GB2118921A - Method and apparatus for the production and use of compact nodules for metal production - Google Patents

Abstract

The invention provides an improved production process for self- reducing and self-fluxing compact nodules which are a mixture comprising 50% to 85% (by weight) metallic oxides, a quantity of coal, charcoal, coke or a mixture thereof, which lies in the range of 1 to 2 times that stoichiometrically required for oxide reduction, and 2 to 10% (by weight) cement and an installation for the production of metal in metallurgical furnaces. The compact nodules can be coated with a thin binder and oxide layer which increases their mechanical resistance and decreases their friability, as well as improving their characteristics within a furnace.

Description

SPECIFICATION Methods and apparatus for the production and use of compact nodules for metal production The invention relates to a method and apparatus for the production and use of compact nodules for metal production and particularly to a production process for self-reducing and selffluxing compact nodules of metal oxide and the equipment for the production of metal in metal lurgical furnaces.

It is known that agglomeration processes play a significant role in the application of natural ore fines and the use of fines resulting from industrial rejects.

The main agglomeration processes comprise bricketting, roasting and production of nodules or pellets which latter has found increasing favour in production all over the world due to its being easy to obtain and the product quality. We would emphasize the cost savings and efficiency obtained in the reducing furnace.

With evolution of nodule production technology, it was possible to obtain modified products with special properties, which enable their use in other reducing processes besides the traditional use in blast furnaces. Developments took place using modified agglomerates starting from classic pellets made only of ore fines and binder (bentonite being commonly used). Selffluxing pellets, for instance are modified agglomerates, containing a proportion of limestone as well as ore and binder. The limestone, besides acting as a flux increases the resistance of the calcinated nodules. Another possibility, according to Brosch in ABM-Bulletin, September 1966, is the use of dolomite, which led to good mechanical characteristics, even when added in low percentages (0.51%).

Other pellets are self-reducing pellets containing a proportion of reductor in addition to the traditional constituents, e.g. coke or coal fines, or even tar and pitch. It should be noted that the latter act as binders as well and may take the place of bentonite, at least partially.

In 1963, the IPT (Technology Research Institute), located in Sao Paulo, Brazil, experimented using self-reducing pellets, using charcoal as a reductor for the first time. The pellets made of iron ore, charcoal and with tar as a binder had approximately 15 mm diameter and were used in cupola. It was noted that the compression resistance of nodules to be used in cupola operation need not be as high as that of nodules for blast furnaces.

Other experiments with self-reducing agglomerates using pellets as well as brickettes in cupola were made. According to Goksel AFS Transactions 1 977, the resistance of this uncured or even undryed material would be insufficient.

Thus problems would arise during the transportation, handling and reducing in the cupola, e.g. agglomeration break and projection of fines with the exhausting gases.

For this reason, the production of high resistance self-reducing and self-fluxing nodules has been studied at the Michigan Technology University, U.S.A., since 1 960 where they succeeded in developing a hot cure agglomeration process called "MTU".

Besides iron ore fines and concentrates, the MTU nodules or pellets may utilize oxide wastes from siderurigical plants as iron scales, melting furnace dust mixed with coke, limestone and silica fines.

The MTU uncured nodules formed in pelletizers are screened and dried and later they are cured in an autoclave typically for 1-2 hours at 21 atm pressure-or at lower pressures for a longer period. Due to the dehydration of gel-like calcium silicate it is necessary to perform final drying in order to increase the product resistance.

The MTU nodules are, therefore, produced by a sophisticated process including autoclaving treatment (necessary to get a high resistance material). The process is a thermosetting process with a high consumption of energy.

It is emphasized that the nodules made by the MTU process have a reductor quantity (coke) more than twice that stoichiometrically required to reduce the iron oxide (magnetite concentrate).

Consequently, for this reductor quantity used we would have pellets with low iron percentages.

In this nodule production process there is a considerable energy waste for drying and calcination. This energy is normally supplied by burning large quantities of oil. The investment required for drying and calcination furnaces is also high.

To reduce fuel consumption we have tried to develop agglomerates in which arrangements for drying and calcination could eventually be omitted during the manufacture of the pellets.

The researches made by Grangesberg Company in Sweden relating to the production of traditional nodules cured by means of chemical reactions at low temperatures are outstanding.

