Evaluation method for melting rate in high-temperature molten pool in direct reduction iron production process

Abstract

The invention provides a method for evaluating the melting rate in a high-temperature molten pool in a direct reduction iron production process. According to the method, melting of the direct reduction iron in a molten pool is analyzed in detail, the melting process of the direct reduction iron is specifically represented in an image acquisition mode, scientific datamation processing is carried out on acquired images in cooperation with a computer image processing method, and finally a series of complete melting curves are obtained. The melting performance of the direct reduced iron is evaluated through the melting time and the melting rate, and a quantitative evaluation standard of the melting efficiency of the direct reduced iron in a high-temperature molten pool is provided. The method not only perfects the process of directly feeding the reduced iron into the electric furnace, but also provides data support for flow operation of electric furnace steelmaking, and lays a foundation for promoting low-carbon green development of short-flow steelmaking of the shaft furnace and the electric furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of direct reduced iron high-temperature molten pool control, and relates to a method for evaluating the melting rate in a high-temperature molten pool during the direct reduced iron production process. Background Art

[0002] Direct reduction ironmaking technology uses non-coking coal as energy. Under the condition of no melting and no slag formation, the raw materials basically maintain their original physical form. The iron oxide is reduced to obtain a solid product with metallic iron as the main component. It has the advantages of short process, low pollution, and low consumption. It reduces greenhouse gas emissions and is environmentally friendly. It is one of the development directions of China's steel industry. Against the background of carbon peak and carbon neutrality, the global direct reduced iron (DRI, including HBI) output continues to grow, and the DRI+ electric furnace short-process steelmaking process is highly valued by the steel industry. From the perspective of steel manufacturing process, most projects use DRI for electric furnace steelmaking or blast furnace ironmaking; some projects explore the technical route of combining DRI with submerged arc furnaces and then connecting with existing converter facilities. Whether it is an electric furnace, converter, or blast furnace process, the use of direct reduced iron as a ferrous raw material will definitely involve the melting process of direct reduced iron in the molten pool. The melting efficiency of direct reduced iron will greatly affect the operation of each process. Therefore, judging the melting state of direct reduced iron in the molten pool and calculating the melting time play an important role in the operation of the whole process. However, there is currently a lack of effective means to determine the melting state of direct reduced iron on site.

[0003] According to literature research, since the formation of the direct reduced iron production process, there have been few studies on the melting of direct reduced iron in a molten pool. For example, the existing patent CN115679035 discloses a method and device for preheating scrap steel based on hot-charged direct reduced iron, which proposes a method for saving energy consumption by preheating scrap steel with hot-charged direct reduced iron, making full use of the sensible heat of hot-charged direct reduced iron, and solving the problems of low and uneven preheating temperature of scrap steel in the prior art. Another example is the patent CN114959152 discloses a method and a vertical furnace device for producing reduced iron with two-stage electric heating, which develops a method and a vertical furnace device for producing reduced iron with two-stage electric heating, including two electric heating reduction sections with different heating and heat transfer modes in the reduction zone of the vertical furnace, which can effectively reduce the amount of reducing gas used in the production of direct reduced iron, and can effectively improve the thermal efficiency, with obvious energy-saving and emission-reduction effects. Another example is the patent CN114438284, which discloses a method for smelting direct reduced iron in an electric furnace by hot charging. This invention effectively improves energy efficiency, reduces the consumption of electric energy and electrodes in electric furnace smelting, and reduces smelting costs. Another example is the patent CN115315533, which discloses an "integration of a DR device and an electric DRI melting furnace for producing high-performance iron", which discloses a method for direct reduction coupled electric furnace melting, including providing a vertical furnace and reducing gas for a direct reduction device to reduce iron oxide while providing direct reduced iron into the electric furnace for melting.

[0004] Although all these studies provide good research ideas for the melting of direct reduced iron in a high-temperature molten pool, there are few studies on the melting rate of direct reduced iron in these existing studies, and no effective measurement method and scientific evaluation system have been formed. Therefore, developing a scientific and systematic method to judge the melting rate of direct reduced iron in a high-temperature molten pool is of great significance for reasonably judging the furnace condition, adjusting the furnace temperature, and operating the electric furnace or converter.

