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WO2002055745A1 - Method for pelletization of iron ore - Google Patents

Method for pelletization of iron ore Download PDF

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Publication number
WO2002055745A1
WO2002055745A1 PCT/FR2002/000063 FR0200063W WO02055745A1 WO 2002055745 A1 WO2002055745 A1 WO 2002055745A1 FR 0200063 W FR0200063 W FR 0200063W WO 02055745 A1 WO02055745 A1 WO 02055745A1
Authority
WO
WIPO (PCT)
Prior art keywords
zones
temperature
pellets
zone
equal
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.)
Ceased
Application number
PCT/FR2002/000063
Other languages
French (fr)
Inventor
Marc Bremont
Robert C. Moe
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.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Cliffs Mining Services Co
Original Assignee
Air Liquide SA
LAir Liquide SA a Directoire et Conseil de Surveillance pour lEtude et lExploitation des Procedes Georges Claude
Cliffs Mining Services Co
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 Air Liquide SA, LAir Liquide SA a Directoire et Conseil de Surveillance pour lEtude et lExploitation des Procedes Georges Claude, Cliffs Mining Services Co filed Critical Air Liquide SA
Priority to BR0206399-9A priority Critical patent/BR0206399A/en
Priority to AU2002233406A priority patent/AU2002233406B2/en
Priority to CA002433853A priority patent/CA2433853A1/en
Publication of WO2002055745A1 publication Critical patent/WO2002055745A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • C22B1/16—Sintering; Agglomerating
    • C22B1/20—Sintering; Agglomerating in sintering machines with movable grates
    • C22B1/205—Sintering; Agglomerating in sintering machines with movable grates regulation of the sintering process
    • 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
    • C22B1/2413—Binding; Briquetting ; Granulating enduration of pellets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B21/00—Open or uncovered sintering apparatus; Other heat-treatment apparatus of like construction
    • F27B21/06—Endless-strand sintering machines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories or equipment specially adapted for rotary-drum furnaces
    • F27B7/2016—Arrangements of preheating devices for the charge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/20—Details, accessories or equipment specially adapted for rotary-drum furnaces
    • F27B7/38—Arrangements of cooling devices
    • F27B7/383—Cooling devices for the charge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/06—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated
    • F27B9/10—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated heated by hot air or gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/30—Details, accessories or equipment specially adapted for furnaces of these types
    • F27B9/3005—Details, accessories or equipment specially adapted for furnaces of these types arrangements for circulating gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0006—Monitoring the characteristics (composition, quantities, temperature, pressure) of at least one of the gases of the kiln atmosphere and using it as a controlling value
    • F27D2019/0012—Monitoring the composition of the atmosphere or of one of their components
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D21/00—Arrangement of monitoring devices; Arrangement of safety devices
    • F27D21/0014—Devices for monitoring temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27M—INDEXING SCHEME RELATING TO ASPECTS OF THE CHARGES OR FURNACES, KILNS, OVENS OR RETORTS
    • F27M2001/00—Composition, conformation or state of the charge
    • F27M2001/18—Composition, conformation or state of the charge in the form of pellets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27M—INDEXING SCHEME RELATING TO ASPECTS OF THE CHARGES OR FURNACES, KILNS, OVENS OR RETORTS
    • F27M2003/00—Type of treatment of the charge
    • F27M2003/03—Calcining

