Separating carbon dioxide and ethane from a mixed stream
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Solution Overview
Problem
Current methods for separating carbon dioxide (CO2) from ethane are inefficient, as they either contaminate ethane, require large amounts of energy, or fail to achieve complete separation due to the formation of azeotropic mixtures, which hinder fractionation processes.
Innovation Solution
A method involving the generation of a liquid stream of CO2 and ethane, which is then flashed through a valve into an accumulation vessel, allowing solid CO2 to form while enriching the vapor stream in ethane, enabling subsequent distillation for partial ethane recovery and subsequent recycling to achieve complete separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If normal fractionation techniques are used to separate CO2 from ethane, then separation is attempted, but complete separation cannot be achieved due to azeotropic mixture formation
Solution Approach 1:
The patent changes the physical state parameter of CO2 from gas/liquid to solid by operating at temperatures below the eutectic point of the CO2-ethane system. This phase change allows complete separation since solid CO2 can be mechanically removed from liquid ethane, bypassing the azeotropic limitation that prevents complete separation in vapor-liquid equilibrium systems.
2Manufacturing precision
If extractive distillation with heavy component is used, then ethane absorption is improved, but process complexity and energy consumption increase
Solution Approach 1:
The patent utilizes the phase transition of CO2 to solid form at temperatures below the eutectic point. This physical transformation provides a natural separation mechanism where solid CO2 settles and can be mechanically removed from liquid ethane, eliminating the need for complex extractive distillation equipment and heavy component additives.
3Manufacturing precision
If two-pressure fractionation is used to exploit azeotropic composition differences, then separation is attempted, but very large recycle streams and energy consumption are required
Solution Approach 1:
The patent employs a single-phase transition approach where CO2 is converted to solid form at temperatures below the eutectic point. This eliminates the need for two-pressure fractionation systems and large recycle streams, significantly reducing energy consumption while achieving complete separation.
4Productivity
If cryogenic processes are used to separate CO2 from methane, then CO2 disposal efficiency is improved, but valuable hydrocarbons are condensed and separated with CO2, reducing recovery potential
Solution Approach 1:
The patent applies local quality by operating at specific temperatures below the eutectic point where CO2 transitions to solid form while ethane remains liquid. This creates a localized condition where CO2 can be selectively removed as solid particles, allowing hydrocarbon recovery while maintaining efficient CO2 separation.
Solution Approach 2:
The patent uses the phase transition of CO2 to solid form to differentiate its behavior from ethane, which remains liquid at the operating temperature. This phase difference enables selective CO2 removal while preserving ethane in liquid form for recovery, solving the contradiction between CO2 disposal efficiency and hydrocarbon recovery.
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 allows for the substantial separation of CO2 and ethane with minimal residual contamination and energy integration, reducing the need for external refrigeration and enabling the recovery of pure ethane and CO2 streams for efficient disposal and sale.
Implementation Method 1
passing the liquid stream through a flash valve into an accumulation vessel, forming a gas that is enhanced in ethane, and forming solid CO2
Implementation Method 2
passing the liquid stream through a flash valve into an accumulation vessel
Implementation Method 3
accumulating the solid CO2 in the accumulation vessel, and removing the gas from the top of the accumulation vessel
Data Source
AI summary
Embodiments described herein provide methods and systems for separating a mixed ethane and CO2. A method described includes generating a liquid stream including ethane and CO2. The liquid stream is flashed to form an ethane vapor stream and solid CO2. The solid CO2 is accumulated in an accumulation vessel and the gas is removed from the top of the accumulation vessel.