EP3253896A1 - Method and arrangement to prepare chromite concentrate for pelletizing and sintering and pelletizing feed - Google Patents

Method and arrangement to prepare chromite concentrate for pelletizing and sintering and pelletizing feed

Info

Publication number
EP3253896A1
EP3253896A1 EP16704030.2A EP16704030A EP3253896A1 EP 3253896 A1 EP3253896 A1 EP 3253896A1 EP 16704030 A EP16704030 A EP 16704030A EP 3253896 A1 EP3253896 A1 EP 3253896A1
Authority
EP
European Patent Office
Prior art keywords
feed
pelletizing
fluxing agent
arrangement
slag
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16704030.2A
Other languages
German (de)
French (fr)
Inventor
Helge Krogerus
Pasi MÄKELÄ
Jarmo Saarenmaa
Sauli PISILÄ
Petri PALOVAARA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Outotec Finland Oy
Original Assignee
Outotec Finland Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Outotec Finland Oy filed Critical Outotec Finland Oy
Publication of EP3253896A1 publication Critical patent/EP3253896A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
    • 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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5264—Manufacture of alloyed steels including ferro-alloys
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • 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
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/242—Binding; Briquetting ; Granulating with binders
    • C22B1/244—Binding; Briquetting ; Granulating with binders organic
    • C22B1/245—Binding; Briquetting ; Granulating with binders organic with carbonaceous material for the production of coked agglomerates
    • 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
    • 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
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/10—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agents
    • C22B9/103—Methods of introduction of solid or liquid refining or fluxing agents
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • 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 invention relates to a method to prepare chromite concentrate for pelletizing and sintering as defined in the preamble of independent claim 1.
  • the invention also relates to an arrangement to prepare chromite concentrate for pelletizing and sintering as defined in the preamble of independent claim 6.
  • the invention also relates to a pelletizing feed as defined in the preamble of independent claim 13.
  • Publication WO 2013/071955 presents a process for the manufacture of ferrochrome alloy comprising the steps of providing a pelletizing feed, wherein the pelletizing feed comprises chromite concentrate and silicon carbide as the only carbonaceous material and the only reducing agent; pelletizing the pelletizing feed to obtain pellets; sintering the pellets to obtain sintered pellets; mixing the sintered pellets with external reducing agent to obtain smelting feed; and smelting the smelting feed.
  • Publication WO 2013/071955 presents a pelletizing feed containing chromite ore, at least one nickel salt, and silicon carbide as the only carbonaceous material and the only reducing agent.
  • the invention also relates to process for manufacturing the pelletizing feed comprising the steps providing chromite, at least one nickel salt and silicon carbide, and mixing chromite, at least one nickel salt and silicon carbide.
  • the invention also relates to use of the pelletizing feed as a starting material for the manufacture of sintering feed.
  • the invention also relates to a sintering feed in the form of pellets containing the pelletizing feed.
  • the invention also relates to sintered pellets containing the sintering feed.
  • the invention also relates to process for manufacturing the sintered pellets.
  • the invention also relates to use of the sintered pellets as a component of smelting feed.
  • the invention also relates to smelting feed comprising sintered pellets.
  • the invention also relates to process for manufacturing ferrochrome alloy.
  • the invention also relates to ferrochrome alloy obtainable by the method.
  • the pelletizing feed from which the sintered pellets are made, may comprise fluxing agents, such as limestone, dolomite, quarts, calcite or wollastonite and any mixture thereof.
  • fluxing agents such as limestone, dolomite, quarts, calcite or wollastonite and any mixture thereof.
  • a reason for adding fluxing agent to the pelletizing feed is to achieve sufficient compressive strength of the sintered pellets which are produced in the subsequent sintering process by using the pelletizing feed.
  • a sufficient compressive strength Fi2mm is typically between 180 and 220 kg.
  • a disadvantage by using the fluxing agents mentioned in publication WO 2013/071955 and in publication WO 2013/071955, limestone, dolomite, quarts, calcite or wollastonite and any mixture thereof, is that these are relatively expensive.
  • Publication US 3,825,638 presents a method for producing cold bound agglomerates from particulate iron oxide containing mineral concentrates using a steam liardenable binder.
  • the binder is ground down together with iron oxide material at a high energy input to produce a fine grain additive material.
  • the additive material is then mixed with the mineral concentrates and agglomerates are formed from the mixture and steam hardened.
  • Publication WO 2015/003669 relates to fluxing agents for the agglomeration process based on slag from the secondary metallurgy, the use of these fluxing agents in the process of agglomeration in the manufacture of the agglomerate designed for the use as a metallic charge in blast furnaces and a process of production of fluxing agents based on slag from the secondary metallurgy or based on a mixture of slag from the secondary metallurgy with other materials.
  • An object of the invention is to provide a method and an arrangement to prepare chromite ore for pelletizing and sintering and correspondingly to provide a pelletizing feed by means of which a pelletizing feed, containing fluxing agent for obtaining sufficient strength of the sintered pellets which are produced in the subsequent sintering process by using the pelletizing feed, can be obtained by using less expensive raw material.
  • the invention relates also to the use of the method according to any of the claims 1 to 5 in a process for producing ferrochrome alloy from chromite concentrate.
  • the invention relates also to the use of the arrangement according to any of the claims 6 to 10 in an arrangement for producing ferrochrome alloy from chromite concentrate.
  • the pelletizing feed is correspondingly characterized by the definitions of independent claim 13.
  • the invention relates also to sintered pellets as defined in claim 18 containing the pelletizing feed according to any of the claims 13 to 17.
  • the invention relates also to the in claim 19 defined use of the sintered pellets according to claim 18 as a component of smelting feed.
  • the invention relates also to a smelting feed as defined in claim 20 containing the sintered pellets according to claim 18.
  • the invention relates also to a process as defined in claim 21 for manufacturing ferrochrome alloy comprising the step of smelting the smelting feed according to claim 20.
