WO2024115674A1

WO2024115674A1 - Method for preheating metallic charge material and apparatus for preheating metallic charge material

Info

Publication number: WO2024115674A1
Application number: PCT/EP2023/083770
Authority: WO
Inventors: Saikat Chatterjee; Frank Nicolaas Hermanus SCHRAMA
Original assignee: Tata Steel Nederland Technology B.V.
Priority date: 2022-11-30
Filing date: 2023-11-30
Publication date: 2024-06-06

Abstract

This invention relates to a method and an apparatus for producing hot metallic charge material and for subsequent discharging the hot metallic charge material into a converter of a BOS-plant or into a reducing electrical arc furnace (REF) or into a submerged electric arc furnace (SAF), by feeding cold metallic charge material through a heating device.

Description

METHOD FOR PREHEATING METALLIC CHARGE MATERIAL AND APPARATUS FOR PREHEATING METALLIC CHARGE MATERIAL

Field of the invention

The present invention relates to a method and an apparatus for preheating metallic charge material for discharging into a converter of a BOS-plant for the production of molten metal.

Background of the invention

Basic oxygen steelmaking (BOS) is a primary steelmaking process for converting molten pig iron into steel by blowing oxygen through a lance over the molten pig iron inside a basic oxygen furnace (BOF). The BOF is a refractory-lined, tiltable converter into which a vertically movable, water-cooled lance is inserted to blow oxygen through nozzles at supersonic velocity onto the charge. Exothermic heat is generated by the oxidation reactions during blowing. This process has been in use since the 1950's and is well known to the skilled person. A normal steelmaking practice in a basic oxygen furnace involves charging the converter vessel with 30% of a metal charge (usually scrap) and about 70% melted pig iron, and other required ingredients such as lime, limestone and the like. The relatively cold scrap cools the pig iron to an average temperature and therefore when the oxygen lance is lowered into the vessel and the oxygen ignited, the heat needed to melt the scrap comes from the heat of combustion of the silicon, carbon and manganese in the pig iron, and possibly from the combustion of some iron from the pig iron. Thus, considerable time and oxygen are required to bring up the heat to desired temperature and some of the pig iron may be consumed in this process. Consequently the implementation of solid scrap preheating in the metal industry has been a subject of interest due to the economic and energy saving benefits.

US 3479178 discloses a method wherein ferromagnetic steel scrap is preheated by radiant heating devices to an elevated temperature within an enclosure prior to charging the steel scrap into an adjacent basic oxygen furnace. The method comprises reheating the scrap to a temperature of at most just below the Curie temperature to avoid losing its ferromagnetic properties, and magnetically lifting and transferring the preheated scrap into the furnace. US 3479178 employs a preheat furnace which is a tunnel-type furnace wherein a car or cars carrying scrap passes through the furnace and is being reheated during its progress through the furnace.

The disadvantage of this method is that the heating is quite inefficient due to the need to heat the furnace and the cars and the ferromagnetic steel scrap and also that it is a discontinuous process involving magnetic lifting and transferring the preheated scrap.

EP0747492-A1 discloses a method to improve the efficiency of an electric arc (EAF) melting furnace by introducing and burning complementary energy releasing material, such as tire rubber, which is intimately mixed with the ferrous material before being fed into the EAF.

EP0592723 discloses a method for the preheating of charge materials using the offgases of an EAF and using any chemical heat in the off-gases provided sufficient oxygen is injected into the furnace to create CO in the off-gases. Carbon is injected into the slag or slag-metal interface as powdered carbon or coke through underbath tuyeres to form a foaming slag and results in the formation of CO in the off-gases.

Objectives of the invention

It is an object of the invention to provide a method for preheating metallic charge material to be fed into a converter of a BOS-plant for the production of molten metal that is more energy efficient.

It is also an object of the invention to provide such a method that allows preheating the metallic charge material to a temperature above the Curie temperature.

