Quick shutdown method for dry quenching system

Abstract

The invention discloses a quick shutdown method for a dry quenching system. The quick shutdown method comprises the following steps: gradually reducing the coke discharge amount and the air volume in a circulating air duct; a pre-storage section pressure regulating valve is used for maintaining the pressure in the pre-storage section to be 50-100 Pa; when the cooling speed is larger than a first theoretical threshold value, the measures of slowly reducing the circulating air volume, reducing the nitrogen filling amount and stopping coke discharging are taken; when the cooling speed is smaller than a second theoretical threshold value, the measures of slowly increasing the circulating air quantity, increasing the nitrogen filling quantity and discontinuously discharging coke are taken; chemicals are intermittently added into the boiler according to a water quality test result, and a main steam pressure relief regulating valve is completely opened; all desuperheating water regulating valves are manually closed; if the difference between the front steam temperature and the rear steam temperature of the desuperheater is larger than a third theoretical threshold value, front manual valves are all closed; and when continuous water supply of the boiler cannot be carried out, operation of the deaerator is stopped, the pressure and the temperature of the deaerator are gradually reduced until all the outlet valves of the deaerator are manually closed, and then the manual valve in front of the deaerator is closed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of dry quenching, and particularly relates to a dry quenching system rapid shutdown method. BACKGROUND

[0002] Dry quenching needs to perform shutdown and cooling operation to ensure production safety and stability and product quality when cleaning internal impurities, normal or abnormal maintenance, replacing refractory materials, temporarily stopping the furnace to implement changes, and coping with various abnormal conditions. Dry quenching shutdown is a key measure taken under various complex conditions to ensure safe operation of equipment, prolong service life, maintain product consistency, and carry out necessary maintenance and repair. The time control and operation method selection of the shutdown process are directly related to the equipment state of the dry quenching system and the efficiency of subsequent production recovery.

[0003] In actual operation, various factors such as environmental protection compliance requirements, operation safety risks, and technical feasibility need to be considered, and at the same time, rapid and smooth shutdown is pursued to effectively shorten the shutdown period and reduce economic losses caused by production interruption. In order to minimize the thermal shock on the coke oven lining, ensure the safety, order and efficient progress of the shutdown process, and thus control the damage to the dry quenching furnace body and key equipment to the lowest level, it is particularly important to develop a standardized and operable dry quenching system rapid shutdown method. The method should cover the preparation before shutdown, cooling rate control, system isolation measures, inert gas management, temperature monitoring and emergency plan, etc., to form a systematic and programmed operation guide to realize efficient, reliable and economic shutdown of the dry quenching device. SUMMARY

[0004] The present application provides a dry quenching system rapid shutdown method to solve the problems of long cooling period, complex operation and easy thermal shock on equipment in the existing dry quenching system shutdown method. The method realizes safe, rapid and orderly shutdown under special conditions by controlling the cooling speed in stages and optimizing the operation process of key components.

[0005] To achieve the above technical purposes, the present application provides a dry quenching system rapid shutdown method, which comprises: Gradually reducing the coke discharge amount of the coke discharge device and the air volume in the circulating air duct; Controlling the cooling speed by changing the circulating air volume, nitrogen charging amount and intermittent coke discharge; Maintaining the pressure in the pre-storage section at 50Pa to 100Pa by using a pre-storage section pressure regulating valve; When the cooling speed is greater than the first theoretical threshold, measures of slowly reducing the circulating air volume, reducing the nitrogen charging amount, and stopping coke discharge are taken; When the cooling rate is less than the second theoretical threshold, measures such as slowly increasing the circulating air volume, increasing the nitrogen charge, and intermittently discharging the coke are taken; According to the water quality test results, chemicals are intermittently added to the boiler. As the boiler inlet temperature decreases, the main steam temperature and pressure decrease, at which time the main steam pressure relief regulating valve is fully opened, and the main steam pressure relief regulating valve is used to control the drum pressure. To avoid the main steam temperature from decreasing too quickly, the desuperheating water regulating valve is manually closed; If the difference between the steam temperatures before and after the desuperheater is greater than the third theoretical threshold, manually close all the front manual valves. When continuous boiler feed water cannot be performed, stop the deaerator operation, gradually reduce the deaerator pressure and temperature, control the temperature drop within 10℃ per hour, until the deaerator outlet valve is manually closed, and then close the front manual valve.