[0005] Therefore, how to find a method to evaluate the melting rate of direct reduced iron in a high-temperature molten pool is of great significance for in-depth analysis of the changes in the quality of molten iron or molten steel during the melting process and improving the melting efficiency. It is also one of the problems that many front-line researchers in the industry urgently need to solve. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for evaluating the melting rate in a high-temperature molten pool during the production of direct reduced iron. The present invention evaluates the melting performance of direct reduced iron by melting time and melting rate, and proposes a quantitative evaluation standard for the melting efficiency of direct reduced iron in a high-temperature molten pool.

[0007] The present invention provides a method for evaluating the melting rate in a high-temperature molten pool during the production of direct reduced iron, comprising the following steps:

[0008] 1) In a protective atmosphere, hot-charged direct-reduced iron pellets are placed in a high-temperature molten iron bath for a melting experiment, and the melting process of the direct-reduced iron pellets is captured by video;

[0009] and / or,

[0010] In a protective atmosphere, cold-charged direct-reduced iron pellets were placed into a high-temperature molten iron bath for melting experiments, and the melting process of the direct-reduced iron pellets was captured by video.

[0011] 2) The primary image information obtained by the above-mentioned step is processed to identify pixels, and the images with different melting times are exported as grayscale images. The grayscale value is used to identify the unmelted area, and then the melting curve is drawn;

[0012] 3) Obtaining evaluation indexes through melting curves, and then obtaining influencing factors of melting rate of direct reduced iron pellets in high temperature molten iron pool and an evaluation system of melting rate;

[0013] The evaluation indexes include melting start time, melting end time and maximum melting rate.

[0014] Preferably, the high-temperature molten iron is obtained by heating and melting direct reduced iron and carbon;

[0015] The temperature of the molten iron in the high-temperature molten iron bath is 1350-1450°C;

[0016] The carbon content in the high-temperature molten iron is 2% to 4% by mass.

[0017] Preferably, the flow rate of the protective atmosphere is 1 to 5 L / min;

[0018] The number of the direct reduced iron pellets includes single or multiple;

[0019] The direct reduced iron pellets include DRI and / or HBI.

[0020] Preferably, the metallization rate of the direct reduced iron pellets is greater than or equal to 80%;

[0021] The carbon mass content of the direct reduced iron pellets is 0 to 3%;

[0022] The temperature of the hot-charged direct-reduced iron pellets is 300-400°C.

[0023] Preferably, the high-temperature molten iron pool comprises a high-temperature molten iron pool having visibility;

[0024] The image processing includes using computer software to perform image processing;

[0025] The computer software includes Image J software.

[0026] Preferably, the video recording is continuous video recording;

[0027] The pixel recognition is specifically as follows: based on the pixels of the collected primary image, the relative size ratio of the direct reduced iron pellets is calculated by pixel ratio, thereby reflecting the overall melting process and melting degree.

[0028] Preferably, the calculation formula of the melting degree is as shown in (1):

[0029] I=Dt / D0=(Pt / P0) 1 / 2 (1);

[0030] Wherein, I is the degree of melting, Dt and D0 are the diameters of the direct reduced iron pellets at time t and the initial state, respectively, and Pt and P0 are the pixel points of the unmelted area of ​​the direct reduced iron pellets at time t and the initial state, respectively.

[0031] Preferably, the melting curve includes the initial melting time, the final melting time, the overall melting rate curve and the maximum melting rate of the direct reduced iron pellets;

[0032] The overall melting rate is obtained by calculating the ratio of the size change of the direct reduced iron pellets to time;

[0033] The influencing factors include one or more of the metallization rate of the direct reduced iron pellets, the carbon content of the direct reduced iron pellets, hot charging, hot charging temperature and cold charging.

[0034] Preferably, drawing the melting curve specifically involves analyzing the entire melting process of the direct reduced iron pellets by drawing the melting curve;

[0035] The evaluation method further comprises the following steps: optimizing and adjusting the parameters of direct reduced iron pellets through the evaluation system;

[0036] The parameters include influencing factors.

[0037] Preferably, the optimization and adjustment method includes adjusting the temperature parameters of the constant temperature section of the tubular furnace for preparing the direct reduced iron pellets, thereby optimizing and adjusting the parameters of the direct reduced iron pellets;

[0038] The constant temperature section includes a preheating section and / or a central high temperature section.

