MXPA01005883A - Method and apparatus for the direct reduction of iron oxides - Google Patents

Abstract

Method for the direct reduction of mineral iron inside a vertical reduction furnace (10) of the type with a gravitational load, wherein the reducing gas flows in counter-flow with respect to the material introduced into the furnace, comprising the following steps:the mineral iron is fed from above into the furnace (10), a mixture of high temperature gas consisting of reducing gas based on H2 and CO is injected, and the reduced mineral is removed from the furnace (10). The mixture of gas is introduced into at least one zone (14) of the furnace (10). The mixture consists of the process gas, which emerges from the same furnace, and of additional gas arriving from an outside reforming circuit. Additionally, natural gas (preferably methane) and/or oxygen can be admixed thereto.

Description

M ETHOD AND APPARATUS FOR THE RE DUCTION DI STRAIGHT OF OXY TWO OF H I ERRO FIELD OF THE INVENTION This invention concerns a process for producing metallic iron starting from mineral iron, where the iron is present in the form of oxides and the relative apparatus, which comprises a reduction furnace, which can have one or more inputs for the reducing gas and within which, the process of direct reduction of iron (DRI) is carried out. The reducing gas is obtained by mixing a part of the process gas, which emerges from the reduction furnace, with the additional gas coming from an external reforming circuit.

BACKGROUND OF THE INVENTION The state of the art includes direct reduction processes, which use the injection of hydrocarbons in the reducing gas stream, to allow the reaction of reforming the methane in the furnace with the H2O and CO2 in the gas; direct reduction processes are also known, which use the injection of hydrocarbons with C > 5 directly towards the furnace in the area between the injection of the reducing gas and the output from above of the burned gas. From the following patent documents, other processes for the direct reduction of mineral iron are known: US-A-2, 1 89,260, US-A-3,601, 381, US-A-3, 748, 1 20 US -A-3, 749, 386, US-A-3, 764, 1 23, US-A-3, 770,421 US-A-4, 054,444, US-A-4, 1 73,465, US-A-4, 1 88, 022 US-A-4, 34, 1 69, US-A-4,201, 571, US-A-4, 270,739 US-A-4, 74,585, US-A-4, 528,030, US-A- 4, 556.41 7 US-A-4, 720,299, US-A-4, 900, 356, US-A-5, 064,467 US-A-5,078,788, US-A-5, 387,274, and US-A- 5,407, 460. The state of the art also includes processes in which hot metallic iron is produced in an arrow-type reduction furnace, with a vertical and gravitational fl ow of the material, which is subsequently sent to the melting furnace by means of a transport system. tire closed in an inert atmosphere. EP-A0262353 discloses a method and apparatus for producing hot spongy iron in a vertical arrow reactor, wherein the reducing gas to reduce the ore is generated in a reformer unit by the catalytic conversion of a mixture of steam and natural gas to a reducing gas mostly composed of CO and H2. Process or spent gas, which leaves the reactor reduction zone, flows to an extinguishing cooler, where it is cooled and dried, and to a carbon dioxide unit, where the CO2 is removed. A back pressure regulator allows excess gas to be removed to keep the reactor and associated equipment at a desired pressure. Therefore, the process gas is substantially uniquely "cleansed" of H2O and CO2, in order to recover a part of the active gas (H2 and CO), which was contained in the spent gas. Consequently, a re-qualification of the process gas is not performed by the method and apparatus described in EP-A-0262353. What happens is simply that something that is no longer necessary (ie, H2O and CO2) is removed from the process gas, while the remaining part is reintroduced into the main gas supply pipe, where the reducing gas flows. produced by the steam reformer unit.

