Analysis of the normal startup steps for catalytic units

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Analysis of the normal startup procedures for catalytic units – Section 1: Operation procedures for the reaction-regeneration unit. I. Preparation work: 1. The unit has been overhauled, all systems have been checked and found to be in good condition, and the manholes are sealed. 2. Public utility systems such as water, electricity, gas, and wind are connected to the facility and are in normal operation. 3. All temporary blind plates have been removed, and the permanent blind plates are in their designated positions. 4. The instruments have been calibrated, the interlock functions have been checked and confirmed to be correct, and the special valves have been calibrated. 5. The large and small feeding lines as well as the large discharge line are unobstructed. 6. All pumps are in good standby condition. 7. V22101 is equipped with 300 tons of freshening agent, V22103 has 300 tons of balancing agent available; 4 tons of CO as an oxidizing agent are also on hand. In addition, 8 tons of activator, 10 tons of passivator, 500 Kg of trisodium phosphate, 8 tons of slurry scale inhibitor, 300 Kg of defoamer, 5 tons of anti-gelling agent, 30 tons of fresh alkaline solution, 500 tons of light oil, 3000 tons of light fuel oil, and 2000 tons of liquefied gas are available. 8. The fire-fighting equipment is in good condition, and all personal protective equipment is available. II. Airtightness of the two vessels 1. Contact the unit operator to start the main fan, introduce main air into the two-vessel system, fully open all vent valves as well as the large and small bypass butterfly valves, and purge the two vessels. 2. After purging both devices is complete, close the standby vent; use the large and small bypass butterfly valves to control the pressure at 0.22 MPa in order to conduct a leak test. 3. Promptly fix any leaks that occur during the airtightness test. III. Heating of the two reactors 1. After ensuring airtightness in both reactors, adjust the flow rates of primary and secondary air: set the opening degree of the primary air valve at 5%, and that of the secondary air valve at 30–40%. Prepare the auxiliary combustion furnace at point F2201; use the automatic control system for the large and small bypasses to maintain a pressure of 0.03–0.06 MPa. It is not necessary to supply fluidization air to the external heat exchanger or the bottom of the raw catalyst sleeve for now. 2. Strictly follow the operating procedure for point F22101 (raise the temperature in accordance with the heating curve of the dryer); control the rate of temperature increase at 20–30°C/h. When the outlet temperature TI22164 exceeds 350°C, the fuel oil nozzle can be activated. However, when the furnace temperature TIA22160 is 950°C or less and the outlet temperature TI22164 is 600°C or less, the main air flow should be controlled at around 2400 Nm3/min. 3. During the temperature rise process, the regeneration slide valve TV22101AB should be opened to 50%, the bypass pipe slide valve TV22101C should be opened to 20%, and the self-circulation slide valve TV22101D should also be opened to 20%. The regeneration plug valve WV22101 should be opened to 80%. In addition, each slide valve must be moved every half hour, and care must be taken to avoid fluctuations in regeneration pressure during such movements. 4. The system undergoes isothermal thermal tightening at regenerator temperatures of 150°C, 250°C, 350°C, and 550°C. 5. When the regenerator temperature reaches 350°C, attempt to pass loose steam, atomizing steam, anti-coking steam, and slide valve passage purge steam; once smooth flow is confirmed, shut them off. IV. Removal of blind flanges SB22201/SB22205: 1. Slowly close the regeneration slide valves TV22101A/B and the regenerator plug valves to disconnect the two vessels. At the same time, fully open the vent valves and drain valves located at the top of the reaction settler, as well as at the tops of the two large oil and gas lines, in front of the blind flanges SB22201/SB22205. Also open the drain valve at the bottom of the riser. When disconnecting the two vessels, do so slowly to prevent an increase in pressure in the regenerator, which could cause furnace shutdown in F22101 or overheating of the furnace. Cut off all steam to the reactor and prepare to remove the blind flanges SB22201/SB22205. 2. Turn off the stirring steam in the fractionation towers T22201A/B completely; supply a small amount of N2 to the tops of V22203A/B to maintain a slight positive pressure in the T22201A/B systems, and then begin to remove the blind flanges SB22201/SB22205 under heat. 3. After completing the removal of the blind flanges, close the vent and drain valves located before the blind flanges SB22201/SB22205, as well as the drain at the bottom of the lift pipe. Fully open the stirring steam in the fractionation towers T22201A/B to drive out air; vent the heavy oil vapor lines and light oil vapor lines at the top of the reaction settler. Once steam is observed coming from the vents on these larger vapor lines, turn off the stirring steam at the bottom of the main and auxiliary fractionation towers, and then use steam in the reactor to drive out any remaining air. 4. When expelling air, open all the steam valves on the reactor fully; other types of steam such as the pre-heating steam should not be opened to full capacity, but the amount of stripping steam should be increased as much as possible (a bypass for the control valve can be used if necessary). 5. Once steam is observed in the vent at the top of the reactor, contact the distillation team to adjust the process flow; simultaneously, close the vents at the top of the settler and the main oil and gas line. The reaction pressure should then be controlled at 0.1 MPa by using the flare at the inlet of the air compressor. V. Catalyst installation and replacement 1. Start the booster pump according to the operating procedures; change the flow of air used for fluidizing the sleeve and the external heat exchanger to air intended for boosting, with the flow rates set at 50 Nm3/min and 50 Nm3/min respectively. 2. Supply backblowing air and loosening air to each inclined tube and each cone. 3. Turn on the air supply for the catalyst feeding line; the pressure should be 0.05 MPa higher than that in the regenerator. Start feeding the equilibrium catalyst at a fast rate (keep the pressure in the feeding line about 0.15 MPa higher than before feeding) to seal the material leg as quickly as possible. 4. When the regenerator inventory is 30T, it has already overflowed the combustion oil nozzle; reduce or suspend feeding, raise the temperature to 390°C, and attempt to spray combustion oil. After ignition, raise the temperature to 450°C and increase or resume feeding. However, as long as the temperature remains ≤450°C, F22101 can be used to gradually reduce the flame until the furnace is shut down, while fully opening the primary and secondary air valves. 