[Q&A Question 330] 2017.12.14
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【Q&A Question 330】December 14, 2017: Causes and treatment methods for hot spots, hot zones, and hot tubes in the tubes of hydrogen production conversion furnaces. Reason: ① The main causes of hot spots are uneven catalyst packing, bridging, and localized carbon deposition. ②The overheating in the upper section of the furnace tube may be caused by insufficient catalyst reduction or deactivation due to sulfur poisoning, significant fluctuations in feed rate or water-to-carbon ratio, uneven burner operation, or localized overheating and carbon deposition. ③The formation of a hot zone in the lower section of the furnace tube may be caused by a decline in the activity of the catalyst in that section, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst in the lower section leading to carbon deposition, or catalyst fragmentation. ④When the catalyst is severely coked or damaged, it causes blockages in the tubes, as well as blockages in the inlet tail pipe or gas guide sieve plates, thereby affecting the heat pipes. Treatment: Feed with a low load and high carbon-to-water ratio, or stop operation for carbon burning; if neither method works, the catalyst needs to be replaced. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) For management purposes, if you need to view content from a few days ago, please go through the summary post below. 2017 Q&A Summary Thread (updates have begun) https://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) https://bbs.hcbbs.com/thread-1657794-1-1.html 2017 Daily Image Summary Thread https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1875160 2017 LNG Version Daily Question List https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1804162 2016 Q&A Summary Thread (updates completed) https://bbs.hcbbs.com/thread-1597792-1-1.html
Answer: The reasons for the formation of hot spots include \"bridging\" caused by improper catalyst loading, localized carbon deposition, or partial poisoning of the catalyst. Local overheating and carbon deposition in the upper bed layer may be caused by insufficient catalyst reduction, sulfur poisoning, significant fluctuations in feed rate and water-to-carbon ratio, uneven burner operation, or partial burning. The tropical zone in the lower bed layer may be caused by factors such as declining activity of the catalyst in the lower section, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst deposits in the lower section, and catalyst crushing. When the catalyst becomes severely caked or crushed, it causes blockages in the tubes, forming heat pipes. Sometimes, blockages in the inlet and outlet tail pipes or the air guide sieve holes can also create heat pipes. The main cause of the aforementioned phenomenon is carbon buildup. Mild hot spots and hot zones can be eliminated by using adjustable burners as a method to improve operating conditions ； When heat pipes appear, carbonization treatment is required. If the heat pipes do not disappear after carbonization, the operation must be stopped and the catalyst replaced to prevent damage to the furnace tubes. To prevent the formation of heat pipes, it is necessary to ensure uniform catalyst distribution, minimal variation in bed resistance, thorough reduction, complete purification of the raw materials, and even adjustment of the furnace nozzles in order to avoid local overheating. It is also necessary to avoid fluctuations in feed rate, water-to-carbon ratio, and pressure, in order to prevent catalyst hydration.
The causes of hot spots include \"bridging\" resulting from improper catalyst packing, localized carbon deposition, or partial poisoning of the catalyst. Local overheating and carbon deposition in the upper bed layer may be caused by insufficient catalyst reduction, sulfur poisoning, significant fluctuations in feed rate and water-to-carbon ratio, uneven burner operation, or partial burning. The tropical zone in the lower bed layer may be caused by factors such as declining activity of the catalyst in the lower section, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst deposits in the lower section, and catalyst crushing. When the catalyst becomes severely caked or crushed, it causes blockages in the tubes, forming heat pipes. Sometimes, blockages in the inlet and outlet tail pipes or the air guide sieve holes can also create heat pipes. The main cause of the aforementioned phenomenon is carbon buildup. Mild hot spots and hot zones can be eliminated by using adjustable burners as a method to improve operating conditions ； When heat pipes appear, carbonization treatment is required. If the heat pipes do not disappear after carbonization, the operation must be stopped and the catalyst replaced to prevent damage to the furnace tubes. To prevent the formation of heat pipes, it is necessary to ensure uniform catalyst distribution, minimal variation in bed resistance, thorough reduction, complete purification of the raw materials, and even adjustment of the furnace nozzles in order to avoid local overheating. It is also necessary to avoid fluctuations in feed rate, water-to-carbon ratio, and pressure, in order to prevent catalyst hydration.
