How to heat a furnace

Abstract

1. A method for heating a furnace equipped with a radiant tube and capable of heat treating a traveling steel strip, comprising the steps of: i. supplying H2 and O2 to at least one of the radiant tubes such that the H2 and O2 combine into heat and steam; ii. recovering the vapor from the at least one of the radiant tubes; iii. electrolyzing the vapor to produce H2 and O2; iv. supplying the H2 and O2 produced in step iii. to at least one of the radiant tubes, where the H2 and O2 are combined to form heat and steam. A method comprising:

Description

[Technical Field]

[0001] The present invention relates to a method for heating a furnace that includes a radiant tube. [Background technology]

[0002] During its manufacture, steel strip undergoes heat treatment to achieve desired properties. Heat treatment facilities include heating means such as direct fired furnaces (DFF), drop tube furnaces (DTF) and radiant tube furnaces (RTF).

[0003] For some heat treatments, such as annealing, it is preferable to use a radiant tube furnace, since in such a furnace the strip is not in direct contact with the combustion products of the flame, and the atmosphere inside the furnace can be controlled.

[0004] Radiant tubes are typically fired using gaseous fuels or oil. However, recent developments have led to radiant tubes that consume H2 and O2 to generate heat. Unfortunately, producing H2 from natural sources is energy intensive and produces greenhouse gas emissions. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need to develop a method of heating a furnace with a radiant tube that has a reduced impact on the environment. [Means for solving the problem]

[0006] This is achieved by providing a method as claimed in any one of claims 1 to 7. This is also achieved by providing an installation as claimed in any one of claims 8 to 12. [Brief explanation of the drawings]

[0007] [Figure 1]1 shows an installation for carrying out the method of the invention, comprising a furnace 1 including a radiant tube 2, an electrolyzer 3 capable of electrolyzing steam to produce H2 and O2, and pipes (not shown in FIG. 1). [Figure 2] A solid oxide electrolysis cell is shown that uses a solid ceramic material as the electrolyte 11 that selectively conducts negatively charged oxygen ions (O2 -) or positively charged hydrogen protons (H+), depending on the type of membrane. [Figure 3] A solid oxide electrolysis cell is shown that uses a solid ceramic material as the electrolyte 11 that selectively conducts negatively charged oxygen ions (O2 -) or positively charged hydrogen protons (H+), depending on the type of membrane. DETAILED DESCRIPTION OF THE INVENTION

[0008] Other features and advantages will become apparent from the following description of the invention.

[0009] The present invention relates to a method for heating a furnace equipped with a radiant tube and capable of heat treating a moving steel product, the method comprising the steps of: i. supplying H2 and O2 to at least one of the radiant tubes such that the H2 and O2 combine into heat and steam; ii. recovering the vapor from the at least one of the radiant tubes; iii. electrolyzing the vapor to produce H2 and O2; iv. supplying the H2 and O2 produced in step iii to at least one of the radiant tubes, wherein the H2 and O2 are combined to form heat and steam. The present invention relates to a method comprising:

[0010] The furnace heating method is a method of providing heat to the furnace so that the temperature reaches a temperature at which the traveling steel strip can be heat treated.

[0011] The method can be carried out in an installation having a furnace 1 including a radiant tube 2, an electrolyzer 3, such as a solid oxide electrolysis cell (SOEC), capable of electrolyzing steam to produce H and O, and piping (not shown in FIG. 1), as shown in FIG. 1. Optionally, the installation can include a pumping system to facilitate gas flow.

[0012] The radiant tube is connected to the electrolyzer via pipes so that at least two gas streams (4 and 4') can flow from the electrolyzer to the furnace, e.g., to the radiant tube, and one gas flux 5 can flow from the furnace, e.g., from the radiant tube, to the electrolyzer. The furnace is also preferably connected to means capable of supplying H2 and O2, e.g., an external source of H2 and an external source of O2.

[0013] Optionally, storage means may be used between the furnace and the electrolyser to at least partially store at least one of the products of the electrolysis.

[0014] Preferably, the running steel product is a running steel strip or a running steel slab.

[0015] The furnace is designed to heat treat steel products, such as annealing steel strips or heating steel slabs. Preferably, the furnace is an annealing furnace. The radiant tube is part of a radiant tube burner. Preferably, the radiant tube burner is an oxy-fuel radiant tube burner.

[0016] In step i., H2 and O2 are supplied to at least one radiant tube, as shown in Figure 1. These two gases are combined by the radiant tube to produce heat and steam. H2 and O2 are supplied from a storage device and / or an electrolyzer. The steam consists essentially of H2O molecules.

[0017] Preferably, in step i., at least one of the radiant tubes is supplied with H and O under conditions that allow their ignition and thus the combination to become heat and steam. Those skilled in the art will be able to determine the parameters that lead to the ignition of H and O.