  • the invention relates also to ferrochrome alloy as defined in claim 22 and obtainable by the process according to claim 21.
  • the invention is based on that the fluxing agent that is used is at least partly slag originating from processing of ferrous metal.
  • the compressive strength of the sintered pellets Fi2mm can be calculated according to the following formula:
  • Figure 1 is a schematic flow chart of a first embodiment of equipment containing an arrangement according to an embodiment of the invention
  • Figure 2 is a schematic flow chart of a second embodiment of equipment containing an arrangement according to an embodiment of the invention
  • Figure 3 is a schematic flow chart of a third embodiment of equipment containing an arrangement according to an embodiment of the invention.
  • Figure 4 is a schematic flow chart of a fourth embodiment of equipment containing an arrangement according to an embodiment of the invention.
  • Chromite is the ore which is excavated from the chromite deposit.
  • the chromite concentrate is the product of the beneficiation plant.
  • the ganque components are mainly separated to the wastes for improving the grade of chromite for the pelletizing and sintering.
  • the method comprises a providing step for providing a chromite concentrate feed 1 and an adding step for adding at least fluxing agent 2 to the chromite concentrate feed 1 to obtain a pelletizing feed 12.
  • a purpose of the fluxing agent 2 is to lower the melting point of the slag forming components in the pelletizing feed 12 and to provide more slag forming components to the pelletizing feed 12.
  • Another purpose of the fluxing agent is to during a sintering process, where pellets previously formed of the pelletizing feed 12 is sintered into sintered pellets, to provide more connections and connections of better quality in the sintered pellets by melting and subsequently solidifying the binding silicates in the fluxing agent 2.
  • the method may include a fine-dividing step for fine-dividing the chromite concentrate feed 1 to a particle size distribution of 70 to 90 % below 74 ⁇ , preferably 80+2% below 74 ⁇ , and more preferably about 80% below 74 ⁇ for example in a mill 3.
  • fluxing agent 2 in the form of slag 4 originating from processing of ferrous metal is added to the chromite concentrate feed 1.
  • the particle size distribution of the fluxing agent 2 may be 80 to 100%, preferably 100 % below 74 ⁇ (200 mesh).
  • the method may include a fine-dividing step for fine-dividing the slag 4 prior the adding step for example by milling in a mill 3.
  • the chromite concentrate feed 1 additionally at least one of the following may be added to the chromite concentrate feed 1: (i) carbonaceous material 6 such as coke, (ii) dust 7, and (iii) binding agent 8 such as bentonite for example sodium- activated calcium betonite, water-based binding agent, and/or organic binding agent.
  • carbonaceous material 6 such as coke
  • dust 7 and binding agent 8 such as bentonite for example sodium- activated calcium betonite, water-based binding agent, and/or organic binding agent.
  • binding agent 8 such as bentonite for example sodium- activated calcium betonite, water-based binding agent, and/or organic binding agent.
  • the purpose of the possible binding agent 8 is give the pellets, which are produced from the pelletizing feed 12, enough dry- and wet strength so that the pellets can firstly withstand transportation from a means for forming pellets such as from a pelletizing drum or disc 16 to a sintering means such as to a steel belt sintering furnace 19, where the pellets are strengthened by performing sintering to produced sintered pellets and secondly withstand drying, heating, sintering in the sintering means until a desired strengthening by sintering is achieved.
  • the strengthening effect of the binding agent in the resulting sintered pellets is quite marginal in comparison to the strengthening effect resulting from fluxing agent and gangue minerals in the chromite concentrate in sintering.
  • Binding agent 8 in the form of bentonite can for example contain the following in percentages of weight:
  • Si0 2 between 30 and 80 %
  • A1 2 0 3 between 0 and 40 %
  • an amount of carbonaceous material 6 may be added to the chromite concentrate feed 1 so that the amount of added carbonaceous material 6 in the resulting pelletizing feed 12 in terms of percentages of weight of the pelletizing feed 12 is between 0.5 % and 3 %.
  • the particle distribution of the of the carbonaceous material 6 is preferably between 70 and 80 % below 74 ⁇ , more preferably 75+2% below 74 ⁇ , such as 75% below 74 ⁇ .
  • an amount of dust 7 may be added so that the amount of added dust 7 in the resulting pelletizing feed in terms of percentages of weight of the pelletizing feed 12 is between 3 and 12 %.
  • the particle distribution of the dust 7 is preferably between 75 and 100 % below 74 ⁇ .
  • an amount of binding agent 8 may be added so that the amount of added binding agent 8 in the resulting pelletizing fees in terms of percentages of weight of the pelletizing feed 12 is between 0.5 and 3 %, preferably between 0.75 and 2.5 %, even more preferably between 1.0 and 2.5 %, such as 1.5 %.
  • the particle distribution of the binding agent is preferable 100% below 74 ⁇ .
  • slag 4 originating from processing of ferrous metal may be added to fluxing agent 2 prior the adding step so that fluxing agent 2 in the form or at least one of limestone, dolomite, quarts, or wollastonite and any mixture thereof and fluxing agent 2 in the form of slag 4 are at least partly mixed together prior the adding step.
  • fluxing agent 2 in the form or at least one of limestone, dolomite, quarts, or wollastonite and any mixture thereof and fluxing agent 2 in the form of slag 4 are at least partly mixed together prior the adding step.
  • fluxing agent 2 in the form or at least one of limestone, dolomite, quarts, or wollastonite and any mixture thereof and fluxing agent 2 in the form of slag 4 may be separately added to the chromite concentrate feed 1 in the adding step.
  • Such embodiments are illustrated in figures 2 and 4.
  • fluxing agent 2 containing in percentages of weight between 10 and 100 %, preferably between 50 and 100 %, more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal, may be added to the chromite ore feed 1. It is also possible to in adding step of the method to add fluxing agent 2 consisting solely of slag 4 originating from processing of ferrous metal to the chromite concentrate feed 1.
