【Daily Question No. 295】October 28, 2018
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【Daily Question No. 295】October 28, 2018: Briefly describe the precautions for an emergency shutdown of a hydrogenation unit (1) When carrying out emergency measures, it is first necessary to take proper personal protective actions to prevent serious accidents such as hydrogen sulfide poisoning. (2) In the event of a leakage accident, remain calm and first carry out preliminary rescue and containment actions in accordance with the operational procedures for the position and the accident response plan. In the event of an H2S leak, wear an air respirator, set up warning ropes to prevent unauthorized personnel from entering, control the situation and stop the accident from spreading. (3) In the event of an accident at the facility, the shift leader must assign personnel to promptly inform the facility’s management, chief technical officers, those on duty, dispatch staff, fire fighters, and gas safety personnel. Once the management arrives at the scene, rescue efforts shall be carried out under their unified command. (4) In the event of a fire, explosion, or poisoning incident, the first step is to find a way to cut off the source of danger, move those who are injured or poisoned to a safe place, and provide first aid. During the rescue process, it is essential to first ensure the safety of the rescuers themselves in order to prevent the accident from escalating. When it is impossible to cut off the source of danger, steam should be used as a shield. (5) Production accidents such as power outages, machine shutdowns, and water interruptions should be handled calmly and methodically in accordance with the following principles: shut down the heating furnace, stop feeding material, relieve pressure to maintain flow of the medium in the reaction system, implement emergency liquid-controlled shutdown of the high-pressure separator, protect the equipment and catalysts, and prevent high pressure from leaking into the low-pressure system. (6) In the event of a high-pressure system leaking into a low-pressure system, it is necessary to first urgently close the high-pressure level/boundary control valves and shut-off valves at the site; if these measures are ineffective, an emergency pressure relief valve must be activated immediately to relieve pressure urgently. When the emergency pressure relief valve opens, it is necessary to notify the dispatch team and relevant units in advance so that they can prepare the low-pressure gas system. It is also important to prevent gas from flowing back into the low-pressure system or from building up pressure inside the device as a result of pressure control. Generally, the reaction system is shut down urgently, while distillation continues to operate in a circular mode. The fractionation system was shut down urgently, while the reaction system maintained compressor circulation. Minimize downtime losses. (7) During emergency shutdown, it is important to maintain proper material balance to prevent adverse situations such as full tanks or empty liquid levels. In particular, care must be taken to prevent oil from entering the heater via the high-pressure gas system, as this could cause the heater to catch fire. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Correct: 3 wealth, Incorrect: 1 wealth ； Mass posting of posts – rated based on the lowest score ； Replies that are unrelated to the answer are considered spam and will be deleted immediately. For management purposes, if you need to view content from a few days ago, please go to https://bbs.hcbbs.com/home.php?mod=space&uid=3862647&do=thread&view=me&from=space through the summary post below
①Confirm that the jacket steam and steaming steam for each emission system are in operation； ②Confirm whether CO has been added to each leg of the loop reactor ； ③Verify whether the emergency discharge valves of the large and small loop reactors are open ； ④Verify whether the outlet line of the flash line or the outlet line of the flash tank is switched to the discharge position ； ⑤Verify whether the high flash temperature control valve is closed; it should be manually kept at a certain opening degree ； ⑥Confirm whether the flash tank, bag filter, steam vessel, and dryer have been emptied ； ⑦Confirm that nitrogen is used to maintain pressure in the bag filter and steam drum ； ⑧Verify whether the hydrogen compressor, exhaust gas compressor, and low-pressure propylene recovery compressor are stopped.
