How to heat metal products

Abstract

The present invention relates to a method for heating a semi-finished steel product, comprising the steps of: - a preheating step carried out in a preheating device comprising a chamber for containing solid particles, a heat exchanger, a support capable of supporting said semi-finished steel product, and a gas injector; and - Heating process carried out in a furnace Including, The preheating step includes the following steps: i. injecting a gas into the first chamber to form a first fluidized bed; ii. heating the fluidized bed with the heat exchanger; iii. placing said semi-finished steel product in said fluidized bed and on said support such that said fluidized bed can transfer heat to said semi-finished steel product; iv. Removing the semi-finished steel product when its temperature is between 200°C and 1000°C. Including, The heating step relates to a method comprising heating the semi-finished steel product to a temperature of 1100-1400°C.

Description

[Technical field]

[0001] The present invention relates to a method for heating a semi-finished steel product. [Background technology]

[0002] In steel production, and more generally in metal production, steel products need to be reheated before undergoing a forming process or a heat treatment. This is the case for example for billets or blooms before hot rolling, which are usually reheated in a furnace from room temperature to temperatures above 1000°C. Summary of the Invention [Problem to be solved by the invention]

[0003] However, such reheating consumes a lot of energy, which leads to the emission of greenhouse gases. It is therefore desirable to develop a method for heating semi-finished products that reduces the impact of the process on the environment.

[0004] It is an object of the present invention to provide such a heating method. [Means for solving the problem]

[0005] This is achieved by providing a method according to any one of claims 1-10.

[0006] Other features and advantages will become apparent from the following description of the invention.

[0007] The present invention relates to a method for heating a semi-finished steel product 2, which is a slab, billet or bloom, comprising the steps of: a preheating step carried out in a preheating device comprising a chamber 3 containing solid particles 4, a heat exchanger 5, a support 6 capable of supporting said semi-finished steel product, a gas injector 7, and - a heating step carried out in a furnace, in which the semi-finished steel product is heated to a temperature of 1000-1400°C; - a hot rolling step after said heating step, in which said semi-finished steel product is hot rolled. Including, The preheating step includes the following steps: i. injecting a gas 12 into said first chamber 3 to form a first fluidized bed 8; ii. heating the fluidized bed 8 by means of the heat exchanger 5; iii. placing said semi-finished steel product 2 in the fluidized bed 8 so that said semi-finished steel product 2 is supported by said support 6 and said fluidized bed 8 is capable of transferring heat to said semi-finished steel product 2; iv. A step of removing the semi-finished steel product 2 when its temperature is 200°C to 1000°C. Including, The heating step relates to a method comprising heating the semi-finished steel product to a temperature of 1100-1400°C. [Brief description of the drawings]

[0008] [Figure 1] 1 illustrates an embodiment of a device capable of implementing the claimed methods. [Diagram 2] 1 shows an embodiment of a multiple pre-heating device, where pre-heating is performed by at least two pre-heating devices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferably, said semi-finished steel products, being slabs or billets or blooms, are laminated.

[0010] The device comprises a chamber 3 containing solid particles 4, a heat exchanger 5, a support capable of supporting a semi-finished steel product 6, and a gas injector 7. The chamber is preferentially capable of receiving a plurality of semi-finished steel products. The support 6 is preferentially capable of receiving a plurality of semi-finished steel products. The support may be a mesh basket. Preferably, in step iii., the semi-finished steel product is on said support.

[0011] The semi-finished steel products may be transported in and out of the chamber by a rolling conveyor or may be placed in the chamber by a pick-up means, e.g. a crane or any suitable pick-up means. For example the system disclosed in WO2021064451 can be used as pick-up means. Even more preferably, said supports are not used to move said semi-finished products in and out of chamber 3. By separating the support system and the transport system, e.g. the pick-up means, the number of transport systems can be reduced in case several semi-finished steel products are pre-heated simultaneously.

[0012] The chamber may be a closed chamber with a closable opening through which the semi-finished steel products can be transported, but it may also have an open roof or any configuration suitable for the transport of semi-finished steel products.

[0013] In step i. of the pre-heating step, gas is injected into said chamber 3 to form a fluidized bed 8. This injection is performed by a gas injector 7.

[0014] Preferably, the gas injected into the chamber is heated. Even more preferably, the gas has a temperature between 200 and 1000°C. This allows to reduce the energy required to heat the fluidized bed in the preferred temperature range. Even more preferably, the gas is at least partially heated by renewable energy sources and / or recovered waste heat. Recovered waste heat can come, for example, from recycled fumes.

