A method for converting the operation of a blast furnace from dry quenching to water quenching

Abstract

This invention relates to the field of metal smelting technology and discloses a method for switching between dry quenching and water quenching in a blast furnace. The steps are as follows: S1. Calculate the weight of each batch of water-quenched coke: Calculate the weight Mn of water-quenched coke based on the moisture change value of dry quenching and water-quenching, the batch weight of ore, and the batch weight of dry quenching; S2. Verify the batch weight of ore and the batch weight of water-quenched coke: Based on the furnace top gas temperature loss coefficient α during each batch of water quenching, the weight of each batch of water-quenched coke needs to be reduced by Mn*α, resulting in the weight of each batch of water-quenched coke being Mn-Mn*α. Based on the coke load R, the corresponding batch weight of ore is (Mn-Mn*α)*R; S3. Adjust the feeding angle and number of feeding rings of ore, coke, and water-quenched coke; S4. If the furnace top gas temperature drops significantly, reduce the batch weight of ore and water-quenched coke to maintain a stable furnace top gas temperature. This invention addresses the changing moisture content of water-quenched coke by operating the water-quenched coke in a gradient manner, thereby stabilizing the gas flow distribution during the water-quenched coke process and ensuring smooth operation of the blast furnace.

Description

Technical Field

[0001] This invention relates to the field of metal smelting technology, and more specifically, to a method for switching between dry quenching and water quenching operations in a blast furnace. Background Technology

[0002] Coke is the core fuel for blast furnace smelting. In the blast furnace smelting process, coke plays three key roles: first, as fuel to generate heat through combustion; second, as a skeleton material to support the weight of the entire furnace charge in the blast furnace during the smelting process, ensuring that the furnace charge inside the blast furnace decreases reasonably as the ore melts and is reduced during the smelting process; and third, as a carburizing agent to provide carbon elements in the carburizing process during the smelting process.

[0003] Currently, blast furnace smelting primarily uses dry quenching, with a small amount using water quenching. However, when the dry quenching system malfunctions, the blast furnace is forced to switch to water quenching. Therefore, the use of water quenching is a problem faced by every blast furnace.

[0004] Water quenching is the process of cooling high-temperature red-hot coke by spraying water. Nowadays, environmental protection management at the production site is very strict. In order to avoid dust from dry quenching and to prevent accidents such as fires caused by high coke temperature during belt conveying, coupled with the difference in the control level of personnel from each shift, the amount of water sprayed varies, making it difficult to control the water content of water quenching coke stably. It generally fluctuates in the range of 3-20%.

[0005] During the use of water-quenched coke in blast furnaces, different operators employ significantly different methods. In most blast furnaces, the appropriate amount of coke is added based on the water content of the water-quenched coke. This addition increases the weight and volume of each batch of coke, causing changes in the gas flow distribution within the blast furnace, leading to decreased gas utilization and increased fuel consumption. Furthermore, the changes in the weight and volume of the added coke inevitably alter its distribution as it is fed into the blast furnace from the top of the feeder. The increased bulk density of the water-quenched coke, especially when it is tilted and rotated along the feeder chute, further complicates the process. During the feeding process, the trajectory of the water-quenched coke changes, while the trajectory of the ore feeding remains unchanged. This leads to changes in the stratified distribution of ore and coke inside the blast furnace, causing fluctuations in furnace conditions. After the water-quenched coke is placed in the top area of ​​the blast furnace, the temperature of the gas at the top reaches about 150°C. Most of the moisture inside the water-quenched coke is evaporated under the baking of the gas temperature. The heat consumption of the water vapor causes the temperature of the gas at the top to decrease. The heat of the gas at the top and the gas pressure in the space at the top will also decrease, which will inevitably lead to a reduction in the residual energy of the blast furnace gas, a significant reduction in TRT power generation, and a significant reduction in recovery efficiency.

