Separation at sub-ambient temperature of a gaseous mixture containing carbon dioxide and a lighter contaminant
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Solution Overview
Problem
Existing methods for separating gas mixtures containing carbon dioxide at sub-ambient temperatures face challenges, particularly the risk of freezing and unpredictable valve operation due to the presence of two-phase mixtures, which complicates control and valve degradation.
Innovation Solution
A process involving multiple phase separation steps and controlled expansion of liquids to maintain temperatures above the triple point of carbon dioxide, avoiding heating to prevent vaporization and ensure a single-phase liquid for stable expansion, followed by further processing in distillation columns or heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the liquid is heated before expansion to prevent freezing, then the risk of freezing is reduced, but partial vaporization occurs generating two-phase mixture that disrupts valve control and degrades valve performance
Solution Approach 1:
The patent changes the temperature parameter of the liquid from heated to unheated (or minimally heated) before expansion. By maintaining the liquid temperature below the dew point but above the freezing point, the process avoids vaporization while preventing freezing, thus eliminating two-phase flow and ensuring stable valve operation.
Solution Approach 2:
The patent replaces the traditional heating approach with a simpler, more direct approach: controlling the liquid temperature to be unheated or minimally heated. This eliminates the need for complex heating control systems and avoids the harmful effects of two-phase flow, using a more reliable and simpler method.
2Reliability
If the liquid is expanded without heating to maintain single-phase flow, then valve control stability is improved, but the temperature drops excessively risking freezing
Solution Approach 1:
The patent optimizes the liquid temperature parameter before expansion by eliminating or minimizing heating. The liquid is maintained at a temperature that, when expanded, results in a final temperature above the freezing point, thus preventing freezing while maintaining single-phase flow and stable valve control.
3Object-affected harmful factors
If heating is applied to the liquid before expansion, then freezing is prevented, but energy losses increase due to partial vaporization and two-phase flow
Solution Approach 1:
The patent changes the temperature parameter from heated to unheated (or minimally heated), eliminating the energy input required for heating. By maintaining the liquid at a temperature that prevents freezing upon expansion without requiring prior heating, the process significantly reduces energy losses while still preventing freezing.
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 prevents excessive cooling and maintains a stable liquid phase, reducing energy losses and improving control over the separation process, thereby enhancing the efficiency and reliability of carbon dioxide enrichment.
Implementation Method 1
The expansion in a valve of the liquid at equilibrium resulting from the pot will generate a partial vaporization that will result in a large drop in the temperature at the outlet of the valve
Implementation Method 2
the gas that is treated in the sub-ambient temperature step must be cooled down to temperatures close to the triple point of carbon dioxide, in the region of −56° C. At these temperatures, the gas will be partially condensed, the liquid being particularly enriched in carbon dioxide
Data Source
AI summary
A device for separating a gas mixture containing at least 35 mol % carbon dioxide and also at least one gas lighter than carbon dioxide, comprising a first phase separator configured to receive a first partially condensed flow from an exchange line; a first phase separator configured to separate the gas phase from the liquid phase; a cooling means configured to receive the gas phase from the first phase separator and cool said gas phase to form a second partially condensed flow. The resulting liquid phase is then sent to a first valve and is expanded to a lower pressure that is at most 300 mbar lower in order to form a first expanded liquid, which is then mixed with a second liquid originating from the second phase separator in a mixing means that is located upstream of a third valve.