Seeking help with the catalyst pretreatment and vulcanization process

A. Purpose and basic principles of catalyst sulfidation: Catalyst presulfidization is based on the hydrogenolysis of a sulfiding agent (DMDS) to produce hydrogen sulfide (H2S), which then reacts with the oxidized states of the active metals in the catalyst to form the corresponding metal sulfides. The relevant sulfidation reactions are as follows: (CH3)2S2 + 3H2 → 2H2S + 2CH4; MoO3 + 2H2S + H2 → MoS2 + 3H2O; 3NiO + 2H2S + H2 → Ni3S2 + 3H2O; WO3 + 2H2S + H2 → WS2 + 3H2O. B. Which sulfiding agent is used and what is the sulfiding method? For cracking, the sulfiding agent is DMDS and the sulfiding method is dry sulfiding. For treatment, the sulfiding agent is also DMDS but the sulfiding method is wet sulfiding. The base oil for sulfidation is straight-run light diesel. C. Location of the sulfur injection point and the sulfur injection process: For cracking, the sulfur injection point is located at the inlet of reactor F01001. For treatment, it is located at the inlet of P01001AB. D. Initial conditions for sulfidation: For cracking sulfidation, the initial pressure in the cold fractionator is 13.63 Mpa ； The recycle hydrogen compressor K01002 is operating normally, with a gas-to-agent volume ratio of 300–600:1 ； The inlet temperature of reactor R01001 is maintained at 190°C, while the temperatures of each bed layer are controlled between 165 and 175°C. Initial conditions for sulfurization treatment: cold high-pressure is 14.0 MPa ； The recycle hydrogen compressor K01002 is operating normally, with a gas-to-agent volume ratio of 300–600:1 ； The inlet temperature of reactor R01001 is maintained at 190°C. Hydrogen-to-oil ratio >700:1 (by volume); purity of circulating hydrogen ≮85% (V); D01004 pressure: 15.0±0.05 MPa ； D01004 liquid level: 50±5% D01005 pressure: 2.5±0.05 MPa ； Liquid level of D01003: 50±5% Liquid level of D01005: 50±5% ； 　　　 D01002 liquid level: 50±5% D01002 temperature: 275±2℃ ； D01004 temperature ≯50℃; D01005 temperature ≯50℃. E. How many steps are there in the sulfidation process, and what are the requirements for hydrogen sulfide concentration at each stage? Cracking sulfidation step: During the sulfidation phase, the heating rate and related technical parameters are as follows – the H2S concentration in the recycled hydrogen is v%: during the heating phase from 175℃ to 230℃, the heating rate is 3℃/h, and the temperature of any point in the bed layer must not exceed 230℃ until H2S no longer penetrates at the outlet of R01002. 01–05: Maintain a temperature of 230°C; the vulcanization time at this temperature should be ≥8 hours. The temperature can be increased only after the dew point of the circulating hydrogen at the outlet of the R01002 reactor reaches -19°C. 01～05: Heating phase at 230℃～290℃, at a rate of 4℃/h; the dew point of the recycled hydrogen at the outlet of reactor R01002 is -19℃. 05～1.0 at a constant temperature of 290°C for 2 hours; the duration of this constant-temperature period may be extended depending on the sulfur absorption by the catalyst. 05～1.0: During the temperature increase phase from 290℃ to 370℃, the temperature is increased at a rate of 6℃/h; if the dew point of the recycled hydrogen at the outlet of reactor R01002 is -19℃, the temperature increase is paused. 05～1.0 at a constant temperature of 370℃; the sulfurization time at this constant temperature should be ≥8 hours. Pre-sulfurization is complete when the dew point difference between the inlet of R01001 and the outlet of reactor R01002 is 3℃, the H2S concentration remains essentially unchanged, and the water level in the high-pressure separator no longer rises. 