[0015] Even more preferably, the gas injected into the chamber is heated by heating means powered partly or entirely by CO2 neutral electricity.

[0016] CO2 neutral electricity includes electricity from renewable sources, which is defined as energy collected from renewable resources that are naturally replenished on human timescales, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat, among others. In some embodiments, the use of electricity derived from nuclear sources can be used, as it does not release the CO2 that is produced.

[0017] Preferably, the solid particles in the fluidized bed are in a bubbling regime. The gas velocity applied to obtain a bubbling regime depends on several parameters, such as the type of gas used, the size and density of the particles, or the size of the chamber, which are easily controlled by the skilled person.

[0018] In step ii., the fluidized bed is heated by a heat exchanger. The heat exchanger 5 is capable of transferring heat to said fluidized bed 8. An inlet pipe 9 is connected to said heat exchanger such that a transport medium can be introduced into the heat exchanger by said inlet pipe 9. An outlet pipe 11 is connected to said heat exchanger such that a transport medium can be discharged from the heat exchanger by said outlet pipe 11. The walls of the chamber 3 are capable of housing the heat exchanger.

[0019] Preferably, in step ii., the fluidized bed is heated to a temperature of 400-700°C, preferably 500-700°C, even more preferably 600-700°C.

[0020] Preferably, the transfer medium circulates within said heat exchanger and is introduced into said heat exchanger at a temperature between 250°C and 1500°C.

[0021] Preferably, the transport medium is at least partially heated by a renewable energy source.

[0022] Preferably, the transfer medium circulates through said heat exchanger and leaves said heat exchanger at a temperature between 150°C and 1000°C.

[0023] Even more preferably, the gas is at least partially heated by a renewable energy source and / or recovered waste heat, which may for example come from recycled fumes.

[0024] Step ii. occurs simultaneously with step i., such that the solid particles are heated while they form a fluidized bed.

[0025] In step iii., the semi-finished steel product is placed inside the fluidized bed so that it can be heated by the fluidized bed. Thus, steps i. and ii. are carried out during step iii. to allow heat transfer from the heat exchanger to the fluidized bed and from the heat exchanger to the semi-finished steel product.

[0026] Preferably, said semi-finished steel product is brought to ambient temperature before being conveyed to the fluidized bed.

[0027] Preferably, the entire semi-finished steel product is inside said fluidized bed.

[0028] In step iv., the semi-finished steel product is removed from the fluidized bed when it has reached a predetermined temperature.

[0029] Preferably, the semi-finished steel product is removed when its temperature is between 500° C. and 700° C. Even more preferably, the semi-finished steel product is removed when its temperature is between 600° C. and 700° C.

[0030] In the heating process, the semi-finished steel product is heated in a furnace to a temperature of 1100°C to 1400°C. This heating range allows hot rolling to be performed.

[0031] Preferably, the method comprises a hot rolling step after the heating step, and said semi-finished steel product is hot rolled.

[0032] Preferred Embodiments Preferably, the gas injected into the chamber is air. Alternatively, the gas injected by the gas injector is preferably an inert gas such as argon or helium, or nitrogen or a mixture of gases.

[0033] Preferably, the gas injected into the chamber is at a temperature close to or higher than that of one of the fluidized beds.

[0034] Preferably, the gas has a flow rate of 1 to 30 cm.s -1 Such a rate range requires low ventilation power and therefore reduced energy consumption.

[0035] Preferably, the solid particles have a size of 40 to 500 μm.

[0036] Preferably, the solid particles have a powder density of 500 to 2000 J.kg -1 .K -1 The heat capacity is contained in

[0037] Preferably, the bulk density of the solid particles is between 1400 and 4000 kg.m -3 It is.

[0038] Preferably, the solid particles are ceramic particles. Preferably, the solid particles are made of glass or any other solid material that is chemically stable up to 1000° C. For example, the solid particles can be made of SiC, olivine, steel slag or alumina.

[0039] Preferably, the solid particles are inert, which avoids any reaction with the semi-finished steel product.

[0040] The method according to the invention makes it possible to heat the semi-finished steel product at least partially with renewable energy and / or recovered waste energy in a pre-heating step.

[0041] Alternatively, as shown in FIG. 2, the pre-heating step is performed by at least two pre-heating devices (1, 100).

[0042] The at least two pre-heating devices are arranged such that the outlet pipe (11) of a first pre-heating device (1) is connected to the inlet pipe (90) of a second pre-heating device (100).