[0006] Currently, in blast furnace operation, when the moisture content of water-quenched coke is too high, generally exceeding 10%, blast furnace operators struggle to find precise countermeasures. Most often, they resort to reducing blast and smelting intensity, inevitably leading to decreased blast furnace output and increased consumption. As the moisture content further increases, the blast furnace becomes difficult to operate, its smooth operation is affected, and various indicators gradually deteriorate. In existing technology, the transition from dry quenching to water quenching in a blast furnace relies entirely on the operator's experience, lacking standards, reference points, and coordination with blast furnace smelting parameters. This results in fluctuating airflow within the furnace during the transition, impacting blast furnace operation, consumption, and iron quality.

[0007] Therefore, it is necessary to propose a conversion operation method for blast furnaces using dry quenching and water quenching. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for switching between dry quenching and water quenching in blast furnaces. By adjusting the water quenching process according to changes in the moisture content of the coke, the method operates the water quenching process in a gradient manner, stabilizing the gas flow distribution during water quenching and ensuring smooth operation of the blast furnace.

[0009] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for switching between dry quenching and water quenching in a blast furnace, comprising the following steps: S1. Calculate the weight of each batch of water-quenched coke: Calculate the weight Mn of water-quenched coke based on the moisture change value between dry-quenched and water-quenched coke, the batch weight of ore, and the batch weight of dry-quenched coke. S2. Verify the batch weight of ore and the batch weight of water-quenched coke: Based on the temperature loss coefficient α of the furnace top gas during each batch of water-quenched coke, the weight of each batch of water-quenched coke needs to be reduced by Mn*α, so the weight of each batch of water-quenched coke is Mn-Mn*α. According to the coke load R, the corresponding batch weight of ore is (Mn-Mn*α)*R. S3. Adjust the feeding angle and number of feeding rings for ore, coke, and water-quenched coke: As the batch weight of ore and water-quenched coke decreases, adjust the feeding angle at the furnace top and the number of feeding rings corresponding to each angle. Under the original number of feeding rings for ore, calculate the weight added to each ring of ore. After the batch weight of ore decreases, ensure that the weight added to each ring of ore remains unchanged as a benchmark, calculate the number of feeding rings for ore after the batch weight of ore decreases, and adjust the number of feeding rings for water-quenched coke accordingly. The adjustment method for the number of feeding rings for coke is the same as the adjustment method for the number of feeding rings for ore. S4. After using water-quenched coke for a period of time, if the temperature of the furnace top gas drops significantly, repeat steps S1-S3 to reduce the batch weight of ore and water-quenched coke and maintain a stable furnace top gas temperature.

[0010] In one embodiment, the specific calculation method in step S1 is as follows: The change in moisture content between dry quenching and water quenching is calculated as ΔY = Yn - Y, where Yn is the moisture content of each batch of water-quenched coke entering the furnace, which is obtained through real-time online monitoring, and Y is the moisture content of dry quenching coke used in the blast furnace. Calculate the coke batch weight M2 when using dry quenching coke: M2 = M1 / R, where M1 is the ore batch weight and R is the coke load. When dry quenching coke is used, the volume occupied inside the blast furnace by the dry quenching coke batch weight M2 corresponding to the ore batch weight M1 is: V1=M2 / β1=(M1 / R) / β1, where β1 is the measured bulk density of dry quenching coke. The volume of water-quenched coke is calculated as V2 = (M2 + M2 * ΔY) / β2, where β2 is the measured bulk density of water-quenched coke; the change in coke volume during the transition from water-quenched to dry-quenched coke is obtained as ΔV = V2 - V1. Finally, the weight of each batch of water-quenched coke was calculated as Mn = (M2 + M2 * ΔY) + ΔV * β2; In one embodiment, the specific verification method in step S2 is as follows: Calculate the furnace top gas temperature loss coefficient α = (T2-T1) / T during the period of water quenching of coke for each batch, where T is the average furnace top gas temperature during the period of dry quenching of coke, T1 is the change in furnace top gas temperature as the dry quenching coke material level drops by 1 meter during the smelting process, and T2 is the change in furnace top gas temperature as the water quenching coke material level drops by 1 meter during the smelting process.