  • an amount of fluxing agent 2 may be added to the chromite concentrate feed 1 so that the resulting pelletizing feed 12 contains in percentages of weight between 1 and 10 %, preferably between 2 and 7 %, more preferable between 3 and 6 %, such as between 4 and 5 % fluxing agent 2.
  • the slag 4 originating from processing of ferrous metal and that is used as fluxing agent 2 in the adding step of the method may contain in percentages of weight:
  • CaO between 20 and 50 %, preferably between 35 and 45 %
  • SiC between 20 and 50 %, preferably between 30 and 40 %
  • MgO between 1 and 20 %, preferably between 5 and 15 %
  • AI2O3 between 1 and 20 %, preferably between 5 and 15 %
  • T1O2 between 0 and 50 %, preferably between 0 and 15 %
  • K 2 0 less than 5 %, preferably less than 1 %
  • Na 2 0 less than 5 %, preferably less than 1 %
  • the method may be used process for manufacturing ferrochrome alloy from chromite concentrate 5 such as in a process of the type as presented in publication WO 2012/172174.
  • the arrangement comprises a first feeding arrangement 9 for providing a chromite concentrate feed 1, and a second feeding arrangement 10 comprising at least a first feeding means (not marked with a reference numeral) for adding fluxing agent 2 to the chromite ore feed 1 to obtain a pelletizing feed 12.
  • the arrangement may comprise a mill 2 for fine-dividing the chromite concentrate feed 1.
  • the arrangement may comprise a drying means 11 for reducing the moisture content the chromite concentrate feed 1.
  • the first feeding means of the second feeding arrangement 10 is configured to add to the chromite concentrate feed 1 fluxing agent 2 containing slag 4 originating from processing of ferrous metal.
  • the second feeding arrangement 10 may comprise additionally at least one of the following: a second feeding means (not marked with a reference numeral) for adding carbonaceous material 6 such as coke to the chromite ore feed 1, a third feeding means (not marked with a reference numeral) for adding dust 7 to the chromite ore feed 1, and a fourth feeding means (not marked with a reference numeral) for adding binding agent 8 such as bentonite to the chromite ore feed 1.
  • the first feeding means of the second feeding arrangement 10 may be configured to add to the chromite concentrate feed 1 fluxing agent 2 containing in percentages of weight between 10 and 100 %, preferably between 50 and 100 %, more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal.
  • the first feeding means of the second feeding arrangement 10 may be configured to add fluxing agent 2 to the chromite concentrate feed 1 so that the pelletizing feed 12 obtained containing in percentages of weight between 1 and 10 %, preferably between 2 and 7 %, more preferable between 3 and 6 %, such as between 4 and 5 % fluxing agent 2.
  • the first feeding means of the second feeding arrangement 10 may be configured to add fluxing agent 2 in the form of slag 4 originating from processing of ferrous metal containing in percentages of weight:
  • CaO between 20 and 50 %, preferably between 35 and 45 %
  • Si0 2 between 20 and 50 %, preferably between 30 and 40 %
  • MgO between 1 and 20 %, preferably between 5 and 15 %
  • A1 2 0 3 between 1 and 20 %, preferably between 5 and 15 % ⁇ 2 0: less than 5 %, preferably less than 1 %
  • Na 2 0 less than 5 %, preferably less than 1 %
  • the arrangement may be used in an equipment for manufacturing ferrochrome alloy from chromite concentrate 5 such as in an equipment of the type as presented in publication WO 2012/172174.
  • the equipment presented in figures 1 and 3 comprises a slurry mixer 13, which is configured to mix the chromite concentrate feed 1 discharged from the mill 3.
  • the equipment presented in figures 1 and 3 comprises a filter 14, which is configured to dewater the chromite concentrate feed 1.
  • the equipment presented in the figures comprises a mixer 15, which is configured to mix the pelletizing feed 14 formed of chromite concentrate feed 1 and the fluxing agent 2 containing slag 4 and the optional carbonaceous material 6, dust 7, and binding agent 8.
  • the equipment presented in the figures comprises a pelletizing drum or disc 16, which is configured to pelletize the pelletizing feed 14 to form pellets 17.
  • the equipment presented in the figures comprises a roller screen 18, which is configured to ensure that uniformly sized pellets only are fed as an even pellet bed to an endless conveyor belt of a steel belt sintering furnace 19 so as to form sintered pellets 20 of the pellets 17.
  • the equipment presented in the figures comprises a third feeding arrangement 21 for feeding sintered pellets 21 together with additives such as lumpy ore, coke and quartz into a preheating kiln 22, which is configured to preheat the sintered pellets 21 prior charging the sintered pellets 21 into an smelting furnace 23. From the smelting furnace ferrochrome alloy 24 is discharged.
  • a third feeding arrangement 21 for feeding sintered pellets 21 together with additives such as lumpy ore, coke and quartz into a preheating kiln 22, which is configured to preheat the sintered pellets 21 prior charging the sintered pellets 21 into an smelting furnace 23. From the smelting furnace ferrochrome alloy 24 is discharged.
  • the equipment presented in the figures comprises also a high pressure water scrubber 25 for cleaning gas originating from the smelting furnace.
  • the equipment presented in figures 3 and 4 comprises also a burning means 25 that is arranged to receive carbon monoxide (CO) from the high pressure water scrubber 25 and to burn carbon monoxide (CO) to produce thermal energy for the drying means 11.
  • a burning means 25 that is arranged to receive carbon monoxide (CO) from the high pressure water scrubber 25 and to burn carbon monoxide (CO) to produce thermal energy for the drying means 11.
  • pelletizing feed 12 containing chromite concentrate 5 and fluxing agent 2 will be described in greater detail.
  • the fluxing agent 2 contains slag 4 originating from processing of ferrous metal.
  • the pelletizing feed 12 may contain additionally at least one of the following: (i) carbonaceous material 6 such as coke, (ii) dust 7, and (iii) binding agent 8 such as bentonite.
  • the fluxing agent 2 may contain in percentages of weight between 10 and 100 , preferably between 50 and 100 , more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal.