Definitions

  • the subject of the present invention is a process for pelletizing iron ore and an installation for implementing said process.
  • iron ore used to make steel is very rarely naturally available in a form. directly usable by the steel industry. In most cases, it has to undergo various stages of concentration and preparation to make it compatible with current metallurgical processes. Indeed, calibrated ore is increasingly rare and the latter does not always meet the requirements of metal production processes.
  • the first classic step in preparation. iron ore consists in giving it a determined chemical composition. The ore is in fact generally too poor in iron and too rich in undesirable oxides, such as silica, to be used in a metal production process. To improve its qualities, it is ground and then the iron oxide particles are concentrated until a high iron content is obtained.
  • the second step consists in giving this ground ore mechanical and physical characteristics which give it enough resistance to withstand the stresses undergone in metallurgical processes such as blast furnaces or direct reduction furnaces. These characteristics include mechanical strength at high temperatures, reducibility, abrasion resistance, porosity, etc.
  • This second stage goes through a phase of agglomeration of the ores in the form of particles of medium particle size from the concentrated fines.
  • pelletizing makes it possible to obtain iron ore pellets with a diameter of the order of 10 mm. This transformation is generally carried out by the mining companies on the extraction sites or on the ports of export of the ore, the ore sold to the steelmakers then being an ore agglomerated into pellets.
  • the installation comprises a first part 12 for forming raw pellets.
  • the ore is mixed in desired proportions with certain additives such as fluxes, binders and possibly a fuel in the form of coke dust for example.
  • At exit 14 of part 12 of the installation there are therefore raw pellets with a suitable diameter, but low mechanical strength.
  • the pellets are loaded on a drive conveyor (or grid) 16 by forming a bed with a thickness of the order of about twenty centimeters.
  • the grid 16 moves in a tunnel 20, in which a stream of hot gases obtained by burners not shown in FIG. 1 is created.
  • the grid 16 consists of a gas-permeable strip, most often made of metallic materials, to allow forced circulation of hot gases through the bed of pellets by means of fans not shown.
  • the tunnel 20 is separated into several functional zones which, themselves, can be subdivided into several stages. First of all, there is the drying zone 22 in which the free water present in the pellets is evaporated, then the water of constitution is eliminated in turn. On leaving the drying zone, the carbonaceous materials (fluxes) are calcined, causing an escape of carbon dioxide. In the following section 24, called preheating, the air circulation in the bed of pellets is comparable to that of the dryer.
  • the iron in Fe2 + form present is oxidized by the oxygen present in the gases circulating through the bed of pellets while the bed of pellets crosses this section. This reaction releases a significant amount of heat which is added to that provided by the burners.
  • fossil fuel is mixed with the ore and its combustion in this preheating section compensates for the heat input given by oxidation in the case where magnetite is predominant in the pellets.
  • These iron oxidation reactions are very important for product quality and must be completed before sintering the ore to obtain a good quality end product.
  • the sintering reactions begin at the end of the preheating section 24.
  • the pellets at the outlet of section 24 are loaded, in this embodiment, into a rotary oven 26 provided with a large burner.
  • the hot gases circulate essentially transversely with respect to the direction of movement of the ore pellets.
  • the pellets are heated by the flame and the radiation of the refractories constituting the oven. They are thus kept at a high temperature during their stay in the oven. It is during this stage that sintering and recrystallization take place which will give their mechanical properties to the pellets.
  • the heating section may consist of an extension of the tunnel similar to that which defines zones 22 and 24 (straight chain).
  • the installation ends with a cooling zone 28 in which the pellets are cooled to ambient temperature by circuits 30 for forced circulation of cold air through the bed of pellets. Most often, the air leaving the cooler is used in the drying zone 22 or in the oven 26.
  • the oxidation reaction does not have time to take place properly in the preheating part 24 of the installation.
  • the coolers finish this oxidation and therefore operate as ovens over part of their length.
  • the fans are limited in capacity, the air flow in the coolers cannot be increased.
  • the length remaining to cool the load is no longer sufficient, which becomes a bottleneck for the productivity of the installation.
  • sintering a not fully oxidized pellet degrades the quality of the product obtained. It is common to see an oxidation performed at only 60% at the end of preheating.
  • An object of the present invention is to provide a pelletizing process which makes it possible to improve the oxidation of the ore while limiting the consumption of oxygen required and therefore maintaining the economic viability of the installation.
  • the iron ore pelletizing process comprises the following steps: - pellets are provided consisting of a mixture of iron ore and additives,
  • a bed of said pellets is formed which is moved into a treatment installation comprising a drying zone, a preheating zone and a heating zone, said zones being supplied by a counter-current circulation of hot gases produced in part by burners, and a cooling section disposed at the outlet of said zones;
  • the temperature of said hot gases is measured in said zones or portions of zones; - said measured temperatures are compared to a predetermined maximum value and to a predetermined minimum value;
  • Oxygen is injected, at least into some of said zones or portions of zones for which the measured temperature is between said maximum value and said minimum value, by controlling the flow rate, thereby significantly improving the oxidation of the iron ore contained in said pellets at the exit of said zones.
  • a second object of the invention is to provide an installation, in particular for implementing the defined method.
  • the pelletizing plant for the processing of ore pellets consisting of ore and additives comprises:
  • a drying zone a preheating zone, a heating zone and a cooling section, means for moving a bed of said pellets in said zones and in said section, said zones and said section being equipped with heating means and circulation of hot gas;
  • the pelletizing process consists in using a pelletizing installation of the same type as that already used but, in a first step, the temperatures are determined during the normal operating phase of the installation. in the zones in particular for drying 22, for preheating 24 and possibly for heating 26.
  • each of these zones is equipped with several temperature sensors such as C1, C2, ... C6 which are mounted in the zone drying, in the preheating zone and possibly in the heating zone formed by the rotary kiln 26.
  • These temperatures are supplied to a treatment installation 40 which compares the temperatures measured by the various sensors Ci and the maximum and minimum temperatures predetermined corresponding to the most favorable temperature regions to produce oxidation by an excess of oxygen born.
  • the temperature ranges are 600 to 1,300 ° C and preferably 850 to 1,100 ° C, the latter temperature range corresponding to the vast majority of the ores to be treated.
  • Figures 3 and 4 show curves recorded during isothermal laboratory tests. A sample of ore is heated to a temperature T under an inert atmosphere. This temperature, once stabilized, is kept constant throughout the test. The sample is then subjected to an atmosphere composed of nitrogen and oxygen and the oxygen content of which is controlled. The change in mass resulting from the oxidation of the ore by atmospheric oxygen is recorded as a function of time in order to quantitatively follow the phenomenon.
  • the curves shown in FIG. 3 provide the final oxidation rate of the ore as a function of the maximum temperature in which the ore is placed for oxygen injection rates of 15% (A), 18% (B), 21% (C) and 23% (D). It can be seen that these curves have a maximum oxidation zone in the range from 700 ° C to 1300 ° C.
  • the curves in FIG. 4 give the average oxidation speed of the ore in mol.g "1.
  • S " 1 as a function of the maximum temperature for four oxygen contents.
  • These curves reflect the "oxidation rate" which has a maximum in the temperature range from 800 ° C to 1200 ° C.
  • the choice of temperature ranges from 600 ° C to 1,300 ° C and preferably from 850 ° C to 1,100 ° C results from a compromise between the results corresponding to these two series of curves.
  • the portions of the zone in which this temperature range is reached are determined, zones or portions of zone where the oxygen injection must be carried out.
  • the zones or portions of zones of oxygen injectors such as 11 and 12 are fitted, which, in the particular example shown in the figure, are arranged in the preheating zone 24
  • These injectors are connected to an oxygen source 44 via an appropriate system.
  • the control of these valves by analogous means makes it possible to adjust the oxygen flow rate as a function of additional information such as the oxygen content in the air, etc., which is supplied by other sensors such as K1, K2, etc.
  • the indications provided by these sensors and transmitted to the treatment unit 40 make it possible to adapt the oxygen flow rate in the different zones or portions of zones of the pelletizing installation.
  • the installation comprises a rotary oven 26
  • the injection of oxygen raises specific problems and this solution will only be adopted in special cases.
  • the heating zone is an extension of the preheating zone
  • the oxygen injection can be carried out in the heating zone if the temperatures of the gases in this zone are included in the ranges' mentioned above.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Manufacturing & Machinery (AREA)
  • Environmental & Geological Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Manufacture Of Iron (AREA)

