Method for controlling zero emission of coal gas by single blast furnace

Abstract

The present application belongs to the technical field of blast furnace gas processing, and relates to a method for controlling zero emission of gas of a single blast furnace, comprising the following steps: step 1, comprehensively adjusting according to the original gas balance to maintain the balance between gas supply and demand; step 2, realizing dynamic storage of the gas holder and stable pressure of the pipe network by means of interval regulation of the gas holder; step 3, effectively controlling the switch valve group at the end to ensure safe and controllable end emission; and step 4, emergency disposal under abnormal production conditions, formulating special measures for blast furnace wind reduction, abnormal gas flow and abnormal gas temperature, giving priority to system safety and dynamically maintaining the zero emission target. The present application realizes efficient utilization and zero emission of blast furnace gas through multi-link collaborative regulation, reduces environmental pollution and improves production economy.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace gas treatment technology, and relates to a method for zero venting of gas, particularly a method for controlling zero venting of gas in a single blast furnace. Background Technology

[0002] In a single blast furnace production system in the metallurgical industry, the generation and transportation path of blast furnace gas is as follows: The blast furnace is connected to a gravity dust collector through a blast furnace downcomer. The outlet of the gravity dust collector is connected to a valve group via a raw gas pipeline. The valve group is connected to a bag filter and a clean gas pipeline respectively. The clean gas pipeline is further branched through a check valve. One branch is connected to a gas holder for gas storage, and the other branch is connected to a gas vent chimney for emergency discharge. The gas vent chimney is equipped with an automatic ignition device. The bag filter is connected to the gas pipeline network to supply gas to downstream users (such as hot blast stoves, gas boilers, etc.).

[0003] Blast furnace gas, as a byproduct of blast furnace production, has specific properties (see Table 1 for specific parameters). Its lower heating value is 3140 kJ / m³, and it contains combustible components such as 20% carbon monoxide (CO) and 1.7% methane (CH4), as well as 22% carbon dioxide (CO2).

[0004] Table 1 Characteristic Parameters of Blast Furnace Gas

[0005] However, existing single blast furnace gas treatment technologies have significant drawbacks: 1. Low utilization rate: Taking the 1000m³ blast furnace of Tianjin Steel Pipe Ironmaking Plant as an example, in order to ensure system safety, the gas release at the end of the gas release tower was not controlled, and the gas release rate was as high as 6%-8%. A large amount of combustible components were not effectively utilized, resulting in energy waste.

[0006] 2. Serious environmental pollution: The greenhouse effect of methane in the released coal gas is 25 times that of carbon dioxide, and the acidic components in the coal gas may form acid rain. Long-term emissions will exacerbate the greenhouse effect and destroy the ecological balance.

[0007] 3. High cost pressure: As cost competition intensifies in the ironmaking industry, underutilized coal gas resources indirectly increase the cost of pig iron production and reduce the economic benefits of enterprises.

[0008] 4. Safety and balance challenges: In single blast furnace production, gas production and user consumption are prone to fluctuations, making it difficult to achieve absolute balance. Traditional control methods rely on large-scale venting to ensure safety when system pressure is too high or when the furnace is shut down, which cannot take into account both environmental protection and safety goals.

[0009] Therefore, there is an urgent need for a control method that can achieve zero flammation of gas from a single blast furnace, improve utilization, reduce pollution, and ensure system safety. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for controlling zero venting of gas in a single blast furnace.

[0011] The technical problem solved by this invention is achieved through the following technical solution: A method for controlling zero venting of gas in a single blast furnace, characterized by comprising the following steps: Step 1: Make comprehensive adjustments based on the original gas balance, with the hot blast stove replacement as the core node, in three stages: pre-adjustment before replacement, dynamic adjustment during replacement, and post-replacement balance restoration. Coordinate and regulate the gas consumption of gas boilers and sintering ignition to maintain the gas supply and demand balance. Step 2: With the help of the gas holder's interval control, using the gas holder height of 20-23 meters and the lifting speed ≤0.60m / min as the control threshold, the automatic pressure regulation of the DN1200 regulating valve is combined with the interlocking control of the DN600 and DN800 valve groups to achieve dynamic storage of gas in the gas holder and stable pipeline pressure. Step 3: Effective control of the terminal venting valve group. Through the interlocking logic of the DN1200 regulating valve opening with the ignition device and nitrogen purge valve, combined with weekly valve calibration, the terminal venting is ensured to be safe and controllable. Step 4: Emergency response under abnormal production conditions. Develop specific measures for blast furnace blast reduction, abnormal gas flow, and abnormal gas temperature, prioritizing system safety and dynamically maintaining the zero venting target.

