How is the circulation system of a hydrogenation unit purged???

The question is a bit vague: what does the hydrogenation unit circulation system and the large distillation circulation system refer to? Hydrogenation units are generally divided into a reaction section and a distillation section, also known as the hydrogenated system and the non-hydrogenated system. There are two types of cycles: the large cycle and the small cycle. The large cycle refers to the cycle of the entire installation, while the small cycles are the reaction cycle and the distillation cycle. Chapter 4: Purging and Flushing of Process Piping and Equipment Section 1: Purpose of purging and flushing: 1. To remove rust, slag, and other debris accumulated within the piping and equipment. Prevent valves from getting stuck and pipelines as well as valves and equipment from becoming clogged. 2. Check whether the equipment pipelines are unobstructed and whether their installation meets the design requirements. Check the changes in the pipeline under hot conditions, and verify whether there are any leaks in the pipeline, flanges, welds, and valves. 3. Improve technical training to ensure smooth commencement of work. Section 2: Principles and Requirements for Purging and Flushing 1. Purging and flushing media: (1) 1.0 MPa steam (2) 0.6 MPa nitrogen (3) 0.6 MPa air (4) 0.3 MPa fresh water (5) 0.3 MPa recycled water 2. Principles and requirements for purging and flushing: (1) The installation must have passed the acceptance inspection. (2) The system’s steam, water, air, and nitrogen are connected to the plant’s pipeline network, enabling the supply of water, steam, air, and nitrogen at any time. (3) The purge lines for clean air, unclean air, nitrogen, circulating water, fresh water, demineralized water, and steam shall all be purged with their respective media. (4) The principle for purging pipelines is to proceed in the direction of the flow. During purging, the pipelines should be purged section by section, starting with high pressure before moving to low pressure, starting with the pipelines themselves before the equipment, and starting with the main lines before the branch lines. (5) To prevent dirt from being blown into the equipment, the purging pipeline should be disconnected from the equipment; a blind flange or baffle should be installed near the equipment’s flange to stop dirt from entering. Once the pipeline has been thoroughly purged, it can be reconnected to the equipment to continue with the purging and cleaning process. The lines connected to the back of the equipment are generally purged from inside the equipment to the outside; make sure to remove the foam breakers inside the towers and containers. (6) Disconnect or isolate the control valve, metering orifice plate, flowmeter, pressure gauge, check valve, safety valve, steam trap, sampling valve, etc., in connection with the instruments to prevent damage, and restore them to their original positions after the purging is complete. (7) The inlet and outlet flanges of the pump must be removed, and the flange surface facing the direction of gas flow should be covered with metal sheeting to prevent steam or dirt from entering the pump. This is necessary to avoid damage to the sealing surfaces caused by impurities carried in the purging medium. (8) When sweeping the line past the control valve, use a bypass line and vent at both ends. (9) Close all valves in the process system as well as the connection valves for water, steam, air, and nitrogen in the relevant process pipelines. (10) It is necessary to have the person in charge of purging confirm whether the pipeline has been thoroughly purged. It is generally required that the steam being discharged be checked with a white cloth to ensure it is clean. For the purging of the turbine main steam, a pre-made aluminum plate can be placed at the discharge outlet to conduct a \"targeting\" test; by counting the number of pitting marks on the plate, it is possible to determine whether the purging has been successful. (11) In accordance with the requirements of the blind flange table for the startup process, all blind flanges shall be installed or removed in their proper positions. (12) When using steam to purge the heat exchanger, make sure to vent the other side to prevent pressure buildup. (13) The pipelines of the compressor system must be purged first; in particular, the compressor inlet pipelines and equipment need to be thoroughly cleaned. (14) The pressure testing of containers and towers should be carried out simultaneously with flushing and purging. Section 3: Precautions for Purging 1. Carry out flushing and purging in accordance with the process sequence. During purging, follow unified instructions, maintain close communication with relevant units and positions, and keep accurate records of the purging process. 2. Steam should be used in a concentrated manner to prevent excessive use or unstable pressure from affecting the purging effect. 3. It is necessary to adhere to the principle of draining condensate first and then introducing steam, with the introduction of steam being done slowly – starting with a small amount of steam before increasing the amount – in order to strictly prevent water hammer. 4. When purging the pipeline with steam, it is necessary to do so slowly in the initial stage as a preheating process. It is crucial to avoid increasing the steam flow rapidly after introducing it, as this can cause the pipeline to expand suddenly due to heating. If there is no time for compensation, the pipeline may be lifted, leading to the detachment of pipe supports, deformation of the pipeline, fragmentation and falling off of the insulation layer, tilting of the pipe supports, cracking of welds, and separation of gaskets. 