Cryogenic CO2 Compressor Inlet Pressure Control for Variable Feed Gas
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Solution Overview
Problem
Existing CO2 capture and purification methods using cryogenic separation are inefficient due to variations in gas composition and flow rate, leading to oversizing of equipment and suboptimal operation, particularly affecting the compressor and heat exchangers.
Innovation Solution
A compressor design that adjusts outlet pressure based on CO2 composition and flow rate to maintain constant volumetric flow rate, using a fan to control pressure variations and prevent oversizing of the main compressor, with optional parallel fans for additional control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the compressor is sized for low CO2 composition scenarios, then it can handle increased low-pressure flow rates, but it operates suboptimally during nominal operation with excessive capacity
Solution Approach 1:
The patent applies dynamics by making the compressor inlet pressure variable rather than fixed. A fan is introduced upstream of the compressor to dynamically adjust the inlet pressure according to the CO2 composition of the gas stream. When CO2 composition decreases, the fan increases inlet pressure to maintain constant volumetric flow rate into the compressor, allowing the compressor to operate at optimal capacity across varying composition scenarios rather than being oversized for low-composition cases.
2Temperature
If the gas is cooled more to condense CO2 at lower partial pressures, then CO2-enriched liquid phase formation is achieved, but the distribution of liquid CO2 streams must be adjusted increasing expanded liquid CO2 flow rates
Solution Approach 1:
The patent applies parameter changes by modifying the inlet pressure parameter to the compressor based on CO2 composition variations. When CO2 composition decreases, the system changes the pressure parameter (increases it via the fan) to maintain constant volumetric flow rate. This prevents the need to increase expanded liquid CO2 flow rates, as the compressor operates at stable capacity regardless of composition changes, thereby stabilizing the liquid CO2 distribution between expanded and non-expanded streams.
3Adaptability or versatility
If heat exchangers are sized for low-composition scenarios, then they can handle increased vaporization demands, but they are oversized for nominal composition operation
Solution Approach 1:
The patent applies dynamics by stabilizing the volumetric flow rate into the compressor through dynamic pressure adjustment by the fan. This ensures that the demand for vaporization in the heat exchangers remains constant regardless of CO2 composition variations. Consequently, heat exchangers can be sized for nominal operation without being oversized, as the stabilized flow rate prevents excessive vaporization demands during low-composition scenarios.
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 the operation of the CO2 capture unit, reducing costs and maintaining efficiency by ensuring consistent performance across varying gas compositions and flow rates, avoiding the need for frequent equipment resizing.
Implementation Method 1
the gas that is to be separated is compressed in a compressor to produce a compressed gas
Implementation Method 2
the inlet pressure of the gas that is to be separated, entering the compressor, is modified according to the CO2 content and/or the flow rate of the gas that is to be separated so as to reduce the variations in volumetric flow rate
Implementation Method 3
a unit that captures and purifies CO2 by cryogenic means... based on the partial condensation of the CO2 at temperatures close to its triple point
Implementation Method 4
which may be supplemented by one or more distillations to increase the CO2 purity of the end product
Implementation Method 5
to cool them in order to form a CO2-enriched liquid phase and a gaseous phase enriched in incondensable gases that will be separated
Data Source
AI summary
In a method for compressing a gas that is to be separated in a low-temperature CO2 separation unit using at least one partial condensation step and/or at least one distillation step, the gas that is to be separated has a variable composition and/or variable flow rate, the gas that is to be separated is compressed in a compressor to produce a compressed gas and the inlet pressure of the gas that is to be separated, entering the compressor, is modified according to the CO2 content and/or the flow rate of the gas that is to be separated so as to reduce the variations in volumetric flow rate of the gas that is to be separated entering the compressor.