BE677178A - - Google Patents

Description

  

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  "Process for the reduction of ter ores by reaction in a fluid bed"

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The present invention relates to an improved process for producing iron from iron ore. More particularly, it relates to a process for the direct reduction of iron ore in which hydrocarbons are used to reduce this ore.



  Specifically, one of the particular embodiments of the present invention is a process for the direct reduction of iron ore in a fluid bed reactor by direct injection of hydrocarbons into the bed, whereby the hydrocarbons are endothermically cracked and the iron ore is endothermically reduced, the heat required for these two reactions being supplied by an external heater. In this heater, the gases from the cracking reactions are partially oxidized with an oxygen-containing gas to heat the reduced carbon-coated iron which is transferred from the reduction zone to the heating zone and which is recycled back to the reduction zone.

   The oxidation conditions in the transfer duct heater are critical and are controlled in such a way that the reduced iron is not reoxidized while the iron is heated to a higher temperature.



   Specifically, another embodiment

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 Particular of the invention resides in a process for the direct reduction of an iron ore in a fluidized bed reactor, which process comprises the direct injection of hydrocarbons and an oxygen-containing gas into a bed containing oxygen. reduced iron ore, whereby the hydrocarbons are partially oxidized and are cracked and carbon is deposited on the reduced iron.



   Cracking of hydrocarbons and reduction of iron ores are strongly endothermic reactions and heat is required to perform these reactions. The necessary heat is obtained by carrying out the cracking or gasification under conditions such that excess carbon is deposited on the reduced iron, this reduced iron together with the carbon being recycled to an external combustion device in which part of the carbon is removed. The excess burns exothermically with an oxygen-containing gas, which heats the particles of reduced iron, these heated particles being recycled to the reduction and gasification zones and providing the necessary heat.

   The quantity of oxygen-containing gas introduced into the gasification zone is such that the production of CO 2 and H 2 O is kept to a minimum, that carbon is deposited and that a relatively small amount of heat. or caused by cracking and partial oxidation of the hydride. The oxidation conditions in the combustion device are critical and are controlled so that part of the deposited carbon is selectively oxidized.

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 The reduced iron is not subjected to reoxidation while the iron is heated to an elevated temperature and is recycled to the reduction zone.



   By carrying out cracking, partial oxidation and reduction in separate reaction zones, and by producing the heat necessary for these endothermic reactions in a different reaction zone, by burning part of the carbon deposited from the reduced iron, each of the reactions can be carried out in a more efficient and economical manner.
In this way, it is possible to choose for each of the reaction zones, the conditions which make it possible to carry out the desired reactions with maximum yield.



   Numerous attempts have been made to reduce iron ore in fluidized beds using hydrocarbons. Difficulties have been encountered in agglomerating the bed and sintering the particles when operating at elevated temperatures. These difficulties usually result in insufficient fluidization and the impossibility of carrying out the process. Further, in most of these processes the reducing gases were primarily hydrogen or a mixture of hydrogen and carbon monoxide from the reforming of various hydrocarbon fuels.



   Reforming is both tedious and expensive and results in a high cost of reducing gases as well as passage of excessive amounts of gas through the reduction plant.



   Perhaps one of the most important reasons

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 Aunt that hydrocarbons are not used to directly reduce iron ore is the particularly poor thermal characteristics of ordinary hydrocarbons, when used as reducing agents for iron ore, especially iron oxide ore . The reduction reactions which use such hydrocarbons are highly endothermic and their yield becomes appreciable only at relatively high temperatures. To provide the heat necessary for these reactions and to maintain the temperatures at the high values required in the reduction zone by preheating the starting gas and / or ore, abnormally high preheating temperatures are required.

   If this heat is to come from an external source and has to pass through the walls of the reduction zone, the temperature gradients are undesirably high. If one attempts to generate heat within the reduction zone itself by burning fuels, the reactions must be carefully controlled so that the ratio of constituents in the gas phase remains below the equilibrium value, at the temperature used. oxide-reduction reactions of iron oxides in the presence of carbon oxides. With regard to the external combustion device, this limitation is eliminated by the application of the carbon coating and by maintaining a short residence time.



   When the ore is used in a powder form, particularly when the mineral is used

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 liquefied solids technique, very high temperatures exceeding 982 C must be avoided, because it has been found that these high temperatures result in agglomeration of the particles, presumably due to plasticization of the solids, in particular the reduced iron itself.



   When an attempt is made to generate a sufficient amount of heat only by partial combustion of hydrocarbons in contact with the ore and / or reduced iron in the reduction zone, further difficulties arise. First of all, the oxidation of hydrocarbons in order to form simply CO has only a rather insignificant positive calorific effect, so that when it is desired to obtain significant quantities of heat, the consumption of hydrocarbons is excessive. .



  A much larger heat input can also be obtained by burning the entire hydrocarbons to form CO2 and water. However, only a limited amount of CO 2 can be tolerated in the reduction zone in order to avoid reoxidation of the metal. It is extremely difficult to reconcile the requirements of efficient heat generation and efficient reduction when using hydrocarbons both as reducing agents and as inter-agents. holding combustion. It is difficult to use hydrocarbons as a source of reducing gases to reduce FeO to metallic iron and to heat this area by adding air to partially oxidize the hydrocarbons, due to the danger of reoxidation of the iron. reduced which would give iron oxides.

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   An attempt has been made to obtain the heat necessary for the endothermic reactions carried out in a reaction zone by passing heated inert solids into such zone, which are heated externally and are then transferred to the reaction zone where they give up their heat. However, the use of inert solids which are circulated through the reaction zone has given unsatisfactory results because it is difficult to achieve effective separation between the inert solids and the subject materials. to a reaction in the reaction zone. Insufficient separation results in consumption of the reduced iron obtained with inert solids.

   In addition, a loss of thermal energy produced in such a process occurs during the transfer of heat to the ore, due to the need to use particles of inert material. larger and denser than the ore particles, as heat transfer agents, so that a separation between the agent in question and the pulsed ore can be obtained.



   The reducing gases from the reduction zone can be partially oxidized with air to provide the heat necessary for endothermic reduction in the first (and second) stage of the reduction zone, in which the oxides ferric iron are brought pure reduction to a lower oxidation state. For example, when reducing Fe203 to Fe, reducing gases can be partially

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 oxidized with air under carefully controlled conditions, to provide the heat necessary for the reduction carried out in this area.

   The reason for this is that, due to the higher oxidation state of iron in this zone, the danger of reoxidation by CO to H2O contained in reducing gases is much lower than in the zone containing FeO and metallic iron.



   The production of reducing gases by using a separate gas production zone to form hydrogen or a mixture of carbon monoxide and hydrogen increases the cost price of the synthesis gas.



  One of the major expenses in reducing iron ore is the cost of producing reducing gases. The item which incurs the most expense in the process is the fuel that must be used to provide the heat necessary for endothermic reactions such as cracking of hydrocarbons and reduction of iron oxide to metallic iron.



  Any process which efficiently utilizes reducing gases and which reduces the demand for heating by a fuel can significantly improve the processes of direct reduction of iron ore. Efficient use of gases from iron ore reduction being difficult to achieve, because if the process uses air, the outgoing gases have a relatively low value as fuel due to their high content of aote, and because these gases cannot be recycled in the iron ore reduction process, without leading to the very expensive installation of a special device for removing nitrogen,

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 carbon dioxide and water.

   Another problem which arises in the direct reduction of these iron ores is that the reduced metal normally has an extremely pyrophoric nature and oxidizes very quickly on contact with air. According to the present invention, the direct injection of the hydrocarbons and the reduction of the iron ore are accomplished in an iron ore reduction zone and the heat necessary for the endothermic reactions is supplied by an external heater. It has been found that when the process is carried out in a series of dense and fluidized beds of finely divided iron ore, ideal heat transfer characteristics and a mixing speed are obtained to achieve substantially perfect uniformity of temperature. the composition of solids.



  This makes it possible to maintain the critical conditions as regards the production of heat, temperature and pressure and also to maintain, among the gaseous reactants contained in the products of the reaction, the appropriate ratios within the narrow limits required for the setting. implementation of the process. When the process is carried out in fluidized bed reaction zones, the flow of materials can be carefully controlled and the desired conditions can be maintained.



   According to a first embodiment of the present invention, the iron ore is reduced in three stages, i.e. 0. is reduced to Fe3O4, Fe3O4 is reduced to FeO and this-

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 this in turn is reduced to Fe. To each of the three stages there may correspond one or more distinct zones. One of the most critical phases of this process is the reduction of FeO an Fe in the third zone.



  Most of the sintering and agglomeration takes place when operating at elevated temperatures in this zone. In accordance with the invention, to prevent this disadvantage, carbonise FeO introduced into the zone for reducing FeO to Fe by cracking a suitable hydrocarbon at a temperature of about 982 C, above the iron. Thus, the iron ore which is undergoing reduction from FeO to Fe is covered with a layer of carbon which prevents agglomeration, sintering and reoxidation of the reduced iron. Cracking of the starting hydrocarbon forms a gas comprising hydrogen and elemental carbon. Hydrogen reacts with iron oxide to form water, while reducing iron oxide to metallic iron.

   Simultaneously, the water thus formed transforms a certain quantity of carbon into gas to form carbon monoxide which itself reacts with iron oxide to form carbon dioxide and metallic iron. The carbon dioxide thus obtained can react with the carbon to form a new quantity of CO which also reacts with FeO to form Fe.



   The rate of introduction of the hydrocarbon is set such that a reducing atmosphere is obtained towards FeO and that the overall calorific requirements of the entire process can be met while simultaneously achieving a relationship of

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 balance in the reduction zones. This zone is heated by circulating carbon coated iron through a transfer duct burner, which is supplied with fuel and air. When this burner is operated using very short solids contact times, for example less than 2 seconds, it is possible to selectively burn the hydrocarbon fuel instead of carbon or iron. There is essentially no reoxidation of the reduced carbon coated iron in the burner.



  The fuel introduced into the burner mainly comprises the residual gases from the Fe3O4 reduction zone. Complementary naphthu can be added to the residual gases when necessary,
The gases generated during the cracking of the hydrocarbon sent to the PeO - Fe reduction stage form the fluidization gases intended for this zone which they maintain in the form of a retained fluidized bed. These gases mainly comprise hydrogen and CO as well as small amounts of CO2 and water. The gases leaving this zone will move upwards to pass into the Fe3O4 - FeO reduction zone, where they reduce Fe304 to FeO.