These chemical reactions present physical and metallurgical properties suitable for application in shaft furnaces as well as in electric furnaces. This process enables smaller investment costs compared to the traditional processes minimizing the operational costs (due to lower fuel consumption), energy, manpower, and other inputs.

According to Martins-ABM Annual Congress, 1980, the application of cold bonded agglomerates e.g. cement has been known for more than 60 years since iron ore brickettes made with this binder were patented in Germany. In the beginning there were difficulties due to the adherence of wet nodules. The Grangcold process which uses binders such as Portland cement and/or pozzolanic cement for the production of cold cured pellets was then developed.

The binder used (which amounts to 10% by weight), is of Portland cement clinker and granulated and dried blast furnace slag in the ratio of 3:2.

The efficiency of the self-reducing and self fluxing pellets is due to their characteristics which strongly foster their almost complete reduction in a short time (15 to 30 minutes). With this kind of nodule, the iron ore, the reductor and the finely divided fluxing materials are in close contact and in this way there are favourable conditions for the reduction at high temperatures rapidly.

The normal pellets in contact with the reducing gas are first reduced on their surface and afterwards the carbon monoxide of the reducing gas diffuses into the nodule and progressively reduces the iron oxide therein. The reduction at the centre requires more time to complete than that on the surface of the nodule and the nodule must spend more time in the furnace. It should be noted that high porosity indexes of the pellets and larger surface contacts between pellet and gas are also required. This clearly shows the need to use small diameter nodules and a strongly reducing gas.

The use of self-reduction pellets enables uniform distribution and wide contact surfaces between reductor particles and iron oxide, allowing the occurrence of the reaction Fe203+3Co2Fe+3CO in the interior of the pellets at high temperatures.

The generated CO reacts later in the interior of the pellets themselves- Fe203+3COo2Fe+3c02 Consequently, by the above-mentioned reactions it is possible to obtain quicker metallization and nodule melting in a shaft furnace, as for example in the cupola and blast furnace.

Self-reducing pellets have already been used in cupola furnaces to produce liquid metal. In work by Brosch at the IPT, the pellets were dried at 4000C for 4 hours, and showed 50% iron and 25% carbon by weight.

The experimental cupola of the IPT used in two runs had a 220 mm diameter and modified tuyeres. The operation was begun with a pig iron charge, using later mixed charges of pig iron and nodules and still later a charge of nodules only.

The specific consumption of coke was 303 kg per pig iron ton, and a metallization index, e.g. the relation between the metallic iron content and total iron was 88.5% at the first run and 90.4% in the second. The coke consumption was considered high in relation to a usual pig iron charge which would normally be about 1 50 kg of coke per pig iron ton. The output of metallic recovery obtained during the melting could be improved if the content of FeO in the slag (37.9% in the first run and 1 6% in the second run) and also the relative volume of slag (17.3% in the first run and 13% in the second run) were reduced by using purer raw materials in making the nodules.

Goksel-AFS Transactions 1 977 also describes experiments related to the application of self-reducing pellets in cupolas and produced by the MTU process. These tests were made in experimental modified cupola with 220-300 mm diameter, refractory coated and with water jacket refrigeration, as well as with three rows of tuyeres and not blast blowing in the lower rows.

Oxygen blowing to improve the furnace performance was also used.

The furnace was normally operated with nodule percentages of 75% to 100% in four runs, obtaining cast irons of different compositions due to the charges used. In this way, e.g. using 100% pellets in the charge, the final composition was 2.58% C, 0.15% Si, 0.10% Mn, 0.06% P and 0.37% S.

The noted work also described an experiment in a 1 500 mm diameter industrial cupola with a 1 2 t/h nominal capacity, with two rows of tuyeres, using 5% of MTU pellets in the charge during three hours of operation. The use of this quantity of nodules did not change the furnace operation conditions; the metal temperature at the spout remained at 1 510-1 540 C, and no changes in the chemical composition of the cast iron or in the slag viscosity could be observed.

Rehder in Iron and Steel Engineer-May 1 980, mentioned other experiments using an industrial, modified cupola with 1 500 mm diameter and height load column (7.60 to 9.00 m) optimized due to the brickette size (which were spherical with 50-100 mm diameter). Hot blast and oxygen enrichment in the furnace with 2 or 3 rows of tuyeres was used, with a charge of almost 100% self-reducing and self-fluxing nodules. Only small scrap quantities were used to adjust the furnace operation.