It is also an object of the invention to provide such a method that allows preheating the metallic charge material to a temperature up to its oxidation limits.

Description of the invention

One or more of the objects is reached with a process for producing a hot metallic charge material and for subsequent discharging the hot metallic charge material into a converter of a BOS-plant (1) or into a reducing electrical arc furnace (REF) or into a submerged electric arc furnace (SAF), by feeding cold metallic charge material through a heating device (3) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein said metallic charge material is preheated in a continuous process by 1. the sensible heat present in one or more of i. hot BOF off-gas (7, BOFG) exiting the converter (1) and entering the heating device gas entry point (5a) and/or ii. hot arc furnace off-gas (AFG) exiting the REF or SAF and entering the heating device gas entry point (5a) wherein the hot off-gas moves in the opposite direction to the direction of movement of the metallic charge material through the heating device (countercurrent), and/or 2. by the chemical heat generated by post-combustion in burner means in a burner section (8) of the heating device of the combustible gases in the BOFG (9) or of the combustible gases in the AFG, wherein the off-gases are optionally supplemented by a secondary fuel (10), thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter through a charging opening in the converter or the REF or SAF. The process as described above could also be implemented in concurrent flow instead of countercurrent flow of metallic charge material and BOFG or AFG, but this is less efficient.

In the context of this invention two types of arc furnaces are considered: Reducing Electric Furnace (REF) and Submerged Arc Furnace (SAF). These are jointly referred to herein by the abbreviation AF. In the context of this invention combustible gases present in the BOFG exiting the converter and/or of the combustible gases present in the AFG exiting the AF means either i). only BOFG or ii). only AFG or iii). a mixture of BOFG and AFG.

In steelmaking many of the processes generate large quantities of off-gas. Examples of these off-gases are the Coke Oven Gas (COG), Blast Furnace Gas (BFG), Basic Oxygen Furnace Gas (BOFG), Reducing Electric Furnace Gas (REFG) and Submerged Arc Furnace Gas (SAFG). A reducing electric arc furnace (REF) can be used to process direct reduced iron (DRI) and/or scrap into hot metal by using electrical energy under a reducing atmosphere to reduce the oxygen content in the DRI. Both the REF and the submerged arc furnace (SAF) work under reducing conditions contrary to the conventional Electric Arc Furnaces (EAF) which work under oxidising conditions. These off-gases (COG, BFG, BOFG, REFG en SAFG) exit the furnaces at high temperatures and they therefore carry a significant amount of energy (sensible and chemical heat) that is to be considered as losses if not properly re-used. Conventional EAF's are used to melt scrap, and the offgases do not contain combustible gases. One of the ways to use the sensible energy contained in these gases, and of BOFG and REFG in particular, is to use the sensible heat to preheat scrap metal before introducing it into a converter or an AF.

Typically the BOF off-gas (BOFG) has the following typical characteristics:

Sensible Heat Available TBOFG ~ 1400 - 1600°C

Flow rate ~ 50-100 Nm3/tLS (tonne of Liquid Steel)

- Consists of energy-rich component like CO (60-80% CO) High calorific value: 1600-2000 kcal/Nm³ (6.7-8.5 MJ/Nm³)

The benefit is to reduce the time and energy needed to melt the scrap and thereby increase the overall energy efficiency. As the heat is coming from hot off-gases, the energy saving benefit is high. Another point of interest is that moisture has to be removed from the metal scrap before it is loaded into the melting furnace to avoid severe explosions known as molten metal splash. By pre-heating the scrap any moisture is removed and as a result of the heat in the heating device. According to the invention any VOC and low melting metals (such as zinc) that may still be present on the scrap is vaporised and as a result the scrap is cleaned before it is charged into the relevant steelmaking device. The limitation of the risk of molten metal splash is a big safety bonus of the method according to the invention. In addition the BOFG and REFG also contains large amounts of chemical energy in the form of combustible compounds like CO.