[0039] The invention provides a method for evaluating the melting rate in a high-temperature molten pool during the production of direct reduced iron. The method comprises the following steps: first, in a protective atmosphere, placing hot-charged direct reduced iron pellets into a high-temperature molten iron pool for a melting experiment, and capturing the melting process of the direct reduced iron pellets by video recording; and / or, in a protective atmosphere, placing cold-charged direct reduced iron pellets into a high-temperature molten iron pool for a melting experiment, and capturing the melting process of the direct reduced iron pellets by video recording; then, pixel recognition is performed on the primary image information obtained by video recording in the above steps by image processing, images with different melting times are exported as grayscale images, grayscale values ​​are used to identify unmelted areas, and then a melting curve is drawn; preferably, an evaluation index is obtained by the melting curve, and then an evaluation system of factors affecting the melting rate of the direct reduced iron pellets in the high-temperature molten iron pool and a melting rate is obtained; the evaluation index comprises a melting start time, a melting end time and a maximum melting rate. Compared with the prior art, the method for evaluating the melting rate of direct reduced iron in a high-temperature molten pool provided by the present invention quantitatively characterizes the melting of direct reduced iron in a high-temperature molten pool for the first time through image acquisition and image processing, and proposes a scientific melting efficiency evaluation system, laying the foundation for promoting the low-carbon and green development of ironmaking raw materials.

[0040] The present invention makes a detailed analysis of the melting of direct reduced iron in the molten pool, specifically characterizes the melting process of direct reduced iron by means of image acquisition, and scientifically digitizes the acquired images by means of computer image processing, finally obtaining a series of complete melting curves, evaluating the melting performance of direct reduced iron by melting time and melting rate, and proposing a quantitative evaluation standard for the melting efficiency of direct reduced iron in a high-temperature molten pool. It not only improves the process of direct reduced iron entering the electric furnace, but also provides data support for the process operation of electric furnace steelmaking, laying a foundation for promoting the low-carbon green development of short-process steelmaking in vertical furnace electric furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram for evaluating the melting rate of direct reduced iron in a high-temperature molten pool provided by the present invention. DETAILED DESCRIPTION

[0042] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0043] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0044] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses industrial purity or conventional purity in the field of gas-based direct reduced iron.

[0045] All noun expressions and abbreviations in the present invention are conventional noun expressions and abbreviations in the field. Each noun expression and abbreviation is clear and unambiguous in its relevant application field. Those skilled in the art can clearly, accurately and uniquely understand them based on the noun expressions and abbreviations.

[0046] The present invention provides a method for evaluating the melting rate in a high-temperature molten pool during the production of direct reduced iron, comprising the following steps:

[0047] 1) In a protective atmosphere, hot-charged direct-reduced iron pellets are placed in a high-temperature molten iron bath for a melting experiment, and the melting process of the direct-reduced iron pellets is captured by video;

[0048] and / or,

[0049] In a protective atmosphere, cold-charged direct-reduced iron pellets were placed into a high-temperature molten iron bath for melting experiments, and the melting process of the direct-reduced iron pellets was captured by video.

[0050] 2) The primary image information obtained by the above-mentioned step is processed to identify pixels, and the images with different melting times are exported as grayscale images. The grayscale value is used to identify the unmelted area, and then the melting curve is drawn;

[0051] 3) Obtaining evaluation indexes through melting curves, and then obtaining influencing factors of melting rate of direct reduced iron pellets in high temperature molten iron pool and an evaluation system of melting rate;

[0052] The evaluation indexes include melting start time, melting end time and maximum melting rate.

[0053] The present invention firstly puts hot-charged direct-reduced iron pellets into a high-temperature molten iron bath to perform a melting experiment under a protective atmosphere, and captures the melting process of the direct-reduced iron pellets by video recording;

[0054] and / or,

[0055] Under a protective atmosphere, cold-charged direct reduced iron pellets were placed into a high-temperature molten iron pool for a melting experiment, and the melting process of the direct reduced iron pellets was captured by video.

[0056] In the present invention, the high-temperature molten iron is preferably obtained by heating and melting direct reduced iron and carbon.

[0057] In the present invention, the temperature of the molten iron in the high-temperature molten iron pool is preferably 1350-1450°C, more preferably 1370-1430°C, and more preferably 1390-1410°C.

[0058] In the present invention, the carbon mass content in the high-temperature molten iron is preferably 2% to 4%, more preferably 2.4% to 3.6%, and more preferably 2.8% to 3.2%.

