fourth quadrant of the vessel based on the direction of rotation of the stirring member. Accordingly, the arrangement of the pig iron inlet and the opening for the desulfurizing agents assure an increased dwell period of the desulfurizing agent within the vessel and, accordingly, in contact with the pig iron.
  • the length of the stirring part 9 is 0.5 times the inside diameter of the vessel, and the upper edge of the vessel is positioned cm above the upper edge or surface of the outlet 4 to prevent any spurt out of the pig iron during stirring.
  • the height or level of the pig iron within the desulfurizing vessel is determined by the position of the overflow edge 7 of the flue 6 located in the trough 20 spaced outwardly from the outlet 4, and the arrangement of the flue affords the separation of spent desulfurizing agent from the pig iron.
  • an inlet 3a for the pig iron is located in the upper surface or cover 13 of the vessel 2.
  • the pig iron and the desulfurizing agent enter the vessel through the same inlet 3a.
  • an emergency tap 14 is located in the vessel for emptying it in the event any difficulties arise. After the tapping of the blast furnace is completed, the flue is pierced in its lower portion at or shortly before the end of the tap so that the solid desulfurization slag is retained or is bypassed.
  • the desulfurizing apparatus as illustrated in FIG. 1, has been used to desulfurize open hearth pig iron in blast furnace tapping.
  • the following table displays the results for high pig iron tapping rates of 4 7 t of pig iron/min with a vessel of 2,000 mm inside diameter and also for low tapping rates of about 1 t of pig iron/min with a smaller vessel of 1,200 mm inside diameter.
  • Different agents were employed for achieving the desulfurization. When lime and methane were used, the methane was injected into the melt through a blow lance located outside the range of the beam-shaped stirring part 9.
  • Apparatus for desulfurizing pig iron as set forth in claim 1, wherein the upper surface of the outlet from said vessel is located slightly above the level of the overflow edge of said flue, and the inlet for the pig iron Table: Continuous Desullurization of Open Hearth Pig Iron Length of Beam-Shaped Part of Stirring Element:
  • the apparatus described above can also be used for alloying and for the primary purification of pig iron or other liquid metal melts during tapping.
  • the apparatus can also be used with advantage for the desulfurization of cast iron in foundries.
  • the vessel With the usual outputs of cupola furnaces used in such operations of about 1 ton per hour, the vessel can be small and can be easily connected into the usual flow of the material.
  • Apparatus for desulfurizing pig iron in the tap spout of a blast furnace with the addition of a desulfurizing agent comprising a vessel lined with refractory material and having an inlet thereto and an outlet therefrom with the outlet spaced angularly from the inlet, the lower surface of the outlet is located in the plane of the interior lower surface of said vessel, a trough is connected at one end to said outlet from said vessel and extends outwardly therefrom, a flue positioned in said trough spaced from the outlet and having an overflow edge spaced upwardly from the lower surface of the outlet from said vessel, means for introducing desulfurizing agent into the pig iron, a stirring member positioned within said vessel between its inlet and outlet, said stirring member comprising a motor mounted on the upper portion of said vessel and arranged to rotate said stirring member about its vertical axis and to effect the mixture of the pig iron and the desulfurizing agent.
  • Apparatus for desulfurizing pig iron as set forth in claim 2 wherein the bottom surface of said inlet for pig iron is located substantially at the level of the bottom interior surface of said vessel, the upper surface of said inlet is located below the level of the overflow edge and the upper surface of the outlet is located slightly above the level of the overflow edge of said flue for the pig iron, and an opening for supplying desulfurizing agent into the vessel is located in the upper surface thereof above the level of the pig iron.
  • Apparatus for desulfurizing pig iron as set forth in claim 1, wherein the interior bottom surface of said vessel and the lower surface of the outlet form a smooth continuous surface and the interior bottom of the vessel and the lower surface of the outlet are slightly inclined downwardly in the direction from the inlet to the outlet, and the opposed surfaces of the outlet as they proceed outwardly from the interior of said vessel are in diverging relationship.
  • Apparatus for desulfurizing pig iron as set forth in claim 2, wherein the lower surface of said beam-shaped stirring part of said stirring member is positioned closely above the interior bottom surface of the vessel in the range of about 2-10 cm above the interior bottom surface.
  • Apparatus for desulfurizing pig iron as set forth in claim 2, wherein with said vessel having an inside diameter of more than 1.5 m, the length of said beamshaped stirring part is 0.35 to 0.45 times the inside diameter of said vessel.
  • Apparatus for desulfurizing pig iron as set forth in claim 2, wherein with said vessel having an inside diameter of less than 1.5 m, the length of the beamshaped stirring part is 0.45 to 0.80 times the inside diameter of said vessel.
  • Apparatus for desulfurizing pig iron as set forth in claim 1, wherein the inlet to said vessel is located on one of the axes of said vessel and said vessel is divided into a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant counting from said inlet in the direction of rotation of said stirring member, said outlet is spaced angularly from said inlet and is located in the third quadrant of said vessel, and the opening for supplying desulfurizing agent into said vessel is located in its fourth quadrant.
  • Apparatus for desulfurizing pig iron as set forth in claim 1, wherein the upper edge of said vessel is located at least 60 cm above the upper surface of the outlet therefrom.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
US69600A 1969-09-06 1970-09-04 Method of and apparatus for desulfurizing pig iron Expired - Lifetime US3687430A (en)