Reduce the load by 50-60% and increase the water-to-carbon ratio to resume production
Reasons: 1) The occurrence of hot spots is mainly due to uneven catalyst packing, bridging, and localized carbon deposition. 2) Hot spots in the upper section of the furnace tubes may be caused by insufficient catalyst reduction or sulfur poisoning leading to deactivation, large fluctuations in feed rate or water-to-carbon ratio, uneven burner operation, or localized overheating resulting in carbon deposition. 3) Hot spots in the lower section of the furnace tubes can be caused by reduced activity of the catalyst in that section, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst in the lower section leading to carbon deposition, or catalyst fragmentation. 4) When the catalyst is severely carbon-deposited or fragmented, it can cause tube blockages, as well as blockages in the inlet tail pipes or gas distribution plates, thereby leading to hot spots. Solutions: 1) Feed at a low load with a high water-to-carbon ratio. 2) Stop operations for carbon burning. 3) If neither of these methods works, the catalyst needs to be replaced
Catalyst poisoning, coking, an excessively low water-to-carbon ratio, and poor packing can all lead to problems; in such cases, production is usually reduced, and the water-to-carbon ratio is increased to facilitate carbon burning. If heat spots persist, it indicates that the catalyst is inactive and must be replaced
(1) The main reasons for the appearance of hot spots are uneven catalyst packing and localized carbon deposition due to bridging. (2) Hot spots in the upper section of the furnace tube may be caused by insufficient catalyst reduction or sulfur poisoning that leads to catalyst deactivation, as well as significant fluctuations in feed rate or water-to-carbon ratio; uneven burner operation or partial burning can also result in localized overheating and carbon deposition. (3) Hot spots in the lower section may be due to reduced catalyst activity, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst in the lower section, or catalyst fragmentation. (4) When the catalyst is severely carbonized or fragmented, it can cause blockages in the furnace tubes, as well as blockages in the inlet tail pipes or gas distribution plates, leading to the formation of hot spots. The main cause of these phenomena is carbon deposition; mild cases can be resolved by adjusting the burners and improving operating conditions； When heat pipes appear, carbon burning treatment is required. If the heat pipes do not disappear after this treatment, the furnace must be stopped and the catalyst replaced to prevent damage to the furnace tubes ； To prevent the formation of heat pipes, it is first necessary to ensure uniform catalyst packing, minimal variation in bed resistance, and thorough reduction. The raw materials must be thoroughly purified, the furnace nozzles must be adjusted evenly to avoid local overheating. Additionally, fluctuations in feed rate, water-to-carbon ratio, and pressure should be minimized to prevent catalyst hydration.
The causes of hot spots include \"bridging\" resulting from improper catalyst packing, localized carbon deposition, or partial poisoning of the catalyst. Local overheating and carbon deposition in the upper bed layer may be caused by insufficient catalyst reduction, sulfur poisoning, significant fluctuations in feed rate and water-to-carbon ratio, uneven burner operation, or partial burning. The tropical zone in the lower bed layer may be caused by factors such as declining activity of the catalyst in the lower section, uneven feed distribution, penetration of heavy hydrocarbons into the catalyst deposits in the lower section, and catalyst crushing. When the catalyst becomes severely caked or crushed, it causes blockages in the tubes, forming heat pipes. Sometimes, blockages in the inlet and outlet tail pipes or the air guide sieve holes can also create heat pipes. The main cause of the aforementioned phenomenon is carbon buildup. Mild hot spots and hot zones can be eliminated by using adjustable burners as a method to improve operating conditions ； When heat pipes appear, carbonization treatment is required. If the heat pipes do not disappear after carbonization, the operation must be stopped and the catalyst replaced to prevent damage to the furnace tubes. To prevent the formation of heat pipes, it is necessary to ensure uniform catalyst distribution, minimal variation in bed resistance, thorough reduction, complete purification of the raw materials, and even adjustment of the furnace nozzles in order to avoid local overheating. It is also necessary to avoid fluctuations in feed rate, water-to-carbon ratio, and pressure, in order to prevent catalyst hydration.