What are the precautions for heating and reducing copper-based catalysts in methanol synthesis towers?

Catalytic heating reduction: 1 Preparation work: ① Purge the synthesis system with N2; ensure that the oxygen content at all sampling points in the analysis system is below 0.1×10-2, and then increase the pressure to 0.8 Mpa. ② The compressor is in standby mode, and the utility supplies are normal. ③ The on-site communication and liaison facilities are complete, have passed inspection, and are sensitive and reliable. ④ Analytical instruments, meters, weighing equipment, various charts, and reports are ready. ⑤ The purification unit can provide qualified purified gas (or by purchasing qualified hydrogen and installing temporary pipelines). ⑥ Check the valves that need to be opened: A. The isolation valves before and after the boiler feed water and blowdown systems; the isolation valves at both ends. The boiler feed water pump should be started in accordance with the regulations to establish water circulation. There are two valves at the outlet base of the B separator, at the sewage discharge point at the filter inlet; these valves are removed and temporary pipelines are connected to introduce water for weighing. C. The root stop valves for each safety valve. D. Isolation valves at the base of each pressure gauge, flow meter, analyzer, and level gauge. ⑦ Check the valves that should be closed: the main fresh air inlet valve for Compressor A and its bypass valve. B. Dual valves for nitrogen filling on the pipeline (for reversing the flow through the blind flange); C. Dual valves for steam entry into the drum along the chemical dosing pipeline, as well as cut-off valves before and after water addition and bypass valves. D. Vent valves such as those on the drum, and dual blowdown valves. E. Cut-off valves and bypass valves before and after hydrogen recovery from the vent gas. F. Double valve for instrument air on the instrument air pipeline (blind plate to reverse blind plate). H. Drain valves for various equipment, pipelines, and self-regulating valve assemblies, as well as valves for various sampling pipelines. 1.2.2 Add boiler water at room temperature to the drum; once the drum level reaches 50%, close the water supply valve 4. (If the water temperature in the drum boiler is too high, demineralized water can be added.) 1.2.3 Feed circulating water to the water cooler; pay attention to venting at the high points and draining at the low points. 1.2.4 Catalyst heating and reduction step (catalyst model: Southwest Research Institute): ① Contact the dispatch team to start the compressor; maintain a pressure of 0.8 Mpa through the anti-surge valve and control system, with an air velocity of 50,000 Nm3/h. Establish an N2 circulation in the synthesis loop (Note: At this time, the anti-surge valves in the compression section should be fully open, while the flow rate in the control circulation section should be kept at 50,000 Nm3/h). ② Introduce process steam in front of the inlet valve; slightly open the shut-off valve and drain water through the drain line. After warming the pipes for 30 minutes, close the drain line, then slowly open the valve to supply steam to the drum. The steam supply should be carried out gradually, and the heating rate of the synthesis tower should be adjusted in accordance with the requirements outlined in the catalyst heating and reduction schedule. Catalyst reduction schedule: Reduction stage, Temperature range (°C), Heating rate (°C/h), Time required (h), Total time (h), Hydrogen content (10-2). Initial stage: Room temperature to 100, ≤25, 6, 6, 0; 100, 0, 1, 7; 100–160, 10, 6, 13, 0. Main stage: 160, 0, 1, 14; 0.2–0.5, 160–170, 4, 3, 17; 1, 170, 0, ≥15, 32; 1, 170–180, 3–4, 3, 35; 1, 180–190, 3–4, 3, 38; 1.2–1.5, 190–200, 3–4, 3, 41; 1.2–1.5. Final stage: 200–210, 5, 2, 43; 1.2–1.5, 210–230, 10, 2, 45; 1.5–2, 230, 0, 1–2, 46; 2, 230, 0, 1–2, 47; 5, 210–10, 2, 49; 10–15. ④ Description of the heating and reduction process: The catalyst is heated in accordance with the requirements specified in the catalyst heating and reduction schedule. Once the temperature at the hottest point inside the tower rises above 40°C, the liquid level in the separator should be monitored promptly. When the liquid level rises, drainage is carried out through the valve assembly in front of the crude alcohol filter, with measurements taken every half hour. Once the temperature reaches 170°C, it is maintained at that level for 1 hour; if the actual amount of water discharged matches the theoretical value, then the heating phase is complete. Contact the dispatch team to supply fresh syngas to the synthesis loop through the auxiliary valve associated with the main valve at the compressor inlet, thereby controlling the concentration of gas entering the tower (H2+CO) at 0.5–1%. The catalyst is first reduced at a reaction temperature of 170°C; as the concentration of (H2+CO) decreases, H2+CO can be added via the auxiliary valve until the hydrogen concentrations at the inlet and outlet of the methanol synthesis tower are equal. Maintain the (H2+CO) concentration at 0.5–1%, gradually increase the opening degree of TV7039 to raise the steam flow rate, and reduce the catalyst at a temperature rise rate of 2°C/h. Before each temperature increase, the hydrogen concentrations at the inlet and outlet of the methanol synthesis tower must be equal, to ensure that the catalyst is fully reduced at each temperature level. Once the catalyst temperature reached 190°C, the concentration of the gas fed into