5. During steam purging, contact the instrumentation team to purge the instrument nozzles along with the leads. The safety valve is not involved in the purging process and is removed during purging. 6. When encountering equipment such as heat exchangers, air coolers, towers, and containers, first remove the inlet flange for purging; once it is clean, proceed to pass through the equipment. Be sure to use guards to protect the flange surface when it is removed. When purging a heat exchanger, if one side is not to be purged, the vent valve must be opened in advance to prevent pressure buildup ； Pass through the air cooler slowly. When the container is filled with water, the upper vent should be opened to prevent overpressure. 7. Those equipped with glass plate level gauges and sampling ports should be purged along with the equipment pipelines. 8. Ensure thorough purging with no dead corners; the leak testing pressure for low-pressure systems shall be ≤ 1.0 MPa. 9. After the purging and pressure testing are completed, the vent valve and drain valve should be opened to prevent a negative pressure from forming inside the tower or vessel (Note: When venting the hydrogen sulfide removal tower and the distillation tower, the vent valve at the top of the tower should be opened). 10. The hydrogen-handling system is purged with nitrogen. 11. Any small pipeline joints not listed shall be purged temporarily with steam. 12. Underground pipelines shall not be purged with steam; they must be purged with air instead. 13. The pipeline purging time should be no less than 0.5 hours until the pipeline is clean. The steam purge should have a sufficient velocity (not less than the operating flow velocity), generally not less than 20 m/s. 14. When purging through, it is generally done by venting from the removed spool; if that is not possible, venting through the removed flange is used. 15. When steam passes by the pump, it is purged through the inlet and outlet connection valves, preventing steam from entering the pump to protect it. 16. Generally, after the pipeline cleaning is completed, the removed valves and flanges must be reinstalled, and the connection valves of the pipeline that has been cleaned must be closed before proceeding with the cleaning of the next section of pipeline. 17. Before purging the front section of the equipment inlet, it is not allowed to purge the towers, vessels, and heat exchangers. 18. For longer pipelines, purging should be carried out in sections by removing the flanges; once the preceding section has been thoroughly purged and found to be satisfactory, the flanges are reattached to proceed with purging the subsequent section of the pipeline. 19. During purging, tools can be used to gently tap the dead corners of the pipes and the bottom of the pipelines in order to loosen debris, but care must be taken not to damage the pipelines. 20. Pay attention to ensuring thorough purging; if the pressure of the purging medium is low, the intermittent pressure-holding method should be used, with purging directed at one pipeline alone, and the flow rate must be no less than 20 m/s. Section 4: Precautions for Flushing 1. Before flushing, do not reset the control valves, pressure gauges, oil gauges, check valves, flow meters, and other removed piping components; reset them only before starting the water test. 2. The hydrogen-handling system is not involved in water flushing. 3. When filling containers and towers with water, open the vent at the top facing upward to prevent pressure buildup. 4. The flushing process should be carried out following the principle of flushing the main lines first and then the branch lines. 5. Whenever a flange is removed and emptied, it should be covered with iron sheet at the rear end. 6. Flush the instrument leads together. 7. The cleaning process should continue until the water is clear and free of impurities. 8. During flushing, open the discharge points one by one; after flushing thoroughly, close them promptly to maintain the flushing water pressure. 9. After the water flushing is complete, open the vent valves at the top of the tower and containers to drain any water remaining in the pipes and equipment. As soon as possible, reinstall the removed control valves, flow meters, pressure gauges, oil gauges, etc.; replace the asbestos gaskets during reinstallation to prepare for water testing. Section 5: Purging Process (omitted) Section 6: Water Flushing Steps and Methods 1. Introducing flushing water: ① Slowly open each fresh water drain valve to discharge the wastewater; only after the water is clear can it be introduced into the process pipelines and containers. ②Rinse the tower and containers with water; make sure they are filled with water and let the water stand for half an hour. Then drain the water from the bottom, and stop rinsing once the water becomes clear. (Note: Open the top vent when adding or removing water.) ③ Fresh water is added to each tower from the inlet of the top reflux tank, and the reflux pump is started to pump the fresh water into the tower from the top. The crude oil pretreatment system draws water from the fresh water line connected to V1101. At the same time, temporary belts can be connected at different locations as needed to supply water. 