     In a second embodiment of the present invention, the iron ore is reduced in two stages, that is to say that F "2O3 is reduced to FeO and FeO to Fe. There may however be more than two stages. @.



   The most critical phase in this second process is the gasification operation carried out in the third zone in the presence of reduced iron particles.

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 carbon coated. Most of the sintering and agglomeration occurs when operating at elevated temperatures in this zone. In accordance with the present invention, these difficulties are overcome by depositing a carbon coating on the reduced iron. When the iron oxide has been reduced to metallic iron in the reduction zones, the carbon which is formed in the gasification zone is deposited uniformly on the reduced iron, on which it forms a protective coating.



   In the gasification zone containing Fe and coal, a gas contained: oxygen partially oxidizes the hydrocarbon which, at the high temperatures prevailing in this zone is thus cracked. The following reactions take place in the gasification zone.
 EMI12.1
 Hydrocarbon + 02 002 + 00 + Il20
 EMI12.2
 
<tb>
<tb> Hydrocarbon <SEP> 0 <SEP> + <SEP> H2
<tb>
 
 EMI12.3
 o + I120 CO + H2 00 + H20 C02 + H2 CO + FeO C02 + Fie H2 ... FeO H20 + Fe 0 02 COg
 EMI12.4
 
<tb>
<tb> 20 <SEP> + <SEP> O2 <SEP> 200
<tb>
 The degree of completion of a particular reaction and the amount of a particular product which is formed depend on the conditions of the reaction as well as the ratio of O 2 to carbon in the oxidizing gas and in the starting hydrocarbon, respectively.



   The rate of introduction of the hydro-

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 carbide and O2 so as to maintain an atmosphere which ensures the reduction of FeO and the deposition of carbon.



  The partial oxidation of the hydrocarbon is carried out so as to form maximum amounts of CO and a minimum amount of CO2 and H2O. The general reaction is strongly endothermic and large amounts of heat must be supplied. The heat input is obtained by circulating a portion of the reduced and carbon-coated iron through an external heater in which a portion of the carbon coating is selectively burned with an oxygen-containing gas, which heats the iron. and charcoal without reoxidizing the reduced iron.



   The gases generated by the partial oxidation and cracking of the hydrocarbon introduced into the gasification zone include reducing gases and fluidization gases serving to maintain the reducing beds in the form of dense fluidized beds. The gases produced include major amounts of CO and H2 and small amounts of CO2 and H20.



   The hot gases exiting the gasification zone flow upward to the reduction zone of FeO to Fe where they provide the heat necessary for the reduction and are partially oxidized while reducing the iron oxide to it. metallic iron in the bed of this area. The gas leaving this zone flows upwards towards the zone of reduction of Fe2O3 to FeO, in which the gases are further oxidized while the iron oxide contained in this bed undergoes a further reduction bringing it into a state

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 lower oxidation. The gas leaving the Fe2O3 reduction zone is still relatively hot and can be used to preheat the ore to be processed, or it can be burnt later as fuel.



   The reduction reactions carried out in the Fe203 to FeO reduction zone are endothermic and the necessary heat is obtained in these zones by preheating the iron ore to be treated which is sent to the Fe203 reduction zone and using ega- There is also the residual heat of the gases leaving the zone for reducing FeO to Fe. In addition, additional heat can be supplied to this zone, that is to say the zone for reducing Fe203 to FeO, by partially oxidizing a portion of the reducing gas by introducing an oxygen-containing gas into this zone, which gas selectively burns the reducing gas while maintaining an atmosphere which is still reducing to the gas. iron oxide.



   Most of the heat necessary to preheat the starting ore to a high temperature can be obtained by contacting this ore, in a preheating cyclone or in some other suitable device, with the gas leaving the device. external heating device. A substantial part of the additional heat supplied to the FeO to Fe reduction zone can be obtained by sending to this zone a part of the reduced iron particles, coated with carbon and heated, which exit from the transfer duct burner. Most of the heat required is

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 supplied to the gasification zone by recycling the major part of these iron particles in this zone from the heater.



   It is essential, in the implementation of the process of the invention, that the ratio between O2 and the hydrocarbon introduced into the gasification zone is adjusted so that the ratio between CO and CO2 and between H2 and H20 in this zone remains lower than that for which the oxidation of the metal becomes predominant, but at the same time this ratio should be adjusted so as to maintain an oxidation potential of a suitable high value so that the excessive carbon deposition by cracking of the hydrocarbon is reduced.

   The amount of carbon deposited on the iron is critical in that, if excessive amounts of carbon are deposited, the reaction becomes more strongly endothermic, requiring the addition of additional heat to this zone, to carry out the reaction. which also represents a significant heat loss and a loss of reducing gases, the amount of fuel required for the reduction being minimally increased. On the other hand, if the amount of carbon deposited is too low, there is not enough carbon to provide the necessary heat and still leave enough to prevent reoxidation of the reduced iron.



   In a variant of the aforementioned first embodiment, not shown on the next day, a part of the solid particles coming from the cyclone of the transfer duct burner can be directed to the Fe3O4 reduction zone to heat this.

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 .zone without significantly modifying the oxygen content of the iron circulated, For this purpose, the quantity of hydrocarbon fuel introduced into the process can be slightly increased in order to maintain the composition of the gases leaving the Fe3O4 reduction zone at the value equilibrium of C02 / CO and H20 / H2 for the FeO - Fe reduction. Additional fuel can be added,

   either in the FeO reduction zone or else in the Fe304 reduction zone. By operating so that a part of the hot solid particles coming from the cyclone of the transfer duct is routed to the Fe3O4 reduction zone before returning to the FeO reduction zone, it is possible to obtain independent control. the temperature of the Fe3O4 reduction zone. In many cases, this can have considerable benefits.



   The gases leaving the cyclone of the transfer line burner are reducing with respect to the balance between Fe2O3 and Fe304 and serve to accomplish this reduction. The gases leaving the Fe2O3 reduction zone are used in a short contact time preheating cyclone to preheat the starting iron ore sent to the first reduction stage *
It is essential that the hydrocarbon introduced into the FeO - Fe reduction zone is controlled in such a way that the CO2 / CO and H2O / H2 ratios in the outgoing gas remain lower than that for which the oxidation of the metal becomes predominant, and at the same time,

   this ratio must be adjusted so that the oxidation potential remains high enough to reduce sen-

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   Easily the excessive deposition, on the reduced iron, of the carbon formed by cracking of the starting hydrocarbon. The amount of carbon deposited on the iron is critical in that if excessive amounts of carbon are deposited, the reaction becomes more strongly endothermic, requiring additional heat to be supplied to this zone to run the reaction. It also represents a significant loss of heat, which increases the amount of fuel required to carry out the reduction reaction.



   A preferred embodiment of this first embodiment of the present invention requires the direct injection of hydrocarbons into a reduction zone in which the hydrocarbons are cracked and form the reducing gases and in which the iron oxide is. reduced to metallic iron. The reduced iron is covered with a protective carbon coating which prevents reoxidation, and which renders the iron non-pyrophoric, and which also prevents agglomeration and sintering in the reducing zone. The gases formed in this zone serve as reducing gases in the other stages and also constitute the fuel which is burned with a gas containing oxygen to heat the iron in the transfer duct of the burner.

   The heat adsorbed by this far and by the carbon provides the heat necessary for the endothermic reduction and for the cracking reaction carried out in the iron reduction zones. By recycling the iron it reduces more carbon, which is the heat transfer agent from the combustion zone to the

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 reduction zone, and by heating them, the difficulties of separating an inert heat transfer vehicle from the reaction materials are overcome. The iron serving as the heat transfer agent is not reoxidized and is the desired product which is simply removed from the reduction zone. The price of synthesis gas is reduced by the combustion of waste gases to heat the recycled iron.



  The amount of air required and recycled in the process is reduced by using the oxygen contained in the iron oxides to provide the necessary oxygen in the reduction zone.



   In a preferred embodiment of the second mentioned embodiment of the present invention, the hydrocarbons are injected into a gasification zone in which they are partially oxidized with air and are cracked, causing deposition. of carbon on iron reduces and forms reducing gases which reduce iron oxide to metallic iron in the reduction zones. The deposition of carbon formed on the reduced iron prevents its reoxidation, renders the iron produced non-pyrophoric and prevents the agglomeration and sintering of the reduced iron in the gasification zone.



  The gases formed in this zone serve as reducing gases in the reduction zones and the deposited carbon is partially burned with air to heat the recycled iron in the external burner. The heating of the carbon-coated iron provides, on recycling, the heat necessary to carry out the endothermic cracking and reduction reactions which take place.

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 in the gasification and iron reduction zones, respectively. By recycling the drill that is the heat transfer agent, from the combustion zone to the gasification zone and the iron reduction zone, and heating this iron, the requirements and the difficulties encountered in separating an inert agent heat transfer of the reaction products are mitigated.

   Since the heat transfer agent is not reoxidized on contact with the atmosphere thanks to the protective carbon coating, this substance can be extracted from the reduction zone and sent to storage without further processing.



   In fig. 1 of the appended drawing schematically shows the reduction zone, the transfer duct burner, the melting zone and the method of carrying out the first embodiment of the invention.



   The hydrocarbon fuels introduced into the FeO - Fe reduction zone, which are cracked to produce the reducing gases and which reduce FeO to Fe, can be hydrocarbons, normally gaseous, such as natural gas, methane, ethane, carbon. propane, butane or normally liquid hydrocarbons such as gasoline, naphtha, kerosene, light and heavy gua-oils from vacuum distillation, heavy oils, diesel oils, hydrocarbons residuals or similar products. The amount of fuel needed to reduce a specific amount of iron ore depends on the fuel used.

   A preferred fuel is a

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 A heavy liquid hydrocarbon with a low content of sulfur and metals. The gases leaving the reduction zones are partially oxidized in the transfer duct burner with an oxygen-containing gas.



  Usually air is used. Iron ores having varying degrees of purity can be reduced in accordance with the present invention. Reduced ores are generally formed mostly from Fe2O3. Before being sent to the iron ore reduction zone, the ore, and pulverized until it has a particle size such that it can be transformed into fluidized bed and .. \ the reactions can be carried out in dense fluidized beds.
The degree of reduction of iron oxides in the bed into which the hydrocarbons are injected is critical and is carefully controlled. This bed contains FeO subjected to reduction to Fe and large amounts of Fe.