The invention preheats metallic charge material, such as metallic scrap or scrap, thus allowing higher metallic charge inputs in iron and steelmaking processes because of the reduced cooling effect of the hot charge and it reduces the energy consumption to maintain the temperature of the processes. Apart from scrap, other potential metallic charge material could be DRI pellets, HBI, iron ore or solid pig iron.

After having been used to heat the metallic charge material the meanwhile cooled BOFG or REFG is temporarily stored in a gas holder for later use. Alternatively the cooled BOFG or REFG can be immediately directed to the burners for further heating the preheated metallic charge material.

Contrary to the off-gases of a conventional EAF the REFG and SAFG contains combustible gases because the REF and SAF operate under a reducing atmosphere because they need to be able to reduce DRI pellets, HBI, iron ore and the like to iron and melt it, whereas a conventional EAF is not able to reduce DRI pellets, HBI, iron ore but is only able to melt scrap.

In an embodiment a process is provided for producing a hot metallic charge material and for subsequent discharging the hot metallic charge material into a converter of a BOS- plant (1) by feeding cold metallic charge material through a heating device (3) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein said metallic charge material is preheated in a continuous process by 1. the sensible heat present in one or more of i. hot BOF off-gas (7, BOFG) exiting the converter (1) and entering the heating device gas entry point (5a) and/or ii. hot arc furnace off-gas (AFG) exiting a REF or SAF and entering the heating device gas entry point (5a) wherein the hot off-gas moves in the opposite direction to the direction of movement of the metallic charge material through the heating device, and/or 2. by the chemical heat generated by post-combustion in burner means in a burner section (8) of the heating device of the combustible gases in the BOFG (9) or of the combustible gases in the AFG, wherein the off-gases are optionally supplemented by a secondary fuel (10), thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter through a charging opening in the converter.

In an embodiment a process is provided for producing a hot metallic charge material and for subsequent discharging the hot metallic charge material into a reducing electrical arc furnace (REF) or into a submerged electric arc furnace (SAF), by feeding cold metallic charge material through a heating device (3) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein said metallic charge material is preheated in a continuous process by 1. the sensible heat present in one or more of i. hot BOF off-gas (7, BOFG) exiting the converter (1) and entering the heating device gas entry point (5a) and/or ii. hot arc furnace off-gas (AFG) exiting the REF or SAF and entering the heating device gas entry point (5a) wherein the hot off-gas moves in the opposite direction to the direction of movement of the metallic charge material through the heating device, and/or 2. by the chemical heat generated by post-combustion in burner means in a burner section (8) of the heating device of the combustible gases in the BOFG (9) or of the combustible gases in the AFG, wherein the off-gases are optionally supplemented by a secondary fuel (10), thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter through a charging opening in the REF or SAF.

In an embodiment the heating device comprises at least a first heating zone (11) and a second heating zone (12) wherein the cold metallic charge material entering the first heating zone is heated by the sensible heat in the BOFG or AFG, and wherein the preheated metallic charge material is subsequently passed to the second heating zone wherein the preheated metallic charge material is further heated by the heat generated by post-combustion of the combustible gases in BOFG or AFG optionally supplemented by the combustible secondary fuel (10) in the burner means in the burner section of the heating device.

In this embodiment optimal use is made from the sensible heat in the BOFG or AFG and from the chemical heat in the cooled BOFG or AFG. Any excess BOFG or AFG can be stored for later use, or used for alternative purposes like the generation of electricity.

Post-combustion of the BOFG and AFG using oxygen (oxy-fuel combustion) leads to generation of gas streams that comprise primarily of CO2. In an embodiment CO2 (16) is captured from the flue gas exiting the heating device and sent to a CO2 processing facility for cleaning, storage or for further utilization.