[0012] Furthermore, the method of comprehensively adjusting the original gas balance, taking the hot blast stove replacement as the core node, and dividing it into three stages—pre-adjustment before replacement, dynamic adjustment during replacement, and post-replacement balance restoration—to coordinate and regulate the gas consumption of the gas boiler and sintering ignition, and maintain the gas supply and demand balance, is as follows: Step 1.1, Pre-adjustment before furnace change: The hot blast stove adopts a "2-burn 1-send" mode, with the gas consumption of the two stoves maintained at 68,000-80,000 cubic meters. Ten minutes before the stove change, the hot blast operator notifies the gas purification main control to start the "dual-burn to single-burn" transition. The main control unit for gas purification confirms the height of the gas holder: if the holder height is at the lower limit, the current user consumption remains unchanged; if the holder height is at the middle or upper limit, the gas boiler is notified to gradually increase the gas consumption until the gas holder height drops to the lower limit, thus reserving buffer space for gas consumption fluctuations during the boiler replacement phase.

[0013] Step 1.2, Dynamic adjustment during furnace changeover: After the main control unit of the gas purification system confirms that the gas holder is in compliance with the standard, it notifies the hot blast stove to start the furnace replacement, and the furnace replacement time is controlled within 10 minutes. The hot air operator reduces the gas consumption of the furnace to be shut down to zero in three evenly divided steps within 10 minutes, while simultaneously increasing the gas consumption of another hot air furnace to the maximum limit. The main control unit for gas purification monitors the height of the gas holder in real time and simultaneously notifies the gas boiler and sintering ignition to increase the gas consumption to the maximum design value, maintaining the height of the gas holder within the normal range and avoiding abnormal fluctuations in the holder height.

[0014] Step 1.3, Restore balance after furnace replacement: When the hot blast stove is started, the hot blast operator notifies the gas purification main control and adjusts the gas consumption of both hot blast stoves to 35,000 cubic meters in three equal steps. The gas purification main control notifies the gas boiler and sintering ignition to resume normal usage and return to the initial gas balance state.

[0015] Furthermore, in step 2, when the pipeline pressure is greater than 12 kPa, the gas holder height is greater than 24 meters, or the gas holder lifting speed is greater than 0.65 m / min, the DN1200 regulating valve automatically adjusts the pressure and simultaneously interlocks to open the DN600 and DN800 electric gate valves. After the parameters are restored, the valves are manually closed.

[0016] Furthermore, in step 3, when the opening of the DN1200 regulating valve is greater than 3% and lasts for 5 minutes, the ignition device is interlocked and activated; when the opening is less than 2%, the nitrogen purge valve is interlocked and automatically closes after the fire is extinguished; when checking the valves weekly, the corresponding associated valves must be closed first, and the initial state must be restored after the check.

[0017] Furthermore, if the gas flow is abnormal in step 4, the gas boiler must be notified immediately to ignite the natural gas for fire protection, cancel the zero-venting interlock, and manually adjust the DN1200 regulating valve; when the gas temperature is >250℃, open the venting pipeline valve group, close the dust collector main pipe valve group, and start the ignition venting.

[0018] The advantages and beneficial effects of this invention are as follows: This method for controlling zero gas release in a single blast furnace breaks through the limitations of traditional single-user regulation or single-valve control. It combines the phased fluctuations in hot blast stove usage during furnace replacement, the dynamic storage of gas holders, the precise control of terminal valve groups, and emergency response to form a closed-loop control throughout the entire process, solving the core problem of unbalancing gas supply and demand in a single blast furnace.