   These substances constitute a catalyst for the cracking of hydrocarbons and the production of reducing and fluidifying gases. The reactions in this zone are controlled in such a way that the products contain 2 to 20% carbon based on iron. The average carbon percentage is controlled so that each particle carries at least some carbon The reduced iron with a carbon coating is taken as a product or is recycled to the transfer duct burner at rates such as the desired percentage of carbon to the iron as well as the composition of the catalyst making it possible to obtain

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 hold the desired reduction are maintained.



   In general, pressures are not considered to be important variables in the process, except that they must be sufficient to maintain proper circulation of solids in the system. In general, the process is carried out at pressures between atmospheric pressure and a (relative) pressure of 10.5 kg / cm2. However. pressures higher or lower than these can be used, if desired. It is not intended to limit the process to particular pressures. In addition, the pressures can be modified according to the reactions carried out in a particular zone so that the gas exerts a reducing or oxidizing action on the reactants, as required.



   The temperature conditions and the ratio between 0 2 and CO and between H2O and H2 in each of the reduction zones as well as in the transfer duct of the burner are critical and will be described in detail. These conditions are set so that the entire process is balanced with respect to endothermic and exothermic reactions, and the heat necessary for the endothermic reactions is generated in the transfer duct burner, in which the main fuel is the gas leaving one of the reducing zones. The reduction of an iron ore can be carried out in one, two or three reducing stages, each stage containing one or more beds.

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   By way of illustration of this first embodiment of the present invention, an iron ore is reduced in three stages. During the first stage, the iron ore (Fe203) is reduced to Fe304 at a temperature of 704-8i6 C, although temperatures of 649-982 C can also be used, and at (relative) pressures between 0 and 2.45 kg / cm2, although pressures from 0 to 21 kg / cm2 can also be used.

   Due to the high oxidation state of iron ore, reducing gases containing relatively high amounts of CO2 and H2O can be effectively used to reduce Fe2O3 to Fe3O4. The residual gases from this harness contain CO2 and CO in a ratio of 50 to 300 and preferably 200 to 250 and H2O and H2 in a ratio of 50-250 and preferably 150-200. The higher the degree of reduction of the iron ore, the more critical the concentration of CO2 and H2U in the reducing gases. In the Fe3O4 reduction zone, temperatures of 649 to 871 C can be used, although it is preferred that they are between 704 and 816 C.



  The ratio of CO2 to CO can be 0.2 - 1.5, but it is preferred that it be 0.75 - 1.0. The ratio between H2 and H2O can be 0.2 - 3.0, with a ratio of 0.5-1.0 being preferred. These reports relate to the constituents of the gases leaving this zone. The gases leaving the Fe304 reduction zone have considerable calorific value and are used as the primary fuel sent to the transfer duct burner, where they are partially oxidized with air to

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 providing the heat required to heat the iron particles which are returned to the reduction zone to provide the heat necessary for the endothermic reactions taking place in this zone.



   In the zone of reduction of FeO to Fe, the temperatures are between 704 and 1038 C and preferably between 871 and 982 C. In this zone, the ratio between C02 and CO is adjusted in such a way that it ensures the reduction of FeO to Fe. A ratio of 0.2 - 0.6 is used, with a ratio of 0.2 - 0.4 being preferred. The ratio between H20 and H2 can be equal to 0.2-0.6. Preferably, the ratio between H2O and H2 is maintained at 0.3 - 0.5. The above ratios represent the maximum degree of oxidation of reducing gases that is allowed in this zone and they are also the same for the gases leaving this zone.

   In order not to use excessive amounts of hydrocarbons, the amount of carbon deposited on the reduced iron in this stage is kept at about 0.2-10.0 by weight, based on the weight of iron. Preferably, by tightly controlling the conditions in this stage, an amount of carbon between 3.0 and 6.0% by weight can be deposited on the reduced iron. The amount of carbon deposited on the reduced iron should be hearth just sufficient to prevent agglomeration and sintering, to maintain the iron in a non-pyrophoric condition and to protect the iron from reoxidation in the transfer duct burner.

   Excessive deposition of carbon on iron increases the amount of heat required for cracking to occur and generally results in

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 less efficient reduction and cracking operation. the conditions prevailing in this stage are carefully controlled so that only the minimum quantity of carbon desired is deposited on the reduced iron.



  In addition, the quantity of FeO to be reduced to Fe which is sent to this stage is carefully regulated so that the quantity of oxygen introduced into this zone with FeO is sufficient for a reduction with the cracked products originating from the cracking reaction of the gases. hydrocarbons, in order to produce carbon monoxide and water necessary for the production of reducing gases. By controlling the frame of introduction of FeO in this zone, the temperature and the pressure, the quantity of oxygen supplied with FeO introduced in this zone is sufficient for a reaction with the carbon formed by the cracking of the hydrocarbons, so that only a minimum amount of carbon is deposited on the reduced ore.

   Due to the operation of the fluidized bed reaction, a reduced ore on which is deposited an amount of 3.0 to 6% by weight of carbon, for example, can be quickly removed from this zone and / or be recycled. in the transfer duct burner.



   Essentially, all of the heat required for the reduction and cracking reactions according to the process of the invention is generated in the transfer duct burner. The heat for preheating the air and fuel is supplied ex- later. Part of the heat generated by the burner is adsorbed by Fe coated with carbon.

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 in this burner, and is transferred to the reduction zone in the form of sensible heat given off by the heated and reduced carbon-coated iron which circulates therein.



  Part of the heat is transmitted to the reducing zone via the hot gases exiting the transfer duct of the burner and which are sent to the reduction zone of Fe 2 O 3 to heat the iron oxide in this zone while at the same time. reducing will. The main fuel sent to the burner transfer duct is the gases leaving the Fe-, 0. reduction zone. However, when this is. necessary, additional fuel can be fed into the burner. The concentration of carbon monoxide and hydrogen in the gases from the Fe3O4 reduction zone is relatively high and the heat of combustion of these gases is high.

   These gases are partially oxidized in the transfer duct burner, in which part of 1-carbon monoxide is oxidized to form carbon dioxide and hydrogen is oxidized to form water, giving off considerable amounts. of heat which is adsorbed as sensible heat by the circulating reduced carbon-coated iron. Only enough CO and H2 remain in the gas to reduce Fe2O3 to Fe3O4.



   The gases leaving the transfer pipe burner at very high temperatures are used to supply heat and serve as reducing gases for the Fe2O3 reduction zone. As a result of the very high oxidation state of the ore in

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 In this zone, the relatively high ratio between 002 and CO and between H20 and H2 in the combustion gases leaving the burner has no detrimental effect on this reduction, and the gases however retain sufficient reducing power to reduce Fe203 in Fe3O4.

   The combustion conditions in the transfer duct burner are critical, since it is desired to obtain a combustion of maximum efficiency of the gases leaving the air in order to increase the temperature of the recycled iron, without however oxidizing the carbon coating or reoxidizing the carbon. reduced iron. Reoxidation of the reduced iron does not occur because the carbon coating protects the iron and would preferentially be oxidized before the iron under the conditions in the transfer duct burner.



   In the transfer duct burner, the temperature is maintained at about 760-1204 C, although temperatures of 871-1093 C are preferred during the oxidation of the outgoing gases. This oxidation increases the temperature of the recycled iron from about 55 to
165 C, preferably about 55 - 110 C. The most important factor in preventing reoxidation of the reduced iron in the transfer duct burner is to maintain a very short contact time in that burner.

   The residence time of the reduced iron in the burner is between 0.1 and 2.0 seconds, although periods of 0.1 to 0.5 seconds are preferred, the solid particles and the gases circulating in it. the burner comes into contact and the gases react in a phase condition of gas-solid particles moving

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 violently. The ratio of CO2 to CO in the transfer duct burner is 2.0 - 10.0 and the ratio of H20 to H2 in the transfer duct burner is 1.5 - 25.0. The preferred ratio of CO 2 to CO is 4.0 - 6.0 and the preferred ratio of H2O to H2 is 4.5 - 12.0.



   By carefully controlling the combustion in the transfer duct burner, that is to say the ratios between CO2 and CO and between H2O and H2, as well as the residence time, the outgoing gases are preferentially burned and the iron reduced. is not reoxidized.



  The outgoing gases are returned to the transfer duct burner from the reduction zone with an appropriate CO2 ratio. CO and H2O 11 at a rate of about 561.6 - 811.2 m3 / tonne of iron, preferably at a rate of about 624 - 748.8 m3 / tonne of iron. The air is introduced into the burner at a rate of 1.0 to 1.25 dm3 of air / dm of outgoing gas and preferably at a rate of 1.0 to 1.1 dm3 / dm3 of outgoing gas.



   A reactor with an iron reduction capacity of 90 tonnes / day and comprising three reduction stages may have a diameter of 0.30 m and a total height of 27.5 m. A transfer duct burner intended to provide the heat necessary for carrying out endothermic reactions and which may be useful with such a reaction zone may have a meter of 0.6 to 1.8 m and a height of. 4.5 - 13.7 m. Pumps, valves, heating furnaces, cyclones for separating solid particles from gases, downpipes and risers are used

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 in a manner known in the art.

   The reduction can be made in a 1 or 2 bed system, instead of. operate in a 3-bed system. In addition, the beds can be divided into reduction and preheating sections. The number of beds used to carry out the reduction is outside the scope of the invention.



   The heated solids exiting the transfer duct burner can be returned entirely to the FeO to Fe reduction zone, or can be directed to the Fe293, or Fe3O4 reduction zone. In the latter case, some reoxidation of the circulating solids would occur. Preferably, the heated solid particles are returned entirely to the reduction zone.
FeO. Additionally, additional amounts of hydrocarbon fuel and oxygen can be added to the transfer duct burner to provide the additional amount of heat required for the endothermic reactions.

   However, it is especially preferred to use the gases leaving one of the reduction zones, preferably the Fe304 reduction zone, to save fuel, thus reducing the overall cost of the process. Further, depending on the degree of control desired over the entire process, the iron ore sent to the transfer duct burner may or may not be coated with carbon. However, if it is carbon coated, control of the heater in the transfer duct burner is not necessarily as strict as if it is not.

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 was not coated.



   According to this first embodiment of the invention, a three-stage reduction zone is implemented with an external burner with a transfer duct. In this embodiment, the valves 35, 38 and 39 are closed. In the drawing, there is shown a preheating furnace 1 in which a combustible hydrocarbon, such as light naphtha, which is introduced through a duct 2, is heated to a temperature of about 482 to 53 8 C, but lower than that. at which the naphtha forms coke in the oven. The preheated fuel is then sent to a bed 9 of a reduction vessel 6 via a pipe 2.