  • the pelletizing feed 12 may contain in percentages of weight between 1 and 10 , preferably between 2 and 7 , more preferable between 3 and 6 , such as between 4 and 5 % fluxing agent 2.
  • the slag 4 originating from processing of ferrous metal may contain in percentages of weight:
  • CaO between 20 and 50 %, preferably between 35 and 45 %
  • SiC between 20 and 50 %, preferably between 30 and 40 %
  • MgO between 1 and 20 %, preferably between 5 and 15 %
  • AI2O3 between 1 and 20 %, preferably between 5 and 15 %
  • K2O less than 5 %, preferably less than 1 %
  • test materials CI and C2 were twelve (12) lab tests were performed with test materials CI and C2 using bentonite as binding agent and as fluxing agents wollastonite, calcite, dolomite and slag originating from a blast furnace.
  • test materials CI and C3 had the composition in percentages of weight mentioned in table 1.
  • the slag had the following composition in percentages of weight:
  • the pelletizing was carried out on a laboratory disc with a diameter of 400 mm and a depth of 150 mm. The moisture content, wet and dry strength of pellets was measured.
  • Bentonite was used as a binder in the pelletizing.
  • the pelletizing mixture consisted of ground chromite concentrate and wollastonite, limestone and blast furnace slag as fluxes.
  • the pelletizing batch was mixed very carefully in a twin- shell mixer for 120 minutes.
  • the mixed batch was fed onto the disc manually.
  • the batch was moistened with a water sprayer bottle according to the formation of the pellets.
  • the desired diameter of pellets is 12 mm.
  • the amount of fluxes was added according to the characteristics of the pellets.
  • the diameter and compressive strength of the wet and dried pellets was measured.
  • the moisture content of the pellets was also measured.
  • the aim of the sintering was to perform the tests for achieving a satisfactory strength of the sintered pellets, about 200 kg/ pellet (a diameter 12 mm).
  • the sintering was carried out in high aluminium crucible (0.25 litres) in an induction furnace.
  • the sintering temperature was estimated to be in the range of 1300 -1450°C. Air was blown to the crucible to achieve oxidising sintering conditions. According to normal practice the temperature of the charge is measured during the tests. The batch was cooled by air and the samples are taken for analysing.

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Abstract

The invention relates to a method and to an arrangement to prepare chromite ore (5) for pelletizing and sintering. The invention relates also to a pelletizing feed. The method comprises a providing step for providing a chromite concentrate feed (1), and an adding step for adding at least fluxing agent (2) to the chromite concentrate feed (1) to obtain a pelletizing feed (12). The fluxing agent (2) is at least partly in the form slag (4) originating from processing of ferrous metal.

Description

METHOD AND ARRANGEMENT TO PREPARE CHROMITE CONCENTRATE FOR PELLETIZING AND SINTERING AND PELLETIZING FEED Field of the invention
The invention relates to a method to prepare chromite concentrate for pelletizing and sintering as defined in the preamble of independent claim 1.
The invention also relates to an arrangement to prepare chromite concentrate for pelletizing and sintering as defined in the preamble of independent claim 6.
The invention also relates to a pelletizing feed as defined in the preamble of independent claim 13.
Publication WO 2013/071955 presents a process for the manufacture of ferrochrome alloy comprising the steps of providing a pelletizing feed, wherein the pelletizing feed comprises chromite concentrate and silicon carbide as the only carbonaceous material and the only reducing agent; pelletizing the pelletizing feed to obtain pellets; sintering the pellets to obtain sintered pellets; mixing the sintered pellets with external reducing agent to obtain smelting feed; and smelting the smelting feed.
Publication WO 2013/071955 presents a pelletizing feed containing chromite ore, at least one nickel salt, and silicon carbide as the only carbonaceous material and the only reducing agent. The invention also relates to process for manufacturing the pelletizing feed comprising the steps providing chromite, at least one nickel salt and silicon carbide, and mixing chromite, at least one nickel salt and silicon carbide. The invention also relates to use of the pelletizing feed as a starting material for the manufacture of sintering feed. The invention also relates to a sintering feed in the form of pellets containing the pelletizing feed. The invention also relates to sintered pellets containing the sintering feed. The invention also relates to process for manufacturing the sintered pellets. The invention also relates to use of the sintered pellets as a component of smelting feed. The invention also relates to smelting feed comprising sintered pellets. The invention also relates to process for manufacturing ferrochrome alloy. The invention also relates to ferrochrome alloy obtainable by the method.
Both publication WO 2013/071955 and publication WO 2013/071955 suggests that the pelletizing feed, from which the sintered pellets are made, may comprise fluxing agents, such as limestone, dolomite, quarts, calcite or wollastonite and any mixture thereof. A reason for adding fluxing agent to the pelletizing feed is to achieve sufficient compressive strength of the sintered pellets which are produced in the subsequent sintering process by using the pelletizing feed. A sufficient compressive strength Fi2mm is typically between 180 and 220 kg. A disadvantage by using the fluxing agents mentioned in publication WO 2013/071955 and in publication WO 2013/071955, limestone, dolomite, quarts, calcite or wollastonite and any mixture thereof, is that these are relatively expensive. Publication US 3,825,638 presents a method for producing cold bound agglomerates from particulate iron oxide containing mineral concentrates using a steam liardenable binder. The binder is ground down together with iron oxide material at a high energy input to produce a fine grain additive material. The additive material is then mixed with the mineral concentrates and agglomerates are formed from the mixture and steam hardened.
Publication WO 2015/003669 relates to fluxing agents for the agglomeration process based on slag from the secondary metallurgy, the use of these fluxing agents in the process of agglomeration in the manufacture of the agglomerate designed for the use as a metallic charge in blast furnaces and a process of production of fluxing agents based on slag from the secondary metallurgy or based on a mixture of slag from the secondary metallurgy with other materials.
