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Questions for the Dry Gas Hydrogen Production Conversion Position 1. What are the measures to prevent catalyst carbon deposition? Answer: (1) Select a catalyst with good activity, stability, and excellent anti-coking properties. (2) Improve the packing quality of the catalyst. (3) Carry out the reduction of the catalyst to enhance its activity. (4) Try not to work at high speeds. (5) Strictly control the feed to prevent large-molecule hydrocarbons from entering the converter. (6) Ensure that the conversion catalyst in the inlet section is in a reduced state during operation. (7) Strictly remove harmful substances from the raw materials. (8) Maintain an adequate water-carbon ratio during operation, while avoiding large fluctuations. (9) Strictly control the furnace temperature, while avoiding any significant fluctuations. (10) Improve the quality of superheated steam to prevent salt deposition on the catalyst. (11) Avoid frequent start-ups and shutdowns. 2. How to prevent carbon buildup during operation? Answer: (1) During operation, ensure that the conversion catalyst in the inlet section is in a reduced state. (2) Maintain an adequate water-carbon ratio during operation, while avoiding large fluctuations. (3) Strictly control the furnace temperature, while avoiding large fluctuations. (4) Improve the quality of superheated steam to prevent catalyst salt formation. (5) Try to avoid working at high speeds. (6) Strictly control the feedstock to prevent large-molecule hydrocarbons from entering the converter; rigorously remove harmful substances from the raw materials. 3. What is the effect of air velocity on the conversion reaction? Answer: The conversion rate of hydrocarbons decreases as the space velocity increases. This is because a higher space velocity results in a shorter residence time of the feed gas on the catalyst, leading to less complete conversion reactions. The appropriate space velocity should be selected based on factors such as the temperature of the conversion process, CH4 conversion rate, feed gas composition, and catalyst activity. (i.e., excessive space velocity leads to a decrease in conversion depth) 4. Where in the furnace tube is carbon deposition likely to occur for the converter? Reason? Answer: Location: Generally, it is the area accounting for 30%–40% of the length of the reformer tubes, i.e., at a point about 3–4 meters below the inlet of the reformer. Reason: Carbon deposition tends to occur during the conversion of gaseous hydrocarbons at temperatures above 650°C, while it occurs easily during the conversion of light oils at temperatures above 630°C. In the conversion furnace tubes, the temperature range of 630–675°C corresponds to the upper 30%–40% of the tube length. When a catalyst with low activity is present in this temperature range, a large amount of hydrocarbons remain unconverted, which can easily lead to the cracking of carbon deposits and the formation of methane; further cracking of methane then results in more carbon deposits. 5 What are the causes, symptoms, and solutions for short-term interruptions of the feed gas? Answer: Reason: (1) Failure of the dry gas supply unit, resulting in a loss of the raw gas source. (2) Compressor malfunction; it is unable to raise the pressure of the raw gas to the raw gas pretreatment system. (3) The control valve on the compressor return line is stuck in the fully open position. Phenomenon: (1) The inlet flow rate of the compressor indicates zero, and the inlet and outlet pressures have decreased. (2) The compressor outlet flow rate shows zero, the outlet pressure decreases, and the inlet pressure increases. (3) The outlet temperature of the heating furnace, as well as the inlet and outlet temperatures of the conversion furnace, increase. (4) Decrease in the feed flow rate to the converter, hydrogen production volume, and system pressure. Processing steps: (1) Contact the upstream unit to restore dry gas supply as soon as possible. (2) If the compressor fails, activate the backup unit immediately. (3) If the control valve fails, adjust the pressure at the secondary line control to stabilize it, and isolate the control valve for handling by the instrumentation staff. (4) During the interruption of the feed gas, appropriately reduce the temperature of the heater and converter to prevent overheating. 