The output found using a charge exclusively of nodules was of 4 to 5 t/h, which is rather low for a cupola of 1 500 mm diameter. It is noted in this work however, that by increasing the carbon content in the agglomerates or by adding steel scrap or cast iron return to the charge, increases in productivity would be obtainable.

In another paper, in Foundry MìTApril 1980 the author tells us that by using a cupola with two rows of tuyeres and charge with 100% self reducing pellets it would be possible to obtain only 25% of the productivity in relation to a common furnace, i.e. which operates with pig iron, steel scrap and cast iron return. In order to reach the same production per hour it would be necessary to use a cupola with twice the diameter.

In Brazilian patent application 004.500/74, Obenchain describes a process for producing metal in cupola starting from metal oxide nodules containing carbonaceous material in sufficient quantity to reduce the metal oxide by means of traditional coke bed on the bottom of the cupola and successive pellets and coke layers and fluxing agents on them. Up to 3 rows of tuyeres in the furnace are used and eventually oxygen enrichment as well.

According to one aspect the invention provides compact nodules for metal production comprising a mixture of oxides, reductors and agglomerants, wherein the mixture comprises 50% to 85% (by weight) metallic oxides, a quantity of reductors, being coal, charcoal, coke or a mixture thereof, which lies in the range of 1 to 2 times that stoichiometrically required for oxide reduction, and 2 to 10% (by weight) cement.

According to a second aspect the invention provides a process for making compact nodules which the process is characterised by the nodules being obtained via successive impacts on a pelletising disc border.

Embodiments of the invention provide selfreducing and self-fluxing cold hardened compact nodules covered with a resistant coating which increases their mechanical resistance, their abrasion resistance (reducing their friability), promotes chemical reactions within them and which is an improvement over the known nodules. The nodules may be used in different kinds of metallurgical furnaces to produce metal, such as pig iron or low carbon content iron alloys.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a flow diagram showing the production of nodules in accordance with the invention and Figure 2 illustrates diagrammatically a blast furnace.

Reductor materials (R) are received and stocked in a covered shed in, a specific area, before they are ground in a ball mill to a size less than 70 mesh and passed by a conveyor 2 for stocking in bins 3. The reductor material is carried pneumatically from bins 3, by conveyors 4, to bins 11 in a mixing preparation unit.

Agglomerants A are received and stocked in bins 5 from which they are fed by pneumatic conveyors 6 to the bins 11.

Oxide fines F are received and eventually ground in a ball mill 7 so that 80% of the fines (by weight) are smaller than 70 mesh. The ground fines are carried by a pneumatic conveyor 8 to intermediate storage bins 9, from which they are carried as required to bins 11 by pneumatic conveyor 1 0. At the start of operation the bins are loaded with ground oxide; as the oxide fine bins are emptied, they are also charged with nodules on the top, thereby avoiding the disintegration of agglomerates which are charged there but are still uncured (green nodules).

The reductor, binder and iron oxide are carried from bin 11 to two continuous mixers 12, in which preparation of the mixture to be agglomerated is effected and in which part of the humidifying water for the mixture is added. This water is added in a quantity which may be up to 10% (by weight) of the mixture. The homogenized and premoistened mixture is continually discharged from mixers 12 to disc nodulizers 15, which form and then discharge nodules to a set of sieves 16, and 1 7 which retain nodules larger than 12-mm diameter and smaller than 35-mm diameter. The material not held in the sieves is automatically fed back to nodulizer 1 5.

In the disc noduliser 1 5 the agglomerating operation to form nodules is performed with mixtures of oxides, binders, reductors and an additional 20% water fed to discs 1 5.

The nodules in the sieves may be coated with a thin layer of a binder/water suspension and oxide fines, as already described, by dipping in tanks 1 3 or by spray coating 14.

After coating the nodules are carried by a belt conveyor system 22 to curing bins 1 9 where they are cured for 1 5 to 45 days at room temperature.

After this time, the nodules have the mechanical resistance to friability to enable their proper use in different types of metallurgical furnaces.

The nodules embodying the invention are preferentially of iron oxide or pyrite ash iron oxide, natural or ground iron ore fines, fines obtained by collection of siderurgical and metallurgical furnace dust in general, mill scale and mixtures of such oxides in any proportion: of reductor agents such as different kinds of coal (including those with high ash content like steam coal), different kinds of charcoal and different types of cokes, employed separately or mixed together in any proportion: and of an agglomerant such as blast furnace Portland cement, pozzolanic Portland cement, common Portland cement, coal ashes with pozzolanic properties and mixtures thereof.

