NL2034821B1

NL2034821B1 - Novel process for the smelting of a blend of hot and cold metalliferous feedstock material yielding reduced carbon emissions

Info

Publication number: NL2034821B1
Application number: NL2034821A
Authority: NL
Inventors: Christiaan Louw Stephan; Jacobus Lötter Gabriel; Scholtz Terblanche Gerhardus
Original assignee: Metix Pty Limited
Priority date: 2023-05-15
Filing date: 2023-05-15
Publication date: 2024-12-02
Also published as: WO2024236508A1; CN121335993A; AU2024273586A1

Abstract

The invention relates to a process for the smelting of a metalliferous-containing feedstock material. More particularly, the invention relates to a process forthe smelting of a blend of hot 5 and cold metalliferous-containing feedstock material yielding a significant reduction in carbon emissions. According to a first aspect of the present invention, there is provided a process for the smelting of a metalliferous-containing feedstock material, the process comprising the steps of: - feeding a combination of hot and cold metalliferous-containing feedstock material, 10 reductant and fluxes into an electrothermal furnace by means of a plurality of adjustable feeding chutes; - heating the hot and cold metalliferous-containing feedstock material, reductant and fluxes in the electrothermal furnace at a temperature of between 1 400°C to 1 800°C to sufficiently melt the feedstock material, reductant and fluxes to a form a liquid metal 15 product, a liquid slag product and a CO-containing gas; - carbonizing the metal product by introducing a source of carbon into the electrothermal furnace; and - ensuring the continuous feeding of the combination of hot and cold metalliferous- containing feedstock material, reductant and fluxes by means of the adjustable feeding 20 chutes into the electrothermal furnace to control the power-to-feed ratio. (FIG.1)

Description

NOVEL PROCESS FOR THE SMELTING OF A BLEND OF HOT AND COLD

METALLIFEROUS FEEDSTOCK MATERIAL YIELDING REDUCED CARBON

EMISSIONS

FIELD OF THE INVENTION

The invention relates to a process for the smelting of a metalliferous-containing feedstock material. More particularly, the invention relates to a process for the smelting of a blend of hot and cold metalliferous-containing feedstock material yielding a significant reduction in carbon emissions.

BACKGROUND TO THE INVENTION

The Basic Oxygen Furnace (BOF) and Direct Reduced Iron (DRI) based processes are two different methods used for the production of steel.

The BOF process involves the use of a furnace that is charged with molten iron and scrap steel. Oxygen is blown into the furnace, which burns off impurities such as carbon, silicon, and phosphorus, leaving behind pure steel. The process is known as a "basic" oxygen furnace because it uses a basic (alkaline) lining to protect the furnace from the corrosive effects of the molten steel.

The DRI process involves the use of a reduction furnace to convert iron oxide pellets or lump ore into metallic iron. The process relies on the use of natural gas or coal to reduce the iron oxide to metallic iron, which is then cooled and formed into pellets or briquettes. The resulting

DRI is then used as feedstock, either hot or cold, for an electric arc furnace.

The BOF process requires a significant amount of energy to melt the iron and scrap steel and to blow oxygen into the furnace. In contrast, the DRI process uses natural gas or coal as its primary source of energy, which is more efficient than melting iron and scrap steel.

The BOF process produces high-quality steel with low levels of impurities, making it ideal for producing high-grade steel products. The DRI process, on the other hand, produces a lower- quality steel product that may contain higher levels of impurities. The DRI process is however a versatile process that can be used to produce a variety of steel products, including flat steel products, long steel products, and specialty steel products.

The BOF process produces significant amounts of carbon dioxide and other pollutants, while the DRI process produces fewer emissions and is considered a cleaner method of steel production.

Overall, the choice between the BOF and DRI processes depends on the specific needs of the steel producer. Although conventional BOF steelmaking processes are still a dominant steelmaking route, DRI-based processes have been gaining a larger share in industry, due to the shortage in scrap supply, fluctuation in the scrap price, and the low impurity content of DRI that improves the steel quality. In addition hereto, the DRI process offers strategic benefits to steel producers, such as the ability to produce steel from low grade ores and the flexibility to adjust production based on market demand. This makes it a preferred process for steel producers who want to remain competitive in a changing market.

