Compilation of the textbook “Unit Processes and Operations in Chemical Engineering”

Table of Contents Chapter 1 General Overview of the Unit 1 Section 1 Brief Description of the Process Flow 1 Section 2 Process Control Parameters for Key Equipment 5 1. Flash Tower T-101 5 2. Atmospheric Tower T-102 5 3. Vacuum Tower 5 4. Atmospheric Furnace F-101, Vacuum Furnaces F-102, F-103 6 Section 3 Key Regulators and Instruments 6 Chapter 2 Cold Start-Up Process of the Unit 10 Section 1 Preparation for Start-Up 10 Section 2 Cold Start-Up 10 Chapter 3 Normal Shutdown Process of the Unit 23 Section 1 Reducing Operation Capacity 23 Section 2 Phase of Shutting Down Side Lines While Reducing Capacity 23 Section 3 Circulation within the Unit and Shutdown of Furnaces 24 Chapter 4 Emergency Shutdown 26 Chapter 5 List of Incidents 26 Section 1 Disruption in Crude Oil Supply 26 Section 2 Power Supply Disruption 26 Section 3 Disruption in Circulating Water Supply 27 Section 4 Steam Supply Disruption 27 Section 5 Disruption in Purified Air Supply 28 Section 6 Fire in the Heating Furnace 28 Section 7 Stoppage of the Bottom Pump in the Atmospheric Tower 29 Section 8 10% Sticking of the (Atmospheric Tower Top Reflux Valve) 29 Section 9 10% Sticking of the (Vacuum Tower Discharge Valve) 30 Section 10 Evacuation in the Bottom of the Flash Tower 30 Section 11 Shutdown of the Vacuum Furnace 30 Section 12 Fault in Pump -1 31 Section 13 Low-Pressure Spark 31 Section 14 High-Pressure Spark 32 Section 15 Water Content in Crude Oil 32 Chapter 6 Scoring Criteria 33 Section 1 Scoring Rules 33 Section 2 Quality Scoring for Cold Start-Up 34 Chapter 7 Design of Lower-Level Machine Screens 35 Chapter 1 General Overview of the Unit This unit is a petroleum atmospheric and vacuum distillation unit. Crude oil is pumped to the heat exchanger by a crude oil pump, where it is heated to around 110°C. A certain amount of demulsifier and washing water are added, and after thorough mixing, the mixture enters the primary electrodesalination tank. At the same time, the oil and water are separated under the action of a high-voltage electric field. The dehydrated crude oil flows out from the top collection pipe of the primary electrodialysis tank, after which demulsifier and washing water are added. After thorough mixing, it enters the secondary electrodialysis tank, where, under the action of a high-voltage electric field, further separation of oil and water takes place, thereby achieving the purpose of electrodialytic desalination of the crude oil. It is then heated to around 200°C in a heat exchanger before entering the evaporation tower, where a portion of the light components is separated out. The distillate oil is then pumped to the heat exchanger using a pump to be heated further to above 280°C, after which it is sent to an atmospheric pressure furnace to be raised to 356°C before entering the atmospheric pressure column. Before separating the heavy diesel fractions in the atmospheric pressure tower, the high-boiling-point heavy fractions are pumped to the vacuum furnace and heated to 386°C before being fed into the vacuum tower. Lubricating oil fractions are separated out in the vacuum tower, while the light heavy oil from the tower is pumped to a heat exchanger for cooling before being discharged from the plant. Section 1: Brief Description of the Process Flow I. Heat Exchange in the Crude Oil System The crude oil in the tank area (at 65°C) is pumped into the facility by the crude oil pumps (P101/1,2). There, it first exchanges heat with the gasoline from the top of the flash tower and the gasoline from the top of the atmospheric distillation column (H-101/1-4), reaching a temperature of around 80°C. After that, the crude oil undergoes heat exchange in two separate paths: in one path, it exchanges heat with lines H-102/1,2, H-103/1,2, and H-105/1,2, reaching a temperature of around 140°C (TIC1101) ； Another stream of crude oil exchanges heat with Line H-106/1,2 (Reduced Pressure Line 2), Line H-107 (Normal Pressure Line 1), Line H-108/1,2 (Normal Pressure Line 2), and Line H-109/1,2 (Normal Pressure Line 3) until the temperature reaches around 140°C (TI1101); thereafter, the two streams combine and flow into the electrodesalination tank (R-101/1,2) for desalination and dehydration. After desalination, the crude oil (at around 130°C) exits the electrodesalination unit and is routed to two separate paths for heat exchange. In one path, the crude oil exchanges heat with H-103/3,4 and H-104/3-7, as well as H-103/5,6, reaching a temperature of around 235°C (TI1134). In the other path, the crude oil exchanges heat with H-111/1-3, H-108/3, H-109/3, H-106/5,6, H-112/2,3, and H-109/4, also reaching a temperature of around 235°C (TIC1103). Once combined, these two streams enter the flash tower (T-101). It can also be directly fed into the atmospheric pressure furnace. The oil vapor from the top of the flash tower enters the top of the atmospheric pressure tower at around 180°C (TI1131), or it goes directly to the gasoline heat exchanger (H-101/1-4) and the air cooler (L-101/1-3). The crude oil from the extraction unit is pumped out by the extraction pump (P102/1,2), where it exchanges heat with line H-113/1. After that, it splits into two streams: one stream exchanges heat with lines H-110/2-4 and H-113/2 to reach a temperature of around 281°C (TIC1102); the other stream exchanges heat with residue oil (H-104/8-11) to reach a temperature of around 281°C (TI1132). Once these two streams combine, they exchange heat with residue oil (H-104/12-14) to reach a temperature of around 306.8°C (TI1106), after which they split again and enter the convection chamber of the atmospheric furnace for heating, and then proceed to the radiation chamber of the same furnace to reach the desired temperature before entering the feed section of the atmospheric tower (T-102) for distillation. II. Atmospheric Pressure Tower: The oil from the top of the atmospheric pressure tower first exchanges heat with crude oil (H-101/1-4), then enters the air cooler (L-101/1,2). It is subsequently cooled in the after-cooler (L-101/3), and then sent to the gasoline reflux tank (R-102) for dehydration; the water separated out is discharged into the sewer system. The gasoline passes through the gasoline pump (P103/1,2); some of it flows back upward while some is discharged outside. The non-condensable gas is led from R-102 to the atmospheric pressure gas tank (R-103); the condensed gasoline returns to R-102 from the bottom of R-103, while the gas is sent from the top of R-103 to the atmospheric pressure furnace for use as fuel in its own operations, or it is vented. The normal line introduces material from the 32nd (or 30th) tray of the atmospheric tower into the upper section of the atmospheric stripping tower (T-103). The stripped oil vapor returns to the 34th tray of the atmospheric tower, while the oil is pumped out from the bottom of the normal line stripping tower by pumps (P106/1, P106/B). After exchanging heat with crude oil in unit H-107, it is cooled to around 70°C in cooler L-102 before being discharged from the plant. The secondary line introduces fluid from the 22nd (or 20th) tray of the atmospheric tower into the middle section of the atmospheric stripping tower (T-103); the stripped oil vapor returns to the 24th tray of the atmospheric tower, while the oil is pumped out from the bottom of the secondary-line stripping tower using pumps (P107, P106/B). After exchanging heat with crude oil in heat exchangers (H-108/1, 2), it is cooled to around 70°C in a cooler (L-103) before being discharged from the plant. The constant-pressure three-line introduces fluid from the 11th (or 9th) tray of the atmospheric pressure tower into the lower section of the atmospheric pressure stripping tower (T-103). The stripped oil vapor returns to the 14th tray of the atmospheric pressure tower, while the oil is pumped out from the bottom of the constant-pressure three-line stripping tower by pumps (P108/1,2). After exchanging heat with crude oil in unit H-109/1-4, it is cooled to around 70°C in cooler L-104 before being discharged from the plant. At normal pressure and medium oil level, it is drawn out from the 25th tray of the atmospheric tower by pumps (P104/1, P104/B), exchanged heat with crude oil (H-111/1-3), and then returned to the 29th tray of the atmospheric tower. At normal pressure, the second intermediate oil is drawn off from the 15th tray at the top of the atmospheric tower by pumps (P104/B, P105), exchanged heat with crude oil (H-112/2, 3), and then returned to the 19th tray of the atmospheric tower. At atmospheric pressure, the residue oil is pumped out from the bottom of the atmospheric distillation column T-102 using the bottom pump (P109/1,2). It then goes to two separate paths; one path proceeds to the convection and radiation chambers of the vacuum furnace (furnaces-102, 103) where it is heated, before entering the feed section of the vacuum distillation column (T-104) at the temperature required by the process for vacuum distillation. III. Vacuum Tower: The secondary distillate oil vapor, after passing through the vacuum system, is either vented from L-110/1,2 as non-condensable gas or fed into the vacuum furnace (Furnace-102) for combustion using the gas produced there. The condensed liquid enters the reduced-vapor-pressure oil-water separator (R-104) where water is separated from it; the separated water is discharged into the sewer system, while the contaminated oil goes into an oil tank where it is further dehydrated. It is then pumped out of the unit using pumps (P118/1,2), or it is pumped by corrosion inhibitors pumps to be fed into the flash tower or the normal distillation column for reprocessing. The oil from the upper oil collection tank of the first stage vacuum distillation tower is pumped out by the first stage vacuum pumps (P112/1, P112/B). After heat exchange with crude oil in unit H-102/1,2, it is cooled to around 45°C in the coolers (L-105/1,2); part of this oil is discharged, while the rest is used as reflux in the overhead vacuum system. The reduced-pressure second-line oil is introduced into the upper section of the vacuum stripping tower (T-105); the oil vapor returns to the vacuum tower, while the oil is pumped out by pumps (P113, P112/B), exchanged heat with crude oil in reactor H-106/1-6, and then cooled to around 50°C in cooler L-106 before being discharged from the plant. The reduced-three-line oil is introduced into the middle section of the vacuum stripping tower (T-105) from the vacuum distillation tower; the oil vapor returns to the vacuum distillation tower, while the oil is pumped out by pumps (P114/1, P114/B), exchanged heat with crude oil in reactor H-103/1-6, and then cooled to around 80°C in cooler L-107 before being discharged from the plant. The reduced-four-line oil is introduced from the vacuum distillation tower into the lower section of the vacuum stripping tower (T-105). The oil vapor returns to the vacuum distillation tower, while the oil is pumped out using pumps (P115, P114/B). One portion of this oil first exchanges heat with crude oil (H-113/1,2), then exchanges heat with softened water (H-113/3,4 -> H-114/1,2), and after being cooled in a cooler (L-108) to around 50–85°C, it is discharged from the plant; another portion is sent to the lower part of the four-line oil collection tank in the vacuum distillation tower for use as cleaning oil. After being pumped out of the vacuum distillation tower by pump (P116/1,2), the washing oil is heat-exchanged with L-109/2; one part is returned to the tower as cleaning oil, while the other part is discharged outside. In the first vacuum distillation column, the oil is drawn out between line 1 and line 2 by pumps (P110/1, P110/B), exchanged heat with softened water (H-105/3), then exchanged heat with crude oil (H-105/1,2), before being returned to the vacuum distillation column. In Unit 2, the oil is drawn from between lines 3 and 4 of the vacuum distillation tower by pumps (P111, P110/B), exchanged heat with crude oil (H-110/2-4), and then returned to the vacuum distillation tower. The vacuum residue is drawn out from the bottom of the vacuum tower by pumps (P117/1,2), exchanged heat with crude oil (H-104/3-14), cooled in a cooler (L-109), and then discharged from the plant. Section 2: Process Control Parameters for Key Equipment
I. Flash Tower T-101
Name: Temperature (°C), Pressure (gauge) (MPa), Flow Rate (T/H)
Feed flow rate: 235, 0.065, 126.262
Bottom product flow rate from the tower: 228, 0.065, 121.212
Top product flow rate from the tower: 230, 0.065, 5.05

