CO2 Compressor Inlet Control for Stable Supercritical Pressurization
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Solution Overview
Problem
Existing pressure increasing systems face challenges in stabilizing the temperature and pressure of carbon dioxide at critical levels, leading to inefficient compression and increased energy requirements, especially when using carbon dioxide as a refrigerant for cooling.
Innovation Solution
A pressure increasing system with multiple stages of compressors, intermediate coolers, a subcooler, a bypass line with a flow rate adjusting valve, and a control unit to regulate temperature and pressure at the inlet of the final stage compressor, ensuring stable cooling and preventing physical property changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If carbon dioxide is cooled using carbon dioxide as a refrigerant in the subcooler, then the cooling efficiency is improved and the temperature is reduced, but the temperature may be excessively lowered causing the gas to enter the transition zone where physical properties easily change
Solution Approach 1:
The control unit continuously monitors the temperature and pressure of carbon dioxide at the inlet of the final stage compressor and dynamically adjusts the degree of opening of the flow rate adjusting valve based on these measurements. This feedback mechanism ensures that the temperature is maintained within an optimal range, preventing excessive cooling that would cause the gas to enter the unstable transition zone while still achieving efficient cooling.
Solution Approach 2:
The system dynamically adjusts the flow rate of refrigerant carbon dioxide through the flow rate adjusting valve based on real-time temperature and pressure conditions. This dynamic control allows the system to adapt to changing conditions and maintain stable physical properties of the carbon dioxide, avoiding the static cooling approach that could lead to excessive temperature reduction.
2Productivity
If the flow rate of refrigerant carbon dioxide is increased to enhance cooling, then the cooling capacity is improved, but the pressure and temperature stability at the compressor inlet deteriorates
Solution Approach 1:
The flow rate of refrigerant carbon dioxide is dynamically adjusted through the flow rate adjusting valve based on real-time measurements of temperature and pressure at the compressor inlet. This dynamic adjustment allows the system to optimize cooling capacity while maintaining stable physical properties of the carbon dioxide, preventing both excessive cooling and pressure/temperature fluctuations.
Solution Approach 2:
The control unit uses feedback from temperature and pressure sensors to continuously adjust the flow rate adjusting valve, ensuring that increased refrigerant flow rate for enhanced cooling does not compromise the stability of pressure and temperature at the compressor inlet.
3Use of energy by moving object
If carbon dioxide is cooled to a lower temperature to improve compression efficiency, then the power required for pressure increase is reduced, but the gas enters the transition zone where physical properties easily change making compression unstable
Solution Approach 1:
The system dynamically controls the refrigerant flow rate to achieve optimal cooling that reduces compression power requirements while maintaining the carbon dioxide temperature above the transition zone. This dynamic control ensures that cooling is sufficient to improve efficiency but not excessive to cause instability.
Solution Approach 2:
The control unit monitors temperature and pressure conditions and adjusts the flow rate adjusting valve to maintain optimal operating conditions, ensuring that the carbon dioxide remains in a stable physical state suitable for compression while minimizing the power required for pressure increase.
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
The system effectively cools carbon dioxide to a stable state suitable for compression, reducing the energy required for the final stage compression and preventing surging in compressors, while maintaining optimal physical properties.
Implementation Method 1
a flow rate adjusting valve which is provided on the bypass line and by which the extracted gas is depressurized upstream from the subcooler
Implementation Method 2
a subcooler that is provided between the final stage compressor and a compressor in a stage before the final stage and cools the gas
Implementation Method 3
the extracted gas is depressurized upstream from the subcooler
Data Source
Figure 1
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AI summary
A pressure increasing system (1) includes a plurality of stages of compressors (2) configured to compress carbon dioxide (F) to a target pressure higher than a critical pressure; intermediate coolers (4) that are provided between the plurality of stages of compressors (2) and cool the carbon dioxide (F) discharged from a compressor (2) in a preceding stage; a subcooler (5) that is provided between a seventh stage compressor (17) in the final stage and a sixth stage compressor (16) in a preceding stage and cools the carbon dioxide (F); a bypass line (6) which is connected to an inlet of the seventh stage compressor (17) and through which the carbon dioxide (F) in the inlet of the seventh stage compressor (17) is extracted, depressurized and supplied to the subcooler (5) as a refrigerant; a flow rate adjusting valve (7) provided on the bypass line (6); and a control unit (8) configured to regulate a degree of opening of the flow rate adjusting valve (7) so that at least one of a temperature and a pressure of the carbon dioxide (F) in the inlet of the seventh stage compressor (17) remains constant.