These constituents appear in the nodules in the sieves 16 and 1 7 in quantities which vary from: metallic oxides 50% to 85% in weight reductors 1-2 times the stoichio metric quantity for oxide reduction binders 2 to 10% (by weight) These cold hardening self-reducing compact nodules, in spite of having a good mechanical resistance, are somewhat friable and because of this the coating process for these nodules is utilized. The coating process improves the friability characteristics of the nodules, and their mechanical resistance.

The coating is made with a thin layer of water suspension of a binder such as cement, lime, bentonite and sodium silicate, used separately or mixed together in any proportion with iron oxide fines.

Such constituents appear in the water suspension in the following quantities: binder 5 to 50% (weight) oxide fines up to 30% (weight) As it can be seen from the above figures not only the nodules but also the covering has characteristics which differ from those previously available. The differences relate to the used reductor quantity (which is less than the quantity used for pellets previously developed) and this increases the nodule content of iron, and the quantities of binders are less than those used in the known processes, increasing the iron oxide quantity in the nodules and decreasing its cost considerably.

The surfaces of coated nodules are sub stantially different from the surfaces of the known self-reducing or non self-reducing pellets.

They are not regular round shapes, are not manufactured aiming a high porosity and are inclusive manufactured with continuous drops on the disk border, which assures a proper mechanical compactibility and resistance necessary for a good action of the agglomerant present in low percentages. Therefore, they may be used in several metallurgical furnaces applied to the production of metal from its oxide.

An example of typical composition with steam coal is 71% (weight) of iron oxide, 23% (weight) of steam coal, which has about 40% (weight) of ashes and 6% (weight) of cement.

Naturally, depending on the quantity of the self-reducing nodules used as constituent of the furnace charge, the final sulphur content of the metal shall be verified once a desulfuration treatment of the metal due to the high sulphur content in the steam coal (about 3% by weight of sulphur) may be necessary.

Besides these aspects, production of pig iron should be emphasized, as it is one of the most important steps in siderurgy.

Traditionally, the primary siderurgical product, pig iron (primary metallic iron) is obtained from blast furnaces which are operated by generating a reducting atmosphere within the furnace. This atmosphere causes an iron oxide charge to convert to metallic iron, and is obtained by the incomplete combustion of a coke. The coke in its turn, is obtained by coking a mixture of appropriate coals, so called coking coals.

In the classical production of pig iron in a blast furnace (with coke or charcoal) operation is according to the following model A reducing gas is generated at the bottom of the furnace by means of the hot gas blast injection, dosed for the incomplete combustion of coke which is supported in layers together with the metallic charge made up of natural ore or agglomerates (pellets or sinter material) or mixture thereof.

The reducing gas generated permeates the oxide charge within the furnace passing from bottom to top, and giving up to it heat generated by the exothermic coke gasification reaction (2C+O2-2CQ) and in successive stages reacting from reduction in counter current to its complete metallization and melting. Figure 2 depicts a classical blast furnace with the different reducing stages.

The furnace shown in Fig. 2. comprises a housing 40 into which the charge is put. Hot air (at 12000C) is pumped into housing 40 at 41 from blowers 42. Within the housing the charge is reduced. Starting from the top of housing 40 the charge is inserted at 43. The oxides are preheated at 44 as they move down the chamber 40. At 45 the oxide is starting to be reduced and at 46 the oxide is premetallized. At 47 is a solid-metai phase with residual oxides and incipient carburizing. The molten metal saturated with carbon 48 is taken from the housing 40 in the usual way as is the slag 49. The gases fed to housing 40 are simply heated air (12000C) and the gas leaving the top of the housing has been found to comprise 52% N2,22% CO, 24% CO2 and 2% H20 and others, and be at a temperature of2500C.

The technological method used presently is dependent on the gas-solid interaction and its efficiency is limited by the reaction kinetics involving the particles and the furnace atmosphere.

Firstly the reducing activity of the gas phase is small as it is obtained by coke gasification to generate CO using preheated air, injected via the tuyeres. Even if the injected air is enriched with oxygen the generated gas has a reducing fraction (CO+H2) of approximately only 50% (by volume) of the total gas flow within the furnace. This factor diminishes the partial pressure of the reducing phase and, as a consequence, its efficacy.

