CO₂ Liquefaction Pressure Control for Variable Impurity Composition
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Solution Overview
Problem
Existing CO2 liquefaction systems face challenges in managing variations in CO2 source composition, which can lead to freezing issues and energy inefficiencies due to fluctuations in suction pressures, particularly when transporting CO2-rich gases containing impurities like nitrogen and oxygen.
Innovation Solution
The system employs a method where CO2-rich gas is compressed and cooled, with a portion expanded to maintain a cooling balance and prevent freezing, while ensuring constant suction pressure for the cycle compressor, utilizing a turbine-compressor arrangement to recover energy and adapt to varying impurity concentrations, and incorporating additional treatments like gas drying and purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CO2-rich gas is cooled to prevent freezing, then the reliability of the system is improved, but the energy consumption increases due to additional cooling requirements
Solution Approach 1:
The patent converts the harmful effect of light impurities (which cause freezing) into a beneficial control mechanism. By measuring the impurity content and using it to dynamically adjust the expansion pressure, the system transforms a reliability threat into an opportunity for optimized energy consumption while maintaining safe operating temperatures above the freezing point.
2Productivity
If the suction pressure of the cycle compressor is maintained constant, then the productivity is improved, but the device complexity increases due to additional pressure regulation mechanisms
Solution Approach 1:
The patent implements a feedback control system where the impurity content measurement feeds into the expansion pressure regulation, which in turn maintains constant suction pressure at the compressor inlet. This closed-loop control ensures stable productivity while the complexity is managed through automated control rather than mechanical complexity.
Solution Approach 2:
The system dynamically changes the expansion pressure parameter based on impurity content measurements. By adjusting this key parameter, the system maintains constant suction pressure and optimal productivity without requiring complex mechanical modifications to the compressor itself.
3Temperature
If the expansion pressure is increased to prevent freezing of CO2, then the temperature margin is improved, but the energy loss increases due to additional expansion work
Solution Approach 1:
The patent transforms the static expansion pressure into a dynamic parameter that adjusts in real-time based on impurity content. This allows the system to use the minimum necessary expansion pressure to maintain the temperature margin above freezing, minimizing energy loss while ensuring safety. The dynamic adjustment replaces fixed high-pressure expansion with optimized variable-pressure expansion.
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 ensures reliable operation by preventing freezing, optimizing energy consumption, and maintaining system safety even with varying CO2 source compositions, allowing for efficient liquefaction and transport of CO2 while minimizing losses.
Implementation Method 1
the CO2-rich gas from one or more sources is compressed via the cycle compressor
Implementation Method 2
at a supply pressure is cooled to form a liquid or supercritical flow
Implementation Method 3
one of the fractions being expanded in a valve to a first pressure to form a biphasic mixture
Implementation Method 4
the vaporized gas then being expanded from the first pressure to a second pressure in an expansion means
Data Source
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Figure 2
AI summary
The invention relates to a method for liquefying a gas containing at least 60 mol % of CO2, in order to produce at least one liquid product, wherein the gas is cooled in order to form a fluid flow, at least a portion of the liquid or supercritical flow is cooled in a heat exchanger (E1) in order to form a cycle fluid having a cycle pressure, the cycle fluid is divided into at least two fractions including an auxiliary fraction, one of the fractions being expanded up to a first pressure in a valve (43) in order to form a biphasic mixture, and then sent to a phase separator (35). The liquid fraction of the phase separator is vaporized so as to form a vaporized gas in the exchanger, the vaporized gas then being expanded from the first pressure to a second pressure in an expansion means (45), and then compressed in the cycle compressor (C1, C2) and mixed with the first feed gas. The auxiliary fraction comprises the liquid product, and the first pressure is increased if the amount of impurities that are lighter than the carbon dioxide contained in the carbon-dioxide-rich gas increases.