However, both of these processes (although more so in the BF process) have a significant high carbon footprint.

A more recently developed solution is the employment of hydrogen instead of natural gas for the reduction of iron ores. The hydrogen direct reduction of iron ores produces mainly iron and water vapor but also CO:. This vapor is optimal for employment in high-temperature electrolysers for further hydrogen production. Presently, more than 90% of hydrogen is produced via fossil sources through various technologies generating carbon dioxide that needs to be treated, captured and stored. In this way, the best means of producing iron with the lowest impact on the environment is the production of hydrogen through electrolysis. By employing hydrogen produced via green energy sources as the reducing agent, carbon dioxide emissions can be reduced by 300 kg/t.

Accordingly, the known process routes have not demonstrated high efficiency yields concurrent with the use of low grade feed material whilst exhibiting reduced carbon emissions.

For purposes of the present specification, it will be appreciated that the following acronyms are used synonymously with the below referenced phrases.

EAF Electric Arc Furnace

FB Blast Furnace

CDRI Cold Direct Reduced Iron

DCF Direct Current Furnace

DRI Direct Reduced Iron

HBI Hot Briquetted Iron

HDRI Hot Direct Reduced Iron

OBF Open Bath Furnace

OSBF Open Slag Bath Furnace

SAF Submerged-Arc Furnace

OBJECT OF THE INVENTION

It is accordingly an object of the present invention to provide a novel process for the smelting of a blend of hot and cold metalliferous-containing feedstock material which overcomes, at least partially, the abovementioned disadvantages and limitations and/or which will provide a useful alternative to existing technology whereby low grade feed material is used whilst demonstrating a significantly lower carbon footprint with high efficiency yields.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a process for the smelting of a metalliferous-containing feedstock material, the process comprising the steps of: (I) feeding a combination of hot and cold metalliferous-containing feedstock material, reductant and fluxes into an electrothermal furnace by means of a plurality of adjustable feeding chutes; (ii) heating the hot and cold metalliferous-containing feedstock material, reductant and fluxes in the electrothermal furnace at a temperature of between 1 400°C to 1 800°C to sufficiently melt the feedstock material, reductant and fluxes to a form a liquid metal product, a liquid slag product and a CO-containing gas; (iii) carbonizing the metal product by introducing a source of carbon into the electrothermal furnace; and (iv) ensuring the continuous feeding of the combination of hot and cold metalliferous- containing feedstock material, reductant and fluxes by means of the adjustable feeding chutes into the electrothermal furnace to control the power-to-feed balance.

The invention provides for the metalliferous-containing feedstock material to be an iron- containing feedstock material.

Smelting in the present context is to be understood as the process of extracting iron from an iron-containing feedstock material.

It will be appreciated that the iron-containing feedstock material may be any material, such as an ore, concentrate, scrap, fines, waste materials from steel production value chains or any combination of such materials, which material or combination of materials comprise(s) a metal or metal-containing compound of iron (Fe). 5

The iron-containing feedstock material may be pre-reduced iron feedstock material as well as un-reduced iron feedstock material.

The invention provides for the pre-reduced iron feedstock material to be pre-reduced iron ore. Similarly, the invention provides for the un-reduced iron feedstock material to be un- reduced iron ore.

The pre-reduced iron ore may be either hot briquetted iron (HBI) or cold DRI (CDRI). The

HBI may be crushed HBI (HBI < 20 mm).

The iron-containing feedstock material may include cold briquetted iron waste (CBI < 20 mm).

The iron-containing feedstock material may include waste fines (< 20 mm); mill scale (< 10 mm); pre-reduced iron ore fines (< 10 mm); un-reduced iron ore fines (< 10 mm); and a combination thereof.

In an embodiment of the invention, the pre-reduced iron ore may be carbon deficient or carbon-free HBI or CDRI. It will be appreciated that the pre-reduced iron ore may be low Fe grade HBI or CDRI.

In a further embodiment of the invention, the pre-reduced iron ore can include recycled scrap.

The invention further provides for the iron-containing feedstock material to consist of 100%

-50um iron ore particles.

The invention provides for a plurality of adjustable feeding chutes which allow for the introduction of the combination of hot and cold iron-containing feedstock blend into the electrothermal furnace.

