TEXT OF THE DESCRIPTION

FIELD OF THE INVENTION

Production of carbon and stainless steel requires two basic steps: ironmaking and steel making.

The ironmaking process transforms ferrous materials into metallic iron by oxyreduction. Ironmaking in traditional blast furnaces requires the use of coke, acting at once as combustible and source of reducing gases, resulting in the production of pig iron. Ironmaking in direct reduction units requires the use of reducing gas, typically syngas, i.e., a mixture of carbon dioxide (CO) and hydrogen (H2), resulting in direct-reduced iron (DRI) or hot briquettes iron (HBI).

The steelmaking process transforms iron into steel, by lowering the carbon content of iron. This is achieved by processing pig iron, DRI, HBI, or scrap metal either in basic oxygen furnaces or electric arc furnaces, which lower the carbon content by decarburizing iron through the use of oxygen and argon gases.

The ironmaking process is a particular source of environmental and sanitary concern due to its creation of high levels of pollution.

STATE OF THE ART

In traditional blastfurnaces, due to the dual role of coke as combustible and source of reducing gases, the chemical reactions taking place at high temperature between the coke, the iron ore, and the hot air blasts result in production of many pollutants, which are interspersed within the large flow of CO2 produced by the combustion. The sanitary and environmental impact of ironmaking via direct reduction units is much lower than that of blast furnaces thanks to removal of coke, but production of pollutants remains strong due to the prevalent use of syngas (mixture of carbon monoxide (CO) and hh from steam reforming) as the reducing agent in direct contact with the iron ores.

The transition to direct reduction units based on the sole use of H2 as reducing agent (H-DR) can further mitigate pollution and could potentially result in a carbon-neutral steel production (but only if coupled the use of energy drawn from certified grids entirely served by renewable sources). The physics principle of direct reduction with sole H2 is described in the 1932 research paper by H. Kamura [Kamura:1932ce] The industrial use of this method was first pioneered at the turn of the century in the context of the Circored project [Nuber:2006vt1· In 2019, almost simultaneously, the development of H-DR units was announced by Primetals with Voestalpine Stahl Donawitz in June [Primetals:2019tt1 and by ArcelorMittal Germany with Midrex Technologies in September [ArcelorMittal:2019ubj. The recent papers by Otto et al. [Otto:2018kp] and by V. Vogl, M. Ahman and L. J. Nilsson [Voql:2018iz] analyze the economics of this process and conclude that costs of the H-DR units is still not competitive with respect to that of blast furnaces.

A scope of the present invention is to describe an innovative “hydrofurnace” with the goals of establishing a new production chain for steel, based on the following goals and principles:

^• Complete avoidance of the use of coal;

^• Supply of energy and carbon through the sole use of natural gas (NG);

^• Restriction of the use of NG to:

> Direct combustion with air or, preferrably, with oxygen (O2), so that the gas resulting from the combustion contains, other than water vapor, H2O, the highest and purest possible concentration of CO2, such as to ease the separation of said CO2 from other components of the exhaust stream, the separation of CO2 from H2O being well understood and characterized in prior art, and such as to ease the capture of the highest possible fraction of said CO2, and its local storage, said direct combustion resulting in the production of large amounts of CO2 being required to provide heat for the steel production process and to provide energy for all other iron- and steelmaking process needs, including the production of H2 via electrolysis and/or proton exchange membranes (PEM) for the direct reduction of the iron ores; this is why the name of the invention can be intended as “hydrofurnace”

> Possibly, in addition, NG cracking [Abanades:2016gu] for direct production of H2 and carbon, the carbon being required for mixing with the metallized iron for steel production, and NG cracking providing also an alternative method for production of the H2 required for direct reduction of the iron ores;

^• Complete reutilization of the CO2, captured and stored as resulting from NG combustion, in enhanced oil recovery processes, following transportation through pipelines or ships, the CO2 is returned underground, resulting in a carbon neutral steelmaking process;

^• Minimized production of pollutants in every step of iron- and steel-making, and provision of means for efficient secondary containment of pollutants;

^• Direct production at competitive costs of hot iron briquettes (HBI) of very high (>95%) metallization, as required for the production of the best quality steel.

BRIEF DESCRIPTION OF THE INVENTION

The innovative device described by the present invention is a direct reduction- smelter unit conceived to provide at once large throughput capacity of the highest quality iron for steel making, minimization of pollution, enabling of complete recovery of C0 ₂ .