[0019] This invention achieves the goal of zero emissions of coal gas, completely eliminating the direct emission of gases such as methane (which has a greenhouse effect 25 times that of CO2) and carbon monoxide, and can reduce CO2 equivalent emissions by more than 10,000 tons per year, effectively mitigating the greenhouse effect and acid rain risks. This invention avoids air pollution caused by the emission of unburned coal gas and complies with the environmental emission standards of the metallurgical industry.

[0020] This invention improves the utilization rate of coal gas by 6%-8%. Taking a 1000m³ blast furnace as an example, it can utilize about 1.8 million cubic meters of coal gas per year. Based on the lower heating value, this is equivalent to saving about 1.2 million cubic meters of natural gas and reducing energy costs by more than 800,000 yuan. Reducing heat loss from gas venting indirectly lowers the energy consumption of gas-fired boilers and hot blast stoves, helping to reduce pig iron manufacturing costs by 3-5 yuan / ton and enhancing the company's market competitiveness.

[0021] Through a four-level safety control system of "early warning-adjustment-interlock-emergency", the pressure fluctuation of the pipeline network is controlled within a safe range (8.8-12 kPa), avoiding the risk of explosion caused by excessive pressure; In response to emergencies such as abnormal gas temperature or gas flow, specific measures have been developed to ensure the safe operation of critical equipment such as purification equipment and fans, and to reduce equipment damage rates and the risk of production interruption. Detailed Implementation

[0022] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0023] This invention achieves zero gas venting from a single blast furnace through a four-stage coordinated control system: "gas balance adjustment - gas holder interval regulation - terminal vent valve group control - emergency response". The specific steps are as follows: Step 1: Comprehensive adjustment of gas balance based on user needs With the control of gas consumption by major users such as hot blast stoves, gas-fired boilers, and sintering ignition as the core, a dynamic balance between gas supply and demand is achieved through phased coordinated adjustments: Before hot blast stove replacement (pre-adjustment stage): The hot blast stove adopts a "2-burn 1-send" mode, with the gas consumption of the two stoves maintained at 68,000-80,000 cubic meters (average 70,000 cubic meters, 35,000 cubic meters for a single stove); 10 minutes before the stove change, the hot blast operator notifies the gas purification main control to start the "dual-burn to single-burn" transition. The main control unit for gas purification confirms the height of the gas holder: if the holder height is at the lower limit (≤20 meters), the current user consumption remains unchanged; if the holder height is at the middle or upper limit (>20 meters), the gas boiler is notified to gradually increase the gas consumption until the gas holder height drops to the lower limit, thus reserving buffer space for gas consumption fluctuations during the boiler replacement phase.

[0024] Hot blast stove replacement in progress (dynamic adjustment phase): After the main control unit of the gas purification system confirms that the gas holder is in compliance with the standard, it notifies the hot blast stove to start the furnace replacement, and the furnace replacement time is controlled within 10 minutes. The hot air operator shall reduce the gas consumption of the furnace to be shut down to zero in three evenly divided steps within 10 minutes, while simultaneously increasing the gas consumption of the other hot air furnace to the upper limit (to meet the safety requirements of arch temperature ≤1320℃ and exhaust gas temperature ≤420℃). The main control unit for gas purification monitors the height of the gas holder in real time and simultaneously notifies the gas boiler and sintering ignition to increase the gas consumption to the maximum design value, maintaining the height of the gas holder within the normal range (20-23 meters) and avoiding abnormal fluctuations in the holder height.

[0025] After hot blast stove replacement (restoration phase): When the hot blast stove is started, the hot blast operator notifies the gas purification main control and adjusts the gas consumption of both hot blast stoves to 35,000 cubic meters in three equal steps. The gas purification main control notifies the gas boiler and sintering ignition to resume normal usage and return to the initial gas balance state.

[0026] Step 2, using the gas holder's interval control Using the height of the gas holder (20-23 meters) and the lifting speed as core parameters, precise control of gas storage and pipeline pressure is achieved through automatic valve adjustment. Normal valve initial settings: In the clean gas venting system, the DN600 and DN800 electric gate valves and regulating valves are all manually closed; the DN1200 electric butterfly valve is manually normally open; the DN1200 regulating valve opening is set to 2% (considered as closed) and put into automatic regulation; the pipeline pressure in the program is set to 9.6 kPa.