[0006] Further: When the pre-storage section temperature of the dry quenching furnace decreases to below 450℃, manually open the furnace cover on site, and visually confirm whether the coke is completely extinguished. After confirmation, close the furnace cover.

[0007] Further: After confirming that the coke is completely extinguished, close the circulating air fan inlet nitrogen charging valve and the dry quenching furnace inlet nitrogen charging valve.

[0008] Further: When the pre-storage section temperature of the dry quenching furnace decreases to the range of 300℃ to 100℃, introduce air into the system for cooling, and confirm that the coke inside the system is completely extinguished before operation.

[0009] Further: Open all the normal relief valves at the top of the dry quenching furnace pre-storage section, manually move the charging device to open the furnace cover, and open the emergency relief valve at the boiler inlet.

[0010] Further: Open the manhole covers on both sides to safely confirm the gas composition, with the detection standard being CO content less than 24ppm, H2 content less than 10ppm, and O2 content higher than 18%.

[0011] Further: After the system pressure is lower than 0.2MPa, pay attention to the drainage at each point, maintain steam flow, and avoid internal water corrosion.

[0012] Further: When the pre-storage section temperature of the dry quenching furnace decreases to the range of 100℃ to 50℃, introduce a large amount of air for system cooling.

[0013] Further: Open all the secondary dust collector inspection ports and the upper explosion-proof valves, and at the same time of air sweeping in the gas circulation system, periodically sweep the dead corners of the boiler.

[0014] Further: stop circulating fan, desulfurization and dust removal fan, boiler feed water pump operation; open all manholes of the boiler, dry quenching furnace, discharge device, dust removal and the like; stop the environmental dust removal fan operation; stop the cooling water supply of each unit after 2 hours of all equipment stop running.

[0015] The advantages and positive effects of the present application are: The present application significantly shortens the shutdown time of the dry quenching system by controlling the cooling speed in stages and optimizing the operation process of key components, while reducing the damage to the refractory lining caused by excessive temperature difference. The method realizes balanced cooling of the whole system by precisely controlling the circulating air volume, nitrogen charging volume and coke discharge speed, ensuring the stability and safety of the system. In addition, through the fine operation of the boiler system and the dust removal system, the problems of equipment corrosion and abnormal gas composition are effectively avoided, improving the reliability and environmental protection of the shutdown process. DETAILED DESCRIPTION

[0016] The technical solutions of the embodiments of the present application will be described clearly and completely below. The described embodiments are only part of the examples of the present application, not all. Obviously, the shown embodiments of the present application demonstrate the technical solutions with characteristics. Based on the embodiments of the present application, any other embodiments obtained by the skilled in the art without creative labor are within the protection scope of the present application.

[0017] A dry quenching system rapid shutdown method mainly includes: When the dry quenching system needs to be shut down, first start the load reduction operation, which is realized by gradually reducing the coke discharge amount and the circulating air volume. Specifically, first reduce the coke discharge amount of the coke discharge device, and then gradually reduce the air volume in the circulating air duct to avoid system instability caused by large increase or decrease.

[0018] The temperature change rate must be strictly controlled during the load reduction process to ensure balanced cooling of the whole system. For example, in the initial stage of cooling (900℃ to 450℃), the cooling speed is controlled by changing the circulating air volume, nitrogen charging volume and intermittent coke discharge. At this time, the circulating fan inlet nitrogen charging valve and the dry quenching furnace inlet nitrogen charging valve are opened to charge nitrogen into the system to ensure that the oxygen concentration in the furnace is less than 6% to prevent explosion or fire accidents. At the same time, the pre-storage section pressure regulating valve is used to maintain the pressure in the pre-storage section in the range of 50Pa to 100Pa to ensure the stability of gas flow.