BRIEF DESCRIPTION OF THE INVENTION The method for producing metallic iron by the direct reduction of iron oxides and the relative apparatus according to the invention are set forth and characterized in the respective main claims, while the dependent claims describe other characteristics. innovators of the invention. The method according to the invention consists in bringing the mineral iron, of different granulometry, into contact with a feed gas in a reduction furnace of the arrow type, in which both the gas and the material are fed continuously, so that a vertical / gravitational flow of material is created and direct reduction of the mineral is achieved. The material can be discharged from the reactor, either cold or from >; hot preference, to be sent subsequently to a smelting furnace, or so that it can be converted to hot briquette iron (HBI) or cooled and converted to direct reduction iron (DRI). The reduction furnace is equipped with means for feeding the metallic iron and means for discharging the reduced metallic iron; it is equipped with at least one inlet manifold for injecting the reducing gas in correspondence with a reaction zone or reactor inside the furnace. The reducing gas sent to the reactor contains injected hydrocarbons in the stream after the partial combustion of hydrogen and carbon monoxide with oxygen and is obtained by mixing a part of the process gas, which leaves the reduction furnace, with gas additional arriving from a circuit of exterior reformation. In a variant, the hydrocarbons are injected before the partial combustion is reached, in order to raise the temperature of the gas introduced into the reactor. According to another variant, the hydrocarbons are injected at least partially into an area between the reduction zone and the area where the reduced material is discharged. In all cases, the injected hydrocarbons cooperate to reduce the iron oxide (FeO) to metallic iron, generating more H2 and CO.

The direct reduction of the iron oxides is achieved in two different continuous stages within the reduction reactor. In a particular embodiment, the furnace is provided with a first stage, defined as the pre-heating and pre-reduction stage, where the fresh iron oxides, that is, those newly introduced in the furnace, come into contact with a mixture of reducing gas, consisting of partially burned gas, coming from the underlying part of the furnace and fresh hot gas, that is, gas introduced from the outside, which leads from a collector carrying fresh reducing gas and possibly CH4 or other natural gas . The first stage takes place in a first corresponding zone arranged in the upper part of the furnace. In the second stage, the appropriate reduction stage, the complete reduction of the iron oxides is reached, due to the action in the oxides, already partially reduced in the first stage, of a mixture of reducing gas with H2 base. and CO and at least one hydrocarbon, preferably natural gas, injected into the middle zone of the reduction reactor. This second step takes place in a corresponding second zone disposed below the first zone. The two inlets for the furnace through which the gas is introduced, can be regulated independently both in the flow of fresh reducing gas and in the addition of natural gas in the stream; introduced. Moreover, the inlet temperature of the two reducing gas streams can be regulated independently of the injected O2 before they enter the reduction reactor. The oxidation reaction necessary to raise the temperature of the gas leads to a change in the level of oxidation of the gas, from normal values of 0.04-0.08 to 0.06-0.15. The following ratio is intended for the oxidation level of the reducing gas: Nox = (H2O + CO2) / (H2O + CO2 + H2 + CO) Er the second reaction zone of the furnace, where the reduction of the oxides is completed of iron, a gas with a high content of H2 and CO is generated and with an oxidation level between 0. 1 5 and 0.25 due to the reduction reactions of the iron oxides with H2, CO and CH4. Once this gas has left the second reaction zone, it enters the first reaction zone, located above, and mixes with the hot gas injected into the first zone to pre-heat and pre-reduce the oxides of; iron. The gas that emerges from the reduction reactor is partly recirculated and partly used as fuel. The recirculated gas has a volume composition within the following fields: H2 = 20-41%, CO = 1 5-28%, CO2 = 1 5-25%, CH4 = 3-1 0%, N2 = 0-8%, H2O = 2-7%. According to a characteristic of the invention, the gas feeding the reduction reactor consists of a mixture of natural gas, recirculated gas, also a process gas or upper gas, which leaves the reactor by itself and reformed gas; the recirculated gas is pre-heated to a temperature between 650 ° C and 950 ° C; the gas that emerges from the preheater is, in turn, mixed with fresh reformed gas and subsequently with air, or air enriched with oxygen, or pure oxygen, to carry out a partial combustion of the H2 and CO in the reducing gas, in order to raise the temperature to values between 800 ° C and 1 1 50 ° C, preferably between 1 000 ° C and 1 1 50 ° C; and the level of oxidation of the resulting gas} The feed of the kiln is between 0.06 and 0.1. The methane represents between 6 and 20% by volume of the reducing gas mixture.

