Process for the separation of a gas rich in carbon dioxide
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Solution Overview
Problem
Current methods for separating gases rich in carbon dioxide are inefficient in cooling and processing, leading to suboptimal carbon dioxide yield and increased energy costs due to unstable pressure conditions and freezing issues, particularly when handling mixtures with other components like oxygen, nitrogen, and hydrocarbons.
Innovation Solution
A process involving a shell-tube exchanger operating at the triple point of carbon dioxide, where the feed gas is cooled and partially condensed, with a distillation column and phase separators to manage pressure and energy efficiently, allowing for expansion and vaporization of liquid streams to optimize carbon dioxide separation and storage, and utilizing a plate-fin heat exchanger for initial cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the feed gas is cooled in a conventional heat exchanger, then the cooling efficiency is limited, but the system complexity and energy consumption increase
Solution Approach 1:
The patent utilizes the triple point phase transition of carbon dioxide, where solid, liquid, and gas phases coexist. By operating the heat exchanger at the triple point conditions (−56.6°C and 5.11 atm), the system achieves maximum cooling efficiency through the latent heat of sublimation and fusion, while maintaining stable pressure conditions that simplify system design and control.
Solution Approach 2:
The carbon dioxide system serves itself by using its own phase change at the triple point as the cooling mechanism. The feed gas is cooled by contact with solid carbon dioxide at the triple point, and the resulting liquid carbon dioxide can be directly used for product storage, eliminating the need for external refrigerants or complex cooling systems.
2Productivity
If the compressor removes more gaseous carbon dioxide to increase yield, then the carbon dioxide production increases, but the pressure stability deteriorates
Solution Approach 1:
By operating at the triple point, the system utilizes the equilibrium between solid, liquid, and gas phases to automatically buffer pressure variations. When the compressor removes more gas, liquid carbon dioxide flashes to gas and solid forms, maintaining pressure stability. When less gas is removed, the presence of solid carbon dioxide prevents substantial pressure increase.
Solution Approach 2:
The triple point system provides inherent feedback control for pressure stability. The phase equilibrium automatically adjusts to compressor demand: if pressure tends to rise, solid carbon dioxide forms; if pressure tends to drop, liquid flashes to gas. This self-regulating mechanism allows flexible compressor operation to maximize yield without compromising pressure stability.
3Quantity of substance
If large blocks of frozen carbon dioxide are formed in the liquid, then the storage capacity increases, but the solid-liquid exchange surface decreases
Solution Approach 1:
The patent introduces mechanical agitation or vibration to the liquid carbon dioxide containing solid micro-crystals. This prevents the formation of large static blocks by continuously disrupting the solid-liquid interface, maintaining a high exchange surface area while still achieving substantial storage capacity through the suspended micro-crystal slush.
Solution Approach 2:
By maintaining the system at the triple point with continuous phase transitions between solid micro-crystals and liquid, the system creates a dynamic slush phase. This micro-crystal slush provides both storage capacity (through the solid phase) and high exchange surface area (through the dispersed nature of the crystals in liquid), resolving the contradiction between quantity and surface area.
4Adaptability or versatility
If three smaller compressors are used instead of one large compressor, then the adaptability to flow variations increases, but the device complexity and cost increase
Solution Approach 1:
The patent implements a dynamic compressor system where the number of operating compressors varies based on production demands and energy costs. The triple point buffer allows flexible modulation of compressor operation (1-3 compressors) without compromising system stability, enabling optimal economic operation across different flow rate requirements.
Solution Approach 2:
The triple point phase equilibrium acts as a buffer that decouples compressor flow variations from product delivery requirements. This allows the use of multiple smaller compressors with varying flow rates, as the triple point system absorbs and smooths out flow variations, maintaining stable liquid carbon dioxide production regardless of compressor configuration or operating mode.
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 stabilizes pressure, increases carbon dioxide yield, reduces energy costs by optimizing compressor usage, and enhances storage and liquefaction capacity without increasing apparatus size, while maintaining efficient separation of carbon dioxide from other components.
Implementation Method 1
The feed gas rich in carbon dioxide is cooled to a subambient temperature in a first heat exchanger
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
vaporizing at least part of the removed liquid stream in the shell and tube heat exchanger to form a vapor
Implementation Method 5
removing a liquid stream richer in carbon dioxide than the feed gas from the bottom of the distillation column, removing a gaseous stream less rich in carbon dioxide than the feed gas from the top of the distillation column
Implementation Method 6
partially condensed and separated to form a gaseous portion and a liquid
Data Source
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, partially condensed and separated to form a gaseous portion and a liquid, sending the liquid portion to the top of a distillation column, removing a liquid stream richer in carbon dioxide than the feed gas from the bottom of the distillation column, removing a gaseous stream 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 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 to the top of the distillation column, vaporizing a liquid stream 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 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.