Method and apparatus for separating a carbon dioxide-rich gas
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Solution Overview
Problem
Current methods for separating carbon dioxide-rich gases at sub-ambient temperatures face inefficiencies due to excessive gas production during expansion, leading to energy losses and mechanical stress in cryogenic applications, particularly when using multi-pass exchangers.
Innovation Solution
The method involves optimizing the cold box exchange line by incorporating a supercooler to supercool the carbon dioxide-rich liquid before expansion, allowing for indirect heat exchange in a tube-shell exchanger, which reduces gas production and optimizes energy consumption by utilizing low-temperature cold effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the liquid is expanded to reach low temperatures for cryogenic separation, then the temperature is reduced to sub-ambient levels, but excessive gas is produced which reduces cooling efficiency and increases mechanical stress
Solution Approach 1:
The liquid is supercooled before expansion in a dedicated supercooler unit, preparing it in advance to minimize gas formation during the subsequent expansion process. This preliminary cooling action ensures the liquid is at optimal temperature and pressure conditions before entering the expansion valve, thereby reducing exergy losses and improving cryogenic separation efficiency
2Temperature
If the liquid is expanded to reach low temperatures, then sub-ambient temperatures are achieved, but mechanical stress increases in the cryogenic system
Solution Approach 1:
The supercooler pre-cools the liquid to optimal conditions before expansion, ensuring that the phase change occurs more gradually and controllably. This reduces sudden pressure drops and thermal shocks that would otherwise create excessive mechanical stress on cryogenic system components such as heat exchangers and separation vessels
3Use of energy by moving object
If a multi-pass exchanger is used for heat exchange, then heat transfer efficiency is improved, but the system complexity and risk of freezing solid increases
Solution Approach 1:
The heat exchange function is divided into two separate units: a primary heat exchanger for main cooling duties and a dedicated supercooler for final temperature adjustment before expansion. This segmentation simplifies each individual unit, reducing the risk of complete system freezing while maintaining overall heat transfer efficiency through optimized temperature control at each stage
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 minimizes exergy losses and mechanical stress while enabling operation near the carbon dioxide triple point, enhancing the overall efficiency of the carbon dioxide separation process.
Implementation Method 1
the carbon dioxide-rich gas is cooled in a first, brazed aluminum plate-type heat exchanger made up of corrugated layers separated by plates
Implementation Method 2
the cooled gas condenses at least partially in the first exchanger
Implementation Method 3
the carbon dioxide-rich liquid which is cooled, next expanded then sent to a second heat exchanger
Implementation Method 4
it is necessary to expand it, and this may generate the production of gas. The gas thus obtained will not generate a great deal of cold because it will transfer only sensible heat. It is therefore advantageous to limit the production of gas by supercooling the liquid before expansion.
Data Source
AI summary
In a purification method, a carbon dioxide-rich gas is cooled in a first brazed aluminum plate-fin heat exchanger, the cooled gas or at least one fluid derived from the cooled gas is sent to a purification step comprising a distillation step, the purification step produces a carbon dioxide-rich liquid which is cooled, then 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.