[0059] In the present invention, the flow rate of the protective atmosphere is preferably 1 to 5 L / min, more preferably 1.5 to 4.5 L / min, more preferably 2 to 4 L / min, and specifically 3 L / min.

[0060] In the present invention, the number of the direct reduced iron pellets preferably includes a single one or a plurality of pellets.

[0061] In the present invention, the direct reduced iron pellets preferably include DRI and / or HBI, more preferably DRI or HBI.

[0062] In the present invention, the metallization rate of the direct reduced iron pellets is preferably greater than or equal to 80%.

[0063] In the present invention, the carbon mass content of the direct reduced iron pellets is preferably 0-3%, or 0.01%-2.5%, or 0.1%-2%, or 0.5%-1.5%.

[0064] In the present invention, the temperature of the hot-charged direct reduced iron pellets is preferably 300-400°C, more preferably 320-380°C, and more preferably 340-360°C.

[0065] In the present invention, the high temperature molten iron pool preferably includes a high temperature molten iron pool having visibility.

[0066] In the present invention, the image processing preferably includes performing image processing using computer software.

[0067] In the present invention, the computer software preferably includes Image J software.

[0068] In the present invention, the imaging is preferably continuous imaging.

[0069] The present invention further performs pixel recognition on the primary image information obtained by the above-mentioned step through image processing, exports images with different melting times as grayscale images, uses grayscale values ​​to identify unmelted areas, and then draws a melting curve.

[0070] In the present invention, the pixel identification is preferably: based on the pixels of the collected primary image, the relative size ratio of the direct reduced iron pellets is calculated by pixel ratio, thereby reflecting the overall melting process and melting degree.

[0071] Finally, the present invention obtains the evaluation index through the melting curve, and then obtains the influencing factors of the melting rate of the direct reduced iron pellets in the high-temperature molten iron bath and the evaluation system of the melting rate;

[0072] The evaluation indexes include melting start time, melting end time and maximum melting rate.

[0073] In the present invention, the calculation formula of the melting degree is shown in (1):

[0074] I=Dt / D0=(Pt / P0) 1 / 2 (1);

[0075] Among them, I is preferably the degree of melting, Dt and D0 are preferably the diameters of the direct reduced iron pellets at time t and the initial state, respectively, and Pt and P0 are preferably the pixel points of the unmelted area of ​​the direct reduced iron pellets at time t and the initial state, respectively.

[0076] In the present invention, the melting curve preferably includes the initial melting time, the final melting time, the overall melting rate curve and the maximum melting rate of the direct reduced iron pellets;

[0077] In the present invention, the overall melting rate is preferably obtained by calculating the ratio of the change in size of the direct reduced iron pellets to time.

[0078] In the present invention, the influencing factors preferably include one or more of the metallization rate of the direct reduced iron pellets, the carbon content of the direct reduced iron pellets, hot charging, hot charging temperature and cold charging, and more preferably the metallization rate of the direct reduced iron pellets, the carbon content of the direct reduced iron pellets, hot charging, hot charging temperature or cold charging.

[0079] In the present invention, drawing the melting curve is preferably to analyze the entire melting process of the direct reduced iron pellets by drawing the melting curve.

[0080] In the present invention, the evaluation method preferably further comprises the following steps: optimizing and adjusting the parameters of the direct reduced iron pellets through the evaluation system.

[0081] In the present invention, the parameters preferably include influencing factors.

[0082] In the present invention, the optimization and adjustment method preferably includes adjusting the temperature parameters of the constant temperature section of the tubular furnace for preparing the direct reduced iron pellets, thereby optimizing and adjusting the parameters of the direct reduced iron pellets;

[0083] In the present invention, the constant temperature section preferably includes a preheating section and / or a central high temperature section, and more preferably a preheating section or a central high temperature section.

[0084] In order to better complete and refine the technical solution and better evaluate the melting rate in the high-temperature molten pool during the direct reduced iron production process, the evaluation method of the melting rate in the high-temperature molten pool during the direct reduced iron production process may specifically include the following contents:

[0085] A method for evaluating the melting rate of direct reduced iron in a high-temperature molten pool is provided. The melting of direct reduced iron in the molten pool is analyzed in detail.