6. What are the causes, symptoms, and solutions for steam supply interruptions in converter furnaces? Answer: Reasons: (1) The safety valve of the steam drum activated; malfunction of the superheated steam temperature control valve. (2) Misoperation caused the steam distribution valve to close. (3) A rupture in the pipeline of the self-generated steam system caused a large amount of steam to leak. (4) A failure in the interlock valve shuts off the steam supply. Phenomenon: (1) The steam flow rate at the converter inlet decreases. (2) The pressure, liquid level, feedwater, and steam generation volume of the steam drum system fluctuate significantly. (3) Drop in converter inlet and system pressure. (4) The inlet temperature of the converter rises, along with the temperatures in the furnace chamber and the furnace tubes; the methane content at the converter outlet increases as well. (5) The medium gas volume and hydrogen production decrease. Treatment: (1) If the interruption in steam supply is caused by the activation of the drum safety valve, the conversion catalyst is not significantly affected; it is sufficient to reduce the production load, maintain an high water-to-carbon ratio, shut off the safety valve, and reset the pressure. (2) If the superheated steam temperature control valve fails to open, resulting in a disruption of steam supply to the conversion furnace, immediately go to the site to open the bypass line to restore steam supply, and cut off the feed to carry out carbon removal operations using a converter. After carbon removal is completed, proceed with reduction before resuming normal operation. (3) In the event that a large amount of steam leaks due to a rupture in the self-generated steam pipeline, it shall be treated as an emergency shutdown. (4) If the steam supply is interrupted due to a fault in the interlock valve, handle it as follows: a. Stabilize the drum liquid level and pressure, cut off the feed to the converter, and reduce the temperature of the converter. b. Stop feeding to the device; cease the supply of hydrogen outward. c. Go to the site immediately to activate the backup air supply or manually open the interlock valve in order to restore steam supply to the converter. d. Control the temperature of the conversion furnace, purge the system with high-pressure nitrogen, establish a circulation system for the conversion process, and remove carbon from the conversion catalyst. e. After the decarburization is completed, stop steam supply, initiate the nitrogen circulation, and properly handle the steam supply interlock valve. f. Conversion: re-distribution of steam and hydrogen reduction. 7. Causes, symptoms, and treatment of converter carbon deposition? Answer: Reason: a. Poor catalyst packing quality or insufficient reduction. b. Catalyst hydrolysis causes the catalyst to crumble, blocking the furnace tubes and resulting in red-colored tubes; it also increases the load on other furnace tubes, leading to coke formation. c. Catalyst poisoning and deactivation, leading to carbon buildup. d. Improper adjustment of the reformer burner leads to uneven combustion and flame impingement on the furnace tubes. e. Interruption of steam supply to the converter, too low water-to-carbon ratio, or pulse feeding. f. The catalyst’s performance has declined; it has reached the end of its useful life. g. High content of heavy hydrocarbon components in the feed. Phenomenon: a. The furnace tube shows mottling or turns red. b. Increase in furnace tube pressure drop. c. The methane content at the converter outlet increases. Treatment: a. When the coke deposition on the conversion catalyst is not severe, the load can be reduced, and a lighter feedstock can be used instead; the unit can then operate for some time under a high water-to-carbon ratio. If the effect is not significant, the feed is cut off, a circulating hydrogen stream during conversion is established, and carbon removal and regeneration are carried out in a reducing atmosphere. b. When severe carbon deposition occurs in the conversion catalyst, an oxidation-reduction method should be employed: (1) Stop the feed and establish a variable-cycle operation in the conversion reactor; reduce the system pressure to 1–1.8 Mpa and lower the steam supply to 30%-50% of the normal level. Operate for 12 hours, and if the carbon dioxide level at the outlet of the conversion reactor is high, replace it with nitrogen. (2) When the carbon dioxide levels at the inlet and outlet of the conversion furnace remain unchanged, liquid ammonia is added to the system for reduction, with the temperatures at the inlet and outlet of the conversion furnace being kept slightly higher than the normal operating values. (3) After analyzing that the catalyst no longer consumes hydrogen, run reduction for 8–12 hours. (4) When catalyst fouling is severe enough to cause blockage of the furnace tubes, operations must be halted to replace the catalyst. 8. Causes of soda azeotrope and its treatment? Answer: Reason: a. The temperature difference of the furnace water exceeds the specified range. b. The water quality is substandard. c. Excessively high water level. d. Excessive production load. e. No discharge for a long time. Treatment: a. When steam carrying water occurs, appropriately increase the inlet temperature of the converter to prevent catalyst hydrolysis. b. Strengthen the drainage from the surface and bottom of the drum to replace the drum water. c. Reduce the production load and strengthen drainage in steam pipelines. d. Strengthen water quality analysis to identify the root causes of substandard water quality. e. After the foaming phenomenon disappears and the boiler water meets the specifications, adjust the blowdown rate to normal levels. 