The invention as claimed also allows an efficient utilization of iron and steelmaking off-gases and consequently also reduce the total CO2 footprint of total process chain. By reusing the off-gases in the same process chain the invention facilitates circularity in iron and steelmaking. The full beneficiation of the carbon in the process also enables efficient CO2 capture for utilization and/or storage because the CO2 concentration in the flue gas exiting the heating device is very high. The CO2 emissions can be effectively captured from one single location and source using known CO2 capture technologies. Capturing CO2 from one consolidated gas stream having a high volume and concentration of CO2 is both efficient and cost-effective. The captured CO2 can be utilized to produce fuels, building materials, be used in greenhouses or permanently stored under the ground. For some applications the CO2 may need to be clean to remove traces of e.g. sulphur compounds or nitrogen compounds. The quality of the captured CO2 stream is enhanced if the heating device is equipped with an air-tight set-up and controlled oxyfuel combustion. An air-tight setup for the controlled combustion of the CO-rich off-gases is also important to prevent CO leaks and to maintain a reducing atmosphere to prevent oxidation of the metallic charge material. The presence of very high fraction of CO gas in the BOFG and AFG generates a reducing atmosphere - which is likely to shift the oxidation boundaries of Fe/FeO, thereby preventing FeO formation even at a higher temperature.

In an embodiment the heating device is provided with dust and fume capturing means and VOC-capturing means for preventing release of dust and VOC and wherein the dust and fume capturing means and the VOC-capturing means are adapted to process the dust, fumes and/or VOC to minimize the environmental impact of the process and maximise the re-use of the resources present in the dust, fumes and VOC. Any SOx and NOx traces are removed by known systems.

The heating device may be equipped with a separate unit for combustion of VOC that may develop during the heating of the metallic charge material. Also any dust developed during the heating of the metallic charge material is collected, e.g. by employing a negative pressure technology which allows better control over flame direction and penetration into the scrap pieces.

In an embodiment temperature measurement means, Tl, are provided between the first and the second heating zone and wherein the temperature reading is used as a 'feedforward' input parameter for controlling the burner settings of the second heating zone. A burner/fuel mix controller assists in choosing the correct burner settings and the right fuel mix.

In an embodiment wherein temperature measurement means, T2, are provided between the second heating zone and the discharge of the metallic charge material into the converter and wherein the temperature reading is used as a 'feedback' input parameter for controlling the burner settings of the second heating zone. Additional sensors at suitable locations may further increase the accuracy and economy of the heating process.

Various sensors like temperature sensors (e.g. Tl and T2) and gas mixture sensors (flow rate, composition and gas temperature) provide the controller with the necessary input. The controller may also take action if there is no BOFG or AFG flow (due to intermittency) and increase the pre-heating in the second heating zone to make up for no heating in the first preheating zone. On the basis of gas flows and temperature feedback the controller may instruct burners to generate the required amount of heat by determining the right fuel mix wherein secondary fuels need to be used if the BOFG flow or AFG flow is not sufficient. The controller may also vary in the distribution of the burner scheme for even heating of the metallic charge material.

In an embodiment the converter is charged with hot metallic charge material and a charge of molten metal chosen from the group of molten metals consisting of molten iron produced in a blast furnace, molten iron produced in an arc furnace (REF I SAF), molten iron produced in a HIsarna®-facility or molten metal produced in an induction furnace.

As secondary fuel the following alternatives can be considered: hydrogen, natural gas, propane, syngas, cold BOFG or AFG, purified blast furnace off-gas, purified coke oven gas. The hydrogen may be "green" (from electrolysis based on green electricity), "blue" (from steam methane reforming integrated with carbon capture for lower CO2 footprint) or "grey" (e.g. from steam methane reforming without carbon capture). Syngas may be provided by gasification of coal I coke I municipal waste, integrated with or without carbon capture. The secondary fuel may also be created from CO2, for instance by a catalytic hydrogenation of CO2 according to: CO2 + 3H2 = CH3OH + H2O, wherein the hydrogen is preferably green hydrogen or other sources.

