Transformation Catalyst User Manual
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Transformation Catalyst User Manual
Instruction Manual for SB303Q Spherical Cobalt-Molybdenum Sulfur-Resistant Shift Catalyst 1. Introduction SB303Q is a spherical sulfur-resistant shift catalyst that was invented and developed by Professor Chen Jinsong, a leading expert in shift catalysts in China. Its performance exceeds the requirements of the HG 2779-1996** chemical industry standard, and it has obtained ISO9001:2000 international quality system certification. Quality is the lifeblood of a company; for each batch of catalyst products leaving our factory, Professor Chen Jinsong personally oversees the quality control. This catalyst features good low-temperature activity, a wide operating temperature range, excellent oxidation resistance, and a high conversion rate of organic sulfur, reaching international advanced levels; it adopts a one-time impregnation production process, resulting in less pollution and lower energy consumption. They can be used in large, medium, and small ammonia synthesis plants that use coal and oil as raw materials; they can be employed after medium-pressure conversion in the copper-cleaning process, or they can replace Fe-Cr series medium-pressure conversion catalysts in fully low-pressure conversion processes; they can also replace Cu-Zn catalysts in three-catalyst processes. Applied in the medium-pressure to low-pressure shift process, it can increase the CO content after medium-pressure shift to 4–6%, significantly reduce steam consumption, and lower the CO content in the shift gas at the system outlet to 0.5–1.5%, thereby reducing the load on the copper washing unit. The effective air compression capacity of the high-pressure compressor increases, allowing fertilizer production to rise by 2–3%, resulting in significant economic benefits. Applied to the fully low-temperature shift process, it nearly doubles the conversion capacity, further reduces steam consumption, shortens the process, and yields significant benefits; it represents a major advancement in shift technology. It is used in the three-catalyst process, allowing the elimination of the secondary desulfurization step and preventing the \"hot-cold problem\" in the gases; it plays a significant role in further reducing energy consumption in medium-sized plants. The all-low conversion process is a completely new conversion process developed on the basis of the medium-string low process ； Based on the SB303Q catalyst, it reduces the peak temperature in the conventional medium-temperature shift system by over 100°C, which **favors the equilibrium of the CO conversion reaction. The actual consumption of ammonia vapor per ton is only around 250 kg; as a result, the heat exchange and heat recovery equipment required will be reduced. In other words, if a synthetic ammonia plant with a capacity of 25,000 t/year is upgraded to one with a capacity of 50,000 t/year, the shift equipment basically does not need to be replaced. This process has been successfully applied industrially in nearly a hundred small nitrogen fertilizer plants across 18 provinces nationwide. Compared with the traditional medium-shift process, it offers the following advantages: the amount of medium-shift catalyst required is reduced by more than half, which lowers the bed resistance and increases the capacity of the shift converter; the bed temperature drops by 100–200°C, and the gas volume decreases by 25%, thereby reducing system resistance and compressor power consumption; compared with the medium-shift combined with low-shift process, the full low-shift process results in less effective energy loss, thus improving heat recovery efficiency and further reducing steam consumption. It also eliminates the reaction that produces acetylene, reduces copper melt usage, and prevents the occurrence of \"liquid carryover\"; the heat exchange area is reduced by about half; the problem of catalyst pulverization associated with the medium-shift process is fundamentally solved, improving the working conditions related to catalyst handling; the conversion efficiency of organic sulfur is enhanced – the conversion rate is 90–95% for the medium-shift or medium-shift combined with low-shift process, while it exceeds 98% for the full low-shift process, with the organic sulfur content at the outlet being around 1 mg/NM3; the operation is simple, startup is fast, and the available operating time is increased; the requirements for the materials used in shift converters are reduced, improving the conditions for equipment maintenance. The catalyst has a long lifespan; it can generally be used for about 5 years, with the longest recorded usage period being 6 years. The desulfurization target was relaxed, thereby reducing the desulfurization costs. Under normal operating conditions, the service life of the SB303Q catalyst can reach around 5 years. For a synthetic ammonia plant with an annual production capacity of 15,000 tons, the annual economic benefits associated with the medium-pressure shift-to-low-pressure shift and full low-pressure shift processes are approximately 300,000 and 500,000 yuan respectively; the energy consumption per ton of ammonia can be reduced by around 800,000 kcal in each case. 2. Main features include excellent low-temperature activity. It has a spherical shape, low air resistance, and high strength. Does not turn powdery when exposed to water. High sulfur resistance; there is no upper limit to sulfur resistance. It has good organic sulfur conversion performance and antioxidant properties. Easy to vulcanize. 