In particular, the innovative hydrofurnace described by the present invention comprises at least and external jacket and a refractory insulation layer contained therein characterized in that inside the refractory insulation layer is housed an internal jacket realized in a material able to withstand at least the fusion temperature of 1800 K and being a conductor material, the space between said refractory insulation layer and the internal jacket, in the lower part of the plant, is a combustion chamber, in said chamber a mixture of combustible and comburent are injected through dedicated pipe and distribution systems, the internal volume of said internal jacket is the reduction and smelting chamber and is subdivided in two different volumes, the reduction zone and the smelting zone, which operate at different temperatures, a top opening permits the loading of iron ores in the smelting chamber, in correspondence of the transition between the reduction zone and the smelting zone is realized a dedicated pipes and distribution system for the inlet of a reducing gas, so the combustion chamber and the reduction and smelting chamber being totally separated from the internal jacket, so having a complete separation of the gas providing the heat for reduction and smelting from the gas serving as reducing agent.

In particular the combustible is NG or, preferably, ChU and the comburent is air or, preferably, O2.

In particular, the bottom part of the metal jacket - in correspondence with the smelting zone housed therein - is surrounded and rests on trusses preferably made of refractory material, to support the lower part of the metal jacket when the device is brought into temperature, so the trusses are completely housed in the combustion chamber.

More in particular, in a preferred embodiment the trusses are directly coupled with soft metal (i.e. a combination of aluminum, copper, steel) pads , which can be fused to and provide the required extra space, due to the thermal expansion of the metal jacket, when said metal jacket is brought to high temperature and expands.

The upper part of the metal jacket - in correspondence with the reduction zone housed therein, is direct contact with the refractory insulator on the external side and is insulated by a graded internal refractory insulator on the internal side. Between the external upper side 3b of the metal jacket and the refractory insulator (that is the refractory material) there is a space, where are comprised pads also realized preferably in i.e. a combination of aluminum, copper, steel, which can be fused to provide the required extra space to the metal jacket, when said metal jacket is brought to high temperature and expands.

The reduction zone has its bottom part in the shape of an inverted cone, with the injection point of the inlet of the reducing gas at the tip of the inverted cone, so that the reducing zone is operated as a fluidized bed reactor for the solid iron ores, under the action of the reducing gas stream acting as the fluidizing agent for the ores. Please note that the activation of operations of the hydrofurnace, obtained by bringing the metal jacket and all of its contents to high temperature, will typically occur only one time (as known from prior art), with the ensuing operation lasting for typically more than a decade, so when the metal jacket is brought into high temperature the pads will be fused to accommodate the thermal expansion of the metal jacket, said expansion completely sealing off the space, achieving a near complete thermal separation of the combustion chamber from the upper section of the metal jacket enclosing the reduction zone of the reduction and smelting chamber.

In particular the metal jacket is preferably realized in tungsten or molybdenum.

In a preferred embodiment the combustion gases are a NG, preferably CPU, and air, or preferably O2, that are injected in the combustion chamber through the pipes and distribution system for NG/CH ₄ and for air/02.

In a preferred embodiment the reducing gas for the iron ores is H2.

In the lower part of the metal jacket there are inserted a gangue duct for the removal of gangue, and a smelting duct for the removal of the smelted iron, a receiving ladle is present for the loading of the smelted iron.

An exhaust line is present connected with the combustion chamber, for extracting the resulting combusted gas, that is a mixture of CO2 and H2O when the gases injected in the combustion chamber are CPU and O2.

A counter-current heat exchanger is connected to an exhaust line for treating the mixture of CO2 and H2O to substantially completely recover its enthalpy, this being achieved by completely recovering the excess heat in counter-current heat exchangers.

The recovered heat is used to pre-heat the NG and 02 streams that is injected through dedicated lines and the hh stream that is injected through line.

A vacuum-pressure unit (VPSA) or a temperature-pressure unit (TPSA) is also present to treat the mixture of combusted gas of CO2 and H2O to completely separate water and CO2.

In a preferred embodiment, the reduction zone is further subdivided to accommodate a loading zone on the top of the reduction zone. In a preferred embodiment, the metal jacket extends to enclose both the loading zone and the reduction zone.

