Podcast
Questions and Answers
Explain how the removal of the heat of compression in E-120A/B contributes to the overall efficiency of the C-120A/B compressors, detailing the thermodynamic principles involved.
Explain how the removal of the heat of compression in E-120A/B contributes to the overall efficiency of the C-120A/B compressors, detailing the thermodynamic principles involved.
Removing heat reduces the gas volume, decreasing the work needed for compression in the subsequent stage. This aligns with the principles of thermodynamics, specifically minimizing energy input for a given compression ratio, thereby increasing efficiency.
If E-120A/B's cooling water flow is severely reduced, what specific operational challenges could arise in C-120A/B, and how might these manifest in downstream processes?
If E-120A/B's cooling water flow is severely reduced, what specific operational challenges could arise in C-120A/B, and how might these manifest in downstream processes?
Reduced cooling can lead to higher discharge temperatures in the first stage, potentially exceeding material limits, reducing compressor efficiency, and causing heavier components to remain in the vapor phase, which can foul downstream reactors.
Describe the potential consequences if T-340, which receives heavier components from D-120A/B, malfunctions or becomes overwhelmed. How could this affect the Charge Gas Compressors and downstream reactors?
Describe the potential consequences if T-340, which receives heavier components from D-120A/B, malfunctions or becomes overwhelmed. How could this affect the Charge Gas Compressors and downstream reactors?
If T-340 malfunctions, heavier components might carry over to the 2nd stage of C-120A/B and subsequently to the reactors (R-201-205), leading to fouling, catalyst deactivation, reduced reactor efficiency, and potential equipment damage from the introduction of unwanted substances.
Explain the purpose of the multiple suction and discharge bottles (D-121A/B-1 through D-121A/B-8) connected to the Charge Gas Compressors. What advantages do these bottles provide for the compression process?
Explain the purpose of the multiple suction and discharge bottles (D-121A/B-1 through D-121A/B-8) connected to the Charge Gas Compressors. What advantages do these bottles provide for the compression process?
Based on the process description, propose a modification to the system to improve the separation efficiency of heavier components in D-120A/B, justifying your suggestion with thermodynamic or process principles.
Based on the process description, propose a modification to the system to improve the separation efficiency of heavier components in D-120A/B, justifying your suggestion with thermodynamic or process principles.
Flashcards
C-120A/B Function
C-120A/B Function
Compress ethylene vapor to the high pressure required for feeding into the reactors.
E-120A/B (Charge Gas Interstage Coolers) Function
E-120A/B (Charge Gas Interstage Coolers) Function
Cool ethylene vapor after the 1st stage of compression, removing heat to maintain a constant 2nd stage temperature.
D-120A/B (Charge Gas Interstage K.O. Drums) Function
D-120A/B (Charge Gas Interstage K.O. Drums) Function
Separate trace heavier components from the ethylene vapor after the interstage cooling.
Why is heat removed?
Why is heat removed?
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D-121A/B Vessels Function
D-121A/B Vessels Function
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Study Notes
Charge Gas Compressors
- Ethylene vapor from D-110 overhead is compressed to high pressure for reactor feed in the Compression Section
- Ethylene vapor flows from D-110 overhead to the 1st Stage of C-120A/B.
- Vapor goes into D-121A/B-1 (C-120A/B 1st Stage Suction Bottles #1), then D-121A/B-2 (C-120A/B 1st Stage Suction Bottles #2) before the 1st Stage of C-120A/B.
- Vapor flows into D-121A/B-3 (C-120A/B 1st Stage Discharge Bottles #1), then D-121A/B-4 (C-120A/B 1st Stage Discharge Bottles #2) before exiting the 1st stage.
- Vapor heats up during compression.
- Vapor is routed to the shell side of E-120A/B (Charge Gas Interstage Coolers) and cooled by cooling water on the tube side to remove heat and maintain a constant 2nd stage temperature.
- Removing heat increases the efficiency and reduces horsepower needed to operate C-120A/B.
- Cooled ethylene is routed to D-120A/B (Charge Gas Interstage K.O. Drums).
- Heavier components are separated from the vapor ethylene and routed from the bottom of D-120A/B to T-340.
- Ethylene from the overhead of D-120A/B goes to the 2nd Stage of C-120A/B.
- Vapor flows into D-121A/B-5 (C-120A/B 2nd Stage Suction Bottles #1), then D-121A/B-6 (C-120A/B 2nd Stage Suction Bottles #2) before entering the 2nd Stage of C-120A/B.
- Vapor goes into D-121A/B-7 (C-120A/B 2nd Stage Discharge Bottles #1), then D-121A/B-8 (C-120A/B 2nd Stage Discharge Bottles #2) before exiting the 2nd stage.
- Vapor exits the 2nd stage at sufficient pressure to feed R-201-205 (Reactors).
Equipment Description – Compression
- The following equipment details size, shape, internals, and special features, to provide an idea about relative sizes in the field:
- C-120A/B (Charge Gas Compressors)
- D-121A/B-1 (C-120A/B 1st Stage Suction Bottles #1)
- D-121A/B-2 (C-120A/B 1st Stage Suction Bottles #2)
- D-121A/B-3 (C-120A/B 1st Stage Discharge Bottles #1)
- D-121A/B-4 (C-120A/B 1st Stage Discharge Bottles #2)
- E-120A/B (Charge Gas Interstage Coolers)
- D-120A/B (Charge Gas Interstage K.O. Drum)
- D-121A/B-5 (C-120A/B 2nd Stage Suction Bottles #1)
- D-121A/B-6 (C-120A/B 2nd Stage Suction Bottles #2)
- D-121A/B-7 (C-120A/B 2nd Stage Discharge Bottles #1)
- D-121A/B-8 (C-120A/B 2nd Stage Discharge Bottles #2)
C-120A/B (Charge Gas Compressors)
- Compressors move vapor by raising pressure and reducing volume.
