Smelting method for improving gas utilization efficiency under high pressure difference operation of blast furnace

Abstract

The invention discloses a smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace. The method comprises the following steps: increasing the coke load fed into the furnace by charging at the furnace top; controlling the weight O / C in a range of 5.0-6.2 t / t; controlling the minimum coke distribution angle in a range of 25-30 degrees; adopting a distribution matrix from an outer ring to an inner ring; when the blast furnace slag skin thickness is appropriate and the furnace type is uniform, smelting is performed according to the parameters of actual wind speed ≥ 280 m / s and blast kinetic energy ≥ 150 KJ / s; gradually increasing the pressure difference in the furnace by increasing the air volume, and dynamically adjusting the pressure difference according to the static pressure on the upper part of the furnace body and the actual wind speed, controlling the stable mean value of the pressure difference in the blast furnace to be within the range of 185-250 KPa, and the fluctuation range of the instantaneous pressure difference in normal smelting is ±5% of the stable mean value of the pressure difference; the invention realizes improving the gas utilization rate and realizing high-yield and low-consumption smelting by maintaining the appropriate slag skin thickness of the furnace body and the circumferential uniformity of the furnace body, increasing the actual wind speed of the blast furnace, increasing the coke load, and increasing the pressure difference in the furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace. Background Art

[0002] my country's steel industry accounts for about 23% of total industrial energy consumption, 16% of the country's total energy consumption, and about 17% of the country's total pollutant emissions. It is a key industry for the country to promote energy conservation and emission reduction. In 2019, the Ministry of Ecology and Environment, the National Development and Reform Commission, the Ministry of Industry and Information Technology and other five ministries and commissions jointly issued the "Opinions on Promoting the Implementation of Ultra-low Emissions in the Steel Industry", which put forward requirements for ultra-low emission indicators in the steel industry. Due to the environmental protection of blast furnaces and the country's strict control over the construction of new blast furnaces, blast furnace output is basically the bottleneck of the production lines of various steel companies.

[0003] At present, steel enterprises will not be able to add new process equipment, but at the same time, with the rapid development of my country's economy, the demand for steel products for different purposes is also increasing day by day. In order to meet the rapidly growing needs of different industries for steel products, steel enterprises need to use existing equipment conditions and fully tap their own capabilities to cope with the growing market demand. As for the ironmaking process, the increase in production capacity, under the condition that new blast furnaces cannot be built, means that the production capacity must be increased, that is, the smelting intensity of blast furnaces must be increased accordingly to meet the needs of expanding production capacity.

[0004] For blast furnace ironmaking, increasing the pressure difference in the blast furnace under acceptable conditions can increase production. It is generally believed that 2000-3000m 3 For blast furnaces, every increase of 5KPa in pressure difference can increase the air volume by 100m 3 / min, increasing output by 140-150t / d. Therefore, without building a new blast furnace, the existing blast furnace can increase the output of molten iron by increasing the pressure difference.

[0005] However, increasing the pressure difference will make the blast furnace unloading worse, resulting in slipping, collapse and even hanging materials, causing large fluctuations in airflow, destroying the stability and smoothness of the blast furnace, and worsening the working state of the furnace in severe cases, causing damage to the tuyere, which is not conducive to the stable distribution of coal gas. If it is not well controlled, it is very easy to form pipelines. The frequent shedding of copper cooling wall slag is not conducive to the formation of a regular operating furnace type, resulting in thickening of the blast furnace body. The thickening of the furnace body will restrict the increase of wind speed and kinetic energy, which is not conducive to the activity of the furnace, and seriously affects the ability of the blast furnace to accept the pressure difference. Limited by natural resources and technical conditions, my country will continue to use blast furnace ironmaking technology to produce pig iron for a considerable period of time in the future. Therefore, blast furnace ironmaking technology will still be dominant in ironmaking production. However, due to the shortage of coke resources across the country, blast furnace production is currently under tremendous pressure from investment, resources, costs, environmental protection and other aspects.