10–20 Sulfidation treatment steps: Reactor inlet temperature, °C; Control of hydrogen sulfide in the circulating hydrogen, V%; Temperature rise/fall rate, °C/h; Time, h; DMDS injection rate, Kg/h. 190°C: 10–15, 0; 190°C: 4 (constant temperature wetting); 190–230°C: 0.1–0.5, ~10, 4; 230°C: 0.1–0.5, 8; 230–260°C: 0.5–1.0, ~10, 3; 260°C: 0.5–1.0, 8; 260–200°C: 0.5–1.0, 15–20, 4; 200–290°C: 0.5–1.0, 10–15, 9; 290–320°C: 1.0–2.0, 5–10, 6; 320°C: 1.0–2.0, 8. Maintain a constant temperature at 320°C until the hydrogen sulfide concentration in the circulating hydrogen reaches 1%. F. Items analyzed in the sulfidation process and locations of sampling points: Analysis items for the cracking sulfidation process: (1) Introduction of hydrogen to the unit and purging: Composition of the new hydrogen and hydrogen purity. Sample and analyze the purity of recycled hydrogen at D01010. (2) After pre-vulcanization begins: Circulating hydrogen: H2S content – 1 time every half hour; Hydrogen purity – 1 time every 4 hours; Gas composition – 1 time every 8 hours. Fresh hydrogen: Hydrogen purity – 1 time every 24 hours; Gas composition – 1 time every 24 hours. Wastewater: Total sulfur content – 1 time every 2 hours. *In principle, the purity should be measured every 4 hours as specified, but in special cases, analysis should be carried out according to the recommendations of on-site technical personnel. Analysis items for the sulfidation process: (1) Analysis items during hydrogen introduction for displacement 　 ① Fresh hydrogen: hydrogen purity, hydrocarbon composition, CO, and CO2 content 　 ② Sampling from the cold high-pressure separator: hydrogen purity (2) Analysis items and frequency during sulfidation 　 ① Fresh hydrogen: hydrogen purity and composition, once every 4 hours 　 ② Recycled hydrogen: hydrogen sulfide content, once every hour ； Hydrogen purity and composition are checked every 4 hours. 　 ③Separate gases at low temperature and low pressure: hydrogen sulfide content is checked every 4 hours, and the gas composition is checked every 4 hours. 　 ④Sulfurized oil: Sulfur content at the P01001A/B inlet and the D01005 outlet is measured every 4 hours. ⑤Sulfur-containing wastewater: Maintain a constant temperature at 175°C, 230°C, 290°C, and 340°C respectively, and analyze the sulfur content in the water after completion. G. Requirements of the sulfidation process for recycled hydrogen: *In principle, the purity should be measured at specified intervals every 4 hours, while the hydrogen sulfide content should be checked once per hour ； However, in special cases, analysis should be carried out according to the recommendations of on-site technical personnel. H. What are the limitations during the sulfidation process? Cracking: During the entire pre-sulfidization period, the high-pressure level must be maintained at 13.63 MPa, with hydrogen purity ≥85%. If it is below this value, the exhaust emissions increase. Treatment: Maintain the pressure of D01007 at 13.9 MPa. Hydrogen purity is greater than 85 v%. I. Indicators of completion of sulfidation: Catalytic cracking: Under conditions where the inlet temperature of R01001 is 370°C and the H2S concentration in the recycle hydrogen is 10,000–20,000 ppm, the dew point difference between the gas entering R01001 and the gas exiting R01002 is ≤3°C, and both values are below -19°C. After stopping the DMDS injection (and switching to a DMDS cycle), the H2S concentration in the inlet gas of R01001 was essentially the same as that in the outlet gas of R01002, with the H2S concentration remaining above 1 v% for at least 4 consecutive hours. High scores are basically generated continuously without water. When the above conditions are met, it is considered that the vulcanization endpoint has been reached; then the temperature is maintained at that level for another 1 hour. Treatment: ① The amount of vulcanizing agent added has reached 60%–70% of the sulfur amount required according to the theory of catalyst vulcanization. 　 ②The H2S concentration in the system no longer decreases. ③There is no significant increase in water content in high-scoring plants. J. How to measure high-pH acidic water: After sulfidation begins, water is continuously generated. A dedicated person should be assigned to keep track of and measure the amount of water produced. High-pH values need to be measured using specialized instruments. In the absence of specific requirements, water should be drained in quantities determined by the liquid level; each time water is drained, its volume should be measured and the sulfur content in the water analyzed. It is necessary to plot curves corresponding to the sulfidation process, such as curves showing temperature and the amount of water generated, as well as curves relating the injection rate of the sulfiding agent to the amount of water produced.