Abstract

The invention concerns a method for pelletization of iron ore. Said method is characterised in that it consists in supplying pellets consisting of a mixture of iron ore and additives, forming a bed of said pellets which is displaced in an processing installation comprising a drying zone, a pre-heating zone and a heating zone supplied with counter-current circulation of hot gases and a cooling section arranged at the output of said zones; measuring in said zones or zone portions the temperature of said hot gases; comparing said measured temperatures with predetermined maximum and minimum values; and injecting oxygen, at least in some of said zones for which the measured temperature ranges between the maximum and minimum values, whereby the oxidation of the iron ore is substantially enhanced.

Description

PROCEDE DE BOULETAGE DE MINERAI DE FER IRON ORE BALLING PROCESS

La présente invention a pour objet un procédé de bouletage de minerai de fer et une installation de mise en oeuvre dudit procédé.The subject of the present invention is a process for pelletizing iron ore and an installation for implementing said process.

Le minerai de fer utilisé pour la fabrication d'acier est très rarement disponible naturellement sous une forme. directement utilisable par l'industrie sidérurgique. Il faut le plus souvent lui fair-e subir diverses étapes de concentration et de préparation pour le rendre compatible avec les procédés métallurgiques actuels. En effet, le minerai calibré est de plus en plus rare et ce dernier ne répond pas toujours aux exigences des procédés d'élaboration du métal. La première étape classique de la préparation. du minerai de fer consiste à lui donner une composition chimique déterminée. Le minerai est en effet généralement trop pauvre en fer et trop riche en oxydes indésirables, tels que de la silice, pour être utilisé dans un procédé de production de métal. Pour améliorer ses qualités, il est broyé puis les particules d'oxyde de fer sont concentrées jusqu'à l'obtention d'une teneur en fer élevée. La seconde étape consiste à donner à ce minerai broyé des caractéristiques mécaniques et physiques qui lui confèrent suffisamment de résistance pour supporter les contraintes subies dans les procédés métallurgiques tels que les hauts fourneaux ou les fours de réduction directe. Ces caractéristiques sont notamment la tenue mécanique à hautes températures, la réductibilité, la résistance à l'abrasion, la porosité, etc.The iron ore used to make steel is very rarely naturally available in a form. directly usable by the steel industry. In most cases, it has to undergo various stages of concentration and preparation to make it compatible with current metallurgical processes. Indeed, calibrated ore is increasingly rare and the latter does not always meet the requirements of metal production processes. The first classic step in preparation. iron ore consists in giving it a determined chemical composition. The ore is in fact generally too poor in iron and too rich in undesirable oxides, such as silica, to be used in a metal production process. To improve its qualities, it is ground and then the iron oxide particles are concentrated until a high iron content is obtained. The second step consists in giving this ground ore mechanical and physical characteristics which give it enough resistance to withstand the stresses undergone in metallurgical processes such as blast furnaces or direct reduction furnaces. These characteristics include mechanical strength at high temperatures, reducibility, abrasion resistance, porosity, etc.

Cette deuxième étape passe par une phase d'agglomération des minerais sous forme de particules de granulométrie moyenne à partir des fines concentrées. Un de ces procédés dénommé le "bouletage" permet d'obtenir des boulettes de minerai de fer d'un diamètre de l'ordre de 10 mm. Cette transformation est généralement effectuée par les compagnies minières sur les sites d'extraction ou sur les ports d'exportation du minerai, le minerai vendu aux sidérurgistes étant alors un minerai aggloméré en boulette.This second stage goes through a phase of agglomeration of the ores in the form of particles of medium particle size from the concentrated fines. One of these processes, called "pelletizing", makes it possible to obtain iron ore pellets with a diameter of the order of 10 mm. This transformation is generally carried out by the mining companies on the extraction sites or on the ports of export of the ore, the ore sold to the steelmakers then being an ore agglomerated into pellets.