9. What measures can be taken to extend the lifespan of catalysts? Answer: (1) During the start-up of conversion, it is essential to ensure that there are no hydrocarbons present in the recycle gas. Thorough permutation must be carried out before cycling, and the hydrocarbon content should be sampled and analyzed at 200°C; the compressor cycle should operate normally. c. During feeding during startup, control the system pressure to prevent pulse feeding. d. During the startup heating phase, the heating rate must be controlled properly. (3) During shutdown, the steam supply must be cut off before the furnace inlet temperature drops to 450°C. (4) Carry out the reduction of the catalyst to enhance its activity. (5) Try not to work at high speeds. (6) Improve the quality of catalyst loading. (7) Strictly control the feed to prevent large-molecule hydrocarbons from entering the converter, and thoroughly remove harmful substances from the raw materials. (8) An appropriate hydrogen supply and carbon-to-water ratio at the furnace front is an important way to protect the catalyst. 10. What are carbon buildup and carbon removal? Answer: Carbon deposition: In the steam reforming of hydrocarbon feedstocks, C-C bond cleavage occurs first, accompanied by further dehydrogenation and hydrogenation; as a result, hydrocarbons with lower carbon numbers and hydrogen are produced, along with carbon, and this is what constitutes carbon deposition. Char gasification: The reaction between charcoal and water vapor produces CO and H2; this is known as char gasification. 11. How to detect carbon buildup? Answer: (1) The furnace tubes commonly exhibit mottling or red discoloration. (2) The pressure drop across the furnace tubes increases. (3) The methane content at the converter outlet increased, and no other hydrocarbons were detected. 12. What are the hazards caused by insufficient reduction of the conversion catalyst or its oxidation during use, and how can they be prevented? Answer: Hazards: a. Catalyst carbon deposition leads to mottling and red tubes in the furnace tubes. In severe cases, it blocks the furnace tubes, causing a white tube phenomenon that affects their lifespan. b. The catalyst conversion rate decreases, and the hydrogen production volume drops. Prevention: a. Conduct proper catalyst reduction at the start of operation to ensure the catalyst is fully reduced. b. An appropriate hydrogen and carbon-to-water ratio at the furnace front is an important way to protect catalyst activity. 13. How to improve conversion rates? Answer: a. Reduce operating pressure b. Increase reaction temperature c. Increase water-to-carbon ratio d. Reduce space velocity e. Increase furnace inlet temperature. 14. What are the precautions for catalyst reduction? Answer: a. During reduction, the inlet temperature of the catalyst bed and the outlet temperature of the furnace should be increased as much as possible to facilitate thorough reduction of the catalyst. The inlet temperature of the converter is maintained at 490–520°C, the outlet temperature is 800°C, and the system pressure is controlled at 0.8–1.0 Mpa. b. To accelerate the reduction process, the system circulation rate can be increased to raise the hydrogen content, with the H2O/H2 ratio controlled between 3 and 7.5. c. The reduction time starts to be counted at 8–12 hours once the furnace outlet temperature reaches 800°C and the H2 content in the circulating gas exceeds 70%. d. When the system pressure drops, liquid ammonia must be replenished. 15. What are the conditions for starting steam supply? Answer: a. The steam quality is satisfactory, the pressure is 0.3–0.5 Mpa higher than that at the inlet of the converter, and the drain water has been removed before the steam supply valve. b. The system pressure should be maintained at 0.8–1.0 Mpa. c. The pressure has been raised in advance for liquid ammonia filling. d. The inlet temperature of the converter is 420–450°C, the outlet temperature is >450°C, and the lowest temperature in the bed of the medium conversion reactor is >200°C. 16. Causes of high methane content at the converter outlet and solutions? Answer: Reasons: ① Low furnace temperature; ② Sudden increase in space velocity; ③ Decreased activity due to catalyst poisoning; ④ Changes in the feedstock, i.e., an increase in high-carbon alkanes; ⑤ Sudden malfunction of the control system, resulting in an excessively low H2O/C ratio, etc. Treatment: ① Adjust the furnace temperature to stabilize the processing capacity. ② Check the desulfurization section of the raw materials to ensure effective desulfurization. ③ Reduce or cut off the feed, and use steam for carbon and sulfur removal. ④ Increase the water-to-carbon ratio, and strictly control the H2O/C ratio. 