Objective of the invention
An object of the invention is to provide a method and an arrangement to prepare chromite ore for pelletizing and sintering and correspondingly to provide a pelletizing feed by means of which a pelletizing feed, containing fluxing agent for obtaining sufficient strength of the sintered pellets which are produced in the subsequent sintering process by using the pelletizing feed, can be obtained by using less expensive raw material.
Short description of the invention
The method to prepare chromite concentrate for pelletizing and sintering of the invention is characterized by the definitions of independent claim 1.
Preferred embodiments of the method are defined in the dependent claims 2 to 5.
The invention relates also to the use of the method according to any of the claims 1 to 5 in a process for producing ferrochrome alloy from chromite concentrate.
The arrangement to prepare chromite concentrate for pelletizing and sintering of the invention is correspondingly characterized by the definitions of independent claim 6.
Preferred embodiments of the arrangement are defined in the dependent claims 7 to 10.
The invention relates also to the use of the arrangement according to any of the claims 6 to 10 in an arrangement for producing ferrochrome alloy from chromite concentrate.
The pelletizing feed is correspondingly characterized by the definitions of independent claim 13.
Preferred embodiments of the pelletizing feed are defined in the dependent claims 14 to
17.
The invention relates also to sintered pellets as defined in claim 18 containing the pelletizing feed according to any of the claims 13 to 17.
The invention relates also to the in claim 19 defined use of the sintered pellets according to claim 18 as a component of smelting feed.
The invention relates also to a smelting feed as defined in claim 20 containing the sintered pellets according to claim 18.
The invention relates also to a process as defined in claim 21 for manufacturing ferrochrome alloy comprising the step of smelting the smelting feed according to claim 20.
The invention relates also to ferrochrome alloy as defined in claim 22 and obtainable by the process according to claim 21.
The invention is based on that the fluxing agent that is used is at least partly slag originating from processing of ferrous metal.
By method, the arrangement and the pelletizing feed, sintered pellets having a compressive strength Fi2mm of more than 200 kg can be produced.
The compressive strength of the sintered pellets Fi2mm can be calculated according to the following formula:
Fi2mm = (12 / D)2 * FD, where
D: measured diameter of the pellet (mm)
12: reference diameter of the desired pellet (mm)
FD: the measured compressive strength of the pellet (kg/pellet)
List of figures
In the following the invention will described in more detail by referring to the figures, which
Figure 1 is a schematic flow chart of a first embodiment of equipment containing an arrangement according to an embodiment of the invention,
Figure 2 is a schematic flow chart of a second embodiment of equipment containing an arrangement according to an embodiment of the invention,
Figure 3 is a schematic flow chart of a third embodiment of equipment containing an arrangement according to an embodiment of the invention, and
Figure 4 is a schematic flow chart of a fourth embodiment of equipment containing an arrangement according to an embodiment of the invention.
Detailed description of the invention
First the method to prepare chromite concentrate 5 for pelletizing and sintering and some preferred embodiments and variants of the method will be described in greater detail.
Chromite is the ore which is excavated from the chromite deposit. The chromite concentrate is the product of the beneficiation plant. The ganque components are mainly separated to the wastes for improving the grade of chromite for the pelletizing and sintering.
The method comprises a providing step for providing a chromite concentrate feed 1 and an adding step for adding at least fluxing agent 2 to the chromite concentrate feed 1 to obtain a pelletizing feed 12.
A purpose of the fluxing agent 2 is to lower the melting point of the slag forming components in the pelletizing feed 12 and to provide more slag forming components to the pelletizing feed 12. Another purpose of the fluxing agent is to during a sintering process, where pellets previously formed of the pelletizing feed 12 is sintered into sintered pellets, to provide more connections and connections of better quality in the sintered pellets by melting and subsequently solidifying the binding silicates in the fluxing agent 2.
The method may include a fine-dividing step for fine-dividing the chromite concentrate feed 1 to a particle size distribution of 70 to 90 % below 74 μιη, preferably 80+2% below 74 μιη, and more preferably about 80% below 74 μιη for example in a mill 3.
In the adding step of the method, fluxing agent 2 in the form of slag 4 originating from processing of ferrous metal (including ferroalloys) is added to the chromite concentrate feed 1.
The particle size distribution of the fluxing agent 2 may be 80 to 100%, preferably 100 % below 74 μιη (200 mesh).
The method may include a fine-dividing step for fine-dividing the slag 4 prior the adding step for example by milling in a mill 3.
In the adding step of the method, additionally at least one of the following may be added to the chromite concentrate feed 1: (i) carbonaceous material 6 such as coke, (ii) dust 7, and (iii) binding agent 8 such as bentonite for example sodium- activated calcium betonite, water-based binding agent, and/or organic binding agent. The purpose of the possible binding agent 8 is give the pellets, which are produced from the pelletizing feed 12, enough dry- and wet strength so that the pellets can firstly withstand transportation from a means for forming pellets such as from a pelletizing drum or disc 16 to a sintering means such as to a steel belt sintering furnace 19, where the pellets are strengthened by performing sintering to produced sintered pellets and secondly withstand drying, heating, sintering in the sintering means until a desired strengthening by sintering is achieved. The strengthening effect of the binding agent in the resulting sintered pellets is quite marginal in comparison to the strengthening effect resulting from fluxing agent and gangue minerals in the chromite concentrate in sintering.
Binding agent 8 in the form of bentonite can for example contain the following in percentages of weight:
Si02: between 30 and 80 %,
A1203: between 0 and 40 %,
CaO: between 0 and 20 %,
MgO: between 0 and 20 %
Na20: between 0 and 20 %
K20: between 0 and 20 %
Fe203: between 0 and 20 %
Ti02: between 0 and 20 %
Volatiles: between 0 and 50 %
In the adding step of the method, an amount of carbonaceous material 6 may be added to the chromite concentrate feed 1 so that the amount of added carbonaceous material 6 in the resulting pelletizing feed 12 in terms of percentages of weight of the pelletizing feed 12 is between 0.5 % and 3 %. The particle distribution of the of the carbonaceous material 6 is preferably between 70 and 80 % below 74 μιη, more preferably 75+2% below 74 μιη, such as 75% below 74 μιη. and between 40 and 60 % below 37 μιη, more preferably 55 % below 37 μιη In the adding step of the method, an amount of dust 7 may be added so that the amount of added dust 7 in the resulting pelletizing feed in terms of percentages of weight of the pelletizing feed 12 is between 3 and 12 %. The particle distribution of the dust 7 is preferably between 75 and 100 % below 74 μιη.