3. Quality standards: Compressive resistance under point pressure: ≥35 N per particle; the strength can increase by 30–50% after vulcanization. CO conversion rate: ≥90%. Test conditions: Pressure of 0.8 MPa, initial particle size of Φ4–5 mm, sample volume of 30 ml; the feed gas is semi-water gas, with a dry gas space velocity of 2500 h-1, a vapor/gas ratio of 0.5, and a temperature of 200°C. The bulk density is 0.72±0.02 g/ml. 4. Use of space velocity (semi-water gas): 4.1. Medium-to-low conversion: At normal pressure <700, the space velocity is <1 h-1; in systems at 0.8 MPa, the outlet CO level is around 1%; when the space velocity is <1400 h-1, the outlet CO level is <0.3%; and when the space velocity is <650 h-1, the outlet CO level is also <0.3%. In systems at 1.35 MPa, the outlet CO level is around 1%; when the space velocity is <1800 h-1, the outlet CO level is <0.3%; and when the space velocity is <800 h-1, it remains <0.3%. In systems at 2.0 MPa, the space velocity should be <2000 h-1. 4.2. Full low conversion: Most plants that use the full low-conversion process have modified their existing medium-to-low conversion processes; the specific process to be used depends on the conditions of each plant. Our company provides technical support, sends personnel to assist with the commissioning of the systems, offers on-site services, and teaches the necessary operating techniques. Main process parameters: (0.8 MPa system) Exit CO: ~1%; total space velocity: 800–1000 h-1, exit CO < 0.3%; total space velocity: 500 h-1, exit CO: ~4–6%; total space velocity: 1600 h-1. 1.35 MPa system: Exit CO: ~1%; total space velocity: 800–1200 h-1, exit CO < 0.3%; total space velocity: 600 h-1, exit CO: ~4–6%; total space velocity: 2000 h-1. 5. Preparations before startup: To ensure a smooth startup, please come to our company during the ordering process to discuss the catalyst application process, and submit the process flow diagram to our company for verification. Before startup, the process flow must be checked. To ensure satisfactory sulfidation results, the following is necessary: 5.1. Electric furnace configuration: An electric furnace should be provided separately for heating up during startup and for start-up/stop operations during production in the low-temperature transformation system. Prepare at 30–50 kW per M3 of catalyst; use CS2 sulfidation to set the lower limit, while sulfidation with dry shift gas, solid sulfiding agents, or high-sulfur gas should be used to set the upper limit. Steam from a water heater can also be used to preheat the dry gas in order to compensate for the insufficient power of the electric furnace; in this case, the dry gas inlet pipe should be connected in front of the water heater. 5.2. Placement of temperature measurement points: One temperature measurement point is installed at each inlet and outlet of the electric furnace and the low-temperature transformation furnace; temperature measurement points are placed 150 mm below the upper surface of the low-temperature transformation bed layer, as well as 150 mm above its lower surface; temperature measurement points are arranged evenly in the middle part of the bed layer according to actual conditions. 5.3. Gas for sulfidation, vent lines: Gas for sulfidation should be dry semi-water gas or dry shift gas. Dry gas can be obtained from the outlet of the Roots pump or from the first and second outlets of the high-pressure compressor, after passing through an oil separator and a coke filter. Dry shift gas should be taken from the outlet of the shift system (at a temperature of less than 35°C). The inlet and vent pipelines should be designed to handle a gas flow rate corresponding to a maximum sulfidation velocity of 500 h-1; for small ammonia plants, a diameter of φ159 is appropriate. . 