[0086] The melting process of direct reduced iron is specifically characterized by image acquisition, and the acquired images are scientifically digitized using computer image processing methods. Finally, a series of complete melting curves are obtained, and for the first time, a quantitative evaluation standard for evaluating the melting efficiency of direct reduced iron in a high-temperature molten pool is established.

[0087] Specifically, after the primary image information collected by the camera is processed by a computer, the obtained pixel map can clearly and effectively identify the unmelted area.

[0088] Specifically, the direct reduced iron used in the experiment requires a metallization rate greater than 80% to ensure that the molten pool at a certain temperature can effectively melt the direct reduced iron.

[0089] Specifically, the experiment can design different high-temperature molten pools, including high-temperature molten iron, high-temperature slag, etc. The basic requirement is that the molten pool temperature needs to reach above the melting point of the direct reduced iron material.

[0090] Specifically, the camera needs to add a filter when shooting. Due to the strong thermal radiation from high temperature, adding a filter can both protect the lens and improve image quality.

[0091] Specifically, the evaluation criteria mainly include three indicators, namely, the initial melting time, the final melting time, and the maximum melting rate.

[0092] Specifically, Image J was used as image processing software.

[0093] Specifically, the image format that can be processed is an 8-bit grayscale image, so the original image format needs to be converted first.

[0094] See also Figure 1 , Figure 1 A schematic diagram for evaluating the melting rate of direct reduced iron in a high-temperature molten pool provided by the present invention.

[0095] The present invention provides a method for evaluating the melting rate of direct reduced iron in a high-temperature molten pool. This method quantitatively characterizes the melting of direct reduced iron in a high-temperature molten pool for the first time by means of image acquisition and image processing, and proposes a scientific melting efficiency evaluation system, laying a foundation for promoting the low-carbon and green development of ironmaking raw materials.

[0096] The present invention adopts direct reduced pellets as a typical direct reduced iron material, hereinafter referred to as pellets, and includes the following experimental steps:

[0097] (1) First, the temperature parameters of each constant temperature section of the tube furnace, including the preheating section and the central high temperature section, were measured to prepare the direct reduced iron required for the experiment;

[0098] (2) preparing a high-temperature molten iron pool by mixing direct reduced iron powder and carbon powder in different proportions and heating the furnace as the furnace is heated;

[0099] (3) Conducting direct reduced iron hot charging and cold charging experiments respectively, placing a single pellet into molten iron for melting experiments, and introducing argon gas for protection throughout the melting process;

[0100] (4) Capturing the melting process of direct reduced iron by continuous video recording;

[0101] (5) A method for evaluating the melting rate was constructed and an evaluation index for the melting efficiency of direct reduced iron was proposed. The primary image information obtained by the camera was subjected to pixel recognition through computer image processing methods. The images with different melting times were exported as 8-bit grayscale images. The grayscale value was used to identify the unmelted area, and then the melting curve was drawn.

[0102] Specifically, the pixels of the collected image are used to calculate the relative size ratio of the pellets through the pixel ratio, and then the overall melting process is described. The degree of melting is: I = Dt / D0 = (Pt / P0) 1 / 2 ;

[0103] Where I is the degree of melting, Dt and D0 are the diameters of the pellet at time t and the initial state, respectively, and Pt and P0 are the pixel points of the unmelted area of ​​the pellet at time t and the initial state, respectively;

[0104] Specifically, the ratio of size change to time is calculated to reflect the melting rate of the entire pellet, and the maximum melting rate within the time period is obtained, the melting rate: v = ΔI / Δt;

[0105] Where v is the melting rate, ΔI is the change in the melting degree of the pellet in a very short period of time Δt;

[0106] At the same time, record the initial melting time of the pellet as ts and the final melting time as tm.

[0107] (6) The entire melting process of the pellets was analyzed, and the influence of factors such as the metallization rate and carbon content of the pellets on the entire melting process was comprehensively analyzed. At the same time, the differences between hot-charged pellets and cold-charged pellets were compared, and three indicators, namely the melting start time, melting end time, and maximum melting rate, were proposed to optimize the parameters of the pellets.

[0108] Specifically, the direct reduced iron material in step (1) can be DRI (sponge iron, direct reduced iron) or HBI (hot briquetted iron). There are certain requirements for the metallization rate of the material, and the metallization rate is controlled to be above 80%.

