Cryogenic Gas Cooling System and Method
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Solution Overview
Problem
The high energy consumption and inefficiency in liquefying cryogenic gases, such as hydrogen and helium, due to the difficulty in compressing these gases and the subsequent high energy usage in refrigeration cycles, particularly in systems that rely on multiple stages of gas compression and nitrogen boiling off to atmosphere.
Innovation Solution
A system and method that incorporate a pre-cool heat exchanger and liquefier heat exchanger with pre-cool and primary refrigeration circuits, utilizing pre-cool and primary refrigerants to pre-cool and liquefy cryogenic gases, reducing the energy required by the primary refrigerant compressor through a pre-cooling loop that separates and expands refrigerants to lower boiling points, thereby optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple stages of gas compression are used to liquefy cryogenic gases, then the liquefaction capability is improved, but the energy consumption increases significantly
Solution Approach 1:
The system performs preliminary cooling of the cryogenic gas feed stream using a pre-cool refrigeration circuit before the gas enters the primary refrigeration circuit. This pre-cooling action reduces the temperature differential that the primary circuit must handle, thereby reducing the compression work and energy consumption required for liquefaction.
Solution Approach 2:
The refrigeration system is divided into two separate circuits: a pre-cool refrigeration circuit operating at higher temperatures and a primary refrigeration circuit operating at lower temperatures. This segmentation allows each circuit to operate more efficiently in its optimal temperature range, reducing overall energy consumption compared to a single-stage system.
2Reliability
If compressors are used in hydrogen refrigeration cycles, then the refrigeration effect is achieved, but the energy consumption increases due to difficulty in compressing hydrogen
Solution Approach 1:
The pre-cool refrigeration circuit performs preliminary cooling of the hydrogen feed stream before it enters the primary refrigeration circuit. This reduces the temperature and pressure requirements for the primary compressors, thereby reducing the energy consumption associated with compressing hydrogen in the primary circuit.
Solution Approach 2:
The pre-cool refrigerant acts as an intermediary that absorbs heat from the hydrogen feed stream before the primary refrigerant does. This intermediary cooling reduces the workload on the primary compressors and reduces overall energy consumption.
3Reliability
If nitrogen is boiled off to atmosphere after providing refrigeration, then the refrigeration cycle is completed, but nitrogen is consumed and energy is wasted
Solution Approach 1:
Instead of discarding the warmed pre-cool refrigerant to atmosphere, the system recovers it by directing it back through the heat exchanger where it absorbs heat from the incoming cold stream. This recovery process maintains the refrigeration cycle while eliminating nitrogen consumption and associated energy waste.
Solution Approach 2:
The warmed pre-cool refrigerant serves itself by automatically absorbing heat from the cold hydrogen stream as it passes through the heat exchanger, thereby re-cooling itself without requiring additional energy input or disposal infrastructure.
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 described system reduces the energy required for liquefying cryogenic gases by shifting cooling power from the primary refrigeration circuit to the pre-cool refrigeration circuit, minimizing energy usage and power requirements, and enhancing the overall efficiency of the liquefaction process.
Implementation Method 1
a pre-cool heat exchanger (46) including a pre-cool refrigerant warming passage (48, 52), a primary refrigerant cooling passage (58, 62), a primary refrigerant warming passage (76, 102) and a feed gas cooling passage (13a, 13b)
Implementation Method 2
A liquefier heat exchanger (26a-26f) includes a primary refrigerant cooling passage, a primary refrigerant warming passage and a feed gas cooling passage
Implementation Method 3
a pre-cool expansion device configured to receive and expand compressed and cooled pre-cool refrigerant from the pre-cool cooling device
Implementation Method 4
a pre-cool separation device configured to receive expanded pre-cool refrigerant from the pre-cool expansion device at a reduced pressure so as to lower a boiling point of the expanded pre-cool refrigerant and to separate the expanded pre-cool refrigerant into a pre-cool refrigerant vapor stream and a pre-cool refrigerant liquid stream
Implementation Method 5
The pre-cool heat exchanger is configured so that primary refrigerant in the primary refrigerant cooling passage of the pre-cool heat exchanger and cryogenic gas in the feed gas cooling passage are cooled by pre-cool refrigerant in the pre-cool refrigerant warming passage
Data Source
AI summary
A pre-cool refrigeration circuit includes a pre-cool compressor configured to receive and compress pre-cool refrigerant vapor from a pre-cool heat exchanger, a pre-cool cooling device configured to receive and cool compressed pre-cool refrigerant from the pre-cool compressor, a pre-cool expansion device configured to receive and expand compressed and cooled pre-cool refrigerant from the pre-cool cooling device, and a pre-cool separation device configured to receive expanded pre-cool refrigerant from the pre-cool expansion device at a reduced pressure so as to lower a boiling point of the expanded pre-cool refrigerant and to separate the expanded pre-cool refrigerant into a pre-cool refrigerant vapor stream and a pre-cool refrigerant liquid stream. A primary refrigeration circuit includes a first primary compressor configured to receive and compress a primary refrigerant vapor from a liquefier heat exchanger and the pre-cool heat exchanger, a primary cooling device configured to receive and cool compressed primary refrigerant from the first primary compressor. The primary cooling device is in fluid communication with the pre-cool heat exchanger and the liquefier heat exchanger. A first primary expansion device is configured to receive and expand compressed and cooled primary refrigerant from the liquefier heat exchanger, with the first primary expansion device having an outlet in fluid communication with the liquefier heat exchanger and the pre-cool heat exchanger.