5.4. Catalyst Loading: To prevent gas flow from being uneven, distributors must be installed at the gas inlet and outlet. For the design of these gas distributors, reference can be made to the equipment diagrams of standard shift converters; the distributor (tube) is located at the radial center of the shift converter, with an upward bend at the inlet and a downward bend at the outlet. The catalyst particles are small in size (φ4–6 mm); a double layer of wire mesh with a mesh size of 8–10 is used as a base, and the surrounding area must be sealed tightly, using red bricks or refractory bricks – it is best to seal it with cement as well, to prevent the catalyst from leaking out. To prevent the catalyst from being blown over, a layer of perforated steel plate must be placed on top of each layer of ribbed plates. The catalyst should be loaded before low-temperature vulcanization; otherwise, leakage in the inlet and outlet valves can allow condensate to enter the catalyst bed, leading to the loss of active components or causing the catalyst to stick together and form clumps, thereby affecting its activity. 6. Heating for vulcanization and vulcanization procedures 6.1. Vulcanization mechanism The main active components of the SB303Q catalyst, namely cobalt oxide and molybdenum trioxide, need to be converted into sulfides before they can be active; this process is known as vulcanization. The main reactions involved are: MoO3 + 2H2S + H2 = MoS2 + 3H2O, with ΔH0 = -48.1 KJ/mol; CoO + H2S = CoS + H2O, with ΔH0 = -13.6 KJ/mol. To ensure an adequate concentration of H2S in the gas and thus facilitate the vulcanization process, CS2 is typically added continuously to the system. Hydrogenolysis then occurs at a certain temperature (around 200°C) to produce H2S: CS2 + 4H2 = 2H2S + CH4, with ΔH0 = -240 KJ/mol. 6.2. Vulcanization methods The quality of vulcanization is crucial for the performance of the catalyst, and this process is usually carried out based on experience. It is generally recommended that professionals handle the vulcanization process, as attempting to do it oneself often does not yield the desired results. To ensure successful catalyst vulcanization, our company offers high-quality start-up services; manufacturers can contact us one week before starting up the system. 6.2.1. Carbon disulfide sulfidation: Carbon disulfide should be prepared at a rate of 150 kilograms per M3 of catalyst; it is necessary to check whether there is sufficient amount of carbon disulfide before use. The carbon disulfide tank must be thoroughly cleaned; the introduction of oil contamination is strictly prohibited. The tank should be able to withstand a pressure of 0.5 MPa, with an operating pressure of 0.1–0.2 MPa. It should be equipped with a pressure gauge, a vent pipe, a nitrogen inlet (Dg20), a carbon disulfide outlet pipe (Dg20), an inlet pipe (Dg50), and a glass tube level gauge. The capacity of the tank should be such that it can hold enough carbon disulfide to be used in one batch. The pipeline for transporting carbon disulfide should be made of steel, pressure-resistant oxygen hoses, or plastic tubing; the inlet pipe should be connected to the pipeline after the temperature measurement point at the exit of the electric furnace. Carbon disulfide is added to the tank, and the pressure is raised to 0.1–0.2 MPa using N2 (under reduced pressure) for later use. After the converter is purged with inert gas, dry semi-water gas (or dry conversion gas) is introduced at atmospheric pressure to raise the temperature. When the temperature at the upper part of the bed rises to 200°C, carbon disulfide can be added to the system; the gas exiting the low-temperature shift reactor can be vented or recycled after cooling. If the carbon disulfide concentration is too low during vulcanization, it will prolong the vulcanization time; if it is too high, the bed temperature will rise sharply. A concentration of 20–70 g/NM3 is appropriate. During sulfidation, care must be taken to prevent a sudden rise in temperature that could burn out the catalyst; the oxygen content in semi-water gas must be strictly controlled to less than 0.5%. The control of the bed temperature is primarily achieved by adjusting the gas flow and the electric furnace, with appropriate changes to the amount of carbon disulfide added. 6.3. Sulfidation process: There are two methods, namely one-pass method and cyclic sulfidation method. During cyclic sulfidation, it is necessary to regularly remove the condensed water from the incoming gas and vent a small amount of circulating gas to keep the H2 content in the circulating gas above 25%. The following sulfidation plans are provided for reference:
**Stage**, **Execution Time (hr)**, **Space Velocity (h-1)**, **Temperature at Various Points in the Bed (°C)**, **H2S Content entering the Furnace (g/Nm3)**, **Notes**
1. **Heating Up**: 6–8, 200–300, 70–210. First, use gas to purge the system and then use an electric furnace to raise the temperature.
2. **Sulfidation Period**: 10–15, 100–200, 210–300, 10–20. Wait until the H2S content in the exhaust gas is ≥3 g/Nm3 and the bed is penetrated.
3. **Intensification Period**: 4, 5, 100–200, 300–350, 350–450, 10–20. The H2S content at the exit of the converter should be ≥10 g/Nm3.