[0109] Specifically, the high-temperature molten pool prepared in step (2) simulates the molten iron environment, so the carbon content of the molten iron is controlled to be around 2% to 4%, and the temperature of the molten iron is controlled to be between 1350°C and 1450°C.

[0110] Specifically, in step (3), the argon flow rate is controlled at about 3 L / min, so that the entire tubular furnace has a protective atmosphere, and a single pellet is loaded into the molten iron pool using a high-temperature resistant glass conduit.

[0111] Specifically, in step (4), a continuous camera is used to record the melting process, and a lens protection sheet is added in front of the camera to prevent damage to the lens due to high temperature radiation, and to filter part of the radiation to improve the camera quality.

[0112] Specifically, in step (5), the image is processed once using Image J software. Since the melting process is recorded using the same camera, there is no obvious difference in the grayscale value of the acquired image after processing, which has an important influence on improving the accuracy of recognition.

[0113] Specifically, the three indicators of melting start time, melting end time and maximum melting rate proposed in step (6) can effectively evaluate the melting efficiency of the pellets in the high-temperature molten pool.

[0114] The above content of the present invention provides a method for evaluating the melting rate in a high-temperature molten pool during the production of direct reduced iron. The method for evaluating the melting rate of direct reduced iron in a high-temperature molten pool provided by the present invention quantitatively characterizes the melting of direct reduced iron in a high-temperature molten pool for the first time by means of image acquisition and image processing, and proposes a set of scientific melting efficiency evaluation system, laying a foundation for promoting the low-carbon green development of ironmaking raw materials.

[0115] The present invention makes a detailed analysis of the melting of direct reduced iron in the molten pool, specifically characterizes the melting process of direct reduced iron by means of image acquisition, and scientifically digitizes the acquired images by means of computer image processing, finally obtaining a series of complete melting curves, evaluating the melting performance of direct reduced iron by melting time and melting rate, and proposing a quantitative evaluation standard for the melting efficiency of direct reduced iron in a high-temperature molten pool. It not only improves the process of direct reduced iron entering the electric furnace, but also provides data support for the process operation of electric furnace steelmaking, laying a foundation for promoting the low-carbon green development of short-process steelmaking in vertical furnace electric furnace.

[0116] In order to further illustrate the present invention, a method for evaluating the melting rate in a high-temperature molten pool in a direct reduced iron production process provided by the present invention is described in detail below in conjunction with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention, and the protection scope of the present invention is not limited to the following embodiments.

[0117] Example 1: Direct reduced iron melting rate evaluation case 1

[0118] This case compares the melting experiments of direct reduced iron pellets with metallization rates of 93.2-93.5%, carbon contents of 0.18, 0.98, 2.02% and gangue contents of 2.0-2.3% in molten iron. The pellets are added by cold charging to keep the carbon content in the molten iron pool at 3% and the temperature is controlled at 1450℃. Since the mass of molten iron far exceeds that of the pellets, there is sufficient heat in the melting environment of the pellets. According to the theoretical basis, the metal Fe in the pellets must contain a certain C content to melt at a temperature below 1538℃. Since the molten iron contains a higher C content, the pellets selected for the experiment can melt in this environment.

[0119] The melting process was captured by a camera. After image processing, the melting curve of the pellets was obtained, and a series of evaluation indicators were obtained. The initial melting time of the three pellets was 32s, 28s, and 25s, the end melting time was 115s, 108s, and 102s, and the maximum melting rate was 0.67s. -1 , 0.73s -1 , 0.81s -1 .

[0120] The results show that the higher the carbon content of the pellets, the shorter the melting end time and the faster the melting rate.

[0121] Example 2: Direct Reduced Iron Melting Rate Evaluation Case 2

[0122] This case compares the melting experiments of direct reduced iron pellets with metallization rates of 94.85%, 87.79% and 80.65%, carbon contents of 1.9-2.0% and gangue contents of 2.0-2.3% in slag. The pellets were added by hot charging, the slag basicity was maintained at 2.0, and the experiment was carried out at a slag temperature of 1450°C.

[0123] The melting process was captured by a camera. After image processing, the melting curve of the pellets was obtained. A series of evaluation indicators were obtained as follows: the initial melting time of the three pellets was 25s, 21s, and 19s, the end melting time was 96s, 84s, and 75s, and the maximum melting rate was 0.80s. -1 , 0.93s -1 , 0.99s -1 .

