Initial startup of the urea plant

Send the original startup plan for the gas method to see if it can be helpful to the original poster. Original driving plan 4.1. General preparations 4.1.1 Contact the electrical and instrumentation team to check all instruments to ensure they are in good working condition, and that the control valves are functioning properly. 4.1.2 All control valves are in the manually closed position. In particular, it is necessary to verify whether the discharge valve HV201 of the synthesis tower, the discharge valve LV203 of the stripping tower, and the high-pressure vent valve HV202 can be closed properly. 4.1.3 Coordinate with the dispatch team to ensure that all raw materials such as CO2, NH3, cooling water, steam, and process air are available, and that the power supply system is in standby mode. 4.2. Inform all relevant personnel to prepare for the startup inspection. 4.2.1 Currently, startups always take place after major repairs; therefore, it is necessary to ensure that all pipelines are unobstructed. 4.2.2 Check that all valves are in the operating position, and ensure that all flanges that require blind plates or have blind plates removed have been properly inspected. 4.2.3 Have all the equipment been fully repaired after maintenance, and are all bolts installed properly? 4.2.4 Whether the equipment subjected to pressure testing has passed the testing. 4.3. System filling: 4.3.1 Fill the condensate tank 901F; contact the dispatch team to introduce deionized water from outside the boundary area into 901F to fill it to 90% capacity. Start the condensate pump 901J in the pump room, and put the outlet control valve LIC907 of the condensate pump under automatic control. 4.3.2 Fill the low-pressure drum 201F with liquid; fully open the drain control valve PV205 and the shut-off valves located before and after the level control valve LV205 for the low-pressure drum. Open the valve that connects the condensate pump to the boiler feed water pump, and manually operate PV205 and LV205. When the liquid level in the drum reaches 80%, switch the level control valve LIC205 to automatic mode. After the system is put into operation, reduce the setting of LIC205 to 50%. In 4.3.3, fill the medium-pressure steam saturator 903F; open the filling valve for 903F, as well as the isolation valves before and after the medium-pressure steam output control valve PV906/2. Manually open PV906/2 to fill 903F to 20%. 4.3.4 Filling the high-pressure steam saturator 902F: Open the valve for transferring liquid from the medium-pressure steam saturator 903F to the high-pressure steam saturator 902F, as well as the shut-off valves before and after the liquid outlet control valve LV901 of the high-pressure steam saturator. Once the liquid level reaches 20%, close the filling valve for 902F and the shut-off valve LV901. 4.3.5 Fill tank 701F with ammonia solution; open valve 901J leading to the filling valve of 701F, and fill it to 25% capacity. Currently, vehicles generally do not require refilling with liquid, as all substances in the system are drained into the ammonia tank after a long period of inactivity. 4.3.6 Fill urine tank 302F by adding condensate through the inlet pipeline of urine pump 303J using large particles; stop when the liquid level in LI303 reaches 10%. 4.3.7 Charging the high-pressure water system: The pump operator starts the flushing water pump 902J, slightly opens the high-pressure water temperature control valve TV901, fully opens the high-pressure water bypass control valve HV902, opens the valve leading from the high-pressure water to the heater 301ECB at the bottom of the distillation tower, as well as the cut-off valves at the inlet and outlet of the water used for temperature regulation and the bypass valves. The inlet and outlet valves of the high-pressure water pump 903J are slightly opened, and the inert gas vent valves on the shell side of the high-pressure washer 203C and the gas vent valve on the shell side of 301ECB are opened. At the same time, the charging valve for the high-pressure water, connected to the flushing water pump 902J, is opened. Once liquid begins to flow from the vent valves of 301ECB and 203C, these vent valves are closed in sequence. The charging valve for the high-pressure water, connected to the flushing water pump 902J, is then closed partially. After that, the high-pressure water pump 903J is started, and the flow rate of the high-pressure water, indicated by FI905, is adjusted to 150 m3/h. Finally, the cut-off valves at the inlet and outlet of 301ECB are closed. 