A method for determining the position of a residual iron port of a blast furnace residual iron discharge hearth

Abstract

The present application relates to a kind of blast furnace residual iron furnace residual iron mouth position determination method, comprising: the determination of furnace residual iron mouth elevation position and the determination of furnace residual iron mouth circumferential position and the like steps.The blast furnace residual iron furnace residual iron mouth position determination method provided by the present application, by the erosion rate of furnace refractory, blast furnace refractory thermal conductivity coefficient and blast furnace running time model, determine the thinnest part of refractory, i.e.elevation (i.e.latitude), by circumferential position model, again in combination with the convenience of residual iron and furnace cooling wall temperature detection, determine specific cooling wall (i.e.latitude), compared with prior art, it is a more scientific method.

Description

Technical Field

[0001] This invention relates to a method for determining the location of the residual iron outlet in the hearth of a blast furnace, belonging to the field of metal smelting technology. Background Technology

[0002] Blast furnace residual iron discharge refers to the process of draining the last molten iron from the blast furnace hearth during a mid-term shutdown for maintenance of the internal refractory materials and water cooling system, or after the blast furnace has been shut down. This is known in the industry as "residual iron discharge." In normal smelting, the molten iron produced by oxidation-reduction in the blast furnace is released through the tap. The tap is usually about 3 meters away from the bottom of the hearth. This portion of molten iron accumulated in the blast furnace protects the ceramic lining at the bottom of the hearth from temperature changes and erosion, thus protecting the hearth.

[0003] When overhauling the hearth or shutting down the blast furnace, the ideal method is to release as much of the molten iron as possible to ensure proper inspection, repair, or removal of the hearth bottom to prevent corrosion.

[0004] Generally speaking, it is best to set the taphole at the lowest position to ensure that all the molten iron in the dead iron layer inside the hearth can be released. However, in actual operation, there is a physical phenomenon: during normal tapping of iron in the blast furnace, there is a turbulent flow process in the molten iron in the dead iron layer. That is, when the blast furnace is tapping iron normally, the upper layer of molten iron flows out through the taphole, but the molten iron accumulated in the blast furnace within a range of about 3 meters from the taphole to the ceramic pad layer at the bottom of the hearth cannot flow out. However, based on practical experience, during normal tapping, this part of the molten iron will flow and scour the hearth and ceramic pad layer within this 3-meter range. This phenomenon is greatly affected by the blast furnace tapping rate, air pressure, and blast furnace tapping system. The erosion of the bottom of the hearth is irregular, that is, the hearth has changed from the original standard and regular "U" shape to an irregular shape.

[0005] Existing technical solutions mostly involve measuring the temperature of the furnace shell surface and determining the elevation of the residual iron tapping location using temperature curves; finally, measuring the surface temperature of the carbon bricks to accurately locate the residual iron tapping location; after removing the cooling wall and furnace shell for discharging residual iron, using a grid-like scale and an infrared imaging thermometer to measure the temperature of the exposed carbon brick surface, identifying locations with drastic temperature changes, and then accurately locating the residual iron tapping location; a hole is then drilled at this location. However, considering the irregular shape of the furnace hearth bottom, the opening location in existing technical solutions is not accurate, and the amount of work required is enormous. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned technologies and provide a method for determining the most severe point of an irregularly shaped erosion model, thereby determining the location of the residual iron tap.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a method for determining the position of the residual iron outlet in the hearth of a blast furnace, comprising the following steps:

[0008] Determining the elevation of the residual iron taphole in the hearth:

[0009] The governing equations are calculated using a two-dimensional steady-state heat transfer model as follows: In the formula, t is the hot surface temperature of the refractory material of the blast furnace hearth, k is the thermal conductivity of the refractory material of the hearth, and Z and r are the coordinate values ​​of the thermocouples on the side wall of the blast furnace hearth.

[0010] The heat transfer equation for the one-dimensional steady-state heat transfer calculation of the furnace hearth refractory is as follows: In the formula, q represents the thermocouple reading on the sidewall of the blast furnace hearth, and q represents the heat flux density of the refractory material in the blast furnace hearth.

[0011] The erosion rate μ of the blast furnace hearth refractory material satisfies the following functional relationship with the maximum value T among the following factors: thermal conductivity k, blast furnace operating time a, output Q, and hot surface temperature T of the hearth refractory material: The residual thickness of the furnace hearth refractory material is d = (1-μ)d0; where d0 is the original thickness of the furnace hearth refractory material.

[0012] Based on the above formula, by substituting the coordinate values ​​and measured values ​​of each thermocouple on the sidewall of the blast furnace hearth into the calculation, the residual thickness of the hearth refractory at each location is obtained. The location with the deepest erosion of the refractory at the bottom of the furnace, that is, the thinnest part of the hearth refractory, is selected as the location for determining the elevation of the residual iron taphole.

[0013] Determining the circumferential position of the residual iron taphole in the hearth:

[0014] The thickness of the carbon bricks on the sidewall of the furnace hearth was calculated by deriving the relationship between the one-dimensional steady-state heat transfer equation and the cooling wall water temperature.