2. Water flushing steps and methods in the raw material pretreatment section: ① Connect a temporary fresh water line from the filter outlet to feed water into V1101; open the top vent valve to prevent pressure buildup, and open the bottom vent valve to discharge waste water. Close these valves once the water is clean. ②After filling V1101 with water, perform a water flush in the order of the connected pipes from top to bottom. ③Flush the gas line, and turn it off once the water is clear. ④Flush the raw material line and start the circulation line; turn it off once the water is clear. ⑤Flush the minimum flow return line at the P1101 outlet; close it once the water is clear. ⑥Flush the P1101 inlet line, sulfur injection line, scale inhibitor line, and liquid vent line; close it once the water is clear. 3. Steps and methods for low-pressure water flushing: ① Connect a temporary water line at the V1103 outlet for water flushing. ②The water flushing process follows the purging procedure for each line. ③When using water for rinsing, it is essential to ensure the quality of the rinse; the water discharged must be clean. ④Water flushing should be carried out in the same way as steam purging, by flushing each line sequentially. ⑤After flushing, restore one line at a time and tighten the flange connections. 4. Steps and methods for tower water flushing 4.1 Flush the stripping tower T1101 system; the water flushing procedure follows the purging procedure. ①The stripper is filled with water, which is introduced from the inlet of the reflux tank. The water is pumped into the tower via the reflux pump P1103 (with a filter screen at the inlet); it first washes the tray in the tower, and wastewater is discharged from the bottom of the tower. Once the water is clean, discharge of wastewater stops and the tower is fully filled with water. Flush each pipeline in ascending and descending order. ②Flush the outlet line at the top of the tower, and check the water quality using the vent valve at the level gauge of the reflux tank; flushing is complete once the water becomes clear. ③Flush the feed line: water enters the feed line from the inlet, flows through E1106/DCBA, and then is discharged via the low-level liquid control valve; once the water becomes clear, the flushing is complete. ④Flush the direct feed line; allow water to flow into the feed line and then discharge it from the flange at the inlet of tower T1102. The flushing is complete once the water becomes clear. file:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/msohtml1/01/clip_image001.gif⑤Flush the sulfur-containing wastewater line; open the boundary line valve for venting, and stop flushing once the water becomes clear. ⑥Flush the bottom extraction line of the tower; allow water to flow into the inlet flange of extraction line E1102 for venting. Once the water becomes clear, tighten the inlet flange and start flushing the outlet of E1102; stop flushing once the water is again clear. 4.2 Flush the fractionation tower T1102 system; the water flushing procedure follows the purging procedure. ①Fill the distillation tower with water by introducing it from the inlet of the reflux tank. The water is pumped into the tower using the reflux pump P1104 (with a filter screen at the inlet); this water first washes the tray sections of the tower. Wastewater is discharged from the bottom of the tower, and once the water is clean, discharge stops and the tower is filled completely with water. Flush each pipeline in ascending and descending order. ②Flush the top outlet line of the tower; once the tower is filled with water, start flushing this outlet line. Check the water quality using the vent valve at the level gauge of the reflux tank, and the flushing is complete once the water becomes clear. ③Flush the feed line: water enters the feed line through the inlet and is discharged from the flange of the feed line control valve; flushing is complete once the water becomes clear. ④Flush the reflux line and the naphtha outlet line: water enters the reflux line through the reflux port, and then is discharged through the boundary valve of the naphtha outlet line; flushing is completed once the water becomes clear. ⑤Flush the refined diesel line: water is drawn from the bottom of tower T1102 to the pump inlet for discharge; once the water becomes clear, start pump P1105 (equipped with a filter screen at the inlet) to flush E1106/ABCD (flushing each unit one by one) → A1104 → then discharge it through the boundary valve at the end of the plant line; the flushing is completed once the water becomes clear. ⑥Flush the scale inhibitor preparation diesel lines 25-P1160 to V1108. This post was last edited by qlasd on 2009-4-10 01:16.]

Is the fractional distillation large-cycle system a long cycle? Just follow the procedure and perform steam purging. During the cleaning process, steam from entering the hydrogen system must be prevented. The hydrogen-containing system can only be purged with nitrogen.

Reaction system: From the outlet of the raw material pump and the outlet of the circulation compressor to the high-pressure section; it is purged with nitrogen, and sampling at the top of the high-pressure section shows that a hydrocarbon plus hydrogen content of less than 0.5% indicates compliance； The large distillation cycle is purged with steam.

The hydrogen-handling system is purged using nitrogen or purified air for blasting； Non-hydrogen systems are purged with steam.

The hydrogen-containing system is purged using nitrogen, the distillation system is purged with steam, and finally it is operated with water.

The hydrogen-handling system is purged with nitrogen. Large-diameter pipelines are generally purged using the blasting method.

Upstairs, why can’t the hydrogen-facing system be purged with steam, and why isn’t a catalyst installed either?