   The naphtha is sprayed directly into the fluidized bed containing FeO and Fe, in which the reduced iron acts as a catalyst and cracks the naphtha forming elemental carbon and hydrogen. The cracked products regulate with FeO in the fluidized bed reducing FeO to Fe, while oxidizing carbon to carbon monoxide and carbon dioxide and hydrogen to H2O. Carbon monoxide can further react with H2O to form carbon dioxide and hydrogen, and hydrogen can react with additional FeO to form H2O and Fe.



   The temperature in bed 9 is maintained at about 871 - 982 C. The CO CO2 ratio in this bed is critical and is carefully adjusted and maintained at 0.2 - 0.4 while the H2: H2O ratio in the bed, which is also critical, is maintained at 0.3 - 0.5.



  Additional amounts of FeO are continual-

 <Desc / Clms Page number 30>

 is introduced from bed 11 through a down tube 22 at a rate sufficient to supply the bed with the quantity of oxygen necessary to produce carbon dioxide and H20, the presence of which is required to form the gas. synthesis used in reduction.

   The rate of introduction of FeO is critical, since, if the amount of oxygen introduced into bed 9 in this manner is not sufficient, excessive amounts of carbon are deposited on the reduced ore. Furthermore, the introduction of the fuel must be controlled so as to adjust the balance between heat and materials while maintaining satisfactory combustion of the gases, in order to carry out the described process. The rate of introduction of FeO into bed 9 is controlled using devices well known in the art.

   The rate at which the reduced iron is withdrawn through conduits 23 and / or 25 is such that carbon cannot accumulate in excessive quantities on the reduced ore, and the quantity of reduced iron maintained in bed 9 is controlled by so as to maintain an appropriate ratio of FeO to Fe so that the desired reactions take place.
The cracking and reduction reactions in bed 9 are highly endothermic and a large amount of heat must be supplied to bed 9 to maintain the reaction temperature. Cracked and partially oxidized products such as H2, CO, H2O and CO2 constitute the fluidizing gas used to maintain bed 9 as a dense fluidized bed.

   These gases pass through the bed 9, a space 10 and a fluid grid.

 <Desc / Clms Page number 31>

   di.fication 7 or other suitable device and are introduced into bed 11 where the gases fluidize Fe3O4 contained in this bed, thus maintaining a dense fluidized bed. In this bed, the fluidizing gases reduce Fe3O4 to FeO. Fe3O4 is continuously passed into bed 11 from Fe304 reduction zone 13 through a drop tube 21. The rate of introduction of Fe3O4 into bed 11 is controlled in a manner conventional in the art. In bed 11, CO and H2 contained in the reducing gases are partially oxidized to CO2 and H2O, while reducing Fe304 to FeO.

   Bed 11 is maintained at a temperature of about 704 to 816 C, the ratio between CO and CO2 in this bed is maintained between 0.75 and 1.0 and the ratio between H2 and H2O in this li.t is maintained between 0.5 and 1.0. Only a part of CO and H2 coming from bed 9 and introduced into bed 11 is oxidized to CO 2 and H2O. A considerable amount of CO and H2 remains in this gas. The gas passes into space 12 and leaves it through a conduit 14 to reach ur. cyclone 4, in which the entrained solid particles are separated and returned by a (, wave 42. The gas exiting cyclone 4 is sent to a transfer duct burner 5 with air to heat the sent carbon coated iron. to this burner.



  The transfer duct burner 5 supplies the necessary heat to bed 9 and, in some cases, to bed 13, for the endothermic reduction and cracking reactions carried out in beds 13 and 9.



   In bed 9, the cracked and partial oxidation of the cracked products are carefully controlled.

 <Desc / Clms Page number 32>

   brushed so that the amount of carbon deposited on the reduced iron removed is maintained at about 3.0 to 6.0% by weight, and when this average amount of carbon is deposited on the reduced iron, the latter is removed . Part of the carbon coated iron is taken up through line 23, valve 34 and line 30 and constitutes the product obtained in accordance with the invention. The carbon coating deposited on the iron makes the latter non-pyrophoric and facilitates its handling. The remainder of the carbon coated iron is sent to transfer duct burner 5.

   Combustion air for the burner is introduced through the duct '.' 3 in the preheating furnace 1, in which the air is heated to about 482 to 982 C. The exiting gas in the duct 26 collects the reduced carbon coated iron circulating in the duct 25 and entrains it to through the riser tube 25 to the transfer duct burner 5, where. it comes into contact with the preheated air.



   At the inlet of the transfer duct burner, preheated air from duct 3 is mixed with exhaust gases which contain the reduced carbon coated iron which exits bed 11. In In the transfer duct burner 5, the outgoing gases are partially oxidized by the preheated air and the temperature of the carbon-coated iron particles is thus raised from 55 to 110 C. The burner 5 is operated at a temperature from 871 to 1093 C. The residence time of the carbon coated iron particles in a transfer duct burner ranges from 0.1 to 0.5 seconds.



   The reduced iron heated in the con-

 <Desc / Clms Page number 33>

 transfer unit may or may not be coated with a carbon deposit. However, the conditions for carrying out the heating are less critical if the particles are coated with carbon. In a preferred embodiment, the reduced iron particles are coated with 5-10% by weight carbon. The ratio of CO2 to CO in the transfer duct burner is 4.0 to 6.0 and the ratio of H20 to H2 is 4.5 to 12.0.



  Only a sufficient quantity of air is added to the burner to partially oxidize the outgoing gases so that the reduced iron particles coated with carbon contain the quantity of additional sensible heat necessary for the reactions to take place in bed 9. The The heating which takes place in the burner 5 and the amount of solids circulated must be regulated so as to provide the. heat required to carry out the desired cracking and reduction reactions in bed 9.



   The reducing gases leaving the bed 11 are only partially oxidized in the burner 5 with transfer duct, the gases leaving the top of this burner at the same time as the reduced iron particles being taken up by the duct 32 and introduced into the separator. cy- clone 28. These outgoing gases are at a temperature of
871-1093 C approximately. In cyclone separator 28, the solids are separated and are then returned through line 29 to bed 9 where the hot particles of reduced iron provide the heat necessary for the reactions taking place in that bed. The separated overhead gases exit through a conduit 27 are introduced into

 <Desc / Clms Page number 34>

 a space 36 and pass through a fluidization grid 8.

   The role of the hot gases is to heat, to fluidify and to reduce the iron oxides contained in the bed 13. Since the iron oxides contained in the bed 13 are in a high oxidation state, that is to say in the form of Fe 2 O 3, the outgoing gases which circulate in the line 27 still have sufficient reducing power to reduce the iron by bringing it from this high oxidation state to a lower oxidation state. This is so even though these gases have a relatively high concentration of CO 2 and H 2 O as a result of partial combustion in the transfer duct burner 5. The ratio of CO 2 to CO is between about 4.0 and 6.0 and the ratio of H2O to H2 is between about 4.5 and 12.0.



   The starting iron ore is introduced through line 19 into a reheating cyclone separator
16 or in another suitable contact device in which the starting ore is directly contacted with the hot gases leaving bed 13 and introduced through line 15, and the ore is preheated to a temperature of about 204 to 316 C or higher. The preheated ore is introduced through line 20 into bed 13. The cooled outgoing gases exit from the heating cyclone separator 16 through line 17 and can be used to heat other product streams in the process by heat exchange. indirect.



   In bed 13, Fe203 is reduced to Fe304. The heat necessary to carry out the reduction is supplied mainly by the hot gases introduced through the duct.

 <Desc / Clms Page number 35>

 27. The reduction temperature in bed 13 is about 704-816oC. The ratio between C02 and CO is 200-250 and the ratio between H20 and H2 is approximately 150-200. Iron oxide in the form Fe2O3 which has been reduced to-Fe304 exits bed 13 through the down tube 21 and passes into bed 11, as described above.



  In another embodiment of this first embodiment of the present invention, the reduced ore coated with carbon is sent directly to an iron melting zone 31. In this case, the valve 34 is closed and the valve 35 is open. As for the valves 38 and 39, they can both be partially open, or one can be open while the other is closed. The hot, carbon-coated reduced ore is taken from zone 9 and, instead of being sent to storage through valve 34 and conduit 30, it is sent directly to smelting zone 31 which is maintained. at 1593-16490C by oxidation of the carbon coating of iron reduced to CO and CO2.

   When the carbon undergoes oxidation, it heated the melting zone and melted the spongy iron as liquid metal. The preheated air is introduced into the melting zone through duct 44 to maintain combustion. The outgoing or combustion gases exit through duct 41 and pass through a recovery boiler 37 in which they are brought back to a temperature of 760 to 1093 C. These gases have considerable calorific energy, can be used as fuel and have a reducing capacity.

   The gases at this temperature can be introduced into

 <Desc / Clms Page number 36>

 the burner 5 has a transfer duct, for use as fuels or else to be sent to the Fe203 or Fe3O4 reduction zones for use as preheating and reduction gas.



  In fig. 1, the arrows show that the combustion gases pass through valve 39 and 42 to reach the Fe304 reduction zone and pass through valve 38 and pipe 25 to reach heater 5.



   The function of the recovery boiler is to reduce the temperature of the gases leaving the melting zone from around 1649 C to 760 - 1093 C. The gases can be treated much more easily at lower temperatures. The combustion of the reduced iron carbon coating, which occurs in the smelting zone, and the use of the combustion gases as preheating gases, reducing gases and as fuel, represent a considerable saving in the fuel used. in the process. The liquid iron at about 1649 C is taken through a line 33 and is subjected to further treatment.



  The heat adsorbed in the boiler 37 is used for preheating or is transformed into energy used in the process.



   In fig. 2 of the appended drawing schematically shows the gasification zone, the reduction zones and the transfer duct burner, which correspond to a preferred embodiment of the present invention.



   The hydrocarbon fuel introduced into the

 <Desc / Clms Page number 37>

 gasification zone where it is partially oxidized and cracked to form reducing gases can also consist of a normally gaseous hydrocarbon.



  The amount of fuel required to reduce a specific amount of iron ore depends on the type of fuel that is used and the ore that is subjected to the reduction. Preferably, use is made of a natural gas comprising essentially methane, and normally liquid hydrocarbons such as naphtha.



