Weekly Topic: What are the methods for sulfiding sulfur-tolerant shift catalysts? What are their respective features? (6.19-6.25)

There are two methods for vulcanization: one involves using gas from the system itself, and the other uses gas purchased externally. The main steps are as follows: 1. Preparation work for vulcanization: (1) Catalyst heating for vulcanization should be carried out after the system has been purged, pressure-tested, and the catalyst has been installed. (2) The technical improvement projects and cleaning tasks for the low-temperature transformation, transformation and decarburization systems have all been completed, without affecting the heating of the catalyst or the startup process. (3) All electrical equipment (including microcomputers), instruments, self-regulating valves, lighting, signaling, alarm systems, interlocks, etc. shall be installed and tested properly and kept in standby. (4) Lubricate the valves and screws in the system once. (5) Personnel have completed their position-specific training and are fully familiar with the heating and startup procedures, so as to have a clear understanding of them. (6) All 380V and 10,000V operating equipment has been tested and is in good condition, ready for use without affecting the startup schedule. New equipment is placed in standby after undergoing individual testing or joint testing first. (7) The electric heating unit is ready after passing the commissioning tests; it is connected to the sulfidation system, while the deionized water and circulating water are prepared for use. (8) Clean up all debris at the site, cover the manhole covers properly, and ensure that fire-fighting equipment and protective gear are in good condition and ready for use. (9) Check that the packing and catalysts used in the low-temperature transformation furnace, as well as the CS2 used for heating, have arrived; verify whether their models, specifications, and quantities meet the requirements, and the manufacturer shall also provide documents regarding product quality and performance. Check that the catalyst, as well as the steel wire meshes laid above and below the packing layer, and the refractory balls are all present in sufficient quantity, and that their types and quantities match. (10) Has the sulfurization plan arrived at the site? (11) Carbon disulfide storage tanks must be free of oil contamination; any oil deposits can be removed using hot alkaline water or carbon disulfide. Additionally, a pressure test at 0.5 MPa must be conducted to ensure that there are no leaks in all connecting valves. (12) The hoses used for sulfidation should be gas-plastic pipes with a fiber reinforcement network; it is essential to check whether there is such a network inside the wall. Wireless network devices are of poor quality; they can easily become clogged as a result of swelling caused by carbon disulfide. Or use a plastic water pipe with a Φ10 fiber inner mesh. 2. Heating vulcanization scheme: Carbon disulfide is used as the vulcanizing agent, and either venting or circulating vulcanization methods can be employed. During the vulcanization process, the system should be kept at atmospheric pressure as much as possible, with strict prevention of steam and water from entering. The temperature-raising sulfidation schedule is as follows: Phase, Time (h), Space velocity (h-1), Bed temperature (°C), CS2 addition rate (l/h), Remarks. Temperature-raising period: 4–6, 200–300, 200–220; the system is replaced with semi-water gas, after which the electric furnace is started. Sulfidation period: ~16, 200–300, 200–300, 40–100; the H2S concentration in the outlet gas should be >3 g/m3. Bed layer penetration. Intensification phase: ~12, 200-200, 350-450, 60-120. It is required that the H2S concentration in the exhaust gas be >10 g/m3. Cool down and replace at 4–6, 200–300, 180–200, until the hydrogen sulfide concentration at the outlet is ≤1 g/m3. and integrated into the system. Note: The H2S concentration at the outlet of the converter is analyzed every 2 hours; when H2S > 3 g/NM3, it is analyzed every hour ； Analyze the O2 level every half hour. 3. Sulfidation process 3.1. Preparation for sulfidation Before raising the temperature for sulfidation, inert gas should be used first, followed by the introduction of gas to displace the air from the system; care must be taken to ensure that all dead corners and the pipelines used for temperature increase are properly purged. 