1. Follow the principle of cooling first and then reducing the flow rate to prevent the bed layer from overheating. 2. During the cooling and depressurization of the reaction system, it is necessary to strictly adhere to the relevant constraints regarding the cooling and depressurization of the reactor, in order to reduce the impact of temper brittleness on chromium-molybdenum steel. 3. During the cooling and pressure reduction of the reaction system, operations must be carried out strictly in accordance with the established plan, to prevent significant fluctuations and avoid leaks in the equipment, flanges, etc. 4. During the shutdown period, if the high-temperature flange is equipped with a fixed steam protection ring, it should be put into use. 5. If it is necessary to open the reactor after shutdown, CO content in the recycle gas should be analyzed until the temperature of any bed in the reaction system drops to 205°C, in order to prevent the formation of highly toxic nickel carbonyl during the shutdown process. Regarding the temper brittleness of chromium-molybdenum steel, pressure limits must be observed during shutdown, and the cooling rate should be less than 25°C/h ； When opening stainless steel equipment, be aware of the risk of stress corrosion cracking due to hydrosulfuric acid ； Before opening the reactor, it must be cooled to below 40°C, and simultaneously purged thoroughly with nitrogen to reduce the risk of spontaneous combustion from hydrocarbon-oxygen compounds and iron sulfide. 6. During the shutdown process, closely monitor the changes in bed pressure drop and bed temperature rise. Outdoor operators should enhance their inspections and report any leaks or similar issues promptly for handling. 7. The purging during the shutdown process is carried out strictly in accordance with the requirements. 8. During the shutdown, the reaction system is depressurized, while the nitrogen line continues to supply nitrogen. The fractionation system and the nitrogen lines of the new hydrogen generator system are isolated using blind flanges. When purging the system with nitrogen, implement proper isolation procedures to prevent the nitrogen from spreading uncontrollably. 9. It is strictly prohibited to discharge oil into floor drains or open ditches during the shutdown purging process. 10. To prevent catalyst damage, after feeding to the reactor is stopped, the system should be kept circulating with the highest possible amount of recycled hydrogen until the oil in the feed lines and the reactor has been completely purged. 11. After stopping the feed, flush hydrogen should be introduced immediately into the fresh feed line; the introduction of hydrogen must be done slowly to prevent high-pressure flanges from leaking due to thermal shock ； When a flange leaks due to cooling, steam should be used promptly to purge the oil and gas in order to prevent ignition. 12. The distillation system should avoid vacuum formation due to overcooling in the columns; if steam purging is not carried out in a column temporarily, nitrogen should be introduced into the top reflux drum to maintain positive pressure. 13. The contaminated oil must be thoroughly stripped before being discharged into the contaminated oil system, to prevent hydrogen sulfide from causing harm to operators.
1. First reduce the temperature and then reduce the flow rate to prevent the bed layer from overheating. 2. Strictly adhere to the constraints regarding reactor cooling and pressure reduction in order to minimize the impact of temper brittleness on chromium-molybdenum steel. 3. Operate strictly in accordance with the plan to avoid significant fluctuations and prevent leaks in the equipment, flanges, etc. 4. During the shutdown period, if the high-temperature flange is equipped with a fixed steam protection ring, it should be put into use. 5. If the reactor needs to be opened after shutdown, a CO content analysis of the circulating gas should be conducted before the temperature of any bed in the reaction system drops to 205°C. Regarding the temper brittleness of chromium-molybdenum steel, pressure limits must be observed during shutdown, and the cooling rate should be less than 25°C/h ； When opening stainless steel equipment, be aware of the risk of stress corrosion cracking due to hydrosulfuric acid ； Before opening the reactor, it must be cooled to below 40°C, and simultaneously purged thoroughly with nitrogen to reduce the risk of spontaneous combustion from hydrocarbon-oxygen compounds and iron sulfide. 6. During the shutdown process, closely monitor the changes in bed pressure drop and bed temperature rise. Outdoor operators should enhance their inspections and report any leaks or similar issues promptly for handling. 7. The purging during the shutdown process is carried out strictly in accordance with the requirements. 8. The nitrogen line maintains nitrogen supply. The fractionation system and the nitrogen lines of the new hydrogen generator system are isolated using blind flanges. When purging the system with nitrogen, implement proper isolation procedures to prevent the nitrogen from spreading uncontrollably. 9. It is strictly prohibited to discharge oil into floor drains or open ditches during the shutdown purging process. 10. To prevent catalyst damage, after feeding to the reactor is stopped, the system should be kept circulating with the highest possible amount of recycled hydrogen until the oil in the feed lines and the reactor has been completely purged. 11. After stopping the feed, flush hydrogen should be introduced immediately into the fresh feed line; the introduction of hydrogen must be done slowly to prevent high-pressure flanges from leaking due to thermal shock ； When a flange leaks due to cooling, steam should be used promptly to purge the oil and gas in order to prevent ignition. 12. The distillation system should avoid vacuum formation due to overcooling in the columns; if steam purging is not carried out in a column temporarily, nitrogen should be introduced into the top reflux drum to maintain positive pressure. 13. The contaminated oil must be thoroughly stripped before being discharged into the contaminated oil system, to prevent hydrogen sulfide from causing harm to operators.