[0124] The results show that the metallization rate has a significant effect on the dissolution of the pellets. When the metallization rate is low, the dissolution time is significantly reduced. This is mainly because the pellets contain a large amount of FeO, which is easy to form a liquid phase with the alkaline slag, and the rate of liquid phase formation is faster at high temperatures.

[0125] The above is a detailed introduction to a method for evaluating the melting rate in a high-temperature molten pool in a direct reduced iron production process provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and its core ideas of the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for evaluating the melting rate in a high-temperature molten pool in a direct reduced iron production process, characterized in that: The following steps are involved: 1) In a protective atmosphere, hot-charged direct-reduced iron pellets are placed in a high-temperature molten iron bath for a melting experiment, and the melting process of the direct-reduced iron pellets is captured by video; and / or, In a protective atmosphere, cold-charged direct-reduced iron pellets were placed into a high-temperature molten iron bath for melting experiments, and the melting process of the direct-reduced iron pellets was captured by video. 2) The primary image information obtained by the above-mentioned step is processed to identify pixels, and the images with different melting times are exported as grayscale images. The grayscale value is used to identify the unmelted area, and then the melting curve is drawn; 3) Obtaining evaluation indexes through melting curves, and then obtaining influencing factors of melting rate of direct reduced iron pellets in high temperature molten iron pool and an evaluation system of melting rate; The evaluation indexes include melting start time, melting end time and maximum melting rate.

2. The evaluation method according to claim 1, characterized in that: The high-temperature molten iron is obtained by heating and melting direct reduced iron and carbon; The temperature of the molten iron in the high-temperature molten iron bath is 1350-1450°C; The carbon content in the high-temperature molten iron is 2% to 4% by mass.

3. The evaluation method according to claim 1, characterized in that: The flow rate of the protective atmosphere is 1 to 5 L / min; The number of the direct reduced iron pellets includes single or multiple; The direct reduced iron pellets include DRI and / or HBI.

4. The evaluation method according to claim 1, characterized in that: The metallization rate of the direct reduced iron pellets is greater than or equal to 80%; The carbon mass content of the direct reduced iron pellets is 0 to 3%; The temperature of the hot-charged direct-reduced iron pellets is 300-400°C.

5. The evaluation method according to claim 1, characterized in that: The high-temperature molten iron pool includes a high-temperature molten iron pool with visibility; The image processing includes using computer software to perform image processing; The computer software includes Image J software.

6. The evaluation method according to claim 1, characterized in that: The video recording is specifically continuous video recording; The pixel recognition is specifically as follows: based on the pixels of the collected primary image, the relative size ratio of the direct reduced iron pellets is calculated by pixel ratio, thereby reflecting the overall melting process and melting degree.

7. The evaluation method according to claim 6, characterized in that: The calculation formula of the melting degree is shown in (1): I=Dt / D0=(Pt / P0) 1 / 2 (1); Wherein, I is the degree of melting, Dt and D0 are the diameters of the direct reduced iron pellets at time t and the initial state, respectively, and Pt and P0 are the pixel points of the unmelted area of ​​the direct reduced iron pellets at time t and the initial state, respectively.

8. The evaluation method according to claim 1, characterized in that: The melting curve includes the initial melting time of the direct reduced iron pellets, the final melting time, the overall melting rate curve of the direct reduced iron pellets and the maximum melting rate; The overall melting rate is obtained by calculating the ratio of the size change of the direct reduced iron pellets to time; The influencing factors include one or more of the metallization rate of the direct reduced iron pellets, the carbon content of the direct reduced iron pellets, hot charging, hot charging temperature and cold charging.

9. The evaluation method according to claim 1, characterized in that: Drawing the melting curve specifically involves analyzing the entire melting process of the direct reduced iron pellets by drawing the melting curve; The evaluation method also The method comprises the following steps: optimizing and adjusting the parameters of direct reduced iron pellets through an evaluation system; The parameters include influencing factors.

10. The evaluation method according to claim 9, characterized in that: The optimization and adjustment method includes adjusting the temperature parameters of the constant temperature section of the tubular furnace for preparing the direct reduced iron pellets, thereby optimizing and adjusting the parameters of the direct reduced iron pellets; The constant temperature section includes a preheating section and / or a central high temperature section.

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