the reactor (H2+CO) was adjusted to 1–2%, and the catalyst temperature was raised to 210°C at a rate of 0.5°C/h℃ ； Continue to increase the concentration of the gas fed into the reactor (H2+CO) to 2–10%, and raise the catalyst temperature to 230°C at a rate of 2.5°C/h. At this temperature, further increase the concentration of the gas fed into the reactor (H2+CO) to 10–20%, and carry out reduction at a constant temperature for 2 hours until the reduction is complete. ⑤ Precautions for temperature-induced reduction: A. Analyze the H2, CO, and CO2 levels at the inlet and outlet of the synthesis tower every half hour. Throughout the reduction period: the concentration difference (H2+CO) at the inlet and outlet of the synthesis tower was around 0.5%, with a maximum value not exceeding 1.0%. B. The hot spot temperature in the synthesis tower is controlled by the amount of heating steam supplied by TV7039 and the steam pressure in the drum; when the liquid level is high, it can be discharged through the drain line. C. Control the CO2 content in the circulating gas to be <5%, and the water vapor concentration to ≤5000 PPm. If the CO2 content exceeds 5%, increase the N2 supply valve to remove the excess CO2 via PV7029. D. Continuously monitor the temperature at the hot spots; if there is a sudden increase in temperature or if issues such as compressor failure or power outages occur, immediate action must be taken to cut off H2+CO, close the steam inlet valve, increase the drainage from the drum, and add low-temperature deionized water ； Supply nitrogen gas ； Measures such as system depressurization are taken to maintain stable temperature in the synthesis tower. E. Determination of the reduction endpoint: ⅰ. The cumulative amount of water released approaches or reaches the theoretical value; this amount is approximately 17×10-2 to 19×10-2 times the weight of the catalyst, with physical water accounting for 3×10-2 to 5×10-2 and chemical water accounting for 13×10-2 to 15×10-2 ； ii. The water discharge rate is zero or less than 1.2 Kg/h ； Ⅲ. The concentrations of (H2+CO) at the inlet and outlet of the synthesis tower are essentially equal. F. Principles for temperature-controlled reduction: ⅰ. Three lows: low-temperature effluent, low-hydrogen reduction, and a period of low-load operation after reduction. ⅱ. Three stabilities: temperature stability, hydrogen supplementation stability, and water output stability. Ⅲ. Three prohibitions: Temperature increase and hydrogen addition must not be carried out simultaneously ； Moisture must not be introduced into the synthesis tower ； Do not allow water to flow at high temperature for a long time. ⅳ. Three controls: Control the H2 supplementation rate ； Control CO2 concentration ； Control the water outlet speed. 1.2.5 Synthetic gas introduction: After the catalytic reduction is complete, maintain the temperature at the hot spot between 210°C and 220°C; close the nitrogen supply valve and install a blind flange, as well as close the valve for the reducing gas supply. At the same time, gradually open the main valve for fresh gas to enter the compressor in order to introduce purified gas. By adjusting the flow rate of the heating steam and the drum pressure for TV-7039, the hot spot temperature in the synthesis tower is controlled at 210–220°C; the rate of pressure increase per hour is kept at 10% of the design pressure (as required for the synthesis loop), thereby raising the synthesis pressure to 5.3–8.3 Mpa(G). When the separator level rises, open the dual cut-off valve in front of the separator and switch it to automatic mode. Once the drum is equipped with a pressure indicator, set its pressure to 0.5 Mpa(G) and switch it to automatic mode. When the methanol tank level rises, open the valve and switch to automatic mode. Control the drum liquid level at 65% via the valve; once the level is stable, engage the interlock for the control valve. Based on the steam demand of the pipeline network, initially steam is supplied to the low-pressure steam network when the pressure is above 1.3 Mpa(G); once the pressure in the boiler exceeds 2.0 Mpa(G), the valve is opened to send the generated steam outside. The steam superheater will be put into use in a timely manner depending on the circumstances. Feed a Na3PO4 solution into the drum from the transformation system; based on the analysis data, activate continuous blowdown for the drum, and carry out intermittent blowdown as required. Once the hydrogen recovery unit is ready for operation, start the hydrogen recovery process by introducing vent gas. Once the hydrogen recovery unit is operating properly, the hydrogen is directed to the compressor inlet, where it mixes with fresh gas to continue participating in the methanol synthesis reaction. The synthesis system operated at a low load under a pressure of 6.0 Mpa(G) for 2–3 days. 1.2.6 Once the catalyst activity is normal and the process in the synthesis system is stable, the compressor load is increased, the system pressure is maintained at 5.3–8.3 Mpa(G), and the system enters normal operation. 1.3 Notes: 1.3.1 During catalytic heating and reduction, the system should maintain a low pressure as much as possible ； The air velocity is controlled at 50,000 h-1. 1.3.2 During catalytic heating reduction, minimize the CO content in the reducing gas and increase the H2 content. 1.3.3 If there are differences between this plan and the technical requirements provided by the catalyst manufacturer, the manufacturer’s heating and reduction procedure shall prevail.