In the adding step of the method, an amount of binding agent 8 may be added so that the amount of added binding agent 8 in the resulting pelletizing fees in terms of percentages of weight of the pelletizing feed 12 is between 0.5 and 3 %, preferably between 0.75 and 2.5 %, even more preferably between 1.0 and 2.5 %, such as 1.5 %. The particle distribution of the binding agent is preferable 100% below 74 μιη.
In the method, slag 4 originating from processing of ferrous metal may be added to fluxing agent 2 prior the adding step so that fluxing agent 2 in the form or at least one of limestone, dolomite, quarts, or wollastonite and any mixture thereof and fluxing agent 2 in the form of slag 4 are at least partly mixed together prior the adding step. Such embodiments are illustrated in figures 1 and 3.
In the method, fluxing agent 2 in the form or at least one of limestone, dolomite, quarts, or wollastonite and any mixture thereof and fluxing agent 2 in the form of slag 4 may be separately added to the chromite concentrate feed 1 in the adding step. Such embodiments are illustrated in figures 2 and 4.
In the adding step of the method, fluxing agent 2 containing in percentages of weight between 10 and 100 %, preferably between 50 and 100 %, more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal, may be added to the chromite ore feed 1. It is also possible to in adding step of the method to add fluxing agent 2 consisting solely of slag 4 originating from processing of ferrous metal to the chromite concentrate feed 1.
In the adding step of the method, an amount of fluxing agent 2 may be added to the chromite concentrate feed 1 so that the resulting pelletizing feed 12 contains in percentages of weight between 1 and 10 %, preferably between 2 and 7 %, more preferable between 3 and 6 %, such as between 4 and 5 % fluxing agent 2.
The slag 4 originating from processing of ferrous metal and that is used as fluxing agent 2 in the adding step of the method may contain in percentages of weight:
CaO: between 20 and 50 %, preferably between 35 and 45 %
SiC : between 20 and 50 %, preferably between 30 and 40 %
MgO: between 1 and 20 %, preferably between 5 and 15 %
AI2O3: between 1 and 20 %, preferably between 5 and 15 % T1O2: between 0 and 50 %, preferably between 0 and 15 %,
K20: less than 5 %, preferably less than 1 %
Na20: less than 5 %, preferably less than 1 %
The method may be used process for manufacturing ferrochrome alloy from chromite concentrate 5 such as in a process of the type as presented in publication WO 2012/172174.
Next the arrangement to prepare chromite concentrate 5 for pelletizing and sintering and some embodiments and variants of the method will be describe in greater detail.
The arrangement comprises a first feeding arrangement 9 for providing a chromite concentrate feed 1, and a second feeding arrangement 10 comprising at least a first feeding means (not marked with a reference numeral) for adding fluxing agent 2 to the chromite ore feed 1 to obtain a pelletizing feed 12.
The arrangement may comprise a mill 2 for fine-dividing the chromite concentrate feed 1. The arrangement may comprise a drying means 11 for reducing the moisture content the chromite concentrate feed 1.
The first feeding means of the second feeding arrangement 10 is configured to add to the chromite concentrate feed 1 fluxing agent 2 containing slag 4 originating from processing of ferrous metal.
The second feeding arrangement 10 may comprise additionally at least one of the following: a second feeding means (not marked with a reference numeral) for adding carbonaceous material 6 such as coke to the chromite ore feed 1, a third feeding means (not marked with a reference numeral) for adding dust 7 to the chromite ore feed 1, and a fourth feeding means (not marked with a reference numeral) for adding binding agent 8 such as bentonite to the chromite ore feed 1.
The first feeding means of the second feeding arrangement 10 may be configured to add to the chromite concentrate feed 1 fluxing agent 2 containing in percentages of weight between 10 and 100 %, preferably between 50 and 100 %, more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal.
The first feeding means of the second feeding arrangement 10 may be configured to add fluxing agent 2 to the chromite concentrate feed 1 so that the pelletizing feed 12 obtained containing in percentages of weight between 1 and 10 %, preferably between 2 and 7 %, more preferable between 3 and 6 %, such as between 4 and 5 % fluxing agent 2.
The first feeding means of the second feeding arrangement 10 may be configured to add fluxing agent 2 in the form of slag 4 originating from processing of ferrous metal containing in percentages of weight:
CaO: between 20 and 50 %, preferably between 35 and 45 %
Si02: between 20 and 50 %, preferably between 30 and 40 %
MgO: between 1 and 20 %, preferably between 5 and 15 %
A1203: between 1 and 20 %, preferably between 5 and 15 % Κ20: less than 5 %, preferably less than 1 %
Na20: less than 5 %, preferably less than 1 %
The arrangement may be used in an equipment for manufacturing ferrochrome alloy from chromite concentrate 5 such as in an equipment of the type as presented in publication WO 2012/172174.
The equipment presented in figures 1 and 3 comprises a slurry mixer 13, which is configured to mix the chromite concentrate feed 1 discharged from the mill 3.
The equipment presented in figures 1 and 3 comprises a filter 14, which is configured to dewater the chromite concentrate feed 1.
The equipment presented in the figures comprises a mixer 15, which is configured to mix the pelletizing feed 14 formed of chromite concentrate feed 1 and the fluxing agent 2 containing slag 4 and the optional carbonaceous material 6, dust 7, and binding agent 8.