17. What are the safety accessories of a boiler? Answer: Pressure gauges, level gauges, safety valves, rupture disks, steam-water valves, drain valves. 18. Write the formula for calculating the methane conversion rate? Answer: Conversion rate X =──────── CO% + CO2% / (CO% + CO2% + CH4%) 19. What is the working principle of a flame arrester? Answer: Most flame arresters are composed of multiple layers of metal mesh. When a flame enters the flame arrester, the rapid heat transfer through the metal mesh causes the flame to be dispersed and cooled, thereby being extinguished, which achieves the purpose of preventing the spread of flames. 20. What are the reasons for excessive temperature rise in fan bearings? Answer: a. Severe vibration of the bearing housing. b. The quality of the lubricating oil is poor and it has deteriorated. c. The lubricating oil level is too low, or too high. d. The shaft is not aligned with the rolling bearing. e. Damage to the rolling bearings. 21. What are the key points for the normal operation of a converter? Answer: (1) The feed rate and feed temperature should be stable ； ⑵Control the furnace temperature well and maintain a constant outlet temperature ； ⑶The excess air coefficient a should be appropriate ； ⑷The main focus is on observing the flame in the furnace ； ⑸Control the exhaust temperature properly ； ⑹Pay attention to changes in the furnace tube pressure drop. 22. What are the various maintenance methods for shut-down boilers? Answer: (1) Wet curing method ； ⑵Nitrogen padding method ； ⑶Dry curing method. 23. What are the conditions for an emergency shutdown of the furnace? Answer: (1) The boiler is severely short of water; even after treatment, the liquid level in the drum still drops to the lower limit ； ⑵When the boiler water level drops rapidly, and despite continuous water supply and other measures, the level still fails to rise ； ⑶When the boiler feedwater valve fails or there is a serious malfunction in the feedwater system that cannot be repaired in a short time ； ⑷Safety accessories such as level gauges, safety valves, pressure gauges, etc., when one of them fails completely ； ⑸When the pressure-bearing components of the boiler leak or are severely damaged. 24. What are the factors that affect the temperature of medium-temperature shift? Answer: (1) Impact of converter operation ； ⑵Impact of catalyst coking ； ⑶Catalyst activity ； ⑷Internal leakage in heat exchanger ； ⑸Instrument failure. 25. How to protect the converter tubes during operation? Answer: (1) Avoid overheating inside the furnace tube ； ⑵Prevent the furnace tubes from bursting due to sudden cooling and heating, uneven expansion, thermal fatigue, water in the steam, and condensation ； ⑶Ensure steam quality to prevent salt buildup in the furnace tubes, which could lead to dead air and dry burning ； ⑷Strengthen the inspection of various parts of the converter tubes. 26. What are the main methods for controlling the temperature of a converter? Answer ； ⑴Reduce the temperature of the entire furnace chamber ； ⑵Adjust the frequency of the exhaust fan or the opening degree of the flue dampers ； ⑶Adjust the blower frequency conversion ； ⑷Adjust the opening degree of the converter nozzle valve ； ⑸The quality of combustion in the burner can be adjusted by changing the opening degree of the primary and secondary air valves ； ⑹After checking the furnace’s combustion status each time, make sure to close the viewing window to prevent air from entering and reduce the furnace’s efficiency. 27. How is the reducing agent reduced? Answer: (1) Establish a variable N circulation during conversion, with a system pressure of 1.0 MPa and a controlled circulation rate of 4000 Nm/h. ⑵Select an appropriate time to introduce the medium-pressure reactor based on the shutdown conditions. ⑶The inlet temperature of the converter is 450°C, and the outlet temperature is 750°C; the lowest temperature in the medium-pressure conversion bed is above 200°C. The pressure in the steam drum is 2.0 MPa. Once the steam and water samples show satisfactory results and the drainage process is completed, 5–6 t/h of steam is added, along with liquid ammonia for reduction purposes ； ⑷Sampling is taken every half hour to analyze the purity of H in the circulating gas; reduction begins once the purity exceeds 70%, and this reduction process lasts for 8–12 hours, during which ammonia is added as needed based on the results of the sampling analyses. 