Method for heating gas and steelmaking vessel thereof

Abstract

The invention relates to a steelmaking manufacturing device for heating gas wherein said device comprises: - a pipe allowing gas to flow inside of it, - an insert located inside said pipe, said insert being electrically conductive, - an inductor located in the vicinity of said pipe and able to feed energy into said insert, so that said energy fed into said insert is transferred to the gas flowing into said pipe, so that said gas is heated to a temperature from 300°C to 2300°C.

Description

[0001] Method for heating gas and steelmaking vessel thereof

[0002]

[0001] The present invention relates to a method for heating gas and the associated steelmaking vessel. More precisely, the present invention relates to a method and a steelmaking vessel for heating gas using induction heating.

[0003]

[0002] In the steel industry, there are various processes that needs hot gas of a temperature around 1000°C. In classical facilities, the heating of gas is usually done using fuel combustion, especially in ironmaking. Hot stoves, for example, are regenerative heaters that uses fuel combustion where the heater shifts alternatively from an oxidizing phase to a reducing phase to heat a reducing gas.

[0004]

[0003] However, fuel combustion causes CO2 emissions and as CO2 emissions need to be reduced in the steel industry, there is a need for alternative devices for heating gas that allow CO2 emissions to be reduced or even suppressed.

[0005]

[0004] It is known from Chinese patent application CN113566044 that a gas can be heated to a temperature of around 1000°C with an electrical method, more precisely, using induction heating. The patent application describes a method for continuously heating a chlorine gas to a temperature of 700°C to 1600°C consisting in heating a graphite pipeline using an induction heater and making the chlorine gas flow into the hot pipe.

[0006]

[0005] This method allows the heating of gas without the use of combustion thus reducing CO2 emissions of the process. However, for the usual flow rates of gas needed in common applications of the steel industry, the implementation of this method is difficult as it would require a massive installation to reach similar temperatures.

[0007]

[0006] The aim of the present invention is therefore to remedy the drawbacks of the prior art by providing a method for heating gas within a limited space while reducing CO2 emissions.

[0007] For this purpose, a first object of the present invention consists in a method for heating gas wherein said method comprises the following steps:

[0008] - introducing gas into a steelmaking vessel, said steelmaking vessel comprising a pipe, said pipe comprising an insert located inside said pipe, said insert being electrically conductive, so that said gas flows into said pipe,

[0009] - feeding energy into said insert using an inductor, said inductor being located in the vicinity of said pipe, so that said energy fed into the insert is transferred to the gas flowing into said pipe, so that said gas is heated to a temperature from 300°C to 2300°C,

[0010] - further using said heated gas in steelmaking manufacturing processes.

[0011]

[0008] The method for heating gas according to the invention may also have the optional features listed below, considered individually or in combination:

[0012] - the gas is heated to a temperature from 400°C to 1500°C,

[0013] - the flow of gas inside the pipe of the steelmaking vessel has a Reynolds number superior to 2800,

[0014] - the heated gas is composed of one or more of the following gases: syngas, CO2, CO, H2, H2O, hydrocarbons, N2.

[0015]

[0009] A second object of the invention consists in a steelmaking manufacturing vessel wherein said vessel comprises:

[0016] - means for injecting gas into said steelmaking manufacturing vessel,

[0017] - a pipe allowing the gas injected to flow inside of it,

[0018] - an insert located inside said pipe, said insert being electrically conductive,

[0019] - an inductor located in the vicinity of said pipe and able to feed energy into said insert, so that said energy fed into said insert is transferred to the gas flowing into said pipe, wherein said steelmaking manufacturing vessel has a power from 1 kWto 50MW.

[0010] The steelmaking manufacturing vessel according to the invention may also have the optional features listed below, considered individually or in combination:

[0020] - the insert is designed to have an exchange surface with the gas to be heated that ranges from 0.5m2to 100m2by meter of pipe,

[0021] - the section of the insert represents from 50% to 100% of the free section of the pipe,

[0022] - the insert is made of one of the following materials: magnetic steel, graphite, tungsten, molybdenum,

[0023] - the inductor is a coil.

