Polyethylene Quench System Jet Pump Compressor Load
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Solution Overview
Problem
Conventional polyethylene manufacturing systems require the first compressor to operate at a high discharge pressure to supply make-up ethylene, leading to increased power consumption and wear, as it must match the suction pressure of the second compressor, especially when a cold quenching system is used, thereby raising the load on the first compressor.
Innovation Solution
A quench system employing a jet pump that receives low-pressure monomer from the first compressor, reducing the load on the first compressor by using energy from the product mixture discharged by the second compressor, allowing the first compressor to operate at a lower discharge pressure than the suction pressure of the second compressor, and utilizing a control system to modulate the monomer flow based on suction pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the first compressor discharge pressure is set to match the second compressor suction pressure to supply make-up ethylene, then the ethylene supply to the reactor is maintained, but the power consumption and wear of the first compressor increase
Solution Approach 1:
A jet pump is introduced as an intermediary device between the first and second compressors. The jet pump uses the high-velocity discharge from the second compressor to create a vacuum that draws in and pressurizes the make-up ethylene from the first compressor, eliminating the need for the first compressor to reach high discharge pressures directly.
Solution Approach 2:
The system uses the own discharge from the second compressor to power the jet pump, which then assists the first compressor. The high-velocity ethylene discharge from the second compressor serves dual purposes: maintaining reactor pressure and providing the driving force for the jet pump to handle make-up ethylene.
2Temperature
If a cold quenching system is implemented to cool the product mixture, then the phase separation is improved, but the load on the first compressor increases due to the need for higher discharge pressure
Solution Approach 1:
The jet pump acts as a mediator that decouples the pressure requirements of the quenching system from the first compressor. It allows the first compressor to operate at lower pressures while still delivering the cold ethylene needed for effective quenching and phase separation.
3Reliability
If the first compressor operates at high discharge pressure to supply both make-up ethylene and quench ethylene, then the system maintains stable operation, but the maintenance requirements increase due to increased wear
Solution Approach 1:
The jet pump serves as a protective intermediary that shields the first compressor from the high-pressure demands of the system. By handling the pressure differential through the jet pump's momentum-based mechanism, the first compressor operates under less stressful conditions, reducing wear and extending maintenance intervals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the energy consumption and maintenance requirements of the first compressor by eliminating the need for external energy to increase the discharge pressure, while maintaining effective cooling of the product mixture entering the separation system.
Implementation Method 1
A quench system includes a jet pump located downstream of, and in fluid communication with, the second compressor. The jet pump has a suction inlet that receives at least a portion of the monomer under relatively low pressure from the first compressor
Implementation Method 2
The injection of cold ethylene cools the product mixture as it enters the separation system, thereby promoting the phase separation of the product stream into a polymer-rich liquid phase, and a monomer rich off gas
Data Source
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AI summary
An ethylene polymerization system is provided with a quench system and that cools the product mixture entering the separation system with a reduced load on the first compressor of the system. The system includes first and second compressors, a high pressure reactor; a high pressure let down valve through which the product mixture from the high pressure reactor flows, and a separation system that separates gas from the product mixture. The quench system includes a pump having a suction inlet that receives all or substantially all of the low pressure flow of monomer from the first compressor. The system provides quenching of the product stream while allowing the first compressor to be operated at a discharge pressure lower than the suction pressure of the second compressor, thereby conserving energy.