US3647417A - Process for producing sponge iron - Google Patents

Process for producing sponge iron Download PDF

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Publication number
US3647417A
US3647417A US855278A US3647417DA US3647417A US 3647417 A US3647417 A US 3647417A US 855278 A US855278 A US 855278A US 3647417D A US3647417D A US 3647417DA US 3647417 A US3647417 A US 3647417A
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Prior art keywords
brown coal
sponge iron
sintering
sinter
kiln
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US855278A
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English (en)
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Rolf Emil Wetzel
Willi Janssen
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Fried Krupp AG
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Fried Krupp AG
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/08—Making spongy iron or liquid steel, by direct processes in rotary furnaces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
    • Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention relates to a process for producing sponge iron using sintered ore as the material charged to the reducing apparatus.
  • sponge iron includes the direct reduction of iron ores which have been mixed with reducing agent. In the case of ores containing fine particles, it is often required that the fine particles be brought together into lumps, before charging the reducing apparatus, in order to obtain sponge iron in lump form.
  • the fine ore In the case of pelletizing, the fine ore must be ground in ball or rod mills and then formed into pellets. The pellets must then be burned.
  • Sintering is effected by a burning of solid fuel previously mixed with the fine ore.
  • the energy costs are essentially determined by the amount of solid fuel mixed.
  • An object of the invention is to reduce the cost of the sintering method of lumping fine iron ores for the charging of reducing apparatus for forming sponge iron and to consequently make the sintering method a better alternative for the pelletizing method, especially where the cost of grinding and forming fine ore into pellets, followed by burning, is especially high.
  • the undesired fines from a sponge iron producing, reducing apparatus are fed back and mixed with the fine ore before sintering.
  • Such sponge iron fines have provided difiiculty for the further treatment of sponge iron coming from a reducing apparatus and it has been necessary to agglomerate them in order to be able to feed them on with the larger sponge iron particles.
  • the strength properties of the sintered material obtained using sponge iron of minus 3 millimeter particle size is not appreciably altered from that obtained using mixes containing only the solid carbonaceous fuel of the prior art.
  • the amount x of solid fuel that can be replaced is given by the following formula:
  • FIG. 1 is a flow diagram of the invention.
  • FIG. 2 is a modification of a part of the flow diagram of FIG.
  • a sinter mix is prepared from iron ore, sponge iron, and some water to provide some green strength to the mix and to maintain porosity in the sinter bed.
  • To this mix may be added auxiliary components, sinter fines separated from the mate rial charged to a reducing apparatus, and a solid fuel such as coke fines or coal dust, should the amount of sponge iron be insufficient to provide the total heat required for the sintering.
  • iron ore is meant to include materials such as the iron oxides resulting from the oxygen torch cutting of steels, etc.
  • a preferred amount of sponge iron for the sinter mix has been determined to be from 5 to 25 weight percent.
  • the lower limit results in a complete utilization of the minimum amount of minus 3 millimeter sponge iron that can be found to occur in a process such as that of Example I below.
  • the upper limit is the maximum amount of minus 3 millimeter sponge iron that can be required in a process such as that of Example II, where no solid carbonaceous fuel is used.
  • the sinter mix is loaded onto a moving conveyor and sintered in the same manner practiced in the prior art for sinter mixes containing only solid carbonaceous fuel.
  • the resulting sinter cake is crushed in a roll crusher and this crushed product is fed while still hot to a size-separating device such as a grizzly, whereupon the undersize is fed back to the mixer for the sinter mix.
  • the oversize is mixed with solid fuel and desulfurizing material and then put in a rotary kiln for reduction. Examples of such desulfurizing material are raw dolomite and limestone.
  • the sponge iron issuing from the rotary kiln is subjected to a size separation operation by screening to remove the fraction under 3 millimeters. This minus fraction is fed back to the sinter mixer.
  • the oversize sponge iron is treated further as desired, for example in an arc furnace.
  • brown coal is meant to include equivalents of brown coal with regard to volatile component content. Any carbonized brown coal remaining following the reduction can be fed right along with the minus 3 millimeter sponge iron back to the sinter mixer, if the rate of minus 3 millimeter sponge iron production should be insufficient to provide the required amount of heat for the sintering operation.
  • the undersize mixture of sponge iron and carbonized brown coal can be separated by a magnetic separator operation. In a preferred modification, the undersized fraction is not separated in a magnetic separating operation, while the oversize is separated in such manner, the oversize carbonized brown coal being mixed into the kiln charge and the oversize sponge iron being fed on for further processing.
  • FIG. 1 shows a tube drier operated by the hot gas exhaust of the kiln.
  • the brown coal is dried and preheated in this tube drier before being fed to the mixer to be mixed with the oversize sintered iron ore to form the kiln charge.
  • Use of the tube drier improves the heat economy of the entire process.
  • FIG. 2 shows a modification of the flow diagram of FIG. I. Only a sufficient amount of the unchanged part of FIG. 1 has been redrawn to indicate the setting of the modification.
  • a low-temperature coking apparatus is used to first produce carbonized brown coal from the raw brown coal.