[0024]

[0011] Other characteristics and advantages of the invention will be described in greater detail in the following description.

[0025]

[0012] The “steelmaking manufacturing vessel” will be referenced in the rest of the description as “steelmaking vessel”. “Steelmaking” in “steelmaking manufacturing vessel” is to be understood as any process used in a steel plant for the production of iron, pig iron and / or steel, starting from the ferrous raw materials to the final product.

[0026]

[0013] The invention will be better understood by reading the following description, which is provided purely for purposes of explanation and is in no way intended to be restrictive, with reference to:

[0027]

[0014] Figure 1 , which is a general view of the steelmaking vessel according to one embodiment of the invention,

[0028]

[0015] Figure 2, which is a cross-sectional view of the interior of the pipe of the steelmaking vessel according to another embodiment of the invention,

[0029]

[0016] Figure 3a and 3b, which are representations of embodiments of the insert of the steelmaking vessel according to the invention,

[0030]

[0017] Figure 4, which is a comparative graph representing the heating of a gas with a method according to the prior art and the method according to the invention.

[0018] With reference to Figure 1 and 2, the method for heating gas and the steelmaking manufacturing vessel according to the invention will be described in detail.

[0031]

[0019] The steelmaking vessel according to the invention first comprises a pipe 1 that allows the gas to be heated to flow inside of it. The gas is introduced into the pipe 1 using means for injecting gas inside the pipe 1 , located at the entrance of the pipe 1 . The steelmaking vessel also comprises an insert 2 located inside the pipe 1 and that is electrically conductive. The steelmaking vessel also comprises an inductor 3 located in the vicinity of the pipe 1 . The inductor 3 feeds energy to the insert 2 by creating a magnetic field that induces a current in the insert 2. This energy fed to the insert 2 results in the heating of the insert 2. This energy is then transferred from the hot insert 2 to the gas flowing into the pipe 1 that is thus heated to a temperature from 300°C to 2300°C. The heated gas then exits the pipe 1 to be further used in a subsequent process.

[0032]

[0020] The insert 2 is a piece that is located inside the pipe 1 . Its purpose is to transfer energy to the gas flowing into the pipe 1 . This transfer occurs as the gas flows into the pipe 1 and enters in contact with the exchange surface of the insert 2. The gas is thus heated by forced convection and / or radiation.

[0033]

[0021] For the structure of the insert 2, increasing the exchange surface will improve the efficiency of the heating as the insert 2 can transfer more energy to the gas over the length of the pipe 1 . The exchange surface corresponds to the surface of the insert 2 that the gas can enter in contact with. The higher the surface exchange of the insert 2 is, the shorter the pipe 1 length required to reach a given target temperature is as well.

[0034]

[0022] For each meter of length of pipe 1 , the insert 2 preferably has an exchange surface from 0.5 m2to 100 m2For an exchange surface below 0.5 m2for each meter of length of pipe 1 , the efficiency of the heating can be insufficient to reach the target temperature. For an exchange surface above 100 m2for each meter of pipe 1 , the gas could reach the target temperature way before the end of the pipe 1 thus reducing the efficiency of the heating compared to the material used. Alternatively, for each meter of length of pipe 1 , the insert has an exchange surface from 0.5 m2to 80 m2or from 0.5 m2to 60 m2or from 0.5 m2to 50 m2or from 0.5 m2to 40 m2or from 0.5 m2to 30 m2or from 0.5 to 25 m2or from 0.5 m2to 20 m2or from 0.5 m2to 15 m2or from 0.5 m2to 10 m2or from 0.5 m2to 7.5 m2or from 0.5 m2to 5 m2or from 0.5 to 2.5 m2or from 1 m2to 100 m2or from 1 m2to 80 m2or from 1 m2to 60 m2or from 1 m2to 50 m2or from 1 m2to 40 m2or from 1 m2to 30 m2or from 1 to 25 m2or from 1 m2to 20 m2or from 1 m2to 15 m2or from 1 m2to 10 m2or from 1 m2to 7.5 m2or from 1 m2to 5 m2or from 1 m2to 2.5 m2

