Device and method for testing conductivity of solid direct reduced iron

Abstract

The invention discloses a device and a method for testing the conductivity of solid direct reduced iron, and relates to the technical field of the conductivity of reduced iron. The invention designs a device which can determine the length and the sectional area when a plurality of DRIs are stacked so as to test the conductivity of the stacked DRIs. The conductivity of stacked DRI can be conveniently tested, the diameter of the cylinder device can be adjusted (namely, the sectional area can be adjusted), the height of the device and the distance between conductor sheets at the upper end and the lower end can also be adjusted, and the requirements for filling DRI of different granularities and numbers can be met; according to the invention, the conductivity of the stacked DRI at different temperatures can be conveniently tested, the device is put into a heating furnace, the temperature is raised to a target temperature, and the conductivity of the directly reduced iron at different temperatures and in a stacking state is tested. A temperature rise system can also be set, and the change curve of the DRI under different temperature rise system conditions is obtained by recording the change of the current and the voltage in real time.

Description

Technical Field

[0001] The invention relates to the technical field of reduced iron conductivity, in particular to a device and method for testing the conductivity of solid-state direct reduced iron. Background Art

[0002] The hydrogen-based direct reduction vertical furnace process does not require coking, sintering, ironmaking and other links, and can control carbon emissions from the source. Compared with blast furnace hydrogen-rich reduction, the carbon reduction rate can reach more than 50%, and the emission reduction potential is relatively large. Direct reduced iron (DRI) is a high-quality charge for smelting high-quality steel. It can be added as a "diluent" to electric furnace smelting with scrap steel as the main raw material. The raw materials of the global mainstream electric furnace steelmaking process are: scrap steel (50%-70%) + DRI (30% + 50%). At the same time, vanadium-titanium direct reduction iron electric furnace smelting has the ability to provide chemical energy and heat for green hydrogen-green electricity through full process transformation, and is the most suitable process for smelting vanadium-titanium ore. Electric furnace smelting is the process of using electric energy to heat electrodes and charge to high temperatures, so as to melt, decompose, and reduce the charge to achieve metal smelting. In the electric furnace, electric energy is input into the furnace through electrodes, and an arc is generated between the electrodes and the charge. The high temperature of the arc is used to heat and melt the charge. Electrical conductivity is a physical quantity that measures the electrical conductivity of a material. For an electric furnace, the electrical conductivity of the charge directly affects the efficiency of converting electrical energy into thermal energy and the uniformity of the temperature in the furnace. If the electrical conductivity of the charge is inconsistent, it may lead to uneven temperature distribution in the furnace, thus affecting the quality and production efficiency of the product. In addition, charge with low electrical conductivity helps to reduce power loss, improve energy efficiency and reduce production costs. Therefore, testing the electrical conductivity of the accumulated solid direct reduced iron is essential for electric furnace steelmaking.

[0003] Conductivity is a parameter used to describe the ease of charge flow in a substance. The calculation formula is σ=GL / A=IL / (AU), where σ represents conductivity; G represents conductance; L represents conductor length; A represents conductor cross-sectional area; I represents current; and U represents voltage. The most commonly used test methods for solid conductivity include direct measurement and four-wire method (four-terminal method). Among them, the direct measurement method is to make the material to be tested into electrodes of a certain shape and size, and calculate the conductivity by measuring the resistance value between the electrodes. During the test, the material to be tested needs to be processed into electrodes of a certain shape and size, usually in the form of round or rectangular sheets. The shape of DRI is approximately spherical, irregular in shape, and has a large surface roughness, so the direct measurement method cannot be used. The four-wire method is mainly used to accurately measure low-value resistors. The principle is that a constant current power supply supplies current to the low-value resistor to be measured, and the voltage is measured through two voltage leads to form a potential difference on the low-value resistor to be measured by the current supplied by the constant current power supply, and then the conductivity is calculated by the resistance value. Testing the conductivity of solid DRI using the four-wire method requires designing a device that can determine the length and cross-sectional area of ​​multiple DRI stacks.