[0011] In one embodiment, in step S3, the ore angle is kept constant, and the angle of the water-quenched coke cloth is reduced based on the original cloth angle, and adjusted in a way that the maximum angle is reduced by 0.1°-0.5° and the minimum angle is increased by 0.1°-0.5°.

[0012] In one embodiment, in step S3, the angle of the water-quenched coke fabric is adjusted based on the moisture change value ΔY between dry quenching and water quenching: When ΔY < 5%, the adjustment amount is 0.1°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.1°, and the minimum fabric angle of water-quenched coke is increased by 0.1°; When 5%≤ΔY<10%, the adjustment amount is 0.2°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.2°, and the minimum fabric angle of water-quenched coke is increased by 0.2°; When 10%≤ΔY<15%, the adjustment amount is 0.3°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.3°, and the minimum fabric angle of water-quenched coke is increased by 0.3°; When 15%≤ΔY≤20%, the adjustment amount is 0.4°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.4°, and the minimum fabric angle of water-quenched coke is increased by 0.4°; When ΔY > 20%, the adjustment amount is 0.5°, which means that the maximum fabric angle of water-quenched coke is reduced by 0.5° and the minimum fabric angle of water-quenched coke is increased by 0.5°.

[0013] In summary, the present invention has the following beneficial effects: This invention can achieve a stable transition between dry quenching and water quenching, avoiding fluctuations in the airflow inside the furnace during the conversion between the two processes.

[0014] Based on this invention, the temperature of the blast furnace top gas will not decrease significantly during the use of water quenching, and the gas temperature will remain basically stable in the range of 100-130℃. This avoids the problems of low blast furnace top gas temperature, dust removal system adhesion and blockage, and reduced TRT power generation caused by the use of water quenching, which result in cost losses. Based on the method of this invention, the TRT power generation of the blast furnace is basically the same as that of dry quenching. This invention realizes the optimal mode for switching between dry quenching and water quenching. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the embodiments.

[0016] It is worth noting that the directional terms such as "up" and "down" used in this article are merely for ease of description and should not be interpreted as limitations on the technical solution.

[0017] This invention proposes a method for switching between dry quenching and water quenching in a blast furnace. It employs a gradient approach to the use of water quenching, taking into account changes in the moisture content of the water-quenched coke, to stabilize the gas flow distribution during water quenching and thus ensure smooth blast furnace operation. The specific steps of this invention are as follows: S1. Calculate the weight of each batch of water-quenched coke: Calculate the weight of each batch of water-quenched coke when switching between dry quenching and water quenching. Preferably, the present invention calculates the weight of water-quenched coke based on the moisture change value of dry quenching and water quenching, the batch weight of ore, and the batch weight of dry quenching.

[0018] During the water-quenching process in a blast furnace, the moisture content of each batch of water-quenched coke is monitored online in real time and denoted as Yn. The moisture content of each batch fluctuates dynamically. The moisture content of dry-quenched coke is denoted as Y, which is a fixed value (dry-quenched coke is not water-cooled but typically nitrogen-cooled; the internal moisture content of dry-quenched coke is generally 0-0.5%, and the presence of moisture can be measured). In this invention, the moisture content of dry-quenched coke is the moisture value measured in the last batch of dry-quenched coke. The change in moisture content between dry-quenched and water-quenched coke is ΔY = Yn - Y.