5. When the regenerator inventory is 50 T, catalyst transfer is carried out, with the pre-lift steam volume for the heavy oil lift pipe set at 0.6 T/h, the stripping steam volume at 4.8 T/h, the steam volume for raw material atomization at 12 T/h, the steam volume for light oil feeding in the light oil lift pipe at 0.6 T/h, the start-up steam volume at 1.0 T/h, and the fluidization steam volume at 0.3 T/h. When the inventory in the settler reaches 15T, gradually open the raw catalyst plug valve to establish fluidization in both vessels. 6. Continue large-scale feeding to maintain a reserve of 60T in the regenerator and 40T in the settler; stop large-scale feeding and switch to small-scale feeding with fresh catalyst. During this period, increase the amount of combustion oil injected into the regenerator in order to keep the temperature in the heavy oil lift pipe at 550°C and the temperature in the light oil lift pipe at 570°C, thereby preparing for feeding into the lift pipes. VI. Reaction injection: 1. Maintain a negative differential pressure of 0.03–0.05 MPa between the two reactors, with the temperature of the feed oil ranging from 200 to 250°C. 2. Open the feed oil nozzle at a pressure of 0.8 MPa, and gradually increase the feed rate based on the temperature at the outlet of the heavy oil lift pipe. 3. After feeding the reactant, combustion oil injection into R22102 should be stopped as soon as possible, so that it is possible to resume combustion oil injection at any time. 4. To prevent secondary combustion, 20–30 Kg of oxidizer is added before fuel injection; after injection, close attention should be paid to the temperature of the dilute and dense phases, and oxidizer must be added promptly if a large temperature difference occurs. 5. After oil injection, appropriately adjust the external heat-fluidized air to control the regenerator temperature and ensure it does not exceed the allowable level. As feed is supplied through the nozzles, correspondingly shut down the emergency bypass line and the emergency steam line, and reduce the temperature of the preheating line for the crude oil nozzles. 6. Once the feeding to the heavy oil lift pipe is operating normally, the liquid level in the vapor-liquid separator at the top of the heavy oil distillation tower rises; at this point feeding to the light oil lift pipe can begin, with attention being paid to controlling the pressure in the settler during feeding. VII. Operations after fuel injection 1. The reaction temperature affects the degree of reaction; under normal conditions, the temperature at the outlet of the heavy oil lift pipe should be maintained at 520°C. If it drops below 460°C, an interlock system will automatically shut off the feed oil and activate the emergency steam for the lift pipe ； The outlet temperature of the light oil lift pipe is controlled at 550°C. 2. The pressure difference between the two vessels should be maintained between -0.03 and -0.05 MPa; otherwise, the catalyst may flow in the reverse direction and the fluidizing media may mix with each other, leading to equipment damage or explosion. When the pressure difference reaches? ? ? At MPa, the interlock shuts off the feed of crude oil; when the pressure difference reaches? ? ? At MPa, the interlock shuts off the feed of crude oil and the circulation between the two vessels. 3. The regenerator outlet temperature is one of the key parameters reflecting the thermal balance between the two reactors, and it should be controlled at 690–710°C. 4. The valve opening shall not exceed 50%. 5. The residual oxygen level in the regenerator should be maintained between 3% and 5%; too high a level can lead to afterburning, while too low a level reduces the effectiveness of combustion. 6. The stripping steam flow rate is 4.8 T/h. 7. If the catalyst to be regenerated is severely contaminated with oil, the oxygen level in the regenerator, indicated by AR22504, will drop rapidly to zero, and yellow smoke will emanate from the chimney; in such cases, it is necessary to stop the feed of crude oil or significantly reduce its flow rate. 8. The carbon content in the regenerated catalyst has a significant impact on its activity; the control limit is: <0.1% (W). 9. The oxygen content in the flue gas rises and then falls again; when the temperature difference between the dilute and dense phases is greater than 20°C, it can be concluded that secondary combustion has occurred, and it is necessary to add CO as a combustion aid to the system. 10. The reaction feed rate is controlled at around 100 T/h; once the quality of each product meets the standards, the feed rate is adjusted to full capacity in accordance with the company’s instructions. Appendix: Operating Procedures for the Auxiliary Combustion Furnace (F22101) I. Characteristics This furnace is a positive-pressure type; it has a small furnace chamber and a large volume of primary air supplied to it. As a result, it is not easy to ignite, but it can also be extinguished easily, so special care must be taken when starting the furnace. II. Preparation Work 1. Contact the instrumentation team to check whether the thermocouples located in the furnace chamber, at the furnace outlet, under the distribution plate, and at the outlet of the coking tank are properly installed, and to carry out calibration. 2. Check whether the equipment and components are complete. 3. Check that the electric igniters are complete and in good working condition. 4. Check whether the gas and oil burners are installed correctly, and whether the switches function properly. 5. Install pressure gauges on the gas line, oil line, steam line, and air line. 6. Check whether gas or oil is being supplied to the furnace for dehydration. 7. Check whether the gas heater is unobstructed. 8. Check the installation status and opening degree of the blinds, and make corresponding markings. III. Operational Precautions 1. Replace the fuel gas pipeline and drain out air and water residues. And control the oxygen content to ≤1%. Install a gas heater. 2. The primary air valve should be almost completely closed (with an opening degree of around 5%); otherwise, it is easy to extinguish the small flames, and the regeneration pressure can be kept at a minimum (between 0.03 and 0.05 MPa). 3. The secondary air damper should be opened to a certain degree, so that the secondary air flow rate remains between 600 and 700 Nm³/min. 4. When attempting to ignite, supply power for ignition; when the spark is strong, reduce the air supply and increase the gas supply. If ignition does not occur, adjust the ratio between the two as much as possible. 5. Closely observe the furnace burner during ignition. Once lit, maintain or increase the gas supply to prevent it from going out. If the gas does not ignite on the first attempt, the gas must be turned off and air flow must be increased to purge the furnace for a few minutes. Blow out the gas to prevent accidents during the next ignition. Electric ignition can be used for a few seconds at a time; continuous power supply can easily cause damage. 6. After ignition, the air supply should be increased slightly promptly, and the amount of gas supplied should also be increased accordingly. Meanwhile, observe the rate at which the furnace temperature rises and the color of the flame, as well as the color of the smoke, in order to adjust the proportion of air supply and ensure complete combustion without any black smoke, while also preventing the flame from being extinguished. The temperature increase must follow the specified heating curve. 