Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B3/00—General features in the manufacture of pig-iron
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/008—Composition or distribution of the charge
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B11/00—Making pig-iron other than in blast 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
  • Y02P10/20—Recycling

Definitions

• the present invention relates to a process for the recovery of iron/steel from scrap mill scales and fines, and more particularly to the refining and cooling of molten steel with mill scale particles recovered from downstream operations of a steel manufacturing process.
• Steel is produced by refining hot metal from a blast furnace. After molten steel has been refined, it is solidified and then subjected to successive rolling operations during which the steel may be successively heated and cooled. During the successive heating and cooling of steel, or during storage between various rolling operations, surface of the steel oxidizes to form mill scale. This mill scale flakes off during handling and rolling of the steel.
• Mill scales include base metal chips, platelets and other fines, which are essentially oxides of iron. Such oxides are primarily composed of ferrous/ferric iron (Fe 3 0 4 ) surrounding a core of the iron base material.
• ferrous/ferric iron Fe 3 0 4
• mill scale is a prime candidate for recycling in steel making or blast furnace operations because mill scale is a relatively coarse, dense, waste oxide material of relatively high iron content and low in impurities such as alumina or silica.
• fines are generated from both the manufacture and the use of Direct Reduced Iron (DRI) pellets. DRI pellets are a primary material used by electric arc furnaces in the making of steel and a secondary material used by blast furnaces and cupolas. Many of the pellets are crushed during transportation to mill sites from production plants and during normal charging operations.
• DRI pellets are a primary material used by electric arc furnaces in the making of steel and a secondary material used by blast furnaces and cupolas. Many of the pellets are crushed during transportation
• the present invention relates to a process for enhancing the efficiency of iron/steel reclamation from mill scales and fines. It is an object of the present invention to recover base metal iron/steel from mill scale platelets and fines.
• the process uses byproducts of iron and steel melting operations, such as coke and fines, to effect iron/steel recovery.
• the recovery process in accordance with an embodiment of the present invention is performed integral to cupola or blast furnace operations, and the recovered metal is collected at the base of the furnace as molten iron/steel.
• a process in accordance with an embodiment of the present invention improves energy utilization of recovery operations by taking advantage of the inherent solubility of carbon in iron and other associated
• a process in accordance with an embodiment of the present invention generates additional heat energy when coke constituents in a feed mixture ignite and burn using oxygen released from the iron/steel mill scale components.
• the process in accordance with an embodiment of the present invention also improves molten base metal output from earlier melting of mill scale constituents at the upper levels of a blast furnace.
• Figure 1 illustrates an exemplary container used in the process for recovering iron/steel from scrap mill scales and fines in accordance with an embodiment of the present invention.
• the present invention relates to a process for recovering iron/steel from scrap mill scales and fines.
• the process includes the step of mixing of components, such as iron/steel chips, platelets and fines, with coke or other carbon containing fines to ensure maximum surface contact of all components.
• components are mixed with coke comprising from about 50% carbon to about 99% carbon.
• components are mixed with coke comprising about 92% carbon.
• the quantity of coke mixed with the components must be sufficient to ensure maximum contact with the surfaces of iron/steel component.
• ratio of carbon to mill scale is about one carbon to about eight mill scale.
• Variance of millscale can go higher depending on iron content of mill scale.
• ratio of DRI fines to carbon is about one carbon to about twenty five DRI fines.
• variance of DRI can go higher.
• the coke plays a central role in the recovery process because of the interaction between the carbon present in the coke with oxygen and iron atoms.
• the carbon monoxide reduces iron oxide (Fe 2 Os) to molten iron, and transforms to carbon dioxide in the process:
• Excess carbon dissolves in the elemental iron to form delta and austenitic phases of the iron/carbon alloy system.
• an addition of 4.3% carbon lowers the melting point of the liquid/solid iron/carbon mixture from about 2780° C to about 2090° C.
• the austenite phase is derived from the peritectic reaction of delta ferrite and molten iron-carbon solution.
• austenite undergoes a eutectoid reaction, which at room temperature produces a variety of useful steel structures.
• Higher carbon contents of the iron/carbon alloy system increases the melting point of the system and results in formation of cementite (FesC).
• FesC cementite
• Such increase in the melting point is undesirable for an economical recovery of iron/steel from mill scales and fines.
• additional heat energy can be derived from the ignition and burning of coke as appropriate furnace temperatures are attained. Molten iron/steel is produced in the upper levels of the furnace, thereby permitting frequent loading of recoverable scrap/coke mix and a resultant increase in production output.
• mill scales components are mixed with coke or other carbon containing fines to form a mixture.
• the mixture provides all components with maximum contact surface necessary for efficient reaction.
• the mixture is poured into a container and sealed.
• an exemplary container, generally designated 100 used in the process for recovering iron/steel from scrap mill scales and fines in accordance with an embodiment of the present invention.
• container 100 of Figure 1 a container body 102 is provided with a side wall 104 leading to a body end 106 which is covered, in the depicted embodiment, with a ring 106.
• Ring 106 forms a flange over body end such that a cross section shaped as an inverted "U" defines a container rim 108. Ring 106 extends inward from container rim 108 to form a ring edge 110. Diameter of ring edge 110 is smaller than the diameter of container rim 108 such that it forms a concentric ring edge 110 from container rim 110. Ring 106 forms a curl depression 112 having a U-shaped cross-section as it extends inward from container rim 108. Ring edge 110 curls inward to form a ring lip 114.