3.2. Heating phase: Room temperature to 210°C (4–6 hours). (1) After being replaced with inert gas or semi-water gas and verified to be suitable, the process is switched to using semi-water gas for heating, with the semi-water gas proceeding through the sulfidation process. Maintain the system at atmospheric pressure, with the temperature at the exit of the electric furnace kept constant at 230–250°C. At this point, the temperature at the inlet of the low-temperature converter is around 210°C, while the temperature of the bed layer ranges from 210°C to room temperature. (2) During the heating process, the O2 content in the gas should be kept below 0.5% to prevent fires and explosions in the electric heater; moreover, the system pressure must be strictly controlled to not exceed 0.1 MPa to avoid overpressure in the electric heater. (3) Before the heating of the gas is completed, the sulfidation tank should be filled with CS2 as required; check that the pipeline supplied by the nitrogen generator is unobstructed, and raise the pressure to 0.1–0.2 MPa for standby use. 3.3. Sulfidation stage (1): Once the inlet temperature of the low-temperature converter reaches 210°C, CS2 can be pumped into the system using N2. The amount of CS2 added is controlled by the flow meter at the outlet of the sulfidation tank, so as to maintain a CS2 concentration of 5–10 g/m3 in the furnace, thereby initiating the sulfidation process. (2) Control the outlet temperature of the electric furnace at 200–250°C. The catalyst bed temperature is maintained at 200–300°C for a period of about 8–10 hours; once the hydrogen sulfide concentration at the outlet reaches ≥ 3 g/NM3, it can be considered that the initial stage of sulfidation is complete. (3) During sulfidation, pay close attention to the bed temperature, and adjust it by controlling the number of electric heaters, the amount of CS2 added, and the volume of gas. (4) During sulfidation, the H2 content at the furnace inlet should be maintained at ≥25% to facilitate the hydrogenolysis of CS2. 3.4. Strengthening phase: The temperature at each point in the catalyst layer is maintained at 400–450°C for ~4 hours; the H2S content at the outlet remains ≥10 g/NM3, marking the end of the intensified sulfidation process. 3.5. Cooling and displacement phase: (1) Once sulfidation is complete in all sections, the cooling and displacement phase begins. The outlet temperature of the electric furnace is controlled at 200°C; once the bed temperature drops to ≤300°C, the addition of CS2 for displacement is stopped. (2) After connecting for maintenance, removing and installing blind flanges, gas can be introduced to produce qualified shift gas for startup. (3) After operating in normal-pressure vent mode for two hours, the syngas can be sent to subsequent processes only once its composition meets the specified standards. (4) Precautions: (1) The heating and vulcanization process must be carried out in strict accordance with the specified requirements; during the heating phase, the temperature at any single point shall not exceed 500°C, and the heating rate must be maintained at 30∽50°C/h. (2) During the sulfidation process, the O2 percentage in the incoming gas must be strictly controlled to prevent an increase in O2 levels from causing a sudden rise in furnace temperature and damaging the catalyst. The amount of CS2 also needs to be adjusted accordingly based on the level of H2S in the incoming gas, so as to avoid adding too much of it, which could lead to a sharp rise in furnace temperature, or adding too little, which would result in slow sulfidation. (3) If a sharp rise in temperature is detected, the cause should be identified immediately, and preventive adjustments should be made to avoid damaging the catalyst. (4) Be sure to wait until the condensate water has been drained before entering the subsequent equipment. (5) The entire vulcanization process is carried out at atmospheric pressure. (6) When starting the electric furnace in the system, it is necessary to first check the cooling water, then introduce air, and finally start the furnace; when shutting it down, turn off the power to the furnace first and then cut off the air supply. For hot water heaters and soft water heaters, water should be circulated first before air is introduced. (7) Operators must be familiar with the process flow, valve locations, and all auxiliary lines. (8) When heating semi-water gas, it is necessary to pay attention to promptly draining the drain from the oil-water separator and activating the oil removal filter, in order to prevent water from entering the electric furnace and the catalyst layer. (9) During the sulfidation process, in case of an CS2 fire, an increase in O2 levels, or other emergencies such as a disruption in the supply of demineralized water, it is necessary to immediately implement the \"three stops and one shutdown\": stop the furnace, stop the CS2 supply, stop the gas supply, and close the vent. The B303Q catalyst is a cobalt-molybdenum-based sulfur-resistant low-temperature catalyst, whose main components are cobalt oxide (CoO) and molybdenum trioxide (MoO3). Before use, it needs to be activated—sulfided, so that the oxidized cobalt and molybdenum are converted into sulfides in order to achieve high activity. The specific method involves using semi-water gas as a carrier and carbon disulfide as a sulfurizing agent; at temperatures above 180–200°C, CS2 is continuously added to hydrogen to undergo a hydrolysis reaction that produces H2S, which then reacts with CoO and MoO3 to form CoS and MoS2. The chemical reactions are as follows: MoO3 + 2H2S + H2 = MoS2 + 3H2O, ΔH0 = -48.2 KJ/mol; CoO + H2S = CoS + H2O, ΔH0 = -13.4 KJ/mol; CS2 + H2 = 2H2S + CH4, ΔH0 = -240 KJ/mol