7. When heating with gas until the burner is operating at full load, if the temperature rise is insufficient, switch to a combustion oil with a higher heating capacity. Such as extinguishing a fire after oil has been burned. Extra attention is needed. Immediately close the oil valve and inspect the bottom of the furnace; if there is oil remaining, it must be drained promptly and the area purged. Otherwise, it is prone to vaporize at high temperatures and cause an explosion; the temperature rises until it reaches 550°C at the distributor plate. At this point, the furnace temperature is adjusted by the ratio of primary to secondary air to keep it below 950°C. 8. If both the oil flame and the gas flame go out, the gas flame should be lit first; it is strictly prohibited to ignite by directly spraying oil. IV. Steps and requirements for switching from oil to gas combustion: When the gas burners are fully open and the furnace temperature can no longer increase, it is time to prepare to switch to using oil burners for combustion. 1. Before ignition, it is necessary to maintain stable oil pressure; a dedicated person must be assigned to monitor this, and the fuel oil pump should adjust the pressure as needed. When replacing the burner nozzles, condensation must be removed from both the combustion oil and steam lines in front of the nozzles. 2. First, use steam to purge the oil burner, then use a small amount of it for atomization; do not extinguish the gas flame. 3. Slowly open the fuel oil valve until ignition occurs; maintain a stable steam pressure, which should be 0.15–0.2 MPa higher than the pressure of the burning oil, and then gradually increase the opening of the burning oil valve ； Turn down the gas valve, but do not turn off the gas burner, so it can be lit as soon as the oil burner goes out. 4. Adjust the flame based on the furnace and distributor plate temperatures to control the fuel volume. Section 2: Startup Procedures for the Fractionation Unit I. N2 airtightness testing and purging 1. Introduce N2 from the tops of V22203A/B into T22201A/B to pressurize it to 0.2 MPa; connect temporary N2 lines to the re-refining and feed oil systems respectively, or connect them to T22201A/B as well, and pressurize them to 0.2 MPa to ensure airtightness. 2. After passing the airtightness test, the distillation system is held at pressure (0.2 MPa) for 24 hours. 3. The fractionation system was purged with N2; after multiple cycles of filling and venting, multi-point sampling showed that O2 levels were below 0.5%, meeting the requirements. II. Establishing a circulation by introducing fuel 1. Introduce light fuel oil: Light fuel oil is introduced into V22204 via the catalytic light fuel oil discharge line P22238 until the level reaches 80%; then V22204 is stopped and the water is separated. Pipeline P22238→FV22232→FO22100-2→V22204. 2. Introduce light oil: (1) From the line for unqualified light oil, introduce light oil into V22203A/B to achieve a liquid level of 60%. Pipelines: P22222→P22222/2→P22221→V22203A; P22222→P22209→P22209/2→P22202/2→V22203B. (2) Fill the top condenser return stream of the heavy oil distillation tower with light oil until oil is observed before valve FV22204 ； Light oil is fed into the top cooling reflux of the light oil fractionator to FV22212; oil is observed in the drain. 3. Introduce crude oil to establish an open-loop circulation in the crude oil, secondary intermediate, and slurry systems. (1) Put all water coolers in the system into operation; the use of tower top air coolers shall be determined based on actual conditions. (2) Establish the open-loop circulation path: →E22222AD→E22223→V3101AB→P3101AB→LV22209→V22201→P22201AB→E22201AB→E22211AB→V22205←E22225←P22213AB←Pipeline P22128←FV22215←E22224AB (shell)←E22202AB←E22212AB←E22215B←FV22225←→E22224AB (tube)→MI22101→XOV22102→V22202→P22208AB←E22215A←E22202←P22209AB←→Bypass of E22214 (TV22205)→Pipeline P22276/2←FV22207←→TV22202B→FV22208→Pipeline P22291→Pipeline P22291/2→E22213AB→Slurry storage area→Pipeline P22291/3→E22213CD. (3) Initially maintain a small amount of feed from the tank area; drain water by backflowing at each control valve along the way and at the pump outlet low points, and stop feeding once oil is detected. (4) Gradually introduce heating steam at 1.0 MPa to E22215B; increase the circulation rate of the feed oil to 100 T/h, and raise the temperature to around 140°C. (5) The electrodialysis section is not in use for the time being. (6) After 8 hours of operation in open-loop mode, if the water content analyzed from the samples taken at the P22201 inlet, the second stage, and the slurry is less than 1%, it is possible to switch back to the closed-loop refining mode, with the slurry being discharged at a flow rate of around 100 T/h. An open-circuit cycle can also be maintained, followed by further temperature increase. 4. Establish a large closed-loop circulation: heating and tightening → E22222AD → E22223 → V3101AB → P3101AB → LV22209 → V22201 → P22201AB → E22201AB → E22211AB → V22205 ← E22225 ← P22213AB ← Pipeline P22128 ← FV22215 ← E22224AB (shell) ← E22202AB ← E22212AB ← E22215B ← FV22225 ← → E22224AB (tube) → MI22101 → XOV22102 → V22202 → P22208AB ← E22215A ← E22202 ← P22209AB ← → Bypass for E22214 (TV22205) → Pipeline P22276/2 ← FV22207 ← → TV22202B → FV22208 → Pipeline P22291 → Pipeline P22291/2 → E22213AB → Pipeline P22116 → P22201AB → Pipeline P22291/3 → E22213CD. (1) Increase the amount of heating steam supplied to E22215B, and control the liquid levels in V22201 and V22202 to be below 40%, in order to prevent vacuum conditions from occurring in P22208 and P22209 when the raw materials are heated. (2) After keeping the crude oil at the outlet of E22215B at a temperature of over 200°C for 2 hours, the system becomes hot and tight; preparation is then made to remove the blind flanges SB22201/SB22205. III. Removal of blind flanges SB22201/SB22205 to connect the reaction distillation system: 1. Open the vent at the top of the main and auxiliary distillation towers, as well as the bottom drain valves for condensate removal and pressure relief. 2. Adjust the amount of stirring steam at the bottom of the tower and the nitrogen flow from V22203AB to maintain a slight positive pressure in the distillation tower; coordinate with the maintenance team to remove the blind flanges SB22201/SB22205. 3. After removing the blind plates SB22201/SB22205, increase the steam supply to the bottom of T22201AB and close the vent at the top of the tower. Vent the heavy oil vapor line and the light oil vapor line at the top of the reaction settler respectively. 4. After the blind plate is removed, cut off the water supply to V22203AB promptly, but oil leakage must be strictly prevented. IV. Feed oil into T22201AB to establish circulation in the main and auxiliary fractionation towers. 