In a further preferred embodiment, the vertical extension of the metal jacket stops in correspondence of the transition between the loading zone and the reduction zone. To better explain the functioning of the above described innovative device, a method according to the hereabove description and device is explained for putting the hydrofurnace in operation in the description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

This and more advantages obtained thanks to the here described innovative hydrofurnace device will be further described hereinafter with reference to non- limitative examples, which are provided for explanatory, non-limitative purposes in the accompanying drawings. These drawings illustrate different aspects and embodiments of this invention and, where appropriate, the structures, components, materials and/or similar elements are indicated in the different figures with similar reference numbers, in particular:

- figure 1 illustrates a preferred embodiment of the device described by the present invention;

- figure 2 and 3 illustrates the same preferred embodiment in a 3D simulation and details thereof.

While the invention is susceptible to various modifications and alternative constructions, some of the illustrated embodiments are shown in the drawings and will be described below in detail. It must be understood, however, that there is no intention to limit the invention to the specific illustrated embodiments, but, on the contrary, the invention intends to cover all the modifications, alternative constructions and equivalents that fall within the scope of the invention as defined in the claims.

The use of "such as", "etc.", "or" indicates non-exclusive alternatives without limitations, unless otherwise indicated.

The use of "includes" means "includes, but is not limited to", unless otherwise indicated.

DESCRIPTION OF THE DRAWINGS

In a preferred embodiment, according to fig. 1 , the innovative hydrofurnace 100 described by the present invention comprises at least an external steel jacket 1 and refractory insulation layer 2 contained therein, which in turn contains a metal jacket 3, made of metal able to withstand the fusion temperatures of iron (1800 K) and steel (1650 K), such as, but not limited to, tungsten (fusion temperature 3700 K) and molybdenum (fusion temperature 2900 K). The bottom part of the metal jacket 3 rests upon trusses 4 made of refractory material like those of the refractory insulator in one embodiment, directly coupled with soft metal (a combination of aluminum, copper, steel) pads 5, which can be fused to give way and provide the required extra space when the metal jacket 3 is brought to high temperature. The space between the trusses 4 surrounding the bottom part of the jacket is the combustion chamber 6 where a mixture of NG, preferably CH4, and O2 is injected in the combustion chamber through the pipes and distribution system 7 for NG and to 8 for O2.

The design and geometry of the combustion chambers are devised such as to ease the complete mixing of combustible and comburent gases, and to ease their complete combustion before the exhaust gas is extracted through exhaust line 9.

The combustion of CH4 and O2 provides the heat necessary for the iron reduction and smelting, resulting in a stream of combusted gas is composed solely of CO2 and H2O, and exhausted through the exhaust line 9. The reduction and smelting chamber 10 is the volume delimited by the metal jacket 3, and can be thought as subdivided in two different volumes, the reduction zone 11 and the smelting zone 12, which operate at different temperatures. The highest temperature are reached in the smelting zone 12, given that the metal jacket 3 is in direct contact on the external side with the combustion chamber 6 and with the smelting zone 12 on the internal side. The temperatures in the reduction zone 11 are lower, due to the metal jacket being in direct contact with the refractory insulator 2 instead of the combustion chamber on the external side and being insulated by a graded internal refractory insulator 13 on the internal side.

The iron ores (ferrite, hematite) are loaded through the top opening 14. They are reduced to metallic iron during their transit through the reduction zone 11 by the reducing gas H2, injected directly in the reduction and smelting chamber 10, in correspondence of the transition between the reduction zone 11 and the smelting zone 12, through its dedicated pipes and distribution system 15.

The metallic iron is smelted during its transit through the smelting zone 12. Any gangue is removed through the gangue duct 16. The smelted iron is removed through the smelting duct 17 and loaded into the receiving ladle 18.

In a preferred embodiment, the reduction zone 11 is further subdivided to accommodate a loading zone 11a on the top of the a lower part reduction zone 11b. In a preferred embodiment, the top part of the metal jacket 3b extends to enclose both the loading zone 11 a and the lower part reduction zone 11 b.

The lower part 3a of the metal jacket 3 rest on trusses 4 and comprises the smelting zone 12 in the internal part of the jacket.

In another a preferred embodiment, the vertical extension of top part of the metal jacket 3b stops in correspondence of the transition between the loading zone 11a and the lower part reduction zone 11b.