  • the coking apparatus is driven by the hot exhaust gases of the kiln.
  • the gases given off by the raw brown coal are used to heat the kiln and to operate the sinter bed igniter.
  • the carbonized brown coal is fed while still hot to the kiln charge mixer.
  • This modification allows better utilization of the available energy in the brown coal.
  • a sinter mix was prepared with 20 percent sinter fines, 8 percent water, 3 percent coke dust, 10 percent sponge iron fines, remainder Kiruna ore. This mix was charged on a conveyor as shown in FIG. 1 and ignited to produce sintering. The sinter cake was subjected to the Micum drum test, which gave the minus 10 millimeter particle size as 23.5 percent. Thus, a sufficient sinter strength is obtained. Reduction of this sintered material in a rotary kiln gave a sponge iron having a total iron content of 75.5 percent and a zero-valent iron content of 69.3 percent. Dividing 69.3 by 75.5, it is seen that a metallizing efficiency of 92 percent is achieved. The sponge iron minus 3 millimeter fraction amounted to 7.8 percent, while the amount below millimeters was 14.8 percent.
  • Kiruna ore is a magnetic ore, whose essential mineralogical component is magnetite, Fe O
  • the chemical analysis of Kiruna ore is given in Table 1. its ignition loss is 1.0 percent.
  • the sieve analyses for the coke dust, sponge iron fines, and Kiruna ore are given in Table 2. The sinter fines were minus 3 millimeter material. The coke dust had 87 percent fixed carbon.
  • the drum was then rotated for 1 minute.
  • the drum contents were then sieved in a stack of sieves to determine the percentage having a particle size below 10 millimeters.
  • the amount of minus 10 millimeter product can be viewed as a measure of the strength of the sintering. The more minus 10 millimeter material produced, the lower the sinter strength.
  • the kiln for the reduction measured 14 meters in length and had an internal diameter of 1.2 meters.
  • the sieve analysis of the crushed sinter cake charged to this kiln is given in Table 3.
  • This sinter product was fed to the kiln at the rate of 400 kilograms per hour.
  • the requisite brown coal, lower heating value H 4600 kilocalories per kilogram sieve analysis in Table 2, was charged with the sinter product into the kiln at the rate of 200 kilograms per hour.
  • More brown coal was blown burning into the kiln by means of an injector at the rate of kilograms per hour, at the sponge iron output side of the kiln. No other fuel was needed, the total brown coal serving both as reducing agent and as fuel.
  • the temperature at the sponge iron output side of the kiln was l,l00 C., while the exhaust gases left the kiln at the sinter product charging side at 870 C.
  • EXAMPLE ll A sinter mix was prepared with 20 percent sinter fines, 8 water, 20 percent sponge iron fines, remainder Kirma ore. This example represents a complete replacement of carbonaceous fuel by sponge iron. This mix was charged on a conveyor as shown in FIG. 1 and ignited to produce sintering. The minus 10 millimeter fraction in the Micum drum test was 27 percent. Reduction gave a sponge iron with a total iron content of 77.2 percent and a zero-valent iron content of 7 l .9 percent corresponding to a metallizing efficiency of 93.1 percent. The sponge iron fraction below 3 millimeters amounted to 8.3 percent and that below 5 millimeters was l6.l percent. The process variables were otherwise those in Example I.
  • Example I the product at the sponge iron output side of the kiln had 45 percent carbonized brown coal in the minus 3 millimeter fraction.
  • the analysis of the brown coal as charged into the kiln was as given in Table 4.
  • the minus 3 millimeter mixture of iron and carbonized brown coal was used to replace the sponge iron fines of the sinter mix of Example I.
  • Example rv The 3 percent coke dust of Example I was replaced by a 5 percent amount of carbonized brown coal with 52 percent fixed carbon.
  • the sponge iron product from the kiln was first screened as in Example III to remove material of below 3 millimeter particle size.
  • the product of over 3 millimeter particle size was then magnetically separated and the carbonized brown coal of over 3 millimeter particle size was used for mixing with the sinter product in replacement of part of the brown coal used for mixing with the sinter product in Example I when charging the kiln.
  • the carbonized brown coal in the plus 3 mm. fraction amounted to 8 percent.
  • Example I a low temperature coking apparatus in the form of a circulating gas retort made by the firm Lurgi is used for the drying and coking of brown coal in two stages.
  • the hot exhaust gases of the kiln are fed into the coking stage at a temperature of about 800 C.
  • the resulting coking exhaust gases which have a heating value of 1,500 kilocalories per standard cubic meter, are partially used for the drying stage of the retort.
  • Another part is used as fuel in replacement of the injected coal for the kiln at the rate of 400 standard cubic meters per hour to maintain a working temperature of l,l50 C.
  • Another part is used for igniting the sinter mix on the conveyor system.
  • Operation at the kiln differs additionally in that the 200 kilograms per hour reduction coal is replaced by 250 kilograms per hour carbonized brown coal from the retort.
  • This carbonized brown coal has a sieve analysis as given in Table 5.
  • the temperature and pressure for the above mentioned standard cubic meter of gas are Celsius and 760 mm.
  • step of changing including the step of mixing brown coal with the product of the step of sintering, the steps of separating and using incorporating the resulting carbonized brown coal minus 3 millimeter size fraction.
  • step of changing including the step of mixing brown coal with the product of the step of sintering, the step of changing including a reduction step in a rotary kiln, the process further comprising the step of preheating and drying the brown coal, before mixing it with the product of the step of sintering, using the hot gas exhaust of the rotary kiln.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Powder Metallurgy (AREA)
US855278A 1968-09-07 1969-09-04 Process for producing sponge iron Expired - Lifetime US3647417A (en)