4.3.8 Low-pressure water filling: Contact the dispatch team; the water treatment unit is responsible for supplying deionized water to the system, while the bypass control valve is used to regulate the flow rate of deionized water going to the power plant. The low-pressure water pump is started just before material discharge, in order to feed deionized water into the low-pressure water system. 4.4. Establishment of the steam system 4.4.1 Establishment of 2.45 MPa steam: Heat up the pipelines for 2.45 MPa steam by opening the low-point drain valves on the high-pressure steam pipelines as well as the high-pressure steam drain valves in front of each steam drum. Raise the temperature of the pipelines gradually to prevent liquid slugging. After the pipeline heating is complete, close all the low-point drain valves, and then slowly open the high-pressure steam valves at 2.45 MPa across the entire system. Open the full-open high-pressure steam release control valve HV901, open the condensate valve of stripper 201C, open the cut-off valve HV901, and open the auxiliary valve of PV904 to introduce a small amount of steam to preheat the shell side of 201C, maintaining it at atmospheric pressure. 4.4.2 Establishment of the 0.8 MPa steam system: 4.4.2.1 High-pressure steam is used to preheat the medium-pressure steam saturator 903F via the auxiliary valve of the medium-pressure steam make-up control valve PV906/1. In 4.4.2.2, preheat the medium-pressure steam saturator 903F to 100°C, fully open the cut-off valves before and after the medium-pressure steam make-up control valve PV906/1, close the bypass valve, manually adjust the pressure of PV906/1 to 0.8 MPa, and then put the pressure control valve PIC906 of the medium-pressure steam saturator under automatic control. 4.4.2.3 Inspect the entire medium-pressure steam system and maintain the liquid level in the medium-pressure steam saturator 903F. 4.4.3 Establishment of the 0.3 MPa steam system 4.4.3.1 Introduce 0.8 MPa steam into the shell side of the high-pressure ammonium methylate condenser 202C, and preheat 202C at a rate of 10–15°C/h to prevent liquid slugging until the temperature T1 001/26 of the low-pressure drum reaches 100°C; then open the trap on the 0.3 MPa steam line. 4.4.3.2 Open the isolation valves before and after the high-pressure steam feed valve for low-pressure steam regulation PV213/2. 4.4.3.3 Manually adjust PV213/2 to introduce steam into the low-pressure drum 201F; use the low-pressure drum vent control valves PV205 and PV213/2 to gradually raise the pressure in the low-pressure drum, PIC213, to 0.3 MPa. After that, switch to automatic control and allow a small amount of steam to be vented through PV205, in order to check the entire 0.3 MPa steam system. 4.3.4 Close the isolation valves before and after the liquid outlet control valve LV903 of the medium-pressure steam saturator. 4.4.4 Establishment of the 0.17 MPa steam system 4.4.4.1 Before opening the low-pressure steam pressure control valve PV907, manually adjust valve PIC907 to 0.17 MPa and then switch to automatic control. 4.5 Feed the steam at each pressure level to the insulated steam bank, open the cut-off valves before and after the drain valve, and close the branch line valve. 4.6 Pass steam into the jacket of the high-pressure water pipeline, while setting TIC901 to 130°C for automatic control. 4.7 Supply instrument water and instrument air. 4.8 Temperature-induced passivation of steam and air. 4.8.1 Preparation work: 4.8.1 Contact the dispatch team to start the carbon dioxide compressor in order to supply air to our workshop for passivation purposes. 4.8.2 Open the main discharge valve on the high-pressure discharge line and the 2-inch drain valve in front of the liquid outlet control valve LV203 of the stripping tower, in order to discharge the condensate generated during the passivation process. 