When the feed gas comes into contact with the reduction zone with the hot, partly reduced material, which therefore consists partly of metallic iron and partly of iron oxides, a highly endothermic reaction occurs. Extete also an endothermic reaction in the preheating and pre-reduction zone when the gas comes into contact with the iron oxide. An advantage of this invention is that the first preheating and pre-reduction zone extends, which allows the transformation of Ematite (Fe2O3) into Wustita (FeO) more quickly. The entire reactor works at a higher and above all constant average temperature throughout both zones, both the pre-reduction and reduction zones, encouraging a higher reaction speed, with a consequent effect of reducing consumption and increasing productivity. In the case where the furnace has two inputs for the introduction of the reducing gas, the first inlet is located at a fixed distance (x) with respect to the second inlet, which is located in the middle part of the furnace, in correspondence with the second reduction zone. This distance (x) is conveniently between 1 and 6 meters, preferably between 2 and 4 meters, to encourage reactions in the most suitable zone between reducing gas and iron oxides. The first gas inlet also has the function of pushing the gases that come from the second reduction zone towards the center of the furnace, in order to create a uniform distribution of the gas in the reactor section. According to one variant, there are multiple, or more than two, «/ Inputs for the reducing gas in the furnace. The first gas stream reducer is injected towards the middle part of the reactor, in the appropriate reduction zone, while the other currents are introduced in the zone eintre injection of the first gas stream and the exit of the burned gas, in the upper part of the furnace . This intermediate zone will be called the pre-heating and pre-reduction zone for the material based on iron oxide. The gas flow in the reactor thus composed, allows to have the zone of reduction and complete pre-reduction at a temperature as constant as possible, and to have a gas inside the furnace that always has a high reducing power, encouraging a higher productivity and a lower consumption of gas; this also allows to improve the final metallization of the product. Moreover, in this way, the iron oxides reach the already partially reduced reduction zone, thus encouraging the termination of the final reduction reaction of FeO to Fe.

BRIEF DESCRIPTION OF THE INVENTIONS These and other features of the invention will become clear from the following description of some preferred forms of the mode, given as a non-restrictive example with the help of the accompanying Figures, in which: FIG. 1 a shows in diagram form, an apparatus for the direct reduction of iron oxides according to the invention in a first form of embodiment; Fig. 1 b shows in diagram form, an apparatus for the direct reduction of iron oxides according to the invention in a second form of embodiment; Fig. 2 is a first variant of a furnace used in the apparatus in Fig. 1 a; Fig. 3 is a diagram showing the temperature inside the oven shown in Figs. 1 a and 2; Fig. 4 shows a second variant of a furnace used in the apparatus in FIG. 1 a; Fig. 5 is a diagram showing the temperature inside the oven shown in Fig. 4; and Fig. 6 shows another variant of the apparatus in Fig. 1 a.

DETAILED DESCRIPTION OF PREFERRED MODALITIES With reference to FIG. 1 a, an apparatus for the direct reduction of iron oxides according to the invention comprises a reduction furnace of the arrow type or reduction reactor 10, which in turn comprises an upper mouth 1 1 for feeding from above, through which the ore (iron oxides) is capable of being introduced, a first pre-heating and pre-reduction zone 12, a second zone, or middle zone 14, where the final reduction reaction of the iron oxides takes place, and a lower zone, or discharge zone 1 5, with a truncated cone-like shape, ending at the bottom in a lower opening 16 through which the iron is discharged. The iron-based metal oxides are introduced into the reactor 10 in the pellet form or raw mineral in the appropriate sizes; the iron contained therein is usually between 63% and 68% by weight. At the end of the process according to the invention, the iron contained in the reduced material leaving the reactor 10 is normally between 80% and 90% by weight. In correspondence with the two zones 1 2 and 1 4 of the reactor 1 0, there are two independent inputs 1 7, respectively 1 8, through which it is suitable to introduce a gas mixture, as described in greater detail below. In its upper part, above the zone 12, the reactor 1 0 is provided with an opening 1 9 through which the burned gas or process gas flows out. This gas usually has the following characteristics: composition: H2 = 20-41%, CO = 15-28%, CO2 = 1 2-25%, C H4 = 2-1 0%, N2 = 0-8%; H2C = 2-1 5%, temperature between 500 ° C and 700 ° C; Oxidation level between 0.3 and 0.50, preferably between 0.40 and 0.45; and a reduction ratio R between 1 and 1 .8, where the reduction ratio is taken as: R == (H2 + CO) / (H2O + CO2) In the mode shown in Fig. 1 a, the furnace 1 0 comprises only one reaction zone 14 and only one inlet 1 8 through which the reducing gas is injected into the furnace.