   Some of the carbon deposited on the reduced ore is oxidized in the external burner by contact with a gas containing nitrogen. In general, air is preferred. Various types of iron can be reduced and, primarily, ores containing Fe2O3 which have been pulverized to a particle size such that they can be fluidized for carrying out dense fluidized bed reactions. The state of reduction of iron in the gasification zone into which the hydrocarbons are injected is important and must be carefully controlled. This bed contains a little FeO being reduced to Fe and large amounts of Fe and carbon. These substances are catalysts for the cracking of hydrocarbons and for the production of reduction and fluidification gases.

   The rate of carbon deposition can be controlled by controlling the ratio of oxygen to carbon in the starting hydrocarbon introduced into the gasification zone. The reaction in this zone is controlled such that 5 to 30% by weight of carbon, based on the reduced iron, is uniformly deposited.

 <Desc / Clms Page number 38>

 on reduced iron. The reduced iron provided with a carbon coating is taken as a product and is recycled to the external burner at such rates that the same average percentage of carbon is maintained on the iron and that the catalyst composition which enables the setting to be maintained is maintained. carrying out the desired reduction and cracking reactions.



   Pressures, as mentioned, are generally not considered to be an important variable with respect to the process, except to the extent necessary to maintain proper circulation of solids in the system. In general, the process is carried out at pressures comprised substantially between atmospheric pressure and 10.5 kg / cm2 (relative pressures). However, significantly higher pressures can be used if desired.



  It is not intended to limit the scope of the present invention to particular pressures. In addition, the pressures can be varied depending on the reaction being carried out in a particular zone, such that the gas is oxidizing or reducing to a particular reactant, as required.



   The temperature conditions and the relationship between CO and CO 2 and between H2 and H2O in the gasification zone as well as in each of the reduction zones and in the external burner are critical and will be described in detail. These conditions are set in such a way that the whole process is balanced with regard to endothermic and exothermic reactions, and the heat required for the reactions.

 <Desc / Clms Page number 39>

 endothermic is generated in the external burner which uses as fuel some of the carbon deposited on the reduced iron. Iron drafting can take place. in one, two or three reduction zones (or stages). The present invention will be described with respect to the use of two reduction zones.



  In the first zone or first stage, the iron ore (Fe2O3) is reduced to FeO at a temperature of 538 to 982 C, although one can also use temperatures of 593 to 871 C, and at pressures of 0 to 7 kg / cm2, although pressures of 0 to 1.4 kg / cm2 may also be suitable. Due to the high oxidation state of iron ore, reducing gases containing relatively large amounts of CO2 and H20 can be used effectively to reduce Fe203 to FeO. In this stage, the reducing gases contain CO and CO2 in a ratio of 2-6 and preferably 3-5, and H2 and H2O in a ratio of 1-4 and preferably 2-3.



   The higher the degree of reduction of the iron ore, the more critical the concentration of CO2 and H2O in the reducing gases becomes. In the FeO to Fe reduction zone, temperatures can range from 538 to 982 C, although temperatures from 593 to 871 C are preferred, and pressures can range from 0 to 7 kg / cm2, pressures of 0 to 1.4 kg / cm2 being preferred. The ratio of CO to CO 2 can be 20-100, although ratios of 40-80 are preferred. The ratio between H2 and H2O can be 20-100, with a ratio of 50-90 being preferred.

   Gas

 <Desc / Clms Page number 40>

 exiting the second FeO e reduction stage: Fe have considerable reducing power and are used to reduce Fe203 to FeO in the first reduction stage.



   In the gasification zone, the temperatures are between 760 and 1093 C and preferably between 816 and 982 C. To avoid an excessive consumption of hydrocarbon fuel, the quantity of carbon deposited on the reduced iron in this stage is maintained at 10-30% by weight, based on reduced iron. Preferably, by tightly controlling the conditions in this stage, a percentage of 20 to 25% by weight, based on the reduced iron, can be deposited on the iron.

   The amount of carbon deposited on the reduced iron in the gasification zone must be sufficient to provide the fuel necessary for burning in the external heater, and that enough n remains to prevent agglomeration and sintering of the reduced ore. in the gasification zone., to maintain the reduced iron constituting the product in a non-pyrophoric state and to protect the iron from reoxidation in the external burner. However, an excessive deposition of carbon on iron represents a loss of reducing gases, an increase in the amount of heat required to perform cracking, and generally a less efficient reduction and cracking operation.



   The reaction conditions in the gasification zone are carefully controlled so that only the minimum excess amount of carbon required is deposited on the reduced iron. The relationship between
O2 contained in combustion gases and carbon con-

 <Desc / Clms Page number 41>

 held in the starting hydrocarbon introduced into this zone is carefully controlled, so that the desired amount of carbon is deposited. This O2 carbon ratio can be 0.02 to 0.4, but is preferably 0.05 - 0.20. By controlling the amount of O2 sent to the gasification zone, there is sufficient oxygen to react with only a portion of the resulting carbon. cracking of the hydrocarbon, so that the desired amount of residual carbon is deposited on the reduced ore.

   Due to carrying out this reaction in a fluidized bed, ore with a carbon coating can be efficiently and continuously withdrawn from this zone and be sent to the external burner or be stored.



   Most of the heat required to carry out the reduction and cracking reactions of this process is generated in the external burner. This heat is transferred to the iron ore reduction zone and / or the gasification zone in the form of sensible heat transmitted to the reduced and heated iron, coated with carbon, from the transfer duct burner. The primary fuel sent to the transfer duct burner is carbon deposited on the reduced ore.

   When carbon has formed CO and CO2 by oxidation, it provides a certain amount of heat, Part of the carbon coating is oxidized in the external burner, which generates a considerable amount of heat which is absorbed in the form of heat. sensitive by reduced iron coated with carbon.



  The gases leaving the external burner are at. tempera-

 <Desc / Clms Page number 42>

 very high tures and are used to preheat the starting iron ore.



   The oxidation conditions in the external burner are critical, as it is desired to achieve maximum efficient combustion of only a portion of the carbon liner with air to raise the temperature of the recycled iron. and do not oxidize the reduced iron. The reoxidation of the reduced iron is kept to a minimum, since only part of the carbon coating burns and the remaining carbon protects the iron and would preferentially be oxidized first under the conditions in the external burner. The critical feature with regard to the operation of the burner is the maintenance of an extremely short residence time of the carbon coated particles in the burner.

   In it, the temperature is maintained at about 927 - 1371 C and, preferably, at 982 - 1204 C.



   The burner operates at a (relative) pressure of 0 to
3.5kg / cm2 and preferably from 0 to 1.4 kg / cm2. This oxidation increases the temperature of the recycled iron by about 38 to 260 C, preferably 93 to 204 C. The residence time of the reduced iron in the transfer duct burner is short, and is usually 0.1. to 5.0 seconds, although periods of 0.4 to 1.0 seconds are preferred. The solids and gases in the burner react in a dispersed solid phase.



   The amount of excess air in the burner is set to 0 - 20%. The preferred amount of excess air is 0-10%. The amount of excess air is calculated from the amount of carbon burned.

 <Desc / Clms Page number 43>

 The amount of total carbon present is much higher but the contact time is too short to allow complete combustion of the carbon.



   The amount of carbon burnt in the transfer duct burner is 0.06 to 0.20 ton / ton of reduced ore, preferably 0.08 to 0.15 ton / ton of reduced ore. This represents 2 to 8%, by weight, preferably 4 to 6% by weight, of the deposited carbon which is burnt to form CO and CO2. An amount of heated iron particles of about 16 to 22 tons, per ton of reduced ore, is recycled to the reactor from the heater.



   For an installation producing 90 tonnes of reduced ore per day, which uses a three-stage reactor having a diameter of 2.4 m and a height of 9 m and containing two reaction zones and a gasification zone 9, beds 2.4m high fluids can be used. The external burner required for the endothermic reactions will in this case be 0.60 m in diameter and 9 m in height. Pumps, furnaces, heaters, cyclones for separating solids from gases, down pipes providing connection and risers, can be used in a manner common in the art.



  The number of beds used in carrying out the reduction reaction is outside the scope of the invention. The heated solids from the external burner can be returned entirely to the gasification zone or a part of these materials can be sent to the Fe / PeO zone. An amount

 <Desc / Clms Page number 44>

      Additional fuel hydrocarbon or flue gas from a reduction zone can be introduced into the transfer duct burner to provide additional heat to the circulating iron. However, it is preferred to burn only the deposited carbon.



   In accordance with a preferred embodiment of this second embodiment of the invention, two reduction stages are used in conjunction with an external transfer duct burner. A combustible hydrocarbon such as naphtha is introduced into a preheating furnace where it is preheated to a temperature of about 482 to 538 ° C, and in any case lower than that at which the naphtha crackles. The preheated fuel is then sent through a pipe 104 (fig. 2) to a gasification zone.
109 from a reduction vessel 106 with the aid of a suitable liquid distribution device, together with preheated air 538 C which is introduced through a duct 103 falls.

   The naphtha is sprayed directly into a fluidized bed containing carbon coated iron.



   The reduced er acts as a catalyst and cracks the naphtha into elemental carbon and oxygen, while the O2 in the air partially oxidizes the hydrocarbons or hydrogen to form CO and H2O. Carbon monoxide can also react with H2O to form carbon dioxide or hydrogen and it can further react with residual FeO to form carbon dioxide or hydrogen and it can also react with
Residual FeO to form carbon dioxide and Fe.



   The temperature in zone 109 is maintained at approximately
816-982 C and the pressure at about

 <Desc / Clms Page number 45>

   0 - 1.4 kg / cm2. The rate of introduction of the air is sufficient to supply the bed with the quantity of oxygen necessary to form carbon monoxide intended for the production of the synthesis gas. The air intake rate is critical because, if. not enough oxygen is introduced into zone 109, the quantity of heat supplied by the external burner will not be high enough to maintain the cracking reaction and if too much oxygen is introduced, it does not deposit carbon.



   The rate of introduction of Fe into zone 4,109 is controlled by an appropriate valve mounted in down tube 122 and which is not shown. The extraction of the reduced iron in zone 109 is regulated through line 124 such that the amount of residual FeO contained in the reduced product has a satisfactory low value, usually less than 10%. and the amount of reduced iron in zone 109 is controlled so as to maintain a good carbon coating to protect the reduced iron from reoxidation in the outer burner.