1. Increase the discharge from the bottom vent of T22201A to remove all condensate; vapor should be visible in large quantities. (1) When the bottom temperature of T22201A is >200°C, shut down P22209, slowly open the bottom extraction valve of T22201A to allow oil to flow back under static pressure; close it once oil is observed in the tower bottom vent. (2) When the level of T22201A is 50%, close the inlet bypass valves for P22208 and P22209; P22209 shall then be used to draw oil from the bottom of the tower. (3) Establish self-circulation of the slurry; the level of T22201A is controlled by the amount of oil returning from reprocessing and the amount discharged externally. (4) Before fuel injection, the secondary stream need not be circulated into the tower. (5) Open the re-refining oil and light fuel distillation valves, as well as the first extraction valve separately (the top circulation extraction valve shall not be opened for now). 2. Open the bottom drain of T22201B to fully drain the condensate; a large amount of steam must be visible. (1) When the bottom temperature of T22201B is greater than 200°C, slowly open the manual valve for feeding crude oil into T22201B. When the liquid level in T22201B reaches 50%, gradually open the bottom extraction valve of T22201B and close the cross-line manual valve; P22213 should then draw from T22201B. (2) Establish self-circulation at the bottom of tower T22201B; the liquid level in T22201B is controlled by the amount of feed oil entering the tower. (3) Open the light fuel distillate valve and the intermediate extraction valve separately (the top circulation extraction valve shall not be opened for now). 3. Strengthen water cutting at the inlet drain of each section of the recirculation pump for T22201AB. V. Reaction oil injection and establishment of reflux streams in the distillation process (I) Oil injection into the heavy oil riser 1. Start the cold reflux; strictly control the top temperature TRC22201 to be ≤110°C, and open the top circulation extraction valve to establish the top reflux as quickly as possible. 2. Adjust the amount of oil slurry returning to the tower to keep the bottom temperature of the tower at ≤350°C. However, the amounts of material returning to and from the tower should be kept as low as possible; adjust the amount of reprocessed oil returning to the tower in order to control the liquid level in vessel T22201A. 3. The reflux from Unit 2 is directed back into the tower to establish a circulation; at the same time, the closed-loop circulation is stopped. Steam is supplied from the outlet of E-211 to purge V-202, but care should be taken to ensure that the amount of steam supplied is not too large. 4. Once a certain liquid level is reached in T22202, the draw-off valve for T22202 is opened, P22206 is activated along with the inlet line to P22207; simultaneously, P22207 is started up to establish a circulation. When the gas-phase load in the middle section is low, it is possible to reduce the amount of slurry returning to the tower as well as the amount returning to the second middle section, thereby helping to establish a reflux flow in the first middle section. 5. Once the light fuel extraction is operating normally, supply stripping steam to T22202. 6. As the feed rate increases, adjust the heat extraction from stages 1 and 2 as well as from the oil slurry reflux to ensure uniform heat extraction in the middle and lower sections of the distillation tower. 7. Adjust the amount of slurry recycled to maintain a solid content in the slurry of ≤6 g/l; activate the small external discharge system for the slurry based on its properties. 8. Adjust each reflux to properly control the temperature and liquid level at various points, ensuring that the product quality and process parameters meet the specified requirements. 9. According to the changes in the preheating temperature of the feed oil, gradually reduce the amount of heating steam supplied to E22215B until it is completely shut off. Stop feeding feed oil into E22215B and instead feed slurry into it; E22215B will then produce 3.5 MPa steam by utilizing the residual heat from the slurry. 10. Operate T22303 in conjunction with the absorption and stabilization system. Section 3: Startup Procedures for the Absorption and Stabilization Unit I. Airtightness Testing 1. The absorption and stabilization unit is pressurized to 1.0 MPa using an air compressor for airtightness testing; once this test is successful, nitrogen is used for purging. Samples are taken at multiple points, and the test is considered successful when the oxygen content is less than 0.5%. 2. For the airtightness test of the light oil desulfurization unit, the gas emitted after the airtightness test of the absorption and stabilization system is used to pressurize the system to 0.3 MPa; once this is achieved, nitrogen is injected into R26101AB for displacement, and multiple samples are taken until the O2 content is below 0.5%, at which point it is considered satisfactory. 3. The T26201, 26202, and 26301 systems supply cooking steam to the bottom of the upper tower, pressurizing it to 1.0 MPa for airtightness. 4. After the gas desulfurization section meets the airtightness requirements, N2 is filled into vessels V26201 and 26202; temporary nitrogen is used for displacement through the drain lines LV22511, 22514, and 22517/2. Sampling at multiple points is conducted until the O2 content is below 0.5%, at which point it is considered satisfactory. II. Introduce nitrogen for pressurization, enable absorption and stabilization; carry out light oil three-tank circulation; add alkali to the light oil refining system, and ensure solvent circulation in the desulfurization system. 1. Introduce nitrogen for pressurization: (1) Introduce N2 into the absorption and stabilization system to achieve a pressure of 0.5 MPa. (2) The process for introducing light oil is as follows: from pipeline P22222 → pipeline P22221 → FV22218 → T22301 → V22302 → P22301A/B → FV22306 → T22302 → P22305 → FV22307 → E22307 → T22304. The liquid levels of V22302, T22301, T22302, and T22304 should be maintained at 60%. (3) Establish a three-tower cycle; the process is as follows: T22301 → V22302 → P22301A/B → T22302 → P22305 → T22304 → P22307 ↑ │ 2. Alkali addition to the light oil refining system (1) V26103 receives fresh alkali; water is added to adjust the concentration of the alkali solution to 10%, and the alkali solution is then added to V26101 until the upper level is reached. (2) Keep the light oil refining system at a slight positive pressure, ensure the entire process is operational, and prepare for material receipt. (3) The levels of the activator and anti-gelling agent tanks have both reached the required levels, satisfying the conditions for filling the system. 