28. What are the usage conditions for the converter? Answer: Z417: Location: Installed in the upper part of the conversion furnace ； Operating temperature: inlet temperature for conversion 450–650°C, water-to-carbon ratio: 3.5–5.3 ； Air velocity: 500–1000 h Z418: Location: lower part of the converter ； Operating temperature: 600～950℃, ； Water-to-carbon ratio: 3.5～5.3 ； Airspeed: 500–1000 h. 29. How to protect the converter during production? Answer: (1) Try not to operate at high speeds ； ⑵Strictly control the raw materials to prevent large-molecule hydrocarbons from entering the converter ； ⑶Ensure that the catalyst in the conversion inlet section is in a reduced state ； ⑷Strictly remove toxic substances from the feed hydrocarbon ； ⑸Ensure a sufficient water-to-carbon ratio at all times during operation, and avoid large fluctuations in this ratio ； ⑹Strictly control the temperature in the converter furnace to avoid large fluctuations ； ⑺Improve the quality of superheated steam to prevent catalyst salt formation ； ⑻Ensure that the inlet temperature for conversion is not lower than 480℃ ； ⑼If mild carbon buildup or poisoning is detected, it should be addressed as soon as possible ； ⑽Ensure the reduced quality and activity of the catalyst, and avoid frequent start-up and shutdowns. 30. What are the main operating conditions for medium-temperature catalysts? Answer: Operating pressure: 0.5-8.0 MPa ； Reaction temperature: 340-460℃ ； Airspeed: 1000-3000h ； The temperature rise during reduction shall not exceed 30℃ ； During reduction, the water-to-hydrogen ratio is controlled between 3 and 7.5. 31. What are the main methods for controlling the temperature of the converter? Answer: (1) Reduce the temperature of the entire furnace ； ⑵Adjust the frequency of the exhaust fan or the opening degree of the flue dampers ； ⑶Adjust the blower frequency conversion ； ⑷Adjust the opening degree of the converter nozzle valve ； ⑸The quality of combustion in the burner can be adjusted by changing the opening degree of the primary and secondary air valves ； ⑹After checking the furnace’s combustion status each time, make sure to close the viewing window to prevent air from entering and reduce the furnace’s efficiency. 32. What are the phenomena, causes, and solutions for overheating in medium-pressure reactors? Answer: Phenomenon: (1) The inlet temperature of the medium-pressure reactor is extremely high ； ⑵The bed temperature and outlet temperature of the medium-pressure reactor are excessively high ； ⑶The steam drum has a low evaporation rate. Reason: (1) Faulty temperature control valve at the reactor inlet ； ⑵The high content of CO in the converted exhaust leads to intense medium-temperature reactions and overheating ； Action: (1) Immediately reduce the temperature at the reactor inlet; if the inlet temperature control valve fails, switch to manual operation on site and contact the instrumentation team to repair the control valve ； ⑵If the inlet temperature cannot be reduced, the production load should be lowered immediately, and high-pressure nitrogen should be blown at the inlet to cool it down; normal production can be resumed once the temperature is back within the normal range ； ⑶If the temperature of the reactor rises significantly, it will damage the catalyst, prompting an emergency shutdown of the plant ； ⑷If the spool of the inlet temperature control valve is damaged, operations must be halted for repair as there is no bypass line available ； ⑸If it is caused by an excessively high CO content at the conversion outlet or an excessive production load, the only solution is to lower the temperature at the conversion outlet or the production load. 33. What are the normal shutdown procedures and precautions for conversion positions? Answer: (1) After the hydrogenation and hot hydrogen with oil processing are completed, hydrogen production will be reduced to its minimum level; the steam supply amount will be 5–6 t/h. The PSA unit and the desorption gas system will be shut off, while the volume of gas supplied will be adjusted to maintain the furnace temperature for normal operation. ⑵A variable cycle during slow conversion establishment is adopted; once stability is achieved, the conversion feed is stopped. A separate cycle for desulfurization is established to ensure a conversion pressure that is 0.3–0.5 MPa lower. Note: Adjust the torch control pressure at medium pressure to prevent pulsating feeding. ⑶After 1 hour, when the CH content in the medium-temperature gas during analysis is less than 0.5%, cooling begins for the conversion furnace in the medium-temperature reactor; the steam supply rate is set at 5 t/h, the cooling rate shall not exceed 50°C/h, the pressure is reduced gradually, and the circulation volume is carefully controlled. ⑷When the conversion inlet temperature reaches 380°C, the steam supply is cut off and nitrogen is introduced at the compressor inlet; when the furnace temperature drops to 250°C, the fire is extinguished and the cooling process continues in a cyclic manner. ⑸The desulfurization system stops operating for a period of time, remains in a heated state, and uses a flare to maintain a pressure difference with the conversion system. ⑹It is determined whether to stop the cycle and pressure reducer based on the duration of the shutdown; after cutting off the steam supply, the pressure in the drum is reduced gradually. If the conditions are not met, the 1.0 MPa system is disconnected, and as appropriate, the boiler feed pump, the bottom pump of the stripping tower, the air coolers, and the fans are stopped. 