The key innovation of the hydrofurnace is the complete separation of the gas providing the heat for reduction and smelting 7,8 from the gas serving as reducing agent 15. This is possible thanks to the innovative introduction of the metal jacket 3, which physically separates the combustion chamber 6 from the reduction and smelting chamber 10. The resulting combusted gas, a mixture of CO2 and H2O, extracted from the exhaust line 9, is first treated to substantially completely recover its enthalpy, as can be achieved by completely recovering the excess heat in counter- current heat exchangers and transferring said heat to the NG and O2 streams to be injected through 7,8 and to the H2 stream to be injected through 15.

Upon recovery of the enthalpy, the combusted gas, a mixture of CO2 and H2O, is treated in vacuum-pressure swing adsorption (VPSA) or temperature-pressure swing adsorption units (TPSA) to completely separate water, which can be recycled in the process, and CO2, which is liquefied and then transported to its final destination via pipelines or ships, for use in enhanced oil recovery and for the concurrent sequestration in adequate geological formations.

In fig. 2 and 3 there are some important details highlighted, in particular fig. 2 is the same as fig. 1 , that is the same embodiment of the invention in 3D view, that is much better to understand the position of the combustion chamber 6, that is delimited outside from refractory material 2 and form the trousses 4 and on the inner part form the metal jacket 3, as said, the metal jacket 3 rests on his lower part on said trusses 4 made preferably fo said refractory material that is in one embodiment the material of the refractory insulator 2; so the combustion chamber 6 and the reduction and smelting chamber 10 being totally separated from the internal jacket 3, so having a complete separation of the gas providing the heat for reduction and smelting from the gas serving as reducing agent. The reduction and smelting chamber as said before is the volume delimited by the metal jacket 3.

To better explain the functioning of the above described innovative device, a method according to the hereabove description and device is explained for putting the hydrofurnace 100 in operation in the description of the drawings. injection in the chamber 6 through the pipe and distribution system 7 of the combustible NG/CH4 and through the pipe and distribution system 8 of air/02; bringing the metal jacket 3 into high temperature, so the pads 5 will be fused to accommodate the thermal expansion of the metal jacket, said expansion completely sealing off the space 20, achieving a near complete thermal separation of the combustion chamber 6 from the upper section of the metal jacket 3 enclosing the reduction zone of the reduction and smelting chamber 10. loading of iron ores in the reduction and smelting chamber 10 through the top opening 14; injection of reducing gas in the reduction and smelting chamber 10 in correspondence of the transition between the reduction zone 11 and the smelting zone 12 through its dedicated pipes and distribution system 15; extraction of gangue form the top part 3b of the metal jacket 3 from the gangue duct 16, removal of smelted iron form a smelting duct 17, a receiving ladle 18 is present for the loading of the smelted iron.

The above described method wherein the combustion gases are a mixture of NG, preferably CH4, and air, or, preferably, 02, and the reduction gas is syngas, a mixture of CO and H2, or, preferably, H2.

And more, the method comprising the phases of: extraction of the resulting combusted gas in the chamber 6, that is a mixture of C02 and H20, from the exhaust line (9); treating said mixture to substantially completely recover its enthalpy by completely recovering the excess heat in counter-current heat exchangers; transferring said heat to the pre-heat NG and 02 streams to be injected in the combustion chamber through the dedicated pipe and distribution systems 7 and 8; transferring said heat to pre-heat the reducing gas stream, preferrably H2, to be injected through the dedicated pipe and distribution system 15; treating, upon recovery of the enthalpy, the combusted gas, a mixture of C02 and H20, in vacuum-pressure swing adsorption (VPSA) or temperature- pressure swing adsorption units (TPSA) to completely separate H20, which can be either recycled for H2 generation or safely disposed of, and C02, which is liquefied and then transported to its final destination via pipelines or ships, for use in enhanced oil recovery and for the concurrent sequestration in adequate geological formations.

So it appears clear how the present invention permits so solve all the hereinabove cited technical problems thanks to the innovative hydrofurnace 100 described by the present invention, with particular reference of the here described preferred embodiment, please note that any change in the order of the components, or in non substantially details of the operations, number of the valves, number/type of the tubes, kind of gas used, amount of production, dimension of the plant, operative temperatures, number of operation cycles, dimension of the single constitutive elements, materials used for the realization of the system, are to be considered only non-significant modifications of some realizations embodiment of the present invention and have to be considered covered by the object of the present invention as here above described and better explicated with reference to the annexed claims.