[0004] Existing four-wire method test devices usually use a fixture to fix the sample, but for the stacked DRI samples, the fixture cannot be used directly. It is necessary to design a device that can determine the length and cross-sectional area of ​​multiple DRI stacked.

[0005] Therefore, a new solution to the above problems needs to be proposed. Summary of the invention

[0006] The object of the present invention is to provide a device and method for testing the electrical conductivity of solid-state direct-reduced iron, so as to solve the technical problems raised in the background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a device for testing the electrical conductivity of solid direct reduced iron, comprising a first wire, a second wire, a third wire, a fourth wire, a cylinder and a conductor sheet. The inner wall of the cylinder is provided with a plurality of conductor sheets, and the inner side of the cylinder is provided with the first wire, the second wire, the third wire and the fourth wire in sequence.

[0008] Furthermore, the cylinder is an open cylinder at the top, and the material of the cylinder is a high temperature resistant insulator.

[0009] Furthermore, the conductor sheets are inlaid on the side wall of the cylinder, and the conductor sheets are made of high temperature resistant material.

[0010] Furthermore, the first wire and the fourth wire are connected to an ammeter.

[0011] Furthermore, the second wire and the third wire are connected to a voltmeter.

[0012] A method for testing the electrical conductivity of solid-state direct-reduced iron, used in the above content, at least comprises the following steps:

[0013] S1: Load solid direct reduced iron into a cylinder with a known diameter, and calculate the cross-sectional area of ​​the cylinder based on the diameter, recorded as A;

[0014] S2: The distance between the conductor sheets at the upper and lower ends is recorded as L;

[0015] S3: Connect the first wire and the fourth wire to the ammeter, connect the second wire and the third wire to the voltmeter, and after the constant current power supply supplies current to the device, record the values ​​of the ammeter and the voltmeter, which are recorded as I and U respectively;

[0016] S4: Calculate the conductivity of the direct reduced iron in the stacked state according to the formula σ=GL / A=IL / (AU);

[0017] S5: placing the device into a heating furnace, heating it to a target temperature, and testing the conductivity of the direct reduced iron in a stacked state at different temperatures.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention designs a device that can determine the length and cross-sectional area of ​​multiple DRI stacks, and then test the conductivity of the stacked DRI.

[0020] 2. The present invention is convenient for testing the conductivity of stacked DRI. The diameter of the cylindrical device is adjustable (i.e., the cross-sectional area is adjustable), and the height of the device and the spacing between the conductor sheets at the upper and lower ends are also adjustable, which can meet the needs of loading DRI of different particle sizes and numbers.

[0021] 3. The present invention is convenient for testing the conductivity of DRI piled at different temperatures. The device is placed in a heating furnace, heated to the target temperature, and the conductivity of direct reduced iron in a piled state at different temperatures is tested. A heating system can also be set to obtain the change curve of DRI under different heating system conditions by recording the changes in current and voltage in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 The structure diagram of the device for testing the electrical conductivity of solid-state direct-reduced iron according to the present invention;

[0024] Figure 2 This is a schematic diagram of the test principle of the electrical conductivity of solid direct reduced iron according to the present invention;

[0025] Figure 3 It is a cross-sectional view of the electrical conductivity testing device of solid direct reduced iron of the present invention;

[0026] Figure 4 It is a schematic diagram of the conductivity of solid direct reduced iron in a stacked state at room temperature according to the present invention;

[0027] Figure 5 It is a schematic diagram of the electrical conductivity of solid direct reduced iron in a stacked state under isothermal conditions according to the present invention.

[0028] In the figure: 1, first wire; 2, second wire; 3, third wire; 4, fourth wire; 5, cylinder; 6, conductor sheet. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] Embodiment 1:

[0031] A device for testing the electrical conductivity of solid direct reduced iron comprises a first wire 1, a second wire 2, a third wire 3, a fourth wire 4, a cylinder 5 and a conductor sheet 6. The inner wall of the cylinder 5 is provided with a plurality of conductor sheets 6, and the inner side of the cylinder 5 is provided with the first wire 1, the second wire 2, the third wire 3 and the fourth wire 4 in sequence.