II. Atmospheric Pressure Tower T-102
Name: Temperature (°C), Pressure (gauge) (MPa), Flow Rate (T/H)
Reflux from the top of the atmospheric pressure tower back to the tower: 120, 0.058
Reflux from the top of the atmospheric pressure tower back to itself: 35, 10.9
Distillate from the first line of the atmospheric pressure tower: 175, 6.3
Distillate from the second line of the atmospheric pressure tower: 245, 7.6
Distillate from the third line of the atmospheric pressure tower: 296, 8.94
Feed flow rate: 345, 121.2121
Output/reflux from the middle section of the first line of the atmospheric pressure tower: 210/150, 24.499
Output/reflux from the middle section of the second line of the atmospheric pressure tower: 270/210, 28.0
Bottom product of the atmospheric pressure tower: 343, 101.8

III. Vacuum Tower
Name: Temperature (°C), Pressure (MPa), Flow Rate (T/H)
Product output from the top of the vacuum tower: 70, -0.09
Distillate/reflux from the first line of the vacuum tower: 150/50, 17.21/13
Distillate from the second line of the vacuum tower: 260, 11.36
Distillate from the third line of the vacuum tower: 295, 11.36
Distillate from the fourth line of the vacuum tower: 330, 10.1
Feed flow rate: 385
Output/reflux from the middle section of the first line of the vacuum tower: 220/180, 59.77
Output/reflux from the middle section of the second line of the vacuum tower: 305/245, 46.687
Sludge output/reflux: Bottom product of the vacuum tower: 362, 61.98

IV. Atmospheric Pressure Furnaces F-101, Vacuum Furnaces F-102, F-103
Name: Oxygen content (%), Furnace negative pressure (MMHG), Furnace temperature (°C), Temperature at the furnace outlet (°C)
F-101: 3–6, -2.0, 610.0, 368.0
F-102: 3–6, -2.0, 770.0, 385.0
F-103: 3–6, -2.0, 730.0, 385.0