Reply to 1# 654262293: Before use, the oxidation state of the active components in sulfur-resistant low-temperature shift catalysts generally needs to be converted to a sulfide state; this conversion process is known as sulfidation. Since the sulfidation reaction is a highly exothermic reaction, manufacturers using low-activation catalysts sometimes experience overheating incidents and catalyst damage during sulfidation. 1. Sulfidation preparation (1) Catalyst heating for sulfidation must be carried out after the system has been purged, pressure-tested, and the catalyst has been loaded. (2) The technical improvement projects and cleaning tasks for the low-temperature transformation, transformation and decarburization systems have all been completed, without affecting the heating of the catalyst or the startup process. (3) All electrical equipment (including microcomputers), instruments, self-regulating valves, lighting, signaling, alarm systems, interlocks, etc. shall be installed and tested properly and kept in standby. (4) Lubricate the valves and screws in the system once. (5) Personnel have completed their position-specific training and are fully familiar with the heating and startup procedures, so as to have a clear understanding of them. (6) All 380V and 10,000V operating equipment has been tested and is in good condition, ready for use without affecting the startup schedule. New equipment is placed in standby after undergoing individual testing or joint testing first. (7) The electric heating unit is ready after passing the commissioning tests; it is connected to the sulfidation system, while the deionized water and circulating water are prepared for use. (8) Clean up all debris at the site, cover the manhole covers properly, and ensure that fire-fighting equipment and protective gear are in good condition and ready for use. (9) Check that the packing and catalysts used in the low-temperature transformation furnace, as well as the CS2 used for heating, have arrived; verify whether their models, specifications, and quantities meet the requirements, and the manufacturer shall also provide documents regarding product quality and performance. Check that the catalyst, as well as the steel wire meshes laid above and below the packing layer, and the refractory balls are all present in sufficient quantity, and that their types and quantities match. (10) Has the sulfurization plan arrived at the site? (11) Carbon disulfide storage tanks must be free of oil contamination; any oil deposits can be removed using hot alkaline water or carbon disulfide. Additionally, a pressure test at 0.5 MPa must be conducted to ensure that there are no leaks in all connecting valves. (12) The hoses used for sulfidation should be gas-plastic pipes with a fiber reinforcement network; it is essential to check whether there is such a network inside the wall. Wireless network devices are of poor quality; they can easily become clogged as a result of swelling caused by carbon disulfide. Or use a plastic water pipe with a Φ10 fiber inner mesh. 2. Heating vulcanization scheme: Carbon disulfide is used as the vulcanizing agent, and either venting or circulating vulcanization methods can be employed. During the vulcanization process, the system should be kept at atmospheric pressure as much as possible, with strict prevention of steam and water from entering. 3. Sulfidation process 3.1. Preparation for sulfidation 3.2. Heating phase 3.4. Intensification phase 3.5. Cooling and displacement stage

The sulfidation of sulfur-resistant low-temperature shift catalysts can be divided into solid sulfidation and liquid sulfidation methods depending on the sulfiding agent used； Based on the use of hydrogen sulfide, it can be divided into the one-pass method and the recycling method. We have never used solid vulcanizing agents, so we can’t speak casually about them. Let’s now compare the one-pass method and the cyclic method. The advantage of the one-pass method is that it eliminates the need for a gas cooler; however, its disadvantages include gas waste, environmental pollution, and increased costs associated with heating and reduction processes. The only drawback of the cyclic method is the need to add a gas cooler; its advantages lie in saving the heating and reduction gases, thereby reducing the costs associated with heating and reduction. Most importantly, it helps to reduce pollution and protect the environment.

This post was last edited by 654262293 on 2011-6-20 at 12:32. There are online vulcanization and cyclic vulcanization, and the precautions for each are different. Note 1: Sulfidation principle: multiple times, in small amounts. When the bed temperature does not rise, increase the dosage; once it rises sharply, cut off the process gas and introduce nitrogen to cool it down. 2. Try to keep the inlet temperature stable. 3. H2S should be analyzed fully once per hour. 4. Pay attention to alternating pressure increase and temperature increase.