[0018] For example, the furnace can include a radiant tube burner to which the H and O are supplied, which can generate a pilot flame or spark, allowing the supplied H and O to ignite, thus converting the combination into heat and steam.

[0019] Alternatively, O2 can be supplied at a temperature of at least 550°C, preferably at least 600°C, and even more preferably at least 700°C. H2 can be supplied at room temperature or above, preferably at least 200°C, more preferably at least 300°C, and even more preferably at least 400°C. This alternative was developed with the intention of creating a synergistic effect between the three first process steps. In fact, heating O2 and H2 in step i. increases the temperature of the recovered steam in step ii., thus increasing the efficiency of electrolysis in step iii. In contrast, prior art developments, such as WO2016102825, disclose processes for supplying gases at low temperatures to increase the energy efficiency of the process.

[0020] The furnace may include at least an oxy-fuel burner, such as an oxy-hydrogen burner with a radiant tube, which may include a heat exchanger capable of heating gas between the burner inlet and the burner nozzle.

[0021] Preferably, the radiant tube burner can preheat the O and optionally the H supplied to the radiant tube burner. Thus, the first step can also include preheating the supplied O and optionally the supplied H prior to combining, e.g., ignition.

[0022] In step ii., the vapor is recovered from the radiant tube to be used in further steps.

[0023] However, due to incomplete combustion and / or a suboptimal O2 / H2 ratio, H2 and / or O2 may be present in the steam. Also, the steam may contain residues from previous combustion in the radiant tube. This is especially true when the radiant tube is operated with oil or natural gas.

[0024] In step iii., the steam recovered in step ii. is electrolyzed to produce H2 and O2, some of which may be diverted to storage means.

[0025] Preferably, the electrolysis is carried out by at least one solid oxide electrolysis cell. As shown in Figures 2 and 3, a solid oxide electrolysis cell generates negatively charged oxygen ions (O2) depending on the type of membrane (e.g., an oxygen ion conducting membrane or a proton conducting membrane, respectively). - ) or positively charged hydrogen protons (H + ) is used as the electrolyte 11, which selectively conducts the

[0026] The vapor at the cathode 12 combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions. Thus, the reaction at the cathode is HO + 2e - →H2+O2 - Since the vapor may contain other gases and / or residues, the H2 exiting the electrolyzer may be filtered by a membrane separator 14 as shown in FIG.

[0027] The charged oxygen ions then pass through the solid ceramic membrane 11 and react at the anode 13 to form oxygen gas and generate electrons for the external circuit. Thus, the reaction at the anode is: - →O2+4e - .

[0028] This is preferably done at high temperatures, making it possible to produce hydrogen and oxygen from the steam.

[0029] This electrolysis reaction is endothermic and therefore requires an external energy input, e.g., heat and / or electricity, for it to occur. It is therefore particularly advantageous to carry out this electrolysis using steam exiting a furnace having a high temperature.

[0030] Alternatively, in step iii, the electrolysis can be carried out by a water vapor electrolyzer using electrodes made of porous metal with an electrolyte made of a composite ionic material. This system advantageously allows for the electrolysis of steam having a temperature higher than 300°C in step iii. Preferably, the steam electrolyzed in step iii is electrolyzed by a water-injected electrolyzer and has a temperature of 300°C to 1000°C, more preferably 400°C to 1000°C.

[0031] In step iv., at least one radiant tube of the equipment is supplied with H2 and O2 produced in step iii.

[0032] Preferably, in step ii., the recovered steam is heated to a temperature of 650° C. to 1000° C. Even more preferably, the recovered steam is heated to a temperature of 700° C. to 1000° C. Such heating of the recovered steam makes it possible to increase the efficiency of the SOEC.

[0033] In this case, the installation comprises heating means capable of heating the recovered steam. Preferably, in step ii., the heating of the recovered steam is performed by heating means powered partly or completely by CO2-neutral electricity.

[0034] For example, the heating means may be a heat exchanger 7 connected to the radiant tube and the electrolyser so as to heat the gas stream from the radiant tube before it enters the electrolysis system.

[0035] Preferably, the steam electrolyzed in step iii. has a temperature between 650°C and 1000°C, even more preferably between 700°C and 1000°C.

[0036] Preferably, in step iii., the electrolysis of the steam is partially or completely powered by CO2-neutral electricity.

[0037] 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, electricity derived from nuclear sources can be used, as it does not emit the CO2 that is produced.

[0038] Preferably, in step iv., the radiant tube is supplied with H2 and O2 produced in step iii. and H2 and / or O2 from a storage means, so that the H2 and O2 combine to form heat and steam.