Section 3: Key Regulators and Instruments
I. Regulators
Serial Number, Tag Number, Normal Value, Unit, Description
1. FIC1101: 126.2 T/H, Crude oil feed
2. FIC1104: 121.2 T/H, Bottom product flow rate from T101 tower
3. FIC1106: 60.6 T/H, One of the feed streams to furnace F101
4. FIC1107: 60.6 T/H, The other feed stream to furnace F101
5. FIC1111: 51.9 T/H, Feed to furnace F102
6. FIC1112: 51.9 T/H, Feed to furnace F103
7. FIC1207: 61.2 T/H, Bottom product flow rate from T104 tower
8. FIC1117: 6.35 T/H, Wash water feed to R101/1
9. FIC1118: 6.35 T/H, Wash water feed to R101/2
10. FIC1116: 6.36 T/H, Product flow rate from the first line of the stripping tower
11. FIC1115: 7.65 T/H, Product flow rate from the second line of the stripping tower
12. FIC1114: 8.94 T/H, Product flow rate from the third line of the stripping tower
13. FIC1108: 25 T/H, Circulation volume of the middle section of the first line
14. FIC1109: 28 T/H, Circulation volume of the middle section of the second line
15. FIC1211: 11.36 T/H, Product flow rate from the second line of the stripping tower
16. FIC1210: 11.36 T/H, Product flow rate from the third line of the stripping tower
17. FIC1209: 10.1 T/H, Product flow rate from the fourth line of the stripping tower
18. FIC1203: 59.77 T/H, Circulation volume of the middle section of the first line
19. FIC1204: 46.69 T/H, Circulation volume of the middle section of the second line
20. FIC1208: 17.21 T/H, Return flow rate from the first line of the stripping tower
21. FIC1110: 10.9 T/H, Reflux from the top of the atmospheric pressure tower
22. LIC1101

Operators in the liquid chlorine handling area must conscientiously fulfill their job responsibilities during daily production. In addition to completing their assigned tasks, they should carry out regular inspections, address any issues that arise during production promptly, keep accurate records, and ensure proper handover of duties. They must also strictly adhere to and follow the relevant operating procedures for this position. (1) Operation to change the liquid chlorine storage tank: a) Based on the reading from the level monitoring instrument of the liquid chlorine storage tank, determine that the liquid chlorine level in the tank has reached the specified level. Check that the backup tank is either pressure-free or has a pressure no higher than that of the system. Verify that the balance valve is open and that all other process valves are closed, before opening the chlorine flow valve. b) Close the chlorine flow valve of the full storage tank, and record the time when the tank is full along with its tank number. (2) Operation of transporting liquid chlorine and venting the storage tank: a) When the liquid chlorine stored in the tank meets the production requirements, the operator on this post shall promptly inform the personnel responsible for packaging liquid chlorine to get ready for bottling it. b) Liquid chlorine is transported using a shielded pump for packaging. The operation can be summarized as follows: Before starting the pump, first open the chlorine outlet valve at the bottom of the storage tank, activate the solenoid valve, open the reflux valve and the vent valve of the pump system located on the storage tank, open the inlet valve of the shielded pump, and use the vent valve to release air. Once the desired liquid level and temperature are achieved, close the vent valve, slightly open the pump’s outlet valve, inform the packaging team to watch for any leaks in the pipes, and then start the pump. After confirming that the pump is operating properly, slowly open the pump outlet valve to deliver liquid chlorine to the packaging and storage tanks. Adjust the reflux valve to maintain the pipeline pressure at 0.8 Mpa–1.0 Mpa and keep it stable. Inform the packaging staff that packaging can proceed; once packaging is completed, adjust the reflux valve to ensure the pump operates properly. During the packaging process, the reflux valve should be adjusted promptly according to pressure conditions; attention must be paid to liquid level monitoring and temperature changes, and preparations should be made for emergency shutdown in case of accidental leaks. (3) Shutdown procedures for the liquefaction system: a) Upon receiving the scheduling instruction to shut down the liquefaction system, notify the chlorine-hydrogen treatment unit responsible for handling accidents to get ready to receive the exhaust gases. After the tail chlorine tower in the hydrogen chloride process is shut down, the tail chlorine is diverted to the emergency chlorine process. b) Open the connection valve between the primary chlorine distribution panel and the tail chlorine distribution panel to exhaust air. c) Close the chlorine valve from the original chlorine distribution station to the liquefier, and the main tail chlorine valve leading to the tail chlorine distribution station. Contact the freezing station to stop supplying chilled brine to the liquefier. d) After the chlorine-hydrogen treatment chlorine compressor is shut down, and the pressures at the feed and tail chlorine distribution stations drop to zero, close all valves at these distribution stations. (4) Emergency shutdown procedure: In the event of an emergency that causes the hydrogen chloride production to come to a complete stop, the valve for the chlorine gas going to the accident area on the tail chlorine distribution panel should be opened immediately. (5) Discharge operation: Since the chlorine produced by chlorohydrogen treatment contains the explosive substance nitrogen trichloride, when the chlorine enters the chlorine liquefier to be liquefied, NCL3 is also condensed and accumulates in the gas-liquid separator and the liquid chlorine storage tank; it should be discharged regularly. a) The drain pump should be in good condition and ready for use, with no pressure inside it. b) 30% NaOH that has evaporated on its own is added to the wastewater treatment tank, and tap water is poured in by opening the tap water valve to prepare an alkaline solution with a concentration of around 10%. c) When draining the gas-liquid separator: close all valves at the inlet and outlet of the drain device, and open the drain valve of the gas-liquid separator. d) Carefully and slowly open the waste inlet valve on the sewage discharger; do not do so too quickly to prevent a large amount of liquid chlorine from entering. When the pressure of the drain pump equals the system pressure, or when the frost layer on the drain pump reaches 10 cm, it is considered that the draining is complete, and the drain valve at the bottom of the gas-liquid separator is closed. e) Open the valve connecting the sewage ejector to the sewage treatment tanks, ensuring that both tanks are unobstructed. Utilize the pressure generated by the natural heating of liquid chlorine, which causes it to vaporize, to force the waste contained in the ejector into the two sewage treatment tanks, where it can be neutralized with an alkaline solution. f) Determine whether the waste in the sewage ejector has been completely removed by checking the reading on the pressure gauge of the ejector; once it has been removed, close the valve connecting the ejector to the sewage treatment tank, as well as the inlet valve of the ejector. g) After NCI3 has been completely decomposed, the waste is discharged. h) The disposal procedures for the NCL3 waste accumulated in the liquid chlorine tank are the same as those for the waste disposal from the aforementioned gas-liquid separator, so they will not be repeated here. (6) Tank evacuation operation: This is carried out to remove residual chlorine from the tank and replace it with air by creating a vacuum, as it is necessary for tasks such as maintaining or replacing the valves on the tank, in order to prevent chlorine gas from leaking out. a) In connection with chlorine-hydrogen treatment, open the exhaust valve of the storage tank, as well as the exhaust valve of the tank on the vacuum distribution panel; first exhaust the chlorine from the accident area, and then close the exhaust valve of the tank on the vacuum distribution panel once exhaustion is complete. b) After obtaining consent regarding the packaging, check that all valves of the tank (except the evacuation valve and those that need repair) are closed. Slowly open the evacuation valve of the tank on the vacuum distribution table, maintaining a certain level of vacuum based on the pressure inside the vacuum tank, in order to prevent backpressure from occurring due to too rapid a process. c) Once the storage tank has reached a certain level of vacuum, close the evacuation valve and the additional valves, and inform the packaging staff that the tank evacuation process is complete. (7) Evaporator pumping and its maintenance/cleaning operations: To perform maintenance, cleaning of the evaporator or valve replacement, it is necessary to shut down the unit, drain out the brine, remove any residual chlorine from the chlorine evaporator, and create a vacuum using air to prevent chlorine from leaking out. After that, the evaporator is cleaned, maintained, or its valves are replaced. a) Close all valves on the gas-liquid separator and the liquefier, drain the gas-liquid separator to remove all liquid chlorine. The gas-liquid separator and liquefier are connected in series to create a vacuum. b) Once a certain degree of vacuum is achieved in the separator, close the pumping valve and inform that the liquefier has been pumped out. c) Remove the end caps of the liquefier and use a high-pressure water gun to clean each tube inside until it is clear of any debris. d) Reinstall the end caps on both ends of the liquefier after maintenance, fit all connection valves and pipes, and then conduct a pressure test; no leaks indicate that the maintenance is successful. (8) Procedures for handling accidental chlorine leaks: The exhaust fans in the liquid chlorine section are used to draw out the chlorine gas leaking from various locations such as the pit where the shielded pumps are located, the enclosed areas of the storage tanks, and the liquid-ring chlorine pump room; this extracted chlorine gas is then sent to the chlorine-hydrogen treatment section for further processing. a) When there is valve damage, pipe cracking, or significant chlorine leakage at the connection flanges, turn on the fan and then direct the air duct at the location of the leakage. At the same time, immediately notify the hydrogen chloride treatment team to handle the chlorine-related accident properly. b) The operator should immediately put on protective clothing and an oxygen mask or gas mask, then inform the branch plant and the dispatch team to prepare for repairing the equipment with chlorine leaks. c) There must be supervisors present near the site where the operators are carrying out emergency repairs, ready to replace or rescue those who have been poisoned at the accident site at any time.

