Device for blowing reducing gas in blast furnace and design method thereof

Abstract

The invention belongs to the technical field of blast furnace injection, and relates to a device for injecting reducing gas into a blast furnace, which comprises an injection pipeline for conveying the reducing gas to the center of the blast furnace from the furnace top or the furnace body of the blast furnace, the injection pipeline adopts a double-sleeve design, an internal channel in the injection pipeline is a hot gas channel, and an external channel in the injection pipeline is a cold gas channel. Reducing gas can be sent to the center of the blast furnace, the reducing gas can make contact with more ore, the reduction effect is improved, the utilization rate is increased, direct carbon consumption is reduced, according to the design method, the inner diameter of the injection pipeline and the material of the injection pipeline are designed according to the injection amount and the injection temperature of the reducing gas, and the design cost is reduced. Therefore, the flow velocity V'in the internal channel used for blowing hot gas in the blowing pipeline is smaller than the economic flow velocity V0, and the working temperature is within the allowable use temperature range, so that the cost of reducing gas blowing is reduced, and the service life of the device is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of blast furnace injection, and relates to a device for injecting reducing gas into a blast furnace and a design method thereof. Background Art

[0002] As the pillar and basic industry of the national economy, the steel industry is an important support for the sustained growth of my country's economy. As the leading process of the steel industry, ironmaking accounts for more than 70% of the energy consumption and carbon emissions of the steel industry. Carbon reduction in blast furnaces is a key area of ​​industry development in the near and medium term. Replacing part of the coke and coal powder with reducing gas is an effective way to reduce carbon in blast furnaces. However, the current conventional injection method makes it difficult to send reducing gas to the center of the blast furnace. Most of the reducing gas escapes along the side wall of the blast furnace, which greatly reduces the reduction effect and affects the carbon reduction effect.

[0003] Therefore, how to deliver reducing gas into the center of the blast furnace, enhance its reducing effect, improve the airflow distribution in the furnace, and achieve more carbon reduction has become a problem that needs to be solved urgently. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a device for injecting reducing gas into a blast furnace and a design method thereof, so as to overcome the deficiencies of the prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A device for injecting reducing gas into a blast furnace comprises an injection pipe for sending reducing gas from the top or body of the blast furnace to the center of the blast furnace. The injection pipe is of double-tube design, and the inner channel in the injection pipe is a hot gas channel, and the outer channel is a cold gas channel.

[0007] Furthermore, two ends of the blowing pipeline are respectively a gas inlet and a gas outlet, and the gas outlet is located above the soft melting zone in the blast furnace.

[0008] Furthermore, a flange is provided at the gas inlet of the injection pipeline to connect to an external pipeline.

[0009] Furthermore, the gas outlet is located 1 to 10 m above the soft melting zone.

[0010] Furthermore, it also includes a support frame, which is fixedly installed on the outside of the blast furnace shell and connected to the part of the injection pipeline located outside the blast furnace to support the injection pipeline.

[0011] Furthermore, the material of the blowing pipe is carbon steel, heat-resistant stainless steel or alloy steel.

[0012] Furthermore, a layer of wear-resistant alloy or wear-resistant spray coating is provided on the outer side of the spray pipe.

[0013] A method for designing a device for injecting reducing gas into a blast furnace, which is used for designing the device for injecting reducing gas into a blast furnace, comprises the following steps:

[0014] S1: Obtain the hot gas flow Q' and its injection temperature T' and injection pressure P', the cold gas flow Q'' and its injection temperature T'' and injection pressure P'' in the injection pipeline;

[0015] S2: Select the inner diameter D1 of the inner channel in the blowing pipe, the inner diameter D2 of the outer channel and the material of the blowing pipe;

[0016] S3: Calculate the flow velocity V' of the internal channel in the spray pipe and the inner wall temperature T1 of the internal channel according to the above parameters;

[0017] S4: Determine whether the flow rate V' is less than the economic flow rate V0, and whether the temperature T1 is less than the allowable use temperature T0 of the injection pipe material;

[0018] S5: If the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0, it can be determined that the inner diameter D1 and the inner diameter D2 and the material of the injection pipe meet the design standards;

[0019] If the flow rate V' is not less than the economic flow rate V0, or the temperature T1 is not less than the temperature T0, return to step S2 to reselect the inner diameter D1 and the inner diameter D2 and the material of the blowing pipe so that the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0.