The equipment presented in the figures comprises a pelletizing drum or disc 16, which is configured to pelletize the pelletizing feed 14 to form pellets 17.
The equipment presented in the figures comprises a roller screen 18, which is configured to ensure that uniformly sized pellets only are fed as an even pellet bed to an endless conveyor belt of a steel belt sintering furnace 19 so as to form sintered pellets 20 of the pellets 17.
The equipment presented in the figures comprises a third feeding arrangement 21 for feeding sintered pellets 21 together with additives such as lumpy ore, coke and quartz into a preheating kiln 22, which is configured to preheat the sintered pellets 21 prior charging the sintered pellets 21 into an smelting furnace 23. From the smelting furnace ferrochrome alloy 24 is discharged.
The equipment presented in the figures comprises also a high pressure water scrubber 25 for cleaning gas originating from the smelting furnace.
The equipment presented in figures 3 and 4 comprises also a burning means 25 that is arranged to receive carbon monoxide (CO) from the high pressure water scrubber 25 and to burn carbon monoxide (CO) to produce thermal energy for the drying means 11.
Next the pelletizing feed 12 containing chromite concentrate 5 and fluxing agent 2 and some embodiments and variants of the pelletizing feed 12 will be described in greater detail.
The fluxing agent 2 contains slag 4 originating from processing of ferrous metal.
The pelletizing feed 12 may contain additionally at least one of the following: (i) carbonaceous material 6 such as coke, (ii) dust 7, and (iii) binding agent 8 such as bentonite.
The fluxing agent 2 may contain in percentages of weight between 10 and 100 , preferably between 50 and 100 , more preferably between 75 and 100 % slag 4 originating from processing of ferrous metal.
The pelletizing feed 12 may contain in percentages of weight between 1 and 10 , preferably between 2 and 7 , more preferable between 3 and 6 , such as between 4 and 5 % fluxing agent 2. The slag 4 originating from processing of ferrous metal may contain in percentages of weight:
CaO: between 20 and 50 %, preferably between 35 and 45 %
SiC : between 20 and 50 %, preferably between 30 and 40 %
MgO: between 1 and 20 %, preferably between 5 and 15 %
AI2O3: between 1 and 20 %, preferably between 5 and 15 %
K2O: less than 5 %, preferably less than 1 %
Na20: less than 5 %, preferably less than 1 % Examples
Twelve (12) lab tests was performed with test materials CI and C2 using bentonite as binding agent and as fluxing agents wollastonite, calcite, dolomite and slag originating from a blast furnace.
The test materials CI and C3 had the composition in percentages of weight mentioned in table 1.
Table 1. Chemical analysis of chromites.
The slag had the following composition in percentages of weight:
- MgO: 8.3 %
- CaO: 40.9 %
The pelletizing was carried out on a laboratory disc with a diameter of 400 mm and a depth of 150 mm. The moisture content, wet and dry strength of pellets was measured.
Bentonite was used as a binder in the pelletizing.
The pelletizing mixture consisted of ground chromite concentrate and wollastonite, limestone and blast furnace slag as fluxes. The pelletizing batch was mixed very carefully in a twin- shell mixer for 120 minutes.
The mixed batch was fed onto the disc manually. The batch was moistened with a water sprayer bottle according to the formation of the pellets. The desired diameter of pellets is 12 mm.
The amount of fluxes was added according to the characteristics of the pellets.
After the pelletizing, the diameter and compressive strength of the wet and dried pellets was measured. The moisture content of the pellets was also measured.
The aim of the sintering was to perform the tests for achieving a satisfactory strength of the sintered pellets, about 200 kg/ pellet (a diameter 12 mm).
The sintering was carried out in high aluminium crucible (0.25 litres) in an induction furnace. The sintering temperature was estimated to be in the range of 1300 -1450°C. Air was blown to the crucible to achieve oxidising sintering conditions. According to normal practice the temperature of the charge is measured during the tests. The batch was cooled by air and the samples are taken for analysing.
Table 2: test results:
As can be seen from table 2, by preparing a pelletizing feed containing 1 % in terms of percentages of weight) of bentonite as binding agent and between 4 and 5 % (in terms of percentages of weight) of fluxing agent consisting of 100 % slag or 50 % slag and 50 % WoUastonite, by pelletizing the pelletizing feed to obtain pellets, and by sintering the pellets to obtain sintered pellets, the result was sintered pellets having a compressive strength Fi2mm of more than 200 kg.
It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

Claims

Claims
1. A method to prepare chromite ore (5) for pelletizing and sintering, wherein the method comprises:
a providing step for providing a chromite concentrate feed (1), and
an adding step for adding at least fluxing agent (2) to the chromite concentrate feed (1) to obtain a pelletizing feed (12),
characterized
by adding in the adding step fluxing agent (2) in the form slag (4) originating from processing of ferrous metal.
2. The method according to claim 1, characterized by
adding in the adding step additionally at least one of the following to the chromite concentrate feed (1): (i) carbonaceous material (6) such as coke, (ii) dust (7), and (iii) binding agent (8) such as bentonite.
3. The method according to claim 1 or 2, characterized
by the fluxing agent (2) containing in percentages of weight between 10 and 100 , preferably between 50 and 100 , more preferably between 75 and 100 % slag (4) originating from processing of ferrous metal.
4. The method according to any of the claims 1 to 3, characterized
by the pelletizing feed (12) containing in percentages of weight between 1 and 10 , preferably between 2 and 7 , more preferably between 3 and 6 , such as between 4 to 5 % fluxing agent (2).
5. The method according to any of the claims 1 to 4, characterized
by the slag (4) originating from processing of ferrous metal containing in percentages of weight:
CaO: between 20 and 50 %,
Si02: between 20 and 50 %,
MgO: between 1 and 20 %,
A1203: between 1 and 20 %,
Ti02: between 0 and 50 ,
K20: less than 5 , and
Na20: less than 5 %.
