WO2025021301A1

WO2025021301A1 - Improved process for the smelting reduction of iron ores

Info

Publication number: WO2025021301A1
Application number: PCT/EP2023/070735
Authority: WO
Inventors: Luca Eugenio Riccardo BASINI; Francesco BARBETTI
Original assignee: NextChem S.p.A.
Priority date: 2023-07-26
Filing date: 2023-07-26
Publication date: 2025-01-30

Abstract

Process for improving the sustainability of the smelting reduction (SR) of iron ores which makes use of synthetic gas (syngas) produced by means of Short Contact Time Catalytic Partial Oxidation (SCT-CPO) in a process utilizing off-gases derived from the reduction of iron ores and, optionally, hydrogen and or CO and oxygen produced with electrolytic means. The process uses also oxygen produced by cryogenic separation of air or by electrolysis. The syngas produced via SCT-CPO can also be used in Blast Furnace and Direct Reduction processes for reducing Iron Ores.

Description

IMPROVED PROCESS FOR THE SMELTING REDUCTION OF IRON ORES

The present invention concerns a process for improving the sustainability of the smelting reduction (SR) of iron ores. This improved process can be also combined with other processes for the reduction of iron ores. The improved process makes use of synthesis gas (syngas) produced by means of Short Contact Time Catalytic Partial Oxidation (SCT-CPO) utilizing gaseous hydrocarbons containing streams including off-gases derived from the reduction of iron ores and, optionally, hydrogen and or CO and oxygen produced with electrolytic means.

BACKGROUND OF THE INVENTION

The greenhouse gases (GHG) and pollutant emissions in the steel industry remain relevant, and ongoing efforts are considering the use of the so-called “green” sources, like “green” electrical energy and renewable fuels and reactants for replacing the fossil ones. In particular, the use of hydrogen, produced with electrolytic means utilizing renewable electric energy sources, is often considered as a preferred molecule for use in the iron ores reduction processes.

However, it is noted that the production of 1 Nm³ of green hydrogen through electrolysis would requires ca 4.5-5.0 kWh, and that the reduction of Iron Ores would require ca. 50-55 kg di H2 for producing 1 ton of raw steel with direct reduction (DR) processes. This would mean that a power station of ca. 1 GW would be required for an iron ores reduction plant producing 3 MTPY of raw steel. This is clearly an amount of power that would be difficult to obtain with windmills or photovoltaic panels (which of course would also have intermittent energy production) or hydroelectric energy sources, in a reasonable layout for an industrial environment.

Moreover, the Iron Ores reduction reactions require high temperatures (typically around 950 °C) and while the CO induced reduction reactions are slightly exothermic the corresponding hydrogen induced reduction reactions are slightly endothermic. Hence, additional energy would be required for performing the reduction of Iron Ores with pure renewable hydrogen. This solution would probably not be applicable in most of the iron ores and steel making contexts. Instead, integrated processes utilizing renewable energy sources but also hydrocarbon containing feedstocks recovered from off-gas emissions of industrial and chemical activities, could provide reductant gases mixtures, i.e., syngas mixtures that, when properly produced and utilized, will allow to reduce the pollutant and the greenhouse gas (GHG) emissions improving the energy efficiency in the great majority of the industrial conditions of the iron ores reduction process.

The present invention concerns a new process allowing this achievement in smelting reduction (SR) processes also integrated with DR processes, with blast furnace (BF) processes and/or with other chemical and energy processes. PRIOR ART

Figures 1A and IB show process schemes of the SR of iron ores according to the prior art.

The SR of iron ores is performed in two steps inside a reduction shaft or by an array of fluid bed reactors followed by a melter gasifier. Initially, the iron ore is partially reduced to sponge iron in the shaft furnace 1 by means of reducing gas. In the following step, the sponge iron is completely reduced and melted in a melter-gasifier vessel 2. More in detail, the pelletized ferrous minerals are introduced in the reduction shaft 1, or in fluid bed reactors represented with 1 in Fig. IB, in contact (typically at 800-850°C and 3-5 bar) with a reduction gas flow, produced in the melter gasifier 2 through the sub- stoichiometric combustion of coal. This reduction gas comprises 65-70% CO, 20-25% Fh, and 2-4% CO2 on a volume basis.

After leaving the melter gasifier 2, the hot reducing gas is mixed with a recycled gas from the reduction shaft 1.

Additional gas leaving the top of the shaft furnace, that still has a relatively high calorific value, may be used as an export gas for other purposes, i.e., to produce thermal and/or electric energy and/or for use in Direct Reduction Iron (DRI) productions.

The separation between the step of iron reduction and the step of iron melting/coal gasification allows the utilization of a wide variety of coals and, differently from the reduction processes of iron ores utilizing a Blast Furnace, the coking and the sintering plants are not required.