Table of Contents Chapter 1: Overview of the Plant------------------------------------------------------------------------3 Section 1: Introduction to the Unit----------------------------------------------------------------------------------------3 1. Working principle of centrifugal compressors--------------------------------------------------------------------------------3 2. Surge phenomenon in centrifugal compressors and preventive measures--------------------------------------------------------------3 3. Critical speed of centrifugal compressors-----------------------------------------------------------------------------4 4. Structure of centrifugal compressors-----------------------------------------------------------------------------------4 5. Working principle of steam turbines---------------------------------------------------------------------------------------5 Section 2: Brief description of the process flow-----------------------------------------------------------------------------------5 1. Description of the CO2 process------------------------------------------------------------------------------5 2. Description of the steam process---------------------------------------------------------------------------------------------6 Section 3: Scope of process simulation-----------------------------------------------------------------------------------6 Chapter 2: List of main equipment-----------------------------------------------------------------------7 Chapter 3: Normal operating parameters-----------------------------------------------------------------8 Chapter 4: Process alarms and interlock systems--------------------------------------------------------------9 1. Explanation of process alarms and interlocks------------------------------------------------------------------------------------9 2. Trigger values for process alarms and interlocks---------------------------------------------------------------------------------10 Chapter 5: Process operation procedures-----------------------------------------------------------------------11 Section 1: Cold start-up-------------------------------------------------------------------------------------------11 Section 2: Normal shutdown-------------------------------------------------------------------------------------------15 Chapter 6: List of accidents-----------------------------------------------------------------------------16 Chapter 7: Simulation DCS interface---------------------------------------------------------------------19 Chapter 1: Overview of the Plant Section 1: Introduction to the Unit The CO2 compressor unit is used to compress the raw material gas, CO2, from the ammonia synthesis plant, and send it to the subsequent urea synthesis stage. It employs a four-stage centrifugal compressor driven by a steam turbine. Its unit mainly consists of a compressor main body, a drive machine, a lubricating oil system, a control oil system, and an anti-surge device. 1. Working principle of centrifugal compressors: The working principle of centrifugal compressors is similar to that of centrifugal pumps. Gas flows into the impeller from the center; under the action of the rapidly rotating impeller, it rotates at high speed along with the impeller and is thrown outward in a radial direction. The impeller rotates driven by the driving machinery, and transfers the resulting mechanical energy to the gas flowing past it through the impeller; in other words, the centrifugal compressor does work on the gas via the impeller. On the one hand, the gas experiences a centrifugal force due to rotation, which increases its own pressure; on the other hand, it gains a large amount of kinetic energy. After the gas leaves the impeller, this portion of kinetic energy can be converted into pressure energy as it passes through the diffuser and the return bend, further increasing the pressure of the gas. In centrifugal compressors, the increase in pressure of the gas after being compressed by an impeller is limited. Therefore, when a higher pressure rise is required, multiple stages of impellers are typically used to compress the fluid one after another in sequence, until the outlet of the final stage reaches the desired pressure. The more impellers a compressor has, the greater the total pressure head it can generate. The temperature of the gas rises after compression. When a high degree of compression is required, the gas is often compressed to a certain pressure and then drawn out of the cylinder, cooled in an external cooler, and subsequently fed back in for further compression. In this way, the compressor is divided into several sections based on the number of cooling cycles, with each section being either one stage or multiple stages. 2. Surge phenomenon in centrifugal compressors and preventive measures. Surge in centrifugal compressors is an abnormal condition that occurs due to improper operation or an insufficient flow rate of the inlet gas. When the flow rate of the incoming gas is reduced to an inappropriate level, the velocity of the gas as it enters the impeller becomes too low; the gas no longer flows along the impeller, and a large vortex region forms on the back side of the blades. This vortex region may even fill the entire blade passage, blocking it off, so that the gas can only swirl within this vortex area and cannot flow out. At this point, the gas in the system flows back from the compressor outlet into the compressor, temporarily compensating for the insufficient amount of gas entering the compressor. Although the compressor seems to have resumed normal operation and started compressing gas again, once the gas is compressed, the aforementioned backflow phenomenon occurs again due to the ongoing shortage of incoming gas. Such airflow that alternates between suction and expulsion at the outlet causes low-frequency, high-amplitude fluctuations in the airflow within the outlet duct, which quickly affect the impellers at all stages; as a result, the entire compressor generates noise and vibration. This phenomenon is known as surge. Surge is very detrimental to machinery; excessive vibration can cause localized overheating, and over time it may even lead to serious accidents such as the destruction of the impeller. When surge occurs, efforts should be made to immediately increase the inlet gas flow rate. The method involves using an anti-surge device to return a portion of the gas at the compressor outlet back to the compressor inlet through a bypass valve, or opening the outlet vent valve to reduce the outlet pressure. 3. Critical speed of centrifugal compressors: Due to manufacturing reasons, the center of gravity and the geometric center of the compressor rotor often do not coincide, which results in a periodically varying centrifugal force during rotation. The magnitude of this force is related to the precision of manufacturing, while its frequency is the speed of rotation of the rotor. If the frequency of the centrifugal force coincides with the natural frequency of the shaft, intense vibrations occur due to resonance, which can severely damage the machine in serious cases. This rotational speed is known as the critical speed of the shaft. There is more than one critical speed; therefore, they are referred to as the first critical speed, the second critical speed, and so on. The compressor rotor cannot operate at speeds close to its critical speeds. The normal operating speed of a conventional centrifugal pump is lower than its first critical speed; such a shaft is called a rigid shaft. The operating speed of a centrifugal compressor is usually higher than the first critical speed and lower than the second critical speed; such a shaft is referred to as a flexible shaft. To prevent vibration, centrifugal compressors must quickly exceed their critical speed during startup and shutdown. 