Sur la figure 1 annexée, on a représenté un exemple d'installation connue de bouletage, L'installation comporte une première partie 12 de formation des boulettes crues. Le minerai est mélangé dans des proportions voulues avec certains additifs tels que des fondants, des liants et éventuellement un combustible sous forme de poussier de coke par exemple. A la sortie 14 de la partie 12 de l'installation, on dispose donc de boulettes crues présentant un diamètre convenable, mais une faible résistance mécanique. Les boulettes sont chargées sur un convoyeur d'entraînement (ou grille) 16 en formant un lit d'une épaisseur de l'ordre d'une vingtaine de centimètres. La grille 16 se déplace dans un tunnel 20, dans lequel on crée un courant de gaz chauds obtenus par des brûleurs non représentés sur la figure 1. La grille 16 est constituée par une bande perméable aux gaz, le plus souvent en matériaux métalliques, pour permettre une circulation forcée de gaz chauds à travers le lit de boulettes par l'intermédiaire de ventilateurs non représentés. Le tunnel 20 est séparé en plusieurs zones fonctionnelles qui, elles-mêmes, peuvent être subdivisées en plusieurs étapes. On trouve tout d'abord la zone 22 de séchage dans laquelle l'eau libre présente dans les boulettes est évaporée, puis l'eau de constitution est éliminée à son tour. A la sortie de la zone de séchage, les matières carbonées (fondants) sont calcinées entraînant un échappement de gaz carbonique. Dans la section suivante 24 dite de préchauffage, la circulation d'air dans le lit de boulettes est comparable à celle du sécheur. Le fer sous forme Fe2+ présent est oxydé par l'oxygène présent dans les gaz circulant à travers le lit de boulettes pendant que le lit de boulettes traverse cette section. Cette réaction dégage une quantité de chaleur importante qui s'ajoute à celle apportée par les brûleurs. Lorsque la quantité de Fe2+ présente est insuffisante, du combustible fossile est mélangé au minerai et sa combustion dans cette section de préchauffage compense l'apport de chaleur donnée par l'oxydation dans le cas où la magnétite est majoritaire dans les boulettes. Ces réactions d'oxydation du fer sont très importantes pour la qualité du produit et doivent être terminées avant le frittage du minerai pour obtenir un produit final de bonne qualité. Les réactions de frittage commencent à la fin de la section 24 de préchauffage.In the appended FIG. 1, an example of a known pelletizing installation has been shown. The installation comprises a first part 12 for forming raw pellets. The ore is mixed in desired proportions with certain additives such as fluxes, binders and possibly a fuel in the form of coke dust for example. At exit 14 of part 12 of the installation, there are therefore raw pellets with a suitable diameter, but low mechanical strength. The pellets are loaded on a drive conveyor (or grid) 16 by forming a bed with a thickness of the order of about twenty centimeters. The grid 16 moves in a tunnel 20, in which a stream of hot gases obtained by burners not shown in FIG. 1 is created. The grid 16 consists of a gas-permeable strip, most often made of metallic materials, to allow forced circulation of hot gases through the bed of pellets by means of fans not shown. The tunnel 20 is separated into several functional zones which, themselves, can be subdivided into several stages. First of all, there is the drying zone 22 in which the free water present in the pellets is evaporated, then the water of constitution is eliminated in turn. On leaving the drying zone, the carbonaceous materials (fluxes) are calcined, causing an escape of carbon dioxide. In the following section 24, called preheating, the air circulation in the bed of pellets is comparable to that of the dryer. The iron in Fe2 + form present is oxidized by the oxygen present in the gases circulating through the bed of pellets while the bed of pellets crosses this section. This reaction releases a significant amount of heat which is added to that provided by the burners. When the amount of Fe2 + present is insufficient, fossil fuel is mixed with the ore and its combustion in this preheating section compensates for the heat input given by oxidation in the case where magnetite is predominant in the pellets. These iron oxidation reactions are very important for product quality and must be completed before sintering the ore to obtain a good quality end product. The sintering reactions begin at the end of the preheating section 24.

Les boulettes à la sortie de la section 24 sont chargées, dans ce mode de réalisation, dans un four tournant 26 muni d'un gros brûleur. Les gaz chauds circulent essentiellement transversalement par rapport à la direction de déplacement des boulettes de minerai. Les boulettes sont chauffées par la flamme et le rayonnement des réfractaires constituant le four. Elles sont ainsi maintenues à une haute température durant leur séjour dans le four. C'est durant cette étape qu'a lieu le frittage et la recristallisatîon qui donneront leurs propriétés mécaniques aux boulettes. Dans d'autres installations, la section de chauffage peut être constituée par un prolongement du tunnel analogue à celui qui définit les zones 22 et 24 (chaîne droite).The pellets at the outlet of section 24 are loaded, in this embodiment, into a rotary oven 26 provided with a large burner. The hot gases circulate essentially transversely with respect to the direction of movement of the ore pellets. The pellets are heated by the flame and the radiation of the refractories constituting the oven. They are thus kept at a high temperature during their stay in the oven. It is during this stage that sintering and recrystallization take place which will give their mechanical properties to the pellets. In other installations, the heating section may consist of an extension of the tunnel similar to that which defines zones 22 and 24 (straight chain).

Enfin, l'installation se termine par une zone 28 de refroidisse- ment dans laquelle les boulettes sont refroidies jusqu'à la température ambiante par des circuits 30 de circulation forcée d'air froid à travers le lit de boulettes. Le plus souvent, l'air sortant du refroidisseur est utilisé dans la zone de séchage 22 ou dans le four 26.Finally, the installation ends with a cooling zone 28 in which the pellets are cooled to ambient temperature by circuits 30 for forced circulation of cold air through the bed of pellets. Most often, the air leaving the cooler is used in the drying zone 22 or in the oven 26.