[0020] Furthermore, the flow velocity V' is calculated as follows:

[0021]

[0022] Nu=0.023Re 0.8 Pr 0.4

[0023]

[0024] Where: V' is the flow rate of the inner channel, V" is the flow rate of the outer channel, T1 is the inner wall temperature of the inner channel, T2 is the outer wall temperature of the inner channel, λ f is the thermal conductivity of the injection pipe, q is the heat, α is the convective heat transfer coefficient, α1 is the convective heat transfer coefficient of the internal channel, α2 is the convective heat transfer coefficient of the external channel, v, λ, Re, Pr, Nu are the kinematic viscosities (m 2 / s), gas thermal conductivity (W / (m·K)), Reynolds number, Prandtl number, Nusselt number, V are V' and V", respectively, and D are D1 and D2, respectively, to calculate α1 and α2 accordingly.

[0025] The beneficial effects of the present invention are:

[0026] The present invention provides a device for injecting reducing gas into a blast furnace and a design method thereof, which can deliver reducing gas to the center of the blast furnace, so that the reducing gas can contact more ores, thereby improving the reduction effect, increasing the utilization rate, and reducing direct carbon consumption.

[0027] Secondly, the design method of the device for injecting reducing gas into a blast furnace in the present invention designs the inner diameter of the injection pipe and the material of the injection pipe according to the injection amount and injection temperature of the reducing gas, so that the flow velocity V' in the internal channel of the injection pipe for injecting hot gas is less than the economic flow velocity V0, and the operating temperature is within the allowable operating temperature range, thereby reducing the cost of reducing gas injection and extending the service life of the device.

[0028] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 A schematic diagram of the arrangement of a device for injecting reducing gas into a blast furnace in an embodiment;

[0031] Figure 2 Schematic diagram of the size relationship of the injection pipe in the embodiment.

[0032] Figure numerals: 1 - blast furnace shell; 2 - soft melting zone; 3 - flange; 4 - support frame; 5 - injection pipe; 6 - gas outlet. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Before describing the embodiments of the present invention in detail, the application environment of the present invention will be described first. The technology of the present invention is mainly applied to blast furnaces, especially in the field of blast furnace injection. The present invention focuses on solving the technical problem that reducing gas cannot reach the center of the blast furnace.

[0037] A device for injecting reducing gas into a blast furnace, comprising an injection pipeline 5 and a support frame 4 for supporting the injection pipeline 5, wherein both ends of the injection pipeline 5 are respectively a gas inlet and a gas outlet 6;

[0038] The key point of this embodiment is that the blowing pipeline 5 is a double-tube design, and its inner channel is a hot gas channel, and the outer channel is a cold gas channel; the gas outlet 6 is located above the soft melting zone 2 in the blast furnace.

[0039] Preferably, the gas outlet 6 is located 1 to 10 m above the top of the soft melting zone 2 .

[0040] Specifically, the material of the spray pipe 5 is carbon steel, heat-resistant stainless steel or alloy steel, and a layer of wear-resistant alloy or wear-resistant spray coating is provided on the outer side of the spray pipe 5 .

[0041] The injection pipe 5 enters the blast furnace from the blast furnace top or the blast furnace shell 1 and reaches the center of the blast furnace, so that the reducing gas therein participates in the reduction process of the ore in the center of the blast furnace. The support frame 4 is fixedly installed on the outside of the blast furnace shell 1 and is connected to the part of the injection pipe 5 located outside the blast furnace, thereby supporting the injection pipe 5.

[0042] Preferably, a flange 3 is provided at the gas inlet of the injection pipeline 5 to connect to an external pipeline.

