CO2 Separation Column With Triple-Point Cooling for Pressure Stability
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Solution Overview
Problem
Current methods for separating gases rich in carbon dioxide lack efficiency in cooling and pressure stabilization, leading to suboptimal carbon dioxide yield and increased energy costs, especially when dealing with variations in energy prices and production levels.
Innovation Solution
The process involves cooling the feed gas to a subambient temperature in a first heat exchanger, followed by partial condensation and separation, with the liquid portion sent to a distillation column and the gaseous portion to a shell-and-tube heat exchanger where the tubes are surrounded by carbon dioxide at its triple point, allowing for stable pressure and efficient carbon dioxide recovery, and utilizing compressors and pumps to manage flow variations based on energy prices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the feed gas is cooled using conventional heat exchangers, then the cooling process can be carried out, but the pressure stability is poor and the cooling efficiency is insufficient
Solution Approach 1:
The patent utilizes the triple point phase transition of carbon dioxide, where solid, liquid, and gas phases coexist in equilibrium. By operating the heat exchanger at the triple point conditions (−56.6°C and 5.11 atm), the system maintains automatic pressure stability through the phase equilibrium of CO2, while achieving efficient cooling of the feed gas through direct thermal contact with the triple point CO2 bath
2Productivity
If more carbon dioxide is produced to increase yield, then the specific energy and specific cost decrease, but the apparatus dimensions would need to be increased
Solution Approach 1:
The patent employs the phase transition properties of CO2 at its triple point to create a compact cooling system. The solid-liquid-gas equilibrium allows for efficient heat transfer in a small volume, enabling high CO2 production rates without proportionally increasing apparatus dimensions. The triple point bath provides intense cooling capacity in a condensed space
3Stress or pressure
If the liquid carbon dioxide is flashed to form gas and solid for storage, then the pressure is stabilized at the triple point, but the system complexity increases
Solution Approach 1:
The patent utilizes the self-regulating nature of the triple point equilibrium, where the CO2 system automatically maintains pressure stability through its phase transition properties. When CO2 is removed as gas, the liquid flashes to replenish it, automatically stabilizing pressure without requiring complex external control systems. The triple point conditions provide inherent pressure regulation
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 enhances carbon dioxide yield and reduces specific energy and cost by maintaining stable pressure and increasing liquefaction capacity without apparatus enlargement, while optimizing compressor and pump usage during energy price fluctuations.
Implementation Method 1
sending the gaseous portion to a heat exchanger in which it condenses at least partially to form a liquid fraction
Implementation Method 2
the tubes of which are surrounded by a bath of carbon dioxide at its triple point
Implementation Method 3
the liquid stream from the bottom of the distillation column is expanded before vaporization
Implementation Method 4
the removed liquid stream is vaporized
Implementation Method 5
the feed gas rich in carbon dioxide is cooled to a subambient temperature in a first heat exchanger
Data Source
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AI summary
In a process for the separation of a gas rich in carbon dioxide and containing at least one component lighter than carbon dioxide, the feed gas rich in carbon dioxide is cooled in a first heat exchanger (E1), partially condensed and separated to form a gaseous portion and a liquid, sending the liquid portion to the top of a distillation column (K), removing a liquid stream richer in carbon dioxide than the feed gas from the bottom of the distillation column, removing a gaseous stream (17) less rich in carbon dioxide than the feed gas from the top of the distillation column and warming the gaseous stream in the first heat exchanger, sending the gaseous portion to a shell and tube heat exchanger (V3) having tubes in a bath of triple point carbon dioxide, in which it condenses at least partially to form a liquid fraction, sending the liquid fraction (35) to the top of the distillation column, vaporizing a liquid stream (19) from the bottom of the distillation column outside or within the distillation column to form a gas which is subsequently separated in the distillation column, expanding a liquid stream (21) from the bottom of the distillation column, vaporizing at least part of the expanded liquid stream in the shell and tube heat exchanger to form a vapor and warming the vapor formed in the first heat exchanger.