[0006] my country has put into production 4000m 3 There are 19 large blast furnaces with large differences in operation indicators. Taking the data from 2013 as an example, the blast furnace utilization coefficient is 1.805~2.487t / m 3 .d, average 2.148t / m 3 .d, which has reached the international advanced level; and the fuel ratio is 486.49-568.26kg / t, with an average of 509.80kg / t, which is 40-50kg / t higher than the international advanced level (the fuel ratio of advanced blast furnaces in Europe is 460-470kg / t). In 2013, the total pig iron output of these 18 large blast furnaces was 59.587 million tons. If the average fuel ratio is reduced to 500kg / t (a reduction of about 10kg / t), the fuel consumption will be reduced by 595,000 tons per year.

[0007] Fuel ratio is the largest part of process energy consumption. In 2019, the domestic energy consumption was 2000-3000m 3 Fuel ratio of blast furnace 519kg / t, 3000m 3 Grade blast furnace 514kg / t, 4000m 3 The main reason for the high fuel ratio of domestic blast furnaces is the unreasonable distribution of coal gas flow in the blast furnace and the low efficiency of coal gas utilization. In 2020, the average coal gas utilization rate of the blast furnace of a certain ironmaking plant in central China was only 46.59%, and the coal gas utilization rate was unstable, resulting in a high fuel ratio in the blast furnace production process. The fuel ratio of the plant in 2020 was 515.8Kg / t.Fe, which affected the cost of molten iron and smelting efficiency.

[0008] In view of this, under the premise of not building new blast furnaces and utilizing existing blast furnace ironmaking equipment, how to optimize the gas flow distribution in the blast furnace by increasing the pressure difference in the furnace, improve the gas utilization efficiency, and achieve high-yield and low-consumption blast furnace ironmaking has become an urgent problem to be solved. Summary of the invention

[0009] The purpose of the present invention is to provide a smelting method for improving the gas utilization efficiency under the high pressure difference operation of the blast furnace, by maintaining the appropriate slag skin thickness of the furnace body and the circumferential uniformity of the furnace body, increasing the actual wind speed of the blast furnace, increasing the coke load, and increasing the pressure difference in the furnace, so as to improve the gas utilization rate and achieve high-yield and low-consumption smelting.

[0010] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0011] A smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace, comprising the following steps:

[0012] (1) Increase the coke load into the furnace by charging the furnace top; the weight O / C control range is 5.0~6.2t / t;

[0013] (2) Use a distribution matrix that suppresses the center and stabilizes the edge to control the minimum coke distribution angle range to 25-30°; adopt a distribution matrix from the outer ring to the inner ring: or or Where C is coke, O is sintered ore + pelletized ore + lump ore, the upper right number is the distribution angle, and the lower right number is the number of distribution rings corresponding to the upper right number;

[0014] (3) When the blast furnace slag skin thickness is appropriate and the furnace shape is uniform, smelting is carried out according to the parameters of actual wind speed ≥ 280m / s and blast kinetic energy ≥ 150KJ / s;

[0015] (4) The pressure difference in the furnace is gradually increased by increasing the air volume. At the same time, the pressure difference is dynamically adjusted according to the static pressure on the upper part of the furnace body and the actual wind speed. The stable average pressure difference of the blast furnace is controlled within the range of 185-250 KPa. The fluctuation range of the instantaneous pressure difference during normal smelting is ±5% of the stable average pressure difference.

[0016] According to the above scheme, the appropriate thickness of the blast furnace slag skin means that the temperature detection value of the cooling wall in the blast furnace waist, the lower and middle parts of the furnace body and the middle part of the furnace body has an appropriate difference with the cooling water inlet temperature; specifically, when the copper cooling wall is used in the furnace waist, the lower and middle parts of the furnace body and the middle part of the furnace body, the temperature difference range is 5 to 15°C; when the cast iron or cast steel cooling wall is used in the middle part of the furnace body, the temperature difference range is 40 to 60°C.

[0017] According to the above scheme, the uniform furnace type refers to the uniform circumferential temperature of the blast furnace waist, the lower and middle parts of the furnace body, and the middle part of the furnace body; specifically, when copper cooling walls are used in the furnace waist, the lower and middle parts of the furnace body, and the middle part of the furnace body, the temperature difference range of each circumferential monitoring point is 0 to 3°C; when cast iron or cast steel cooling walls are used in the middle part of the furnace body, the temperature difference range of each circumferential monitoring point is 0 to 8°C.

