Ethylene plant refrigeration system
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Solution Overview
Problem
The existing refrigeration systems in ethylene plants require significant energy for compressing binary refrigerants, leading to high capital and operational costs due to inefficient energy usage.
Innovation Solution
A refrigeration system with multiple heat exchangers and compressor stages where the expanded refrigerant is successively fed back to previous heat exchangers to provide cooling, allowing for interstage cooling using cooling water, thereby reducing the energy required for compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If binary refrigerant is compressed by a single compressor in existing systems, then refrigeration is achieved, but energy consumption is high
Solution Approach 1:
The single compressor is divided into multiple compressor stages (first compressor stage, second compressor stage, third compressor stage). Each stage compresses the refrigerant to a different extent, with interstage coolers providing cooling between stages. This segmentation reduces the total energy required for compression compared to a single-stage compressor while maintaining the necessary refrigeration effect.
2Temperature
If refrigerant is expanded after each heat exchanger to lower temperature, then cooling effect is improved, but system complexity increases
Solution Approach 1:
The refrigerant is expanded in advance after each heat exchanger (first heat exchanger, second heat exchanger, third heat exchanger) to lower its temperature before it enters the next heat exchanger. This preliminary expansion action ensures that the refrigerant is at the optimal temperature for the subsequent cooling process, improving the overall cooling effect while managing system complexity through a structured approach.
3Loss of energy
If expanded refrigerant is fed back to previous heat exchangers, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The expanded refrigerant from each heat exchanger is fed back to previous heat exchangers in the series. Specifically, expanded refrigerant from the first heat exchanger is fed back to earlier stages, creating a feedback loop that recovers cooling capacity and reduces energy loss. This feedback mechanism improves energy efficiency by utilizing the cold refrigerant multiple times, though it does increase system configuration complexity.
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 total energy needed for the compressor stages, achieving efficient cooling while minimizing energy consumption and costs.
Implementation Method 1
a portion of the refrigerant is expanded to lower the temperature after each of the n heat exchangers
Implementation Method 2
n heat exchangers for progressively cooling the charge gas by the binary refrigerant
Implementation Method 3
n compressor stages for compressing the heated refrigerants
Data Source
AI summary
A refrigeration system for cooling a charge gas by a binary refrigerant. The refrigeration system comprises n heat exchangers, n compressor stages, at least one separator and a demethanizer. By flowing depressurized refrigerant through all the subsequent heat exchangers and installing interstage coolers, the overall energy for the refrigeration system is reduced.