Secondly the natural ore reactivity, especially of the denser and purer ores such as Brazilian ores, is also naturally low. This fact caused successive developments over the last twenty to thirty years which culuminated in the generalized production of sinters and pellets. Blast furnaces in modern siderurgical plants are generally charged only with sinters and pellets, and not with ore. In spite of the efforts on charge preparation including particle size limitation and fine elimination, at most only slightly more than 50% of the reducing power of the gas in a blast furnace is used. There is therefore significant energy loss even if use is made of part of this energy to preheat the injected air and elsewhere in the plant.As blast furnace gas has a low calorific value (about 750 kcal/Nm3) because of the high N2 content (from the input air) its application in reheating furnaces is characteristic for the siderurgical industry and also expensive, presenting a low thermal output which makes its salvage almost impossible.

The low reactivity of traditional blast furnaces is explained by the high dilution of the reducing gas fraction in N2 from the combustion air and the difficulties of the gassy phase in permeating the micropores of the agglomerates or ore and reaching its nucleus to promote metallization of the particle which is the object of the process.

As a result of these problems it is necessary for the particle (sinter, pellet or ore) to remain in the reduction furnace for a long time, e.g. a period of 6-7 hours in passing from top to bottom of the furnace. The low utilization of the reducing gas phase also leads to a high coking rate (about 500 kg/t of produced pig iron). These two factors lead to a low volumetric output for the equipment and wasted energy.

The method now proposed aims to avoid these problems and represents a radical change in the philosophy of blast furnace operation process control. The proposal now made is that cold bound semi- (or) self-fluxing and self-reducing nodules are used to charge the furnace. With its metallic charge made up in this way the blast furnace will be operated in a neutral or slightly oxidising atmosphere, the injected air effecting the complete combustion to coke to generate CO2. The carbon atoms needed to reduce the metals oxide are introduced to the nodules when they are being prepared from the agglomerated mass, and the limitation to higher productivity of blast furnaces-the difficult penetration of the reducing atom to the particle nucleus-is removed.In this way, reduction occurs quickly (in little more than 1 5 minutes once the thermal level of 9000C necessary for direct reduction of Fe203 through the carbon is reached) due to the reductor uniform distribution in the agglomerated mass.

The above examples show the difficulty in reducing an oxide particle, for instance a common nodule, passing through a blast furnace reducing atmosphere.

First the hindrance that the CO molecules already diluted in N2 have in penetrating the micropores of a pellet or of a sinter to react with the oxide of the internal layers of the pellet or sinter. Therefore, whilst the reaction in the outer layer of the particle readily takes place the reaction speed decreases exponentially with successively deeper layers of the nodule, requiring high permanence times in the blast furnaces (about 6-7 hours, as already mentioned). As a result almost half of the reducing gas leaves the furnace without reacting, the proportion expressed by the relation CO/CO2 at the top of the present furnaces being about 1:1.The proportion of gases leaving the present furnaces is: CO 22% CO2 24% H2 52% H20+others 2% The low reactivity of natural ore charges and the inconveniences caused by fines has lead to the development of iron ore agglomerates for use in substitution for natural ore. The evolution of external charge preparation, and its conditioning for optimisation of gas permeability led to the great "coking rate" reductions in blast operation which became known two decades ago. The possibilities of further advances in this area however, are thought to be almost exhausted.

The investment and production costs relating to blast furnace charge preparation, i.e. the use of sinter or pellet in place of natural ore is known in siderurgical production. However, the present invention provides a particle which is permeable to a reducing gas and which guarantees a proper charge permeability to the gas due to its size uniformity and the lack of fines. In other words, we aim to optimize the gas-solid model.

The proposed method eliminates the reducing gas-solid model, which is replaced by the formation of a particle already containing carbon atoms needed for reduction and acts as an individually reactive dosed package. The particle itself becomes the reduction environment, and not the solid phase-gas phase within the furnace.

The reduction is autogeneous and for that reason called self-reduction.

.The results of these changes in the process are very important.

The furnace acts only as a melting furnace in which coke is completely burnt to form CO2 and it is not necessary to maintain a reducing atmosphere in the furnace. The CO2 dissolves in the N2 present in the air which, together with the presence of a small amount of coke particles in the charge and an excess of air, reduces to a minimum the reversion of CO2 to CO.

