Extended Binary Refrigeration for Wide-Range Ethylene Plant Cooling
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Solution Overview
Problem
Ethylene plants require multiple separate refrigeration systems to achieve a wide range of temperature requirements, which increases complexity and capital costs, while existing binary and mixed refrigeration systems are limited in temperature range or have composition variations that complicate adjustments to operating conditions.
Innovation Solution
A single refrigeration system using an extended binary refrigerant mixture of methane and a C3 hydrocarbon, such as propylene or propane, which allows for a wider temperature range without composition variation, replacing separate propylene, ethylene, and methane refrigeration systems, particularly in olefins plants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If separate propylene, ethylene and methane refrigeration systems are used to cover the required temperature range, then the temperature range coverage is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple separate refrigeration systems (propylene, ethylene, and methane systems) into a single integrated refrigeration system. This is achieved by using a mixed refrigerant composition containing components from each separate system, allowing one system to perform the cooling function across the entire temperature range that previously required three separate systems.
Solution Approach 2:
The single refrigeration system is designed to perform multiple functions across different temperature ranges. The mixed refrigerant composition enables the system to provide refrigeration duties at various temperature levels (from methane temperature levels to propylene temperature levels) within a single system, making the system universal for all refrigeration needs in the ethylene plant.
2Device complexity
If a binary refrigeration system with fixed composition is used, then the system simplicity is improved, but the temperature range is limited
Solution Approach 1:
The patent uses a composite refrigerant mixture containing multiple hydrocarbon components (methane, ethylene, propylene, and optionally butane) in specific concentration ranges. This composite composition allows the single refrigeration system to achieve a wide temperature range (from below -140°C to near ambient temperature) while maintaining fixed composition for stable operation, overcoming the temperature limitations of simple binary systems.
3Temperature
If a tertiary refrigeration system with three components is used, then the temperature range is improved, but the refrigerant composition variation occurs
Solution Approach 1:
The patent specifies precise concentration ranges for each component in the mixed refrigerant (methane: 30-70 mol%, ethylene: 10-40 mol%, propylene: 10-40 mol%, and butane: 0-10 mol%) to optimize system performance. By controlling these compositional parameters within defined ranges, the system achieves both wide temperature coverage and stable, reproducible operation without the composition variation problems of tertiary systems.
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
The extended binary refrigerant system provides a simplified, cost-effective solution for ethylene plants by offering a single system capable of covering the necessary refrigeration temperature range from ambient to -136°C, reducing the need for multiple systems and facilitating adjustments to operating conditions.
Implementation Method 1
a refrigeration system utilizing a mixture of methane with a C3 hydrocarbon
Implementation Method 2
cooling a feed gas using an extended binary refrigerant
Implementation Method 3
the extended binary refrigerant being compressed in a multistage compressor
Implementation Method 4
being divided into a liquid coolant stream and a gaseous coolant stream after compression
Data Source
AI summary
A method of cooling using an extended binary refrigerant system containing methane and a C3 hydrocarbon such as propylene and/or propane is disclosed. The extended binary refrigerant from a compressor final discharge is separated into a methane-rich vapor fraction and at least one C3 rich liquid fraction so as to provide various temperatures and levels of refrigeration in various heat exchange stages. The method and corresponding refrigeration system can be utilized in plants utilizing low pressure or high pressure demethanizers.