Si la productivité de l'installation est élevée et si le minerai utilisé contient un taux important de magnétite, la réaction d'oxydation n'a pas le temps de se produire convenablement dans la partie préchauffage 24 de l'installation. L'oxydation n'ayant pas lieu dans le four tournant, lorsque l'installation en est équipée, les refroidisseurs terminent cette oxydation et fonctionnent par conséquent comme des fours sur une partie de leur longueur. Les ventilateurs étant limités en capacité, le flux d'air dans les refroidisseurs ne peut être augmenté. La longueur restante pour refroidir la charge n'est plus suffisante, ce qui devient un goulot d'étranglement pour la productivité de l'installation. De plus, le frittage d'une boulette non totalement oxydée dégrade la qualité du produit obtenu. Il est courant de constater une oxydation réalisée à 60 % seulement à la sortie du préchauffage. Par conséquent, il serait très utile à la fois pour la productivité et pour la qualité des boulettes d'augmenter le taux d'oxydation atteint à la sortie du préchauffage sans diminution de productivité ou même avec augmentation de celle-ci. II est à noter que, dans le cas d'une chaîne droite, c'est-à-dire sans four tournant, le problème de l'oxydation dans les refroidisseurs n'existe pas. En revanche, si l'on trouve un moyen d'accélérer celle-ci lors du préchauffage, cela permet tout de même d'augmenter la vitesse globale du procédé et d'améliorer la qualité du produit en réalisant l'oxydation avant le frittage. Ainsi, quel que soit le type d'installation, une amélioration de l'oxydation est souhaitable.If the productivity of the installation is high and if the ore used contains a high rate of magnetite, the oxidation reaction does not have time to take place properly in the preheating part 24 of the installation. As the oxidation does not take place in the rotary kiln, when the installation is equipped with it, the coolers finish this oxidation and therefore operate as ovens over part of their length. As the fans are limited in capacity, the air flow in the coolers cannot be increased. The length remaining to cool the load is no longer sufficient, which becomes a bottleneck for the productivity of the installation. In addition, sintering a not fully oxidized pellet degrades the quality of the product obtained. It is common to see an oxidation performed at only 60% at the end of preheating. Consequently, it would be very useful both for the productivity and for the quality of the pellets to increase the rate of oxidation reached at the outlet of the preheating without reduction in productivity or even with increase thereof. It should be noted that, in the case of a straight chain, that is to say without a rotary kiln, the problem of oxidation in the coolers does not exist. On the other hand, if a way is found to accelerate it during preheating, this still makes it possible to increase the overall speed of the process and to improve the quality of the product by carrying out the oxidation before sintering. Thus, whatever the type of installation, an improvement in oxidation is desirable.

Pour accélérer la réaction d'oxydation, on a proposé d'enrichir en oxygène Pair circulant dans le lit de boulettes. C'est ce qui est proposé notamment dans les documents GB 2 098 190 et US 4313757. Cependant, les quantités d'air mises en jeu sont importantes et le procédé fonctionne avec un gros excès d'air. Les quantités d'O2 à mettre en oeuvre pour enrichir l'air sont donc énormes. De plus, l'équipement n'étant pas étanche, une partie non négligeable de l'oxygène utilisé risque de s'échapper de l'installation avant d'avoir été utilisée pour produire l'oxydation. Bien que l'utilisation d'oxygène apparaisse comme techniquement souhaitable, les techniques mentionnées ci-dessus ont été abandonnées car, avec ces techniques, l'utilisation d'oxygène aboutit à une solution économiquement non viable du fait des quantités mises en jeu.To accelerate the oxidation reaction, it has been proposed to enrich the oxygen circulating in the bed of pellets. This is what is proposed in particular in documents GB 2,098,190 and US 4,313,757. However, the quantities of air involved are significant and the process works with a large excess of air. The amounts of O 2 to implement to enrich the air are therefore enormous. In addition, since the equipment is not waterproof, a non-negligible part of the oxygen used risks escaping from the installation before being used to produce the oxidation. Although the use of oxygen appears to be technically desirable, the techniques mentioned above have been abandoned since, with these techniques, the use of oxygen results in an economically unsustainable solution due to the quantities involved.

Un objet de la présente invention est de fournir un procédé de bouletage qui permette d'améliorer l'oxydation du minerai tout en limitant la consommation d'oxygène nécessaire et donc en maintenant la viabilité économique de l'installation.An object of the present invention is to provide a pelletizing process which makes it possible to improve the oxidation of the ore while limiting the consumption of oxygen required and therefore maintaining the economic viability of the installation.

Pour atteindre ce but selon l'invention, le procédé de bouletage de minerai de fer comprend les étapes suivantes : - on fournit des boulettes constituées par un mélange de minerai de fer et d'additifs,To achieve this object according to the invention, the iron ore pelletizing process comprises the following steps: - pellets are provided consisting of a mixture of iron ore and additives,

- on forme un lit desdites boulettes qui est déplacé dans une installation de traitement comprenant une zone de séchage, une zone de préchauffage et une zone de chauffage, lesdites zones étant alimentées par une circulation à contre-courant de gaz chauds produits en partie par des brûleurs, et une section de refroidissement disposée à la sortie desdites zones ;- A bed of said pellets is formed which is moved into a treatment installation comprising a drying zone, a preheating zone and a heating zone, said zones being supplied by a counter-current circulation of hot gases produced in part by burners, and a cooling section disposed at the outlet of said zones;

- on mesure dans lesdites zones ou portions de zone la température desdits gaz chauds ; - on compare lesdites températures mesurées à une valeur maximale prédéterminée et à une valeur minimale prédéterminée ; et- The temperature of said hot gases is measured in said zones or portions of zones; - said measured temperatures are compared to a predetermined maximum value and to a predetermined minimum value; and

- on injecte, au moins dans certaines desdites zones ou portions de zone pour lesquelles la température mesurée est comprise entre ladite valeur maximale et ladite valeur minimale, de l'oxygène, en en contrôlant le débit, par quoi on améliore sensiblement l'oxydation du minerai de fer contenu dans lesdites boulettes à la sortie desdites zones.- Oxygen is injected, at least into some of said zones or portions of zones for which the measured temperature is between said maximum value and said minimum value, by controlling the flow rate, thereby significantly improving the oxidation of the iron ore contained in said pellets at the exit of said zones.