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Application Number Priority Date Filing Date Title
DE1945275A DE1945275C3 (de) 1969-09-06 1969-09-06 Vorrichtung zur Entschwefelung von Roheisen in der Abstrichrinne eines Hochofens und deren Verwendung

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US69600A Expired - Lifetime US3687430A (en) 1969-09-06 1970-09-04 Method of and apparatus for desulfurizing pig iron

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US (1) US3687430A (fr)
JP (1) JPS4914602B1 (fr)
BE (1) BE755733A (fr)
CA (1) CA920807A (fr)
DE (1) DE1945275C3 (fr)
FR (1) FR2060432B1 (fr)
GB (1) GB1321096A (fr)
LU (1) LU61642A1 (fr)
NL (1) NL7013078A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3915694A (en) * 1972-09-05 1975-10-28 Nippon Kokan Kk Process for desulphurization of molten pig iron
EP0116221A1 (fr) * 1982-12-21 1984-08-22 Shinko Electric Co. Ltd. Appareil et procédé pour désulfurer et chauffer des métaux fondus
EP1254734A1 (fr) * 2001-05-02 2002-11-06 Senju Metal Industry Co., Ltd. Appareil d'enlèvement de scories de brasure
CN113151624A (zh) * 2021-04-20 2021-07-23 中天钢铁集团有限公司 一种消化高硫焦的高炉冶炼方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU154998A1 (fr) *
US1590730A (en) * 1924-04-23 1926-06-29 Mathieson Alkali Works Method of desulphurizing iron
US2290961A (en) * 1939-11-15 1942-07-28 Essex Res Corp Desulphurizing apparatus
US2319402A (en) * 1941-01-18 1943-05-18 Rasex Res Corp Desulphurizing apparatus
US2677609A (en) * 1950-08-15 1954-05-04 Meehanite Metal Corp Method and apparatus for metallurgical alloy additions
US3572671A (en) * 1967-10-03 1971-03-30 Conzinc Riotinto Ltd Continuous degassing of metals

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE750404C (de) * 1940-10-01 1945-01-19 Verfahren zur Steigerung der Entschwefelungsgeschwindigkeit in fluessigen Metallbaedern
US2741556A (en) * 1952-02-05 1956-04-10 Allied Chem & Dye Corp Method of desulfurizing molten ferrous metal
NL152602B (nl) * 1968-05-09 1977-03-15 Nippon Kokan Kk Werkwijze voor het continu bereiden van staal.

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU154998A1 (fr) *
US1590730A (en) * 1924-04-23 1926-06-29 Mathieson Alkali Works Method of desulphurizing iron
US2290961A (en) * 1939-11-15 1942-07-28 Essex Res Corp Desulphurizing apparatus
US2319402A (en) * 1941-01-18 1943-05-18 Rasex Res Corp Desulphurizing apparatus
US2677609A (en) * 1950-08-15 1954-05-04 Meehanite Metal Corp Method and apparatus for metallurgical alloy additions
US3572671A (en) * 1967-10-03 1971-03-30 Conzinc Riotinto Ltd Continuous degassing of metals

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3915694A (en) * 1972-09-05 1975-10-28 Nippon Kokan Kk Process for desulphurization of molten pig iron
EP0116221A1 (fr) * 1982-12-21 1984-08-22 Shinko Electric Co. Ltd. Appareil et procédé pour désulfurer et chauffer des métaux fondus
EP1254734A1 (fr) * 2001-05-02 2002-11-06 Senju Metal Industry Co., Ltd. Appareil d'enlèvement de scories de brasure
CN113151624A (zh) * 2021-04-20 2021-07-23 中天钢铁集团有限公司 一种消化高硫焦的高炉冶炼方法
CN113151624B (zh) * 2021-04-20 2022-05-31 中天钢铁集团有限公司 一种消化高硫焦的高炉冶炼方法

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Publication number Publication date
DE1945275A1 (de) 1971-03-11
FR2060432B1 (fr) 1974-05-17
JPS4914602B1 (fr) 1974-04-09
GB1321096A (en) 1973-06-20
DE1945275B2 (de) 1973-03-22
NL7013078A (fr) 1971-03-09
LU61642A1 (fr) 1970-12-01
FR2060432A1 (fr) 1971-06-18
DE1945275C3 (de) 1974-07-11
CA920807A (en) 1973-02-13
BE755733A (fr) 1971-02-15

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