As shown in Figs. 1A and IB, the process scheme comprises a reduction shaft or an array of high temperature fluid beds in the upper part while in the lower part takes place the process of smelting and collection of liquid metal at ca. 1550 °C.

Coal, limestone and other inorganic oxides are fed in the upper zone of the melter gasifier 2, where they quickly reach the temperature of 1000-1200 °C. Oxygen is introduced into the gasification zone through tuyeries by burning coal and producing Carbon Monoxide which, together with the reaction heat, completes the metal reduction and the melting processes.

In addition, the use of pure Oxygen greatly reduces emissions of NOx and other polluting compounds. Since the gas produced in the melter gasifier is overproduced and has a high calorific value and is rich in Carbon Monoxide, Hydrogen and CO2, it is used for the generation of thermal and electrical energy or, alternatively, it is sent to a further Direct Reduction (DR) plant.

The utilization of the off gases produced in the reduction processes of iron ores is not limited to the smelting reduction and involves other iron ores reduction technologies, such as those utilizing blast furnaces (BF) or the direct reduction (DR) process, as these too produce large amounts of gases that cannot be entirely reutilized in the same industrial processes. BRIEF DESCRIPTION OF THE INVENTION

The present invention concerns a new process for the reduction of iron ores in metallurgical plants, and particularly for improving the energy efficiency and reducing the pollutants and the greenhouse gas emissions (GHG), particularly the CO2 emissions. This result is achieved by a process for smelting reduction of iron ores comprising the steps of: a) Introducing iron ores into at least one pre-reduction furnace or at least one pre-reduction reactor; b) Charging the pre-heated and pre-reduced iron ores and a carbonaceous material into a smelting reduction furnace; c) Blowing oxygen gas into said smelting reduction furnace through an array of nozzles located in the lower part of said smelting reduction furnace, whereby said pre -reduced iron ores are further reduced and an exhaust gas is produced; d) Introducing said exhaust gas produced in said smelting reduction furnace into said at least onepre -reduction furnace or pre-reduction reactor; and e) Discharging reduced molten iron and slag from the bottom of said smelting reduction furnace; characterized in that said exhaust gas produced in said smelting reduction furnace is: i) partially or completely mixed to a syngas stream before being introduced into said at least one pre-reduction furnace or pre-reduction reactor, said syngas stream being produced in a Short Contact Time - Partial Catalytic Oxidation process that uses as a feedstock a mixture of hydrocarbon sources, ii) partially or completely mixed to said mixture of hydrocarbon sources used as feedstock of said Short Contact Time - Catalytic partial oxidation process.

According to an aspect of the invention said oxygen blown into said smelting reduction furnace is produced by one or more of the following methods: electrolysis of water, electrolysis of carbon dioxide, cryogenic separation from air, vacuum swing adsorption or pressure swing adsorption separation from Air.

According to an aspect of the invention, when oxygen is produced by electrolysis of water and hydrogen is also produced, said hydrogen is mixed with said syngas and introduced into said pre-heat and pre-reduction furnace with syngas and with said exhaust gas produced in said smelting reduction furnace to carry out the pre-reduction of said iron ores. The electrolysis can be performed according to any of the following methods: alkaline electrolysis (AE), polymer electrolyte membranes electrolysis (PEME), solid oxide cell electrolysis (SOEC).

According to another aspect of the invention, said mixture of hydrocarbon sources used as feedstock for the SCT-PCO process comprises one or more of: natural gas (NG), blast furnace gas (BFG), coke oven gas (COG), direct reduction gas (DRG), basic oxygen furnace gas (BOFG), and other off-gases produced in metallurgical plants and/or biogases and/or other hydrocarbon containing off-gases produced by chemical and/or refining applications.

The reduced iron particles produced in the smelting reduction furnace can be further processed in electrical arc furnaces (EAF see Treatise on Process Metallurgy, Volume 3; Chapt. 1.5. 2018), submerged arch furnaces (SAF see Journal of Sustainable Metallurgy (2018) 4:77-94). An advantage of the process of the invention is the possibility of utilizing the SCT-PCO process to produce syngas from different gaseous reactant mixtures, and particularly the off-gases produced by the iron ores reduction processes.

Noteworthy, these feedstocks cannot be utilized by the current catalytic syngas production technologies (namely, steam reforming, autothermal reforming and the combination of these two named combined reforming) and, if utilized by non-catalytic technologies (namely non- catalytic partial oxidation) would require much higher oxygen consumption, a lower energy efficiency and would produce a syngas with a lower quality.

In the present description the smelting reduction furnace is designated also as “melter gasifier” and the pre-heat and pre -reduction furnace designates either a shaft furnace or one or more fluid beds.

DESCRIPTION OF THE FIGURES

The invention is described also with reference to the attached drawings, wherein:

Figures 1 A and B: Simplified process scheme utilized for SR of the prior art, including (A) a shaft furnace or (B) an array of fluid beds.