In both versions, that is, the one shown in Fig. 1a and the one shown in Fig. 1b, the burnt gas emerging from the reactor 10 is sent through a pipe 20 to a cooling unit 21, suitable for use in the first stage of the process. ? > recover the heat that can be delivered; from the unit cooling 21, through another pipe 22, arrives at a cooling and condensation unit 24. In this unit 24, the burned gas is washed in water at a temperature between 40 ° C and 65 ° C, and the amount of Water present in the gas itself is partially removed. The percentage of water that remains in the gas at the outlet of the unit 24 is between 2% and 7%. The gas in the outlet of the unit 24 is sent through a pipe 30 in part to a pre-heater 36, in part to a catalytic reformer 44, to be used as fuel, and in part to a compressor 26. The gas arising from the compressor 26 is in turn used in part as a recirculation gas and is sent, through a pipe 28, into the unit 21, and partly, through a pipe 46, is mixed with a natural gas comprising methane (CH4) or pure methane, which comes from line 34 in a ratio of about 4: 1 (ie, per In part of the natural gas there are approximately four parts of gas coming from the pipe 46) and it is introduced into the reformer 44, so that the reaction of reforming methane (CH4) with H2O and CO2 can begin. The part of gas that is sent to the unit 21 through the pipe 28 is pre-heated, and then it is sent through a pipe 32 to the pre-heater 36, where it is pre-heated additionally to a temperature between 650 ° C and 950 ° C. CH4 can also be injected into line 32. The gas that emerges from pre-heater 36, which has a delivery rate of between 600 Nm3 / ton of DRI and 1 500 Nm3 / ton of DRI, is mixed in a pipeline 38 with the gas coming from the reformer 44 through a pipe 50. The gas resulting from this mixture is divided into two parts and distributed in two pipes 40 and 41, connected to the inlets 17 and 18 of the furnace 1 0. The delivery of reducing gas is controlled in each zone 1 2, 14 by means of regulating valves 55 and 56. In each pipe 40 and 41, air or air enriched with oxygen or pure oxygen and natural gas are injected in variable percentages, in order to achieve a partial combustion of CO and H2 and raise the temperature of the gas. A stream of CH4 or natural gas is injected into the gas before it is introduced into the reactor. In a variant, shown by a striped line in the Fígs. 1 a and 1 b, the CH is injected before reaching the partial combustion, in order to raise the temperature of the gas introduced in the reactor. The CH4 can also be introduced in an area between the reduction zone 14 and the discharge cone of the material, through a pipe 81. In this case, before entering zone 14, where the reduction reactions are carried out, the partially injected CH4 cools the reduced iron, before the latter is discharged.

The valves V1-V11 are located in correspondence with the different conduits of the plant, so that the flow can be controlled selectively. The resulting mixtures are then introduced into the reduction zone 14 and optionally into the pre-heating and pre-reduction zone. With respect to the oven 10 with two inlets (Fig. 1a), for each zone 12 and 14, the corresponding gas mixture is regulated in an independent and independent manner. To be more exact, the gas flow in the first zone 12 is between 500 Nm3 / ton of DRI and 800 Nm3 / ton of DRI and enters the reduction reactor 10 with a temperature between 800 ° C and 1150 ° C, preferably between 1000 ° C and 1150 ° C, while the gas flow in the second zone 14 is between 1000 Nm3 / ton of DRI and 1500 Nm3 / ton of DRI and also enters the reduction reactor 10 with a temperature of between 800 ° C and 1150 ° C, preferably between 1000 ° C and 1150 ° C. The consumption of oxygen, which is necessary to raise the temperature of the reducing gas from 650 ° C-950 ° C to 800 ° C-1150 ° C, intended as pure oxygen that was contained in the air, if air was also injected, it is between 8 Nm3 / ton of DRI and 60 Nm3 / ton of DRI, preferably between 20 and 60 Nm3 / ton of DRI. The CH4 consumption is between 50 and 120 Nm3 / ton of DRI, preferably between 90 and 110 Nm3 / ton of DRI. In volume, CH represents between 6 and 20% of the reducing gas mixture introduced into the reactor.