3. Solvent circulation in the dry gas and liquefied gas desulfurization system: (1) Charge T26201 and T26202 to 0.5 MPa; contact the solvent regeneration unit V23602 to prepare a desulfurizing agent solution with a concentration of 20–30%; then use N2 to pressurize T23601 to 60–80 KPa. (2) Contact the solvent regeneration unit to establish a three-tank solvent circulation; the process is as follows: V23602 → P23602AB → T26201 → E23601 → V23601 ↑ │ ↑ │ Where: FRC22508 controls 24 t/h │ └─→ T26202 ──┘ │ FRC22511 controls 38 t/h └───E23602AB←E23601←T23601 ← ┘ 4. Alkali solution circulation in the liquefied gas desulfurization system (1) T26301, V26302, and V26304 are pressurized together to 0.5 MPa when T26201 is pressurized. Pressurize V26303 to 0.2 MPa and add the catalyst alkaline solution. (2) Establish a catalyst alkali solution circulation; the process is as follows: V26303 → E26302 → P26301 → FI26301 → T26301 ↑ │ Where: FRC22518 controls the flow at 20 t/h. └ T26302 ← E26301 ← LV22517/2 ← T26301 ← ┘ III. Receiving rich gas and crude light oil 1. Absorption and stabilization (1) As distillation operations progress, a circulation system is established in Tower 1; low-pressure steam is supplied via E22306, and heat is provided from Tower 1 via E22310. The temperature is increased gradually to maintain proper circulation in the three towers. Rich gas and crude light oil can be introduced only when there is sufficient heat supply in the desorption tower and the stabilization tower. (2) As the feed amount increases, the qualified crude light oil is upgraded to T22301. (3) Close the pressure compressor flare valve; control the pressure increase at a rate of 0.1 MPa per 10–15 minutes. Activate the air-cooled units E22301A/D in a timely manner to establish two intermediate reflux streams in T22301, and inject water into the rich gas as appropriate. V22302 should be used to remove water promptly, keeping the wastewater level at 30–40%. The pressures in T22301 and T22303 are controlled by PV22301. (4) Use PV22303A/B at the top of tower T22304 to control the pressure at 1.05 MPa; keep the non-condensable gas valves fully closed in order to establish a liquid level in V22303 as quickly as possible. When the liquid level in V22303 reaches 30%, activate P22306 to send reflux to T22304. (5) Use PV22302 to control the pressure of T22302 at 1.2 MPa; the deethanized light oil should be transferred to T22304 via pressure as appropriate. 2. Desulfurization system: (1) Introduce liquid hydrocarbons into T26201; the concentration of LRCA22510 is around 18%. After amine washing, the liquid hydrocarbons go into V26301 for pre-alkaline washing, and then into T26301 to remove thiol compounds. Keep PRC22506 at 1.2 MPa, and send the mixture to the tank area. (2) The dry gas from T22303 is sent to T26202 for amine washing; PRC22512 is controlled at 1.2 MPa and LRCA22514 at 50%. The dry gas after amine washing is sent to the fuel gas network and reaction units as pre-heated dry gas. 3. Light oil refining: (1) To stabilize the light oil, it first passes through an alkaline washing process, then through R26101 for desulfurization and alcohol removal; subsequently, it goes through T26101 to have impurities such as alkali mist and moisture further removed. The pressure in V26102 is controlled at 0.25 MPa by PRC22501. The refined light oil is finally discharged through P26101. (2) Start P26104A and P26105; the amount of anti-adhesive injected shall be 5.0 L/h ； The dosage of the activator is controlled at 8.0 L/h. Chapter 5: Procedures for Normal Shutdown of the Unit Section 1: Shutdown Procedures for the Reaction-Regeneration Unit I. Cut off feed to the reaction unit and stop the rich gas compressor. 1. The heavy oil lift pipe reduces the amount of fresh feed oil at a rate of 10 T/h, while the light oil lift pipe reduces the light oil feed at the same rate. Meanwhile, coordination is carried out with the oil storage area to decrease the amount of feed oil supplied, in order to keep the level in V22201AB at 20%. 2. Slowly close the butterfly valve at the flue gas extractor inlet, and fully close the gate valve at the same inlet; the regeneration pressure is controlled by the butterfly valve in the flue gas extractor bypass. 3. The feed rate to the reactor should be steady, ensuring that the temperature at the outlet of the coking tank is ≤660°C; if the temperature is too low, combustion oil can be injected to maintain the reaction temperature around 510°C. 4. As the reaction load decreases, the heat removed by the external heat exchangers, the oil slurry, the bottom oil of the tower, and the second heat exchanger gradually decreases; accordingly, the steam generation rate of the operating boilers is increased step by step to maintain a stable steam pressure in the system. 5. When the heavy oil feed rate drops to 50 T/h, first shut off the light oil lift pipe feed, then activate the interlock for the heavy oil lift pipe feed to cut off the feed; the crude oil is then routed through the emergency bypass line to V22202. Cut off the re-refining process and close the feed nozzle for crude oil. 6. Stop feeding to the reactor; after 2 hours of cyclic coking in the two vessels, burn oil is injected into the regenerator to keep the system’s temperature drop rate below 30°C/h. 7. After the feed to the reaction is stopped, the reaction pressure is controlled by the large and small flare valves at the inlet of the rich gas compressor; at this time, it is necessary to maintain a proper pressure balance between the two vessels in order to avoid excessive pressure fluctuations. II. Transferring and Unloading the Catalyst 1. Stop feeding to the reaction vessel, and activate the large-scale unloading line of the coking tank to begin unloading the catalyst. Keep the unloading temperature at ≤450°C, and pay close attention to the heating conditions of the pipelines and the catalyst tank during the unloading process. 2. When the outlet temperature of the lift pipe is below 480°C, catalyst transfer can be carried out. A positive pressure difference should be maintained (regenerator pressure at 100 KPa, reactor pressure at 120 KPa). First, close the two regeneration slide valves manually on-site, in order to transfer the catalyst inside the reactor to the regenerator. When the inventory and density in the reactor return to zero, and the pressure drop in the stripping section of the settler as well as the pressure drop across the catalyst plug valve also return to zero, it indicates that all the catalyst has been removed from the reactor and the catalyst lift pipe. At this point, the catalyst plug valve should be closed (by manual operation on site) to disconnect the two vessels. 3. Increase the steam supply to the reactive settler to drive away oil and gas; once the catalyst has been completely removed, turn off the atomization steam and anti-coking steam, while keeping the pre-lift steam and stripping steam in use. Notify the fractionation unit that it is possible to stop the slurry circulation. 4. After all the catalyst has been transferred to the regenerator, adjust the main air volume to maintain the volume and density in the regenerator, thereby facilitating the removal of the catalyst. 5. The external heat exchanger catalyst is discharged through the discharge line at the bottom of the external heat exchanger. 6. Once the catalyst in the two-tank system has been completely removed, stop the rich gas compressor. Activate the bottom discharge line of V22105 to discharge the catalyst from the three-spin system. III. Purge the two vessels, stop the main fan, and install blind flanges SB22201/22205. 1. Divert the main steam away from the regenerator; fully open the vents at the top of the reactor, in front of the blind flanges SB22201/22205, and at the bottom of the lift pipe. Stop all steam supplied to the reactor, and work together with the distillation team to install the blind flanges SB22201/22205. 