[0043] Based on the above-mentioned device for injecting reducing gas into a blast furnace, this embodiment further provides a design method for injecting reducing gas into a blast furnace, comprising the following steps:

[0044] S1: Obtain the hot gas flow Q' and its injection temperature T' and injection pressure P', the cold gas flow Q' and its injection temperature T' and injection pressure P' in the blast furnace injection reducing gas (in the injection pipeline 5);

[0045] S2: Select the inner diameter D1 of the inner channel of the blowing pipe 5, the inner diameter D2 of the outer channel (i.e. the outer diameter of the inner channel) and the material of the blowing pipe;

[0046] S3: Calculate the flow velocities V' and V" of the inner channel and the outer channel in the spray pipe 5, the convection heat transfer coefficient α, and the inner wall temperature T1 and the outer wall temperature T2 of the inner channel in the spray pipe according to the above parameters;

[0047] S4: Determine whether the flow velocity V' is less than the economic flow velocity V0, which is determined by the equipment capacity and comprehensive cost, generally 40-75 m / s, and whether the inner wall temperature T1 of the internal channel is less than the allowable use temperature T0 of the injection pipe material, which is determined by the characteristics of the injection pipe material itself;

[0048] S5: If the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0, it can be determined that the inner diameters D1 and D2 of the spray pipe 5 and the material of the spray pipe 5 meet the design standards;

[0049] If the flow rate V' is not less than the economic flow rate V0, or the temperature T1 is not less than the temperature T0, return to step S2 to reselect the inner diameters D1 and D2 of the blowing pipe 5 and the material of the blowing pipe 5 so that the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0.

[0050] The calculation formula for flow rates V' and V" is:

[0051]

[0052] The calculation formula for temperature T is:

[0053]

[0054] The calculation formula of heat q is:

[0055]

[0056] The calculation formula of the convection heat transfer coefficient α is:

[0057]

[0058] Nu=0.023Re 0.8 Pr 0.4

[0059]

[0060] Where: f is the thermal conductivity of the injection pipe, α1 is the convection heat transfer coefficient of the internal channel, α2 is the convection heat transfer coefficient of the external channel, v, λ, Re, Pr, Nu are the kinematic viscosities (m 2 / s), gas thermal conductivity (W / (m·K)), Reynolds number, Prandtl number, Nusselt number, V is V' and V", respectively, and D is D1 and D2, respectively.

[0061] To further illustrate the device and design method, a specific embodiment is used below to further illustrate, but the device and method are not limited to the following embodiment.

[0062] like Figure 1 and Figure 2 As shown, a device for injecting reducing gas into a blast furnace is composed of a flange 3, a support frame 4, and an injection pipe 5. The device is located on the upper part of the blast furnace body to avoid damage to it by the soft melting zone, wherein the injection pipe 5 is made of austenitic stainless steel and adopts a double-channel design, wherein the inner channel is a hot gas channel with a hot gas temperature of 950°C and a pressure of 0.5MPa, and the outer channel is a cold gas channel with a temperature of 30°C and a pressure of 0.5MPa. The cold gas can reduce the temperature of the injection pipe 5, so that it can work stably for a long time inside the blast furnace, wherein the economic flow rate V0=50m / s, and the injection pipe material allows the use temperature T0=600°C. The support frame 4 is welded to the blast furnace shell 1 to play a role in stably supporting the injection pipe shell 5. The design method includes the following steps:

[0063] S1: Get the flow rate of hot gas injected into the blast furnace Q' = 50000Nm 3 / h, injection temperature T' = 950 ° C, injection pressure P' = 0.5 MPa, injection cold gas flow rate Q" = 30000 Nm 3 / h, spraying temperature T" = 30 ° C, spraying pressure P" = 0.5 MPa;

[0064] S2: Select the inner diameter of the spray pipe D1 = 610mm and D2 = 630mm, and the material of the spray pipe is austenitic stainless steel;

[0065] S3: The calculated flow rate V'=35.87m / s, V"=21.31m / s, convection heat transfer coefficient α1=74.59, α2=49.25, the inner wall temperature T1=579.11℃ and the outer wall temperature T2=573.87℃ of the inner channel in the spray pipe, the flow rate V'=35.87m / s is less than the economic flow rate V0=50m / s, the inner wall temperature T1=579.11℃ of the spray pipe is less than the allowable use temperature T0=600℃ of the spray pipe material;

[0066] It can be seen that the inner diameter of the spray pipe and the spray pipe material selected in this embodiment meet the design standards, and the design is completed; if V' is not less than the economic flow rate V0, or the inner wall temperature T1 of the internal channel in the spray pipe is not less than the allowable use temperature T0 of the spray pipe material, it is necessary to reselect the inner diameter of the spray pipe and the spray pipe material so that V' is less than the economic flow rate V0, and the inner wall temperature T1 of the internal channel in the spray pipe is less than the allowable use temperature T0 of the spray pipe material.

