A method suitable for hot blast stove peak-shaving during blast furnace maintenance period

Abstract

This invention discloses a method for staggered gas usage of hot blast stoves during blast furnace maintenance. During blast furnace maintenance, three hot blast stoves are used simultaneously for firing during off-peak electricity periods. Towards the end of firing, the combustion chamber temperature of the hot blast stoves is maintained at no less than 950℃, while the flue gas temperature is controlled to be no greater than 350℃. When the expansion coefficient of the checker bricks is ≤1.25%, the furnace heat loss is calculated, and the furnace temperature during peak electricity periods is predicted based on this heat loss. If the furnace temperature during peak electricity periods is >950℃, the hot blast stoves are stopped firing and kept warm during peak electricity periods. If the furnace temperature during peak electricity periods is ≤950℃, the stoves are supplemented for firing during off-peak electricity periods until the furnace temperature during peak electricity periods exceeds 950℃, at which point supplementary firing during off-peak electricity periods is stopped. This invention reduces heat loss and gas waste caused by hot blast stove insulation during blast furnace maintenance.

Description

Technical Field

[0001] This invention belongs to the technical field of blast furnace hot blast stove equipment, specifically relating to a method for staggered gas consumption of hot blast stoves during blast furnace maintenance. Background Technology

[0002] The hot blast stove is one of the thermal furnace devices used in the blast furnace ironmaking process. It uses blast furnace gas as its energy medium (consuming approximately 35%), stably providing blast to the blast furnace at temperatures above 1200℃. The heat supplied accounts for about 25% of the energy consumption in ironmaking, directly affecting the yield and quality of pig iron. During periods of shutdown, when the temperature drops below 800℃, the silica brick lattice undergoes a transformation, resulting in significant volume changes and causing some damage to the hot blast stove. To ensure the safety of the hot blast stove, a furnace-keeping operation is required during short-term shutdowns and major repairs of the blast furnace. To maintain a furnace temperature above 900℃, the furnace needs to be fired every 4 hours for 2 hours each time, consuming a large amount of gas resources.

[0003] Currently, due to the imbalance between daytime and nighttime demand for electricity from the power grid, industrial electricity supply has largely adopted a peak-shaving, flat-shaving, and valley-shaving differential pricing model. Local governments adjust the price difference based on local power structure and load. Generally, daytime electricity consumption is concentrated, resulting in high demand for grid power, which is the peak electricity period, and prices are appropriately increased. Conversely, nighttime demand is low, which is the valley-shaving period, and prices are appropriately decreased. In the steel industry, surplus coal gas resources are primarily used for power generation. Therefore, under the time-of-use pricing system, steel companies' coal gas resources have different values ​​at different times. During existing blast furnace maintenance periods, statistics show that the proportion of gas consumption during peak, flat, and valley-shaving electricity periods is equal, indicating that the proportion of gas consumption during peak-shaving electricity periods is not effectively controlled, leaving significant room for profit generation through off-peak gas usage. Summary of the Invention

[0004] In view of this, the present invention provides a method for staggered gas consumption of hot blast stoves during blast furnace maintenance, which introduces the concept of peak and valley gas management and reduces heat loss and gas waste caused by hot blast stove insulation during blast furnace maintenance.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for staggered gas consumption of hot blast stoves during blast furnace maintenance:

[0007] During blast furnace maintenance, three hot blast stoves were used simultaneously for furnace operation during off-peak electricity pricing periods.

[0008] During the final stage of furnace firing, maintain the combustion chamber temperature of the hot blast stove at no less than 950℃, while controlling the flue gas temperature to be no more than 350℃.

[0009] When the expansion coefficient of the checker bricks is ≤1.25%, the heat loss of the furnace body is calculated, and the furnace temperature during the peak electricity price period is predicted based on the heat loss of the furnace body. If the furnace temperature during the peak electricity price period is >950℃, the hot blast stove stops firing during the peak electricity price period and is kept warm. If the furnace temperature during the peak electricity price period is ≤950℃, the furnace is supplemented with firing during the parity electricity price period until the furnace temperature during the peak electricity price period is >950℃, at which point the supplementation of firing during the parity electricity price period is stopped.