2. After the blind plates SB22201/22205 are installed, steam for stripping and pre-raising is supplied to the reactor; after 12 hours of purging, all steam supply is stopped. 3. After the catalysts in both units have been completely removed, main air is introduced into the regenerator for purging; the large and small bypasses are opened fully, and the exhaust is released through the chimney. When the temperature at the outlet of the regenerator drops to 200°C, contact the unit to shut down the main fan. 4. After the main fan is shut down, turn off all the backflow and loosening air (steam) used in the reverse-regeneration system, and close the main valve for non-purified air entering the two reactors. 5. Contact the maintenance unit to open manholes and carry out cooling. IV. Shutdown procedures for the waste heat boiler system: 1. As the reaction rate decreases and the heat demand drops, it is necessary to adjust the water supply to V22401 in a timely manner to ensure that the liquid level in V22401 remains above 50%. 2. As the flue gas temperature decreases, the amount of flue gas fed into B22401 should be gradually reduced, while the amount of flue gas discharged through the chimney should be increased. 3. Increase the drainage volume of the steam-water separator in the external heat exchanger as appropriate. 4. When the temperature in the middle section of the external heat exchanger drops to 150°C, stop feeding water to V22401 and shut down the external heat water circulation system. When the temperature of the E22205AB slurry is below 250°C, stop feeding water to V22402; simultaneously, water feeding to V22403 and V22404 can also be stopped. 5. V22401. 22402, 22403, 22404: Steam venting, with gradual pressure reduction. 6. The boiler feed pump P22402AB continues to supply water to the operating boilers, maintaining steam supply for the units that are shut down. Section 2: Shutdown Procedures for the Fractionation Unit 1. Oil removal from fractionation unit and installation of blind flanges SB22201/22205 (1) As the reaction rate decreases, the electrodesalination system stops injecting water, and the demulsifier is no longer added ； Adjust the flow rates accordingly to ensure product quality meets standards and prevent the pump from running dry. (2) As the feed oil loading volume decreases, maintain a low level of V22201 at 20%, after the feed oil feeding is stopped. Close the manual valve on the wall of vessel V22201 for the feed oil, and contact the tank farm to purge the feed oil pipeline in front of the valve with steam. (3) Fully open the inlet and outlet manual valves for cooling water at E22213AD; increase the amount of slurry discharged outside, keep the discharge temperature at ≤95℃, maintain the level of T22201A at 25%, and also keep the levels of V22201 and V22202 between 20% and 30% in order to reduce the oil recovery time. (4) After stopping the feed to the reaction, increase the flow rate of FC22215 to transfer the material in V22201 to T22201B and remove it from the plant, until P22201 is emptied. In T22201B, the oil at the bottom of the tower is kept in circulation; when the liquid level is high, the amount of fluid that enters V22202 through the emergency bypass line is controlled, until all the catalyst in the reaction settler has been transferred to the regenerator. (5) For the reprocessing of V22202, the fluid from FC22207 is returned to T22201A via the second intermediate stream, and FC22207 operates at maximum flow rate until P22208 is evacuated; meanwhile, V22403 stops supplying water. ┌─→ E22214 → FV22207 ┐ V22202→P22208→─┤ ├→T22201A └─→FV22202 ───────┘ (6) When the bottom temperature of T22201AB is <250°C, V22402/4 stops supplying water. (7) Close the light fuel and reprocessed oil distillation valves; shut down after evacuating P22206. (8) After stopping the feed, stop the cooling reflux as appropriate. The stirring steam at the bottom of the distillation tower and the stripping steam in the light fuel oil stripper remain operational. (9) Depending on the reaction converter conditions and the bottom temperature of the fractionation tower, stop the slurry circulation and bottom oil circulation at the appropriate time. (10) All the bottom oil from T22201B was transferred to T22201A; P22213 was evacuated and taken out of service ； Drain the bottom slurry from tower T22201A and shut down P22209. 2. Fractionation system purging: (1) Feed oil is introduced into the line to purge the tank area. In front of the inlet manual valve of V22201 ──→ LV22209 → intermediate tank area ↑ Steam. (2) After P22201 is evacuated repeatedly, the entire system filled with crude oil is purged. LS → E22222AD → E22223 → after the extraction valve of V22201 → P22201AB → E22201AB → E22211AB → V22205 ← E22225 ← P22213AB ← pipeline P22128 ← FV22215 ← E22224AB (shell) ← E22202AB ← E22212AB → E22224AB (tube) → MI22101 → XOV22102 → pipeline P22102 → pipeline P22260/1 → pipeline P22260/2. Outlet/inlet ← pipeline P22294 ← pipeline P22116 ← (3) Crude light oil reprocessing and quench oil section. Before shutting off the feed to the heavy oil lift pipe and the light oil lift pipe, first stop the feed of crude and light oil for reprocessing as well as the feed of quench oil, and transfer the material in the pipelines into the lift pipes. (4) It is best to start sweeping the line on the startup cycle at this time, in order to avoid repeated oil inflow into V22202; steam should be supplied from E22213 and FV22208, and the oil should be swept into V22202. LS → Pipeline P22116 → Pipeline P22276/5 → V22202; LS → Pipeline P22276/2 → Pipeline P22276/5. (5) Top circulation system for the main and auxiliary distillation columns: Nitrogen is used to initiate oil circulation at the top, and nitrogen supply is stopped once oil flow is confirmed to be absent in FV22205/22213. Layer 4 of T22201A ─┬─→P22204→E22201AB→E22206AF→Layer 1 of T22201A | │ ↑ N2 └ TV22201─┘ Layer 4 of T22201B ─┬─→P22205→E22222AD→E22221AB→Layer 1 of T22201B | │ ↑ N2 └ TV22222─┘ (6) Middle return system, intermediate return system: Stop the circulation of hot water in E22217 and drain all remaining water. The No. 1 system has started scanning the line, aiming to locate E22310 as soon as possible in order to create conditions for stabilizing the oil level at the water surface. The steam volume can be increased appropriately; after the FV22206 drain is free of oil, reduce the steam volume. T22201A → P22207 → E22310 → E22212AB → E22217 → FV22206 → T22201A ↑ Steam. T22201B → P22215 → E2223 → FV22214 → T22201B ↑ Steam. (7) Light fuel oil system: E22208AD stops the circulation of hot water; E22210AB stops the circulation of water and drains any remaining water. The light fuel oil then begins to flow through the normal discharge line. After 2 hours when significant steam is observed in the tank area, the flow direction is changed to the T22303 line. At the same time, it sweeps into V22214 as well as the return lines of the light diesel makeup oil and various flushing oil pipelines. The reprocessed light fuel oil line is purged in reverse by introducing steam from the drain connection before the inlet lift pipe control valve. ┌─→Pipeline P22234/3 → inlet of P22207. After the extraction valve T22202 → P22206 → E22211AB → E22207 → E22208AD → E22209AB ↑ LS → FV22102 – steam. T22303 ← FV22303 ← E22210AB ←—— intermediate tank area ← FV22232 ←—— V22204 ← LV22401 ←—— flushing oil for various pipelines ← pipeline FLO22201. After the combustion oil used in the reaction is stopped, the main valve for feeding oil to the reaction vessel is closed; oil is then drained from V22204 and sent into the light fuel system of the plant. After P22214 is evacuated, steam supplied from behind P22214 is used to sweep the oil back into V-204. After 2.5 hours, once no oil is present in the E-214 drain, the steam supply is stopped and the main oil isolation valve is closed. The oil stored in V-204 is sent to the light fuel pipeline. After P-210 is evacuated, open the main oil valve to use steam supplied from behind P-210 to purge the oil sealing lines and flushing oil lines at the inlet and outlet of each pump. After the liquid level in T22303 stopped rising, increase the flow rate of LV22304 and open the drain valve; once no oil is flowing out through the drain, immediately close LV22304. Steam is introduced from the drain line to clean the T22201 line; at the same time, light fuel is diverted to clean the rich-poor absorption oil lines. Starting from FV22303, the flow passes through T22303 and then returns to T22201A and T22202 → P22206AB → E22211AB → E22207 → E22208AD → E22209AB ↑ Steam. T22201A←E22226←E22207←T22303 (crossing line) → P22324←FV22303←E22210AB← (8) The secondary system: As the feed oil system begins to be cleaned, the re-refining system also starts its cleaning process. V22202→P22208→FV22225→MI22101 ↑ Steam. After confirming that there is no oil in the crude oil system, P22208 is evacuated repeatedly before being shut down; the water in the V22403 system is drained, and the cleaning process for the second system begins. V22202→P22208→E22214→FV22207→T22201A ↑ Steam. Once there is no oil in the drain line of FV22225, the cleaning process for the re-refining line is completed. If there is still residual oil in the re-refining tank at this time, P22208 can be opened to pump it back to the fractionation tower via internal reflux. Finally, scan the internal return line again. V22202→P22208→FV22202─→T22201A ↑ Steam (9) Slurry system: After all the reflux purging in the distillation column is completed, P22209 is evacuated repeatedly before purging begins. Once the upper and lower sections of the tower have been cleaned, the slurry can be discharged through the large and small external discharge nozzles. If the up and down tower return paths have not been scanned yet, the up and down tower return lines must be scanned first to send the oil back to the tower. After closing the main valves for upward and downward flow to the tower, open P22209 to pump the oil out, then purge the line. Meanwhile, for the oil slurry, activate the external circulation line of the tower and also use steam to purge the line. Oil slurry flows up and down the tower: after the extraction valve of T22201A (bottom) → P22209 → E22202AB → E22215AB → TV22202B → LS pipeline; P22262/3 ← LS outlet → large and small external discharge lines → (10) In coordination with the reaction unit, blind flanges SB22201/22205 are installed. After cleaning the bottom of the fractionation tower with stirring steam, the steam supply is stopped; the stripping steam to the light fuel oil stripper is also ceased. Nitrogen is supplied to the top of V22203AB to maintain a slight positive pressure, and blind flanges SB22201/22205 are installed in coordination with the reaction unit. 3. Boiling in the fractionation tower: Water is injected into the main and auxiliary fractionation towers from P22202/3. The stirring steam and stripping steam at the bottom of the tower are increased in volume to flush the tray sections, and the water temperature is raised to 80–90°C. Drainage is allowed through the bottom of T22201AB; once it is confirmed that T22201AB has been thoroughly flushed, hot water is introduced again. 4. Hot water is used in the heavy oil system for transportation, while steam is used in the overhead gas system for cooking. Hot water is drawn from the distillation tower in the slurry, reprocessed oil, and crude oil systems, and then used for multiple rinses before being discharged. T22201A→P22209→E22202→E22215→P22291→E22213→Start-up cycle line P22116→V22201→P22201 ↑ ┌→E22201→E22211─┐ | P22201→FV22216┤ ├→V22205→E22212→E22202→E22224→T22201B→P22213 | └→E22222→E22223 ┘ | | │ | ┌→FV22225───────────────┐ │ | │ ┌ Accident bypass line ←┐ ↓ │ └──── FV22202←┤P22208←V22202←┤ ├──FV22201←E22214←E22215←┘ │ └Feed oil nozzle preheater←┘ └→E22214→FV22207→Pipeline P22268/1→Pipeline P22276/2→V22202 After the hot water transfer is complete, drain all remaining water. Turn on the stripping steam and stirring steam, activate the drain of T22201AB and the vent at the top of V22203AB, to steam-clean the distillation tower and the overhead vapor system. 5. For the small amounts of dead corners and blind spots remaining from the cleaning process, barrels can be installed on-site to drain the oil accumulated in the pipelines; safety must be considered during this drainage process. 6. After oil removal and line cleaning as well as steaming are completed, blind flanges are installed on the distillation system; the combustible gas content in the analysis tower is reduced to less than 0.2%. The maintenance team opens the manholes and hands over the site for maintenance work. Section 3: Shutdown Procedures for the Absorption and Stabilization Unit I. Oil Removal from the Absorption and Stabilization Unit Once the feed to the reaction process is stopped, the distillation unit evacuates the light oil from V22203AB, and then stops the supply of absorption oil to T22304 through T22301. The principle behind oil removal is to drive the oil as far as possible towards T22304; after each extraction pump has been evacuated, it is shut down, thereby completing the oil removal process. Before the start of the first sweep in distillation, all oil in T22304 is drained. Light oil flows from T22301 → V22302 → T22302 → T22304 → the refining unit → then to the discharge point. The oil with low absorption capacity goes via a bypass line, without passing through T22303, and returns directly to T22201A. The oil pressure in T22303 is directed back to T22201A; care must be taken to ensure that the liquid level in T22303 does not drop to zero, as it is strictly prohibited for dry gas to enter T22201A. When the temperature at the reboiler outlet remains relatively stable, increase the output volume of stabilized light oil; while maintaining the top temperature of the tower constant, strive to increase the amount of liquefied gas sent out. When there is no liquid level in V22303, stop P22306AB. Send the alkali-removal slag from the refining unit to V26106. II. Absorption and stabilization unit – oil on top of water 1. The tube side of E22310 has not been thoroughly purged through distillation; water ingress into T22304 is strictly prohibited to prevent bumping. 2. Unqualified light oil outlet line: Fresh water → P22202 → FV22218 → Pipeline P22218/2 → Pipeline P22222 → Unqualified light oil tank. 3. Fresh water follows the normal flow path: T22301 → P22202 feedwater → FV22218 → T22301 → P22203 feedwater → FV22221 → T22301.
