CO2 Purification Heat Exchanger Near the Triple Point
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Solution Overview
Problem
Brazed aluminum plate exchangers used for purifying CO2-rich gas mixtures risk damage due to the formation of a solid CO2 phase when pressure drops to the triple point, leading to potential blockages and energy inefficiencies, as existing solutions either increase energy costs or degrade efficiency by avoiding solid formation.
Innovation Solution
A process utilizing a first brazed aluminum plate heat exchanger for cooling a CO2-rich mixture, followed by a second indirect heat exchange exchanger, where the liquid CO2 is expanded and heated using a gas derived from the cooled mixture, allowing operation near the triple point without solid CO2 formation, and incorporating a distillation and phase separation system to produce a gas rich in CO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the CO2-rich gas mixture is cooled close to the freezing temperature of CO2 to condense maximum CO2, then the purification efficiency is improved, but the risk of solid CO2 formation increases which may block and damage the exchanger
Solution Approach 1:
The patent introduces an intermediary heating step using a reboiler between the condensation exchanger and the phase separator. This intermediary device ensures that the liquid CO2 is heated to a temperature above the triple point before pressure reduction, preventing solid CO2 formation in the exchanger while maintaining high purification efficiency through effective condensation.
2Use of energy by moving object
If the pressure is reduced to the triple point value to enable vaporization and cooling, then the energy efficiency is improved, but solid CO2 phase appears which blocks the exchanger
Solution Approach 1:
The patent applies preliminary heating action through the reboiler before the pressure reduction step. By heating the liquid CO2 to a temperature above the triple point (−56.5°C) before expanding it to triple point pressure, the system prevents solid CO2 formation during vaporization, maintaining both energy efficiency and operational safety.
3Reliability
If the liquid supply position is raised above the exchanger to prevent solid formation, then the reliability is improved, but the energy efficiency degrades due to higher vaporization pressure
Solution Approach 1:
Rather than raising the liquid supply position which would degrade energy efficiency, the patent uses an intermediary reboiler that actively heats the liquid CO2 to prevent solid formation. This approach maintains the exchanger in its optimal position while achieving both reliability and energy efficiency through thermal management.
4Reliability
If the pressure is operated at higher pressure to avoid solid formation, then the reliability is improved, but the energy cost increases due to reduced condensation efficiency
Solution Approach 1:
The patent changes the temperature parameter of the liquid CO2 through reboiler heating, raising it above the triple point temperature before pressure reduction. This parameter change allows the system to operate at optimal condensation pressure while preventing solid formation, thereby reducing energy costs associated with operating at higher pressures.
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
Enables efficient CO2 purification near the triple point, reducing the risk of exchanger damage and maintaining energy efficiency by allowing operation at the triple point pressure while preventing solid CO2 formation, thus optimizing energy use and exchanger performance.
Implementation Method 1
the mixture rich in carbon dioxide is cooled in a first brazed aluminum plate heat exchanger
Implementation Method 2
the cooled mixture or at least one fluid derived from the cooled mixture is sent to a purification step comprising a distillation step and/or at least two successive steps of partial condensation
Implementation Method 3
the liquid rich in carbon dioxide is at least partially vaporized in the second exchanger
Implementation Method 4
the coldest temperature of the exchange is provided by the vaporization of CO2 close to the triple point
Implementation Method 5
the liquid rich in carbon dioxide is expanded then sent to a second heat exchanger where it is heated using a process fluid, the exchanger carrying out an indirect heat exchange only between the liquid rich in carbon dioxide and the process fluid
Implementation Method 6
a purification step comprising a distillation step and/or at least two successive steps of partial condensation
Data Source
AI summary
A carbon dioxide-rich mixture is cooled in a first brazed aluminum plate-fin heat exchanger, at least one fluid derived from the cooled mixture is sent to a purification step having a distillation step and/or at least two successive partial condensation steps, the purification step produces a carbon dioxide-depleted gas which heats up again in the first exchanger, the purification step produces a carbon-dioxide rich liquid which is expanded, then sent to a second heat exchanger where it is heated by means of a fluid of the method, the exchanger carrying out an indirect heat exchange only between the carbon dioxide-rich liquid and the fluid of the method, the carbon dioxide-rich liquid at least partially vaporizes in the second exchanger and the vaporized gas formed heats up again in the first exchanger to form a carbon dioxide-rich gas which can be the end product of the method.