   The cracking and reactions carried out in zone 109 are highly endothermic and a large amount of heat must be supplied to this zone to maintain the reaction temperature at 816-982 0. The cracked product partially oxidized, air CO and H2 and small amounts of heat. quantities of H20 and CO2 constitute the fluidizing gas used to maintain a dense and fluidized bed in zone 109,
The fluidizing gases flow upwards in the bed, and pass through the space 110 and the grid

 <Desc / Clms Page number 46>

 fluidization 107 or another suitable gas distributor, then they pass into bed 111 in which the gases fluidize Fe contained in this bed,

   maintaining it in the form of a dense fluidized bed. In this bed, the fluidizing gases reduce FeO to Fe. The down tube 121 allows the continuous introduction of FeO from the bed of Fe2O3, 113. The rate of introduction of FeO into the bed 111 is controlled by an appropriate valve. , not shown. In bed 111, the carbon monoxide, and H2 contained in the reducing gases are partially oxidized to CO2 and H2O, while FeO is reduced to Fe.

   Bed 111 is maintained at a temperature of 593 to 871 and at a (relative) pressure of 0 to 1.4 kg / cm2 and, in this bed, the ratio between 00 and CO2 is between 3 and 5 and the ratio between H2 and H20 is between 2 and 3. Only a small part of 00 and H2 coming from zone 109 and introduced into bed 111 is subjected to the oxidation to CO2 and H2O. There is a considerable amount of residual 00 and H2 in the gas which breaks in the space 112 for the gases and which passes through the fluidization grid 151 to pass into the bed 113 in which it reduces Fe2O3 to FeO.



     @ Transfer duct burner 105 is a preferred heat delivery device for zone 109 and bed 111 for endothermic reduction in bed 111 and endothermic cracking reactions in bed 109. In the latter , the cracking and the partial oxidation of the cracked products are carefully controlled so that the amount of carbon deposited on the reduced iron which comes out through the

 <Desc / Clms Page number 47>

 duct 124 is maintained at a value of about 20 to
25% by weight based on the iron and, when this average amount of carbon has been deposited on the iron, the latter is then recovered. Some of the carbon coated iron exits through conduit 124 and is the desired product in the process.

   The carbon coating formed on iron renders it non-pyrophoric when exposed to the atmosphere and allows it to be handled more easily. The remainder of the carbon coated iron is returned through conduits 124, 125 and 143 to transfer conduit burner 105. The combustion air for the burner is preheated to a temperature of about 482 to 53800. The air collects the reduced carbon coated iron in duct 125 and carries it through riser 143 to burner 105. to transfer duct. In this burner, the carbon is oxidized by the preheated air to form CO and CO2 'which increases the temperature of the carbon coated particles to approximately 110 to 220 C.

   The transfer duct burner operates at a temperature of about 982 1204 C and a (relative) pressure of about 0 to 1.4 k / cm. The residence time of the carbon coated iron particles in the burner is about 0.4 to 1.0 seconds.



   In a preferred embodiment of this second embodiment, the reduced iron particles are coated with 10 to 30% by weight of carbon, at the iron base. The quantity of carbon revolving the particles is critical because, if this quantity is excessive, this corresponds to a loss in terms of fuel efficiency and in terms of fuel efficiency.

 <Desc / Clms Page number 48>

 quantity of reducing gas formed. On the other hand, if the carbon coating is too small, it is not sufficient to supply the fuel intended for the burner and to protect the iron from reoxidation in the burner. The amount of excess oxygen in the burner is approximately 0-10%.

   Sufficient excess air is added to said burner so that the reduced iron particles coated with carbon receive a sufficient amount of sensible heat to provide the necessary heat for zone 109 and bed 111. The reduced iron particles thus coated with carbon are circulated at a rate sufficient to transmit this heat to zone 109 and bed 111. The degree of heating in the burner 105 and the amount of recycle can be adjusted so as to provide the heat necessary for the heating. performing the desired cracking and reduction reactions in zone 109 and bed 111.

   The gases exiting the head of the transfer duct burner 105 and being at a temperature of 982 to 1204 C are collected together with the heated reduced iron particles and exit through a duct 132 and then pass into a cyclone separator.
128. These gases are at a very high temperature. In the cyclone separator 128, the solids are separated and they are then returned through the conduits
129, 145 and 146 in zones 109 and 111 in which the hot iron particles provide the heat necessary for the endothermic reactions. The separated overhead gases exit through line 127 and serve to preheat the starting ore.

 <Desc / Clms Page number 49>

 



   The starting ore is introduced at a temperature of about 25 ° C. into a preheating cyclone separator 116 in which the ore is directly contacted with the hot outgoing gases coming from the transfer duct burner 105 and introduced through the duct 127, and the ore is preheated to a temperature of 538 to 871 C. The preheated ore is introduced through line 120 into bed 113. The partially cooled gases leaving the preheating cyclone separator 116 through line 117 can be used by means of indirect heat exchange to heat other product streams in the process.

   In bed 113, Fe203 is reduced to FeO. The heat necessary to carry out the reduction comes mainly from the sensible heat of the reducing gases leaving the bed 111 and, in a complementary way, from an injection of air through the duct 154 which determines an increase in temperature thanks to the combustion of part of the reducing gases. In bed 113, the temperature is about 593 to 871 C and the pressure (relative) is about 0 to 1.4 kg / cm2. The ratio between 00 and CO2 is 0.3-1.6 and the ratio between H2 and H2O is 0.2 - 2.5. From bed 113, reduced FeO passes into bed 111 via down tube 121, as already explained.



   The outgoing gases from space 153 passing through conduit 152 have a considerable amount of waste heat and can be used for heat exchange to heat product streams in the process. These gases

 <Desc / Clms Page number 50>

 will normally also be used as fuel.



  They could also be cooled and condensed to remove H2O, then treated to remove CO2 and recycled to bed 109 or bed 111 to provide additional reducing gases.



   The above discussion relates only to two preferred embodiments of two embodiments of the present invention. In the drawing, the pumps, valves, cyclone separators and various apparatuses of the heat exchange plant have been omitted to simplify the representation, but these apparatus are used in a manner known in the art.



   The reduced iron which constitutes the product and is coated with 2 to 10% carbon, iron obtained in accordance with the first embodiment of the present invention, can be easily handled and stored because, under this condition, it does not. is not pyrophoric. This product constitutes perfect synthetic waste and can be used as waste in conventional steel mill processes. Liquid iron can be used directly in a steel making process.



   The recycling of carbon coated iron in accordance with the second embodiment of the present invention allows internal removal of sulfur which may be present as FeS and which may be due to the use of a hydrocarbon fuel containing carbon. sulfur for gasification. During the gasification of the hydrocarbon, sulfur is released and is adsorbed by the reduced iron forming, in the

 <Desc / Clms Page number 51>

 gasification zone, FeS which is recycled to the external transfer duct burner. In the latter, the sulfur contained in the iron is released in the form of H2S. Fe is returned to the reactor. H2S is taken from the system with the combustion products formed in the transfer duct burner.

   Reduced and sulfur-free iron can be obtained by taking the product from the final reduction zone 111 through line 114. In cases where sulfur is not a problem of critical importance, the reduced sulfur-free and coated iron. of carbon can be obtained by taking the product from the gasification zone 109 through the conduit 124.



   The present invention will be better understood on reading the following nonlimiting examples.
 EMI51.1
 : .E ± .P1JLl It is preheated to about bzz0 "in naphtha 14our boiling between 38 and 204 C, and it is introduced into a reduction zone containing FeO and metallic iron.



  The light naphtha is introduced into the reduction zone at a rate of about 0.225 kg / tonne of reduced far ore obtained. The reduction zone in question operates at a temperature of 982 C. Under these conditions, the starting naphtha is cracked into hydrogen and elemental carbon. Elemental carbon joins together with the v-gene in FeO to form carbon monoxide and carbon dioxide, and the hydrogen reacts with the oxygen in carbon dioxide or FeO to form H2O. The latter can still react with CO to

 <Desc / Clms Page number 52>

 form CO2 and hydrogen. These reactions are simultaneous and the amount of each of the products present depends on the reaction conditions.

   The ratio of CO 2 to CO in the reaction zone is about 0.211 and the ratio of H 2 O to H2 is 0.346. The conditions of the reaction are such that 5.5% carbon is deposited on the reduced ore. The gases leaving the FeO / Fe reduction zone at a temperature of about 982 C. The hot gases leaving the FeO reduction zone and hot Fe3O4 leaving the Fe2O3 reduction zone provide the heat necessary for the reduction of Fe3O4 to FeO.

   700 m3 of combustion gas are taken, per tonne of ore, in the Fe3O4 reduction zone, at a temperature of approximately 7600C and this gas is sent to the external burner with transfer duct in which it is partially oxidized thanks to to the addition of air in the burner at the rate of 764.5m3 of air / tonne of reduced ore.



   In the transfer duct burner the temperature of the reduced carbon-coated iron is increased by 68 C over the temperature of the iron in zone 9. The residence time of the iron ore in the transfer duct burner is d. 'about 0.2 seconds. The combustion gases leaving the burner are introduced into the Fe2O3 reduction zone where they heat this bed and serve as reducing gases to reduce Fe203 to Fe3O4. These gases are at a temperature between about 1038 and 1093 C and provide the heat necessary to carry out the endothermic reaction in the reduction zone. The heated iron is

 <Desc / Clms Page number 53>

 sent to the FeO - Fe reduction zone at a rate of 59,500 kg of Fe / tonne of reduced iron obtained.

   About 1310.5 m3 of gas, per tonne of ore reduced, exit the cyclone separator and are introduced into the Fe2O3 reduction zone. The gases exiting at the head of the Fe2O3 reduction zone, at a temperature of about 649 to 760 0, are used to preheat the ore sent to the Fe2O3 reduction zone lice to raise its temperature from about 25 C to about 204 - 316 C.



   The indications in the table below show the savings in fuel and air that can be achieved when directly injecting hydrocarbons using the general means of the transfer duct burner, in comparison with the direct injection of hydrocarbons and air in the reduction zone to obtain the heat necessary for carrying out the exothermic reactions.