Emergency shutdowns of hydrogen-handling high-pressure units are mostly interlock shutdowns. Precautions after the hydrogenation unit shuts down due to interlocks: 1. Immediately verify the status of each interlock action – whether each interlock condition has been triggered, and whether the corresponding actions have been initiated and completed ； 2. Verify the isolation of high and low pressure areas and implement more secure safeguards; in areas where cross-contamination is possible, manual valves must be closed to achieve isolation ； 3. Thorough isolation of the heating furnace and fuel gas system, with manual valves closed ； 4. Pay attention to the static sealing points in areas with high temperature and pressure, to prevent seal failure due to significant fluctuations in process conditions, which could lead to the leakage of sulfur-rich fluids and cause poisoning among personnel; on-site workers should wear portable gas detectors ； 5. Protection of critical equipment: the unit is rotated in a timely manner as required, and steam is introduced into the furnace for purging, etc
1. First reduce the temperature and then reduce the flow rate to prevent the bed layer from overheating. 2. Strictly adhere to the constraints regarding reactor cooling and pressure reduction in order to minimize the impact of temper brittleness on chromium-molybdenum steel. 3. Operate strictly in accordance with the plan to avoid significant fluctuations and prevent leaks in the equipment, flanges, etc. 4. During the shutdown period, if the high-temperature flange is equipped with a fixed steam protection ring, it should be put into use. 5. If the reactor needs to be opened after shutdown, a CO content analysis of the circulating gas should be conducted before the temperature of any bed in the reaction system drops to 205°C. Regarding the temper brittleness of chromium-molybdenum steel, pressure limits must be observed during shutdown, and the cooling rate should be less than 25°C/h ； When opening stainless steel equipment, be aware of the risk of stress corrosion cracking due to hydrosulfuric acid ； Before opening the reactor, it must be cooled to below 40°C, and simultaneously purged thoroughly with nitrogen to reduce the risk of spontaneous combustion from hydrocarbon-oxygen compounds and iron sulfide. 6. During the shutdown process, closely monitor the changes in bed pressure drop and bed temperature rise. Outdoor operators should enhance their inspections and report any leaks or similar issues promptly for handling. 7. The purging during the shutdown process is carried out strictly in accordance with the requirements. 8. The nitrogen line maintains nitrogen supply. The fractionation system and the nitrogen lines of the new hydrogen generator system are isolated using blind flanges. When purging the system with nitrogen, implement proper isolation procedures to prevent the nitrogen from spreading uncontrollably. 9. It is strictly prohibited to discharge oil into floor drains or open ditches during the shutdown purging process. 10. To prevent catalyst damage, after feeding to the reactor is stopped, the system should be kept circulating with the highest possible amount of recycled hydrogen until the oil in the feed lines and the reactor has been completely purged. 11. After stopping the feed, flush hydrogen should be introduced immediately into the fresh feed line; the introduction of hydrogen must be done slowly to prevent high-pressure flanges from leaking due to thermal shock ； When a flange leaks due to cooling, steam should be used promptly to purge the oil and gas in order to prevent ignition. 12. The distillation system should avoid vacuum formation due to overcooling in the columns; if steam purging is not carried out in a column temporarily, nitrogen should be introduced into the top reflux drum to maintain positive pressure. 13. The contaminated oil must be thoroughly stripped before being discharged into the contaminated oil system, in order to prevent hydrogen sulfide from causing harm to operators