The: reactions involved in the reduction zone 14 are as follows: Fe O + CH4 = Fe + 2H2 + CO (1) Simultaneously, in the same zone 14, the following reduction reactions take place with hydrogen and monoxide carbon: FeO + H2 = Fe + H2O (2) FeO + CO = Fe + CO2 (3) The consequence of these endothermic reactions is that the temperature of the gas in the reduction zone decreases from 800 ° C-1 1 50 ° C up to 700 ° C-900 ° C, still maintain the reaction temperature higher than in furnaces in the state of the art, and the gas leaving the reduction zone 14 has an oxidation level of between 0.1 5 and 0.35 and a reducing power of between 1.1 and 2.8. The reactions involved in the pre-reduction zone 1 2 are as follows: Fe2O3 + H2 = 2FeO + H2O (4) Fe2O3 + CO = 2FeO + CO2 (5) In the lower zone 1 5, shaped like a truncated cone It is also possible to introduce gas containing natural gas to control the final carbon in hot reduced iron at values between 1.5% and 3.0%. In a variant as shown in Fig. 2, instead of having a single lower part with a shape similar to a truncated cone, the furnace 1 0 has at least; two, and preferably three or four lower ends, with a shape similar to a cone or truncated cone 1 5a, 1 5b and 1c, through which the reduced metal iron is discharged in a controlled and independent manner. In this case, the CH4 can also be introduced by means of the devices located in the intersection area of the truncated cone ends 1 5a, 1 5b and 1 5c, thus exploiting the geometric conformation of the system. The temperature development inside the 1 0 oven, both in the version shown in Fig. 1 a and also in the variant shown in Fig. 2, is shown in Fig. 3, from which it can be seen how the temperature is greater and more constant in the segment affected by the two zones 1 2 and 14. According to another variant shown in Fig. 4, instead of having two inputs to introduce reducing gas, the oven 1 0 is provided with a plurality of inputs, more than two. In this case, a first gas stream is introduced into the lower inlet 1 8 through the pipe 41, a second gas stream is introduced into the inlet 1 7 through the pipe 40 and other gas streams, each of which can be regulated in an autonomous manner, they are introduced through pipes 42 and corresponding inlets arranged between the inlet 1 7 and the upper opening 19. The temperature development inside the furnace 10, in the variant shown in FIG. Fig. 4, is shown in the diagram in Fig. 5, from which it can be seen how the temperature is higher and more constant in the complete segment affected by the pipes 40, 41 and 42. According to another variant, shown in Fig. 6, the reducing process gas can be recirculated without passing through a catalytic reformer, but a part of the gas leaving the reduction furnace 10 is pre-heated in the exchanger 21 and, by means of line 32, it is mixed with natural gas, for example, CH4, and is sent to the pre-heater 36. In this variant, the gas leaving the furnace 1 0 has a temperature between 500 ° C and 600 ° C and has the following composition: H2 = 30-36%, CO = 20-25%, CO2 = 20-25%, CH4 = 2-7%, H2O = 1 5-25%; with an oxidation level between 0.4 and 0.5. The gas, in this way pre-heated and mixed with natural gas, leaves the pre-heater 36 at a temperature of between 650 ° C and 950 ° C, is subsequently divided into several reducing gas streams, towards each of which oxygen and natural gas are injected before they enter the reduction furnace 1 0, in order to raise the temperature of the inlet gases to a value between 800 ° C and 1 1 50 ° C. Another part of the gas leaving the reduction furnace 10 is used as fuel to generate heat in the pre-heater 36, by means of the pipe 30. The reactions that take place in the reduction furnace 10 are for pre-heating and pre-reducing the mineral in the upper zone 1 2 and to reduce the Wustite (FeO) with CH 1 H 2 and CO in the reduction zone 14. In a variant, CH 4 can be injected in the zone between the reduction zone 14. and the truncated cone-shaped discharge end 1 5; in this sea it was, the CH4 is pre-heated, cooled the reduced material, and arrives in the reduction zone 14 cooperating with the methane contained in the reducing gas injected in the reaction zone 14.