[0019] When the cooling rate is too fast, the following measures should be taken to regulate it: slowly reduce the air volume in the circulating air duct, reduce the nitrogen charge, and stop the coke discharge from the coke discharge device. Conversely, if the cooling rate is too slow, the following measures should be taken: slowly increase the air volume in the circulating air duct, increase the nitrogen charge, and perform intermittent coke discharge. This dynamic adjustment mechanism can flexibly respond to real-time temperature changes, ensuring a stable and controllable cooling process. In addition, the boiler system also needs to be adjusted synchronously during the cooling process. After the discharge device stops operating, appropriate chemicals can be intermittently added to the boiler according to the water quality test results to maintain water quality stability. As the temperature at the boiler inlet decreases, the main steam temperature and pressure also decrease. At this time, the main steam pressure regulating valve can be fully opened, and the main steam pressure relief regulating valve can be used to control the steam drum pressure. To avoid the main steam temperature decreasing too quickly, the desuperheating water regulating valve should be manually closed completely; if a large difference in steam temperature is found before and after the desuperheater, the manual valve before it should be manually closed completely. When continuous boiler feedwater cannot be provided, stop the deaerator operation, gradually reduce the deaerator pressure and temperature, controlling the temperature drop at 10°C per hour, until the deaerator outlet valve is manually closed completely, and then close the upstream manual valve.

[0020] During the coke removal process, the operator must strictly monitor the coke removal temperature to ensure that it is below 150℃.

[0021] After entering the later cooling stage (450℃ to 50℃), the cooling operation steps are further refined. When the temperature of the pre-storage section of the dry quenching furnace drops below 450℃, the furnace cover is manually opened on-site to visually confirm whether the coke is completely extinguished. After confirmation, the furnace cover is closed. This confirmation step is crucial because subsequent operations can only continue if the coke is completely extinguished; otherwise, it may lead to safety hazards. After confirming that the coke is completely extinguished, the nitrogen charging valve is closed, and the charging of nitrogen into the system is stopped. Subsequently, coke continues to be discharged according to the plan, and it is confirmed at the on-site conveyor belt that no red-hot coke is being discharged. This step is completed by observing the discharge of the coke discharge device to ensure that the coke has been sufficiently cooled.

[0022] When the temperature in the pre-storage section of the dry quenching furnace drops to between 300°C and 100°C, air is introduced into the system for cooling. Before this operation, it must be confirmed again that the coke inside the system is completely extinguished to avoid a combustion reaction after the air is introduced. Next, all the commonly used vent valves in the pre-storage section at the top of the dry quenching furnace are opened, the furnace cover is opened manually by moving the loading device, and the emergency vent valve at the boiler inlet is opened. Subsequently, the manhole covers on both sides are opened to conduct a safety check of the gas composition. This check includes checking whether the CO content is below 24 ppm, the H2 content is below 10 ppm, and the O2 content is above 18%. Only when the gas composition meets the safety standards can subsequent operations continue.

[0023] Regarding the boiler system, while continuing to reduce temperature and pressure, a series of refined operations are also required. When the water supply is low, water should be added to the boiler intermittently, and the feedwater dosing pump and auxiliary economizer should be stopped. When the system pressure drops below 0.2 MPa, attention should be paid to the drainage of water at each point to maintain steam flow and prevent water accumulation and corrosion inside the system. The water supply valve should be adjusted in a timely manner according to the water consumption and the water level in the demineralized water tank to ensure sufficient water supply and avoid waste of resources. When the temperature of the pre-storage section of the dry quenching furnace drops to the range of 50°C to 100°C, a large amount of air should be introduced for system cooling. At this time, the inspection port of the secondary dust collector and its upper explosion-proof valve should be fully opened, and while purging the air in the gas circulation system, the dead corners of the boiler should be purged regularly. The dust in the secondary dust collector should be manually discharged, and the dead corners in the gas circulation system should be cleaned to thoroughly remove residues.