Figure 2: (A): Qualitative drawing of the enthalpy/temperature contributions determined by reactions [1], [2], [3-4], [5] and [6] occurring along a tubular reactor including a fixed catalytic bed operated at low mass flow velocity; the solid line represents the total enthalpy variation.

(B): Qualitative drawing of the enthalpy/temperature contributions determined by reactions [1], [2], [3-4], [5] and [6] occurring along a SCT-CPO reactor with truncated cone geometry, including a fixed catalytic bed operated at high mass flow velocity; wherein the solid line represents the total enthalpy variation.

Figure 3: Scheme of the internal zones of a SCT-CPO reactor with a truncated cone reaction zone.

Figure 4: Simplified SR process scheme in which electrolysis produces some of the oxygen required in the melter gasifier while hydrogen (AE o PEM) and the carbon monoxide (SOEC) are mixed with the hot gases produced in the melter gasifier and added to the shaft furnace or to an array of fluidized beds.

Figure 5: Simplified SR process scheme in which the iron lump ores/pellets are loaded in either a shaft or one or more fluidized beds where a partial reduction of the iron ores takes place tanks to a reducing gas stream produced in: i) a melter gasifier (2), ii) an AE, PEME, SOEC electrolyzers, iii) a short contact time catalytic partial oxidation reactor, and wherein the oxygen stream produced by the electrolyzers is also added to the melter gasifier and/or to the short contact time catalytic partial oxidation reactor.

Figure 6: Simplified process scheme integrating Smelting Reduction and Direct

Reduction utilizing a reducing gas stream produced in: i) a melter gasifier, ii) AE, PEME, SOEC electrolyzers, iii) a short contact time catalytic partial oxidation reactor, wherein the oxygen stream produced by the electrolyzers is also added to the melter gasifier and/or to the short contact time catalytic partial oxidation reactor.

Figure 7: Simplified process scheme integrating Smelting Reduction and Blast Furnace for iron ores reduction in which the partial reduction of the iron ores takes place tanks to a reducing gas stream produced in: i) a melter gasifier (2), ii) AE, PEME, SOEC electrolyzers, iii) a short contact time catalytic partial oxidation reactor, wherein the oxygen stream produced by the electrolyzers is also added to the melter gasifier and/or to the short contact time catalytic partial oxidation reactor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides process solutions for a further reduction of coal utilization and possibly for a complete replacement of coal in smelting reduction. This is achieved by integrating electrolytic hydrogen and oxygen productions and syngas production. This last is obtained with short contact time catalytic partial oxidation (SCT-CPO), which also allows the utilization of the off-gases produced by the iron ores reduction processes, thus contributing to a strong reduction of the GHG and pollutant emissions and improving the overall energy efficiency of the processes.

The SCT-CPO reactor is particularly advantageous for utilizing various feedstock that could not be used as feedstock in the catalytic technologies (e.g., steam methane reforming - SMR and autothermal reforming - ATR) and would be utilized in a rather inefficient way by non- catalytic technologies (e.g., partial oxidation - POx).

The SCT-CPO reactor used in the process of the invention has some specific features that make it effective for these applications, while different reactors utilizing tubular and fixed bed reactors, fluidized bed, moving beds, or bubbling bed reactors cannot be applied in the conditions here described.

The SCT-CPO technology is described in numerous patent documents, including WO2016016257 (Al), WO2016016256 (Al), WO2016016253 (Al), W02016016251 (Al), WO 2011151082, WO 2009065559, WO 2011072877, US 2009127512, WO 2007045457, WO 2006034868, US 2005211604, WO 2005023710, WO 9737929, EP 0725038, EP 0640559.

Among the scientific and technical publications the following are mentioned; Catalysis Today, 106 (1-4), p. 34, Oct 2005, Catalysis Today, 117 (4), (2006) 384-393; DOI: 10.1016/ j.cattod.2006.06.043, IntechOpen, htp://dx.doi.org/10.5772/48708, Ind. Eng. Chem. Res. 2013, 52, 17023-17037; https ://doi .org/10.102 l/ie402463m

The term “short contact time catalytic partial oxidation” (SCT-CPO) has a well-defined meaning either in the scientific, technical, and patent literature. As used in the present invention, however, certain aspects are quite specific for what concerns the combination of the characteristics of the reactor and the operation conditions.

It has been found that the utilization of a specific SCT-CPO reactor and operation conditions, improves the possibility of producing synthesis gas for the reduction of iron ores in the smelting reduction. It has also been found that smelting reduction can be integrated with other processes devoted to the reduction of iron ores, and particularly those utilizing fluidized bed and moving bed solutions.