[0015] Under one-dimensional steady-state heat conduction, the relationship between heat flux density and temperature gradient is as follows: In the formula, T1 is the temperature at a certain point in the cooling wall water pipe, L is the thickness of the carbon brick hot surface of the hearth sidewall of the blast furnace to the cooling wall water pipe; K is the thermal conductivity of the hearth sidewall, from which the value of L / K is calculated.

[0016] The thermal conductivity K of the furnace hearth sidewall is given by the equation: In the formula, λ1 is the thermal conductivity of the cooling wall; λ2 is the thermal conductivity of the ramming material; λ3 is the thermal conductivity of the carbon brick; d1 is the distance from the cooling wall water pipe to the hot surface of the cooling wall; d2 is the thickness of the ramming material; d3 is the residual thickness of the carbon brick; the value of K is calculated from this, and then the value of L is obtained; then the value of d3 is calculated according to the formula L=d1+d2+d3.

[0017] By substituting the temperature values ​​of various locations in the cooling wall water pipes into T1, the thinnest part of the carbon brick on the side wall of the furnace hearth is identified, which is then used as the circumferential position of the residual iron tap.

[0018] The method for determining the location of the residual iron outlet in the hearth of a blast furnace, provided by this invention, determines the elevation (i.e., longitude) of the thinnest part of the refractory material by using the erosion rate of the hearth refractory, the thermal conductivity of the blast furnace refractory, and a blast furnace operating time model. By using a circumferential position model, combined with the convenience of residual iron discharge and the temperature detection of the hearth cooling wall, the specific cooling wall (i.e., latitude) is determined. Compared with the prior art, this is a more scientific method. Detailed Implementation

[0019] Example: The method for determining the location of the residual iron tapping hole in the hearth of a blast furnace in this example includes the following steps:

[0020] 1. Determining the elevation of the residual iron tap in the hearth:

[0021] Heat transfer in the hearth and bottom of a blast furnace can be considered a heat conduction problem. Under constant blast furnace production conditions such as furnace temperature and cooling regime, blast furnace smelting production is stable. To simplify the calculation, we assume the heat transfer process is a steady-state process with no internal heat source; when defining the thermal performance parameters of each material, we assume the thermal conductivity of the refractory material used in the hearth and bottom, the thermal conductivity of the cooling wall, and the thermal conductivity of the furnace shell are constants; we assume the molten iron temperature and the ambient temperature outside the furnace shell are uniformly distributed on the contact surface. The calculation only considers the effect of heat transfer on erosion, neglecting the slag-iron layer thickness and its actual bonding condition and bonding capacity with the hearth and bottom; we ignore the relationship between heat transfer and time and internal heat sources. Considering the axisymmetry of the hearth, a two-dimensional steady-state heat transfer model is used for calculation, and its governing equations are as follows: In the formula, t is the hot surface temperature of the blast furnace hearth refractory (in °C), and k is the thermal conductivity of the hearth refractory (in W / m²). -1 ℃ -1 Z and r are the coordinate values ​​of the thermocouples on the sidewall of the blast furnace hearth (in meters).

[0022] Under blast furnace conditions, the outer shell and the inner walls of the cooling wall water pipes are subject to third-type boundary conditions, while the inner lining hot surface is subject to first-type boundary conditions. Due to the symmetry of the hearth and the directionality of heat flow, the upper edge and centerline of the hearth wall are considered adiabatic boundaries. The interior of the ceramic pad or cast refractory at the furnace bottom, and the interior of the carbon bricks in the hearth, can be calculated using one-dimensional steady-state heat transfer. The heat transfer equation for the one-dimensional steady-state heat transfer of the hearth refractory is: In the formula, q represents the thermocouple reading on the sidewall of the blast furnace hearth (in °C), and q represents the heat flux density (w / m²) of the refractory material in the blast furnace hearth.

[0023] The erosion rate μ (in %) of the blast furnace hearth refractory material satisfies the following functional relationship with the maximum value T among the following factors: thermal conductivity k, blast furnace operating time a (in years), output Q (in tons), and hot surface temperature T of the hearth refractory material: The residual thickness of the furnace hearth refractory material is d = (1-μ)d0; where d0 is the original thickness of the furnace hearth refractory material (in meters).

[0024] Based on the above formula, by substituting the coordinate values ​​and measured values ​​of each thermocouple on the sidewall of the blast furnace hearth into the calculation, the residual thickness of the hearth refractory at each location is obtained. The location with the deepest erosion of the refractory at the bottom of the furnace, that is, the thinnest part of the hearth refractory, is selected as the location for determining the elevation of the residual iron taphole.

[0025] 2. Determining the circumferential position of the residual iron taphole in the hearth:

[0026] In the radial direction of a blast furnace, it consists of the furnace shell, pressurized charge, cooling walls, ramming mix, sidewall carbon bricks, and sidewall ceramic pads. For blast furnaces that have been in operation for several years, the sidewall ceramic pads have been completely eroded, and some of the sidewall carbon bricks have also been eroded. Therefore, the thickness of the carbon bricks on the hearth sidewall can be calculated by deriving the relationship between the one-dimensional steady-state heat transfer equation and the cooling wall water temperature.