[0024] Throughout the cooling process, the pressure regulating valve in the pre-storage section remains open, and the air inlet valves are also fully open to promote airflow and accelerate cooling. When the pre-storage section of the dry quenching furnace reaches the target temperature of 50°C, the final gas composition test is performed. The test standards remain the same: CO content below 24 ppm, H2 content below 10 ppm, and O2 content above 18%. After passing the test, the cooling process officially ends.

[0025] The equipment shutdown procedure must also be strictly followed in sequence. First, stop the operation of the circulating fan, desulfurization and dust removal fan, and boiler feed water pump. Then, open all manholes in the boiler, dry quenching furnace, discharge device, dust collector, etc., to release residual gas and accelerate heat dissipation. Subsequently, stop the operation of the environmental dust removal fan. Two hours after all equipment has stopped operating, stop the cooling water supply to each unit to complete the dry quenching coke oven shutdown operation.

[0026] Through the specific implementation steps described above, this invention achieves rapid shutdown of the dry quenching coke system. Phased control of the cooling rate and optimization of the operation procedures for key components significantly shortens shutdown time and reduces damage to the refractory masonry caused by excessive temperature differences. Precise control of the circulating air volume, nitrogen charge, and coke discharge rate ensures balanced cooling across the entire system, improving system stability and safety. Furthermore, refined operation of the boiler and dust removal systems effectively avoids equipment corrosion and abnormal gas composition, enhancing the reliability and environmental friendliness of the shutdown process.

[0027] In the above embodiments, when dry quenching requires shutdown, the dry quenching unit begins load reduction operation, that is, gradually reducing the coke discharge rate and the circulating air volume. Load reduction must be carried out slowly; large increases or decreases in the coke discharge rate and air volume are not permitted. When reducing the load, the coke discharge rate must be reduced first, followed by the air volume. Throughout the cooling process, efforts should be made to achieve balanced and synchronized cooling across the entire system to minimize damage to the refractory masonry caused by excessive temperature differences. Any deviations must be adjusted promptly. During the dry quenching shutdown process, the oxygen concentration inside the furnace must be kept below 6%; otherwise, an explosion or fire may occur. Therefore, before shutdown, the furnace needs to be purged with nitrogen to control the oxygen content in the gas within a safe range.

[0028] In the initial stage of cooling operation, the coke in the dry quenching furnace should be discharged to about 1 meter below the lower edge of the inclined chute. After the coke discharge stops, dry quenching cannot be carried out; instead, wet quenching must be used to maintain normal production of the coke oven.

[0029] The cooling process is carried out in two stages, as shown in Table 1: Table 1 shows the parameters for the two stages.

[0030] Standard for the end of cooling of dry quenching unit: The temperature near each manhole reached approximately 50°C.

[0031] The circulating gas is sampled from the top sampling port of the dust collector and tested. The following data are considered acceptable: CO: 0% (below 24ppm), H2: 0% (below 10ppm), O2: above 18%.

[0032] This invention strictly controls the cooling rate and proceeds in two steps.

[0033] 1. The temperature drop range is between 900℃ and 450℃. The cooling rate is controlled by changing the circulating air volume, nitrogen charge, and intermittent coke discharge.

[0034] The air vent valve is opened or closed based on the gas composition inside the circulating system and the boiler inlet temperature.

[0035] The pressure of the pre-storage section is controlled at 50Pa to 100Pa using the pre-storage section pressure regulating valve.

[0036] Open the nitrogen charging valves at the inlet of the circulating fan and the inlet of the dry quenching furnace.

[0037] When the nitrogen charge is changed, the pressure in the pre-storage section will also change accordingly. At this time, the pressure in the pre-storage section should be adjusted using a pressure regulating valve.