[0019] The ore batch weight when using dry quenching in a blast furnace is denoted as M1, a fixed value. The corresponding dry quenching batch weight is determined based on the coke load (R = weight of each batch of ore / weight of the corresponding batch of coke, which is the coke load), a variable value. Typically, blast furnace operation uses a fixed coke load value based on raw material conditions, adjusting the furnace temperature by injecting pulverized coal through the tuyeres. Fixing the ore and coke batch weights aims to create a stable ore-coke layer distribution within the furnace. Based on the ore batch weight M1 and the corresponding coke load when using dry quenching, the coke batch weight M2 is calculated as M1 / R. The bulk density of dry quenching is measured as β1, and the bulk density of water quenching is measured as β2; both bulk densities are obtained through on-site sampling and testing. When using dry quenching, the volume occupied by the dry quenching batch weight M2 corresponding to ore batch weight M1 inside the blast furnace is: V1 = M2 / β1 = (M1 / R) / β1.

[0020] When using water quenching, the change in moisture content of water-quenched coke compared to dry quenching is ΔY = Yn - Y. The ore batch weight is M1, and the weight of each batch of water-quenched coke increases by M2 * ΔY, resulting in an initial batch weight of water-quenched coke of M2 + M2 * ΔY. The volume of water-quenched coke is V2 = (M2 + M2 * ΔY) / β2. The change in coke volume during the conversion between water-quenched and dry quenching is calculated as ΔV = V2 - V1, and the final weight of water-quenched coke is Mn = (M2 + M2 * ΔY) + ΔV * β2.

[0021] S2. Verify the batch weight of ore with the batch weight of water-quenched coke.

[0022] The gas temperature around the edge of the furnace top and the center temperature of the furnace top charge surface can be monitored in real time. The average furnace top gas temperature during dry quenching is denoted as T. During blast furnace smelting, the minimum and maximum furnace top gas temperatures must be kept at a safe level, generally requiring a minimum gas temperature of no less than 85℃ and a maximum gas temperature of no more than 250℃. During dry quenching, any batch of dry-quenched coke is placed on the furnace top charge surface, and the change in furnace top gas temperature (T1) is measured as the dry-quenched coke charge surface descends 1 meter during the smelting process. Similarly, after the first batch of water-quenched coke enters the blast furnace top charge surface, the change in furnace top gas temperature (T2) is also measured as the water-quenched coke charge surface descends 1 meter during the smelting process (because water-quenched coke is heavy and absorbs heat after being placed on the furnace top, the temperature drop range of the furnace top gas will be larger). The furnace top gas temperature loss coefficient α = (T2 - T1) / T is calculated for each batch of water-quenched coke used. To ensure a stable furnace top gas temperature during water quenching, the weight of each batch of water-quenched coke needs to be reduced by Mn*α, resulting in the weight of each batch of water-quenched coke being Mn - Mn*α. Based on the coke load R, the corresponding ore batch weight is (Mn - Mn*α)*R. At this point, the weight of ore and water-quenched coke used in the first batch of water-quenched coke entering the furnace is determined.

[0023] Adjust the ore and coke charging angles: as the ore batch weight decreases, the water-quenched coke batch weight also decreases. The furnace top charging angle and the number of charging rings corresponding to each angle need to be adjusted.

[0024] For example, during the dry quenching process: the ore feeding angles are 40°, 39°, 38°, 37°, and 36°, which constitute 5 rings (i.e., 5 feeding angles), and the angle difference of the ore is 4°; the dry quenching feeding angles are 40.5°, 39°, 38°, 37°, 36°, and 30°, which constitute 6 rings (i.e., 6 feeding angles), and the angle difference of the coke is 10.5°; the number of feeding rings corresponding to each angle for ore and coke is 3 rings.