4. **Cooling and Purging**: ~6, 200–300, 180–20. The H2S content in the exhaust gas should be ≤1 g/Nm3, after which it can be used in production. Analyze the H2S concentration at the exit of the converter once per hour; if it exceeds 3 g/NM3, analyze it every half hour. After low-temperature vulcanization is complete, if it is necessary to remove the blind flanges in the system, it is strictly prohibited to remove both the inlet and outlet blind flanges at the same time, to prevent air from entering and damaging the catalyst. If it is not possible to do so in a timely and systematic manner, dry gas should be used to maintain positive pressure inside the furnace, thereby preventing negative pressure from allowing air to enter. 6.4. Handling of abnormal situations during the sulfidation process: Slow heating of the bed layer: Too low or too high flow rate of semi-water gas, or insufficient capacity of the electric furnace. Bed temperature rises sharply: excessive O2 content in semi-water gas; too rapid addition of CS2; excessive power usage by the electric furnace. Upon detecting a sharp rise in temperature, the cause is identified and preventive adjustments are made to avoid burning out the catalyst. 7. Normal operating conditions and precautions 7.1. Process parameters 7.1.1. For the medium-pressure shift to low-pressure shift system: steam-to-gas ratio: ~0.5; inlet temperature of the low-pressure shift unit: 170–210°C; CO content at the inlet of the low-pressure shift unit: 4–6%; CO content at the outlet: ≤1.5%; maximum bed temperature: ~250°C. H2S content in the gas from the medium-pressure shift unit: ~80 mg/NM3. The catalyst used in the low-pressure shift unit should be operated at low temperatures as much as possible, but the inlet temperature must be at least 30°C above the dew point. 7.1.2. Full low-pressure conversion: This depends on the processes used in various plants (copper washing, hydroformylation, methanation), and is generally as follows: Inlet temperature for the first stage: 200–230°C; inlet temperature for the second stage (low-pressure conversion section): ~180°C; CO content at the outlet of the first stage: 2–6%. Second-stage outlet CO: ≤1.5%. Transformed gas H2S content (total sulfur): ≥100mg/NM3. 7.2. Preventing catalyst resulfidation – Resulfidation is one of the causes of catalyst deactivation. Anti-sulfidation intensifies as temperature and gas-to-vapor ratio increase, as well as as H2S concentration decreases. Therefore, to maintain stable operating conditions, it is essential to keep the catalyst bed temperature and the gas-to-vapor ratio as low as possible, and an appropriate H2S level should be maintained (H2S level > 50 mg/NM3); this is a prerequisite for preserving the catalyst’s activity and lifespan. 7.3. Control of steam-to-gas ratio: When operating in the medium-pressure shift with low-pressure shift mode, the steam-to-gas ratio at the inlet of the converter should not be set too low (it should not be less than 0.40); otherwise, the Fischer-Tropsch reaction may occur, resulting in the formation of ethylene, acetylene, etc. This can lead to the formation of cuprous acetylide precipitates in the copper melt and cause issues with the copper washing liquid. Secondly, an excessively low gas-to-vapor ratio causes large fluctuations in the CO content at the conversion outlet, affecting normal production. 8. Parking 8.1. Temporary parking: Close the inlet and outlet valves of the low-pressure transformation system, as well as the drain and sampling valves, to maintain insulation and pressure. If the bed temperature drops, the system pressure should also be reduced to ensure that the bed temperature remains 30°C above the dew point; when the temperature falls below 120°C, the pressure must be reduced to atmospheric level, after which positive pressure is maintained using gas, shift gas, or refined gas stored in cylinders, to prevent air from entering. 8.2. Emergency shutdown: Similar to temporary shutdown, close the system’s inlet and outlet valves, as well as the drain and sampling valves, in order to maintain pressure and temperature; pay attention to the liquid level in the hot water tower to prevent it from rising too high and flowing into the low-temperature converter. 8.3. Long-term shutdown: Before shutting down the entire system, relieve pressure and use dry gas to cool the catalyst bed to a temperature below 40°C. Close the inlet and outlet valves of the low-temperature shift reactor as well as all pressure measurement and analysis sampling points, and install blind flanges. Maintain a slight positive pressure (approximately 30 mm of water column) using gas, shift gas, or refined gas stored in cylinders (such as nitrogen, with an O2 content of <0.1%); air must not enter the furnace under any circumstances. When it is necessary to inspect the catalyst bed, it must first be purged with N2 (O2 < 0.1%), and only then can the manhole be opened, in order to prevent gas convection from allowing air to enter the catalyst (i.e., the chimney effect). The temperature of the low-temperature converter can be reduced to 120–150°C by using steam for displacement. 