4. Return lines for T-301 Unit 1 and Unit 2: Unit 1: P22303 → LV22302 → E22303 → T22301; Unit 2: P22304 → LV22303 → E22304 → T22301.
5. Condensate oil line: T22301 → P22302 → FV22302 → V22302 → P22301 → FV22306 → E22305 → T22302 → FV22305 → V22301 (feedwater) → P22309 → LV22601.
6. Deethanized light oil line: T22302 → P22305 → FV22307 → E22307 → T22304.
7. Stabilizer return line: P22306 feedwater → FV22308 → T22304.
8. Line for supplying absorbent to T22301: T22304 → P22307 → FV22301 → T22301.
9. Skimming in the absorption and stabilization unit: The absorption and stabilization unit is converted to a three-tank circulation system. After 2 hours, T22301 and V22302 are evacuated, with all water concentrated in T22302 and T22304. The water level in these two tanks should be high enough so that water can be seen at the inlet of P22307 via the skimming line. The floating oil in T22302 and T22304 is sent to the tank area via the skimming line using P22307, through the reject line, until it is emptied. This process is repeated 3 times to confirm that there is no oil left, after which water from P22202 is used to push the remaining oil in the reject line into the tank area. III. Light oil refining section 1. The alkaline waste streams from the system, namely V26101, V26102, R26101AB, and T26101, are combined and sent to V26106; while the alkaline residues from V26103 are sent through P26102 to tankers for disposal. 2. System oil on top of water – For the light oil refining system, the oil on top of water is handled simultaneously with that in the absorption and stabilization system; it follows the normal process from T22304 to MI26101, then to the refining system, and finally to the output point. V26102 is evacuated more than three times. 3. When there is water on the light oil line, the alkali solution system undergoes washing; in the washing process for the alkali solution, the water is collected in V26106 for unified discharge. 4. Once the washing with top oil is complete, open the drain valves of each tower and tank to release water, and close the drain valves after the water has been drained. Note: During the water-on-top-of-oil process, T22302, T22304, and V26102 must be evacuated 3 to 4 times repeatedly so that the residual light oil in the system can be removed more thoroughly. After the water stripping in the absorption stabilization and light oil refining system is completed, close the boundary valves leading to and from this system, and use 8-shaped blind plates for guidance. 5. Steam is introduced to the bottoms of various towers and tanks within the system for steaming, while vents are opened at the tops of these towers and tanks. IV. Liquefied gas – Dry gas desulfurization unit: 1. The dry gas comes from T22303 → pipeline P26201 → pipeline P26207 → fuel gas network → flare, passing by V26202 and T26202. 2. Liquid hydrocarbons are sent from the refining system to the tank farm via the normal process flow. 3. The dry gas, liquid hydrocarbons, and amine solution systems are separated, and the amine solution system is recycled and regenerated. 4. After stopping the feed, make every effort to maintain the pressures of T26201 and T26202, and allow the solvent to continue circulating for regeneration until the analysis shows satisfactory results. 5. After solvent regeneration stops, contact the solvent regeneration team to gradually lower the temperature at a rate of 30°C/h, using the circulation volume of the solvent in the three towers to control this rate. 6. Once the solvent regeneration system is ready for solvent rejection, transfer the amine solutions in T26201 and T26202 to the regeneration system; when rejecting the solvent, be sure to prevent dry gas or liquefied gas from entering the solvent regeneration system. 7. Liquefied gas: Dry gas desulfurization unit – water transport; FV22506, FV22508, P226201. Feed water → T26201 solvent regeneration system; T26202, LV22512, LV22514. After the water transport is completed, the liquid is discharged on-site, and the liquefied gas desulfurization and dewaxing system begins to liquefy the gas using water. V. Liquefied gas desulfurization and alkylation unit 1. The alkali waste streams from the liquefied gas desulfurization and alkylation system, namely V26301, V26303, T26301, and T26303, are combined and sent to V26106; the alkali residues from V26103 are transferred to tank trucks via P26102 for disposal. 2. LPG desulfurization system: Water-top LPG P22306 → fresh water → V26201 → T26201 → V26301 → T26303 → V26302 → T26303 → discharge. Once a large amount of water is observed at the sampling port, the water supply is stopped for 1 hour every 2 hours, and this process is repeated to ensure that all the liquid hydrocarbons are removed. 3. When liquefied gas is depressurized in the LPG desulfurization system, the alkali solution system undergoes washing; the water generated in this washing process is collected in V26106 for unified discharge. Once the water-pressurized liquefied gas processing in the LPG desulfurization system is complete, open the drain valves of each tower and tank to release water, and close these drain valves after the water has been drained. 4. Nitrogen is used for purging each tower and tank, and the flare system is discharged. After the system replacement is complete, steam it for cooking. VI. Purging Process
1. Purging of T22301 using N2: The process for purging the systems T22301, 22303, and 26202 is as follows:
　┌──→P22302AB→Pump pressure reduction line→Flare line N2
　──→T22301→T22303→PV22301→V26202→T26202
　↓ ↓
　SV22302 auxiliary line, Safety valve auxiliary line
　↓ ↓
　Flare line

2. Purging of T-304 using N2: The process for purging the systems T22304 and 26201 is as follows:
　┌────────────────┐
　↓ ↓ N2
　↓ P22306 inlet drain
　──→FV22308→T22304→V22303→PV22310
　↓ ↓
　│ ↑ ↓
　Pressure reduction line FV22309
　└→ E22308/9
　↓ ↓ ↓ ↓ ↓
　Flare
　V26201
　SV22304AB auxiliary line─────→ Flare
　↓→SV2601→Flare
　T26201→SV2602→Flare

3. Purging of T22302 using N2: The process for purging the system T22302 is as follows:
　N2──→T22302→PV22302→E22301→E22302→T22301
　↓ SV22303AB auxiliary line→Flare

4. Purging of the flare system: N2 is introduced from the six safety valve outlets at the top of tower T22201AB to flare V22310, thereby purging the flare system. 5. Purging of the rich gas system: N2 is introduced from V22203AB and blown from the inlet of the rich gas compressor to its outlet, after which it is vented through a flare. Once the system scanning is complete, blind plates begin to be installed, and the steam systems in each tower are used for cooking.