Noteworthy, the SCT-CPO reactor here described allows: i) the utilization of gaseous off-gases emitted by the reduction shafts, by the fluidized beds as well as by the blast furnaces, by the coke ovens and by the basic oxygen furnace, ii) the utilization of other feedstocks such as natural gas, other gases having a biomass origin (e.g., biogas), off-gas feedstocks produced by other chemical and ore refining industries. Moreover, this specific SCT-CPO reactor also allows the utilization of other CO2 rich feedstocks.

In addition, this specific SCT-CPO reactor requires moderate pre-heating of the reactant mixtures, and the heat required for this moderate pre-heating can be obtained by recovering the heat contained in other off-gas streams and/or recycle streams, hence avoiding the utilization of fire heaters and avoiding the CO2 emissions that this use would produce.

For what it concerns the SCT-CPO technology and for explaining the unique reactivity features that allows the integration of this technology with the process of the invention, the following aspects are to be considered.

The thermo-chemical properties of the reaction environment produced in short contact time conditions during the SCT-CPO in a heterogeneous catalytic fixed bed reactor fed with a premixed CH₄, Steam, CO2 and O2 stream, are described considering the system composed by the by equations [1-5]:

CH₄ + 202 = C0₂ + 2H2O AH° = -803.0 kJ/mol [1]

CH₄ + ‘/20₂ = CO + 2 H₂ AH⁰ = -38 kJ/mol [2]

CO + H₂O co₂ + H₂ AH° = -41.0 kJ/mol [3]

CO₂ + H2 ^ CO + H₂O AH° = 41.0 kJ/mol [4]

CH₄ + CO₂ = 2CO + 2 H₂ AH° = 247.3 kJ/mol [5]

CH₄ + H₂O = 3H₂ + CO AH° = +206 kJ/mole [6]

The exothermic total oxidation reaction [1] has the highest probability to occur at the beginning of the bed, while the endothermic steam-CCh reforming reactions [5] and [6] and the mildly endothermic (RWGS) reaction [4] have the highest probability to occur in the following zone. By increasing the reaction temperature above 83O°C reaction [4] is favored with respect to reaction [3], and also favored with respect to steam-CCh reforming [5] and [6].

However, we found that the extent and the localization of these reactions inside the catalytic bed is greatly affected by physical and chemical factors. Total combustion [1] is the most competitive reaction on noble metal base (Rh, Ru, Ir, Pt, Pd) catalysts at "relatively low temperatures" below 750 °C and at high O2 partial pressure.

These are typically the conditions produced at the beginning of the catalytic beds in tubular reactors operated at “high” contact time values (e.g., above 1 s). In these cases, we found that the thermal profiles of the reaction environments are determined by the strongly exothermic reaction [1] with a minor contribution of reactions [2], [3] and [4], followed by the strongly endothermic steam-CCh reforming reactions [5] and [6].

These conditions originate very large axial temperature gradients and moreover, the energy release associated to total combustion also determines the propagation of the heterogeneous reactions into the gaseous phase originating a rather unselective radical chemistry, leading to unsaturated molecules and soot formation.

We have found that with tubular reactors the catalytic partial oxidation reactions cannot be performed at high pressures since reaction [1] cannot be controlled and propagates reactions into the gaseous phase with the risk of flame ignition, particularly at high pressure (e.g., above 10 ATM) but in any case, producing some radical reactions leading to the formation of unsaturated hydrocarbons precursors of solid carbonaceous compounds.

Instead, it has been found that it is possible that the temperatures of solid catalyst reach values higher than 1000°C, while the gas remains relatively cool by utilizing a reaction environment geometry that allows to reduce the contact time at the entrance of the catalytic bed to few milliseconds. This allows the expansion of the reaction volume when the temperature and the mole flow increase due to the progressing of the reaction. This effect is obtained by adopting a truncated shape geometry of the catalytic bed.

Accordingly, it has been found that in these short contact time conditions, the gaseous hydrocarbon conversion largely depends on the O2/C ratios, while is almost unaffected by the addition of steam and CO2. This addition, instead, modifies the H2/CO ratios in the produced synthesis gas, clearly indicating that the reactivity is largely determined by the direct partial oxidation [2] and by the RWGS reaction [4].

Figure 2 shows qualitative representation of the Enthalpy/Temperature profiles obtained at (A) low mass velocity, high contact time, tubular geometry of the catalytic bed and (B) high mass velocity, short contact time, truncated cone geometry of the catalytic bed.

Figure 3 shows the main zones of the SCT-CPO reactor, including a truncated cone reaction zone; these include: a) a mixing inlet zone, b) a first thermal shield pre-heating zone, c) a reaction zone, d) a second thermal shield, e) a reactor exit zone,

The angle a shown in the Figure 3 is clearly lower than 85° and preferentially lower than 80° and preferentially comprised between 75° and 30°.