4.8.3 The pressure of the low-pressure drum, PIC213, is controlled at 0.5–1 kgf/cm2. 4.8.4 Open the relief control valve HV202 of the high-pressure washer and the relief control valve HV203 of the gas phase in the synthesis tower, as well as the shut-off valves, the discharge valve and the main valve on the pipeline from 202C to 201D, the discharge valve on the overflow pipe of 201D, and the two discharge valves at the bottom of 203C; do not open the discharge valve at the jet pump to prevent short circuits during passivation. 4.8.5 HV202 fully open, HV203 at 50%, HV201 at 60%. 4.8.2 Passivation at temperatures below 100°C 4.8.2.1 After confirming that HV204 is open, air is fed into the CO2 pipeline to ensure that the pressure remains at least 0.55 MPa. 4.8.2.2 Open the steam valve to 201C to introduce steam into the system. 4.8.2.3 Reduce the pressure of PIC906 to 0.1–0.2 MPa (close the 80VC valve). 4.8.2.4 Pay attention to the pressure of PIC213; keep 002/8 about 5℃ lower than 002/9. 4.8.2.5 Pay attention to the rising rate of 001/4.5.6.7; try to keep the heating rate at 6–8°C/h. 4.8.2.6 The heating rate should be strictly controlled below 100°C. 4.8.2.7 Pay attention to the discharge of cold produced fluid, and try to minimize steam emissions. 4.8.2.8902F remains at atmospheric pressure for preheating. 4.8.2.9 Adjust using HV201 to keep the temperature difference between 001 and 4.7 below 30°C. 4.8.3 Passivation at temperatures above 100°C 4.8.3.1 Reduce the settings of HV203 and HV202 to increase the pressure in 201D; however, the valve position of HV202 should not be set too low, to prevent excessive inert gas from accumulating inside the tower. 4.8.3.2 Gradually increase the pressures of PIC906 and PIC213, but keep 002/8 below 002/9 and 002/6 above 002/5. 4.8.3.3 Gradually reduce HV201 based on the temperature rise at 001/4. 4.8.3.4 When the heating rate is low, gradually increase the pressure of PIC904; in order to ensure condensation of steam at 201°C, 002/9 should be at least 5°C lower than 002/6. 4.8.3.5 The condensate accumulated in 201C can be drained by slightly opening the first shut-off valve before LV203. 4.8.3.6 Due to air pressure limitations, the PIC906 can only be raised to 0.5 MPa; if the temperature rise does not meet the requirements, the air valve can be closed. 4.8.3.7 When 001/4.5.6.7 reaches above 125°C and remains at that temperature for 4 hours, it can be considered that the temperature-induced passivation is successful. 4.8.3.8 If temperature elevation passivation is carried out after the system is discharged, and the wall temperature of the tower is around 100°C at that time, the operation can be conducted by raising the temperature above 100°C. After steam is introduced into the synthesis system, HV203 should remain fully open to displace the inert gas in the synthesis tower for about 20 minutes. 4.8.3.9 When the conditions for starting up are met after passivation is complete, the pump operator stops supplying air to 201C and gradually increases the pressure of PIC213 to 0.55 MPa. Following the pressure increase curve, when the pressure of PIC904 reaches above 1.0 MPa, the inert gas discharge valve on the shell side of 201C is opened; PIC906 is put under automatic control at a pressure of 0.8 MPa, and simultaneously the 80VC valve is opened. 4.8.3.10 If the CO2 compressor is not started at this time, the synthesis system should be kept in a passivated state until it is brought online. 4.9. Pressurization of the synthesis system: After reducing the pressure at PV204 to bring PIC204 to 8.0–10.0 MPa, CO2 is introduced to pressurize the system. 4.9.1 Close all discharge valves and drain valves of the high-pressure system (the discharge valve at the bottom of 203C shall not be closed), and confirm that there is no condensate accumulated in the high-pressure system. 4.9.2 Close the steam valve on the CO2 pipeline. 4.9.3 Adjust the pressure of PIC906 and slowly raise PIC904 to 1.0 MPa. 4.9.4 Start 701J; feed process condensate to 302E via FIC708, while simultaneously starting 704J to fill 302EF, and starting 703J to feed process fluid to 303E. 4.9.5 Maintain the 302EF level using the discharge method. 