34. How to determine whether it is converter poisoning or carbon buildup? Answer: Poisoning: Catalyst poisoning usually starts with red tubes appearing in the upper part of the converter and then spreading to tubes of all diameters; it is a widespread phenomenon, not limited to individual reactor tubes ； A decrease in catalyst activity leads to an increase in methane content at the outlet; in severe cases, aromatics can penetrate through the bed layer and even cause carbon deposition. This results in an increase in furnace temperature and an increase in the pressure difference at the furnace outlet. Carbon deposition: Catalyst carbon deposition only results in mottled patterns, red tubes, and hot spots in some of the furnace tubes; it is not a widespread phenomenon ； The methane and aromatic content at the furnace outlet increased, and their proportions rose significantly; the pressure difference between the inlet and outlet of the conversion unit also increased markedly. 35. What are the causes of hot spots, hot zones, and hot tubes in furnace tubes? Answer: Reasons: (1) Poor quality of catalyst filling, with gaps and bridges, as well as uneven distribution across the furnace tubes leading to carbon deposition ； ⑵During operation, the catalyst may get crushed, or it may fall from a great height during loading, resulting in blockages of the furnace tubes; this leads to dry burning and discoloration of the tubes to a red color ； ⑶Carbon deposition on the catalyst during long-term operation or as a result of accidents, as well as hydrolysis ； ⑷Inadequate reduction by the reducing agent leads to more thermal cracking of hydrocarbons on its surface, while carbon elimination occurs to a lesser extent; this results in catalyst carbon deposition ； ⑸Improper adjustment of the converter burner leads to uneven burning or tube blockage, resulting in localized overheating and carbon deposition; this causes ⑹ a decline in the performance of some catalysts, bringing them to the end of their useful life. 36. What are the causes and symptoms of converter shutdown? Answer: Reason: (1) The fuel self-protection valve failed to open ； ⑵The unit shuts down due to interlock; the fuel safety valve closes ； ⑶The system stops supplying purge air and instrument power, causing the fuel control valve to close ； ⑷Fuel interruption or PSA failure causes an interruption in the desorbed gas flow ； ⑸The flame arrester is severely clogged, preventing fuel from passing through. ⑹Changes in the fuel composition cause a sharp increase in negative pressure in the furnace, resulting in the flame going out instantly. Phenomenon: (1) The furnace temperature drops rapidly, and the temperatures at the inlet and outlet of the furnace decrease ； ⑵The combustion noise in the converter disappears; the negative pressure inside the furnace increases, the furnace becomes darker, and the flame is no longer visible ； ⑶The fuel flow rate into the furnace is 0. 37. What are the regeneration steps after catalyst poisoning? Answer: (1) When the conversion catalyst is slightly poisoned: the production load can be reduced, and clean feedstock can be used to operate under a high water-to-carbon ratio for a period of time. If the temperature at the upper part of the furnace tubes drops, the red color in those tubes disappears, and the methane content at the conversion outlet gradually decreases, this indicates that the measure is effective. If the effect is not satisfactory, the feed material can be cut off and the system can be operated in a reducing atmosphere for a period of time to achieve regeneration. ⑵ In cases of severe poisoning of the converter: ① Cut off the feed, establish a nitrogen circulation within the conversion system; the pressure in the conversion system should be maintained at 0.5–1.0 MPa, while the steam supply should remain at the normal level of 20%-30%. The bed temperature should be kept slightly lower than the normal operating temperature, and the system should be operated for 8 hours. ② Add hydrogen at the inlet of the compressor to raise the water-to-hydrogen ratio to around 3, and maintain this condition for 4 hours. Samples should be taken for analysis; if the H2S level in the circulating gas is high, more hydrogen should be added to displace it. ③When the H2S content in the converted product is less than 0.2 ppm, hydrogen supply is stopped; then nitrogen is