9. When driving the process, whenever the temperature at any point in the bed is below the dew point temperature (0.75 MPa–120°C, 1.35 MPa–140°C), it is necessary to raise the temperature back above the dew point using dry gas before the gas can be fed into the medium-pressure conversion process. Otherwise, the vapor of intermediate-temperature gas will condense into water, causing the loss of potassium in the catalyst and thereby affecting its activity. In the early stages of operation, the system pressure is low and the gas-to-steam ratio is difficult to control properly, which can lead to catalyst resulfidation; at such times, the outlet CO content should be increased appropriately in order to maintain a lower gas-to-steam ratio. In the early stages of driving, the circulating water temperature is low; using a water heater to adjust the temperature may result in a too low inlet temperature for the water, leading to water contamination. Therefore, it is necessary to activate the gas bypass of the water heater in order to regulate the gas inlet temperature. 10. Catalyst removal and resulfurization: The low-temperature converter is cooled to below 20°C using dry gas, and the catalyst is removed through a discharge hole and placed in plastic bags or iron drums for storage. It can be reused without undergoing sulfurization and can operate directly in combination with gas. The re-vulcanization scheme is the same as the original vulcanization scheme; both the temperature and the vulcanization time at each temperature must meet the specified requirements. The amount of CS2 used can be half of that used during the initial vulcanization; during re-vulcanization, H2S penetrates quickly, but the overall vulcanization time cannot be reduced. The decline in activity caused by factors such as anti-sulfidation can be restored through resulfidation. 11. Catalyst maintenance during normal operation: Internal leakage in the heat exchanger is a major cause of abnormal catalyst deactivation; oxygen present in semi-water gas, along with oil and other impurities, can penetrate into the low-temperature converter and lead to permanent catalyst deactivation. Attention should be paid to the relationship between temperature rise and the CO content at the inlet and outlet; generally, a 1% reduction in CO results in a temperature rise of around 9°C. The temperature rise exceeds the corresponding value; internal heat leakage must be taken into account, as even a small amount of such leakage can cause serious damage to the catalyst. In the event of a sudden reduction in production volume, the steam supply should be immediately reduced or cut off. Otherwise, it will cause an excessively high gas-to-oil ratio in the short term, leading to reverse sulfidation; this aspect is often overlooked and deserves proper attention. If temporary parking is required, the main steam valve must be closed first, and the pressure in the steam drum must be released before the gas supply can be cut off. Otherwise, it will cause a sharp increase in the gas-to-vapor ratio, leading to reverse sulfidation and catalyst deactivation. 4) Strictly prevent hot water from flowing into the low-temperature converter, as this can cause caking and uneven distribution of the catalyst bed, thereby reducing the catalyst’s activity. In the event of water absorption, the bed temperature should be raised to ~250°C and the system operated for ~5 hours to dry it out before use again. 5) It is prohibited to use steam addition to address abnormal conditions during operation. If the oxygen content rises, adjust it by using steam pressure; or if the CO% increases due to issues such as a short circuit in the shift gas flow, the hot water pump running dry, or gas flowing through the saturation tower in a short circuit, use steam to maintain a proper level. It is necessary to accurately assess the situation before taking appropriate actions. 6) If the catalyst’s activity is affected by oil contamination, the hydrogen sulfide inlet concentration can be increased to 0.5 g/NM3 and the inlet temperature raised to 150–280°C; operating under these conditions for 8–20 hours while keeping the hotspot temperature at around 370°C, followed by a reduction of the temperature to around 210°C, can restore the catalyst’s activity without affecting production. However, this method should not be used frequently. 12. Appendix 12.1. Precautions for Using Carbon Disulfide and Manufacturers 12.1.1. Precautions when Using Carbon Disulfide Carbon disulfide is a pale yellow or colorless, transparent flammable liquid; it is soluble in alcohols and ethers but insoluble in water. Its specific gravity is 1.26, and its boiling point is 46.3°C. Precautions during storage or transportation: Carbon disulfide storage tanks should not be placed at high elevations; they must be kept away from other equipment, especially those that generate high temperatures such as heating devices, with a distance of at least 15 meters being ideal. When releasing carbon disulfide from the tank, it must not spill onto the ground – it should be stored in containers to prevent fires. The storage tanks must be kept free from oil contamination, and any contamination can be cleaned using hot alkaline water. Due to the low boiling point of carbon disulfide, the tanks containing it should be placed in a cool area, away from direct sunlight. The liquid level should be covered with water, or the tanks should be