[0010] In a further technical solution, the combustion chamber temperature and flue temperature are both monitored using infrared thermometry.

[0011] A further technical solution involves increasing the amount of gas used and extending the firing time during off-peak electricity hours if the combustion chamber temperature is less than 950°C.

[0012] A further technical solution involves supplying air to cool the flue if the flue temperature exceeds 350°C.

[0013] A further advanced technical solution involves using a combustion-supporting fan to deliver air and cool the flue through combustion-supporting air ducts and cold air ducts.

[0014] A further technical solution is to reduce the furnace intensity if the expansion coefficient of the checker bricks is greater than 1.25%.

[0015] A further technical solution is that the expansion coefficient of the grid brick includes a transverse expansion coefficient and a longitudinal expansion coefficient.

[0016] Further technical solutions involve calculating furnace heat loss according to GB / T32287-2015.

[0017] The beneficial effects of this invention are as follows: During blast furnace maintenance, the hot blast stove system is changed from two-burner-one-feeder to three hot blast stoves. All three hot blast stoves operate simultaneously during off-peak electricity periods. By maintaining the combustion chamber temperature of the hot blast stoves at no less than 950℃ and the flue gas temperature at no more than 350℃, and by reducing the firing intensity, the expansion coefficient of the checker bricks is kept ≤1.25%. Finally, based on the furnace heat loss, the furnace temperature during peak electricity periods is predicted. If the furnace temperature during peak electricity periods is >950℃, the hot blast stoves stop firing and are simultaneously kept warm during peak electricity periods. If the furnace temperature during peak electricity periods is ≤950℃, the stoves are fired during off-peak electricity periods until the furnace temperature during peak electricity periods exceeds 950℃. This invention reduces heat loss and gas waste caused by hot blast stove insulation during blast furnace maintenance and achieves efficient utilization of gas during peak electricity periods. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for staggered gas consumption of hot blast stoves during blast furnace maintenance, as described in this invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0020] like Figure 1 As shown, the present invention provides a method for staggered gas consumption of hot blast stoves during blast furnace maintenance, specifically including the following:

[0021] During blast furnace maintenance, the firing mode is changed. In the existing technology, a blast furnace is equipped with three hot blast stoves. Under normal production conditions, one hot blast stove supplies hot air, and the other two hot blast stoves are used for firing and heating. Considering that no hot air needs to be supplied during maintenance, but the hot blast stoves still need to maintain the furnace temperature >900℃, in this implementation, during blast furnace maintenance, all three hot blast stoves are set up for firing and heating, and all three hot blast stoves are fired simultaneously during off-peak electricity hours.

[0022] At the end of the furnace firing process, infrared thermography is used to monitor the combustion chamber temperature of the hot blast stove and transmit it to the control terminal. If the combustion chamber temperature is <950℃, during off-peak electricity hours, the amount of gas used is increased and the furnace firing time is extended to always keep the combustion chamber temperature of the hot blast stove not lower than 950℃, so as to prevent the gas from failing to burn after being introduced, which could lead to safety hazards in the hot blast stove.

[0023] When the combustion chamber temperature is ≥950℃, infrared thermography is used to monitor the flue temperature and transmit it to the control terminal. If the flue temperature is >350℃, the combustion air duct and the cold air duct are opened. The combustion air blower supplies air to the flue through the combustion air duct and the cold air duct to cool it down. The flue temperature should not exceed 350℃ to avoid heat accumulation at the bottom of the furnace during the heat preservation period. Excessive flue temperature will affect the safety of the grate.

[0024] When the flue temperature is ≤350℃, the expansion coefficient of the checker bricks is calculated. If the expansion coefficient of the checker bricks is >1.25%, the furnace intensity is reduced, and the combustion chamber temperature and flue temperature are monitored again, and the expansion coefficient of the checker bricks is calculated again until the expansion coefficient of the checker bricks is ≤1.25% to avoid excessive temperature changes affecting the life of the silica bricks. The expansion coefficient of the checker bricks includes the transverse expansion coefficient and the longitudinal expansion coefficient, and the process of calculating the expansion coefficient of the checker bricks is existing technology.