- Compressors function like pumps, but for vapor instead of liquids.
- Vapor movement is for flow through piping or for storage.
- Centrifugal and positive displacement compressors exist for both liquids and vapors.
- A reciprocating compressor uses a tight-fitting piston inside a cylinder.
- As the cylinder draws back, it draws in low-pressure gas.
- As the cylinder moves forward, it compresses the gas.
- Valves open automatically when the piston draws in or exhausts, and close during compression.
- Reciprocating compressors are reliable with less investment and space for installation.
- Reciprocating compressors are optimal for applications requiring frequent starts and stops.
- Reciprocating compressors operate efficiently even at less than full capacity.
- Multi-stage compressors combine multiple compressors onto a single driver shaft.
- Multi-stage compressors are used when a single-stage unit cannot produce the desired pressure to move gas.
- Vapor enters the suction of the 1st stage and is compressed out as 1st stage discharge gas into a KO drum to remove any liquid.
- 1st stage discharge gas then enters the suction of the 2nd stage where it is compressed again and exits.
- C-120 A/B are Dresser-Rand (6WIK-149) horizontally opposed, 325 rpm, 2500 hp multistage reciprocating positive displacement compressors.
- Normal operations runs both compressors in parallel.
- C-120 A/B increase the pressure of the ethylene feed to a pressure high enough to be introduced into R-201-205 as feed.
Reciprocating Compressor Function
- Gas is put under pressure via compression
- Compression: Piston retracts, cylinder fills with gas, piston moves forward to compress the gas until cylinder pressure exceeds discharge pressure.
- Discharge: Cylinder pressure exceeds discharge pressure, forcing the discharge valve to open and pass gas to the receiver until the piston reaches the end of the stroke.
- Expansion: Both valves are closed, the piston moves toward the beginning point, and the pressure decreases to the inlet pressure.
- Intake: The inlet valve opens, the piston completes the intake stroke, creating a partial vacuum allowing gas to move into the cylinder for the next cycle.
D-121A/B-1 (C-120A/B 1st Stage Suction Bottles #1)
- Suction/discharge bottles, also known as pulsation dampeners, dampen pressure pulsations.
- Pulsations are created by the action of compression where suction and discharge valves are open for only part of the compression cycle.
- Reciprocating compressors generate flow pulsations in the suction and discharge lines.
- Pulsations have to be controlled to prevent overloading compressors, avoid vibration in piping, and provide smooth gas flow.
- C-120A/B have pulsation dampeners before and after each cylinder to reduce vibration from the piston rod's reciprocating stroke.
- High vibration can be caused by loose metal support straps, broken concrete support slab, and/or significant oil level in the discharge pulsation dampeners.
- Suction/discharge bottles allow relatively unrestricted flow of gas in one direction.
- Monitor the temperature of the suction and discharge valves on the DCS console to detect valve failure or leaks.
- Ethylene enters the side of D-121A/B-1 and exits the bottom; it is 2’ in diameter and 11’ long.
D-121A/B-2 (C-120A/B 1st Stage Suction Bottles #2)
- Ethylene enters the top of D-121A/B-2 before exiting at the bottom into the 1st stage of compression
- This bottle is 2’ in diameter and 5 ‘ long.
D-121A/B-3 (C-120A/B 1st Stage Discharge Bottles #1)
- Ethylene exits the 1st stage compression and enters the top D-121A/B-3, then exits the side.
- This bottle is 2’ in diameter and 4 ‘ long.
D-121A/B-4 (C-120A/B 1st Stage Discharge Bottles #2)
- Ethylene enters the top D-121A/B-4 and exits the side.
- This bottle is 2’ in diameter and 9 ‘ long.
E-120A/B (Charge Gas Interstage Coolers)
- E-120A/B are shell and tube, U-tube type heat exchangers that cool the ethylene on the shell side with cooling water on the tube side.
- E-120A/B are installed between the 1st and 2nd stages of the compressor.
- E-120A/B's purpose is to remove the heat of compression.
D-120A/B (Charge Gas Interstage K.O. Drums)
- D-120A/B (4’D x 8’2”L) are equipped with internal demister pads installed below the top vapor outlets.
- D-120A/B's purpose is to knock out any entrained liquid in the ethylene that may develop when the ethylene is cooled.
- Ethylene enters on the side of the drums and liquid exits from the bottom of the drums, while vapor exits from the top of the drums.
D-121A/B-5 (C-120A/B 2nd Stage Suction Bottles #1)
- Ethylene enters the side of D-121A/B-5 and exits the bottom
- This bottle is 1’8” in diameter and 13’2” long.
D-121A/B-6 (C-120A/B 2nd Stage Suction Bottles #2)
- Ethylene enters the top of D-121A/B-6 and exits the bottom into the 2nd stage of compression.
- This bottle is 1’ 8” in diameter and 3‘ 2” long.
D-121A/B-7 (C-120A/B 2nd Stage Discharge Bottles #1)
- Ethylene exits the 2nd stage compression and enters the top D-121A/B-7 and exits the side.
- This bottle is 1’ 8” in diameter and 5‘ 2” long.
D-121A/B-8 (C-120A/B 2nd Stage Discharge Bottles #2)
- Ethylene enters the top D-121A/B-8 and exits the side.
- This bottle is 1’ 8” in diameter and 13‘ 2” long.
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