[0038] When the cooling rate is too fast, the following methods can be used to adjust it.

[0039] Slowly reduce the circulating air volume; Reduce the amount of nitrogen introduced; Stop the discharge of coke.

[0040] When the cooling rate is too slow, the following methods can be used to adjust it.

[0041] Slowly increase the circulating air volume; Increase the amount of nitrogen introduced; Intermittent coke removal is carried out.

[0042] As the evaporation rate decreases, the operating equipment and control methods of the boiler system must also be adjusted accordingly.

[0043] Once the discharge device stops operating, appropriate chemicals can be intermittently added to the furnace based on the water quality test results.

[0044] As the boiler inlet temperature decreases, the main steam temperature and pressure also decrease. At this time, the main steam pressure regulating valve can be fully opened, and the main steam pressure relief regulating valve can be used to control the steam drum pressure.

[0045] To prevent the temperature from dropping too quickly, manually close all the desuperheating water regulating valves. If a large temperature difference is found between the steam before and after the desuperheater, manually close all the manual valves before it.

[0046] When continuous boiler feedwater cannot be provided, the deaerator should be stopped. This involves gradually reducing the deaerator pressure and temperature by 10°C / h until the deaerator outlet valve is fully closed manually. After that, the manual valve before the deaerator should be closed.

[0047] During the coke removal process, the operator must strictly monitor the coke removal temperature to ensure it remains below 150℃.

[0048] II. Temperature drop range of 50℃ to 450℃ Follow the steps below to confirm that all the coke in the dry quenching furnace has been extinguished.

[0049] Confirmation time: When the temperature of the pre-storage chamber of the dry quenching furnace reaches below 450℃, manually open the furnace cover on site, visually check whether all the coke has been extinguished, and close the furnace cover after confirmation.

[0050] After confirming that the coke has been completely extinguished, close the nitrogen charging valve.

[0051] The coke in the dry quenching furnace continues to be discharged according to plan. When discharging coke on site, it should be confirmed at the conveyor belt that no red coke is being discharged.

[0052] When the temperature in the pre-storage chamber of the dry quenching furnace reaches 100℃~300℃, air is introduced into the system for cooling. Before performing this step, it must be confirmed that the coke inside the system has been completely extinguished.

[0053] Open all the commonly used vent valves in the pre-storage section at the top of the dry quenching furnace.

[0054] Manually move the loading device to open the furnace lid.

[0055] Open the emergency vent valve at the boiler inlet.

[0056] Open both manhole covers to confirm the safety of the gas composition.

[0057] Air is introduced into the system for cooling.

[0058] The boiler system should continue to cool and depressurize, and the following operations should be performed.

[0059] When the water supply is very small, water can be supplied to the boiler intermittently, and the feedwater dosing pump and auxiliary economizer should be stopped.

[0060] When the system pressure drops below 0.2 MPa, pay attention to the drainage of condensate at each point to maintain steam flow and prevent water accumulation and corrosion inside the system.

[0061] Adjust the water supply valve promptly based on water consumption and the water level in the demineralized water tank.

[0062] When the temperature in the pre-storage chamber of the dry quenching furnace reaches 50℃~100℃, a large amount of air is introduced to cool the system.

[0063] Open all inspection ports of the secondary dust collector and its upper explosion-proof valve.

[0064] While the air is being purged in the gas circulation system, dead corners in all parts of the boiler must also be purged regularly.

[0065] Manually drain the dust from the secondary dust collector.

[0066] Clean the dead corners inside the gas circulation system.

[0067] All pressure regulating valves in the pre-storage section are open, and all air inlet valves are open.

[0068] When the pre-storage chamber of the dry quenching furnace reaches the target temperature (50℃), the gas composition is tested. Once the composition is deemed acceptable, the cooling process ends.

[0069] Cooling end criteria: The temperature near each manhole reached approximately 50°C.