[0027] Under one-dimensional steady-state heat conduction, the relationship between heat flux density and temperature gradient is as follows: This formula is the standard formula, where q is the heat flux density, J / (s·m). 2 λ is the thermal conductivity of the material, W / (m·K); T is the temperature field distribution function, K; X is the length in the heat conduction direction, m. The negative sign indicates that heat transfer is opposite to the temperature gradient. Under blast furnace conditions, due to the continuity of heat transfer and relatively small temperature changes, It can be considered as In a normally operating blast furnace, the temperature of the solidified blast hearth is 1150℃. Therefore, it can be... Convert to: In the formula, T1 is the temperature at a certain point in the cooling wall water pipe (in °C), L is the thickness of the carbon brick hot surface of the blast furnace hearth sidewall to the cooling wall water pipe (in m), and K is the thermal conductivity of the hearth sidewall. The value of L / K is calculated from this.

[0028] The hearth sidewall comprises a cooling wall, rammed earth, and carbon bricks. The thickness of the cooling wall and rammed earth remains constant; the only variable is the remaining thickness of the carbon bricks. According to the multi-layer thermal conductivity model, the total thermal conductivity of the hearth sidewall is K, calculated using the following formula: In the formula, λ1 is the thermal conductivity of the cooling wall; λ2 is the thermal conductivity of the ramming material; λ3 is the thermal conductivity of the carbon brick; d1 is the distance from the cooling wall water pipe to the hot surface of the cooling wall; d2 is the thickness of the ramming material; d3 is the residual thickness of the carbon brick; the value of K is calculated from this, and then the value of L is obtained; then the value of d3 is calculated according to the formula L=d1+d2+d3.

[0029] By substituting the temperature values ​​of various locations in the cooling wall water pipes into T1, the thinnest part of the carbon brick on the side wall of the furnace hearth is identified, which is then used as the circumferential position of the residual iron tap.

[0030] This invention is not limited to the products described above. All technical solutions derived using equivalent substitutions fall within the scope of protection claimed by this invention.

Claims

1. A method for determining the location of the residual iron outlet in the hearth of a blast furnace, characterized in that, Includes the following steps: Determining the elevation of the residual iron taphole in the hearth: The governing equations are calculated using a two-dimensional steady-state heat transfer model as follows: In the formula, t is the hot surface temperature of the refractory material of the blast furnace hearth, k is the thermal conductivity of the refractory material of the hearth, and Z and r are the coordinate values ​​of the thermocouples on the side wall of the blast furnace hearth. The heat transfer equation for the one-dimensional steady-state heat transfer calculation of the furnace hearth refractory is as follows: In the formula, q represents the thermocouple reading on the sidewall of the blast furnace hearth, and q represents the heat flux density of the refractory material in the blast furnace hearth. The erosion rate μ of the blast furnace hearth refractory material satisfies the following functional relationship with the maximum value T among the following factors: thermal conductivity k, blast furnace operating time a, output Q, and hot surface temperature T of the hearth refractory material: The residual thickness of the furnace hearth refractory material is d = (1-μ)d0; where d0 is the original thickness of the furnace hearth refractory material. Based on the above formula, by substituting the coordinate values ​​and measured values ​​of each thermocouple on the sidewall of the blast furnace hearth into the calculation, the residual thickness of the hearth refractory at each location is obtained. The location with the deepest erosion of the refractory at the bottom of the furnace, that is, the thinnest part of the hearth refractory, is selected as the location for determining the elevation of the residual iron taphole. Determining the circumferential position of the residual iron taphole in the hearth: The thickness of the carbon bricks on the sidewall of the furnace hearth was calculated by deriving the relationship between the one-dimensional steady-state heat transfer equation and the cooling wall water temperature. Under one-dimensional steady-state heat conduction, the relationship between heat flux density and temperature gradient is as follows: In the formula, T1 is the temperature at a certain point in the cooling wall water pipe, L is the thickness of the carbon brick hot surface of the hearth sidewall of the blast furnace to the cooling wall water pipe; K is the thermal conductivity of the hearth sidewall, from which the value of L / L is calculated. The thermal conductivity K of the furnace hearth sidewall is given by the equation: In the formula, λ1 is the thermal conductivity of the cooling wall; λ2 is the thermal conductivity of the ramming material; λ3 is the thermal conductivity of the carbon brick; d1 is the distance from the cooling wall water pipe to the hot surface of the cooling wall; d2 is the thickness of the ramming material; d3 is the residual thickness of the carbon brick; the value of K is calculated from this, and then the value of L is obtained; then the value of d3 is calculated according to the formula L=d1+d2+d3. By substituting the temperature values ​​of various locations in the cooling wall water pipes into T1, the thinnest part of the carbon brick on the side wall of the furnace hearth is identified, which is then used as the circumferential position of the residual iron tap.

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