[0025] The method for adjusting the fabric angle is as follows: regardless of the angle, the ore angle remains unchanged, and the fabric angle of the water-quenched coke is reduced based on the original fabric angle. The adjustment is carried out by reducing the maximum angle by 0.1°-0.5° and increasing the minimum angle by 0.1°-0.5°. The adjustment amount is determined based on the value of ΔY. For ΔY within 5%, the adjustment is 0.1°; for ΔY between 5-10%, it's 0.2°; for ΔY between 10-15%, it's 0.3°; for ΔY between 15-20%, it's 0.4°; and for ΔY greater than 20%, it's 0.5°. As the moisture content of water-quenched coke further increases, the blast furnace needs to appropriately reduce the smelting intensity, blast furnace air volume, and production output according to the smelting situation. (Reducing smelting intensity is mainly achieved by reducing the blast volume. To ensure stable operation of the blast furnace during high-proportion water-quenched coke use, when the water-quenched coke moisture content exceeds 20%, the blast furnace needs to reduce the rate of descent of the top burden by reducing air volume. The adjustment method is: using a top gas temperature of no less than 90℃ as a reference standard, the air volume reduction is based on maintaining a top gas temperature of no less than 90℃.) The adjustment theory of this invention is that the density of coke increases and the falling speed increases during the feeding process of the material in the water-quenched coke.

[0026] The adjustment method for the number of charging rings is as follows: Under the original number of charging rings, based on the original weight of ore added in each ring, the standard is to maintain the same weight added in each ring after the reduction of the ore batch weight. For example, if the original ore weight is 70 tons, the charging ring number is set to 10 rings, with each ring containing 7 tons of ore. Now, using water quenching coke and reducing the ore batch weight to 68 tons, 68 / 7 = 9.71 rings, which is the total number of charging rings that needs to be adjusted. If the water quenching coke charging angle is now set to 5 levels, then the number of charging rings for each level is reset to 9.71 / 5 = 1.942 rings. The adjustment for coke is similar to that for ore. Specifically, under the original number of charging rings for coke, the original weight added in each ring of coke is calculated. After the reduction of the coke batch weight, the weight added in each ring of coke is kept constant as a benchmark, and the number of charging rings for coke after the reduction in coke batch weight is calculated. The biggest advantage of this method is that it ensures a uniform change in the thickness of the top charge layer.

[0027] S4. After adjusting as described above, if the furnace top gas temperature drops significantly after a period of water-quenched coke smelting, the batch weight of ore and water-quenched coke needs to be further reduced. The minimum weight of the reduced ore and water-quenched coke should be determined to meet the fastest feeding speed. Operating water-quenched coke according to the method of this invention can achieve a stable transition between dry and water quenching, avoiding fluctuations in the furnace airflow during the conversion process.

[0028] This invention ensures that the temperature of the blast furnace top gas does not significantly decrease during water quenching, maintaining a relatively stable temperature within the 100-130℃ range. This avoids problems such as low blast furnace top gas temperature, dust removal system blockage, and reduced TRT power generation associated with water quenching, which can lead to cost losses. Based on this method, the TRT power generation of the blast furnace is essentially the same as that using dry quenching, especially for a 3000m³ blast furnace. 3 The TRT power generation of the blast furnace is stable at around 45 kWh / t. When operating a 3000 m³ blast furnace using this method, after deducting the moisture content from the water quenching process, the blast furnace fuel consumption remains relatively stable at 512 kg / t. Therefore, this invention achieves the optimal mode for switching between dry and water quenching.

[0029] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for switching between dry quenching and water quenching in a blast furnace, characterized in that, The steps are as follows: S1. Calculate the weight of each batch of water-quenched coke: Calculate the weight Mn of water-quenched coke based on the moisture change value between dry-quenched and water-quenched coke, the batch weight of ore, and the batch weight of dry-quenched coke. S2. Verify the batch weight of ore and the batch weight of water-quenched coke: Based on the temperature loss coefficient α of the furnace top gas during each batch of water-quenched coke, the weight of each batch of water-quenched coke needs to be reduced by Mn*α, so the weight of each batch of water-quenched coke is Mn-Mn*α. According to the coke load R, the corresponding batch weight of ore is (Mn-Mn*α)*R. S3. Adjust the feeding angle and number of feeding rings for ore, coke, and water-quenched coke: As the batch weight of ore and water-quenched coke decreases, adjust the feeding angle at the furnace top and the number of feeding rings corresponding to each angle. Under the original number of feeding rings, calculate the weight of ore added in each ring. After the batch weight of ore decreases, ensure that the weight of ore added in each ring remains unchanged as a benchmark, calculate the number of feeding rings for ore after the batch weight of ore decreases, and adjust the number of feeding rings for coke and water-quenched coke accordingly. The method for adjusting the number of feeding rings for coke is the same as the method for adjusting the number of feeding rings for ore. S4. After using water-quenched coke for a period of time, if the temperature of the furnace top gas drops significantly, repeat steps S1-S3 to reduce the batch weight of ore and water-quenched coke and maintain a stable furnace top gas temperature.