[0018] According to the above scheme, in step 4, the pressure difference is increased to 185KPa at a uniform speed, and then the speed of increase from 185 to 250KPa is gradually reduced. The process of increasing the pressure difference keeps the blast furnace unloading smooth.

[0019] According to the above scheme, dynamically adjusting the pressure difference according to the static pressure on the upper part of the furnace body and the actual wind speed in step 4 includes the following steps:

[0020] When the multi-point static pressure trend curves on the upper part of the furnace are concentrated and the actual wind speed increases, continue to increase the air volume to increase the pressure difference; when the multi-point static pressure trend curves are dispersed or the actual wind speed decreases, stop increasing the air volume, and at the same time take one or more measures such as reducing the air volume to reduce the pressure difference or adjusting the distribution system or adjusting the coke load until the multi-point static pressure trend curves on the upper part of the furnace are concentrated again.

[0021] According to the above scheme, the pellets are Ezhou pellets and / or Chengchao pellets, and the lump ore is Australian lump and / or South African lump.

[0022] According to the above scheme, the static pressure on the upper part of the furnace body refers to the static pressure monitoring value of the 13th section of the blast furnace.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention increases the actual wind speed and kinetic energy of the blast furnace, increases the pressure difference range accepted by the blast furnace to 185-250KPa by increasing the coke load and reducing the central coke amount, and dynamically adjusts the pressure difference, thereby increasing the molten iron output of the blast furnace, and overcoming the problems of deep central material surface and periodic material sliding to the center caused by high pressure difference operation with large kinetic energy of blast, strong central airflow, and fast consumption of central material column. At the same time, the upper charging matrix is ​​optimized, which not only ensures the balance of the material surface, but also adjusts the distribution of the edge and central gas flow, prolongs the residence time of the gas in the furnace, improves the utilization efficiency of the blast furnace gas, and reduces the energy consumption of the blast furnace. DETAILED DESCRIPTION

[0025] The following examples further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0026] A specific embodiment provides a smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace, comprising:

[0027] (1) Increase the coke load into the furnace by charging the furnace top; the weight O / C control range is 5.0~6.2t / t;

[0028] (2) Use a distribution matrix that suppresses the center and stabilizes the edge to control the minimum coke distribution angle range to 25-30°; adopt a distribution matrix from the outer ring to the inner ring: or or Where C is coke, O is sintered ore + pelletized ore + lump ore, the upper right number is the distribution angle, and the lower right number is the number of distribution rings corresponding to the upper right number;

[0029] (3) When the blast furnace slag skin thickness is appropriate and the furnace shape is uniform, smelting is carried out according to the parameters of actual wind speed ≥ 280m / s and blast kinetic energy ≥ 150KJ / s;

[0030] (4) The pressure difference in the furnace is gradually increased by increasing the air volume. At the same time, the pressure difference is dynamically adjusted according to the static pressure on the upper part of the furnace body and the actual wind speed. The stable average pressure difference of the blast furnace is controlled to be within the range of 185-250KPa. The fluctuation range of the instantaneous pressure difference during normal smelting is ±5% (relative to the stable average pressure difference).

[0031] Specifically, the appropriate thickness of the blast furnace slag skin means that the temperature detection value of the cooling wall of the blast furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body has an appropriate difference with the cooling water inlet temperature; specifically, when the furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body use copper cooling walls, the temperature difference range is 5 to 15°C; when the middle part of the furnace body uses cast iron or cast steel cooling walls, the temperature difference range is 40 to 60°C.

[0032] Specifically, the uniform furnace type refers to the uniform circumferential temperature of the blast furnace waist, the lower and middle parts of the furnace body, and the middle part of the furnace body; specifically, when copper cooling walls are used in the furnace waist and the lower and middle parts of the furnace body, the temperature difference range of each circumferential monitoring point is 0 to 3°C; when cast iron or cast steel cooling walls are used in the middle part of the furnace body, the temperature difference range of each circumferential monitoring point is 0 to 8°C.

[0033] Specifically, in step 4, when the blast furnace is in good condition, the pressure difference in the furnace is gradually increased by increasing the air volume, and the pressure difference is increased to 185KPa at a uniform speed, and then the speed of increasing from 185 to 250KPa is gradually reduced, and the process of increasing the pressure difference keeps the blast furnace unloading smooth. If necessary, the strategy of "two steps forward and one step back" can be adopted until the goal of increasing the pressure difference to the established level is achieved.

