A calculation method for the in-furnace utilization rate of pulverized coal injected into a blast furnace

Abstract

The present invention discloses a calculation method for the in-furnace utilization rate of pulverized coal injected into a blast furnace. By means of coal petrography, the specific surface area content of coke, transitional components, and the specific surface area content of unburned pulverized coal in blast furnace gas ash are analyzed. Based on relevant calculations, the actual utilization situation of pulverized coal injected into the blast furnace in the furnace is clarified, so as to provide a technical reference for scientifically and reasonably adjusting the structure of blended coal injected into the blast furnace.

Description

Technical Field

[0001] The invention relates to the technical field of coal injection technology for iron-making blast furnaces, and in particular to a method for calculating the utilization rate of coal powder injected into a blast furnace. Background Art

[0002] As the steel industry gradually enters the era of low profits, cost competition among enterprises has become increasingly fierce, and blast furnace coal injection is one of the important measures to optimize the blast furnace fuel structure and reduce the consumption of raw fuel. Therefore, how to ensure the full combustion of pulverized coal in the blast furnace tuyere whirlpool area and replace sufficient coke with a certain replacement ratio has become the focus of current technical personnel.

[0003] The destination of coal powder after entering the blast furnace can be divided into two parts: most of it is effectively utilized in the blast furnace, including unburned coal powder that is burned in front of the tuyere and utilized in the furnace; a small part is unburned coal powder that escapes from the furnace and is not utilized. If the blast furnace only blindly increases the injection volume, it is impossible to ensure that the coal powder has a high utilization rate in the furnace. At the same time, if a large amount of unburned coal powder is generated in the furnace, it will not only affect the stability of the blast furnace, but also greatly reduce the effect of reducing the cost of blast furnace coal injection. Based on the above problems, the present invention combines actual on-site production with theoretical calculations, and uses coal petrographic phases, chemical analysis and other inspection methods to explore the quality of unburned coal powder in the blast furnace, thereby providing data reference for optimizing the mixed coal structure. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the utilization rate of pulverized coal injected into a blast furnace. The technical problem to be solved is to use coal petrographic means to analyze the specific surface area content of coke, transition components, specific surface area content of unburned coal powder in blast furnace gas ash, etc., and clarify the actual utilization of pulverized coal injected into the blast furnace in the furnace based on relevant calculations, so as to provide a technical reference for adjusting the mixed coal structure in a scientific and reasonable manner.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for calculating the utilization rate of pulverized coal injected into a blast furnace according to the present invention comprises the following steps:

[0007] (1) Select the blast furnace to be analyzed. At least reserve the gravity ash, cyclone ash, and bag filter ash of this blast furnace as sample specimens, and conduct maceral analysis on the above samples. At least focus on determining the specific surface area content of coke, transition components, the specific surface area content of unburned pulverized coal, and the specific surface area content of minerals and impurities. Among them, the tissue types in the specific surface area content of coke include anisotropy, flow structure, flaky structure, coarse-grained mosaic structure, and residual carbon particles; the tissue types in the transition components include medium-grained mosaic structure; the tissue types in the specific surface area content of unburned pulverized coal include slightly deformed coal particles, fragment structure, fine-grained mosaic structure, and deformed particles; the tissue types in the specific surface area content of minerals and impurities include ash slag, iron, and translucent slag.

[0008] (2) Determine the fluctuation range of the area proportion of coke and unburned pulverized coal through the above data. Taking the gravity ash of this blast furnace as an example, the lower limit of the area proportion of coke in the gravity ash is the sum of the tissue types in the specific surface area content of coke, and the upper limit is the sum of the specific surface area content of coke and the tissue types in the transition components; the lower limit of the area proportion of unburned pulverized coal is the sum of the tissue types in the specific surface area content of unburned pulverized coal, and the upper limit is the sum of the specific surface area content of unburned pulverized coal and the tissue types in the transition components; the calculation methods for cyclone ash and bag filter ash are the same as above.

[0009] (3) Calculate the amounts of gravity ash, cyclone ash, and bag filter ash produced per ton of iron based on the daily iron production and daily gas ash production of this blast furnace. Combine the chemical composition analysis of gravity ash, cyclone ash, and bag filter ash to obtain the C content components of the three types of ash, and calculate the carbon mass per ton of iron in the three types of ash based on the ash production per ton of iron.

[0010] (4) Based on the area proportion of coke and unburned pulverized coal calculated in step (1), obtain the upper and lower limits of the mass of coke and unburned pulverized coal in the three types of ash. Generally, the distribution ratio of unburned pulverized coal in gas ash and slag is 3:7. Further obtain the total upper and lower limits of unburned pulverized coal in gas ash and slag. The subsequent calculation is based on the following calculation formula:

[0011] Upper limit of injection coal utilization rate:

[0012] Lower limit of injection coal utilization rate:

[0013] Where: C Coal is the coal ratio of injection coal in the blast furnace, kg / t·HM;

[0014] CMax Dust is the maximum value of unburned pulverized coal in gas ash, kg / t·HM;

[0015] CMin Dust is the minimum value of unburned pulverized coal in gas ash, kg / t·HM;

[0016] CMax Slag is the maximum value of unburned coal powder in blast furnace slag, kg / t·HM;

[0017] CMin Slag is the minimum value of unburned coal powder in blast furnace slag, kg / t·HM.