1. Follow the principle of cooling first and then reducing the flow rate to prevent the bed layer from overheating. 2. During the cooling and depressurization of the reaction system, it is necessary to strictly adhere to the relevant constraints regarding the cooling and depressurization of the reactor, in order to reduce the impact of temper brittleness on chromium-molybdenum steel. 3. During the cooling and pressure reduction of the reaction system, operations must be carried out strictly in accordance with the established plan, to prevent significant fluctuations and avoid leaks in the equipment, flanges, etc. 4. During the shutdown period, if the high-temperature flange is equipped with a fixed steam protection ring, it should be put into use. 5. If it is necessary to open the reactor after shutdown, CO content in the recycle gas should be analyzed until the temperature of any bed in the reaction system drops to 205°C, in order to prevent the formation of highly toxic nickel carbonyl during the shutdown process. Regarding the temper brittleness of chromium-molybdenum steel, pressure limits must be observed during shutdown, and the cooling rate should be less than 25°C/h ； When opening stainless steel equipment, be aware of the risk of stress corrosion cracking due to hydrosulfuric acid ； Before opening the reactor, it must be cooled to below 40°C, and simultaneously purged thoroughly with nitrogen to reduce the risk of spontaneous combustion from hydrocarbon-oxygen compounds and iron sulfide. 6. During the shutdown process, closely monitor the changes in bed pressure drop and bed temperature rise. Outdoor operators should enhance their inspections and report any leaks or similar issues promptly for handling. 7. The purging during the shutdown process is carried out strictly in accordance with the requirements. 8. During the shutdown, the reaction system is depressurized, while the nitrogen line continues to supply nitrogen. The fractionation system and the nitrogen lines of the new hydrogen generator system are isolated using blind flanges. When purging the system with nitrogen, implement proper isolation procedures to prevent the nitrogen from spreading uncontrollably. 9. It is strictly prohibited to discharge oil into floor drains or open ditches during the shutdown purging process. 10. To prevent catalyst damage, after feeding to the reactor is stopped, the system should be kept circulating with the highest possible amount of recycled hydrogen until the oil in the feed lines and the reactor has been completely purged. 11. After stopping the feed, flush hydrogen should be introduced immediately into the fresh feed line; the introduction of hydrogen must be done slowly to prevent high-pressure flanges from leaking due to thermal shock ； When a flange leaks due to cooling, steam should be used promptly to purge the oil and gas in order to prevent ignition. 12. The distillation system should avoid vacuum formation due to overcooling in the columns; if steam purging is not carried out in a column temporarily, nitrogen should be introduced into the top reflux drum to maintain positive pressure. 13. The contaminated oil must be thoroughly stripped before being discharged into the contaminated oil system, in order to prevent hydrogen sulfide from causing harm to operators
①Confirm that the jacket steam and steaming steam for each emission system are in operation； ②Confirm whether CO has been added to each leg of the loop reactor ； ③Verify whether the emergency discharge valves of the large and small loop reactors are open ； ④Verify whether the outlet line of the flash line or the outlet line of the flash tank is switched to the discharge position ； ⑤Verify whether the high flash temperature control valve is closed; it should be manually kept at a certain opening degree ； ⑥Confirm whether the flash tank, bag filter, steam vessel, and dryer have been emptied ； ⑦Confirm that nitrogen is used to maintain pressure in the bag filter and steam drum ； ⑧Verify whether the hydrogen compressor, exhaust gas compressor, and low-pressure propylene recovery compressor are stopped.
(1) In the event of an emergency shutdown, it is necessary to report immediately to the workshop and the factory’s production management department. (2) Immediately notify the relevant upstream and downstream devices. (3) The team leader coordinates and directs the relevant personnel to safely shut down the equipment. (4) When shutting down operations, the principle of addressing priorities first and then secondary matters must be followed. (5) The conversion system should maintain gas flow as much as possible to protect the catalyst and facilitate production resumption after an accident. (6) Take necessary measures to protect the safety of personnel, the environment, equipment, and catalysts during the shutdown process.