placed in a pool. In summer, it is best to fill the tanks with carbon disulfide at night. When storing or using carbon disulfide, open flames must be strictly avoided, and smoking or using fire near the tanks is prohibited. The pipes connecting the storage tanks should be made of steel or thick-walled rubber that can withstand pressure; plastic pipes should not be used as they may swell and rupture. In case of a leak that leads to a fire, the main valve of the nitrogen cylinder should be closed immediately, and the pressure should be released. Other fire-fighting measures should also be taken. CCI4 should not be used to extinguish the fire, as carbon disulfide is denser than water; water or steam can be used for extinguishing the fire. 12.1.2. List of carbon disulfide manufacturers (available at most general textile fiber factories): Sichuan Province: Sichuan Chengdu Textile Fiber Factory, Chengdu Chemical Industry Research Institute Experimental Factory, Chongqing Dongfeng Chemical Factory; Shanghai Municipality: Shanghai Electrochemical Factory, Shanghai No. 12 Textile Fiber Factory, Shanghai No. 1 Textile Fiber Factory; Shandong Province: Shandong Boshan Sulfur Factory, Shandong Zibo Hongqi Chemical Factory, Shandong Boshan Chemical Factory; Jiangxi Province: Jiangxi Provincial Chemical Industry Experimental Factory; Liaoning Province: Liaoning Benxi Zhengjiatun Chemical Factory, Liaoning Liaoyang Electrochemical Factory, Benxi City Chemical Factory, Dalian Fiberglass Factory, Dalian Insulation Materials Factory, Dandong Textile Fiber Factory, Tieling Chemical Factory; Hebei Province: Tangshan Aluminum Sulfate Factory; Shanxi Province: Changzhi County Phosphating Factory, Lingchuan County Maoguzhang Sulfur Factory; Heilongjiang Province: Heilongjiang Shuangyashan Shuguang Chemical Factory; Jiangsu Province: Wuxi Chemical Factory; Gansu Province: Gansu Baiyin Company, Lanzhou Chemical Industry Company; Guizhou Province: Guizhou *Shui County Chemical Factory; Shaanxi Province: Shaanxi Chengcheng County Chemical Factory; Guangxi Province: Guangxi Yishan County Pesticide Factory; Zhejiang Province: Yuyao Textile Fiber Factory; Tianjin Municipality: Tianjin Tanggu Bohai Chemical Factory; Hubei Province: Xiangfan Hubei Textile Fiber Factory; Hunan Province: Yiyang Daquan Chemical Factory; Henan Province: Xinxiang Textile Fiber Factory;
**Stage**, **Execution Time (hr)**, **Space Velocity (h-1)**, **Temperature at Various Points in the Bed (°C)**, **H2S Content entering the Furnace (g/Nm3)**, **Notes**
1. **Heating Up**: 6–8, 200–300, 70–210. First, use gas to purge the system and then use an electric furnace to raise the temperature.
2. **Sulfidation Period**: 10–15, 100–200, 210–300, 10–20. Wait until the H2S content in the exhaust gas is ≥3 g/Nm3 and the bed is penetrated.
3. **Intensification Period**: 4, 5, 100–200, 300–350, 350–450, 10–20. The H2S content at the exit of the converter should be ≥10 g/Nm3.
4. **Cooling and Purging**: ~6, 200–300, 180–20. The H2S content in the exhaust gas should be ≤1 g/Nm3, after which it can be used in production. Analyze the H2S concentration at the exit of the converter once per hour; if it exceeds 3 g/NM3, analyze it every half hour. After low-temperature vulcanization is complete, if it is necessary to remove the blind flanges in the system, it is strictly prohibited to remove both the inlet and outlet blind flanges at the same time, to prevent air from entering and damaging the catalyst. If it is not possible to do so in a timely and systematic manner, dry gas should be used to maintain positive pressure inside the furnace, thereby preventing negative pressure from allowing air to enter. 6.4. Handling of abnormal situations during the sulfidation process: Slow heating of the bed layer: Too low or too high flow rate of semi-water gas, or insufficient capacity of the electric furnace. Bed temperature rises sharply: excessive O2 content in semi-water gas; too rapid addition of CS2; excessive power usage by the electric furnace. Upon detecting a sharp rise in temperature, the cause is identified and preventive adjustments are made to avoid burning out the catalyst. 7. Normal operating conditions and precautions 7.1. Process parameters 7.1.1. For the medium-pressure shift to low-pressure shift system: steam-to-gas ratio: ~0.5; inlet temperature of the low-pressure shift unit: 170–210°C; CO content at the inlet of the low-pressure shift unit: 4–6%; CO content at the outlet: ≤1.5%; maximum bed temperature: ~250°C. H2S content in the gas from the medium-pressure shift unit: ~80 mg/NM3. The catalyst used in the low-pressure shift unit should be operated at low temperatures as much as possible, but the inlet temperature must be at least 30°C above the dew point. 7.1.2. Full low-pressure conversion: This depends on the processes used in various plants (copper washing, hydroformylation, methanation), and is generally as follows: Inlet temperature for the first stage: 200–230°C; inlet temperature for the second stage (low-pressure conversion section): ~180°C; CO content at the outlet of the first stage: 2–6%. Second-stage outlet CO: ≤1.5%. Transformed gas H2S content (total sulfur): ≥100mg/NM3. 