The other geometrical features, namely the: i) truncated cone inlet radius Rl, ii) the truncated cone exit radius R2, iii) the truncated cone length L and the catalytic bed filling are designed for allowing pressure drop values (AP) inside the catalytic bed between 0.1 and 10 ATM, and preferably between 0.5 and 5 ATM.

To this purpose, the ratios R1/R2 are comprised between 0.9 and 0.1 and preferably between 0.8 and 0.4, and the shapes of the filling of the catalyst bed are defined for minimizing the pressure drop conditions by utilizing pelletized or monolith structures and their combinations. It has also been noted that the existence of a non-thermal equilibrium between the gas and the solid phases. This has been explained considering that the chemical heat generated at the surfaces and emitted by radiation, is absorbed, and scattered much better by the solid than by the gaseous phase and is transferred along the catalytic bed from the hotter towards the cooler points, thus smoothing the solid surface temperatures. The main experimental observations on the thermo-chemical properties of the SCT environments, performed after optimization of the reaction environment characteristics, are synthesized as follows: i) the temperature of the solid phase raises steeply at the beginning of the bed and the temperature profiles are smoothed through radiative and conduction mechanisms in the axial and radial directions; ii) temperature differences are originated between the gas and the solid phases; iii) local surface temperatures values result higher than the adiabatic temperatures; and iv) gas temperatures are always lower than the adiabatic temperatures and gradually increase from the entrance to the exit of the bed.

It has also been found that part of the reaction heat is transferred towards the incoming reactants inside the first thermal shield zone and in this way a reactant pre-heating internal to the reactor is also achieved.

Accordingly, in the process of the invention the CO2 emissions are mainly related to the energy consumption required for: compressing the feedstock (compression energy that would be required for any syngas production technology), obtaining the O2 flow with an Air Separation Unit (ASU), obtaining H2 and O2 flows from steam/water electrolysis.

The use of the specific SCT-CPO reactors, catalysts, and operation conditions provide a unique mean for obtaining CO- and fU-rich syngas suitable for reduction shaft of the smelter gasifier technologies, and for other reactor solutions such as fluidized bed solutions useful for the reduction of iron ores. The use of specific SCT-CPO reactors can improve the overall efficiency and production rate of SR processes utilizing reduction shaft or fluidized bed.

The specific SCT-CPO reactor solutions here described utilize a truncated cone geometry of the catalytic bed and can operate at: i) Gas Hourly Space Velocity Values comprised between 30,000 - 500,000 h ¹ and preferentially between 50,000 - 250,000 h ¹, ii) inlet temperatures of the reactant mixtures comprised between 100 and 450°C, preferably between 150 and 400 C, iii) inlet pressures comprised between 1.5 ATA and 50 ATA, preferably for the purposes of this application between 2 and 10 ATA.

The catalysts can be any suitable material comprising a support with a pelletized or a monolith structure having active metal species onto their external surface. Examples of these catalysts, not limiting the possibilities of utilizing other materials, are described in WO 2022/263409 Al. More in detail, the SCT-CPO reactor has a first inlet section having a cylindrical shape consisting of an inlet, a mixing zone and a thermal shield zone, a second portion containing a catalytic bed having a truncated cone shape, and a third portion having a cylindrical shape with a diameter greater than the diameter of said first cylindrical portion, followed by a second thermal shield zone, wherein: a) in said second portion having the shape of a truncated cone the upper base is smaller than the bottom base; b) said upper base of said truncated cone is joined to said first cylindrical portion and said bottom base is joined to said third cylindrical portion; and c) the external angle (a) of said truncated cone at the upper base is lower than 85° and preferably lower than 75°.

The utilization of the specific SCT-CPO reactor solution here described also allows the utilization of the oxygen stream obtained by the electrolytic processes, thus further improving the integration between electric energy sources having a renewable character with other reactants useful in the production of synthesis gas.

These points are illustrated with the help of Figures 1, 4-7.

Figures 1 (A) and (B) describe, as already mentioned, two simplified schemes of the currently utilized smelting reduction process.

Figure 1 (A) shows that the lump ores/pellets are charged in a pre-heat and pre -reduction furnace, or shaft, (1) where the partial reduction of the iron ores takes place by means of a reducing gas stream produced in a smelting reduction furnace, or melter gasifier, (2). The partially reduced iron ores are charged in the melter gasifier (2) together with a carbonaceous material, typically coal. Oxygen is blown at the bottom of the melter gasifier through an array of nozzles, or tuyeres. Eiquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from shaft 1 goes through a scrubber (5). Part of the Hot Gas produced in the melter gasifier (2) goes through a scrubber (4), is combined with export gas released from shaft 1 and is exported. In a settling pond (6) dusts are separated from water.