With this system it is possible to eliminate the catalytic reformer 44, and at the same time, the plurality of gas inlets allows to improve the temperature profile of the reduction furnace 1 0, making it more uniform and accelerating the reduction reactions. Obviously, it is possible to make modifications and additions to the method for the direct reduction of mineral iron and the relative apparatus as described heretofore, but these will remain within the scope and scope of the invention.

Claims (26)

1. REIVI N DICACIONES 1 . The method for the direct reduction of mineral iron within a vertical reduction (10) furnace of the type with a gravitational load, which comprises the following steps: feed the mineral iron from above to the furnace (10), inject a high temperature reducing gas mixture based on H2 and CO in said furnace (10), said reducing gas flowing to counter-flow with respect to said mineral iron introduced in the furnace, the process gas (or top gas) is removed from above said furnace (10), and the reduced metal is removed from the lower part of said hoe (10), where said reducing gas is obtained by mixing, in variable parts depending on the requirements of the process iron reduction, at least a part of said process gas and additional gas coming from an external reforming circuit (44), the method being characterized in that said process gas is divided into two parts, of which a first part is direct au n pre-heater (36) to be re-introduced subsequently to said furnace (10) and a second part is directed to said reforming circuit (44) to be re-qualified and sent to said furnace (10), mixing together the gas emerging from said pre-heater (36) and said catalytic reformer (44) to form a mixed gas before injection thereof into said furnace (10).
2. 2. The method as in claim 1, characterized in that, before being divided into two parts, said process gas is washed, cooled and subjected to a substantial reduction in the amount of water contained therein.
3. 3. The method as in claim 1, characterized in that said preheater (36) increases the temperature of said first part of process gas to a value comprised between 650 ° C and 950 ° C.
4. 4. The method as in claim 1, characterized in that, before being introduced into the furnace, said mixed gas is mixed additionally with O2 or air enriched with O2, in order to achieve partial combustion of H2 and CO present in the reducing gas and in this way, raise the temperature in the reduction zone of the furnace to values between 800 ° C and 1 1 50 ° C, advantageously between 1 000 ° C and 1 1 50 ° C.
5. The method as in claim 1, characterized in that at least one hydrocarbon is added to said mixed gas before its injection in the reduction zone of the furnace.
6. 6. The method as in claim 5, characterized in that said hydrocarbon consists of CH, in order to cooperate in the reduction of the iron oxide to metallic iron, at the same time that it generates H2 and additional CO.
7. The method as in claim 1, characterized in that said reducing gas is introduced into at least two zones (1 2, 14) of said furnace (10) arranged one above the other, in order to reach, in a manner controlled, a first stage of pre-heating and pre-reduction in the upper part (1 2) of the oven (10) and a second stage of the final reduction in the lower part (14) of the oven (10).
8. 8. The method as in claim 6, characterized in that said methane represents between 6 and 20% by volume of said reducing gas mixture.
9. The method as in claim 7, characterized in that the delivery, in different percentages, of said mixed gas is controlled in the different reduction zones (1 2, 14) together with the length of said oven (10).
10. The method as in claims 5 and 7, characterized in that said hydrocarbon consists, preferably, of natural gas and in that said hydrocarbon in said mixed gas is provided and controlled independently in the different reduction zones (1 2, 14) together with the length of said oven (10). eleven .
11. The method as in claim 7, characterized in that said mixed gas is heated independently in the different zones (12, 14) together with the length of said oven (10). 2.
12. The method as in claim 1, characterized in that said mixed gas injected into said reactor has an oxidation level between 0.06 and 0.25.
13. The method as in any of the preceding claims, characterized in that additional CH4 is injected in part in said furnace (10) in an area between said lower part (14) and an underlying discharge zone (1 5).
