Ethylene Open-Loop Refrigeration for Sub-Zero Storage Cooling
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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 that require high-pressure gas storage or insufficient sub-cooling for atmospheric storage, pose challenges in efficiently chilling ethylene to required storage temperatures.
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 temperature, allowing for efficient sub-cooling of the ethylene-rich fraction for atmospheric storage without the need for additional refrigeration equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If closed-loop refrigeration systems are used for cryogenic separation, then ethylene can be recovered at required temperatures, but capital cost and operating cost increase significantly
Solution Approach 1:
The patent extracts the refrigeration function from a complex closed-loop system and implements it through a simple open-loop expansion process using the ethylene product itself as the refrigerant. The ethylene is expanded through a valve or expander to achieve the required storage temperature without needing specialized refrigeration equipment.
Solution Approach 2:
The ethylene product serves dual functions: it is both the stored chemical product and the refrigerant medium. This eliminates the need for separate refrigeration systems and specialized metallurgy, reducing capital and operating costs while achieving the required storage temperature.
2Device complexity
If non-cryogenic separation methods are used, then capital cost decreases, but ethylene flashing occurs during atmospheric storage
Solution Approach 1:
The patent changes the temperature parameter by using expansion cooling to achieve sub-cooling of the ethylene below its storage temperature. This parameter change prevents flashing during atmospheric storage while avoiding the complexity of cryogenic separation systems.
3Temperature
If closed-loop refrigeration is used to subcool ethylene for atmospheric storage, then storage is feasible, but additional refrigeration compressors and high operating costs are required
Solution Approach 1:
The ethylene product itself provides the refrigeration service needed for its own storage. By expanding the ethylene through a valve or expander, the system achieves self-cooling without requiring external refrigeration compressors or additional energy input, eliminating the harmful energy consumption associated with closed-loop 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, eliminates flashing during storage, and allows for the use of existing equipment, achieving sub-cooling temperatures below −100° C for effective atmospheric storage of ethylene, thereby enhancing the efficiency and cost-effectiveness of ethylene storage.
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.