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Application Number Priority Date Filing Date Title
DE1758951A DE1758951C3 (de) 1968-09-07 1968-09-07 Verfahren zur Herstellung von Eisenschwamm

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DE (1) DE1758951C3 (es)
ES (1) ES371092A1 (es)
FR (1) FR2017565A1 (es)
SE (1) SE348761B (es)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888657A (en) * 1970-12-30 1975-06-10 Scm Corp Process for production of metal powders having high green strength
US4050924A (en) * 1975-06-03 1977-09-27 Dravo Corporation Process of controlling Fe++ content of sintered iron ore
US5520719A (en) * 1992-08-31 1996-05-28 Nippon Steel Corporation Process for producing sintered iron ore product
US5630202A (en) * 1993-09-30 1997-05-13 Maschinenfabrik Koppern Gmbh & Co. Kg Method for making sponge iron briquettes from fine ore
US6248152B1 (en) * 1997-09-30 2001-06-19 Kawasaki Steel Corporation Method of reducing iron oxide on a movable hearth furnace
US20060123952A1 (en) * 2002-10-15 2006-06-15 The Australian Steel Company(Operations) Pty Ltd. Process and apparatus for extracting zinc

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3306614A1 (de) * 1983-02-25 1984-08-30 Metallgesellschaft Ag, 6000 Frankfurt Verfahren zur direktreduktion von gesintertem eisenoxidhaltigem material zu eisenschwamm in einem drehrohrofen

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1864593A (en) * 1929-05-15 1932-06-28 Gustafsson Emil Gustaf Torvald Method of producing metal sponge
US2826487A (en) * 1955-07-07 1958-03-11 United States Steel Corp Method of sintering ore fines
US3428445A (en) * 1965-07-22 1969-02-18 Metallgesellschaft Ag Iron ore reduction
US3489549A (en) * 1965-12-29 1970-01-13 Fuji Iron & Steel Co Ltd Sintering material from iron-containing dry dust and preparing method thereof
US3497348A (en) * 1965-06-25 1970-02-24 Metallgesellschaft Ag Sponge iron production

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1864593A (en) * 1929-05-15 1932-06-28 Gustafsson Emil Gustaf Torvald Method of producing metal sponge
US2826487A (en) * 1955-07-07 1958-03-11 United States Steel Corp Method of sintering ore fines
US3497348A (en) * 1965-06-25 1970-02-24 Metallgesellschaft Ag Sponge iron production
US3428445A (en) * 1965-07-22 1969-02-18 Metallgesellschaft Ag Iron ore reduction
US3489549A (en) * 1965-12-29 1970-01-13 Fuji Iron & Steel Co Ltd Sintering material from iron-containing dry dust and preparing method thereof

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888657A (en) * 1970-12-30 1975-06-10 Scm Corp Process for production of metal powders having high green strength
US4050924A (en) * 1975-06-03 1977-09-27 Dravo Corporation Process of controlling Fe++ content of sintered iron ore
US5520719A (en) * 1992-08-31 1996-05-28 Nippon Steel Corporation Process for producing sintered iron ore product
US5630202A (en) * 1993-09-30 1997-05-13 Maschinenfabrik Koppern Gmbh & Co. Kg Method for making sponge iron briquettes from fine ore
US6248152B1 (en) * 1997-09-30 2001-06-19 Kawasaki Steel Corporation Method of reducing iron oxide on a movable hearth furnace
US20060123952A1 (en) * 2002-10-15 2006-06-15 The Australian Steel Company(Operations) Pty Ltd. Process and apparatus for extracting zinc
US7790099B2 (en) * 2002-10-15 2010-09-07 David Wilson Investments Pty. Ltd. Process and apparatus for extracting zinc

Also Published As

Publication number Publication date
FR2017565A1 (es) 1970-05-22
SE348761B (es) 1972-09-11
DE1758951A1 (de) 1971-04-01
ES371092A1 (es) 1971-08-01
DE1758951C3 (de) 1978-04-27
DE1758951B2 (de) 1977-09-08

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