A method for determining the reducibility of iron ore

Abstract

This application provides a method for determining the reducibility of iron ore, comprising the following steps: placing an iron ore sample in a sealed space filled with a protective gas and heating it to 500°C; continuously introducing a reducing gas into the sealed space while maintaining a pressure of 0.1-0.3 MPa, while simultaneously heating the iron ore sample to 1000°C and maintaining the temperature, continuously weighing the iron ore sample, and calculating the degree of reduction. Specifically, the continuous introduction of the reducing gas into the sealed space involves: introducing a first reducing gas for 1 hour, wherein the volume percentage of carbon monoxide in the first reducing gas is 23%-27%; subsequently introducing a second reducing gas for 1 hour, wherein the volume percentage of carbon monoxide in the second reducing gas is 29%-31%; and subsequently introducing a third reducing gas for 1 hour, wherein the volume percentage of carbon monoxide in the third reducing gas is 33%-37%. The experimental data collected by the iron ore reducibility determination method provided by this application are more consistent with actual smelting conditions and have guiding significance for actual production.

Description

Technical Field

[0001] This application relates to the field of iron ore testing, and in particular to a method for determining the reducibility of iron ore. Background Technology

[0002] Iron ore reducibility testing simulates the reduction process of iron-bearing furnace charge entering the lumpy zone of a blast furnace. Sinter with poor reducibility, when charged into the blast furnace, will affect the fuel ratio and output. Therefore, accurately measuring the reducibility of iron ore is crucial for controlling the conditions of blast furnace iron ore smelting to increase output.

[0003] The determination of the reduction performance of iron ore is generally carried out according to the test method specified in the national standard GB / T13241-2017. The national standard test method requires that the reduction temperature be maintained at 900℃ throughout the experiment, and the reducing gas composition be kept constant at 30% CO and 70% N2. However, the lumpy zone of the blast furnace is not at a constant temperature, and the CO composition is not always constant. Therefore, the test conditions specified in the national standard test method differ from actual smelting and cannot accurately reflect the true reduction process of iron ore in the blast furnace. Summary of the Invention

[0004] This application provides a method for determining the reducibility of iron ore, in order to solve the technical problem that current detection methods cannot accurately reflect the actual reduction process of sinter in the blast furnace.

[0005] This application provides a method for determining the reducibility of iron ore, including the following steps:

[0006] Provide an iron ore sample of known mass, place the iron ore sample in a closed space filled with protective gas, and heat it to 500-600°C.

[0007] A reducing gas is continuously introduced into the sealed space, while the gas inside the sealed space is continuously vented to maintain a pressure of 0.1-0.3 MPa. Simultaneously, the iron ore sample is continuously heated to 950-1050°C and maintained at that temperature. The iron ore sample is continuously weighed, and the degree of reduction is calculated.

[0008] The reducing gas includes a first reducing gas, a second reducing gas, and a third reducing gas, and the continuous introduction of the reducing gas into the sealed space specifically involves:

[0009] A first reducing gas, consisting of an inert protective gas and carbon monoxide, is continuously introduced into the sealed space for 1 hour. The carbon monoxide has a volume percentage of 23%-27%.

[0010] Subsequently, a second reducing gas, consisting of an inert protective gas and carbon monoxide, is continuously introduced into the sealed space for 1 hour. The carbon monoxide has a volume percentage of 29%-31%.

[0011] Subsequently, a third reducing gas is introduced into the sealed space for 1 hour. The third reducing gas consists of an inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 33%-37%.

[0012] In some embodiments of this application, the volume percentage of carbon monoxide in the first reducing gas is 25%.

[0013] In some embodiments of this application, the volume percentage of carbon monoxide in the second reducing gas is 30%.

[0014] In some embodiments of this application, the volume percentage of carbon monoxide in the third reducing gas is 35%.

[0015] In some embodiments of this application, the first reducing gas is introduced at a flow rate of 15 L / min, and / or,

[0016] The second reducing gas is introduced at a flow rate of 15 L / min, and / or,

[0017] The third reducing gas is introduced at a flow rate of 15 L / min.