[0034] Specifically, dynamically adjusting the pressure difference in step 4 includes:

[0035] When the multi-point static pressure trend curves on the upper part of the furnace are concentrated and the actual wind speed increases, continue to add air to increase the pressure difference; when the multi-point static pressure trend curves are dispersed or the actual wind speed decreases, stop adding air to increase the pressure difference, and at the same time take appropriate measures to reduce the pressure difference or adjust the distribution system or adjust the coke load, one or more of them, until the multi-point static pressure trend curves on the upper part of the furnace are concentrated again.

[0036] Specifically, the pelletized ore is Ezhou pelletized ore and / or Chengchao pelletized ore, and the lump ore is Australian lump and / or South African lump.

[0037] Specifically, the static pressure on the upper part of the furnace body refers to the static pressure monitoring value of the 13th section of the blast furnace.

[0038] Comparative Example 1

[0039] Table 1 shows the status of the No. 5 blast furnace and the temperature distribution of each monitoring point in a domestic ironmaking plant. When the No. 5 blast furnace is thick, the temperature of the furnace is low and uneven. Although the pressure difference of the blast furnace is reduced to below 150KPa, the blast furnace is still in poor operation. The static pressure of each section of the furnace body is bifurcated, the material slides and collapses continuously, and the material is suspended or even malignantly suspended. In addition, the furnace hearth is not active and the tuyere is easily damaged. Based on this, the traditional view is that 2000m 3 The pressure difference of the following blast furnaces should generally be maintained below 170KPa, 2000m 3 The above blast furnace pressure difference should generally be maintained below 180KPa.

[0040] Table 1 The status of the No. 5 blast furnace and the temperature distribution of each monitoring point in a domestic ironmaking plant

[0041]

[0042] Example 1

[0043] The status of blast furnace A in an iron and steel plant and the temperature distribution of each monitoring point (Table 2).

[0044] Table 2 The status of the blast furnace A in a domestic ironmaking plant and the temperature distribution of each monitoring point

[0045]

[0046] Adjust the air inlet area according to the actual air volume of the blast furnace, and smelt according to the actual wind speed of 288m / s and the blast kinetic energy ≥153KJ / s.

[0047] The average batch weight of the selected ore is 95,000 kg / batch, the average batch weight of coke is 19,000 kg / batch, and the coke load (weight O / C) into the furnace is 5.0 t / t.

[0048] The blast furnace adopts a distribution matrix from the outer ring to the inner ring, and the charging matrix is: Among them, C is coke, O is sintered ore + pelletized ore + lump ore, the upper right number is the distribution angle, the lower right number is the distribution ring number corresponding to the upper right number, and the coke distribution angle No. 4 is selected as 28°.

[0049] When the blast furnace is in good condition, the pressure difference in the furnace is gradually increased by increasing the air volume. The pressure difference increases uniformly from 165KPa to 185KPa. At the same time, on the premise that the static pressure trend curves at multiple points on the upper part of the furnace body are not dispersed and the actual wind speed is not decreased, the average pressure difference is slowly increased to 232KPa at the rate of an arithmetic progression. The instantaneous value of the pressure difference during normal smelting is relatively stable, and the fluctuation range of the average is ±3%.

[0050] The results show that the pressure difference of the blast furnace of the present invention is increased to 232KPa, and the utilization coefficient is 3.55t / m 3 .d, the gas utilization efficiency is increased to 52.8%, the fuel ratio is as low as 475.6kg / t, and the blast furnace achieves high output and low fuel consumption.

[0051] Example 2

[0052] The status of the blast furnace B in an iron and steel plant and the temperature distribution of each monitoring point (Table 3).

[0053] Table 3 The status of the blast furnace B in a domestic ironmaking plant and the temperature distribution of each monitoring point

[0054]

[0055] Adjust the air inlet area according to the actual air volume of the blast furnace, and smelt at the actual wind speed of 290m / s and blast kinetic energy ≥155KJ / s.

[0056] The average batch weight of selected ore is 98,000 kg / batch, the average batch weight of coke is 15,800 kg / batch, and the coke load (weight O / C) entering the furnace is 6.2 t / t.