[0027] Alarm and adjustment for abnormal cabinet height and lifting speed: When the height of the gas holder is greater than 23 meters or the lifting speed is greater than or equal to 0.60 m / min, the operation screen will flash and an alarm will be triggered, and the main control room will be activated with an audible and visual alarm. The DN1200 regulating valve will automatically switch to the 8.8 kPa pressure control mode to reduce the amount of gas entering the gas holder. When the height of the gas holder is less than 20 meters, the DN1200 regulating valve automatically returns to the 9.6 kPa pressure control mode, increasing the amount of gas entering the gas holder; If the automatic adjustment cannot stabilize the cabinet height or pressure, the interlock can be deactivated and the valve opening can be manually adjusted.

[0028] High-pressure / high-cube emergency control: When the pipeline pressure is greater than 12 kPa, the gas holder height is greater than 24 meters, or the gas holder lifting speed is greater than 0.65 m / min, the DN1200 regulating valve continues to automatically regulate the pipeline pressure, and at the same time, it interlocks to open the DN600 and DN800 electric gate valves and automatically adjusts their opening degree; after the parameters return to normal, the gas purification operator manually closes the DN600 and DN800 electric gate valves.

[0029] Step 3, effective control of the end-of-line venting valve assembly. By interlocking the valve action logic with ignition and purging, the safety and controllability of end-point venting are achieved: Ignition Interlock: When the opening of the DN1200 regulating valve is greater than 3% and lasts for 5 minutes, the automatic ignition device for clean gas venting is interlocked and activated to prevent unburned gas from being directly discharged. Purge Interlock: When the opening of the DN1200 regulating valve is <2%, the nitrogen purging valve for clean coal gas release is interlocked and opened. After confirming that the flame is extinguished, the nitrogen purging valve is automatically closed to prevent residual coal gas leakage. Valve periodic calibration: The power operation area conducts weekly calibration of all vent valve assemblies. Before operating DN600 and DN800 electric gate valves, the corresponding regulating valve must first be manually closed to 0% opening. Before operating the DN1200 regulating valve, its electric butterfly valve must be closed first; After verification, promptly restore all valves to their initial working state to ensure normal valve function.

[0030] Step 4, Emergency Response to Abnormal Production Conditions Specific emergency measures have been developed to address unforeseen circumstances such as blast furnace blast reduction, abnormal gas flow, and abnormal gas temperature, ensuring the dynamic maintenance of system safety and the zero-emission target. Emergency blast furnace blast reduction: If a significant reduction in blast is required during normal blast furnace production, the furnace foreman must immediately notify the gas control room. The gas control room will then adjust the gas consumption of each user. If the balance cannot be maintained, the zero-venting operation control should be promptly discontinued to prioritize system pressure stability.

[0031] Emergency response to abnormal gas flow: When the gas flow in the blast furnace is abnormal, the furnace foreman notifies the main control of the gas purification system. The gas purification system immediately notifies the gas boiler to ignite natural gas to maintain the flame (to prevent the boiler from shutting down and causing the blower to stop). At the same time, the "zero venting" interlock is canceled, and the DN1200 regulating valve is manually opened to a reasonable opening. The abnormal gas flow is temporarily handled through the venting tower. After the gas flow returns to normal, the zero venting control is restarted.

[0032] Emergency response to abnormal gas temperature: When the temperature of raw coal gas is <100℃, the coal gas purification control room sends a signal to the blast furnace control room to start ignition and release the low-temperature coal gas (to avoid the low-temperature coal gas affecting the efficiency of the purification equipment). When the temperature of raw coal gas exceeds 200℃, the coal gas purification control room sends a signal, and the blast furnace starts the top spray water cooling to control the coal gas temperature within the range that the purification system can handle (≤200℃). When the temperature of the raw coal gas exceeds 250℃, immediately open the venting pipeline valve group and close the dust collector main pipeline valve group to guide the coal gas into the venting chimney for ignition and venting, in order to prevent the high-temperature coal gas from damaging the purification equipment.