4.9.6 Start 301J to run in cycle mode. 4.9.7 Shut off HV201, add water to the overflow pipe of 201D to establish a liquid seal, and stop once the system starts discharging. 4.9.8 Slightly open the large CO2 inlet valve to supply CO2 into the system; once the system pressure reaches 2.0 MPa, further open the CO2 inlet valve while ensuring that PV204 remains partially open. The pressure increase should be done gradually – it should take about half an hour to reach 2.0 MPa, after which the pressure should increase by 0.1 MPa per minute. 4.9.9 Open HV203 and increase the flow rate of HV202 to displace the steam in the system. 4.9.10 Increase the pressure release and replacement rate while ensuring that the wall temperature at the bottom of 201D does not drop and that TR 002/1 does not overheat. 4.9.11 When PR201 reaches 8.0 MPa, fully open the CO2 inlet valve; manually close PV204, and allow all CO2 to be vented through HV202 and HV203. Gradually increase PR204 to 10.0 MPa. 4.9.12 During the displacement process, ensure that TIC901 remains above 130°C. 4.10. Preparations before feeding material 4.10.1 Confirm once again that there is no condensate accumulation in 201D. 4.10.2 Add water to the 201D overflow tube using 902J for 15 minutes. 4.10.3 Note: For the 201C liquid level shutdown, use LV203, the shut-off valve before LV203. 4.10.4 Close the bottom discharge valve of 203C and introduce purge steam. 4.10.5 Contact the dispatch to introduce ammonia into the boundary area. 4.10.6 Reduce PIC904 to below 0.8 MPa. 4.10.7 Close the isolation valves before opening PV301 and before and after LV101; slightly open PV301 to preheat 301ECA. 4.10.8 Open the isolation valves before and after PV302, and introduce purge steam to manually fully open PV302. 4.10.9 Check that the pipeline from outlet 103J to 201L, and from outlet 301J to 203C, is unobstructed and clear. 4.11 Driving 4.11.1 Feeding 4.11.1.1 Before feeding, it is necessary to verify once again that the lines from ammonium pump 301J to 203C, as well as the line from the outlet of ammonia pump 103J to 201L, are unobstructed. 4.11.1.2 Close the bottom discharge valve of 302EF and set the ammonium methoxide pump to the main line: low speed. 4.11.1.3 Set HV207 to 50% opening, and simultaneously open the ammonia angle valve. 4.11.1.4 After the temperature drops, start the ammonia pump to feed ammonia into the system. 4.11.1.5 Adjust the frequency converter to keep NH3/CO2 at around 2.9–3.1. 4.11.1.6 Pay attention to the opening degree of HV207 to prevent overpressure in PR201; try to open HV202 as wide as possible. 4.11.1.7 Pay attention to the 302EF liquid level. 4.11.1.8 Keep HV203 open for another half hour to release excess CO2; once a temperature difference appears in TR002/2.3, gradually reduce the flow rate of HV203. After about 15 minutes, shut HV203 completely, and then slowly increase the synthesis pressure to 12.5 MPa. 4.11.1.9 When the temperature difference between TR002/2.3 exceeds 8°C and TIC901 is above 130°C, shut off the steam supply to the high-temperature water jacket and manually reduce the pressure of PIC213 slightly. 4.11.1.10 Notify the pump operator to close the isolation valve before opening LV203, and operate LIC203 in automatic mode at 70-80%. 4.11.2 Before discharge: 4.11.2.1 Once about one and a half hours have passed since NH3 was introduced into the synthesis system, notify the evaporation unit to remove water and create a vacuum. 4.11.2.2 More than 15 minutes before the synthetic display shows the desired liquid level, contact the dispatch team to increase the steam supply; gradually increase the value of PV904 so that the steam flow rate to FR902 is slightly higher than that required for operation at 70% load. The excess steam should be vented through HV901, and the 80VC valve should be closed. 4.11.3 Adjustment after liquid appears in the synthesis tower 4.11.3.1 Close the automatic liquid seal valve and flush the pipeline. 4.11.3.2 Once the liquid level is displayed on the synthesis tower, immediately reduce the flow rate of HV901 and increase that of PV904. While keeping the steam flow rate at FR902 constant, raise the pressure at PIC904 to 1.7 MPa; open the high-pressure water discharge valve 902F and close the high-pressure water discharge valve 902J. 4.11.3.3 When LR201 reaches 50%, gradually increase the opening of HV201 to an appropriate level, keeping LR201 at around 50%. During this process, reduce the opening of HV901 accordingly to maintain a constant pressure at PIC904; set LIC203 at 60–80% and enable automatic control for LIC301 at 20%. 