Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B3/00—General features in the manufacture of pig-iron
  • C21B3/04—Recovery of by-products, e.g. slag
  • C21B3/06—Treatment of liquid slag
  • C21B3/08—Cooling slag
• • 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
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/076—Use of slags or fluxes as treating agents
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2400/00—Treatment of slags originating from iron or steel processes
  • C21B2400/02—Physical or chemical treatment of slags
  • C21B2400/022—Methods of cooling or quenching molten slag
  • C21B2400/024—Methods of cooling or quenching molten slag with the direct use of steam or liquid coolants, e.g. water
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/04—Working-up slag
• • 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
• • 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
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies

Definitions

• the present invention relates to a method of cooling slag, and more particularly to a method of rapidly cooling slag (hereinafter, simply referred to as "molten iron pre- treatment slag") generated during preliminary treatment of molten iron, at low cost.
• molten iron pre- treatment slag a method of rapidly cooling slag generated during preliminary treatment of molten iron, at low cost.
• the cooling rate of the molten iron pre treatment slag is generally very slow.
• preliminary treatment or “preliminary process” according to the present invention refers to desulfurization treatment and the like of a molten pig iron.
• blast furnace slag is produced as by-product from a blast furnace which is used in a process for producing pig iron.
• molten iron pretreatment slag, converter slag, and electric furnace slag are respectively produced as by-products from a molten-iron pretreatment facility, a converter, and an electric furnace.
• slag is at a temperature of 1000 0 C or higher.
• slag is typically cooled at a site near the furnace prior to being transported for recovery and recycling of metal (base metal) contained therein.
• Such cooling is typically conducted using water cooling, in order to reduce the treatment area and the cooling-down period.
• the molten iron pretreatment slag is separated from molten iron and piled up at the designated site adjacent to the blast furnace, and then water-cooled. Disclosure of Invention Technical Problem
• an object of the present invention is to provide a method of completely cooling molten iron pretreatment slag to the center thereof, with a cooling rate that is equal to or higher than the cooling rate achieved with other iron-making slag.
• Another object of the present invention is to provide a method of cooling slag in the preliminary treatment of molten iron in an economical manner.
• the present invention provides a method of cooling slag in the preliminary treatment of molten iron, including applying slag in a molten phase on the molten iron pretreatment slag which is piled up, prior to water- cooling the molten iron pretreatment slag, wherein the slag in the molten phase contains 10 wt% free-CaO or less, based on the total weight, and active oxygen.
• the active oxygen may be present in the form of gaseous oxygen and/ or ferric oxide such as FeO or Fe O contained in the molten slag, and the molten slag applied on the molten iron pretreatment slag is preferably converter slag.
• the thickness to which the molten slag is applied is preferably in the range of 50-300 mm, regardless of the height to which the molten iron pretreatment slag is piled.
• the first fact is that the carbon component contained in molten iron pretreatment slag hinders the cooling of the molten iron pretreatment slag. More specifically, the carbon component in molten iron pretreatment slag is precipitated on the surface of the molten iron pretreatment slag in the course of cooling. Since the precipitated carbon has poor wettability with water, the precipitated carbon hinders the infiltration of the water into the molten iron pretreatment slag.
• the second fact is that quicklime (about 15% or more), which does not react to components such as sulfur, contained in a large amount of quicklime, which is used in the preliminary treatment of molten iron and thus remains in the slag, hinders the cooling of molten iron pretreatment slag. More specifically, the remaining quicklime (CaO) reacts to atmospheric moisture (CaO + H O ⁇ Ca(OH) ), and expands (about double), thus causing the slag to be fractured/powdered.
• the slag powder not only has small clearances therebetween but also agglomerates (forms a slurry) when water is sprinkled thereon, thus preventing water from infiltrating into the molten iron pre- treatment slag. Meanwhile, the hydration of quicklime proceeds exothermically, and the reaction heat generated in the exothermic process evaporates some of the cooling water sprinkled on the slag. The evaporation of cooling water increases the required amount of cooling water.
• the cooling water does not infiltrate into the heaped molten iron pre- treatment slag, but flows down along the surface of the slag, thereby retarding the cooling rate of the molten iron pretreatment slag.