[0057] The blast furnace adopts a distribution matrix from the outer ring to the inner ring, and the charging matrix is: Among them, C is coke, O is sintered ore + pelletized ore + lump ore, the upper right number is the distribution angle, the lower right number is the distribution ring number corresponding to the upper right number, and the coke distribution angle No. 4 is selected as 30°.

[0058] When the blast furnace is in good condition, the pressure difference in the furnace is gradually increased by increasing the air volume. The pressure difference increases uniformly from 165KPa to 185KPa. At the same time, on the premise that the static pressure trend curves at multiple points on the upper part of the furnace body are not dispersed and the actual wind speed does not decrease, the average pressure difference is slowly increased to 240KPa at the rate of an arithmetic progression. The instantaneous value of the pressure difference during normal smelting is relatively stable, and the fluctuation range of the average is ±3%.

[0059] The results show that the pressure difference of the blast furnace of the present invention is increased to 240KPa, and the utilization coefficient is 3.62t / m 3 .d, the gas utilization efficiency is increased to 51.3%, the fuel ratio is as low as 482.1kg / t, and the blast furnace achieves high output and low fuel consumption.

Claims

1. A smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace, characterized in that The following steps are involved: (1) Increase the coke load into the furnace by charging the furnace top; the weight O / C control range is 5.0~6.2t / t; (2) Use a distribution matrix that suppresses the center and stabilizes the edge to control the minimum coke distribution angle range to 25-30°; adopt a distribution matrix from the outer ring to the inner ring: or or , where C is coke, O is sintered ore + pelletized ore + lump ore, the upper right number is the distribution angle, and the lower right number is the number of distribution rings corresponding to the upper right number; (3) When the blast furnace slag skin thickness is appropriate and the furnace shape is uniform, smelting is carried out according to the parameters of actual wind speed ≥ 280m / s and blast kinetic energy ≥ 150J / s; the appropriate blast furnace slag skin thickness refers to the appropriate difference between the temperature detection value of the cooling wall in the blast furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body and the cooling water inlet temperature; specifically, when the furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body adopt copper cooling walls, the temperature difference range is 5-15℃; when the middle part of the furnace body adopts cast iron or cast steel cooling walls, the temperature difference range is 40-60℃; the uniform furnace shape refers to the circumferential temperature of the blast furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body is uniform; specifically, when the furnace waist, the middle and lower part of the furnace body and the middle part of the furnace body adopt copper cooling walls, the temperature difference range of each circumferential monitoring point is 0-3℃; when the middle part of the furnace body adopts cast iron or cast steel cooling walls, the temperature difference range of each circumferential monitoring point is 0-8℃; (4) The pressure difference in the furnace is gradually increased by increasing the air volume. At the same time, the pressure difference is dynamically adjusted according to the static pressure on the upper part of the furnace body and the actual wind speed. The stable average pressure difference of the blast furnace is controlled within the range of 185-250 kPa. The fluctuation range of the instantaneous pressure difference during normal smelting is ±5% of the stable average pressure difference.

2. The smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace as claimed in claim 1, characterized in that Step (4) uniformly increases the pressure difference to 185 kPa, and then gradually decreases the speed of increasing the pressure difference from 185 to 250 kPa. The process of increasing the pressure difference keeps the blast furnace unloading smooth.

3. The smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace as claimed in claim 1, characterized in that In step (4), dynamically adjusting the pressure difference according to the static pressure on the upper part of the furnace body and the actual wind speed includes the following steps: When the multi-point static pressure trend curves on the upper part of the furnace are concentrated and the actual wind speed increases, continue to increase the air volume to increase the pressure difference; when the multi-point static pressure trend curves are dispersed or the actual wind speed decreases, stop increasing the air volume, and at the same time take one or more measures such as reducing the air volume to reduce the pressure difference or adjusting the distribution system or adjusting the coke load until the multi-point static pressure trend curves on the upper part of the furnace are concentrated again.

4. The smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace as claimed in claim 1, characterized in that The pellets are Ezhou pellets and / or Chengchao pellets, and the lump ore is Australian lump and / or South African lump.

5. The smelting method for improving gas utilization efficiency under high pressure difference operation of a blast furnace as claimed in claim 1, characterized in that The static pressure on the upper part of the furnace body in step (4) refers to the static pressure monitoring value of the 13th section of the blast furnace.

Images