Intermediate Fluid Heat Exchange for CO₂ Liquefaction Without Freezing
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Solution Overview
Problem
The existing methods for cooling and liquefaction of CO2-rich flows are energy-intensive and risk freezing carbon dioxide, especially when integrating with liquefied natural gas (LNG) systems, due to incompatibilities in enthalpy-temperature profiles and the need for high energy to adjust pressures and flow rates.
Innovation Solution
A process using an intermediate fluid rich in ethane or ethylene, designated as fluid C2, to recover cold from LNG, which is then used in a multi-fluid heat exchanger to cool and liquefy CO2, with a closed cycle that includes pumps and possibly a JT valve to manage pressures and flow rates, minimizing energy consumption and avoiding freezing risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If direct heat exchange between LNG and CO2 is used, then cooling efficiency is improved, but CO2 freezing risk increases
Solution Approach 1:
An intermediate fluid (nitrogen, HFO liquid, or CO2 itself at controlled conditions) is introduced to transfer heat between LNG and CO2. This mediator absorbs heat from CO2 and transfers it to LNG, achieving efficient cooling while maintaining temperatures above CO2 freezing point through controlled phase change of the intermediate fluid
2Productivity
If CO2 is compressed to supercritical pressure for liquefaction, then liquefaction efficiency is improved, but energy consumption increases
Solution Approach 1:
The process utilizes phase change parameters of an intermediate fluid at controlled pressures and temperatures. By changing the pressure and temperature parameters of the intermediate fluid during its phase change, heat is transferred efficiently to cool CO2 to liquefaction temperature without requiring supercritical compression, thereby reducing energy consumption
3Use of energy by moving object
If very low CO2 liquefaction pressure is used, then energy consumption is reduced, but CO2 yield decreases
Solution Approach 1:
The intermediate fluid undergoes controlled phase transitions (vaporization and condensation) at relatively low pressures. During vaporization, it absorbs heat from CO2, cooling it to liquefaction temperature. During condensation, it releases heat to LNG. This phase change mechanism enables efficient heat transfer and CO2 liquefaction at low pressures, maintaining both low energy consumption and high CO2 yield
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 allows for efficient cooling and liquefaction of CO2 with limited energy consumption, reducing the risk of carbon dioxide freezing and enabling integration with LNG systems, while maintaining compact exchanger compatibility and ambient temperature heating of LNG for network injection.
Implementation Method 1
heating a methane-rich fluid, for example vaporizing a methane-rich liquid
Implementation Method 2
The transfer of frigories is achieved by using an intermediate fluid rich in ethane or ethylene to transfer the frigories from the liquefied gas
Implementation Method 3
condensing at least a portion of the intermediate fluid vaporized in step ii) in a second heat exchanger at at least one pressure into at least one stream, by heat exchange with the methane-rich fluid
Implementation Method 4
cooling and optionally at least partially condensing the carbon dioxide-rich flow in a first heat exchanger at a pressure greater than 5 bar abs
Implementation Method 5
pressurizing the at least one stream of condensed intermediate fluid by means of a pump
Data Source
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AI summary
In a process for recovering cooling from a methane-rich fluid (1) for cooling a carbon dioxide-rich flow (5), cooling is supplied to a first heat exchanger (E1) for cooling the flow by vaporizing an intermediate fluid (11) by exchanging heat with the methane-rich fluid to form at least one stream of condensed intermediate fluid at at least one pressure level, at least a part (33) of the vaporized intermediate fluid is condensed in a second heat exchanger (E2) at at least one pressure into at least one stream.