• the required amount of cooling water is excessively increased.
• the method according to the present invention applies molten slag, in particular, converter slag (hereinafter, the slag applied on the molten iron pretreatment slag is simply referred to as "coating slag"), which contains 10 wt% or less of free-CaO, based on the total weight thereof, and essential active oxygen, on the molten iron pretreatment slag.
• molten slag in particular, converter slag
• coating slag which contains 10 wt% or less of free-CaO, based on the total weight thereof, and essential active oxygen
• the coating slag contains free-CaO in an amount greater than 10 wt%, or the coating slag is in a solid phase rather than in a molten phase, the effect of promoting the cooling of molten iron pretreatment slag is negligible.
• the coating slag is not in the molten phase, the slag, which is powdered by the hydration of quicklime, is not sufficiently removed from the surface of the molten iron pretreatment slag, and, if the coating slag contains free-CaO in an amount greater than 10 wt%, the function of the coating slag, that of hindering the molten iron pretreatment slag from being powdered, is decreased or lost.
• the slag applied on molten iron pretreatment slag forms a porous structure, which will be described below, thus enabling cooling water to easily infiltrate into the molten iron pretreatment slag.
• the slag which is most suitable for satisfying the conditions of the coating slag, is converter slag, which is concomitantly generated in the course of operation of a converter.
• the converter slag contains oxygen in an amount of 1 wt% or more, and free-CaO is present in an amount of 5 wt% or less, based on the weight of slag.
• the thickness of the coating slag which is applied on the molten iron pretreatment slag, must be in the range of 50-300 mm. If the thickness of the coating slag is less than the above range, the effect of eliminating oxygen is negligible, thus precluding the realization of a porous surface. Meanwhile, if the thickness of the coating slag is greater than the above range, air bubbles cannot escape to the outside, but are trapped in the coating slag layer, thus precluding the realization of a porous coating slag layer.
• the height to which the molten iron pretreatment slag, on which slag is applied, is piled does not play an important role. Regardless of whether or not the height to which the molten iron pretreatment slag is piled is high, where molten iron pretreatment slag is treated on the surface thereof with the coating slag according to the present invention, cooling water can quickly infiltrate into the molten iron pretreatment slag.
• Table 1 below shows representative results of time periods for which it is required to cool molten iron pretreatment slag to a temperature of 100 0 C after the molten iron pretreatment slag is applied with coating slags having the above three different conditions to a thickness of 250 mm.
• the coating slag used in Comparative Examples was dephosphorized slag and cast slag, and the coating slags used in Examples were converter slags.
• Example 1 shows a result obtained by cooling molten iron pretreatment slag by directly sprinkling water without the use of coating slag.
• Free-CaO in the coating slag when present in an amount of 10 wt% or less, effectively cooled molten iron pretreatment slag (the cooling time was shortened by about 50%), and free-CaO in the coating slag, when present in an amount of 5 wt% or less, even more effectively cooled molten iron pretreatment slag.
• free-CaO was present in an amount greater than 10 wt%, although the cooling time was somewhat shortened, a considerably long cooling time of 20 hours of more was still required.
• the slag having the condition of Comparative Example 1 in Table 1, that is, converter slag containing free-CaO of 5-10 wt% and oxygen of 1 wt% or more was applied on molten iron pretreatment slag, and was then sprinkled with water. At this point, the time period required to cool the molten iron pretreatment slag to 100 0 C was measured. Thereafter, the cooling time was measured while varying the coating thickness of the converter slag and the heaping height of the molten iron pretreatment slag.
• Table 2 The exemplary results are given in Table 2 below.
• the present invention can be applied to iron-making factories.
• the present invention can cool slag generated during the preliminary treatment of molten iron at a cooling rate higher than that of the conventional method, the present invention contributes to cost reduction in an iron-making processes.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Carbon Steel Or Casting Steel Manufacturing (AREA)
• Furnace Details (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 2006
  • 2006-06-15 KR KR20060053747A patent/KR100775503B1/ko active IP Right Grant
• 2007
  • 2007-06-15 JP JP2009515308A patent/JP4865858B2/ja not_active Expired - Fee Related
  • 2007-06-15 CN CN2007800220141A patent/CN101466850B/zh not_active Expired - Fee Related
  • 2007-06-15 WO PCT/KR2007/002905 patent/WO2007145481A1/en active Application Filing

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