CO2 Vaporization Pressure Control to Prevent Cryogenic Freezing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in cryogenic treatment of CO2 streams is to avoid sudden freezing of liquid CO2 near its triple point, which can lead to solid CO2 formation, clogging pipes and equipment, and causing overpressure issues due to its denser nature compared to liquid CO2.
Innovation Solution
The method involves vaporizing liquid CO2 at a pressure higher than the initial pressure, using a heat exchanger with a liquid level difference to increase vaporization pressure and ensure freezing occurs away from small hydraulic diameters, and employing expansion valves and compressors to manage pressure and prevent solid CO2 formation in sensitive areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid CO2 is vaporized at the lowest possible pressure to generate the coldest temperature for partial condensation, then CO2 recovery efficiency is improved, but the risk of solid CO2 formation and equipment clogging increases
Solution Approach 1:
The patent applies preliminary action by pre-heating the liquid CO2 before it enters the vaporization zone, and by designing the heat exchanger to ensure that vaporization occurs at pressures above the triple point. The liquid is heated in advance in the heat exchanger, and the vaporization is controlled to occur at pressures greater than the triple point pressure, preventing solid formation before it can clog equipment.
Solution Approach 2:
The patent changes the pressure parameter by maintaining vaporization pressure above the triple point (P > 5.1 bars), and changes the temperature parameter by controlling the heating process to ensure complete vaporization before the liquid reaches the triple point conditions. These parameter changes prevent the liquid from entering the solidification region.
2Productivity
If the pressure of the system drops, then CO2 can be recovered more efficiently, but freezing starts in zones with small hydraulic diameters causing equipment damage
Solution Approach 1:
The patent applies local quality by creating different pressure zones within the system. The heat exchanger operates at higher pressure (above triple point) to prevent freezing, while other zones can operate at lower pressures for efficient recovery. The liquid level difference H creates a hydrostatic pressure gradient that ensures the vaporization zone maintains sufficient pressure.
Solution Approach 2:
The patent provides beforehand cushioning by maintaining a liquid level difference H that creates a hydrostatic pressure head, cushioning against pressure drops that would otherwise cause freezing in the heat exchanger. This pressure buffer prevents the liquid from reaching freezing conditions even when system pressure fluctuates.
3Productivity
If liquid CO2 freezes in pipes and heat exchanger channels, then CO2 separation efficiency is improved, but equipment breaks due to overpressure from phase change
Solution Approach 1:
The patent changes the pressure parameter to maintain P > 5.1 bars during vaporization, keeping the system away from the triple point where solid formation occurs. By controlling temperature and pressure parameters, the liquid remains in the liquid-vapor transition region without entering the solidification region, preventing equipment damage from phase change overpressure.
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 the risk of equipment damage by controlling the vaporization pressure and preventing solid CO2 formation in critical areas, while maintaining efficient CO2 recovery and energy usage.
Implementation Method 1
a first liquid flow rich in carbon dioxide is sent to a heat exchanger where it vaporizes, all the liquid of the first flow vaporizing in the heat exchanger
Implementation Method 2
the first vaporized flow is released from the heat exchanger, expanded in a first expansion valve and sent back to the heat exchanger where it heats up
Implementation Method 3
the level of liquid in the enclosure is located at a higher level above the ground than the level at which the last drop of liquid rich in carbon dioxide vaporizes in the exchanger, the difference between the two levels being H
Implementation Method 4
the first vaporized flow is released from the heat exchanger, expanded in a first expansion valve
Data Source
Figure 1
Figure 2
AI summary
In a method for vaporising a carbon dioxide-rich liquid flow in which a first carbon dioxide-rich liquid flow (5) is drawn from an enclosure (S1) containing carbon dioxide-rich liquid and carbon dioxide-rich gas, the gas being at pressure P1, the first liquid flow is sent to a heat exchanger (7) where it vaporises, all the liquid from the first flow vaporises in the heat exchanger at a pressure or a plurality of pressures greater than P1, the first vaporised flow is discharged from the heat exchanger, expanded in a first expansion valve (V2) and sent back to the heat exchanger, where it heats up again.