[0043] In this case, the preheating step includes the following steps. i. injecting a gas (12, 120) into the chambers (3, 30) of said first and second preheating devices to form a fluidized bed (4, 40); ii. heating the fluidized bed (4, 40) by means of a heat exchanger (5, 50); iii. placing said semi-finished steel product 2 in the fluidized bed (80) of said second pre-heating device (100) and on said support (60) so that said fluidized bed (80) can transfer heat to said semi-finished steel product 2; iv. removing the semi-finished steel product 2 when its temperature is 300°C to 500°C; v. placing said semi-finished steel product 2 in the fluidized bed (8) of said second pre-heating device (1) and on said support (6) so that said fluidized bed (8) can transfer heat to said semi-finished steel product 2; vi. Removing the semi-finished steel product 2 when its temperature is between 500°C and 700°C.

[0044] Such a preheating step makes it possible to heat the semi-finished steel product in several steps in order to increase the efficiency of the transport medium passing through the heat exchanger.

[0045] The invention also relates to a method for heating a semi-finished steel product 2, comprising the steps of: the preheating step being carried out in a preheating device 1 comprising a chamber 3 for containing solid particles 4, a heat exchanger 5, a support 6 capable of supporting said semi-finished steel product, and a gas injector 7; The rolling process in a rolling mill Including, The preheating step includes the following steps: i. injecting a gas 12 into said first chamber 3 to form a first fluidized bed 8; ii. heating the fluidized bed 8 by means of the heat exchanger 5; iii. placing said semi-finished steel product 2 in the fluidized bed 8 so that said semi-finished steel product 2 is supported by said support 6 and said fluidized bed 8 is capable of transferring heat to said semi-finished steel product 2; iv. A step of removing the semi-finished product 2 when its temperature is 150°C to 350°C. Including, The rolling step relates to a method comprising rolling the semi-finished steel product at a temperature of 150-300°C.

Claims

1. A method for heating a semi-finished steel product 2, which is a slab, billet or bloom, comprising the steps of: a preheating step carried out in a preheating device comprising a chamber 3 containing solid particles 4, a heat exchanger 5, a support 6 capable of supporting said semi-finished steel product, a gas injector 7, and a heating step carried out in a furnace, in which the semi-finished steel product is heated to a temperature between 1000 and 1400°C; a hot rolling step after said heating step, in which said semi-finished steel product is hot rolled. Including, The preheating step includes the following steps: i. injecting a gas 12 into the first chamber 3 to form the first fluidized bed 8; ii. Heating the fluidized bed 8 by the heat exchanger 5; iii. Placing the semi-finished steel product 2 in the fluidized bed 8 so that the semi-finished steel product 2 is supported by the support 6 and the fluidized bed 8 is capable of transferring heat to the semi-finished steel product 2; iv. Removing the semi-finished steel product 2 when its temperature is between 200°C and 1000°C. The method includes:

2. The method of claim 1 , wherein the gas injected into the chamber is air.

3. 3. The method of claim 1 or 2, wherein the solid particles of the fluidized bed are in a bubbling regime.

4. A process according to any one of claims 1 to 3, wherein in step ii., the fluidized bed is heated at a temperature of 400 to 700°C, preferably 500 to 700°C, even more preferably 600 to 700°C.

5. A method according to any one of the preceding claims, wherein the semi-finished steel product is removed when its temperature is between 500°C and 700°C.

6. The method according to claim 5, wherein the semi-finished steel product is removed when its temperature is between 600°C and 700°C.

7. A method according to any one of the preceding claims, in which a transport medium circulates through the heat exchanger and is introduced into the heat exchanger at a temperature between 250°C and 1500°C.

8. A method according to any one of the preceding claims, wherein a transport medium circulates through the heat exchanger and leaves the heat exchanger at a temperature between 150°C and 1000°C.

9. A method for heating a semi-finished steel product 2, which is a slab, billet or bloom, comprising the steps of: a heating step carried out in a preheating device 1 comprising a chamber 3 containing solid particles 4, a heat exchanger 5, a support 6 capable of supporting said semi-finished steel product, and a gas injector 7; - Rolling process carried out in a rolling mill Including, The heating step comprises the following steps: i. injecting a gas 12 into said first chamber 3 to form a first fluidized bed 8; ii. Heating the fluidized bed 8 by the heat exchanger 5; iii. placing said semi-finished steel product 2 in said fluidized bed 8 so that said semi-finished steel product 2 is supported by said support 6 and said fluidized bed 8 is capable of transferring heat to said semi-finished steel product 2; iv. Step of removing the semi-finished steel product 2 at a temperature of 150°C to 350°C and The method, wherein the rolling step comprises rolling the semi-finished steel product at a temperature of 150-300°C.

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