[0039] Preferably, steps ii., iii. and iv. are repeated.

[0040] The use of radiant tubes that consume H2 and O2 in a semi-closed loop allows the furnace to be heated in a manner that requires fewer energy and natural resources compared to prior art heating methods.

[0041] The present invention also provides an apparatus capable of carrying out the above-described method, comprising: - a furnace (1) equipped with at least one radiant tube (2) and capable of heat treating a moving steel product; - an electrolyzer (3) capable of electrolyzing steam to produce H2 and O2; the electrolyzer is connected to the radiant tubes 2 such that at least two gas streams (4 and 4') can flow from the electrolyzer 3 to the radiant tubes 2 and one gas flux 5 can flow from the radiant tubes 2 to the electrolyzer, the furnace is configured to supply H2 and O2 to at least one of the radiant tubes 2, the H2 and O2 can be combined to become heat and steam, and the furnace is configured to recover the steam from at least one of the radiant tubes.

[0042] Preferably, the furnace is configured to supply the H2 and O2 produced in step iii to at least one of the radiant tubes, such that the H2 and O2 combine to form heat and steam.

[0043] Preferably, the furnace is capable of treating a running steel strip or a running steel slab.

[0044] The furnace may include at least an oxy-fuel burner, such as an oxy-hydrogen burner, having a radiant tube. The oxy-hydrogen burner may include a heat exchanger capable of heating gas between the burner inlet and the burner nozzle. The radiant tube is part of the radiant tube burner. Preferably, the radiant tube burner is an oxy-fuel radiant tube burner.

[0045] Preferably, the electrolyzer comprises at least one solid oxide electrolysis cell.

[0046] Preferably, the facility comprises heating means capable of heating steam, the heating means being connected to the furnace and the electrolyzer.

[0047] Preferably, the installation comprises at least storage means capable of storing gas and connected to the electrolyser such that a flow of gas can pass from the electrolyser to the storage means.

[0048] More preferably, at least said storage means is connected to said furnace so that a flow of gas can pass from said storage means to said furnace.

Claims

1. 1. A method for heating a furnace having at least one radiant tube and capable of heat treating traveling steel products, comprising the steps of: i.H ２ and O ２ At least one of the radiant tubes is connected to a H ２ and O ２ supplying a ii. Recovering the vapor from at least one of the radiant tubes; iii. Electrolyzing the vapor to produce H ２ and O ２ generating a iv. In at least one of the radiant tubes, the H produced in step iii. ２ and O ２ and H ２ and O ２ is combined to form heat and steam A method comprising:

2. 2. The method of claim 1, wherein in step ii., the recovered vapor is heated to a temperature of from 650°C to 1000°C.

3. 3. The method of claim 2, wherein in step ii., the recovered vapor is heated to a temperature of from 700°C to 1000°C.

4. 4. The method according to any one of claims 1 to 3, wherein in step iii., the electrolysis is carried out by means of at least one solid oxide electrolysis cell.

5. In step iv., the radiation tube is charged with the H generated in step iii. ２ and O ２ , and H from the storage means ２ and / or O ２ is supplied, and H ２ and O ２ The method of any one of claims 1 to 4, wherein the is combined to heat and steam.

6. In step iii., the electrolysis of the steam produces CO ２ The method of any one of claims 1 to 5, powered partly or completely by neutral electricity.

7. In step ii., the heating of the recovered vapor is performed by CO ２ A method according to any one of claims 2 to 6, carried out by heating means powered partly or completely by neutral electricity.

8. An installation capable of carrying out the method according to any one of claims 1 to 7, a furnace 1 equipped with at least one radiant tube 2 and capable of heat treating moving steel products; - Electrolyze steam to produce H ２ and O ２ an electrolyzer 3 capable of producing The electrolyzer is connected to the radiant tube 2 in such a way that at least two gas fluxes (4 and 4') can flow from the electrolyzer 3 to the radiant tube 2 and one gas flux 5 can flow from the radiant tube 2 to the electrolyzer, and the furnace is ２ and O ２ At least one of the radiant tubes 2 is provided with H so that the ２ and O ２ and the furnace is configured to recover the steam from at least one of the radiant tubes.

9. 9. The facility of claim 8, wherein the electrolyzer comprises at least one solid oxide electrolysis cell.

10. 10. The installation according to claim 8 or 9, further comprising heating means capable of heating steam, said heating means being connected to said furnace and said electrolyzer.

11. 11. The installation according to any one of claims 8 to 10, comprising at least storage means capable of storing gas and connected to the electrolyser such that a flow of gas can flow from the electrolyser to the storage means.

12. 12. The installation of claim 11, wherein at least the storage means is connected to the furnace so that a flow of gas can flow from the storage means to the furnace.

Images