14. 14. An apparatus for the direct reduction of mineral iron comprising a vertical reduction furnace (10) of the type with a gravitational load, to achieve iron ore reduction reactions therein, feed means (11) for feed the mineral iron in said furnace (1 0) from above, first injection means (1 7, 1 8) to inject a high temperature gas mixture, consisting of reducing gas based on H2 and CO, first medium (1 9) to remove the process gas (or upper gas) from the top of said furnace (10), and a second means (16) to remove the reduced ore from the bottom of said furnace (10), in wherein the first mixing means is provided for mixing, in variable portions according to the requirements of the iron reduction process, at least a part of said process gas with additional gas coming from a reforming circuit (44) disposed outside of said furnace (1 0), to obtain said reducing gas, the apparatus being characterized in that dividing means (28, V8, 46, V9) are provided to divide the process gas into two parts, of which a first part is capable of being transferred to a heater (36) to be re-introduced subsequently in said furnace (10) and a second part is able to be directed to said reforming circuit (44) to be re-qualified and sent to said furnace (10), and first mixing means (38, 50) are provided to mix together the gas leaving the pre-heater (36) and the gas arising from said catalytic reformer (44) to form a mixed gas before the injection thereof to said oven (1 0).
15. The apparatus as in claim 14, characterized in that washing and cooling means (21, 24) are provided upstream of said dividing means, so that said process gas is capable of being washed, cooled and subjected to a substantial reduction in the amount of water contained therein.
16. The apparatus as in claim 14, characterized in that heating means (36) are provided for pre-heating said process gas to a temperature of between 650 ° C and 950 ° C, before it is mixed with said additional gas .
17. The apparatus as in claim 14, characterized in that second mixing means (V2, V4) are provided to further mix said mixed gas with O2 or air enriched with O2, in order to achieve partial combustion of H2 and the CO present in the reducing gas and thus raise the temperature in the reduction zone of the furnace to values between 800 ° C and 1 1 50 ° C, advantageously between 1 000 and 1 1 50 ° C.
18. 18. The apparatus as in claim 14, characterized in that means are provided for injecting at least one hydrocarbon into said reducing gas or together with it into the reduction zone of the furnace. 9.
19. The apparatus as in claim 18, characterized in that said hydrocarbon consists of CH4, in order to cooperate in the reduction of iron oxide to metallic iron, at the same time generating H2 and CO added.
20. The apparatus as in claim 14, characterized in that means (1 7, 1 8) are provided for introducing said reducing gas into at least two: reduction waves (1 2, 1 4) of said furnace (1 0) arranged one above the other in order to achieve, in a controlled manner, a first stage of pre-heating and pre-reduction in the upper part (1 2) of the furnace (10) and a second stage of final reduction in the lower part (14) of said furnace (10). twenty-one .
21. The apparatus as in claim 20, characterized in that regulation means (55, 56) are provided to regulate the introduction, also in different percentages, of said reducing gas in the different zones of; reduction (1 2, 14) together with the length of said furnace (1 0).
22. 22. The apparatus as in claims 1 8 and 20, characterized in that at least two elements for mixing the reducing gas and hydrocarbon are provided upstream of the inlets to said furnace (10), in correspondence with said reduction zones (1 2, 14), in order to supply a mixture, in which the hydrocarbon is provided and controlled independently and autonomously in each of said zones (1 2, 14).
23. 23. The apparatus as in any of claims 14 to 22 inclusive, characterized in that said removal means (1 5) comprise at least two ends (1 5a-1 5c) with a cone-like shape or a truncated cone.
24. 24. The apparatus as in claim 23, characterized in that said ends. (1 5a-1 5c) with a cone-like shape or a truncated cone are tapered downwards, and each is provided with a corresponding lower opening (1 6a-1 6c) through which said metallic iron can be discharged selectively in a controlled and independent manner.
25. The apparatus as in any of claims 14 to 24 inclusive, characterized in that second injection means (81) are provided to at least partially inject CH4 towards said furnace (10) in an area between said second removal means ( 15) and the lower part of said reaction zones (14).
26. 26. The apparatus as in claims 23 and 25, characterized in that said second injection means (81) are arranged in an area of intersection between said ends (15a-15c) with a shape similar to a cone or a truncated cone. SUMMARY The method for the direct reduction of metallic iron within a vertical reduction furnace (10) of the type with a gravitational load, wherein the reducing gas flows counter-flow with respect to the material introduced into the furnace, which comprises the following steps: the mineral iron is fed from above to the furnace (10), a high temperature gas mixture consisting of reducing gas based on H2 and CO is injected, and the reduced ore is removed from the furnace (10). The gas mixture is introduced into at least one zone (14) of the furnace (10). The mixture consists of the process gas, which emerges from the same furnace, and of additional gas coming from an external reforming circuit. Additionally, natural gas (preferably methane) and / or oxygen can be mixed thereto.