6. An arrangement to prepare chromite ore (5) for pelletizing and sintering, wherein the arrangement comprises: a first feeding arrangement (9) for providing a chromite concentrate feed (1), and a second feeding arrangement (10) comprising at least a first feeding means for adding fluxing agent (2) to the chromite concentrate feed (1) to obtain a pelletizing feed (12),
characterized
by the first feeding means of the second feeding arrangement (10) being configured to add fluxing agent (2) containing slag (4) originating from processing of ferrous metal.
7. The arrangement according to claim 6, characterized
by the second feeding arrangement (10) comprising additionally at least one of the following:
a second feeding means for adding carbonaceous material (6) such as coke to the chromite concentrate feed (l),
a third feeding means for adding dust (7) to the chromite concentrate feed (1), a fourth feeding means for adding binding agent (8) such as bentonite to the chromite concentrate feed (1).
8. The arrangement according to claim 6 or 7, characterized
by the first feeding means of the second feeding arrangement (10) being configured to add fluxing agent (2) containing in percentages of weight between 10 and 100 %, preferably between 50 and 100 %, more preferably between 75 and 100 % slag (4) originating from processing of ferrous metal.
9. The arrangement according to any of the claims 6 to 8, characterized
by the first feeding means of the second feeding arrangement (10) being configured to add fluxing agent (2) to the chromite concentrate feed (1) so that the pelletizing feed (12) obtained containing in percentages of weight between 1 and 10 %, preferably between 2 and 7 %, more preferably between 3 and 6 %, such as between 4 and 5 % fluxing agent (2).
10. The arrangement according to any of the claims 6 to 9, characterized
by first feeding means of the second feeding arrangement (10) being configured to add fluxing agent (2) in the form of slag (4) originating from processing of ferrous metal containing in percentages of weight:
CaO: between 20 and 50 %,
Si02: between 20 and 50 %,
MgO: between 1 and 20 %,
A1203: between 1 and 20 %,
K20: less than 5 %, and
Na20: less than 5 %.
11. Use of the method according to any of the claims 1 to 5 in a process for manufacturing ferrochrome alloy from chromite concentrate (5).
12. Use of the arrangement according to any of the claims 6 to 10 in an equipment for manufacturing ferrochrome alloy from chromite concentrate (5).
13. Pelletizing feed (12) containing chromite concentrate (5) and fluxing agent (2), characterized
by the fluxing agent (2) containing slag (4) originating from processing of ferrous metal.
14. The pelletizing feed (12) according to claim 13, characterized
by containing additionally at least one of the following: (i) carbonaceous material (6) such as coke, (ii) dust (7), and (iii) binding agent (8) such as bentonite.
15. The pelletizing feed (12) according to claim 13 or 14, characterized
by the fluxing agent (2) containing in percentages of weight between 10 and 100 , preferably between 50 and 100 , more preferably between 75 and 100 % slag (4) originating from processing of ferrous metal.
16. The pelletizing feed (12) according to any of the claims 13 to 15, characterized
by the pelletizing feed (12) containing in percentages of weight between 1 and 10 , preferably between 2 and 7 , more preferably between 3 and 6 , such as between 4 and 5 % fluxing agent (2).
17. The pelletizing feed (12) according to any of the claims 13 to 16, characterized
by first feeding means of the second feeding arrangement (10) being configured to add fluxing agent (2) in the form of slag (4) originating from processing of ferrous metal containing in percentages of weight:
CaO: between 20 and 50 %,
Si02: between 20 and 50 %,
MgO: between 1 and 20 %,
A1203: between 1 and 20 %,
K20: less than 5 , and
Na20: less than 5 %.
18. Sintered pellets containing the pelletizing feed (12) according to any of the claims 13 to 17.
19. Use of the sintered pellets according to claim 18 as a component of smelting feed.
20. Smelting feed containing sintered pellets according to claim 18.
21. Process for manufacturing ferrochrome alloy comprising the step of smelting smelting feed according to claim 20.
22. Ferrochrome alloy obtainable by the process according to claim 21.
EP16704030.2A 2015-02-05 2016-02-05 Method and arrangement to prepare chromite concentrate for pelletizing and sintering and pelletizing feed Withdrawn EP3253896A1 (en)

Applications Claiming Priority (2)

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FI20155075A FI127031B (en) 2015-02-05 2015-02-05 PROCEDURE AND ARRANGEMENTS FOR PREPARING CHROMITE CONCENTRATE FOR PELLETING AND SINTERING AND FEED FOR PELLETING
PCT/FI2016/050077 WO2016124823A1 (en) 2015-02-05 2016-02-05 Method and arrangement to prepare chromite concentrate for pelletizing and sintering and pelletizing feed

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SE350769C (en) 1970-10-19 1977-09-26 Cold Bound Pellets Ab PROCEDURE FOR THE PREPARATION OF COLD-BINDED AGGLOMATER OF PARTICULAR MINERAL CONCENTRATE
US4790872A (en) * 1988-01-19 1988-12-13 Hamilton Specialty Bar Division Of Slater Industries, Inc. Additive for promoting slag formation in steel refining ladle
CN101638730B (en) * 2008-07-31 2015-03-25 塔塔钢铁有限公司 Method for preparing sponge chromium from metallurgical-grade chromite concentrate fine powder
FI9406U1 (en) * 2011-06-15 2011-10-11 Outotec Oyj Apparatus for making ore concentrate for pelleting
KR101492783B1 (en) * 2011-11-15 2015-02-12 오토텍 오와이제이 Process for the manufacture of ferrochrome
CN103060548B (en) * 2013-02-04 2014-05-07 重庆大学 Method for sintering chromite powder recycled based on ferronickel smelting furnace slag
CZ2013531A3 (en) 2013-07-08 2015-02-04 Ecofer, S.R.O. Agglomeration slagging medium, process for preparing the slagging medium, agglomeration mixture for producing agglomerate and use of secondary metallurgy slags as slagging media for producing the agglomeration mixture um

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CN107949646A (en) 2018-04-20

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