On comprend que, grâce à la mesure préliminaire de la température dans l'installation, on peut déterminer la ou les portions de zones de celle-ci dans lesquelles la température est comprise entre les valeurs maximales et minimales et limiter l'injection d'oxygène à ces zones ou portions de zone. Ces valeurs maximales et minimales sont respectivement de l'ordre de 1 300°C et 600°C et de préférence encore 1 100°C et 850°C.It is understood that, by means of the preliminary measurement of the temperature in the installation, it is possible to determine the portion or portions of zones thereof in which the temperature is between the maximum and minimum values and to limit the injection of oxygen. to those zones or portions of zones. These maximum and minimum values are respectively of the order of 1300 ° C and 600 ° C and more preferably 1100 ° C and 850 ° C.

Il a été mis en évidence par les inventeurs que c'est dans cette plage de températures que l'effet de l'excès d'oxygène sur l'oxydation du minerai de fer avait le meilleur rendement. On comprend qu'en localisant l'injection d'un excès d'oxygène, on limite la consommation de ce gaz tout en améliorant la performance de l'installation de bouletage.It has been demonstrated by the inventors that it is in this temperature range that the effect of excess oxygen on the oxidation of iron ore has the best yield. It is understood that by localizing the injection of an excess of oxygen, the consumption of this gas is limited while improving the performance of the pelletizing installation.

Un deuxième objet de l'invention est de fournir une installation notamment pour la mise en oeuvre du procédé défini. L'installation de bouletage pour le traitement de boulettes de minerai constituées par du minerai et des additifs comprend :A second object of the invention is to provide an installation, in particular for implementing the defined method. The pelletizing plant for the processing of ore pellets consisting of ore and additives comprises:

- une zone de séchage, une zone de préchauffage, une zone de chauffage et une section de refroidissement, des moyens pour déplacer un lit desdites boulettes dans lesdites zones et dans ladite section, lesdites zones et ladite section étant équipées de moyens de chauffage et de circulation de gaz chaud ;a drying zone, a preheating zone, a heating zone and a cooling section, means for moving a bed of said pellets in said zones and in said section, said zones and said section being equipped with heating means and circulation of hot gas;

- des moyens pour mesurer la température dans lesdites zones ou dans des portions desdîtes zones,means for measuring the temperature in said zones or in portions of said zones,

- des moyens pour comparer les températures mesurées à une valeur maximale prédéterminée et à une valeur minimale prédéterminée,means for comparing the temperatures measured with a predetermined maximum value and with a predetermined minimum value,

- des moyens pour alimenter en oxygène, en en contrôlant le débit, au moins certaines desdites zones ou portions de zone pour lesquelles la température mesurée est comprise entre ladite température maximale et ladite température minimale. D'autres caractéristiques et avantages de l'invention apparaîtront mieux à la lecture de la description qui suit de plusieurs modes de mise en oeuvre de l'invention donnés à titre d'exemples non limitatifs. La description se réfère aux figures annexées, sur lesquelles :- Means for supplying oxygen, by controlling the flow rate, at least some of said zones or portions of zone for which the measured temperature is between said maximum temperature and said minimum temperature. Other characteristics and advantages of the invention will appear better on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the appended figures, in which:

- la figure 1 , déjà décrite, montre une installation de bouletage selon l'état de la technique ;- Figure 1, already described, shows a pelletizing installation according to the prior art;

- la figure 2 montre une installation de bouletage conforme à l'invention ;- Figure 2 shows a pelletizing installation according to the invention;

- la figure 3 montre des courbes expérimentales donnant le taux final d'oxydation du fer en fonction de la température maximale pour différentes teneurs en oxygène ; et - la figure 4 montre des courbes expérimentales donnant la vitesse d'oxydation en fonction de la température maximale.- Figure 3 shows experimental curves giving the final rate of iron oxidation as a function of the maximum temperature for different oxygen contents; and - Figure 4 shows experimental curves giving the oxidation rate as a function of the maximum temperature.

Ainsi qu'on l'a déjà exposé succinctement, le procédé de bouletage consiste à utiliser une installation de bouletage du même type que celle déjà utilisée mais, dans une première étape, on détermine les températures durant la phase de fonctionnement normal de l'installation dans les zones notamment de séchage 22, de préchauffage 24 et éventuellement de chauffage 26. Pour cela, de préférence, chacune de ces zones est équipée de plusieurs capteurs de température tels que C1 , C2, ... C6 qui sont montés dans la zone de séchage, dans la zone préchauffage et éventuellement dans la zone de chauffage constituée par le four tournant 26. Ces températures sont fournies à une installation de traitement 40 qui effectue la comparaison entre les températures mesurées par les différents capteurs Ci et les températures maximales et minimales prédéterminées correspondant aux régions de températures les plus favorables pour produire l'oxydation par un excès d'oxygène.As already explained briefly, the pelletizing process consists in using a pelletizing installation of the same type as that already used but, in a first step, the temperatures are determined during the normal operating phase of the installation. in the zones in particular for drying 22, for preheating 24 and possibly for heating 26. For this, preferably, each of these zones is equipped with several temperature sensors such as C1, C2, ... C6 which are mounted in the zone drying, in the preheating zone and possibly in the heating zone formed by the rotary kiln 26. These temperatures are supplied to a treatment installation 40 which compares the temperatures measured by the various sensors Ci and the maximum and minimum temperatures predetermined corresponding to the most favorable temperature regions to produce oxidation by an excess of oxygen born.