[0018] In some embodiments of this application, the heating rate to 500°C does not exceed 10°C / min.

[0019] In some embodiments of this application, the iron ore sample is continuously heated to 1000°C at a heating rate of 3-7°C / min.

[0020] In some embodiments of this application, the inert protective gas includes at least nitrogen.

[0021] In some embodiments of this application, the carbon monoxide is supplied via a carbon monoxide cylinder.

[0022] In some embodiments of this application, the iron ore is selected from at least one of lump ore, pellet ore, and sinter.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art:

[0024] The iron ore reducibility determination method provided in this application can simulate the changes in temperature and atmosphere inside the blast furnace. The reduction temperature and CO concentration are gradually changed as the reduction time increases, which is more consistent with the temperature and CO concentration changes in the actual smelting process. Therefore, the collected test data is more consistent with the actual smelting situation. The reducibility results measured according to this invention have guiding significance for actual production. They can guide the improvement of iron-containing raw material quality, the rational distribution of materials in the upper part of blast furnace production, and the improvement of gas utilization rate. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of a method for determining the reducibility of iron ore provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the process of continuously introducing reducing gas into the enclosed space in this application;

[0029] Figure 3 This is a graph showing the change in the degree of reduction of Example 1 and Comparative Example 1 in this application over time;

[0030] Figure 4 This is a graph showing the change in the degree of reduction of Example 2 and Comparative Example 2 in this application over time;

[0031] Figure 5 This is a graph showing the change in the degree of reduction of Example 3 and Comparative Example 3 in this application over time. Detailed Implementation

[0032] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0033] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] It should be understood that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] It should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Additionally, the term "and / or" as used herein is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone.

[0037] In existing technologies, the determination of iron ore reduction performance is generally carried out according to the test method specified in the national standard GB / T13241-2017. This national standard requires the reduction temperature to be maintained at 900℃ throughout the experiment, and the reducing gas composition, expressed as a volume percentage, to remain constant at 30% CO and 70% N2. However, the blast furnace slag zone is not a homogeneous environment. In particular, the reducing gas composition and temperature gradually change. From top to bottom, the temperature in this zone gradually increases, ranging from approximately 300 to 1000℃, while the CO concentration also increases, gradually rising from approximately 25% to 35% or higher. During the blast furnace smelting process, iron ore gradually moves from the upper part to the lower part of the slag zone, with the ambient temperature and CO concentration gradually increasing. The impact of this characteristic on the iron ore reduction process is not reflected in the national standard test method. The national standard method typically only focuses on data at 180 minutes of reduction to represent the overall reduction performance of iron ore, but it cannot reflect the overall reduction process of iron ore in the blast furnace.

[0038] Based on this, the present application provides a method for determining the reducibility of iron ore, which can simulate the temperature and gas composition changes in a blast furnace, thereby reflecting the overall reduction process of iron ore in the blast furnace.

[0039] Please refer to Figure 1 The method for determining the reducibility of iron ore includes the following steps:

[0040] S1: Provide an iron ore sample of known mass, place the iron ore sample in a sealed space filled with protective gas, and heat it to 500-600°C.

[0041] S2: Continuously introduce reducing gas into the sealed space and continuously discharge the gas in the sealed space to make the gas pressure in the sealed space 0.1-0.3MPa. At the same time, continuously heat the iron ore sample to 950-1050℃ and maintain the temperature, and continuously weigh the iron ore sample to calculate the degree of reduction.

[0042] The reducing gas includes a first reducing gas, a second reducing gas, and a third reducing gas. Please refer to [reference needed]. Figure 2 The continuous introduction of reducing gas into the sealed space specifically includes the following steps:

[0043] S21: A first reducing gas is continuously introduced into the sealed space for 1 hour. The first reducing gas consists of an inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 23%-27%.

[0044] S22: Subsequently, a second reducing gas is introduced into the sealed space for 1 hour. The second reducing gas consists of an inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 29%-31%.