(1) When carrying out emergency measures, it is first necessary to take proper personal protective actions to prevent serious accidents such as hydrogen sulfide poisoning. (2) In the event of a leakage accident, remain calm and first carry out preliminary rescue and containment actions in accordance with the operational procedures for the position and the accident response plan. In the event of an H2S leak, wear an air respirator, set up warning ropes to prevent unauthorized personnel from entering, control the situation and stop the accident from spreading. (3) In the event of an accident at the facility, the shift leader must assign personnel to promptly inform the facility’s management, chief technical officers, those on duty, dispatch staff, fire fighters, and gas safety personnel. Once the management arrives at the scene, rescue efforts shall be carried out under their unified command. (4) In the event of a fire, explosion, or poisoning incident, the first step is to find a way to cut off the source of danger, move those who are injured or poisoned to a safe place, and provide first aid. During the rescue process, it is essential to first ensure the safety of the rescuers themselves in order to prevent the accident from escalating. When it is impossible to cut off the source of danger, steam should be used as a shield. (5) Production accidents such as power outages, machine shutdowns, and water interruptions should be handled calmly and methodically in accordance with the following principles: shut down the heating furnace, stop feeding material, relieve pressure to maintain flow of the medium in the reaction system, implement emergency liquid-controlled shutdown of the high-pressure separator, protect the equipment and catalysts, and prevent high pressure from leaking into the low-pressure system. (6) In the event of a high-pressure system leaking into a low-pressure system, it is necessary to first urgently close the high-pressure level/boundary control valves and shut-off valves at the site; if these measures are ineffective, an emergency pressure relief valve must be activated immediately to relieve pressure urgently. When the emergency pressure relief valve opens, it is necessary to notify the dispatch team and relevant units in advance so that they can prepare the low-pressure gas system. It is also important to prevent gas from flowing back into the low-pressure system or from building up pressure inside the device as a result of pressure control. Generally, the reaction system is shut down urgently, while distillation continues to operate in a circular mode. The fractionation system was shut down urgently, while the reaction system maintained compressor circulation. Minimize downtime losses. (7) During emergency shutdown, it is important to maintain proper material balance to prevent adverse situations such as full tanks or empty liquid levels. In particular, care must be taken to prevent oil from entering the heater via the high-pressure gas system, as this could cause the heater to catch fire.
(1) When carrying out emergency measures, it is first necessary to take proper personal protective actions to prevent serious accidents such as hydrogen sulfide poisoning. (2) In the event of a leakage accident, remain calm and first carry out preliminary rescue and containment actions in accordance with the operational procedures for the position and the accident response plan. In the event of an H2S leak, wear an air respirator, set up warning ropes to prevent unauthorized personnel from entering, control the situation and stop the accident from spreading. (3) In the event of an accident at the facility, the shift leader must assign personnel to promptly inform the facility’s management, chief technical officers, those on duty, dispatch staff, fire fighters, and gas safety personnel. Once the management arrives at the scene, rescue efforts shall be carried out under their unified command. (4) In the event of a fire, explosion, or poisoning incident, the first step is to find a way to cut off the source of danger, move those who are injured or poisoned to a safe place, and provide first aid. During the rescue process, it is essential to first ensure the safety of the rescuers themselves in order to prevent the accident from escalating. When it is impossible to cut off the source of danger, steam should be used as a shield. (5) Production accidents such as power outages, machine shutdowns, and water interruptions should be handled calmly and methodically in accordance with the following principles: shut down the heating furnace, stop feeding material, relieve pressure to maintain flow of the medium in the reaction system, implement emergency liquid-controlled shutdown of the high-pressure separator, protect the equipment and catalysts, and prevent high pressure from leaking into the low-pressure system. (6) In the event of a high-pressure system leaking into a low-pressure system, it is necessary to first urgently close the high-pressure level/boundary control valves and shut-off valves at the site; if these measures are ineffective, an emergency pressure relief valve must be activated immediately to relieve pressure urgently. When the emergency pressure relief valve opens, it is necessary to notify the dispatch team and relevant units in advance so that they can prepare the low-pressure gas system. It is also important to prevent gas from flowing back into the low-pressure system or from building up pressure inside the device as a result of pressure control. Generally, the reaction system is shut down urgently, while distillation continues to operate in a circular mode. The fractionation system was shut down urgently, while the reaction system maintained compressor circulation. Minimize downtime losses. (7) During emergency shutdown, it is important to maintain proper material balance to prevent adverse situations such as full tanks or empty liquid levels. In particular, care must be taken to prevent oil from entering the heater via the high-pressure gas system, as this could cause the heater to catch fire.