Comme on l'a déjà indiqué, les plages de températures sont de 600 à 1 300°C et de préférence de 850 à 1 100°C, ce dernier intervalle de températures correspondant à l'énorme majorité des minerais à traiter. Les figures 3 et 4 montrent des courbes enregistrées lors d'essais isothermes en laboratoire. Un échantillon de minerai est chauffé à une température T sous atmosphère inerte. Cette température, une fois stabilisée, est conservée constante tout le long de l'essai. L'échantillon est alors soumis à une atmosphère composée d'azote et d'oxygène et dont la teneur en oxygène est contrôlée. La variation de masse résultant de l'oxydation du minerai par l'oxygène de l'atmosphère est enregistrée en fonction du temps afin de suivre quantitativement le phénomène.As already indicated, the temperature ranges are 600 to 1,300 ° C and preferably 850 to 1,100 ° C, the latter temperature range corresponding to the vast majority of the ores to be treated. Figures 3 and 4 show curves recorded during isothermal laboratory tests. A sample of ore is heated to a temperature T under an inert atmosphere. This temperature, once stabilized, is kept constant throughout the test. The sample is then subjected to an atmosphere composed of nitrogen and oxygen and the oxygen content of which is controlled. The change in mass resulting from the oxidation of the ore by atmospheric oxygen is recorded as a function of time in order to quantitatively follow the phenomenon.

Les courbes représentées sur la figure 3 fournissent le taux d'oxydation finale du minerai en fonction de la température maximale dans laquelle est placé le minerai pour des taux d'injection d'oxygène de 15 % (A), 18 % (B), 21 % (C) et 23 % (D). On voit que ces courbes présentent une zone d'oxydation maximale dans la plage de 700°C à 1 300°C.The curves shown in FIG. 3 provide the final oxidation rate of the ore as a function of the maximum temperature in which the ore is placed for oxygen injection rates of 15% (A), 18% (B), 21% (C) and 23% (D). It can be seen that these curves have a maximum oxidation zone in the range from 700 ° C to 1300 ° C.

Les courbes de la figure 4 donnent la vitesse d'oxydation moyenne du minerai en mol.g"1. s"1 en fonction de la température maximale pour quatre teneurs en oxygène. Ces courbes rendent compte de la "vitesse d'oxydation" qui présente un maximum dans la zone de température allant de 800°C à 1 200°C.The curves in FIG. 4 give the average oxidation speed of the ore in mol.g "1. S " 1 as a function of the maximum temperature for four oxygen contents. These curves reflect the "oxidation rate" which has a maximum in the temperature range from 800 ° C to 1200 ° C.

Le choix des plages de températures 600°C à 1 300°C et de préférence de 850°C à 1 100°C résulte d'un compromis entre les résultats correspondant à ces deux séries de courbes.The choice of temperature ranges from 600 ° C to 1,300 ° C and preferably from 850 ° C to 1,100 ° C results from a compromise between the results corresponding to these two series of curves.

Après cette étape de comparaison, on détermine les portions de zone dans lesquelles cette plage de température est atteinte, zones ou portions de zone où l'on doit procéder à l'injection d'oxygène. Après cette phase préliminaire d'acquisition d'information, on équipe les zones ou portions de zones d'injecteurs d'oxygène tels que 11 et 12 qui, dans l'exemple particulier montré sur la figure, sont disposés dans la zone de préchauffage 24. Ces injecteurs sont reliés à une source d'oxygène 44 par l'intermédiaire d'un système approprié. La commande de ces vannes aux moyens analogues permet de régler le débit d'oxygène en fonction d'informations complémentaires telles que la teneur en oxygène dans l'air, etc., qui sont fournies par d'autres capteurs tels que K1, K2, etc. Les indications fournies par ces capteurs et transmises à l'ensemble de traitement 40 permettent d'adapter le débit d'oxygène dans les différentes zones ou portions de zones de l'installation de bouletage. On comprend que, dans le cas où l'installation comporte un four tournant 26, l'injection d'oxygène soulève des problèmes spécifiques et cette solution ne sera adoptée que dans des cas particuliers. En revanche, lorsque la zone de chauffage est une extension de la zone de préchauffage, l'injection d'oxygène pourra être réalisée dans la zone de chauffage si les températures des gaz dans cette zone sont comprises dans les plages' mentionnées ci-dessus. After this comparison step, the portions of the zone in which this temperature range is reached are determined, zones or portions of zone where the oxygen injection must be carried out. After this preliminary phase of information acquisition, the zones or portions of zones of oxygen injectors such as 11 and 12 are fitted, which, in the particular example shown in the figure, are arranged in the preheating zone 24 These injectors are connected to an oxygen source 44 via an appropriate system. The control of these valves by analogous means makes it possible to adjust the oxygen flow rate as a function of additional information such as the oxygen content in the air, etc., which is supplied by other sensors such as K1, K2, etc. The indications provided by these sensors and transmitted to the treatment unit 40 make it possible to adapt the oxygen flow rate in the different zones or portions of zones of the pelletizing installation. It is understood that, in the case where the installation comprises a rotary oven 26, the injection of oxygen raises specific problems and this solution will only be adopted in special cases. On the other hand, when the heating zone is an extension of the preheating zone, the oxygen injection can be carried out in the heating zone if the temperatures of the gases in this zone are included in the ranges' mentioned above.