[0045] S23: Subsequently, a third reducing gas is introduced into the sealed space for 1 hour. The third reducing gas consists of an inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 33%-37%.

[0046] The iron ore reducibility determination method provided in this application can simulate the changes in temperature and atmosphere inside the blast furnace, gradually changing the reduction temperature and CO concentration as the reduction time increases. It can detect the changes in iron ore reducibility throughout the reduction process, which is more consistent with the changes in iron ore reducibility during smelting. The reducibility results obtained according to this invention have guiding significance for actual production, and can guide the improvement of iron-containing raw material quality, the rational distribution of materials in the upper part of blast furnace production, and the improvement of gas utilization rate.

[0047] Those skilled in the art will understand that although the temperature of the blast furnace block zone is generally 300-1000℃, the reaction rate between iron ore and carbon monoxide is very low at 300-500℃, and the reaction is negligible.

[0048] Those skilled in the art will understand that the enclosed space can be provided by experimental apparatus known in the art, including but not limited to reduction furnaces.

[0049] Those skilled in the art will understand that a high-temperature weighing device is pre-installed within the enclosed space to continuously weigh the iron ore sample. The high-temperature weighing device may be, for example, a thermogravimetric balance.

[0050] Those skilled in the art will understand that the inert protective gas can be at least one of the following gases known in the art that does not chemically react with iron ore and carbon monoxide at 25-1000°C and does not decompose itself at 25-1000°C: rare gases, nitrogen, etc.

[0051] In some embodiments of this application, the volume percentage of carbon monoxide in the first reducing gas is 25%. Those skilled in the art will understand that, under normal circumstances, the average volume percentage of carbon monoxide in the upper part of the blast furnace during iron ore blast furnace smelting is 25%. Those skilled in the art will also understand that, under special production conditions, the average volume percentage of carbon monoxide in the upper part of the blast furnace may deviate from 25%. To simulate the iron ore reduction process under such special conditions, the volume percentage of carbon monoxide in the first reducing gas can be any value or any sub-range of 23%-27%.

[0052] In some embodiments of this application, the volume percentage of carbon monoxide in the second reducing gas is 30%. Those skilled in the art will understand that, under normal circumstances, the average volume percentage of carbon monoxide in the upper part of the blast furnace is 30% during iron ore blast furnace smelting. Those skilled in the art will also understand that, under special production conditions, the average volume percentage of carbon monoxide in the upper part of the blast furnace may deviate from 30%. To simulate the iron ore reduction process under such special conditions, the volume percentage of carbon monoxide in the first reducing gas can be any value or sub-range of 29%-31%.

[0053] In some embodiments of this application, the volume percentage of carbon monoxide in the third reducing gas is 35%. Those skilled in the art will understand that, under normal circumstances, the average volume percentage of carbon monoxide in the lower part of the blast furnace during iron ore blast furnace smelting is 35%. Those skilled in the art will also understand that, under special production conditions, the average volume percentage of carbon monoxide in the lower part of the blast furnace may deviate from 35%. To simulate the iron ore reduction process under such special conditions, the volume percentage of carbon monoxide in the first reducing gas can be any value or sub-range of 33%-37%.

[0054] In some embodiments of this application, the first reducing gas is introduced at a flow rate of 15 L / min, and / or,

[0055] The second reducing gas is introduced at a flow rate of 15 L / min, and / or,

[0056] The third reducing gas is introduced at a flow rate of 15 L / min.

[0057] In some embodiments of this application, the heating rate to 500°C does not exceed 10°C / min.

[0058] In some embodiments of this application, the iron ore sample is continuously heated to 1000°C at a heating rate of 3°C / min. A heating rate that is too slow can lead to an inaccurate reaction and results that deviate from the actual situation. Conversely, a heating rate that is too high can accelerate the reaction, potentially causing the final test results to exceed normal values.

[0059] In some embodiments of this application, the inert protective gas includes at least nitrogen. Nitrogen is inexpensive and readily available because it does not react with iron ore or carbon monoxide at temperatures between 25 and 1000°C, does not decompose, and is readily available.