The first preheating zone (5) operates in a counter-current flow mechanism where the hottest BOFG or AFG contact the hottest metallic charge material and the cooled BOFG or AFG contact the colder metallic charge material. The first heating zone may preferably be provided with a temperature resistant conveyor belt for conveying the metallic charge material while being preheated or with a rotating drum or rotating tube to increase the residence time and to increase the heat transfer. The conveyor belt may be only moving forward, but it may also be provided with vibration means to increase the heating homogeneity. The second heating zone is provided with one or more burners in a burner section, preferably with oxyfuel burners, enabling a controlled heating to reach the target discharge temperatures of the metallic charge material whilst fully utilising the calorific value of BOFG - or AFG gases. Preferably the burners are of the direct flame impingement (DFI) type.

In an embodiment the cold metallic charge material is heated in the heating device by the sensible heat present in BOF off-gas (BOFG) exiting the converter and entering the heating device gas entry point and by the heat generated by post-combustion of the cooled BOFG, optionally supplemented by a secondary fuel, such as natural gas, hydrogen or hot BOFG or hot or cold AFG.

There are three main options for charging the hot metallic charge material into the converter

Option a: through the (optionally modified) openings for flux/ore additions;

Option b: charging from the top;

Option c: conventional bucket charging;

The charging may be continuous or semicontinuous to increase productivity and to have a balanced (steady or semi-steady state) operation. However, due to the batch type converter process the charging of the converter is likely to be semicontinuous or batchwise. An AF may be charged in a continuous way or semicontinuous, although also here a batchwise charging is possible. A continuous way results in the lowest loss of heat of the charge as the hot metallic charge material is immediately processed without any delay.

In an embodiment of the invention the temperature of the hot metallic charge material exiting the heating device is controlled by one or more temperature measuring means and by adjusting 1. the flow of hot BOFG or 2. the flow of hot AFG or 3. the flow of hot BOFG and hot AFG or 4. adjusting the burners in the burner section, optionally by adding a secondary fuel to the cooled BOFG or to the cooled AFG to top up the caloric value of the gas supplied to the burners in the burner section.

In an embodiment cold metallic charge material is continuously provided to the heating device and/or wherein hot metallic charge material is continuously discharged from the heating device.

In a preferred embodiment of the invention the process relates to producing the hot metallic charge material and for subsequent discharging the hot metallic charge material into a converter by feeding the cold metallic charge material through the heating device wherein the metallic charge material is preheated in a continuous process by the sensible heat present in BOFG and by the chemical heat generated by post-combustion in burner means in the burner section (8) of the heating device of the combustible gases in the BOFG wherein the BOFG is optionally supplemented by a secondary fuel, thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter. This embodiment is particularly relevant for steel production sites that do not have access to AFG, for instance because the production facilities on the site do not include SAF's or REF's.

In a preferred embodiment of the invention scrap is added to the converter in an amount of at least 25% of the total metallic input to the BOF, the remainder being hot metal (molten iron from other sources), preferably at least 26%, or even 27 %.

According to a second aspect the invention is also embodied in an apparatus for preheating metallic charge material for use in the production of steel in a basic oxygen furnace (1) or a reducing or submerged arc furnace comprising a heating device (3) comprising a first heating zone (11) and a second heating zone (12) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein, in use, in the first heating zone said metallic charge material is heatable by 1. the sensible heat present in BOF off-gas (7) (BOFG) exiting the BOF and entering the hot gas entry point (5a) of the first heating zone (11) of the heating device or 2. the sensible heat present in AF off-gas (AFG) exiting the AF and entering the gas entry point (5a) of the first heating zone (11) of the heating device or 3. in the second heating zone (12) by the heat generated by postcombustion in a burner section (8) of the combustible gases present in the BOFG and/or of the combustible gases present in the AFG. A burner/fuel mix controller (15) assists in choosing the correct burner settings and the right fuel mix.