[0018] The upper and lower limits of the utilization rate of pulverized coal injection in the blast furnace, that is, the pulverized coal utilization range, are obtained.

[0019] Furthermore, in step (2), since the calculation part does not take into account the specific surface area content of minerals and impurities, the above calculation is weighted and regressed to 100%.

[0020] Compared with the prior art, the beneficial technical effects of the present invention are:

[0021] The present invention uses coal petrographic means to analyze the specific surface area content of coke, transition components, specific surface area content of unburned coal powder in blast furnace gas ash, and clarifies the actual utilization of blast furnace pulverized coal injection in the furnace based on relevant calculations, thereby providing a scientific and reasonable technical reference for adjusting the mixed coal structure. DETAILED DESCRIPTION

[0022] A method for calculating the utilization rate of pulverized coal injection in a blast furnace, including:

[0023] 1. Calculation of the lower limit of coke and unburned coal powder in blast furnace gas ash;

[0024] 2. Calculation of the mass of unburned coal powder. Specific implementation method:

[0026] Select the blast furnace to be analyzed, and at least prepare the blast furnace gravity ash, cyclone ash, bag ash and other samples, conduct coal petrographic analysis on the above samples, and at least focus on exploring the coke specific surface area content, transition components, unburned coal powder specific surface area content, mineral and impurity specific surface area content, etc. Among them, the tissue types in the coke specific surface area content include various phase anisotropy, flow structure, flaky structure, coarse-grained mosaic structure, residual carbon particles, etc.; the tissue types in the transition components include medium-grained mosaic structure; the tissue types in the unburned coal powder specific surface area content include slightly altered coal particles, broken structure, microparticle mosaic structure, deformed particles, etc.; the tissue types in the mineral and impurity specific surface area content include ash slag, iron, translucent slag, etc.

[0027] Based on the above data, clarify the fluctuation range of the area ratios of coke and unburned pulverized coal. Taking the BF gravity ash as an example, the lower limit of the coke area ratio in the gravity ash is the sum of the specific surface area contents of each tissue type in the coke, and the upper limit is the sum of the specific surface area content of the coke and the specific surface area contents of each tissue type of the transition components; the lower limit of the unburned pulverized coal area ratio is the sum of the specific surface area contents of each tissue type in the unburned pulverized coal, and the upper limit is the sum of the specific surface area content of the unburned pulverized coal and the specific surface area contents of each tissue type of the transition components. The calculation methods for the cyclone ash and the bag filter ash are the same as above. Since the specific surface area contents of minerals and impurities are not considered in this calculation part, the above calculation needs to be weighted and regressed to 100%.

[0028] Based on the daily iron output and daily gas ash output of this BF, calculate the amounts of gravity ash, cyclone ash, and bag filter ash produced per ton of iron. Combining the chemical composition analysis of the gravity ash, cyclone ash, and bag filter ash, obtain the C content components of the three types of ash. Calculate the carbon mass per ton of iron for the 3 types of ash based on the ash output per ton of iron.

[0029] Based on the area ratio situation of coke and unburned pulverized coal calculated in the first step, obtain the upper and lower limits of the coke and unburned pulverized coal masses in the 3 types of ash. Generally, the distribution ratio of unburned pulverized coal in the gas ash and slag is 3:7. Obtain the total upper and lower limits of unburned pulverized coal in the gas ash and slag. Subsequently, according to the following calculation formula:

[0030] Upper limit of injection coal utilization rate:

[0031] Lower limit of injection coal utilization rate:

[0032] In the formula: C Coal is the injection coal ratio of the BF, kg / t·HM;

[0033] CMax Dust is the maximum value of unburned pulverized coal in the gas ash, kg / t·HM;

[0034] CMin Dust is the minimum value of unburned pulverized coal in the gas ash, kg / t·HM;

[0035] CMax Slag is the maximum value of unburned pulverized coal in the BF slag, kg / t·HM;

[0036] CMin Slag is the minimum value of unburned pulverized coal in the BF slag, kg / t·HM.

[0037] Obtain the upper and lower limits of the utilization rate of the injection pulverized coal in the BF, that is, the pulverized coal utilization interval.

[0038] Case

[0039] The petrographic analysis results of the gas ash from a certain blast furnace of Baotou Steel are shown in Table 1. It is generally believed that the medium-grained mosaic structure may come from either coke or pulverized coal. Therefore, based on the uncertainty of the medium-grained mosaic structure, the upper and lower limits of the coke and unburned pulverized coal contents can be calculated. The specific results are shown in Table 2.

[0040] Table 1 Petrographic analysis of gravity ash, cyclone ash and bag filter ash

[0041]

[0042] Table 2 Fluctuation range of area ratios of coke and unburned pulverized coal in the gas ash of a certain blast furnace (%)

[0043]

[0044] According to the calculation results in Table 2, the conversion results of the area ratios of coke and unburned pulverized coal regressing to 100% are deduced, and the upper and lower limits of the obtained fluctuation intervals are shown in Table 3.