Claims

REVENDICATIONS 1. Procédé de bouletage de minerai de fer comprenant les étapes suivantes : - on fournit des boulettes constituées par un mélange de minerai de fer et d'additifs,1. A method of pelletizing iron ore comprising the following steps: - pellets consisting of a mixture of iron ore and additives are supplied, - on forme un lit desdites boulettes qui est déplacé dans une installation de traitement comprenant une zone de séchage, une zone de préchauffage et une zone de chauffage, lesdites zones étant alimentées par une circulation de gaz chauds produits en partie par des brûleurs, et une section de refroidissement disposée à la sortie desdites zones ;- A bed of said pellets is formed which is moved in a treatment installation comprising a drying zone, a preheating zone and a heating zone, said zones being supplied by a circulation of hot gases produced in part by burners, and a cooling section arranged at the outlet of said zones; - on mesure dans lesdites zones ou portions de zone la température desdits gaz chauds ;- The temperature of said hot gases is measured in said zones or portions of zones; - on compare lesdites températures mesurées à une valeur maximale prédéterminée et à une valeur minimale prédéterminée en fonction du minerai traité ; et- said measured temperatures are compared to a predetermined maximum value and to a predetermined minimum value as a function of the ore processed; and - on injecte, au moins dans certaines desdites zones ou portions de zone pour lesquelles la température mesurée est comprise entre ladite valeur maximale et ladite valeur minimale, de l'oxygène, par quoi on améliore sensiblement l'oxydation du minerai de fer contenu dans lesdites boulettes à la sortie desdites zones.- Oxygen is injected, at least into some of said zones or portions of zones for which the measured temperature is between said maximum value and said minimum value, whereby the oxidation of the iron ore contained in said is substantially improved pellets at the exit of said zones. 2. Procédé de bouletage selon la revendication 1, caractérisé en ce que ladite température maximale est égale à 1 300°C et ladite température minimale égale à 600°C. 2. Pelletizing method according to claim 1, characterized in that said maximum temperature is equal to 1300 ° C and said minimum temperature equal to 600 ° C. 3. Procédé de bouletage selon la revendication 1 , caractérisé en ce que ladite température maximale est égale à 1 100°C et la température minimale est égale à 850°C.3. Pelletizing method according to claim 1, characterized in that said maximum temperature is equal to 1100 ° C and the minimum temperature is equal to 850 ° C. 4. Installation de bouletage pour le traitement de boulettes de minerai constituées par du minerai et des additifs comprenant : - une zone de séchage, une zone de préchauffage, une zone de chauffage et une section de refroidissement,4. Pellet plant for the treatment of ore pellets consisting of ore and additives comprising: - a drying zone, a preheating zone, a heating zone and a cooling section, - des moyens pour déplacer un lit desdites boulettes dans lesdites zones et dans ladite section, lesdites zones et ladite section étant équipées de moyens de chauffage et de circulation de gaz chauds ; - des moyens pour mesurer la température dans lesdites zones ou dans des portions desdites zones, - des moyens pour comparer les températures mesurées à une valeur maximale prédéterminée et à une valeur minimale prédéterminée,- Means for moving a bed of said pellets in said zones and in said section, said zones and said section being equipped with means for heating and circulation of hot gases; means for measuring the temperature in said zones or in portions of said zones, means for comparing the temperatures measured with a predetermined maximum value and with a predetermined minimum value, - des moyens pour alimenter en oxygène, en en contrôlant le débit, au moins certaines desdites zones ou portions de zone pour lesquelles la température mesurée est comprise entre ladite température maximale et ladite température minimale.- Means for supplying oxygen, by controlling the flow rate, at least some of said zones or portions of zone for which the measured temperature is between said maximum temperature and said minimum temperature. 5. Installation selon la revendication 4, caractérisée en ce que ladite température maximale est égale à 1 300°C et ladite température minimale est égale à 600°C. 5. Installation according to claim 4, characterized in that said maximum temperature is equal to 1300 ° C and said minimum temperature is equal to 600 ° C. 6. Installation selon la revendication 4, caractérisée en ce que ladite température maximale est égale à 1 100°C et ladite température minimale est égale à 850°C. 6. Installation according to claim 4, characterized in that said maximum temperature is equal to 1100 ° C and said minimum temperature is equal to 850 ° C.
PCT/FR2002/000063 2001-01-10 2002-01-09 Method for pelletization of iron ore Ceased WO2002055745A1 (en)

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BR0206399-9A BR0206399A (en) 2001-01-10 2002-01-09 Iron Ore Ball Production Process
AU2002233406A AU2002233406B2 (en) 2001-01-10 2002-01-09 Method for pelletization of iron ore
CA002433853A CA2433853A1 (en) 2001-01-10 2002-01-09 Method for pelletization of iron ore

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FR0100268A FR2819267B1 (en) 2001-01-10 2001-01-10 IRON ORE BALLING PROCESS
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2785063A (en) * 1951-11-17 1957-03-12 Oglebay Norton And Company Temperature control system and method
US4313757A (en) * 1976-08-06 1982-02-02 Union Carbide Corporation Process for upgrading iron ore pellets
US4473519A (en) * 1980-02-13 1984-09-25 Estel Hoogovens B.V. Method of agglomeration of fly ash into pellets
EP0602880A1 (en) * 1992-12-18 1994-06-22 Mark Cross Treatment of iron ore

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2785063A (en) * 1951-11-17 1957-03-12 Oglebay Norton And Company Temperature control system and method
US4313757A (en) * 1976-08-06 1982-02-02 Union Carbide Corporation Process for upgrading iron ore pellets
US4473519A (en) * 1980-02-13 1984-09-25 Estel Hoogovens B.V. Method of agglomeration of fly ash into pellets
EP0602880A1 (en) * 1992-12-18 1994-06-22 Mark Cross Treatment of iron ore

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