In an embodiment the heating device (3) is provided as a tunnel furnace provided with scrap conveyor means (4) to convey the metallic charge material through the heating device or wherein the heating device is provided as a shaft furnace wherein gravity is the conveyor means to convey the metallic charge material through the heating device.

In an embodiment the heating device is provided with one or more of: means to prevent sticking together of the hot metallic charge material; means to collect hot metallic charge material and discharge the collected hot metallic charge material into the converter or AF; conveying means to semi-continuously feed hot metallic charge material to the converter or AF.

Examples

The apparatus for producing heated metal scrap for charging into a converter according to the invention and the process by means of figure 1 and 2. In a typical the plant complex for steel production according to the invention a liquid iron charge is provided to a converter (basic oxygen furnace, BOF). In the converter iron is converted into crude steel by blowing oxygen onto the liquid iron and troublesome impurities, in particular carbon, silicon and phosphorus, are removed. Scrap may be added in amounts of up to 25-30% with respect to the amount of iron. Furthermore lime is added for forming slag and alloying agents. At the top of the converter, very hot converter gas (basic oxygen furnace gas, BOFG) that has a very high proportion of CO is drawn off. Typical temperatures of the BOFG are 1400 to 1600°C. This gas is led through the first heating zone of the heating device though which selected metallic charge material is conveyed in the opposite direction to benefit maximally from the exchange of heat between BOFG and scrap. The conveying means belt preferably allow a good contact between gas and scrap. This may be achieved by agitating the scrap whilst conveying it. The BOFG exits the heating device cooler and is temporarily stored in a gas holder. Preferably as much of the sensible heat is extracted from the off-gases. The temperature of the off-gas is preferably below 100°C, more preferably below 75 °C and even more preferably below 50 °C. Mutatis mutandis this is also applicable in case the off-gas is AFG. The preheated scrap meanwhile exits the first heating zone and enters the second heating zone. The temperature T1 is measured and fed into the second heating zone, where the burner/fuel mix controller instructs mixing of appropriate fuels to allow the scrap to be preheated and leave the second heating zone with the target temperature T2 of about 780 to 800°C. The preheated scrap is then charged to a BOF that is ready to receive it in preparation of receipt of liquid iron and the additives after which it can start the blowing process to produce steel. Most steel plants have several BOF's, e.g. 3, so that BOFG from one BOF can be used to preheat metallic charge material for another BOF, etc..

Brief description of the drawings

The invention will now be explained by means of the following, non-limiting figures.

Figure 1 shows a schematic drawing of a heating device in symbiosis with a BOF converter 1. The BOFG comprising CO and CO2 is captured by means of a hood over the converter. This is already known because this is already used for capturing the off-gases and using them as fuel for the various processes in steelworks. However, for this known application the off-gases need to be cooled from around 1600°C to about 75°C for safe storage in a gasholder for later use. In the invention the hot BOF off-gases (BOFG) are captured and conveyed to an inlet 5a of a heating device 3 through a duct 7. The heating device is fed with suitably pre-processed metallic charge material 2 and is conveyed into the heating device 3, and in particular into the first heating zone 11 by conveying means 4. It is optimal to have opposite directions of BOFG flow and metallic charge material flow (counter-current) to maximise the heat transfer between gas and metallic charge material. The cooled BOFG exits the heating device and is led to a storage facility 14. The heated metallic charge material continues through the heating device and enters a burner section 8 in the second heating zone. The burners are fed with the cooled BOFG and/or AFG 9 from the storage facility 14 and burned with air or preferably with oxygen 13 (in so-called oxyfuel burners) coming from storage 10. Secondary fuel from storage 14 may be used to top up the caloric value of the cooled BOFG stored in 14. A burner/fuel mix controller (15) assists in choosing the correct burner settings and the right fuel mix. The off-gas from the burner section is led to carbon capturing means 16 and stored or utilised 17. Temperature measurements T1 and T2 assist the burner/fuel mix controller (15) in choosing the settings and fuel mix. The hot metallic charge material is discharged from the heating device at the heating device discharging point 6 and discharged into the converter through the (optionally modified) openings for flux/ore additions (a), charging from the top (b) or conventional bucket charging (c). The heating of the metallic charge material can be performed continuously. The charging of a converter is not continuous because during the oxygen blowing period no scrap is added. In a multi-converter works the charging can be directed to another converter, or the hot scrap can be collected and discharged into a converter as soon as a converter is ready for receiving the hot metallic charge material. To make optimal economical and safe use of the invention it is preferable that the capture of the off-gas, its use in the first heating zone, its storage in the storage facility (14), its subsequent use in the second heating zone and the further processing of its off gasses is performed in a gas-tight way. Otherwise loss of BOFG, loss of sensible heat, loss of chemical heat and uncontrolled release of dust, VOC and gases like CO and CO2 may occur. It is noted that figure 1 gives a schematic configuration and is not intended to be limiting. The ingress of air can be prevented by carrying out operations under overpressure, as shown in figure 2.