introduced to thoroughly displace it, and the carbon deposits accumulated in the catalyst’s micropores are burned away in an oxidizing atmosphere ； ④After analyzing that the CO contents at the inlet and outlet of the conversion unit are equal, hydrogen is added at the inlet of the compressor to raise the water-to-hydrogen ratio to around 3, followed by another sulfur release process. The sulfur content at the outlet of the conversion unit is analyzed promptly; if it is high, hydrogen is used for displacement. Once the H2S content at the outlet of the conversion unit falls below 0.1 ppm, the system is operated under these conditions for 4 hours, after which the sulfur release process is completed ； ⑤Reduce the catalyst for 8-12 hours according to the normal startup procedure. 38. What are the normal steps to start working at a converted position and what are the precautions? Answer: (1) Establish a cycle of varying N during conversion, ignite and raise the temperature; the rate of temperature increase should not exceed 50°C/h, with the system pressure maintained at around 1.0 MPa ； ⑵Select an appropriate time to introduce the medium-pressure reactor based on the shutdown conditions. If the bed temperature rises above 300°C during a short shutdown, it is incorporated when the conversion reaches 320%; in the case of a long shutdown, the temperature is increased along with the conversion rate. Note: When merging, do it slowly to avoid causing large fluctuations. ⑶When the inlet temperature of the converter is 450°C, the outlet temperature is 750°C, the lowest temperature in the medium-conversion bed is above 200°C, the pressure in the steam drum is 2.0 MPa, the steam and water samples show satisfactory analysis results and the drainage process is completed, 5–6 t/h of steam is added along with liquid ammonia for reduction purposes. Timing begins when the purity is greater than 70%; the reduction process lasts for 8–12 hours, during which the pressure in the steam drum is gradually increased to 3.0 MPa. Note: During the reduction process, maintain a circulation rate of 4000 Nm∙h to ensure an appropriate hydrogen-to-air ratio as well as a proper water-to-hydrogen ratio ； ⑷After the reduction is complete, and once the sampled desulfurized gas meets the required analysis standards, the desulfurization pressure is increased gradually. When this pressure exceeds the conversion pressure, the conversion feed control valve as well as the upstream and downstream valves are opened. The circulation pump is stopped based on the required pressure and temperature at its inlet, and the pressure is controlled by using a flare system; once stability is achieved, the system pressure is slowly increased to the normal operating level. Note: Adjust the pressure by changing the torch setting, maintain a stable water-to-carbon ratio, avoid pulsating feed, and be careful not to let the water-to-carbon ratio become too low during pressure increase ； ⑸Drive to the PSA control valve and the upstream and downstream valves, then to the PSA ； Note: Sample analysis should be conducted before combining to check for changes in gas composition ； ⑹After the PSA returns to normal, introduce desorption gas into the furnace, activate the purified water system, stabilize the liquid levels in the steam drum and various water separation tanks, and adjust all parameters to their normal operating values. 39. Reduction conditions for the converter? ⑴The circulation compressor is operating normally, and a nitrogen circulation system for the conversion process has been established; the system pressure is around 1.0 MPa ； ⑵The intermediate transformer has been integrated into the system, and the lowest bed temperature of the intermediate transformer is more than 20°C above the steam dew point corrosion level ； ⑶Conversion inlet temperature: 450°C, outlet: 750°C℃ ； ⑷The drum liquid level is normal, the drum pressure is 2.0 MPa, and the analyses of the drum water and steam water are satisfactory ； ⑸The liquid ammonia has been replenished, and the pressure in the liquid ammonia tank is 0.3–0.5 MPa higher than the system pressure; ⑹ Drainage before the steam distribution valve has been completed ； 40. What are the factors affecting hydrogen yield? Answer: (1) The properties of the raw material; that is, the higher the H/C ratio, the higher the hydrogen yield ； ⑵, Changes in PSA operating parameters ； The larger the parameter, the higher the yield ； ⑶, the set value of the adsorption pressure changes ； ⑷, Analyze the changes in the set value of pressure ； ⑸Changes in the requirements regarding product purity: the higher the purity, the lower the yield ； ⑹, calculate or analyze errors ； ⑺Changes in the activity of converters and medium-transformers ； ⑻Leakage conditions of the process pipelines. 41. What are the requirements for the feedstock for conversion? Answer: Sulfur content