4.11.3.4 After feeding 301ECB, increase the flow rate of HV902 while keeping the high-water flow rate constant; set TIC901 under automatic control at 125–130°C, and open the inlet and outlet valves for high-pressure water to 301ECB as well as the shut-off valve. 4.11.3.5 Adjust PV301 and TIC301 to 132–135°C and put them under automatic control. 4.11.3.6 When a temperature difference occurs in the low-temperature water, reduce the setting of HV903 and increase that of TV902, so that TIC902 reaches 50-55°C and automatic control is activated. 4.11.3.7 Pay attention to the pressure of PIC302; in case of overpressure, increase the opening of the circulating vapor shut-off valve or the vent valve. 4.11.3.8 After the LR201 liquid level stabilizes and the opening degree of HV201 remains essentially constant, put PIC904 under automatic control. 4.11.3.9 After the liquid level in the synthesis tower is displayed, reduce the pressure of PIC213 slightly; once HV201 is opened, quickly lower PIC213 to the value corresponding to the load. 4.11.3.10 After HV201 is opened, the ammonia-to-carbon ratio in the system decreases slightly. 4.11.3.11 When 201C consumes a large amount of steam, pay attention to the pressure of PIC906 to prevent it from overpressuring; if there is urine in 302F during operation, it can be circulated using this urine for evaporation before discharge. 4.11.3.12 Adjust the amount of water and NH3 entering the system in a timely manner, based on the circulation pressure and the concentration of ammonium methoxide solution. 4.11.3.13 Close the 302EF discharge valve and flush it. 4.11.3.14 Use the flash vapor phase to evaporative vapor phase shut-off valve to regulate the flash pressure and maintain TR003/4 at 85-90°C. 4.11.4 Adjustment after the synthesis liquid level stabilizes 4.11.4.1 Once 201C is operating normally, close HV201 to its normal valve position, and adjust the ammonia-to-carbon ratio and water-to-carbon ratio of the system in order to keep the pressure of PR204 between 13.5–14.6 MPa, and the pressure of PR201 between 16.0–16.9 MPa. 4.11.4.2 Analyze the liquid phase composition of 201D in a timely manner; keep the NH3/CO2 ratio at around 3.0, so that the 002/1 ratio is around 183°C. 4.12, Startup via Desorption and Hydrolysis 4.12.1, Open the isolation valves for PV711, FV701, PV709, LV701, LV703, LV706, and TV715; introduce purge steam before PV711, open the valve from 702E to 701F, and close the wastewater discharge valve. 4.12.2: Adjust FV703 to supply NH3.H2O to 701E; manually open FV704 to preheat 701E. Once the level indicated by LIC703 reaches 50%, start 705J. Add water to 703E through LV703, while also opening FV705 to preheat 703E. When the level indicated by LIC706 reaches 50%, open LIC706 to add water to 702E. Once the level indicated by LIC701 reaches 50%… ； LIC701 and LIC703 are respectively put under automatic control. 4.12.3 Manually increase the flow rate of FIC704 and FIC705; use the shut-off valves to heat 702E and 703E respectively, so that the temperature at the bottom of the desorption tower reaches 143°C and the temperature in the hydrolysis tower reaches 200°C. 4.12.4 Set PIC711 and PIC709 to 0.25 MPa and 2.0 MPa respectively for automatic control; manually adjust FIC704 and FIC705 to increase the steam flow into 702E and 703E. Start 707J; when condensation occurs at 708C, manually adjust TV715 and switch it to automatic control at 40°C. 4.12.5 When the liquid level in LIC707 reaches 50%, start 706J, open the valve leading to 301C, and put LIC707 into manual control mode. 4.12.6. Be careful to adjust the amount of ammonia and water fed to 301C in order to maintain the concentration in 302EF. 4.12.7 Manually adjust FIC703 and use FV701 for regulation to maintain the gas phase temperature at 100–115°C. 4.12.8 Once the 702E meets the emission standards, open the wastewater discharge valve and close the valve leading to 701F.