Figure 3 shows a block diagram of the gas and scrap streams in the process and apparatus according to the invention. Two alternative sources of off-gas are depicted (BOF, AF). One of these sources may be used, or alternatively or simultaneously, depending on the lay-out and energy balance of the site, where the apparatus is located. The apparatus is contained in an airtight enclosure where the sensible heat is used to heat the metallic charge material (indicated here with the dashed arrow, gas streams are solid arrows) and where the chemical heat is released form the off-gas by burning the combustible compounds in the cooled off-gas. Hot metallic charge material is subsequently discharged and charged into the BOF (or AF (not depicted)).

Claims

CLAIMS A process for producing hot metallic charge material and for subsequent discharging the hot metallic charge material into a converter of a BOS-plant (1) or into a reducing electrical arc furnace (REF) or into a submerged electric arc furnace (SAF), by feeding cold metallic charge material through a heating device

(3) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein said metallic charge material is preheated in a continuous process by 1. the sensible heat present in one or more of i. hot BOF off-gas (7, BOFG) exiting the converter (1) and entering the heating device gas entry point (5a) and/or ii. hot arc furnace off-gas (AFG) exiting the REF or SAF and entering the heating device gas entry point (5a) wherein the hot off-gas moves in the opposite direction to the direction of movement of the metallic charge material through the heating device, and/or 2. by the chemical heat generated by post-combustion in burner means in a burner section (8) of the heating device of the combustible gases in the BOFG (9) or of the combustible gases in the AFG, wherein the off-gases are optionally supplemented by a secondary fuel (10), thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter through a charging opening in the converter or the REF or SAF. Process according to claim 1 wherein the heating device comprises at least a first heating zone (11) and a second heating zone (12) wherein the cold metallic charge material entering the first heating zone is heated by the sensible heat in the BOFG or AFG, and wherein the preheated metallic charge material is subsequently passed to the second heating zone wherein the preheated metallic charge material is further heated by the heat generated by post-combustion of the combustible gases in BOFG or AFG optionally supplemented by the secondary fuel (10) in the burner means in the burner section of the heating device. Process according to claim 1 or 2 wherein the heating device is provided with dust and fume capturing means and VOC-capturing means for preventing release of dust and VOC and wherein the dust and fume capturing means and the VOC-capturing means are adapted to process the dust, fumes and/or VOC to minimize the environmental impact of the process and maximise the re-use of the resources present in the dust, fumes and VOC.

4. Process according to any one of claims 1 to 3 wherein CO2 (16) is captured from the flue gas exiting the heating device and sent to a CO2 processing facility for cleaning, storage or for further utilization.