4. Structure of centrifugal compressors A centrifugal compressor consists of two main parts: the rotor and the stator. The rotor consists of components such as the main shaft, impeller, shaft sleeve, and balance disk. All rotating components are mounted on the main shaft; except for the shaft sleeves, the other components are fixed to the main shaft using keys. The spindle is mounted on radial bearings to facilitate rotation. The impeller is the main component of a centrifugal compressor, and it is equipped with several blades used to compress gas. As the gas is compressed by the blades, its pressure increases; as a result, the gas pressure acting on each side of the blades differs, generating an axial thrust directed toward the low-pressure side. This thrust can cause the rotor to move toward the low-pressure side, and in severe cases, it can lead to friction and collision between the rotor and the stator. To eliminate axial thrust, a balance disc and a thrust bearing are installed on the outside of the high-pressure side. One side of the balance disc is in contact with high-pressure gas, while the other side is in contact with low-pressure gas; the thrust generated by the pressure difference between the two sides is used to balance the axial thrust. The stator of a centrifugal compressor consists of components such as the cylinder, diffuser chamber, bend, return vessel, partition, seals, and bearings. Cylinders, also known as housings, come in two types: horizontally split and vertically split. Horizontal splitting involves dividing the enclosure into upper and lower parts, with the upper cover being removable; this design is commonly used in low-pressure applications. A vertical split structure is a tubular design, consisting of a cylindrical body and end caps, and is commonly used in high-pressure applications. There are several partitions inside the cylinder, which separate the blades and form diffusers, bends, and recirculators. To prevent cross-ventilation between stages or leakage to the outside, inter-stage seals and shaft seals are provided. The auxiliary equipment of a centrifugal compressor includes intercoolers, gas-liquid separators, and oil systems. 5. Working principle of the turbine A turbine, also known as a steam turbine, is a rotary prime mover that uses steam to generate power. The high-pressure, high-temperature steam entering the turbine is ejected through nozzles; after expansion and pressure reduction, the resulting high-speed airflow pushes against the moving blades on the turbine rotor in a specific direction, causing the rotor to rotate at a constant speed and thus converting the energy of the steam into mechanical energy. Due to different methods of energy conversion, turbines are divided into impulse and reaction types. In the impulse type, steam expands only within the nozzle, and the moving blades are subjected only to the force of the high-speed airflow. In reaction turbines, steam expands not only in the nozzles but also within the blades; the moving blades are subjected to both the force exerted by the high-speed airflow and the reaction force generated by the expansion of steam within the blades. Depending on the number of impeller stages in the turbine, it can be divided into single-pole or multi-pole types. Based on different thermodynamic processes, steam turbines can be classified into back-pressure type, condensing type, and extraction-condensing type. In a back-pressure steam turbine, the steam does work through expansion and is then discharged from the turbine at a certain temperature and pressure, where it can be used again in the process ； After expanding to perform work, the inlet air of the condensing steam turbine is entirely discharged into the condenser where it condenses into water ； In an exhaust-condensation type turbine, as steam expands to perform work, a portion of it is drawn off in the middle for other uses, while the remaining part continues to do work inside the cylinder before being discharged to the condenser to be condensed. Section 2: Brief Description of the Process Flow 1. Explanation of the CO2 process: The raw gas CO2 coming from the ammonia synthesis unit has a pressure of 150 Kpa (A) and a temperature of 38°C; its flow rate is measured by FR8103. It enters the first-stage separator V-111 of the CO2 compressor, where the liquid droplets contained in the CO2 gas phase are separated off. After that, it proceeds to the inlet of the first stage of the compressor. Following compression in this stage, the CO2 pressure rises to 0.38 Mpa (A) and the temperature reaches 194°C. The gas then enters the first-stage cooler E-119, where it is cooled to 43°C using circulating water. To ensure an adequate supply of oxygen for corrosion prevention in the urea production unit, an appropriate amount of air from the ammonia synthesis unit is added before the CO2 enters E-119; the flow rate of this air is controlled by FRC-8101. The oxygen content in the CO2 gas is maintained between 0.25% and 0.35%. After the liquid droplets are separated in separator V-111, the gas proceeds to the second stage of compression. At the exit of the second stage, the CO2 pressure is 1.866 Mpa (A) and the temperature is 227°C. It then enters the second-stage cooler E-120 where it is cooled to 43°C; after the droplets are removed via the second-stage separator V-120, it proceeds to the third stage. Inter-segment vent valves are provided at the entrances of the three sections. It facilitates CO2 pressure control and rapid pressure release in the low-pressure cylinder; after being compressed in three stages, the CO2 reaches a pressure of 8.046 Mpa(A) and a temperature of 214°C, after which it enters the three-stage cooler E-121 for cooling. To prevent the formation of dry ice due to excessive cooling of CO2, a temperature control valve TV-8111 is installed on the cooling water return line of the third-stage cooler; this valve is used to maintain the CO2 temperature at the inlet of the fourth stage between 50–55°C. The cooled CO2 undergoes four stages of compression, during which its pressure rises to 15.5 Mpa(A) and its temperature reaches 121°C, after which it enters the high-pressure urea synthesis system. To prevent overpressure and surge in the high-pressure cylinder of the CO2 compressor, a four-way one-valve HV-8162 (i.e., HIC8162) is installed on the fourth-stage outlet pipeline. 2. Steam flow description: The main steam pressure is 5.882 Mpa, the temperature is 450°C, and the flow rate is 82 t/hr. This steam enters the turbine to generate power; a large portion of it is extracted from the middle section of the turbine. The extraction steam has a pressure of 2.598 Mpa, a temperature of 350°C, and a flow rate of 54.4 t/hr, and it is sent to the frame. Another portion of the steam passes through the medium-pressure control valve and continues to work inside the turbine cylinder. After performing its function, the waste steam enters the steam condensation system. Section 3: Scope of Process Simulation 1. Process scope: Carbon dioxide compression, turbines, oil system. 2. Boundary conditions: All utility systems such as water, electricity, steam, and air are in normal and stable conditions. 3. On-site operation: Valves, machines, pumps, etc. that are operated manually on-site are designed according to the requirements of startup, shutdown, and emergency scenarios. The shut-off valves before and after the control valve are not simulated. Chapter 2 List of Main Equipment 1. CO2 gas circuit system: E-119, E-120, E-121, V-111, V-119, V-120, V-121, K-101. 2. Steam turbine and oil system: DSTK-101, oil tank, oil temperature controller, oil pump, oil cooler, oil filter, barring oil pump, pressure regulator, quick shut-off valve, governor, pressure regulator. 3. Equipment Description (E: Heat Exchanger; V: Separator) Piping Diagram Tag Numbers Main Equipment U8001 E-119 (CO2 First-Stage Cooler), E-120 (CO2 Second-Stage Cooler), E-121 (CO2 Second-Stage Cooler), V-111 (CO2 First-Stage Separator), V-120 (CO2 Second-Stage Separator), V-121 (CO2 Third-Stage Separator) DSTK-101 (CO2 Compressor Unit Turbine) U8002 DSTK-101 Oil Tank, Oil Pump, Oil Cooler, Oil Filter, Turning Gear Oil Pump 4. List of Main Control Valves Tag Number Description Piping Diagram Tag Number FRC8103 Air Flow Control U8001 LIC8101 V111 Level Control U8001 LIC8167 V119 Level Control U8001 LIC8170 V120 Level Control U8001 LIC8173 V121 Level Control U8001 HIC8101 Interstage Vent Valve U8001 HIC8162 Four-in-One Anti-Surge Valve U8001 PIC8241 Fourth-Stage Outlet Pressure Control U8001 HS8001 Turbine Steam Quick-Shut Valve U8002 HIC8205 Throttle Valve U8002 PIC8224 Extracted Medium-Pressure Steam Pressure Control U8002 Chapter 3 Normal Operating Process Parameters Table Tag Number Measurement Point Location Normal Value Unit Remarks TR8102 CO2 Feed Gas Temperature 40 ℃ TI8103 CO2 Compressor First-Stage Outlet Temperature 190 ℃ PR8108 CO2 Compressor First-Stage Outlet Pressure 0.28 MPa (G) TI8104 CO2 Compressor First-Stage Cooler Outlet Temperature 43 ℃ FRC8101 Second-Stage Air Addition Flow 330 Kg/h FR8103 CO2 Inlet Flow 27000 Nm3/h FR8102 Third-Stage Outlet Flow 27330 Nm3/h AR8101 Oxygen Content 0.25~0.3 % TE8105 CO2 Compressor Second-Stage Outlet Temperature 225 ℃ PR8110 CO2 Compressor Second-Stage Outlet Pressure 1.8 Mpa (G) TI8106 CO2 Compressor Second-Stage Cooler Outlet Temperature 43 ℃ TI8107 CO2 Compressor Third-Stage Outlet Temperature 214 ℃ PR8114 CO2 Compressor Third-Stage Outlet Pressure 8.02 Mpa (G) TIC8111 CO2 Compressor Third-Stage Cooler Outlet Temperature 52 ℃ TI8119 CO2 Compressor Fourth-Stage Outlet Temperature 120 ℃ PIC8241 CO2 Compressor Fourth-Stage Outlet Pressure 15.4 Mpa (G) PIC8224 Turbine Medium-Pressure Steam Outlet Pressure 2.5 Mpa (G) Fr8201 Turbine Steam Inlet Flow 82 T/h FR8210 Turbine Medium-Pressure Steam Outlet Flow 54.4 t/h TI8213 Turbine Medium-Pressure Steam Outlet Temperature 350 ℃ TI8338 CO2 Compressor Oil Cooler Outlet Temperature 43 ℃ PI8357 CO2 Compressor Oil Filter Outlet Pressure 0.25 MPa (G) PI8361 CO2 Control Oil Pressure 0.95 MPa (G) SI8335 Compressor Speed 6935 rpm *8001 Compressor Vibration 0.022 mm GI8001 Compressor Shaft Displacement 0.24 mm Chapter 4 Process Alarm and Interlock System 1. Process Alarm and Interlock Description: To ensure the normal operation of the process and equipment and prevent accidents, detection devices are installed at key locations on the equipment, and alarm lights are provided on the auxiliary control panel to give warnings, enabling timely action to eliminate potential accidents. Process interlock is a self-protection system that activates when the equipment is not operating properly. This unit features two interlock-based self-protection measures: A: Compressor vibration excess-high interlock (surge occurrence): Action: After 20 seconds (primarily to facilitate handling by trainees), the following actions are automatically carried out: Close the turbine emergency shut-off valve HS8001, the speed control valve HIC8205, and the medium-pressure steam pressure control valve PIC8224 ； Handling of the fully open anti-surge valve HIC8162 and the inter-stage vent valve HIC8101: Press the RESET button on the auxiliary control panel, and initiate restart by starting the pipe warming process during cold start-up. B: Low oil pressure interlock: Action: The following operations are carried out automatically: Close the turbine emergency shut-off valve HS8001, the speed control valve HIC8205, and the medium-pressure steam pressure control valve PIC8224 ； Handling of the fully open anti-surge valve HIC8162 and the inter-stage vent valve HIC8101: Identify and address the cause of the low oil pressure, then press the RESET button on the auxiliary control panel to restart the oil system during cold start-up. 2. Process alarms and interlock trigger values: Tag Number, Detection Point, Trigger Value – PSXL8101: V111 pressure ≤0.09 Mpa; PSXH8223: Steam turbine back pressure ≥2.75 Mpa; LSXH8165: V119 liquid level ≥85%; LSXH8168: V120 liquid level ≥85%; LSXH8171: V121 liquid level ≥85%; LAXH8102: V111 liquid level ≥85%; SSXH8335: Compressor speed ≥7200 rpm; PSXL8372: Control oil pressure ≤0.85 Mpa; PSXL8359: Lubricating oil pressure ≤0.2 Mpa; PAXH8136: CO2 fourth-stage outlet pressure ≥16.5 Mpa; PAXL8134: CO2 fourth-stage outlet pressure ≤14.5 Mpa; SXH8001: Compressor shaft displacement ≥0.3 mm; SXH8002: Compressor radial vibration ≥0.03 mm. Vibration interlock: *8001≥0.05 mm or GI8001≥0.5 mm (triggers after 20 seconds). Oil pressure interlock: PI8361≤0.6 Mpa. Auxiliary oil pump auto-start interlock: PI8361≤0.8 Mpa. Chapter 5: Process Operating Procedures Section 1: Cold Start-up Preparation: Introducing circulating water: The compressor operator at E119 opens the circulating water valve OMP1001 to introduce circulating water ； At the compressor station E120, open the circulating water valve OMP1002 to introduce circulating water ； At the compressor station E121, open the circulating water valve TIC8111 to introduce circulating water ； Starting of the CO2 compressor oil system: Activate the oil tank temperature controller on the auxiliary control panel to raise the oil temperature to around 40 degrees ； Open the front shut-off valve OMP1026 of the oil pump ； Open the rear shut-off valve OMP1048 of the oil pump ； Start the main oil pump OIL PUMP from the auxiliary control panel ； Adjust the valve TMPV186 in the oil pump circuit to keep the control oil pressure above 0.9 Mpa ； Crank rotation: Open the front isolation valve OMP1031 of the crank pump ； Activate the rear shut-off valve OMP1032 of the crank pump ； Start the turning pump from the auxiliary control panel ； Press the crank button on the auxiliary control panel to crank the shaft until the speed exceeds 150 rpm ； Check the compressor for any abnormal noises, and examine vibration, shaft displacement, etc ； Stop cranking: Press the cranking button on the auxiliary control panel to stop cranking ； Stop the pump from the auxiliary control panel ； Close the rear isolation valve OMP1032 of the turning pump ； Close the front isolation valve OMP1031 of the cranking pump ； Interlock test: Oil pump auto-start test. After the main oil pump starts and the oil pressure is brought under control, press the button to automatically start the auxiliary oil pump on the auxiliary control panel. Press the RESET button, open the turbine steam quick-shut valve HS8001, then stop the main oil pump on the auxiliary control panel; the auxiliary oil pump should start automatically, and the interlocks should not activate. Low oil pressure interlock test: After the main oil pump starts and the oil pressure is brought under control, verify that the auxiliary oil pump has not been set to start automatically on the auxiliary control panel. Press the RESET button, open the turbine steam quick shut-off valve HS8001, and close the four-in-one valve as well as the inter-stage vent valves. Slowly reduce the oil pressure through the oil pump circuit valves; when the oil pressure drops to a certain level, the gauge PSXL8372 should trigger an alarm. After confirming this, continue to increase the valve opening to further reduce the oil pressure, and check whether the interlock function activates. Once it activates, the turbine steam quick shut-off valve HS8001 should close, while the four-in-one valve and the inter-stage vent valves should be fully open. Parking test: After the main oil pump starts and the oil pressure is under normal control, press the RESET button. Open the turbine steam quick-shut valve HS8001, and close the four-in-one valve as well as the inter-stage vent valves. Press the STOP button on the auxiliary control panel; the turbine steam quick-shut valve HS8001 should close, while the four-in-one valve and the inter-stage vent valves should be fully open. Warm-up of pipes and machinery: Click the automatic start button for the auxiliary oil pump on the auxiliary control panel to set the auxiliary oil pump to start automatically ； Open the steam bypass valve OMP1006 in the inlet area to prepare for steam introduction ； Open the isolation valve OMP1007 on the main steam pipeline of the steam turbine to warm up the compressor ； Open the CO2 vent shut-off valve TMPV102 ； Open the CO2 refrigerant control valve PIC8241 ； Once the steam pressure in the turbine inlet pipeline rises to 5.0 MPa, open the inter-zone steam valve OMP1005 ； Close bypass valve OMP1006 ； Open the CO2 feed main valve OMP1004 ； Fully open CO2 inlet control valve TMPV104 ； Open the turbine extraction isolation valve OMP1009 ； Press the RESET button on the auxiliary control panel to prepare for starting the compressor ； Open the turbine emergency shut-off valve HS8001 ； Gradually open valve HIC8205 and increase the speed of SI8335 to 1000 rpm for low-speed warm-up ； Set the rotation speed to 1000 and warm up for 15 minutes (simulated as 2 minutes) ； Open the oil cooler cooling water valve TMPV181 ； Once warming up is complete, gradually increase the unit’s speed to 2000 rpm and check its operation ； Check the compressor for any abnormal noises, and examine vibration, shaft displacement, etc ； Control the rotation speed at 2000, and stay for 15 minutes (simulated as 2 minutes) ； Beyond critical speed: Continue to increase the HIC8205 setting, gradually raising the unit’s speed to 3000 rpm in order to reach beyond the critical speed range (3000–3500 rpm) ； Continue to increase the HIC8205 setting, and use 20–30 seconds to slowly raise the unit’s speed to 4000 rpm, passing through the critical speed ； Gradually increase the PIC8224 to 50% ； Slowly reduce the inter-segment vent valve HIC8101 to 72% ； Set the V111 level control LIC8101 to automatic mode, with the set value around 20% ； Set the V119 level control LIC8167 to automatic mode, with a set point around 20% ； Set the V120 level control LIC8170 to automatic mode, with a setpoint around 20% ； Set the V121 level control LIC8173 to automatic mode, with a setpoint around 20% ； Set TIC8111 to automatic mode with a setpoint of around 52 degrees ； Increase speed and voltage: Continue to increase the setting of HIC8205 in order to slowly raise the unit’s speed to 5500 rpm ； Slowly reduce the inter-segment vent valve HIC8101 to 50% ； Continue to increase the HIC8205 setting, gradually raising the unit’s speed to 6050 rpm ； Slowly reduce the inter-segment vent valve HIC8101 to 25% ； Slowly reduce the flow rate of the four-way one-valve HIC8162 to 