Combined operation of low-temperature methanol washing

Water flushing is carried out after the system has been purged and made airtight, but before it is dried and purged with nitrogen； Purpose of water-based operation: (Personal summary, not official) 1. Since water and methanol have similar densities, water is used as a substitute for methanol to simulate the methanol cycle and check whether all system parameters are normal. 2. Check for leaks in the heat exchanger, valves, and pipe flanges ； 3. Test the operation of each pump, such as its flow rate and whether the motor is functioning properly. Since the water is at room temperature while methanol is at a lower temperature after normal production, factors such as temperature need to be taken into account during testing in order to determine whether any abnormalities that occur during water-cooled operation still have an impact after production.

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After that, drain the water completely, fill it with methanol, and the system can be started; with the auxiliary facilities in place, ammonia cooling can be used to start the operation

After draining the water, low-pressure nitrogen must be introduced for drying, to prevent a high water content in the methanol. Once the analysis shows satisfactory results, low-pressure nitrogen is continued to be used for air displacement, to avoid a high oxygen content. Only after everything meets the required standards can methanol be introduced

Hehe, I simplified the question. There will always be dead zones regardless of how water is drained; it is very important to start the thermal regeneration tower. During short-term shutdowns, the regeneration tower is generally not stopped

During the water transportation process, it is necessary to ensure that the temperature in the cold area remains below 50 degrees, and attention should also be paid to regularly cleaning the filters at the inlets of each pump.

① By flushing, dirt, rust, and oil residues in the equipment pipes are removed to prevent product contamination. ② Through water interconnection commissioning, the monitoring instruments for pressure, flow rate, liquid level, temperature, etc., as well as the control and alarm systems are calibrated; the operation of control valves is adjusted. The equipment and pipelines are further flushed, thereby improving the proficiency of operators in their work, and creating favorable conditions for the chemical feeding commissioning. 3. Conditions to be met before system flushing and water commissioning: ① The purging, cleaning, and airtightness testing of equipment and pipelines have been completed, and removed components such as control valves and flow orifice plates have been reinstalled in their original positions. ② All rotating equipment has undergone detailed inspections as required, passed individual tests, and is ready for normal operation. ③ The personnel are ready, there is a comprehensive testing plan, and they are well-versed in the operating procedures. ④ The site is now clean, with all work completed and materials removed. ⑤ The sewerage system is unobstructed, providing proper drainage conditions, and it will not cause the foundation to sink as a result of drainage. ⑥ Low-pressure nitrogen, low-pressure steam, and instrument air are available for use in the boundary zone ； The fire water pipeline network has been established, and other supporting utility systems such as electricity (for power and lighting) and desalinated water are operating properly. ⑦ Appropriate on-site tools such as adjustable wrenches, pliers, F-wrenches, and hoses are available. ⑧ Ensure that all valves in the system are closed, and contact the dispatch team to prepare for testing. 4. Operating and safety precautions ① Exhaust air should be released when each heat exchanger is put into use. ② Once the water circulation is established, open the drain valve on the steam pipeline of the reboiler in the thermal regeneration tower to warm up the pipeline. Once steam begins to flow, slowly open the shut-off valve; it is important to prevent liquid slugging at this stage. If vibrations occur in the pipeline, reduce the steam flow or stop the steam supply. Resume heating once everything is normal, until the water temperature in the system reaches 50°C (be careful not to let the temperature get too high, as this could damage the polyurethane insulation material). ③ The flushing of C2201 and C2202 must be carried out carefully and thoroughly, ensuring that the water discharged from the bottom drain of the tower appears clean when viewed visually ； Start P2205 again to feed water into the methanol-water separation tower C2204; once the liquid level is normal, start FV22024 to heat it to the normal operating temperature, and discharge the liquid repeatedly until it is thoroughly flushed clean. ④ Once the water circulation is established, regularly check the water quality of the system; if there are too many impurities in the water and it is too dirty, trigger a flushing cycle using the drainage water. During the water interconnection commissioning, all drain valves are opened sequentially until the liquid is cleaned up. If necessary, the cycle can be stopped, the water drained, and then operation resumed; the continuous operation period must be no less than 48 hours. ⑤ All pumps are equipped with an automatic control minimum flow backflow device. Once the liquid flow stops, or the flow rate at the pump outlet decreases, the minimum reflux device activates automatically. An isolation valve is installed downstream of the minimum flow control device and is opened during maintenance or standby periods. ⑥ Before starting the pump, it is necessary to exhaust air first; the pump can only be started after a minimum flow rate is established ； During the combined transportation process, special attention should be paid to the pump’s inlet filter and outlet pressure gauge to prevent cavitation. ⑦ Since water has a higher specific gravity than methanol, the outlet should not be fully open while the pump is running, to avoid exceeding the rated current. Keep records of the commissioning process parameters such as pressure, temperature, flow rate, and liquid level. ⑧ When filling the tank, it is essential to vent air to prevent overpressure. ⑨ When establishing the liquid level for combined transportation, pay attention to whether the indication of the central control liquid level gauge matches that of the on-site liquid level meter ； At the end of the combined transportation, all measuring instruments, control valves, and alarm systems must be sensitive and reliable. ⑩ After the water transfer operation is completed, activate the drain lines of various devices, pipelines, and pump inlet and outlet pipes to drain any accumulated water.

Hydro-transport is a trial run when starting up the machine; attention should be paid to the pump head pressure, as water has a higher density than methanol, which may lead to excessive pressure or high current consumption by the pump. Also, the pressure guiding tubes of the instruments should be cleared of any accumulated water to prevent methanol from freezing and damaging the instruments and related components. Another thing is to drain all the water in the dead zone. Pay attention to the pressure difference across various parts of the system, as all the dirt in the system may have accumulated inside the valve filters.