[0045] Table 3 Conversion results of the area ratios of coke and unburned pulverized coal regressing to 100% (%)

[0046]

[0047] According to the daily output of the blast furnace per ton of iron and the daily output of gas ash, the generation amounts of gravity ash, cyclone ash and bag filter ash per ton of iron of this blast furnace are calculated. As shown in Table 4.

[0048] Table 4 Output per ton of iron of gravity ash, cyclone ash and bag filter ash of a certain blast furnace

[0049]

[0050] Then, combined with the results in Table 3, the upper and lower limits of the generation amounts of coke and unburned pulverized coal in the gas ash per ton of iron are calculated. As shown in Table 5.

[0051] Table 5 Fluctuation range of carbon content per ton of iron and contents of coke and unburned pulverized coal in gas ash

[0052]

[0053] It can be seen from Table 5 that the C content in the gas ash is above 35%, and the carbon content in the gas ash per ton of iron is calculated to be above 1 kg / t. This indicates that the pulverized coal utilization rate inside this blast furnace is not very ideal. Subsequently, based on the distribution ratio of 3:7 for the unburned pulverized coal in the blast furnace dust removal ash and the unburned pulverized coal carried away by the slag, the mass distribution of the unburned pulverized coal in this blast furnace is calculated. See Table 6 for details.

[0054] Table 6 Mass distribution of unburned pulverized coal (kg)

[0055]

[0056] Then, according to the calculation formula for the utilization efficiency of pulverized coal injected into the blast furnace, the actual utilization of pulverized coal in front of the tuyere of this blast furnace is calculated. The results are shown in Table 7. It can be seen from Table 7 that the control range of the pulverized coal utilization rate of this blast furnace is 79.46 - 89.03%.

[0057] Table 7 Pulverized coal injection ratio and utilization rate of pulverized coal in front of the tuyere of a certain blast furnace (%)

[0058]

[0059] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for calculating the utilization rate of pulverized coal injection in a blast furnace. Features: The steps include: (1) Select a blast furnace to be analyzed, and take at least the gravity ash, cyclone ash, and bag ash of the blast furnace as test samples, and perform coal petrographic analysis on the above samples, at least focusing on the coke specific surface area content, transition components, unburned coal powder specific surface area content, and mineral and impurity specific surface area content; wherein the organizational types in the coke specific surface area content include various phase anisotropy, flow structure, lamellar structure, coarse-grained mosaic structure, and residual carbon particles; the organizational types in the transition components include medium-grained mosaic structure; the organizational types in the unburned coal powder specific surface area content include slightly altered coal particles, broken fragment structure, microparticle mosaic structure, and deformed particles; the organizational types in the mineral and impurity specific surface area content include ash slag, iron, and translucent slag; (2) The fluctuation range of the area ratio of coke and unburned coal powder is clarified through the above data. Taking the gravity ash of the blast furnace as an example, the lower limit of the area ratio of coke in the gravity ash is the sum of the various tissue types in the coke specific surface area content, and the upper limit is the sum of the coke specific surface area content and the various tissue types of the transition components; the lower limit of the area ratio of unburned coal powder is the sum of the various tissue types in the unburned coal powder specific surface area content, and the upper limit is the sum of the unburned coal powder specific surface area content and the various tissue types of the transition components; the calculation method of cyclone ash and bag ash is the same as above; (3) Based on the daily iron production and daily gas ash production of the blast furnace, the amount of gravity ash, cyclone ash and bag ash produced per ton of iron is calculated. Combined with the chemical composition analysis of gravity ash, cyclone ash and bag ash, the carbon content of the three types of ash is obtained. Based on the ash production per ton of iron, the carbon content of the three types of ash per ton of iron is calculated; (4) Based on the area ratio of coke and unburned coal powder calculated in step (1), the upper and lower limits of the mass of coke and unburned coal powder in the three types of ash are obtained. In general, the ratio of unburned coal powder in gas ash and slag is 3:

7. Further, the total upper and lower limits of unburned coal powder in gas ash and slag are obtained. Subsequent calculations are based on the following calculation formula: Upper limit of pulverized coal utilization rate: Lower limit of pulverized coal injection utilization rate: Where: C Coal is the pulverized coal injection rate in the blast furnace, kg / t·HM; CMax Dust is the maximum value of unburned coal dust in gas ash, kg / t·HM; CMin Dust is the minimum value of unburned coal dust in gas ash, kg / t·HM; CMax Slag is the maximum value of unburned coal powder in blast furnace slag, kg / t·HM; CMin Slag is the minimum value of unburned coal powder in blast furnace slag, kg / t·HM; The upper and lower limits of the utilization rate of pulverized coal injection in the blast furnace, that is, the pulverized coal utilization range, are obtained.

2. The method for calculating the utilization rate of pulverized coal injection in a blast furnace according to claim 1, Features: In step (2), since the specific surface area content of minerals and impurities is not taken into account in the calculation part, the above calculation is weighted and regressed to 100%.

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