[0025] When the expansion coefficient of the checker bricks is ≤1.25%, the furnace heat loss is calculated according to GB / T32287-2015. Based on the furnace heat loss, the furnace temperature during peak electricity price periods is predicted (the specific prediction method is the existing technology). If the furnace temperature during peak electricity price periods is >950℃, the hot blast stove stops firing during peak electricity price periods and is simultaneously kept warm. If the furnace temperature during peak electricity price periods is ≤950℃, the furnace is supplemented with firing during normal electricity price periods. The combustion chamber temperature, flue temperature, and expansion coefficient of the checker bricks are monitored to ensure that the combustion chamber temperature is ≥950℃, the flue temperature is ≤350℃, and the expansion coefficient of the checker bricks is ≤1.25%. Then, the furnace heat loss is calculated, and the furnace temperature during peak electricity price periods is predicted based on the furnace heat loss until the furnace temperature during peak electricity price periods is >950℃, at which point supplementary firing during normal electricity price periods is stopped.

[0026] Specific Implementation Example: From July 18th to August 15th, 2022, a steel plant's 1080m³... 3 During the blast furnace overhaul, sufficient off-peak gas was used for hot blast stove insulation (i.e., all three hot blast stoves were kept running continuously during off-peak electricity periods) to ensure that the combustion chamber temperature was >1050℃ at 8:00 AM (the start time of peak electricity). During peak electricity periods and peak-price electricity periods, furnace operation was prohibited unless there were special circumstances. During the parity electricity periods, furnace operation was carried out 1-2 times as needed. According to statistics, gas consumption during peak electricity periods decreased by about 52% compared to conventional operations, reducing energy costs by about 100,000 yuan.

[0027] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for staggered gas consumption of hot blast stoves during blast furnace maintenance, characterized in that: During blast furnace maintenance, three hot blast stoves were used simultaneously for furnace operation during off-peak electricity pricing periods. During the final stage of furnace firing, maintain the combustion chamber temperature of the hot blast stove at no less than 950℃, while controlling the flue gas temperature to be no more than 350℃. When the expansion coefficient of the checker bricks is ≤1.25%, the heat loss of the furnace body is calculated, and the furnace temperature during the peak electricity price period is predicted based on the heat loss of the furnace body. If the furnace temperature during the peak electricity price period is >950℃, the hot blast stove stops firing during the peak electricity price period and is kept warm. If the furnace temperature during the peak electricity price period is ≤950℃, the furnace is supplemented with firing during the parity electricity price period until the furnace temperature during the peak electricity price period is >950℃, at which point the supplementation of firing during the parity electricity price period is stopped.

2. The method for hot blast stove peak-shaving gas utilization during the blast furnace maintenance period according to claim 1, characterized in that, The combustion chamber temperature and flue temperature are both monitored using infrared thermometry.

3. The method for hot blast stove peak-shaving gas utilization during BF maintenance period according to claim 2, characterized in that, If the combustion chamber temperature is less than 950℃, increase the amount of gas used and extend the firing time during off-peak electricity hours.

4. The method for hot blast stove peak-shaving gas utilization during BF maintenance period according to claim 2, characterized in that, If the flue temperature is greater than 350℃, then the flue should be cooled by supplying air.

5. The method for hot blast stove peak-shaving gas utilization during the maintenance of blast furnace according to claim 4, characterized in that, The combustion air blower supplies air to the flue and cools it through the combustion air duct and the cold air duct.

6. The method for hot blast stove peak-shaving gas utilization during BF maintenance period as claimed in claim 1, wherein, If the expansion coefficient of the checker bricks is greater than 1.25%, the firing intensity of the furnace will be reduced.

7. The method for staggered gas consumption of hot blast stoves during blast furnace maintenance, as described in claim 6, is characterized in that... The expansion coefficient of the checker bricks includes the transverse expansion coefficient and the longitudinal expansion coefficient.

8. The method for staggered gas consumption of hot blast stoves during blast furnace maintenance according to claim 1, characterized in that, Calculate the furnace body heat loss according to GB / T32287-2015.

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