[0035]

[0023] The efficiency of the heating can also be improved by imposing an agitation to the gas flow inside the pipe 1. This is provided by creating a turbulent flow inside the pipe 1 .

[0036]

[0024] The flow patterns are usually characterized by the Reynolds number (Re). Usually, the Reynolds number is defined as: puL Re = - —

[0037] A p: density of the fluid (kg.rrr3) u: flow speed (m.s’1)

[0038] L: characteristic length (m) p: dynamic viscosity (kg. (m.s)’1)

[0039] A turbulent flow is characterized by a Reynolds number Re > 2800.

[0040]

[0025] The shape of the insert 2 has an influence on the Reynolds number as it modifies the characteristic length L of the system. A shape designed to provide turbulent flow to the gas flowing into the pipe 1 can thus improve the efficiency of the heating of the gas.

[0041]

[0026] To further improve the efficiency, the insert 2 preferably extends from the entrance of the pipe 1 to the exit of the pipe 1 . The insert 2 also preferably has a section that represents from 50% to 100% of the free section inside the pipe 1 , that is to say, the section where the gas is flowing. Having an insert 2 with a section that is almost the same as the free section of the pipe 1 allows to avoid that a large fraction of the gas flows around the insert 2 without being heated by the insert 2. However, having a smaller section allows the insert 2 to expand more freely with thermal dilatation without damaging the steelmaking vessel. An insert 2 with a section of 100% of the free section of the pipe 1 can be considered with a material such as Invar™ that has a thermal expansion rate sufficiently low so as not to damage the pipe 1 . With a section lower than 50% of the free section of the pipe 1 , the efficiency of the heating could be too low. Alternatively, the section of the insert 2 comparatively to the free section of the pipe 1 is from 50% to 97.5% or from 50% to 95% or from 50% to 92.5% or from 50 to 90% or from 50% to 85% or from 50% to 80% or from 50% to 75% or from 60% to 97.5% or from 60% to 95% or from 60% to 92.5% or from 60 to 90% or from 60% to 85% or from 60% to 80% or from 60% to 75% or from 65% to 97.5% or from 65% to 95% or from 65% to 92.5% or from 65 to 90% or from 65% to 85% or from 65% to 80% or from 65% to 75% or from 70% to 97.5% or from 70% to 95% or from 70% to 92.5% or from 70 to 90% or from 70% to 85% or from 70% to 80% or from 70% to 75%.

[0042]

[0027] Examples for insert designs are represented in Fig 3a and Fig 3b. The insert represented in Fig 3a has a screw shape and the insert represented in Fig 3b has a perforated twisted tape shape. These designs provide a high exchange surface comparatively to the length of the pipe 1 and can also provide a turbulent flow for typical gas speeds used in steelmaking processes.

[0043]

[0028] The designs of the insert 2 are not limited to the ones represented in Fig 3a and Fig 3b and other designs can be considered.

[0044]

[0029] In order to be heated, the insert 2 has to be made of a material that is electrically conductive. The insert 2 is preferably made of magnetic steel or graphite but can also be made of any electrically conductive material. An electrically conductive material is any material that has an electrical conductivity value o > 10 000 (Q.m)’1.

[0045]

[0030] Magnetic steel can be used as a material for the insert 2 for heating non oxidizing gas to temperatures up to 1000°C, preferably up to 1200°C without material degradation. For higher temperatures, it is preferable to use graphite as a material for the insert 2 as graphite can reach temperatures higher than 3000°C. Tungsten and molybdenum can also be considered as material for the insert 2 for high temperatures as they can resist to temperatures higher than 3000°C. For heating oxidizing gases, stainless steel can be used as the induced material.