The invention provides for low grade HBI or cold DRI to also be produced with 100% hydrogen to further reduce the CO: footprint. It will be appreciated that the HBI or CDRI produced with 100% hydrogen will have very low to 0% carbon content.

The invention provides for continuous replenishment of the iron-containing feedstock material, reductant and fluxes by means of the plurality of adjustable feeding chutes into the electrothermal furnace to ensure that the loss-in-weight and power-to-feed balance is controlled.

The specific energy requirement (SER) of a smelting process can be simply expressed as

MWh per metric ton of total feed or power (MW)/feed rate (ton/h). SER is the energy required to transform the feed materials at 25 °C into the product streams at the desired temperatures at which they leave the furnace. SER is thus inherently the power-to-feed ratio. It will be appreciated that the theoretical SER changes quite significantly if the chemical composition or temperature of the raw materials deviate from the theoretical baseline.

It is to be understood that an electrothermal furnace is a furnace with a heat source derived from electricity. The electrothermal furnace may be a Direct Current (DC) electric arc furnace, the DC furnace may be used in open bath smelting (open bath furnace (OBF)).

In terms of the present invention, the OBF may be operated on different arc modes, namely immersed arc mode, brush arc mode and open arc mode (multiple or single electrode).

In an embodiment of the invention, there is provided for the DC furnace to include an insulated copper or steel roof.

In terms of the invention, the DC furnace has a power capacity of up to 100 MW with a typical 580 — 640 kWh / ton of hot metal and typical reductant usage of 45 — 50 kg/ton of hot metal (Aim 0.1%C to 4.5 %C).

In an embodiment of the invention, the DC furnace consists of a single electrode.

The DC furnace, as mentioned above, consists of a plurality of adjustable feeding chutes which allows for the introduction of the hot and cold iron-containing feedstock blend in to the

DC furnace. These feeding chutes may comprise a single feeder connected to each feeding cute. The DC furnace may comprise any number of feeding chutes, but particularly the DC furnace comprises 4 or 8 feeding chutes. In another preferred embodiment, the DC furnace may comprise 6 or 12 feeding chutes.

The invention provides for the reductant to be a low grade reductant, for instance anthracite, finer fraction coke, or petroleum coke. In an embodiment of the invention, the reductant may be bio-carbon. The reductant may be added to the electrothermal furnace as particulates having a particle size equal to or less than 0 to 50 mm.

The flux may be selected from the group consisting of burnt dolomite, burnt limestone, quartzite, bauxite and a combination of one or more thereof.

In terms of the invention, the liquid metal product material may be formed through the heating and melting or at least partial melting of the iron-containing feedstock material, reductant and fluxes.

The residence time of the iron-containing feedstock material in the electrothermal furnace may be controlled to impact the degree of reduction of the iron-containing feedstock material inthe electrothermal furnace.

In terms of the invention, the slag product may be used downstream in infer alia cement applications.

The degree of metallization of iron in the iron-containing feedstock material in the process may be from as low as 86% to 94%.

It will be appreciated that carbonization involves taking a low carbon metal product and transforming it into a high carbon metal product. This may be done by exposing the metal product to an atmosphere which is dense in carbon. By heating a metal product in a carbon- dense atmosphere, the metal product will allow carbon atoms to attach to its surface on a molecular level.

In terms of the present invention, carbonization may be achieved by carbon lancing in the

DC furnace into the hot metal. In an alternative embodiment of the invention, carbonization may be achieved in a Torpedo, in hot metal ladles or in a suitable-type vessel.

In an embodiment of the invention, there is provided for carbon lances to be included in the

DC furnace to introduce carbon into the DC furnace to facilitate carbonization of the metal product, if necessary.

The metal product is characterized as per the values provided herein below:

~ Eement | Vae 001-7% 90 - 95% 0.14% sp Too

Tapping Temperature 1450 — 1550 °C

The invention provides for the net carbon footprint to be between 20% and 40% of the traditional BF route.

The present invention provides for a multi-physical computational fluid dynamics model for the reactions, kinetics, and different transformer modes with specific reference to the DC furnace.

It will be appreciated that post tap hole operations can be integrated seamlessly in the process of the present invention.