[0033] Taking the 1000m³ single blast furnace at Tianjin Steel Pipe Ironmaking Plant as an example, the method of this invention is used for zero gas emission control. The specific implementation conditions and effects are as follows: Implementation conditions Equipment configuration: The blast furnace is equipped with 3 rotary top-fired hot blast stoves (using 37-hole Φ28mm high-efficiency checker bricks), 1 gas holder (effective height 20-24 meters), 1 gas boiler (used to drive the steam turbine to generate blast furnace cold air), sintering ignition device, and the clean gas venting system is equipped with DN600, DN800, and DN1200 three-stage valve groups and automatic ignition and nitrogen purging devices.

[0034] Initial parameters: blast furnace gas lower heating value 3140kJ / m³, hot blast stove "2-burn 1-send" mode dual-furnace gas consumption 70,000 cubic meters, gas boiler maximum gas consumption 52,000 cubic meters, sintering ignition maximum gas consumption 18,000 cubic meters.

[0035] Implementation process and results During normal production: through the coordinated adjustment of hot blast stove replacement in step 1 and the control of gas holder intervals in step 2, the height of the gas holder is stabilized at 20-23 meters, the opening of the DN1200 regulating valve is maintained at 2% (closed state), and the DN600 and DN800 valve groups are fully closed, achieving zero gas release and increasing the gas utilization rate from 92%-94% to 100%.

[0036] Abnormal test phase: Simulating blast furnace blast reduction (30% reduction), after the furnace foreman notifies the gas control system, the gas control system increases the sintering ignition gas consumption from 12,000 cubic meters to 18,000 cubic meters and the gas boiler consumption from 40,000 cubic meters to 52,000 cubic meters. The gas balance is restored within 3 minutes, and no venting is initiated. When simulating abnormal gas flow, the gas boiler promptly ignites natural gas to maintain the flame, and the DN1200 regulating valve opening is manually adjusted to 5% (for 3 minutes). The ignition device starts automatically, and the zero venting state is restored within 10 minutes after the abnormality is resolved.

[0037] Long-term operational results: After implementing this invention, continuous monitoring for 6 months showed: The coal gas emission rate is stable at 0, with no emissions of methane, carbon monoxide, or other gases, reducing CO2 emissions by approximately 12,000 tons per year. The utilization rate of coal gas resources will be increased by 6%-8%, saving about 800,000 yuan in natural gas substitution costs annually, and reducing the cost of pig iron manufacturing by 3.2 yuan / ton; The pressure fluctuation range of the blast furnace gas system was controlled within 8.8-12 kPa, and no safety accidents caused by abnormal pressure occurred.