[0032] The cylinder 5 is an open cylinder at the top, and the material of the cylinder 5 is a high temperature resistant insulator.

[0033] A total of four conductive sheets 6 are embedded on the side wall of the cylinder 5 , and the conductive sheets 6 are made of high temperature resistant material.

[0034] The first wire 1 and the fourth wire 4 are connected to an ammeter.

[0035] The second wire 2 and the third wire 3 are connected to a voltmeter.

[0036] Embodiment 2:

[0037] This embodiment proposes a method for testing the electrical conductivity of solid-state direct reduced iron based on the above embodiment 1;

[0038] A method for testing the electrical conductivity of solid-state direct reduced iron comprises at least the following steps:

[0039] S1: Solid direct reduced iron is loaded into a cylinder 5 with a known diameter, as shown in the cross-sectional view. Figure 3 . Calculate the cross-sectional area of ​​the cylinder based on the diameter, recorded as A;

[0040] S2: Figure 1 b and Figure 1 In d, the distance between the conductor sheets 6 at the upper and lower ends is recorded as L;

[0041] S3: Connect the first wire 1 and the fourth wire 4 to the ammeter, connect the second wire 2 and the third wire 3 to the voltmeter, and after the constant current power supply supplies current to the device, record the values ​​of the ammeter and the voltmeter, which are recorded as I and U respectively;

[0042] S4: Calculate the conductivity of the direct reduced iron in the stacked state according to the formula σ=GL / A=IL / (AU);

[0043] S5: placing the device into a heating furnace, heating it to a target temperature, and testing the conductivity of the direct reduced iron in a stacked state at different temperatures.

[0044] The diameter of the cylinder 5 is adjustable, that is, the cross-sectional area is adjustable, and the height of the device and the spacing between the upper and lower conductive sheets 6 are also adjustable, which can meet the needs of loading DRI of different particle sizes and numbers.

[0045] The conductivity of DRI stacked at different temperatures was tested.

[0046] Place the device in a heating furnace, heat it to the target temperature, and test the conductivity of direct reduced iron in a stacked state at different temperatures. You can also set a heating system, and obtain the DRI change curve under different heating system conditions by recording the changes in current and voltage in real time.

[0047] Based on the above two embodiments, the following experimental cases are further proposed:

[0048] First experimental case:

[0049] The conductivity of solid direct reduced iron (about 12.5 mm in diameter) in a stacked state was tested at room temperature using a device with a cylinder inner diameter of 45 mm. The current and voltage values ​​were recorded by a computer, and the corresponding conductivity values ​​were obtained. The results are shown in Figure 4 In this experiment, the shortest time interval that can be achieved to record the current and voltage values ​​is 0.01s. Figure 4 It can be seen that the conductivity test value of solid direct reduced iron in a stacked state at room temperature is very stable.

[0050] Under isothermal conditions, the conductivity test of solid direct reduced iron in a stacked state is carried out in the following steps:

[0051] (1) Solid direct reduced iron is loaded into a cylinder with a known diameter. See the cross-sectional view. Figure 3 . Calculate the cross-sectional area of ​​the cylinder based on the diameter and record it as A.

[0052] (2) Figure 1 (b) and Figure 1 In (d), the distance between the conductor plates at the upper and lower ends is denoted by L.

[0053] (3) Place the cylinder in a heating furnace and introduce inert gas to prevent oxidation of the direct reduced iron during the heating process. Heat to the target temperature and keep it warm for a period of time until the temperature does not change.

[0054] (4) The first wire 1 and the fourth wire 4 are connected to an ammeter, and the second wire 2 and the third wire 3 are connected to a voltmeter. After the constant current power supply supplies current to the device, the values ​​of the ammeter and the voltmeter are recorded and recorded as I and U respectively.

[0055] (5) The electrical conductivity of direct reduced iron in a stacked state under isothermal conditions is calculated according to the formula σ=GL / A=IL / (AU).