[0070] The circulating gas is sampled from the top sampling port of the dust collector and tested. The following data are considered acceptable: CO: 0% (below 24ppm) H2: 0% (below 10ppm) O2: above 18% Stop the operation of the circulating fan, desulfurization and dust removal fan, and boiler feed water pump.

[0071] All manholes in the boiler, dry quenching furnace, exhaust system, dust removal system, etc., are opened.

[0072] Stop the operation of the environmental dust removal fan.

[0073] Two hours after all equipment stops operating, the cooling water supply to each unit will be stopped.

[0074] The dry quenching furnace shutdown operation is complete.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapid shutdown of a dry quenching system, characterized in that, include: Gradually reduce the amount of coke discharged and the air volume in the circulating air duct; The cooling rate is controlled by changing the circulating air volume, nitrogen charge, and intermittent coke discharge. The pressure in the pre-storage section is maintained at 50Pa to 100Pa using the pre-storage section pressure regulating valve; When the cooling rate exceeds the first theoretical threshold, measures such as slowly reducing the circulating air volume, reducing the nitrogen charge, and stopping the coke discharge should be taken. When the cooling rate is less than the second theoretical threshold, measures such as slowly increasing the circulating air volume, increasing the nitrogen charge, and intermittent coke removal are taken. Based on the water quality test results, chemicals are intermittently added to the boiler. As the boiler inlet temperature decreases, the main steam temperature and pressure also decrease. At this time, the main steam pressure relief regulating valve is fully opened, and the main steam pressure relief regulating valve is used to control the steam drum pressure. Manually close all desuperheating water regulating valves; if the temperature difference between the steam before and after the desuperheater is greater than the third theoretical threshold, manually close all the manual valves before it. When continuous boiler feedwater cannot be provided, stop the deaerator operation, gradually reduce the deaerator pressure and temperature by 10°C per hour, until the deaerator outlet valve is manually closed completely, and then close the preceding manual valve.

2. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, When the temperature of the pre-storage section of the dry quenching furnace drops below 450℃, the furnace cover is manually opened on site to visually confirm whether the coke has been completely extinguished. After confirmation, the furnace cover is closed.

3. The rapid shutdown method for a dry quenching system according to claim 2, characterized in that, After confirming that the coke has been completely extinguished, close the nitrogen charging valve at the inlet of the circulating fan and the nitrogen charging valve at the inlet of the dry quenching furnace.

4. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, When the temperature of the pre-storage section of the dry quenching furnace drops to the range of 100℃ to 300℃, air is introduced into the system for cooling. Before operation, it must be confirmed that the coke inside the system is completely extinguished.

5. The rapid shutdown method for a dry quenching system according to claim 4, characterized in that, Open all the commonly used vent valves in the pre-storage section at the top of the dry quenching furnace, manually move the loading device to open the furnace cover, and open the emergency vent valve at the boiler inlet.

6. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, Open both manhole covers to confirm the safety of the gas composition. The testing standards are: CO content below 24 ppm, H2 content below 10 ppm, and O2 content above 18%.

7. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, When the system pressure drops below 0.2 MPa, pay attention to drainage at all points, maintain steam flow, and avoid water accumulation and corrosion inside the system.

8. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, When the temperature of the pre-storage section of the dry quenching furnace drops to 100℃~50℃, air is introduced for system cooling.

9. The rapid shutdown method for a dry quenching system according to claim 8, characterized in that, Open all inspection ports of the secondary dust collector and its upper explosion-proof valve, and while purging the air in the gas circulation system, regularly purge the dead corners of the boiler.

10. The rapid shutdown method for a dry quenching system according to claim 1, characterized in that, Stop the operation of the circulating fan, desulfurization and dust removal fan, and boiler feed water pump; open all manholes of the boiler, dry quenching furnace, discharge device, and dust removal equipment; stop the operation of the environmental dust removal fan; and stop the cooling water supply to each unit 2 hours after all equipment has stopped operating.

Images