    T A B L S A U
 EMI53.1
 
<tb>
<tb> Case <SEP> Direct <SEP> injection <SEP> Injection
<tb>
 
 EMI53.2
 of hydrocarbons and direct and
 EMI53.3
 
<tb>
<tb> air <SEP> in <SEP> the <SEP> burner <SEP> to <SEP>
<tb> <SEP> zones of <SEP> reduction <SEP> leads <SEP> of
<tb> without <SEP> burner <SEP> to <SEP> con- <SEP> transfer
<tb> duit <SEP> from <SEP> transfer
<tb> Air <SEP> required, <SEP> m3 / tonne
<tb> of <SEP> iron <SEP> 1319.8 <SEP> 731
<tb> Fuel <SEP> sent
<tb> in <SEP> the <SEP> zones <SEP> of <SEP> reduction, <SEP> large <SEP> calories / ton <SEP> of <SEP> iron <SEP> 3400 <SEP> 2300
<tb>
 
One can easily see, by examining the table above,

   that the air requirements when using the general means of a gas burner

 <Desc / Clms Page number 54>

 transfer fluid are reduced by about half and the requirements on the hydrocarbon required for carrying out the reaction are reduced by about
1/3, which represents considerable savings in expenses for fuel and air introduced into the process and which also represents a reduction in the dimensions of the installation, since smaller volumes of material are put into circulation. This process greatly reduces the cost of syngas and the amount of fuel required, making the process more efficient, economical and practical.



    Example II
A light C5-C6 naphtha boiling between 49 and 82 C is preheated to about 527 C and is introduced into a gasification zone containing metallic iron and carbon. The light naphtha is introduced into the gasification zone at a rate of approximately
600 kg / tonne of reduced iron ore constituting the; produced, along with 750-875 dm3 of air per kg of naphtha. The gasification zone operates at a temperature of about 871 C and a (relative) pressure of about 0.7 kg / cm2; Under these conditions, the starting naphtha undergoes partial oxidation giving CO, CO2, and H20 and undergoes cracking forming hydrogen and elemental carbon.

   Elemental carbon reacts with oxygen in air to form carbon monoxide, and hydrogen reacts with oxygen in carbon dioxide or with that in air to form H2O. Again, H20 can react with CO to form CO2 and

 <Desc / Clms Page number 55>

 hydrogen. These reactions are simultaneous and the amount of each of the products depends on the reaction conditions. The ratio of O2 to C in the starting light naphtha is about 0.1. The gasification reaction is carried out so that approximately 24% by weight of carbon is deposited on the reduced ore.

   In the gasification zone, 455,650 koal per tonne of reduced ore is required, and in the reduction zone from FeO to Fe; it takes 272,280 kcal / tonne to carry out the reduction reaction in this zone The combustion gases from the gasification zone exit at a temperature of about 871 C and are introduced into the reduction zone from FeO to Fe. The temperature in this latter reduction zone is about 871 C and the pressure (relative) is 0.42 kg / cm2.

   The hot gases leaving the gasification zone, as well as FeO cnaud leaving the reduction zone of Fe3O4 to FeO and the solids leaving the burner provide the calories necessary to reduce FeO to Fe.

   The flue gases leaving the FeO reduction zone are at a temperature of 87100 and are sent to the Fe2O3 reduction zone where they are oxidized by Fe2O3 while reducing Fe2O3 to Fe304 and FeO. An amount of additional heat in this zone by injecting air which oxidizes part of the reducing gases, In the transfer duct burner,

     145 50 kg of carbon deposited on the reduced iron coated with carbon are burnt by 1685 m3 4'air preheated per tonne of reduced ore constituting the product and a quantity of approximately

 <Desc / Clms Page number 56>

 19 tonnes of iron particles per tonne of reduced ore is recycled. In the transfer duct burner, the temperature of the reduced carbon coated iron is increased by about 168 C. The residence time of the iron ore in this burner is about 0.5 seconds. The flue gases leaving the transfer duct burner contain CO2 and nitrogen at a very high temperature and are used to preheat the feedstock.

   These gases are at a temperature of about 1093 C and preheat the starting minor to about 5380C The hot gases containing the hot reduced ore entrained out of the transfer duct hole are introduced into a cyclone separator in which the gases are separated from iron ore. The hot solids are recycled to the ferrous iron oxide reduction zone and the gasification zone at a recycling rate of approximately 19 tonnes per tonne of reduced ore obtained.



   The process described above makes it possible to solve many difficulties of the processes known in the prior art for the reduction of iron ores by direct injection of hydrocarbons by the fluidized bed technique. However, the general means of the transfer duct burner can be used in other direct reduction processes for iron ores, whether the reducing gases are formed by direct injection of hydrocarbons or whether they are formed in a zone. separate gasification.



   The main features of the present invention reside in the extraction of reduced iron or iron

 <Desc / Clms Page number 57>

 reduced carbon coated in the zones of reduction of ferrous iron oxide or gasification, respectively, in the heating of this iron in an external heating zone, in the recycling of the heated reduced iron in the zone of reduction of FeO in Fe and / or in the gasification zone to obtain the necessary heat for the endothermic cracking and reduction reactions. This technique solves the problems of supplying large quantities of heat in the reduction and gasification zones and overcomes the difficulties presented by the operation consisting in separating from the product obtained the particles of the inert substance serving as an agent of heat transmission.

 

Claims (1)

