Patent Application
20250019784
The invention relates to a method for heating a semi-finished steel product.
In steel production, but more generally in metal production, steel products need to be reheated before undergoing a forming process or heat treatment. This is for example the case of billets or bloom before hot rolling which are generally reheated, from room temperature to a temperature above 1000° C., in a furnace.
However, such a reheating consumes a great amount of energy leading to emission of greenhouse gas. It is thus desirable to develop heating methods of semi-finished product that reduce the process impact on the environment.
It is a subject of this invention to provide such a heating method.
The present invention relates to a method for heating a semi-finished steel product 2, being a slab, a billet or a bloom, comprising
Preferably, said semi-finished steel product, being a slab or a billet or a bloom, is to be laminated.
This device comprises a chamber 3 containing solid particles 4, a heat exchanger 5, a support able to support a semi-finished steel product 6 and a gas injector 7. The chamber is preferentially able to receive more than one semi-finished steel product. The support 6 is preferentially able to receive more than one semi-finished steel product. The support can be a mesh basket. Preferably, in step iii., the semi-finished steel product lies on said support.
The semi-finished steel product may be conveyed inside and outside the chamber by a rolling conveyor or may be placed inside the chamber by pick up means, such as cranes or any suitable pick up mean. For example, the system disclosed in WO 2021 064 451 can be used to as pick up means. Even more preferably, said support is not used move said semi-finished product inside or outside the chamber 3. Dissociating the support system and the transport system, e.g. pick-up means, permits to reduce the number of transport system in case several semi-finished steel products are pre-heated simultaneously.
The chamber may be a closed chamber with a closable opening through which a semi-finished steel product maybe be conveyed, but it could also have an open roof or any configuration suitable for semi-finished steel products conveying.
In step i. of the pre-heating step, a gas is injected into said chamber 3 so as to form a fluidized bed 8. This injection is done by means of the gas injector 7.
Preferably, said gas injected in said chamber is heated. Even more preferably, said gas has a temperature from 200 to 1000° C. It permits reduction of the energy required to heat the fluidized bed at the preferred temperature range. Even more preferably, said gas is at least partly heated by a renewable energy source and/or by recovered waste heat. The recovered waste heat can for example come from reused fumes.
Even more preferably, said gas injected in said chamber is heated by means of heating means powered in part or all by CO2 neutral electricity.
CO2 neutral electricity includes notably electricity from renewable source which is defined as energy that is collected from renewable resources, which are naturally replenished on a human timescale, including sources like sunlight, wind, rain, tides, waves, and geothermal heat. In some embodiments, the use of electricity coming from nuclear sources can be used as it is not emitting CO2 to be produced.
Preferably, said solid particles of said fluidized bed are in a bubbling regime. The gas velocity to be applied to get a bubbling regime depends on several parameters like the kind of gas used, the size and density of the particles or the size of the chamber which are easily managed by a person skilled in the art.
In step ii., the fluidized bed is heated by means of the heat exchanger. The heat exchanger 5 is able to transfer heat to said fluidized bed 8. An entry pipe 9 is connected to said heat exchanger such that a transfer medium can be introduced into the heat exchanger by said entry pipe 9. An exit pipe 11 is connected to said heat exchanger such that the transfer medium can be drained away from the heat exchanger by said exit pipe 11. The walls of the chamber 3 can contain the heat exchanger.
Preferably, in step ii., said fluidized bed is heated at a temperature from 400 to 700° C., preferably from 500 to 700° C., and even more preferably from 600 to 700° C.
Preferably, a transfer medium is circulating in said heat exchanger and is introduced into said heat exchanger at a temperature from 250° C. to 1500° C.
Preferably, said transfer medium is at least partly heated by a renewable energy source.
Preferably, a transfer medium is circulating in said heat exchanger and is exiting said heat exchanger at a temperature from 150° C. to 1000° C.
Even more preferably, said gas is at least partly heated by a renewable energy source and/or by recovered waste heat. The recovered waste heat can for example come from reused fumes.
The step ii. happens simultaneously as the step i., so that while the solid particles form a fluidized bed, they are heated.
In step iii., the semi-finished steel product is put inside the fluidized bed such that it can be heated by the fluidized bed. So, the steps i. and ii. are performed during the step iii. to allow the heat transfer from the heat exchanger to the fluidized bed and also from the heat exchanger to the semi-finished steel product.
Preferably, said semi-finished steel product is at ambient temperature before being brought into the fluidized bed.
Preferably, the whole semi-finished steel product is inside said fluidized bed.
In step iv., the semi-finished steel product is taken out of the fluidized bed when it reaches a determined temperature.
Preferably, said semi-finished steel product is taken out when its temperature is from 500° C. to 700° C. Even more preferably, said semi-finished steel product is taken out when its temperature is from 600° C. to 700° C.
In the heating step, the semi-finished steel product is heated in a furnace to a temperature from 1100° C. to 1400° C. Such a heating range permits to perform a hot rolling.
Preferably, said method comprises a hot rolling step, after the heating step, wherein said semi-finished steel product is hot rolled.
Preferably, said gas injected in said 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 mix of gases.
Preferably, said gas injected in said chamber as a temperature close, or higher, to the one of the fluidised bed.
Preferably, the gas is injected at a velocity from 1 to 30 cm·s−1. Such a velocity range requires a low ventilation power and thus a reduced energy consumption
Preferably, the solid particles have a size from 40 to 500 μm.
Preferably, the solid particles have a heat capacity comprised from 500 to 2000 J·kg−1·K−1.
Preferably, the bulk density of the solid particles is from 1400 to 4000 kg·m−3.
Preferably, the solid particles are ceramic particles. Preferably, the solid particles are made of glass or any other solid materials chemically stable up to 1000° C. For example, the solid particles can be made of SiC, Olivine, steel slag or alumina.
Preferably, the solid particles are inert. It avoids any reaction with the semi-finished steel product.
The method according to the invention permits to heat, at least partly a semi-finished steel product by means of renewable energy and/or recovered waste energy, in the pre-heating step.
Alternatively, as illustrated in
Said at least two pre-heating devices are arranged such that the exit pipe (11) of a first pre-heating device (1) is connected to an entry pipe (90) of a second pre-heating device (100).
In that case, the pre-heating step comprises the steps of
Such a pre-heating steps permits to heat the semi-finished steel product in several steps so as to increase the efficiency of the transfer medium passing through the heat exchangers.
The invention also relates to a method for heating a semi-finished steel product 2, comprising:
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/IB2021/061689 | Dec 2021 | WO | international |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/061704 | 12/2/2022 | WO |