It is to be understood that the steps of the process according to the invention need not necessarily be executed sequentially, as the process may be operated in a batch, semi-batch or continuous manner. Furthermore, it is envisaged that the steps of the process provided for need not necessarily be executed in the order listed herein.

BRIEF DESCRIPTION OF THE DIAGRAMS

The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein:

Figure 1 is a schematic representation of a process for the smelting of a blend of hot and cold metalliferous-containing feedstock material according to the present invention;

Figure 2 is a cross-sectional front perspective view of adjustable feed chutes as employed in one embodiment of the process of Figure 1;

Figure 3 is a front perspective view of an electrode arm arrangement in a DC furnace as employed in the process of Figure 1;

Figure 4 is a front view of a copper roof design employed in one preferred embodiment of a DC furnace of the process of Figure 1;

Figure 5 is a top perspective view of a six-feed chute arrangement employed in one preferred embodiment of an electrothermal furnace of the process of Figure 1; and

Figure 6 shows a diagram depicting the arc zones within the process of Figure 1.

DETAILED DESCRIPTION OF THE INVENTION

The invention described herein is not to be limited in scope by any specific embodiment or example herein disclosed, as the embodiments and examples are intended as illustrative of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention, as they will become apparent to those skilled in the art from the present description.

A process for the smelting of a hot and cold blend of metalliferous-containing feedstock material according to the invention is generally designated by reference numeral 10 in the accompanying diagrams.

Figure 1 shows a schematic representation of the process 10 for the smelting of a hot and cold blend of metalliferous-containing feedstock material according to the present invention.

As shown in Figure 1; HBI, CDRI, waste and fines 20, reductants and fluxes 30 are fed through adjustable feed chutes 40 (Figure 2) into the DCF 50. Here, hot and cold feed material 20 and reductants and fluxes 30 are (where applicable) batched in separate hoppers and proportioned in the adjustable feed chutes 40 (See Figure 5). The loss-in-weight and feed-to-power ratio systems control the furnace feed 20 and 30 and can be charged in the center (hollow-electrode) of the DCF 50, peripheral of the DCF 50 (side feed) or in the high intensity energy zone (close to the electrode) of the DCF 50.

The high gas velocities around the DCF 50 plasma (not shown) pull the material 20 and 30 in the arc zones (Figure 8) and the DCF 50 is operated with a single or multiple graphite electrode (Figure 3). Furnace operational control is done via a dedicated furnace controller (not shown), a combination of electrode current control, furnace impedance control, furnace resistance control, furnace power input and rectifier control, and very stable furnace operation with the electrode tip (not shown).

The DCF 50 has a power capacity of up to 100 MW with a typical 580 — 640 kWh/ton hot metal and typical reductant usage 45 — 50 kg/ton pig iron (Aim 0.1%C to 4.5 %C).

The furnace 50 itself is constructed from a steel shell with a refractory based containment system that is able to safely contain molten material with temperatures of up to 1 800°C. The furnace 50 includes an insulated copper or steel roof (Figure 4).

Hot iron 60 (see Table 1 below) and molten slag 70 (see Table 2 below) is tapped from the

DCF 50 intermittently and delivered to downstream processes that will produce steel (from hot iron 60) and cement replacement materials (from slag 70).

Table 1: DCF Metal Analysis

Element Vae 0.07 = 5% or

Tapping Temperature 1450-1550 °C

Table 2: DCF Slag Analysis me [0

The hot iron 60 as per plant requirement is tapped from a dedicated set of uniquely placed metal and slag tapholes (not shown). The DCF 50 is equipped with carbon lances 80 strategically placed to optimise carbon feed positions for hot iron carbonization if necessary.

Additional carbonization could also be done by carbon added in the torpedo or ladle.

The net carbon foot print of this production process 10 is expected to be between 20% and 40% of the traditional BF route.

Simultaneously, the process 10 provides an improved alternative to existing technology whereby a hot and cold blend of low grade feed material is used whilst demonstrating a significantly lower carbon footprint with high efficiency yields.

The description is presented by way of example only in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention and/or the equipment utilized therein in more detail than is necessary for a fundamental understanding of the invention.