[0046]

[0031] The insert can be manufactured using additive manufacturing.

[0047]

[0032] The inductor 3 is preferably a coil and is located in the vicinity of the pipe 1 . Preferably, the inductor 3 is located inside the pipe 1 close to its wall as represented in Fig 2. This configuration allows to avoid heating the pipe 1 alongside the insert 2 if the pipe is made of a material that is also electrically conductive. In this configuration, a refractory material is placed between the insert 2 and the inductor 3 to serve as a thermal insulator. A magnetic yoke is also preferably installed inside the pipe 1 , between the inductor 3 and the wall of the pipe 1 . It can be a plate of electric steel. Its purpose is to confine the magnetic field inside the pipe 1 so as not to heat the pipe 1 to increase the energy efficiency. Alternatively, the inductor 3 can be placed outside the pipe 1 , as in Fig 1 , if the pipe 1 is made of a material that is not electrically conductive.

[0048]

[0033] A various number of gases can be heated using the method for heating gas according to the invention. The following Table 1 gives a list of gases that can be heated using two specific materials for the insert 2.

[0049] Table 1

[0034] The gases that are listed in table 1 are only listed as examples and the gases that can be heated using the invention are not limited to these gases. In the same way, the materials that are listed in Table 1 are only listed as examples and the materials that are used for the insert in the invention are not limited to these materials.

[0050]

[0035] A step of cleaning the gas is preferably done before heating to remove most of the particles that can be present. This step of cleaning can be done with a specific equipment using venturi effect and scrubbers to remove particles with water. This step can also be done by mechanical separation or any other means to remove particles from a gas. Preferably, the amount of particles in the heated gas is not more than 5mg / Nm3. Nm3stands for Normal cubic meters and is a unit of measurement of the quantity of gas which corresponds to the content of a volume of one cubic meter, for a gas under normal temperature and pressure conditions (0°C and 1 atm.). Preferably, the size of the particles present in the heated gas is not more than 50pm.

[0051]

[0036] The pipe 1 preferably has a cylindrical shape. To reach a certain power, a minimal surface and / or mass of induced material is needed in the form of the insert 2. The shape of the insert 2 and the dimensions of the pipe 1 are arranged to provide optimal efficiency and compacity of the steelmaking vessel depending on the power needed for the application it is used for. As the pipe 1 is not heated in the method for heating gas according to the invention, the thickness of the pipe 1 does not have an influence on the efficiency of the heating contrary to the prior art where the pipe 1 itself is heated.

[0052]

[0037] The gas is heated to a temperature from 300°C to 2300°C. Preferably, the gas is heated to a temperature from 400°C to 1500°C.

[0053]

[0038] The gas temperature needed at the exit of the steelmaking vessel depends on the application it is used for. For example, galvanization requires a temperature from 400°C to 700°C. A preferred temperature for the application at the blast furnace is from 700°C to 1500°C. A range from 800°C to 1100°C is preferably used for direct reduction of iron applications.

[0039] The flow rates for the gas that are considered for the invention are usual flow rates of gas for the application the invention is used for. The person skilled in the art would know what flow rates of gas is needed for the application he wants to use the invention.

[0054]

[0040] In the applications of the method for heating gas according to the invention, a given global gas flow rate of a given composition is heated to a target temperature. Depending on the value of this global gas flow rate and the target temperature, the required global heating power can range from 1 kW to 50MW. For low power values, for example in the order of 1 kW to 10kW, a single steelmaking vessel would be sufficient to provide this level of power. For higher power range, for example in the order of 10MW to 50MW, depending on the technology available to the person skilled in the art, a single steelmaking vessel can be insufficient to obtain this level of power. In this case, the global gas flow rate to be heated can be divided in several streams of lower flow rate that will each be heated by a single steelmaking vessel and require much lower power to reach the same target temperature.

