Open-Loop Ethylene Refrigeration for Low-Cost Cryogenic Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The high cost and energy intensity of closed-loop refrigeration systems used in cryogenic separation processes for recovering ethylene from methanol-to-olefins (MTO) effluents, as well as the limitations of non-cryogenic methods in achieving low enough temperatures for atmospheric storage, lead to significant capital and operating expenses.
Innovation Solution
An open-loop refrigeration system is employed, where the ethylene product is cooled via indirect heat exchange with a coolant at temperatures less than −100° C, and a portion of the cooled ethylene is mixed with methane to form a coolant, which is then expanded to further reduce the temperature, allowing for efficient sub-cooling of the ethylene-rich fraction for atmospheric storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If closed-loop refrigeration systems are used for cryogenic separation, then ethylene can be recovered at low temperatures, but capital and operating costs increase significantly
Solution Approach 1:
The patent extracts the refrigeration function from a separate closed-loop system and integrates it into the ethylene recovery process itself. The ethylene-rich fraction serves dual purposes: as the product being recovered and as the refrigerant medium, eliminating the need for specialized refrigeration equipment and reducing system complexity.
Solution Approach 2:
The ethylene-rich fraction performs multiple functions simultaneously: it is the desired product being separated and recovered, and it serves as the refrigerant medium for cooling. This multi-functionality eliminates the need for separate refrigeration systems and reduces both capital and operating costs.
2Device complexity
If non-cryogenic separation methods are used, then capital and operating costs decrease, but the ethylene-rich fraction cannot be stored at atmospheric conditions
Solution Approach 1:
The patent changes the temperature parameter of the ethylene-rich fraction from non-cryogenic to cryogenic ranges by using self-cooling during the separation process. This temperature change enables atmospheric storage without requiring high-pressure vessels or additional refrigeration equipment.
Solution Approach 2:
The patent performs preliminary cooling of the ethylene-rich fraction during the separation process itself, before storage. The cooling occurs as the fraction is formed and separated, preparing it for atmospheric storage without requiring additional cooling steps later.
3Temperature
If closed-loop refrigeration is used to subcool ethylene-rich fraction, then atmospheric storage is enabled, but additional refrigeration equipment and operating costs are required
Solution Approach 1:
The ethylene-rich fraction cools itself through the separation process without requiring external refrigeration equipment. The cooling is achieved through the inherent thermodynamics of the separation and phase change processes, eliminating the need for additional compressors and refrigeration systems.
Solution Approach 2:
The patent utilizes phase transitions during the separation process to achieve cooling. As the ethylene-rich fraction forms and undergoes phase changes during separation, it releases or absorbs heat, naturally achieving the required subcooling temperatures without external refrigeration.
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 approach reduces capital and operating costs by eliminating the need for additional refrigeration equipment, allows for lower refrigeration temperatures, and minimizes ethylene flashing during storage, enabling cost-effective and efficient sub-cooling of ethylene-rich fractions.
Implementation Method 1
cooling an ethylene product from at least one of an ethylene production process and an ethylene recovery process via indirect heat exchange with a coolant at a temperature less than about −100° C. to decrease the temperature of the ethylene product
Implementation Method 2
expanding at least one of the coolant, the methane, and the portion of the cooled ethylene to reduce a temperature of the coolant to less than −100° C. prior to the cooling
Data Source
AI summary
A process for chilling ethylene to required storage temperatures is disclosed, the process including: cooling an ethylene product from at least one of an ethylene production process and an ethylene recovery process via indirect heat exchange with a coolant at a temperature less than about −100° C. to decrease the temperature of the ethylene product; mixing a portion of the cooled ethylene product with methane to form the coolant; expanding at least one of the coolant, the methane, and the portion of the cooled ethylene to reduce a temperature of the coolant to less than −100° C. prior to the cooling; and feeding the heat exchanged coolant to at least one of the ethylene production process, the ethylene recovery process, and an open-loop refrigeration system.