Figure 1 (B) also describes a currently utilized process scheme in which lump ores/pellets are charged in an array of fluidized beds (1) where the partial reduction of the iron ores takes place by means of a reducing gas stream produced in the melter gasifier (2). The partially reduced iron ores are charged in the melter gasifier (2) together with coal. Oxygen is injected at the bottom of the melter gasifier through a tuyerie. Liquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from 1 goes through a scrubber (5). Part of the Hot Gas produced in the melter gasifier (2) goes through a scrubber (4), is combined with export gas released from shaft 1 and is exported. In a settling pond (6) dusts are separated from water.

Figure 4 shows a scheme of the improved process according to an embodiment of the invention and describes how the production of oxygen with an air separation unit (ASU) can be integrated with the production of oxygen and hydrogen obtained from water or steam with alkaline electrolysis (AE) or polymeric membrane electrolysis (PEME) or with the production of oxygen, hydrogen and carbon monoxide obtained with solid oxide cell electrolysis (SOEC) from steam and/or CO2.

More in detail, Figure 4 shows how the lump ores/pellets are first charged in a pre-reduction furnace or pre-reduction reactor or into an array of pre-reduction reactor, all designated with 1, where a partial reduction of the iron ores takes place by means of a reducing gas stream produced in a melter gasifier 2. The partially reduced iron ores are charged in the melter gasifier 2 together with coal. Oxygen is injected at the bottom of the melter gasifier through a tuyerie. Liquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from the pre-heat and pre-reduction unit 1 goes through a scrubber 5. A settling pond (6) is foreseen to separate dusts from water. Oxygen utilized in the smelter gasifier 2 can either be produced by an Air Separation Unit 7, by an electrolyzer 10 or by a combination of the two. Both a water (AE,PEM,SOEC) and a CO2 electrolyzer can be used. Electric Energy (E.E) is used to operate the Air Separation Unit 11 and the electrolyzer 10. The produced H2 (AE,PEM,SOEC) or CO (SOEC) can be added to the hot gas produced in the melter gasifier 2. Part of the mixed stream can be exported prior a scrubbing phase (4).

Figure 5 shows another embodiment of the improved process according to the invention and shows how the hydrogen and oxygen produced with electrolytic means are integrated in the syngas production process performed with an SCT-CPO reactor. The feedstock for the SCT- CPO process comprises different hydrocarbon containing gas sources. In this way the degree of pre -reduction in the shaft furnace 1 is increased and the amount of the Coal feed in the melter gasifier 2 is reduced. The reduction in the use of coal reduces both the emission of GHG and the emission of sulfur pollutants and of gaseous unsaturated hydrocarbons or particulates.

More in detail, Figure 5 shows that the partially reduced iron ores are charged in the melter gasifier 2 together with coal. Oxygen is injected at the bottom of the melter gasifier through a tuyerie. Liquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from 1 goes through a scrubber 5 and is then compressed in a compressor 6. Part of this export gas can be burned in a fired heater (7) prior to compression together with other fuels or off-gasses. The export gas is pre-heated in (7) together with other hydrocarbon sources, such as Natural Gas and Biogas, off gases such as Blast Furnace Gas (BFG), Coke Oven Gas (COG), Basic Oxygen Furnace Gas (BOFG), Direct Reduction Gas (DRG), refinery off-gasses, chemical processes off-gasses. Oxidant such as steam, CO2 and CO2 rich stream are preheated as well in the preheater 7. The preheated stream is mixed to an oxygen stream and fed to the SCT-CPO reactor 8. The produced hot syngas is mixed to the hot top gas coming from the smelter gasifier 2 after dust removal 3 and fed to the pre-reduction step 1. Part of the hot mixture can go through a scrubber 4 to be recycled in the process. A settling pond 9 is provided to separate dusts from water. The oxygen utilized in the smelter gasifier 2 and in the SCT-CPO reactor 8 can either be produced by an Air Separation Unit 11, by an electrolyzer (10) or by a combination of the two. Both the water (AE,PEM,SOEC) and the CO2 electrolyzers can be used and the produced H2 (AE,PEM,SOEC) or CO (SOEC) can be added to the hot syngas stream produced by the SCT-CPO reactor 8.

Figure 6 shows another embodiment of the improved process according to the invention, in which the gas exported by the SR process can be mixed with other hydrocarbon containing streams and used in a SCT-CPO process for producing a synthesis gas. This syngas is fed to the pre-heat pre-reduction shaft of a smelting reduction process and to other iron ore reduction processes utilizing fluidized bed technologies. The oxygen needed for the SCT-CPO process and for the melter gasifier can be produced either in an Air Separation Unit and/or with AE, PEM or SOEC electrolysis processes. The Hydrogen (AE or PEM) and/or Carbon Monoxide (SOEC) produced by the electrolytic means is added to the iron ores reduction reactors together with syngas.