2. The method for switching between dry quenching and water quenching in a blast furnace as described in claim 1, characterized in that, In step S1, the specific calculation method is as follows: The change in moisture content between dry quenching and water quenching is calculated as ΔY = Yn - Y, where Yn is the moisture content of each batch of water-quenched coke entering the furnace, which is obtained through real-time online monitoring, and Y is the moisture content of dry quenching coke used in the blast furnace. Calculate the coke batch weight M2 when using dry quenching coke: M2 = M1 / R, where M1 is the ore batch weight and R is the coke load. When dry quenching coke is used, the volume occupied inside the blast furnace by the dry quenching coke batch weight M2 corresponding to the ore batch weight M1 is: V1=M2 / β1=(M1 / R) / β1, where β1 is the measured bulk density of dry quenching coke. The volume of water-quenched coke is calculated as V2 = (M2 + M2 * ΔY) / β2, where β2 is the measured bulk density of water-quenched coke; the change in coke volume during the transition from water-quenched to dry-quenched coke is obtained as ΔV = V2 - V1. Finally, the weight of each batch of water-quenched coke was calculated as Mn = (M2 + M2 * ΔY) + ΔV * β2.

3. The method for switching between dry quenching and water quenching in a blast furnace as described in claim 1, characterized in that, In step S2, the specific verification method is as follows: Calculate the furnace top gas temperature loss coefficient α = (T2-T1) / T during the period of water quenching of coke for each batch, where T is the average furnace top gas temperature during the period of dry quenching of coke, T1 is the change in furnace top gas temperature as the dry quenching coke material level drops by 1 meter during the smelting process, and T2 is the change in furnace top gas temperature as the water quenching coke material level drops by 1 meter during the smelting process.

4. The method for switching between dry quenching and water quenching in a blast furnace as described in claim 1, characterized in that, In step S3, the ore angle is kept constant, and the water-quenched coke cloth angle is reduced based on the original cloth angle. The adjustment is made by reducing the maximum angle by 0.1°-0.5° and increasing the minimum angle by 0.1°-0.5°.

5. The method for switching between dry quenching and water quenching in a blast furnace as described in claim 4, characterized in that, In step S3, the angle of the water-quenched coke fabric is adjusted according to the moisture change value ΔY between dry quenching and water quenching: When ΔY < 5%, the adjustment amount is 0.1°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.1°, and the minimum fabric angle of water-quenched coke is increased by 0.1°; When 5%≤ΔY<10%, the adjustment amount is 0.2°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.2°, and the minimum fabric angle of water-quenched coke is increased by 0.2°; When 10%≤ΔY<15%, the adjustment amount is 0.3°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.3°, and the minimum fabric angle of water-quenched coke is increased by 0.3°; When 15%≤ΔY≤20%, the adjustment amount is 0.4°, that is, the maximum fabric angle of water-quenched coke is reduced by 0.4°, and the minimum fabric angle of water-quenched coke is increased by 0.4°; When ΔY > 20%, the adjustment amount is 0.5°, which means that the maximum fabric angle of water-quenched coke is reduced by 0.5° and the minimum fabric angle of water-quenched coke is increased by 0.5°.