Claims

Conclusions

1. A process for melting a metalliferous feedstock, the process comprising the steps of: (i) feeding a combination of hot and cold metal-ferrous feedstock, reducing agent and fluxes into an electrothermal furnace through a plurality of adjustable feed hoppers; (ii) heating the hot and cold metal-containing raw material, the reducing agent and the fluxes in the electrothermal furnace at a temperature between 1400°C and 1800°C to sufficiently melt the raw material, the reducing agent and the fluxes to form a liquid metal product, a liquid slag product and a CO-containing gas; (ii) carbonizing the hot and cold metal-containing raw material by introducing a carbon source into the electrothermal furnace; and (iv) providing for the continuous supply of the combination of the hot and cold metal-containing raw material, the reducing agent and the fluxes through the adjustable feeding hoppers to the electrothermal furnace to control the balance between power and supply.

2. The process of claim 1, wherein the metal-ferrous feedstock is an iron-containing feedstock.

3. The process of claim 1, wherein metal-ferrous feedstock is any material, such as ore, concentrate, scrap, fines, waste material from the steel production value chain or any combination of such materials, which material or combination of materials contains a metal or a metal-containing compound of iron (Fe).

4. Process according to any one of claims 1 to 3, wherein the iron-containing feedstock is pre-reduced iron.

5. The process of claim 4, wherein the pre-reduced iron feedstock is pre-reduced iron ore.

6. Process according to any one of claims 1 to 3, wherein the iron-containing feedstock consists of non-reduced iron feedstock.

7. The process of claim 6, wherein the unreduced iron feedstock is unreduced iron ore.

8. The process of claim 5, wherein the pre-reduced iron ore is either hot briquetted iron (HBI) or cold DRI (CDRI).

9. Process according to claim 8, wherein the HBI is crushed HBI (HBI < 20 mm).

10. Process according to any one of claims 1 to 3, wherein the iron-containing raw material comprises cold briquetted iron waste (CBI < 20 mm).

11. Process according to any one of claims 1 to 3, wherein the iron-containing raw material comprises waste fines (< 20 mm), mill scale (< 10 mm), pre-reduced iron fines (< 10 mm), non-reduced iron fines (< 10 mm) and a combination thereof.

12. The process of claim 5, wherein the pre-reduced iron ore is low-carbon or carbon-free HBI or CDRI.

13. The process of claim 5, wherein the pre-reduced iron ore is low Fe grade HBI or CDRI.

14. The process of claim 12 or 13, wherein the pre-reduced iron ore comprises recycled scrap.

15. The process of claim 1, wherein the plurality of adjustable feed hoppers allow the combination of hot and cold ferrous raw material mixture to be introduced into the electrothermal furnace.

16. Process according to any one of the preceding claims, wherein the low-grade HBI or cold DRI is produced with 100% hydrogen to further reduce the CO footprint.

17. The process of claim 1, wherein the process provides for continuous replenishment of the ferrous raw material, the reducing agent and the fluxes through the plurality of adjustable feed hoppers in the electrothermal furnace to ensure control of the weight loss and the balance between power and feed.

18. The process of claim 1, wherein the electrothermal furnace is a DC furnace used in open bath smelting (OBF).

19. The process of claim 1 or claim 18, wherein the OBF operates in different arc modes including submerged arc mode, brush arc mode and open arc mode (multiple or single electrode).

20. The process of claim 1, wherein the DC furnace has a power of up to 100 MW with a typical 580 - 640 kWh/ton hot metal and a typical reducing agent consumption of 45 - 50 kg/ton hot metal.

21. Process according to any one of claims 1, 18, 19 and 20, wherein the DC furnace comprises a single electrode.

22. The process of claim 1, wherein the reducing agent is a low-grade reducing agent, for example anthracite, finer fraction coke or petroleum coke.

23. The process of claim 1, wherein the flux is selected from the group consisting of calcined dolomite, calcined limestone, quartzite, bauxite and a combination of one or more thereof.

24. A process according to any preceding claim, wherein the degree of metallization of iron in the iron-containing raw material in the process may be from 86% to 94%.

25. The process of claim 1, wherein the carbonization is achieved by introducing carbon into the hot metal in the direct current furnace.

26. The process of claim 1, wherein the carbonization is accomplished in a torpedo or pan.

27. Process according to any one of the preceding claims, wherein the net carbon footprint is between 20% and 40% of the traditional BF route.