More in detail, Figure 6 shows that the partially reduced iron ores from the pre-heat prereduction step 1 are charged in a melter gasifier 2 together with coal. Oxygen is injected at the bottom of the melter gasifier 2 through a tuyerie. Liquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from the pre-heat pre-reduction shaft 1 goes through a scrubber 5 and is then compressed in a compressor 6. Part of this export gas can be burned in a fired heater 7 prior to compression together with other fuels or off-gasses.

The process of this embodiment is integrated with a Direct Reduction Process where iron ores are charged from the top of a shaft furnace 14. The iron ores are reduced in said shaft by mean of a counter current reducing gas injected in the shaft through a tuyerie. At the bottom of the shaft, a gas stream is de-dusted in a scrubber 15 and recycled together with cold methane (NG) to cool down and carburize the reduced metal. The Direct Reduction Gas (DRG) leaves the shaft furnace 14 and goes through a scrubber 13. Part of this gas can be used as fuel in the preheater 7. The DRG is compressed in a compressor 12, mixed to the export gas coming from the pre-heat pre-reduction shaft 1 and pre-heated in the pre-heater 7 together with other hydrocarbon sources, such as Natural Gas and Biogas, and off gasses such as Blast Furnace Gas (BFG), Coke Oven Gas (COG), Basic Oxygen Furnace Gas (BOFG), Direct Reduction Gas (DRG), refinery off-gasses, chemical processes off-gasses. Oxidant such as steam, CO2 and CO2 rich streams are preheated as well in the preheater 7. The preheated stream is mixed to an oxygen stream ad fed to the SCT-CPO reactor 8. The produced hot syngas is split and routed to the DR shaft 14 and mixed to the top gas coming from the smelter gasifier 2 after dust removal 3 and fed to the pre-reduction unit 1. Part of the hot mixture goes through a scrubber 4 and is recycled in the process. A settling pond 9 is provided to separate dusts from water. Oxygen utilized in the smelter gasifier 2 and in the SCT-CPO reactor (8) can either be produced by an Air Separation Unit 11, by an electrolyzer 10 or by a combination of the two. Both water (AE,PEM,SOEC) and CO2 electrolyzers can be used. The produced H2 (AE,PEM,SOEC) or CO (SOEC) can be added to the hot syngas stream produced by the SCT-CPO reactor (8).

Figure 7 shows an embodiment of the invention which integrates SR operation with Blast Furnace operation.

The partially reduced iron ores from the pre-heat pre-reduction step 1 are charged in a melter gasifier 2 together with coal. Oxygen is injected at the bottom of the melter gasifier 2 through a tuyerie. Liquid metal and slug are discharged at the bottom of the melter gasifier. The export gas from 1 goes through a scrubber 5 and is then compressed in a compressor 6. Part of this export gas can be burned in a fired heater 7 prior to compression, together with other fuels or off-gasses.

The process is integrated with a Blast Furnace (BF) 14, where Sintered Iron Ores, limestone and coke are charged at top of the Blast furnace. Coke is produced from coal in a coke oven battery 13. The coke oven gas produced by the coke oven battery is mixed with the Blast Furnace Gas (BFG) leaving the BF 14 and compressed in a compressor 12. Part of the mixed gases are utilized as fuel in the preheater 7. The compressed BFG and COG are mixed to the export gas from unit 1 and pre-heated in the preheater 7 together with other hydrocarbon sources, such as Natural Gas and Biogas, off gasses such as Basic Oxygen Furnace Gas (BOFG), Direct Reduction Gas (DRG), refinery off-gasses, chemical processes off-gasses. Oxidant such as steam, CO2 and CO2 rich stream are preheated as well in the preheater 7. The preheated stream is mixed to an oxygen stream and fed to the SCT-CPO reactor 8. The produced hot syngas is split and routed to the BF shaft 14 and mixed to the top gas coming from the smelter gasifier 2 after dust removal (3) and fed to the prereduction step 1. Part of the hot mixture goes through a scrubber 4 and is recycled in the process. A settling pond 9 is provided to separate dusts from water. Oxygen utilized in the smelter gasifier 2, in the Blast Furnace 14 and in the SCT-CPO reactor 8 is produced by an Air Separation Unit 11 or by an electrolyzer 10 or by a combination of the two. Both the water (AE,PEM,SOEC) and the CO2 electrolyzers can be used, and the produced H2 (AE,PEM,SOEC) or CO (SOEC) can be added to the hot syngas stream produced by the SCT-CPO reactor 8.

As mentioned above, an advantage of the process of the invention is the use of the SCT-PCO process to produce syngas from different gaseous reactant mixtures, and particularly the offgases produced by the iron ores reduction processes. This type of feedstock cannot be utilized by the current catalytic syngas production technologies (namely, steam reforming, autothermal reforming and the combination of these two, named “combined reforming”) and, if utilized by non-catalytic technologies (namely non-catalytic partial oxidation) would require much higher oxygen consumption, a lower energy efficiency and would produce a syngas with a lower quality.