[0055]

[0041] Preferably, the power of the steelmaking vessel is from 1 kW to 10MW, more preferably from 1 kW to 1 MW, more preferably from 1 kW to 100kW, more preferably from 1 kW to 50kW, more preferably from 1 kW to 10kW.

[0056]

[0042] Fig 4 represents a comparative heating of a gas heated according to the prior art and a gas heated according to the invention. The first curve represents the heating with a method for heating gas according to the prior art. A gas flows inside the pipe and the pipe is heated using induction heating. The second curve represents the heating with the method according to the invention. The pipe is not heated and only the insert is heated.

[0057]

[0043] The curves were calculated using a simulation using Fluent, a software published by Ansys, Inc. For both curves, the conditions of heating are the same. The pipe has a diameter of 300mm, a thickness of 5mm and a length of 2m. The gas heated is H2 with a mass flow of 68kg / h. For the curve of the heating according to the invention, the inductor 3 is located outside the pipe 1 , the insert 2 is of screw type, like represented in Fig 3a, with a diameter equal to the diameter of the pipe 1 . The total surface of the insert is 2.66 m2and the Reynolds number is 9300.

[0058]

[0044] The comparison shows that a more efficient heating over a shorter length can be obtained with the method according to the invention.

[0059]

[0045] The method for heating gas according to the invention allows to successfully heat gas within a limited space while reducing CO2 emissions.

Claims

CLAIMS1 ) A method for heating gas wherein said method comprises the following steps:- introducing gas into a steelmaking manufacturing vessel, said steelmaking manufacturing vessel comprising a pipe (1 ), said pipe (1 ) comprising an insert (2) located inside said pipe (1 ), said insert (2) being electrically conductive, so that said gas flows into said pipe (1 ),- feeding energy into said insert (2) using an inductor (3), said inductor (3) being located in the vicinity of said pipe (1 ), so that said energy fed into the insert (2) is transferred to the gas flowing into said pipe (1 ), so that said gas is heated to a temperature from 300°C to 2300°C,- further using said heated gas in steelmaking manufacturing processes.2) A method for heating gas according to claim 1 wherein said gas is heated to a temperature from 400°C to 1500°C.3) A method for heating gas according to any of the preceding claims wherein the flow of gas inside the pipe of the steelmaking manufacturing vessel has a Reynolds number superior to 2800.4) A method for heating gas according to any of the preceding claims wherein said heated gas is composed of one or more of the following gases: syngas, CO2, CO, H2, H2O, hydrocarbons, N2.5) A steelmaking manufacturing vessel wherein said vessel comprises:- means for injecting gas into said steelmaking manufacturing vessel,- a pipe (1 ) allowing the gas injected to flow inside of it,- an insert (2) located inside said pipe (1 ), said insert (2) being electrically conductive,- an inductor (3) located in the vicinity of said pipe (1 ) and able to feed energy into said insert (2), so that said energy fed into said insert (2) is transferred to the gas flowing into said pipe (1 ),wherein said steelmaking manufacturing vessel has a power from 1 kW to 50MW.6) A steelmaking manufacturing vessel according to claim 5 wherein said insert (2) is designed to have an exchange surface with the gas to be heated that ranges from 0.5m2to 100m2by meter of pipe (1 ).7) A steelmaking manufacturing vessel according to any of claims 5 or 6, wherein the section of said insert (2) represents from 50% to 100% of the free section of the pipe (1 ).8) A steelmaking manufacturing vessel according to any of claims 5 to 7 wherein said insert (2) is made of one of the following materials: magnetic steel, graphite, tungsten, molybdenum.9) A steelmaking manufacturing vessel according to any of claims 5 to 8 wherein said inductor (3) is a coil.

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