5. Process according to any one of claims 1 to 4 wherein the combustible gases in the cooled BOFG or AFG are supplemented by one or more secondary fuels.

6. Process according to any one of claims 1 to 5 wherein temperature measurement means, Tl, are provided between the first and the second heating zone and wherein the temperature reading is used as 'feed-forward' input parameter for controlling the burner settings of the second heating zone.

7. Process according to any one of claims 1 to 6 wherein temperature measurement means, T2, are provided between the second heating zone and the discharge of the metallic charge material into the converter and wherein the temperature reading is used as 'feed-back' input parameter for controlling the burner settings of the second heating zone.

8. Process according to any one of the claims 1 to 7 wherein the converter is charged with hot metallic charge material and molten metal chosen from the group of molten metals consisting of: molten iron produced in a blast furnace, molten iron produced in an arc furnace, molten iron produced in a HIsarna®-facility, molten metal produced in an induction furnace.

9. Process according to any one of the claims 1 to 8 wherein the cold metallic charge material is heated in the heating device by the sensible heat present in BOF off-gas (BOFG) exiting the converter and entering the heating device gas entry point and by the heat generated by post-combustion of the cooled BOFG, optionally supplemented by a secondary fuel, such as natural gas, hydrogen or hot BOFG or hot or cold AFG.

10. Process according to any one of the claims 1 to 9 wherein the temperature of the hot metallic charge material exiting the heating device is controlled by one or more temperature measuring means and by adjusting 1. the flow of hot BOFG or 2. the flow of hot AFG or 3. the flow of hot BOFG and hot AFG or 4. adjusting the burners in the burner section, optionally by adding a secondary fuel to the cooled BOFG or to the cooled AFG to top up the caloric value of the gas supplied to the burners in the burner section. Process according to any one of the claims 1 to 10 wherein cold metallic charge material is continuously provided to the heating device and/or wherein hot metallic charge material is continuously discharged from the heating device. Process according to any one of claims 1 to 11 for producing the hot metallic charge material and for subsequent discharging the hot metallic charge material into the converter of a basic oxygen furnace by feeding the cold metallic charge material through the heating device wherein the metallic charge material is preheated in a continuous process by the sensible heat present in BOFG and by the chemical heat generated by post-combustion in burner means in the burner section (8) of the heating device of the combustible gases in the BOFG wherein the BOFG is optionally supplemented by a secondary fuel, thereby heating the metallic charge material and discharging the hot metallic charge material from the heating device exit point into the converter. Apparatus for producing hot metallic charge material for use in the production of steel in a basic oxygen furnace (1) or an reducing electric or submerged arc furnace comprising a heating device (3) comprising a first heating zone (11) and a second heating zone (12) provided with conveyor means (4) for conveying the metallic charge material from a heating device charging point (5) to a heating device discharging point (6) wherein, in use, in the first heating zone said metallic charge material scrap is heatable by 1. the sensible heat present in BOF off-gas (7) (BOFG) exiting the BOF and entering the hot gas entry point (5a) of the first heating zone (11) of the heating device or 2. the sensible heat present in AF off-gas (AFG) exiting the AF and entering the gas entry point (5a) of the first heating zone (11) of the heating device or 3. in the second heating zone (12) by the heat generated by postcombustion in a burner section (8) of the combustible gases present in the BOFG and/or of the combustible gases present in the AFG. Apparatus according to claim 13 wherein the heating device (3) is provided as a tunnel furnace provided with scrap conveyor means (4) to convey the metallic charge material through the heating device or wherein the heating device is provided as a shaft furnace wherein gravity is the conveyor means to convey the metallic charge material through the heating device. Apparatus according to claim 13 or 14 wherein the heating device is provided with one or more of: means to prevent sticking together of the hot metallic charge material; means to collect hot metallic charge material and discharge the collected hot metallic charge material into the converter or AF; conveying means to semi-continuously feed hot metallic charge material to the converter or AF.