Furthermore, oxygen obtained from ASU and/or electrolysis is introduced into the gasification zone of the melter gasifier and/or in the SCT-PCO reactor. This contributes to the decarbonization concept inspiring the invention. In particular, the use of pure Oxygen greatly reduces emissions of NOx and other polluting compounds. When oxygen is produced by electrolysis of water, hydrogen is also produced, so that it can be mixed with the syngas and used in the pre-heat and pre-reduction unit.

Since the gas produced in the melter gasifier is overproduced and has a high calorific value and is rich in Carbon Monoxide, Hydrogen and CO2, it is used for the generation of thermal and electrical energy or, alternatively, it is sent to a further Direct Reduction (DR) plant.

Claims

1. Process for smelting reduction of iron ores comprising the steps of: a) Introducing iron ores into at least one pre-reduction furnace or at least one pre-reduction reactor; b) Charging the pre-heated and pre-reduced iron ores and a carbonaceous material into a smelting reduction furnace; c) Blowing oxygen gas into said smelting reduction furnace through an array of nozzles located in the lower part of said smelting reduction furnace, whereby said pre -reduced iron ores are further reduced and an exhaust gas is produced; d) Introducing said exhaust gas produced in said smelting reduction furnace into said at least one pre-reduction furnace or at least one pre-reduction reactor; and e) Discharging reduced molten iron and slag from the bottom of said smelting reduction furnace; characterized in that said exhaust gas produced in said smelting reduction furnace is: i) partially or completely mixed to a syngas stream before being introduced into said at least one pre -reduction furnace or pre-reduction reactor, said syngas stream being produced in a Short Contact Time - Partial Catalytic Oxidation process that uses as a feedstock a mixture of hydrocarbon sources, ii) partially or completely mixed to said mixture of hydrocarbon sources used as feedstock of said Short Contact Time - Catalytic partial oxidation process .

2. Process according to claim 1, characterized in that said oxygen blown into said smelting reduction furnace is produced by one or more of the following methods: electrolysis of water, electrolysis of carbon dioxide, cryogenic separation of air, vacuum swing adsorption or pressure swing adsorption of air.

3. Process according to claim 1 or 2, characterized in that said oxygen is produced by electrolysis of water and said electrolysis produces also hydrogen which is mixed with said syngas and introduced into said pre-reduction furnace or pre-reduction reactor with said exhaust gas produced in said smelting reduction furnace to carry out the pre -reduction of said iron ores.

4. Process according to any claim 1 - 3, characterized in that said electrolysis is performed according to any of the following methods: alkaline electrolysis (AE), polymer electrolyte membranes electrolysis (PEME), solid oxide cell electrolysis (SOEC).

5. Process according to any claim 1 - 4, characterized in that said mixture of hydrocarbon sources used as feedstock for the SCT-PCO process comprises one or more of: natural gas (NG), blast furnace gas (BFG), coke oven gas (COG), direct reduction gas (DRG), basic oxygen furnace gas (BOFG), and other off-gases produced in metallurgical plants including the off-gases produced by the melter gasifier and/or biogases and/or other hydrocarbon containing off-gases produced by chemical and/or refining applications.

6. Process according to any claim 1 - 5, characterized in that said syngas produced with said SCT-CPO process is fed to said pre-reduction shaft or pre-reduction reactor of a smelting reduction process and to a Direct Reduction process of iron ores.

7. Process according to any claim 1 - 5, characterized in that said syngas produced with said SCT-CPO process is fed to said pre-reduction shaft or pre-reduction reactor of a smelting reduction process and to a Blast Furnace process of iron ores to produce reduced iron.

8. Process according to any claim 1 - 7, characterized in that the exhaust gas produced in said SR process is mixed with other hydrocarbon containing streams and used in said SCT-CPO process for producing a synthesis gas.

9. Process according to any claim 1 - 7, characterized in that said short contact time catalytic partial oxidation process is carried out in a reactor on a catalytic bed comprising a portion with truncated cone geometry operated at a gas hourly space velocity from 30,000 to 500,000 h ¹; preferentially between 50,000 - 250,000 h ¹.

10. Process as according to claim 9, wherein the operating conditions the Short Contact Time - Catalytic Partial Oxidation process are the following:

- Inlet temperatures of the feedstock to the Short Contact Time - Catalytic Partial Oxidation reactor from 100 to 450 °C, preferably from 150 to 400 °C;

Inlet pressure of the reactant mixture in the Short Contact Time - Catalytic Partial Oxidation reactor from 15 to 2 kg/cm², preferably from 10 to 2.5kg/cm² and more preferably from 6 to 3 kg/cm².