75% ； Continue to increase the HIC8205 setting, gradually raising the unit’s rotational speed to 6400 rpm ； Slowly close the inter-segment vent valve HIC8101 ； Slowly close the four-way one-valve HIC8162 ； Continue to increase the HIC8205 setting, gradually raising the unit’s speed to 6935 rpm ； Adjust the HIC8205 to stabilize the unit speed SI8335 at 6935 rmp ； Feed: Gradually reduce the PIC8241 setting, and slowly increase the pressure at the fourth stage outlet of the compressor to 14.4 MPa in order to balance the pressure in the synthesis system ； Open the CO2 outlet valve OMP1003 ； Continue to manually reduce the setting of the PIC8241, and slowly increase the pressure at the fourth outlet of the compressor to 15.4 MPa, then introduce CO2 into the synthesis system ； Once the PIC8241 control stabilizes at around 15.4 MPa, set it to 15.4 and switch to automatic mode ； Section 2: Normal Shutdown – Shutdown of the CO2 compressor: Adjust HIC8205 to reduce the speed to 6500 rpm ； Adjust HIC8162 to reduce the load to 21,000 Nm3/h ； Continue to adjust HIC8162, as well as the amount of steam extracted and injected, until HIC8162 is fully open ； Manually and slowly open the PIC8241 to reduce the pressure at the four outlet points to below 14.5 MPa, allowing CO2 to leave the synthesis system ； Close the CO2 inlet main valve to the synthesis system OMP1003 ； Continue to increase the PIC8241 setting in order to slowly reduce the pressure at the four outlet stages to 8.0–10.0 Mpa ； Adjust the HIC8205 to reduce the speed to 6403 rpm ； Continue adjusting the HIC8205 to reduce the speed to 6052 rpm ； Adjust the HIC8101 to reduce the outlet pressure of the four sections to 4.0 Mpa ； Continue adjusting the HIC8205 to reduce the speed to 3000 rpm ； Continue adjusting the HIC8205 to reduce the speed to 2000 rpm ； Press the STOP button on the auxiliary control panel to stop the compressor ； Close the CO2 inlet compressor control valve TMPV104 ； Close the main CO2 inlet valve to the compressor, OMP1004 ； Close the steam extraction main valve to MS OMP1009 ； Close the main steam valve OMP1005 to the compressor section ； Close the compressor steam inlet valve OMP1007 ； Oil system shutdown: Disable the automatic start-up of the auxiliary oil pump from the auxiliary control panel ； Shut down the main oil pump from the auxiliary control panel ； Close oil pump inlet valve OMP1048 ； Close oil pump outlet valve OMP1026 ； Close the oil cooler cooling water valve TMPV181 ； Stop oil temperature control from the auxiliary control panel ； Chapter 6: List of Incidents I. Excessive compressor vibration: Causes: Mechanical issues such as bearing wear, damaged balance disk seals, poor alignment, shaft bending, loose couplings, and other problems related to the equipment itself ； Due to issues with speed control, the unit operates near its critical speed, resulting in resonance ； The reason related to process control is mainly computer surge caused by improper operation. Treatment measures: (In the simulation, there is only 20 seconds for processing; if it is not done in time, an interlock shutdown will occur.) ) Mechanical failures require shutdown for maintenance ； When resonance occurs, it is necessary to change the operating speed; furthermore, during startup and shutdown, the critical speed should be passed as quickly as possible ； When the compressor experiences surge, identify the cause of the surge and take appropriate measures: I. Insufficient inlet flow rate: Open the anti-surge valve HIC8162 and increase the opening degree of the inlet control valve ； Ⅱ. Excessive outlet pressure: Open the anti-surge valve HIC8162 and increase the opening degree of the fourth-stage outlet discharge control valve ； Ⅲ. Improper operation, excessive movement of the valves: Open the anti-surge valve HIC8162 to eliminate surge, and then operate it carefully. Preventive measures: 1. Centrifugal compressors are generally equipped with vibration detection devices, which should be checked regularly during operation. If excessive shaft vibration or displacement is detected, the cause should be analyzed and addressed promptly. 2. Surge prevention: Regular attention should be paid to changes in the compressor’s air volume to prevent surge caused by an excessively low inlet air volume. When driving the machine, it is necessary to follow the principle of \"increasing speed first before raising pressure\". First, open the anti-surge valve; once the speed reaches a certain level, gradually close the anti-surge valve to raise the outlet pressure to a specified value. After that, increase the speed again, proceeding in an alternating manner of increasing speed and raising pressure until the process requirements are met. When stopping the machine, it is necessary to follow the principle of \"reducing pressure first by reducing speed\": first open the anti-surge valve slightly to lower the outlet pressure to a certain level, then reduce the speed; this process of reducing speed and pressure should be repeated until all pressure has been released before shutting down the machine. II. Automatic start of the compressor auxiliary oil pump: Reason: The automatic start of the auxiliary oil pump is a safety measure taken as a result of low oil pressure. Generally, it is caused by one of the following two reasons: 1. The filter at the outlet of the oil pump is clogged, 2. The opening degree of the valve in the oil pump circuit is too large. Remedial action: Close the oil pump circuit valve ； Clean the oil filter according to the filter cleaning procedure ； Stop the auxiliary oil pump from the auxiliary control panel. Preventive measures: The proper operation of the oil system is an essential guarantee for the proper functioning of the compressor. Therefore, the compressor’s oil system is equipped with various monitoring devices such as those for oil temperature, oil pressure, filter pressure drop, and oil level. These parameters need to be checked regularly during production, and the oil filters should be replaced and cleaned on a regular basis. The outlet pressure at stages 3 and 4 is low, and the amount of CO2 injected is insufficient: Reason: The compressor speed is low ； The anti-surge valve is not fully closed ； The pressure control valve PIC8241 is not set to automatic mode, or it is not fully closed. Action to take: Adjust the speed to 6935 rpm ； Close the anti-surge valve ； Close the pressure control valve PIC8241. Preventive measures: The outlet pressure at the fourth stage of the compressor is closely related to the system pressure in the subsequent stage; fluctuations in the system pressure of the next stage can also cause fluctuations in the outlet pressure at the fourth stage, which in turn affects the compressor’s air handling capacity. Therefore, during production, the system pressure in the subsequent stage should be kept stable. It is also necessary to regularly check the suction flow rate, rotation speed of the compressor, as well as the opening degrees of the discharge valve, anti-surge valve, and inter-stage vent valves. Under normal operating conditions, these three valves should remain closed as much as possible to ensure the compressor operates at its highest efficiency. IV. Compressor trips due to surge interlock. Cause: Improper operation resulted in surge in the compressor, and no timely action was taken ； Action taken: Close the main CO2-to-urea synthesis valve OMP1003 ； Press the RESET button on the auxiliary control panel ； Restart the operation by following the pipe warming and warm-up procedure for cold start. Preventive measures: Prevent surge from occurring by following the preventive measures for excessive vibration; once surge occurs, take appropriate action promptly by opening the anti-surge valve. V. The outlet temperature of the compressor’s three-stage cooler is too low. Reason: The cooling water control valve TIC8111 is not set to automatic mode, and its opening degree is too large ； Remedial measures: 1. Reduce the cooling water control valve TIC8111 to keep the temperature around 52 degrees ； 2. After the control stabilizes, set TIC8111 to 52 degrees and switch to automatic mode. Precautions: At high pressures and low temperatures, carbon dioxide can precipitate as solid dry ice, which can damage the compressor impeller and affect its proper operation. Therefore, it is necessary to regularly check the temperature at this point during compressor operation to keep it within the normal operational range. Chapter 7 Simulation DCS Screens: U8001 DCS Diagram for the CO2 gas system; U8002 DCS Diagram for the separation and oil system. U8001F – On-site diagram of the CO2 gas system; U8002F – DCS Diagram for the separation and oil system. AUX – Auxiliary control panel: U8001, U8001F, U8002, U8002F, AUX