• container plug 116 generally extending laterally across the container opening up to container rim 110 such that it resembles a disc covering the container opening. Viewing from the center towards the edge, container plug 116 forms a series of alternating depressions and ridges. First, container plug 116 forms a curl depression 118 having a shallow U-shaped cross-section. Immediately following curl depression 118, container plug 116 forms a ridge 120 having an inverted U- shaped cross section. Following ridge 120, container plug 116 forms a second curl depression 122 having a U-shaped cross-section. The edge following curl depression 122 curls outward to form plug lip 124.
• container plug 116 When container plug 116 is placed over the container opening, container plug 116 covers the entire container opening and curl depression 122 contacts the inner surface of curl depression 112 such that curl depression 122 forms a tight fit with curl depression 112.
• the tight fit between curl depression 122 and curl depression 112 provides a gas-tight seal between container body 102 and container plug 116.
• 0.33g of tin solder paste is placed in the curl depression prior to placement of the container plug to ensure a gas tight seal.
• Post closure the mini-furnace is placed such that a heat induction system can heat the top 1/16 inch of the mini-furnace to 550 degrees F in 4.5 seconds. The tin solder flows through the curl depression and upon cooling assures a tight and very secure seal.
• Container 100 is made from a material having a composition that is compatible with the core components of the mill scales.
• container 100 is a flat rolled steel can having a composition of about 0.15% by weight.
• Container 100 wall is of sufficient thickness so as to withstand the weight of mill scales, fines and coke.
• the container wall is of sufficient thickness so as to withstand high pressures from gases generated with the container.
• container 100 wall thickness is from about 0.12 inches to about 0.015 inches.
• the internal surface of container 100 is coated with a material that assists in sealing container 100 and enhances the mill scale conversion reaction.
• the material used for coating the internal surface of container 100 has low melting point, attaches or bonds to the internal surface of container 100, is ductile, and resistant to corrosion from oils present in contaminants in the mill scales and coke.
• Container 100 internal surface coating material combines with sulfur, phosphorous, silicon and other contaminants present in the mill scales and coke to form compounds that minimize the dissolution of the contaminants in the recovered molten iron/steel.
• the contaminants combine with coating material to form compounds or eutectics that limit the solubility of the contaminants in molten iron/steel.
• the resulting slag segregates from the molten iron/steel, and the coating material can be recovered from the slag.
• Exemplary materials that can be used to coat the internal surface of container 100 include tin, zinc, aluminum, and the like. In some embodiments of the present invention, internal surface of container 100 is coated with tin having a thickness of from about 0.00003 inches to about 0.0001 inches.
• Container 100 capacity is chosen such that it facilitates melting and recovery of mill scale base metal.
• containers of smaller size are useful in furnaces having a fixed opening.
• Containers of smaller capacity are also useful for controlling the quantity of mill scale fed into the furnace without disrupting furnace operating conditions.
• Containers of smaller capacity minimize production losses resulting from damages to a container.
• the volume of container 100 is from about 0.01 gallons to about 1.5 gallons. In another embodiment of the present invention, the volume of container 100 is from about 0.01 gallons to about 1 gallon.
• Container 100 include a plurality of vents to release carbon monoxide and/or carbon dioxide gases generated by reactions between components within container 100.
• vents are located on the top surface of container 100.
• the diameters of the vents are about 0.1875 inches.
• vents are located along the sides of container 100.
• containers 100 are fed into the furnace from the top of a furnace.
• Containers 100 comprising the mill scale-coke mixture are brought to the top of the furnace along with raw mateirals via a mechanical device, such as a crane, a skip car powered by winches or conveyor belts, and the like.
• Containers 100 are charged into the furnace in a manner similar to charging raw materials into the furnace.
• containers 100 can be used in blast furnaces having a double bell system, where two bells are used to control the entry of raw material into the blast furnace.
• container 100 In such blast furnaces, containers 100 are placed into the upper or small bell. The small bell is then rotated to position container 100 more accurately, and then opens to drop container 100 into the large bell. The small bell then closes, to seal the blast furnace, while the large bell dispenses container 100 into the blast furnace.
• container 100 can be used in blast furnaces having a bell-less system, where multiple hoppers containing multiple containers are discharged into the blast furnace through valves.
• a chute can also be implemented in order to precisely control where container 100 is placed.
• container 100 As container 100 travel towards the bottom of the furnace, its contents and the pallet are consumed. Elevated temperatures existing at the upper levels of furnaces and additional heat obtained from furnace operations permit the contents of container 100 to react and form molten metal while containers 100 are still at the upper levels of the furnaces. Charge levels are monitored using instruments which determine whether a flat surface is reestablished at the bottom. Once a reasonably flat surface is reestablished at the bottom, additional containers can be charged into the furnace. In one embodiment of the present invention, additional containers can be charged into a cupola at one hour intervals. In another embodiment of the present invention, additional containers can be charged into a blast furnace at every 12 hour intervals.
• molten iron/steel at the upper levels of the furnace permit frequent loading of recoverable scrap/coke mix and a resultant increase in production output.
• Molten metal collects at the base of the furnace and withdrawn into ladles.
• the molten metal in ladles are then transferred for downstream processing.
• the ladles contents are poured into ingots or other product molds, allowed to solidify and prepared for processing into desired configurations.

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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)

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Publications (1)

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Citations (4)

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• 2013
  • 2013-03-14 CA CA 2869553 patent/CA2869553A1/fr not_active Abandoned
  • 2013-03-14 EP EP13772913.3A patent/EP2834380A4/fr not_active Withdrawn
  • 2013-03-14 WO PCT/US2013/031189 patent/WO2013151711A1/fr not_active Ceased
  • 2013-03-14 MX MX2014012005A patent/MX2014012005A/es unknown
• 2014
  • 2014-10-03 US US14/505,773 patent/US20150013497A1/en not_active Abandoned

Patent Citations (4)

Non-Patent Citations (1)

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