7.2. Preventing catalyst resulfidation – Resulfidation is one of the causes of catalyst deactivation. Anti-sulfidation intensifies as temperature and gas-to-vapor ratio increase, as well as as H2S concentration decreases. Therefore, to maintain stable operating conditions, it is essential to keep the catalyst bed temperature and the gas-to-vapor ratio as low as possible, and an appropriate H2S level should be maintained (H2S level > 50 mg/NM3); this is a prerequisite for preserving the catalyst’s activity and lifespan. 7.3. Control of steam-to-gas ratio: When operating in the medium-pressure shift with low-pressure shift mode, the steam-to-gas ratio at the inlet of the converter should not be set too low (it should not be less than 0.40); otherwise, the Fischer-Tropsch reaction may occur, resulting in the formation of ethylene, acetylene, etc. This can lead to the formation of cuprous acetylide precipitates in the copper melt and cause issues with the copper washing liquid. Secondly, an excessively low gas-to-vapor ratio causes large fluctuations in the CO content at the conversion outlet, affecting normal production. 8. Parking 8.1. Temporary parking: Close the inlet and outlet valves of the low-pressure transformation system, as well as the drain and sampling valves, to maintain insulation and pressure. If the bed temperature drops, the system pressure should also be reduced to ensure that the bed temperature remains 30°C above the dew point; when the temperature falls below 120°C, the pressure must be reduced to atmospheric level, after which positive pressure is maintained using gas, shift gas, or refined gas stored in cylinders, to prevent air from entering. 8.2. Emergency shutdown: Similar to temporary shutdown, close the system’s inlet and outlet valves, as well as the drain and sampling valves, in order to maintain pressure and temperature; pay attention to the liquid level in the hot water tower to prevent it from rising too high and flowing into the low-temperature converter. 8.3. Long-term shutdown: Before shutting down the entire system, relieve pressure and use dry gas to cool the catalyst bed to a temperature below 40°C. Close the inlet and outlet valves of the low-temperature shift reactor as well as all pressure measurement and analysis sampling points, and install blind flanges. Maintain a slight positive pressure (approximately 30 mm of water column) using gas, shift gas, or refined gas stored in cylinders (such as nitrogen, with an O2 content of <0.1%); air must not enter the furnace under any circumstances. When it is necessary to inspect the catalyst bed, it must first be purged with N2 (O2 < 0.1%), and only then can the manhole be opened, in order to prevent gas convection from allowing air to enter the catalyst (i.e., the chimney effect). The temperature of the low-temperature converter can be reduced to 120–150°C by using steam for displacement. 9. When driving the process, whenever the temperature at any point in the bed is below the dew point temperature (0.75 MPa–120°C, 1.35 MPa–140°C), it is necessary to raise the temperature back above the dew point using dry gas before the gas can be fed into the medium-pressure conversion process. Otherwise, the vapor of intermediate-temperature gas will condense into water, causing the loss of potassium in the catalyst and thereby affecting its activity. In the early stages of operation, the system pressure is low and the gas-to-steam ratio is difficult to control properly, which can lead to catalyst resulfidation; at such times, the outlet CO content should be increased appropriately in order to maintain a lower gas-to-steam ratio. In the early stages of driving, the circulating water temperature is low; using a water heater to adjust the temperature may result in a too low inlet temperature for the water, leading to water contamination. Therefore, it is necessary to activate the gas bypass of the water heater in order to regulate the gas inlet temperature. 10. Catalyst removal and resulfurization: The low-temperature converter is cooled to below 20°C using dry gas, and the catalyst is removed through a discharge hole and placed in plastic bags or iron drums for storage. It can be reused without undergoing sulfurization and can operate directly in combination with gas. The re-vulcanization scheme is the same as the original vulcanization scheme; both the temperature and the vulcanization time at each temperature must meet the specified requirements. The amount of CS2 used can be half of that used during the initial vulcanization; during re-vulcanization, H2S penetrates quickly, but the overall vulcanization time cannot be reduced. The decline in activity caused by factors such as anti-sulfidation can be restored through resulfidation. 11. Catalyst maintenance during normal operation: Internal leakage in the heat exchanger is a major cause of abnormal catalyst deactivation; oxygen present in semi-water gas, along with oil and other impurities, can penetrate into the low-temperature converter and lead to permanent catalyst deactivation. Attention should be paid to the relationship between temperature rise and the CO content at the inlet and outlet; generally, a 1% reduction in CO results in a temperature rise of around 9°C. The temperature rise exceeds the corresponding value; internal heat leakage must be taken into account, as even a small amount of such leakage can cause serious damage to the catalyst. In the event of a sudden reduction in production volume, the steam supply should be immediately reduced or cut off. Otherwise, it will cause an excessively high gas-to-oil ratio in the short term, leading to reverse sulfidation; this aspect is often overlooked and deserves proper attention. If temporary parking is required, the main steam valve must be closed first, and the pressure in the steam drum must be released before the gas supply can be cut off. Otherwise, it will cause a sharp increase in the gas-to-vapor ratio, leading to reverse sulfidation and catalyst deactivation. 