[0067] The device for injecting reducing gas into a blast furnace and the design method thereof can deliver reducing gas to the center of the blast furnace so that the reducing gas can contact more ores, thereby improving the reduction effect, increasing the utilization rate, reducing the direct carbon consumption of the blast furnace, and achieving energy saving and consumption reduction of the blast furnace.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A device for injecting reducing gas into a blast furnace, characterized in that: It includes a blowing pipeline for delivering reducing gas from the top or body of the blast furnace to the center of the blast furnace. The blowing pipeline is of double-tube design, and the inner channel in the blowing pipeline is a hot gas channel, and the outer channel is a cold gas channel.

2. The device for injecting reducing gas into a blast furnace according to claim 1, characterized in that: The two ends of the blowing pipeline are respectively a gas inlet and a gas outlet, and the gas outlet is located above the soft melting zone in the blast furnace.

3. The device for injecting reducing gas into a blast furnace according to claim 2, characterized in that: A flange is provided at the gas inlet of the injection pipeline to connect with an external pipeline.

4. The device for injecting reducing gas into a blast furnace according to claim 2, characterized in that: The gas outlet is located 1 to 10 meters above the soft melting zone.

5. The device for injecting reducing gas into a blast furnace according to claim 1, characterized in that: It also includes a support frame, which is fixedly installed on the outside of the blast furnace shell and connected to the part of the injection pipeline located outside the blast furnace to support the injection pipeline.

6. The device for injecting reducing gas into a blast furnace according to claim 1, characterized in that: The material of the spray pipe is carbon steel, heat-resistant stainless steel or alloy steel.

7. The device for injecting reducing gas into a blast furnace according to claim 1, characterized in that: A layer of wear-resistant alloy or wear-resistant spray coating is provided on the outer side of the spray pipe.

8. A method for designing a device for injecting reducing gas into a blast furnace, characterized in that: The design of the device for injecting reducing gas into a blast furnace according to any one of claims 1 to 7 comprises the following steps: S1: Obtain the hot gas flow Q' and its injection temperature T' and injection pressure P', the cold gas flow Q'' and its injection temperature T'' and injection pressure P'' in the injection pipeline; S2: Select the inner diameter D1 of the inner channel in the blowing pipe, the inner diameter D2 of the outer channel and the material of the blowing pipe; S3: Calculate the flow velocity V' of the internal channel in the spray pipe and the inner wall temperature T1 of the internal channel according to the above parameters; S4: Determine whether the flow rate V' is less than the economic flow rate V0, and whether the temperature T1 is less than the allowable use temperature T0 of the injection pipe material; S5: If the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0, it can be determined that the inner diameter D1 and the inner diameter D2 and the material of the injection pipe meet the design standards; If the flow rate V' is not less than the economic flow rate V0, or the temperature T1 is not less than the temperature T0, return to step S2 to reselect the inner diameter D1 and the inner diameter D2 and the material of the blowing pipe so that the flow rate V' is less than the economic flow rate V0, and the temperature T1 is less than the temperature T0.

9. The design method of the device for injecting reducing gas into a blast furnace according to claim 8, characterized in that: The calculation method of the flow velocity V' is as follows: Now=0.023Re 0.8 Per 0.4 Where: V' is the flow rate of the inner channel, V" is the flow rate of the outer channel, T1 is the inner wall temperature of the inner channel, T2 is the outer wall temperature of the inner channel, λ f is the thermal conductivity of the injection pipe, q is the heat, α is the convective heat transfer coefficient, α1 is the convective heat transfer coefficient of the internal channel, α2 is the convective heat transfer coefficient of the external channel, v, λ, Re, Pr, Nu are the kinematic viscosities (m 2 / s), gas thermal conductivity (W / (m·K)), Reynolds number, Prandtl number, Nusselt number, V are V' and V", respectively, and D are D1 and D2, respectively, to calculate α1 and α2 accordingly.

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