[0056] Second experimental case:

[0057] The conductivity of solid direct reduced iron (about 12.5 mm in diameter) in a stacked state was tested under isothermal conditions using a device with a cylinder inner diameter of 45 mm. The current and voltage values ​​were recorded by a computer, and the corresponding conductivity values ​​were obtained. The results are shown in Figure 5 .from Figure 5 It can be seen that when the temperature rises from 200℃ to 600℃, the conductivity test value of solid direct reduced iron in the stacking state under isothermal conditions decreases with the increase of temperature. The reason is that the metallic iron content in direct reduced iron is high, and the resistance of metal generally increases with the increase of temperature. When the resistance increases, the conductivity decreases.

[0058] The specific steps for the conductivity test of solid direct reduced iron in a stacked state under variable temperature conditions are as follows:

[0059] (1) Solid direct reduced iron is loaded into a cylinder with a known diameter. See the cross-sectional view. Figure 3 . Calculate the cross-sectional area of ​​the cylinder based on the diameter and record it as A.

[0060] (2) Figure 1 (b) and Figure 1 In (d), the distance between the conductor plates at the upper and lower ends is denoted by L.

[0061] (3) Place the cylinder in a heating furnace and introduce inert gas to prevent oxidation of the direct reduced iron during the heating process. Set the temperature regime by changing the heating or cooling rate.

[0062] (4) The first wire 1 and the fourth wire 4 are connected to an ammeter, and the second wire 2 and the third wire 3 are connected to a voltmeter. After the constant current power supply supplies current to the device, the values ​​of the ammeter and the voltmeter are recorded and recorded as I and U respectively.

[0063] (5) The electrical conductivity of direct reduced iron in a stacked state under variable temperature conditions is calculated according to the formula σ=GL / A=IL / (AU).

[0064] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A device for testing the electrical conductivity of solid-state direct reduced iron, characterized in that: The invention comprises a first wire (1), a second wire (2), a third wire (3), a fourth wire (4), a cylinder (5) and a conductor sheet (6), wherein the inner wall of the cylinder (5) is provided with a plurality of conductor sheets (6), and the inner side of the cylinder (5) is provided with the first wire (1), the second wire (2), the third wire (3) and the fourth wire (4) in sequence.

2. A device for testing the electrical conductivity of solid-state direct reduced iron according to claim 1, characterized in that: The cylinder (5) is a cylinder with an open top, and the material of the cylinder (5) is a high-temperature resistant insulator.

3. A device for testing the electrical conductivity of solid-state direct reduced iron according to claim 1, characterized in that: A total of four conductive sheets (6) are embedded on the side wall of the cylinder (5), and the conductive sheets (6) are made of high temperature resistant material.

4. A device for testing the electrical conductivity of solid-state direct reduced iron according to claim 1, characterized in that: The first conductor (1) and the fourth conductor (4) are connected to an ammeter.

5. A device for testing the electrical conductivity of solid-state direct reduced iron according to claim 1, characterized in that: The second wire (2) and the third wire (3) are connected to a voltmeter.

6. A method for testing the electrical conductivity of solid-state direct-reduced iron, used in a device for testing the electrical conductivity of solid-state direct-reduced iron as claimed in any one of claims 1 to 3, characterized in that: At least the following steps are included: S1: Solid direct reduced iron is loaded into a cylinder (5) with a known diameter, and the cross-sectional area of ​​the cylinder is calculated according to the diameter, which is recorded as A; S2: The distance between the conductor sheets (6) at the upper and lower ends is recorded as L; S3: Connect the first wire (1) and the fourth wire (4) to an ammeter, connect the second wire (2) and the third wire (3) to a voltmeter, and after a constant current power supply supplies current to the device, record the values ​​of the ammeter and the voltmeter, which are recorded as I and U respectively; S4: Calculate the conductivity of the direct reduced iron in the stacked state according to the formula σ=GL / A=IL / (AU); S5: placing the device into a heating furnace, heating it to a target temperature, and testing the conductivity of the direct reduced iron in a stacked state at different temperatures.

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