C207 diol catalyst high-hydrogen temperature-raising reduction plan: Phase, Time: h; Peak temperature: °C; Axial temperature difference: °C; Heating rate: °C/h; System pressure: Mpa; H2 concentration: %; Water vapor concentration: g/Nm3; Water output rate: kg/30 minutes; Space velocity: h-1; Remarks. Planned value, Cumulative value. Heating phase: 3, 3; Room temperature to 70 °C, ≤10, ≤30, 5.0, ≥65, ≤1.0, ≤20, ≥3000; Water release attempted after reaching 65 °C. Phase 3: 6, 70–80 °C, ≤10, ≤6, 5.0, ≥65, ≤2.5. Initial stage: 27, 33; 80–120 °C, ≤20, ≤2, 5.0, ≥65, ≤2.5; Increase circulation rate. Main phase: 12, 45; 120–160 °C, ≤20, ~4, 5.0, ≥70, ≤2.0, ≤25; 12, 57; 160–180 °C, ≤20, ~3, 5.0, ≥70, ≤2.0. Final stage: 8, 65; 180–240 °C, ≤20, 6–10, 5.0, ≥65, ≤1.0; Constant temperature phase: 2–4, 68; 240 °C, ≤15, 0, 6.0, ≥65, ≤0.2; Bottom temperature ≥230 °C. Cooling phase: 2, 70; 240–220 °C, ≤20, ≤-10, 6.0. Adjustment and aeration phase: 2, 220 °C, ≤20. Gradual increase in pressure under light load: 24, 230±5 °C, ≤20, 11.0, CO

This post was last edited by Chemical Gas Purification on 2010-11-28 at 12:51. I agree with the heating and reduction approach suggested in the third floor comment. There are two points to keep in mind when using copper methanol catalysts for heating and reduction: First, a high space velocity should be employed; whenever possible, use a high space velocity, which means turning on all the circulation pumps available； The second is to remove as much of the physical and chemical water from the catalyst as possible at low temperatures, that is, to achieve water removal at low temperatures. Another point is that when high-hydrogen reduction is used, and the temperature rises to 80°C–100°C, it is necessary to pay attention to the temperature trend in the catalyst layer in order to prevent excessive temperatures from destroying the catalyst.

Is it really necessary to maintain such a high pressure for low-hydrogen reduction on the 2nd floor? 0.8 MPa?? The basic principle for reduction is to ensure stable effluent quality. This covers all the issues.

Could you explain to the person on floor 2 that 0.8 MPa might be based on the air delivery volume of the compressor?

On the 2nd floor is the reduction process for monohydric alcohols; this process uses circulating nitrogen along with hydrogen for reduction, and a low-hydrogen reduction method is employed, with the reduction rate being controlled by regulating the concentration of hydrogen. Currently, this method is widely used in the monolcohol systems of large-scale plants (with air separation)!