4) Strictly prevent hot water from flowing into the low-temperature converter, as this can cause caking and uneven distribution of the catalyst bed, thereby reducing the catalyst’s activity. In the event of water absorption, the bed temperature should be raised to ~250°C and the system operated for ~5 hours to dry it out before use again. 5) It is prohibited to use steam addition to address abnormal conditions during operation. If the oxygen content rises, adjust it by using steam pressure; or if the CO% increases due to issues such as a short circuit in the shift gas flow, the hot water pump running dry, or gas flowing through the saturation tower in a short circuit, use steam to maintain a proper level. It is necessary to accurately assess the situation before taking appropriate actions. 6) If the catalyst’s activity is affected by oil contamination, the hydrogen sulfide inlet concentration can be increased to 0.5 g/NM3 and the inlet temperature raised to 150–280°C; operating under these conditions for 8–20 hours while keeping the hotspot temperature at around 370°C, followed by a reduction of the temperature to around 210°C, can restore the catalyst’s activity without affecting production. However, this method should not be used frequently. 12. Appendix 12.1. Precautions for Using Carbon Disulfide and Manufacturers 12.1.1. Precautions when Using Carbon Disulfide Carbon disulfide is a pale yellow or colorless, transparent flammable liquid; it is soluble in alcohols and ethers but insoluble in water. Its specific gravity is 1.26, and its boiling point is 46.3°C. Precautions during storage or transportation: Carbon disulfide storage tanks should not be placed at high elevations; they must be kept away from other equipment, especially those that generate high temperatures such as heating devices, with a distance of at least 15 meters being ideal. When releasing carbon disulfide from the tank, it must not spill onto the ground – it should be stored in containers to prevent fires. The storage tanks must be kept free from oil contamination, and any contamination can be cleaned using hot alkaline water. Due to the low boiling point of carbon disulfide, the tanks containing it should be placed in a cool area, away from direct sunlight. The liquid level should be covered with water, or the tanks should be placed in a pool. In summer, it is best to fill the tanks with carbon disulfide at night. When storing or using carbon disulfide, open flames must be strictly avoided, and smoking or using fire near the tanks is prohibited. The pipes connecting the storage tanks should be made of steel or thick-walled rubber that can withstand pressure; plastic pipes should not be used as they may swell and rupture. In case of a leak that leads to a fire, the main valve of the nitrogen cylinder should be closed immediately, and the pressure should be released. Other fire-fighting measures should also be taken. CCI4 should not be used to extinguish the fire, as carbon disulfide is denser than water; water or steam can be used for extinguishing the fire. 12.1.2. List of carbon disulfide manufacturers (available at most general textile fiber factories): Sichuan Province: Sichuan Chengdu Textile Fiber Factory, Chengdu Chemical Industry Research Institute Experimental Factory, Chongqing Dongfeng Chemical Factory; Shanghai Municipality: Shanghai Electrochemical Factory, Shanghai No. 12 Textile Fiber Factory, Shanghai No. 1 Textile Fiber Factory; Shandong Province: Shandong Boshan Sulfur Factory, Shandong Zibo Hongqi Chemical Factory, Shandong Boshan Chemical Factory; Jiangxi Province: Jiangxi Provincial Chemical Industry Experimental Factory; Liaoning Province: Liaoning Benxi Zhengjiatun Chemical Factory, Liaoning Liaoyang Electrochemical Factory, Benxi City Chemical Factory, Dalian Fiberglass Factory, Dalian Insulation Materials Factory, Dandong Textile Fiber Factory, Tieling Chemical Factory; Hebei Province: Tangshan Aluminum Sulfate Factory; Shanxi Province: Changzhi County Phosphating Factory, Lingchuan County Maoguzhang Sulfur Factory; Heilongjiang Province: Heilongjiang Shuangyashan Shuguang Chemical Factory; Jiangsu Province: Wuxi Chemical Factory; Gansu Province: Gansu Baiyin Company, Lanzhou Chemical Industry Company; Guizhou Province: Guizhou *Shui County Chemical Factory; Shaanxi Province: Shaanxi Chengcheng County Chemical Factory; Guangxi Province: Guangxi Yishan County Pesticide Factory; Zhejiang Province: Yuyao Textile Fiber Factory; Tianjin Municipality: Tianjin Tanggu Bohai Chemical Factory; Hubei Province: Xiangfan Hubei Textile Fiber Factory; Hunan Province: Yiyang Daquan Chemical Factory; Henan Province: Xinxiang Textile Fiber Factory;