[0060] In some embodiments of this application, the carbon monoxide is provided via a carbon monoxide cylinder. In the current national standard (GB / T13241-2017), carbon monoxide is obtained through a gasifier. However, in practice, the purity and flow rate of carbon monoxide obtained through a gasifier are greatly affected by the type of raw material used in the gasifier, leading to experimental results that easily deviate from reality. The current national standard (GB / T13241-2017) generally only focuses on the overall reducing power of iron ore, neglecting changes during the reduction process. In contrast, the iron ore reducing power determination method provided in this application simulates the reduction process of iron ore in a blast furnace, focusing on changes during the reduction process. Therefore, using a carbon monoxide cylinder to provide carbon monoxide makes it easier to control the flow rate and purity of the carbon monoxide, making it a more preferred solution.

[0061] In some embodiments of this application, the iron ore is selected from at least one of lump ore, pellet ore, and sinter.

[0062] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0063] Example 1

[0064] This embodiment provides a method for determining the reducibility of iron ore, which is performed through the following steps:

[0065] Weigh an iron ore sample, specifically an Australian lump ore sample, place the iron ore sample on the porous plate of the reduction tube, flatten it, insert a thermocouple and seal the sealing cap, set up a thermogravimetric balance in the reduction furnace, and place the reduction tube on the thermogravimetric balance.

[0066] Nitrogen gas is introduced into the reduction furnace, and the furnace is heated to 500°C using a thermocouple at a rate of 10°C / min.

[0067] The reduction furnace is heated by a thermocouple at a rate of 3°C / min until it reaches 1000°C and is then maintained at that temperature. During this process, a reducing gas is continuously introduced, and the iron ore sample and the reduction tube are continuously weighed using a thermogravimetric balance. After deducting the weight of the reduction tube, the weight of the iron ore sample is obtained, and the degree of reduction is calculated.

[0068] In this embodiment, the introduction of reducing gas during this process is specifically performed through the following steps:

[0069] Nitrogen and carbon monoxide were introduced into the sealed space at a flow rate of 11.25 L / min and a flow rate of 3.75 L / min, respectively, for 1 hour.

[0070] The nitrogen flow rate was then adjusted to 10.05 L / min, and the carbon monoxide flow rate was adjusted to 4.5 L / min, and this was continued for 1 hour.

[0071] The flow rate of nitrogen was then adjusted to 9.75 L / min, and the flow rate of carbon monoxide was adjusted to 5.25 L / min, and this was continued for 1 hour.

[0072] In this embodiment, carbon monoxide is supplied via a carbon monoxide gas cylinder.

[0073] In this embodiment, unless otherwise specified, all other matters in this method are carried out in accordance with the national standard for static reduction test method of iron ore (GB / T13241-2017), such as the test apparatus, preparation of iron ore samples, recording of test data, and calculation of reduction degree.

[0074] Example 2

[0075] The only difference between this embodiment and Embodiment 1 is that the iron ore sample in this embodiment is actually pellet ore.

[0076] Example 3

[0077] The only difference between this embodiment and Embodiment 1 is that the iron ore sample in this embodiment is sintered ore.

[0078] Comparative Example 1

[0079] Weigh out iron ore samples and perform reducibility testing on the iron ore samples according to the national standard (GB / T13241-2017). The iron ore samples specifically used were Australian lump ore.

[0080] Comparative Example 2

[0081] The only difference between this embodiment and Comparative Example 1 is that the iron ore sample in this embodiment is actually pellet ore.

[0082] Comparative Example 3

[0083] The only difference between this embodiment and Comparative Example 1 is that the iron ore sample in this embodiment is sintered ore.