CLAIMS 1.- Process for the direct reduction of iron oxides to metallic iron in contact with these oxides with reducing gases, where the reduction reaction is substantially endothermic and requires the input of large quantities of heat, characterized in that ' it consists of taking some of the reduced iron, sending it to an external heating zone, 4 heating the reduced iron to a high temperature, and recycling this iron to the reduction zone, which supplies the zone reduction of the iron sufficient additional heat to effect the desired reduction reaction. 2.- @@ method according to claim 1, characterized in that the amount of reduced iron sent to the external heating zone and recycled to the. reduction zone is such that the additional heat input is sufficient for the reduction * of iron oxides to metallic iron. 3. A method according to claim 1, characterized in that a hydrocarbon fuel is injected directly into the reduction zone in which it undergoes cracking, and the broken products react with the iron oxide to form reducing gases. which reduce the ox / de iron to metallic iron. 4. A process according to claim 1, characterized in that a hydrocarbon fuel is injected directly into a gasification zone in which it is cracked and the cracked products react to. "To form reducing gases which reduce To form reducing gases which reduce iron oxide to metallic iron. <Desc / Clms Page number 59> 5, - A method of direct reduction of iron ores according to one or other of claims 1 to 4 wherein the iron oxides are reduced to metallic iron, characterized in that it consists in subjecting to endothermic cracking a hydrocarbon fuel and subject to endothermic reduction of iron oxides to form metallic iron, in a reduction zone? in the absence of free oxygen, under reducing conditions such that carbon and hydrogen are formed during cracking and carbon is deposited uniformly on the particles of reduced metallic iron, a part of the carbon coated particles being taken and sent to an external heating zone in which these particles are contacted with a gas containing oxygen and a combustion gas from a reduction zone, which determines the oxidation of a part of the residual gases, the iron particles coated with carbon and thus being heated being recycled in the reduction zone to provide the necessary heat in the form of sensible heat of the heated particles for carrying out the reactions endothermic in this zone, 6.- A method of direct reduction of iron ores according to one or the other of claims 1 to 4 in which the iron oxides are reduced to metallic far, characterized in that a hydrocarbon fuel is subjected to endothermic cracking and partial oxidation in a gasification zone and the iron oxides are subjected to endothermic reduction <Desc / Clms Page number 60> to form metallic iron in a reduction zone in which reducing conditions prevail, carbon and hydrogen being formed during the cracking reaction and the carbon being uniformly deposited on the particles of reduced metallic iron, a sample is taken. part of the carbon-coated particles and sent to an external heating zone in which these particles are contacted with an oxygen-containing gas and in which part of the carbon is subjected to exothermic oxidation, which heats the particles. carbon coated iron particles, and these particles are recycled to the gasification and reduction zone to provide the necessary heat in the form of sensible heat of the heated particles for carrying out the endothermic reactions in these zones. 7. A direct reduction process according to claim 1, for reducing iron oxides to metallic iron, characterized in that it consists: (1) in gasifying a hydrocarbon fuel in a reaction zone, at an elevated temperature, with the oxygen contained in the iron oxides, in order to form hydrogen and carbon, as well as oxidation products of hydrogen and carbon, this reaction being carried out in a dense fluidized bed of oxides iron and reduced iron particles, the carbon formed in the gasification reaction being deposited uniformly on the reduced iron; (2) contacting, in said reaction zone, the gases originating from the gasification reaction and comprising large quantities of 00. and H2, <Desc / Clms Page number 61> with said iron oxides, and subjecting these oxides 4 to an endothermic reduction yielding metallic iron while partially oxidizing the reducing gases; (3) to provide the heat necessary for the endothermic gasification and reduction reactions by taking from the aforementioned reaction zone a part of the reduced iron particles coated with carbon and sending these particles to an external burner, this which causes them to come into contact with a gas containing oxygen and with combustion gases from a zone of reduction of ferrous iron oxide, gases which contain H2 and CO, part of these gases burning to form H2O and CO2 by generating a large quantity of heat which is adsorbed in the form of sensible heat by the reduced iron particles coated with carbon, the temperature of which is thus raised above the temperature prevailing in the reaction zone; (4) recycling the particles of reduced iron thus heated and leaving the burner in a reaction zone, in order to supply the heat necessary for the endothermic reactions which are carried out there. 8.- Direct reduction process according to claim 1, for reducing iron oxides to metallic iron, characterized in that it consists: (1) in gasifying a hydrocarbon fuel in a gasification zone, at an elevated temperature, with a gas containing oxygen, to form hydrogen and carbon as well as oxidation products of hydrogen and carbon, this gasification being carried out in a dense fluidized bed of iron particles <Desc / Clms Page number 62> reduced on which the carbon formed during gasification is deposited uniformly, '(2) to send the gases formed in this gasification zone and comprising large quantities of CO and H2 in a zone for reducing ferrous oxides in which a fluidized bed of ferrous oxides is contacted with the reducing gases and is reduced to iron metallic by an endothermic reaction, while the reducing gases are partially oxidized; (3) to provide the heat necessary for the endothermic gasification and reduction reactions by taking a portion of the reduced iron particles coated with carbon in the gasification zone and sending them to an external burner in which they are contacted with a gas containing oxygen and in which part of the carbon coating burns forming CO and CO2 and generating a large amount of heat which is adsorbed in the form of sensible heat by said particles, which increases their temperature by carrying it above the temperature of the gasification and reduction zones, (4) in recycling the thus heated reduced iron particles leaving the burner to return them to the ferrous oxide reduction zone and to the gasification zone in order to provide the heat necessary for the endothermic reactions carried out in these zones. 90- A method according to claim 7, characterized in that the combustion gases formed in the transfer duct burner are contacted with ferric oxides in a reduction zone of these oxides to reduce them to ferrous oxides. <Desc / Clms Page number 63> 10. - Method according to claim 8, characterized in that the combustion gases generated in the aforementioned burner are contacted with the starting iron ore in a preheating cyclone and the ore is preheated before its reduction. 11. A method according to claim 8, characterized in that the preheated iron ore is sent to a zone for reducing ferric oxides and / is then sent to a zone for reducing ferrous oxides where it is reduced to metallic iron, then it is then sent to a gasification zone where it serves as a gasification catalyst. 12. A direct reduction process according to claim 1 for reducing iron oxides to metallic iron, characterized in that (1) a hydrocarbon fuel is gasified in a reaction zone, at a high temperature, with the oxygen contained in iron oxides, maintaining the temperature between 704 and 1038 C to produce hydrogen and carbon as well as oxidation products of hydrogen and carbon, this reaction being carried out in a dense fluidized bed iron oxides and particles of reduced iron, the carbon formed in this reaction being deposited uniformly on the reduced iron, (2) the gases from the gasification reaction, include large amounts of CO and H2 and are of reducing nature vis-à-vis iron oxides, and these oxides are brought into contact with CO and H2 in this zone, then they are reduced to metallic iron, thanks to a reaction <Desc / Clms Page number 64> endothermic while partially oxidizing the reducing gases, the latter being sent to a fluidized bed of ferric oxides in which they reduce said oxides to ferrous oxides, the iron contained in each of the fluidized beds passing from the oxide reduction zone ferric to the iron oxide reduction zone and to the aforementioned reaction zone; (3) the heat necessary for the aforementioned gasification and endothermic reduction reactions is obtained by taking a part of the reduced iron particles coated with carbon in the reaction zone and sending these particles to an external burner in which they are brought into contact with a gas containing oxygen and a combustion gas coming from a zone for reducing ferrous oxides, these combustion gases containing H2 and CO, in which part of H2 and CO burns so exothermic by forming H2O and CO2 and by generating a large quantity of heat, the residence time of these particles in said burner being between 0.1 and 2.0 seconds, the heat being adsorbed in the form of sensible heat by the reduced iron particles coated with carbon, which brings their temperature adju above the temperature of the reaction zone, (4) the reduced iron particles thus heated, which leave the burner, are recycled in a zone of reduction of the ferrous oxides to provide the necessary heat for the carrying out endothermic reactions in said zone. <Desc / Clms Page number 65> 13. - A direct reduction method according to claim 1, for reducing iron oxides to metallic iron, characterized in that; (1) a hydrocarbon fuel is gasified in a high temperature gasification zone with a gas containing oxygen, the ratio between the oxygen contained in the gas and the carbon contained in the hydrocarbon is between 0.02 and 0.4, so as to produce hydrogen and carbon and the oxidation products of hydrogen and carbon, said gasification reaction being carried out in a dense fluidized bed of reduced iron particles, said carbon produced by said gasification reaction being uniformly deposited on said reduced iron, (2) gases from this gasification zone include large amounts of CO and H2 and are reducing in nature with respect to iron oxides and they are sent from said gasification zone to a ferrous oxide reduction zone in which they come into contact with a fluidized bed of ferrous oxides which are reduced to metallic iron endothermically while the reducing gases are partially oxidized and are then sent to a fluidized bed of ferric oxides in which they reduce these oxides to ferrous oxides, the iron in each of said fluidized beds flowing from the ferric oxide zone to the ferrous oxide zone and to the gasification zone, (3) the heat required for these endothermic gasification and reduction reactions being supplied by sending carbon-coated iron particles taken from the gasification zone. <Desc / Clms Page number 66> tion, in an external burner in which they are brought into contact with a preheated oxygen-containing gas, part of the carbon coating burning exothermically, forming CO and CO2 and generating a large amount of heat and time particle residence time in the burner being 0.1 to 5.0 seconds, the aforementioned heat being adsorbed in the form of sensible heat by the reduced iron particles coated with carbon, which raises their temperature above the temperature of the particles. reduction and gasification zones, (4) and the reduced iron particles thus heated are recycled from the transfer line burner to the ferrous oxide reduction zone and to the gasification zone to provide the heat necessary for carrying out the endothermic reactions in these zones. 14. A method according to claim 12 characterized in that the amount of carbon deposited on the iron in said reaction zone is between 2 and 10% by weight relative to the iron. 15.- The method of claim 13, characterized in that the amount of carbon deposited on the reduced ore is increased by about 2 to 8% in the gasification zone. 16. A method according to claim 12, characterized in that the temperature of the particles which are sent to the transfer duct burner is increased from about 56 to 168 ° C. by virtue of the combustion of CO and H2. as C02 and H2O in this burner. <Desc / Clms Page number 67> 17.- The method of claim 13, characterized in that the temperature of the particles sent into the burner is increased from 56 to 168 C by the combustion of 2 to 8% per pass of carbon from these particles, in said burner. 18. A method according to claim 13, characterized in that the quantity of air sent into the burner exceeds by 20% that which is required for the combustion of the quantity of carbon actually burning in the burner. 19. A direct reduction process according to claim 1, for reducing iron oxides to metallic iron, characterized in that it consists: (1) in gasifying a hydrocarbon fuel in a reaction zone at an elevated temperature , with the oxygen contained in iron oxides, to form hydrogen and carbon, as well as oxidation products of hydrogen and carbon, these reactions of gasification and reduction being carried out in a dense fluidized bed of iron oxides and reduced iron particles, to deposit 2 to 10% by weight of said carbon, relative to the weight of iron produced by said gasification reaction, in a uniform manner on said reduced iron, (2) the gases from said gasification zone include large amounts of CO and H2 and are reducing in nature with respect to the oxide? of iron, in bringing these oxides into contact with said gases in said zone, the ratio of CO2 / CO and of H20 / H2 in said zone being respectively 0.2-0.4 and 0.3- 0.5 and endothermically reducing said oxides to iron <Desc / Clms Page number 68> metallic while partially oxidizing the reducing gases, the latter being sent to a fluidized bed, of ferric oxides in which they reduce said oxides to ferrous oxides, the iron contained in each of the fluidized beds passing from the reduction zone of ferric oxides. ferric oxides to the ferrous oxide reduction zone and to the aforementioned reaction zone; (3) The heat necessary for the aforementioned gasification and endothermic reduction reactions is obtained by removing a part of the reduced iron particles coated with carbon in the reaction zone and sending these particles to an external burner pipe. transfer, in which they are brought into contact with a gas containing oxygen and a combustion gas from a zone of reduction of ferrous oxides, these combustion gases containing H2 and CO, in which a part of H2 and CO burns exothermically forming H2O and CO2 and generating a large amount of heat, the ratio of COg / CO and H2O / H2 in said burner being respectively 4.0-6.0 and from 4.5- 12.0, the residence time of these particles in said burner being between 0.1 and 0.50 seconds, the heat being adsorbed in the form of sensible heat by the reduced iron particles overloaded with carbon, bringing their temperature from about 38 to about 93 C above the temperature of said reaction and reduction zones of ferrous oxide, (4) recycling the thus heated reduced iron particles, which exit the burner, to a ferrous oxide reduction zone to provide the heat necessary for carrying out the endothermic reactions in said zone. <Desc / Clms Page number 69> 20. A direct reduction process according to claim 1, for reducing iron oxides to metallic iron, characterized in that: a hydrocarbon fuel is gasified in a gasification zone at high temperature with a gas containing ox / gene , the ratio between the oxygen contained in the gas and the carbon contained in the hydrocarbon is between 0.05 and 0.20, so as to produce hydrogen and carbon and the oxidation products of the hydrogen and carbon, said gasification reaction being carried out in a dancing fluidized bed of reduced iron particles, said carbon produced by said gasification reaction being deposited in an amount of 10 to 30% by weight of said carbon relative to the weight of iron; (2) the gases from this gasification zone include large amounts of CO and H2 and are reducing in nature with respect to iron oxides and are sent from said gasification zone to a gasification zone. reduction of ferrous oxides in which they come into contact with a fluidized bed of ferrous oxides which are reduced to metallic iron endothermically while the reducing gases are partially oxidized and are then sent to a fluidized bed of oxides ferric in which they reduce these oxides to ferrous oxides, the iron in each of said fluidized beds flowing from the ferric oxide zone to the ferrous oxide zone and to the gasification zone, (3) the heat necessary for these endothermic gasification and reduction reactions being supplied <Desc / Clms Page number 70> by sending carbon-coated iron particles, taken from the gasification zone, to an external burner with a transfer line, in which they are brought into contact with a preheated gas containing oxygen, part of the carbon coating burning exothermically forming CO and CO2 and generating a large amount of heat and the residence time of the particles in the burner being 0.4 to 1.0 seconds, the aforementioned heat being adsorbed in the form of sensible heat by the particles of reduced iron coated with carbon, which raises their temperature above the temperature of about 38 to about 260 C above the temperature of the reduction and gasification zones, while burning 2 to 8% of the carbon deposited on the iron, (4) and the reduced iron particles thus heated are recycled from the transfer line burner to the ferrous oxide reduction zone and to the gasification zone for provide the heat necessary for carrying out the endothermic reactions in these zones, 21. A method according to claim 19, characterized in that the zones for reducing the ferric oxides and the ferrous oxides are maintained at a temperature between 704 and 816 C, the aforementioned reaction zone is maintained at a temperature between 871 and 982 C and the burner is maintained at a temperature between 871 and 1204 C. 22. A method according to claim 19, characterized in that the redactant combustion gas supplied to said burner has a CO2 / CO and H20 / H2 ratio respectively. <Desc / Clms Page number 71> from 0.75 - 1.0 and from 0.5 to 1.0. 23. - Process according to claim 19, characterized in that the CO 2 / CO and H 2 O / H 2 ratios in the gas leaving the reduction zone of the ferrous oxides are respectively between 200 and 250 and between 150 and 200. 24.- Process according to claim 20, characterized in that the temperatures are maintained between 593 and 871 C in the zones of reduction of ferric oxides and ferrous oxides, between 816 and 982 C in the gasification zone and between 982 and 1204 C in the burner, 25. A process, in substance, as described above, with reference to the accompanying drawings.