Refer to the following books: \"Principles of Unit Processes in Petroleum Processing\", published by Sinopec Press; \"Petroleum Refining Engineering\", published by Petroleum Industry Press; as well as reference materials such as plant operation procedures

1. The content is very rich; I’m not sure who the target audience for these teaching materials is? 2. Chapter 3 is about flow meters; is its content repetitive with some parts of Chapter 1?

Who is the original poster? Writing books is amazing!

Is it aimed at what kind of learners? Is it an organizational structure based on the work process? If review is needed, I’ll handle it

My elder brother is truly amazing; compiling books is such a monumental task. It reminds me of Sima Qian who wrote the Records of the Grand Historian, and Ban Gu who wrote the History of the Han Dynasty. . . . . I’m currently reading this great work; it contains unit operations that I am familiar with, and I will definitely upload the relevant materials for your reference! Amazing!

That’s terrifying. The table of contents is so long. It can be used as a dictionary.

1. The content and difficulty level of the book will vary depending on the target audience. I’m not sure what audience this book is intended for, so I can’t discuss its specific content. II. The table of contents does indeed seem too long. Some chapters can definitely be combined; for example, Chapters 8, 9, and 18 can be merged into one chapter, as they all deal with absorption operations, which can then be further divided into several sub-items. 2, 4, 15, and 16 can also be combined. Chapters can be divided based on unit operations; identical unit operations form one chapter, which is then further subdivided. III. The operation of the instruments can be covered in a chapter on unit operations involving pressure, flow rate, and temperature measurements, without the need for a separate chapter. IV. The title of the book is \"Unit Processes and Operations in Chemical Engineering\", but the contents of chapters 25 and 26 deal with unit operations, which does not match the title; should it be changed? V. Based on the content of the simulation chapter you shared, the simulation should be based on Dongfang Simulation’s training materials; therefore, it is sufficient to incorporate their operation manuals into the content. Additionally, referring to the book \"Guidelines for Chemical Engineering Simulation Training\" can also be helpful. VI. The content of the practical training can be found in “Practical Training in Chemical Unit Operations”; different versions are available for various audiences.

That’s great; I’ve learned so much. Thank you!

The original poster can refer to the three-volume series, namely Volume 1, Volume 2, and Volume 3, of the \"Handbook on Design of Chemical Unit Operations\"