The coke requirements for metal and scrap melting and for reaction heat involved in the oxide reduction with embodiments of this invention are about 1 50 to 250 kg/t of produced metal rather than the 500 kg/t requirement of the known processes.

Again the residence time of the particles in the furnace is reduced compared with the known processes now that reduction is an autogenous process. The reduction progresses very rapidly from the periphery to the nucleus of the nodule, decreasing the residence time from 6-7 hours to no more than 2 hours. The time limitation is a function of the rate at which heat can pass from the gas to the materials allowing a doubling of the capacity of known processes. The carbon needed for the reduction within the particle may come from several origins. In the tests we have performed, coal-, anthracite-, charcoal-, and cokefines were successfully used. Therefore, it is possible to greatly decrease the reductor cost compared to the known processes.

With a doubled volumetric output and the unitary half-reduced burning of coke, the use of high ash content coke reductors is possible. The increased productivity resulting from the decreased residence time through the higher reaction speed will be greater than the productivity decrease due to a high ash content in the reductor and fuel used. The same output in terms of volumetric productivity allows the use of more inferior cokes than now possible, and as a result it would even be possible to makes these cokes from a mixture of cokeable and noncokeable coals.

The gas leaving a furnace embodying the present invention is about 1/3 of that found in current practice, and its CO content is reduced from the present figure of 22 to 24% to approximately 6 to 8% and, in this way, the current CO waste in the furnace is reduced to 10% of the present figure. This gas may be used by blast furnace regenerators themselves (cowpers) to generate low temperature preheated air.

Embodiments of the invention also allow the elimination of one of the high thermal peaks in the classical form of traditional integrated siderurgy, i.e. agglomerate production, in as much as the proposed self-reducing input nodules are cold hardened. The significance of the thermal input for coke production is also decreased due to the reduction in need for coke by 2/3 thus representing a parallel source of energy economy.

As the presently available installations may readily be adapted for the innovations now proposed, thus multiplying the productive capacity of the main parts of siderurgical plants, the described process may be introduced rapidly.

Stock cost is also reduced and because of the subsequent savings a good economical return can be expected.

Claims (9)

Claims

1. Compact nodules for metal production comprising a mixture of oxides, reductors and agglomerants, wherein the mixture comprises 50% to 85% (by weight) metallic oxides; a quantity of reductors, being coal, charcoal, coke or a mixture thereof, which lies in the range of 1 to 2 times that stoichiometrically required for oxide reduction; and 2 to 10% (by weight) cement.

2. Compact nodules according to claim 1, wherein the metallic oxides are selected from pyrite roasting ash residuals, iron ore fines (natural or obtained by grinding), iron oxide fines obtained by dust collection from siderurgical and metallurgical furnaces in general, mill scale and mixtures thereof.

3. Compact nodules according to claim 1 or claim 2, wherein the reductors are selected from:-- several types of coke, charcoal and mineral coal including those having a high ash content, and mixtures thereof.

4. Compact nodules according to any one of claims 1 to 3, wherein the agglomerants are selected from:-- blast furnace portland cement, pozzolanic portland cement, portland cement with coal ashes having pozzolanic properties and mixtures thereof.

5. Compact nodules according to any one of claims 1 to 4, characterised by being superficiaily coated by a thin binder layer such as cement, lime, bentonite, sodium silicate, used separately or in mixtures in proportions which vary from 5 to 50% (by weight) in water suspension and up to 30% (by weight) of iron oxide.

6. A process for making compact nodules which are in accordance to any one of claims 1 to 5, which process is characterised by the nodules being obtained via successive impacts on a pelletizing disc border.

7. A process according to claim 6, characterised by coating the nodules with water solutions contained in immersion tanks or applied in spray through sprayers.

8. A metal production process making use of compact nodules according to any one of claims 1 to 5, which process is characterised by using the nodules in several different kinds of metallurgical furnaces such as blast furnaces, cupolas, electric furnaces and laboratory furnaces.

9. A process according to claim 8, wherein the nodules comprise up to 100% of the furnace charge.

1 0. A process according to claim 8 or claim 9, characterised by the nodules being charged in a blast furnace operated with a substantially neutral or only slightly reducing oxidising atmosphere.