[0084] The data on the change of reduction degree over time measured in Examples 1-3 and Comparative Examples 1-3 are as follows:

[0085]

[0086] Comparing Example 1 and Comparative Example 1, it can be observed that the reduction processes of Example 1 and Comparative Example 1 differ significantly. In Example 1, the initial RI (reduction ratio) increases slowly, but increases rapidly later; in Comparative Example 1, the initial increase is rapid, but the increase slows down later. However, at 180 minutes, the RI of Example 1 and Comparative Example 1 are almost identical. Please refer to... Figure 3 , Figure 3 The above-mentioned patterns in Example 1 and Comparative Example 1 are visually demonstrated. Please refer to the table above and... Figure 4 , Figure 5 Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 also showed similar patterns.

[0087] In actual iron ore smelting, during the early stages of smelting, the iron ore mainly remains in the upper part of the blast furnace, where the temperature and CO concentration are not high, and the reduction reaction rate is relatively slow. During the later stages of smelting, it gradually enters the middle of the blast furnace, where the temperature and CO concentration increase, the reduction reaction rate accelerates, and the degree of reduction (RI) increases rapidly. It is evident that the reduction behavior of iron ore in blast furnace smelting is not similar to Comparative Examples 1-3, but is quite similar to Examples 1-3. Therefore, Comparative Examples 1-3, i.e., the traditional national standard (GB / T13241-2017) for determining the reducibility of iron ore, are only suitable for indicating the quality of iron ore reduction performance and cannot reflect the changes in iron ore throughout the entire blast furnace smelting process. In contrast, the iron ore reducibility determination method provided in this application can not only detect the quality of iron ore reduction performance but also accurately reflect the changes in iron ore throughout the entire blast furnace smelting process.

[0088] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for determining the reducibility of an iron ore, characterized by, The method comprises the following steps: providing an iron ore sample with a known mass, heating the iron ore sample in a sealed space filled with inert protective gas to 500-600℃; continuously supplying a reducing gas into the sealed space, continuously discharging the gas in the sealed space so that the gas pressure in the sealed space is 0.1-0.3MPa, continuously heating the iron ore sample to 950-1050℃ and keeping the temperature, and continuously weighing the iron ore sample to calculate the reduction degree, the reducing gas comprises a first reducing gas, a second reducing gas and a third reducing gas, and the continuously supplying a reducing gas into the sealed space specifically comprises: supplying the first reducing gas into the sealed space for 1h, the first reducing gas being composed of inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 23%-27%, then supplying the second reducing gas into the sealed space for 1h, the second reducing gas being composed of inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 29-31%, then supplying the third reducing gas into the sealed space for 1h, the third reducing gas being composed of inert protective gas and carbon monoxide, wherein the volume percentage of carbon monoxide is 33%-37%.

2. The method for measuring reducibility of iron ore according to claim 1, characterized by, the volume percentage of carbon monoxide in the first reducing gas is 25%.

3. The method for measuring reducibility of iron ore according to claim 1, characterized by, the volume percentage of carbon monoxide in the second reducing gas is 30%.

4. The method for measuring reducibility of iron ore according to claim 1, characterized by, the volume percentage of carbon monoxide in the third reducing gas is 35%.

5. The method for measuring reducibility of iron ore according to claim 1, characterized by, the first reducing gas is supplied at a flow rate of 15L / min, and / or, the second reducing gas is supplied at a flow rate of 15L / min, and / or, the third reducing gas is supplied at a flow rate of 15L / min.

6. The method for measuring reducibility of iron ore according to claim 1, characterized by, In the step of heating the iron ore sample in a sealed space filled with inert protective gas to 500-600℃, the heating speed is not more than 10℃ / min.

7. The method for measuring reducibility of iron ore according to claim 1, characterized by, In the step of continuously heating the iron ore sample to 950-1050℃, the heating speed is 3-7℃ / min.

8. The method of determining the reducibility of iron ores according to any one of claims 1 to 7, characterized in that, The inert protective gas at least comprises nitrogen.

9. The method for measuring reducibility of iron ore according to claim 8, characterized by, The iron ore is selected from at least one of lump ore, pellet ore and sintered ore.

10. The method for measuring reducibility of iron ore according to claim 8, characterized by, The carbon monoxide is provided by a carbon monoxide cylinder.

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