[0038] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for controlling zero venting of gas in a single blast furnace, characterized in that: Includes the following steps: Step 1: Make comprehensive adjustments based on the original gas balance, with the hot blast stove replacement as the core node, in three stages: pre-adjustment before replacement, dynamic adjustment during replacement, and post-replacement balance restoration. Coordinate and regulate the gas consumption of gas boilers and sintering ignition to maintain the gas supply and demand balance. Step 1.1, Pre-adjustment before furnace change: The hot blast stove adopts a "2-burn 1-send" mode, with the gas consumption of the two stoves maintained at 68,000-80,000 cubic meters. Ten minutes before the stove change, the hot blast operator notifies the gas purification main control to start the "dual-burn to single-burn" transition. The main control unit for gas purification confirms the height of the gas holder: if the holder height is at the lower limit, the current user consumption remains unchanged; if the holder height is at the middle or upper limit, the gas boiler is notified to gradually increase the gas consumption until the gas holder height drops to the lower limit, thus reserving buffer space for gas consumption fluctuations during the boiler replacement phase. Step 1.2, Dynamic adjustment during furnace changeover: After the main control unit of the gas purification system confirms that the gas holder is in compliance with the standard, it notifies the hot blast stove to start the furnace replacement, and the furnace replacement time is controlled within 10 minutes. The hot air operator reduces the gas consumption of the furnace to be shut down to zero in three evenly divided steps within 10 minutes, while simultaneously increasing the gas consumption of another hot air furnace to the maximum limit. The main control unit for gas purification monitors the height of the gas holder in real time and simultaneously notifies the gas boiler and sintering ignition to increase the gas consumption to the maximum design value, maintaining the height of the gas holder within the normal range and avoiding abnormal fluctuations in the holder height. Step 1.3, Restore balance after furnace replacement: When the hot blast stove is started, the hot blast operator notifies the gas purification main control and adjusts the gas consumption of both hot blast stoves to 35,000 cubic meters in three equal steps. The main control unit of the gas purification system notifies the gas boiler and sintering ignition to resume normal usage and return to the initial gas balance state. Step 2: With the help of the gas holder's interval control, using the gas holder height of 20-23 meters and the lifting speed ≤0.60m / min as the control threshold, the automatic pressure regulation of the DN1200 regulating valve is combined with the interlocking control of the DN600 and DN800 valve groups to achieve dynamic storage of gas in the gas holder and stable pipeline pressure. Normal valve initial settings: In the clean coal gas venting system, the DN600 and DN800 electric gate valves and regulating valves are all manually closed; the DN1200 electric butterfly valve is manually normally open; the DN1200 regulating valve opening is set to 2%, which is considered to be in the closed state and put into automatic regulation. The pipeline pressure in the program is set to 9.6 kPa. Alarm and adjustment for abnormal cabinet height and lifting speed: When the height of the gas holder is greater than 23 meters or the lifting speed is greater than or equal to 0.60 m / min, the operation screen will flash and an alarm will be triggered, and the main control room will be activated with an audible and visual alarm. The DN1200 regulating valve will automatically switch to the 8.8 kPa pressure control mode to reduce the amount of gas entering the gas holder. When the height of the gas holder is less than 20 meters, the DN1200 regulating valve automatically returns to the 9.6 kPa pressure control mode, increasing the amount of gas entering the gas holder; If the above automatic adjustment cannot stabilize the cabinet height or pressure, disconnect the interlock and switch to manual operation to adjust the valve opening. High-pressure / high-cube emergency control: When the pipeline pressure is greater than 12 kPa, the gas holder height is greater than 24 meters, or the gas holder lifting speed is greater than 0.65 m / min, the DN1200 regulating valve continues to automatically regulate the pipeline pressure, and at the same time, it interlocks to open the DN600 and DN800 electric gate valves and automatically adjusts their opening degree. After the parameters return to normal, the gas purification operator manually closes the DN600 and DN800 electric gate valves. Step 3: Effective control of the terminal venting valve group. Through the interlocking logic of the DN1200 regulating valve opening with the ignition device and nitrogen purge valve, combined with weekly valve calibration, the terminal venting is ensured to be safe and controllable. Step 4: Emergency response under abnormal production conditions. Develop specific measures for blast furnace blast reduction, abnormal gas flow, and abnormal gas temperature, prioritizing system safety and dynamically maintaining the zero venting target.

2. The method for controlling zero venting of gas in a single blast furnace according to claim 1, characterized in that: In step 2, when the pipeline pressure is greater than 12 kPa, the gas holder height is greater than 24 meters, or the gas holder lifting speed is greater than 0.65 m / min, the DN1200 regulating valve automatically adjusts the pressure and simultaneously interlocks to open the DN600 and DN800 electric gate valves. After the parameters are restored, the valves are manually closed.

3. The method for controlling zero venting of gas in a single blast furnace according to claim 1, characterized in that: In step 3, when the opening of the DN1200 regulating valve is >3% and lasts for 5 minutes, the ignition device interlock is activated; when the opening is <2%, the nitrogen purge valve interlock is opened and automatically closes after the fire is extinguished; when calibrating the valves weekly, the corresponding associated valves must be closed first, and the initial state must be restored after calibration.

4. The method for controlling zero venting of gas in a single blast furnace according to claim 1, characterized in that: In step 4, if the gas flow is abnormal, the gas boiler should be notified immediately to ignite the natural gas for flame protection, the zero-venting interlock should be canceled, and the DN1200 regulating valve should be manually adjusted. When the gas temperature is >250℃, the venting pipeline valve group should be opened, the dust collector main pipe valve group should be closed, and the ignition venting should be started.

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