Nested Supercritical CO2 Power Cycle for Self-Contained Oxycombustion
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Solution Overview
Problem
The Allam cycle, which uses supercritical CO2 as a working medium, faces challenges with high temperatures and pressures, requiring specialized equipment and posing scalability issues, and needs additional heat sources, limiting its use as a self-contained power plant for applications like container ships or oil platforms.
Innovation Solution
A nested cycle system utilizing CO2 as the working fluid, with a sub-critical first cycle operating at low pressure and a supercritical second cycle at higher pressure, employing oxycombustion of hydrocarbons in a Brayton cycle, where the first cycle provides heat to the second cycle through a gas/gas heat exchanger, eliminating the need for external heat sources and allowing for a self-contained power generation system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If supercritical CO2 is used as working fluid in the Allam cycle, then power density and efficiency are improved, but temperatures and pressures become excessively high requiring specialized equipment
Solution Approach 1:
The system divides the power generation process into two separate cycles: a first cycle operating at lower temperatures and pressures, and a second cycle operating at higher temperatures and pressures. This segmentation allows each cycle to operate within acceptable parameter ranges for standard equipment while collectively achieving high power density and efficiency.
Solution Approach 2:
The first cycle is nested within the second cycle, with the first cycle's exhaust heat being utilized by the second cycle. The first cycle's working fluid path is contained within the overall system structure of the second cycle, creating a nested configuration that optimizes heat transfer and system integration.
2Power
If supercritical CO2 is used as working fluid in the Allam cycle, then power density and efficiency are improved, but equipment size and complexity increase due to high pressure requirements
Solution Approach 1:
The system divides the power generation process into two separate cycles: a first cycle operating at lower temperatures and pressures, and a second cycle operating at higher temperatures and pressures. This segmentation allows each cycle to operate within acceptable parameter ranges for standard equipment while collectively achieving high power density and efficiency.
Solution Approach 2:
The system changes the operating parameters of CO2 through two distinct cycles, with the first cycle operating at lower pressure and temperature parameters and the second cycle operating at higher parameters. This parameter differentiation enables the use of standard equipment across both cycles while achieving superior performance.
3Object-generated harmful factors
If the Allam cycle is implemented, then CO2 emissions are reduced, but additional heat sources are required limiting self-contained operation
Solution Approach 1:
The first cycle serves the second cycle by providing heat to the second cycle's working fluid using the first cycle's exhaust heat. This self-service arrangement eliminates the need for external heat sources and enables complete self-contained operation of the power generation system.
Solution Approach 2:
The two cycles are merged into an integrated system where the first cycle's exhaust heat is combined with the second cycle's working fluid through a heat exchanger. This merging creates a unified system that generates power while managing CO2 emissions and providing self-contained operation.
4Loss of energy
If high temperatures and pressures are used in the Allam cycle, then efficiency is improved, but reliability decreases due to material and containment challenges
Solution Approach 1:
The system divides the power generation process into two separate cycles: a first cycle operating at lower temperatures and pressures, and a second cycle operating at higher temperatures and pressures. This segmentation allows each cycle to operate within acceptable parameter ranges for standard equipment while collectively achieving high power density and efficiency.
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 nested cycle system achieves high power density and efficiency without extreme temperatures and pressures, enabling a self-contained, emission-free power generation system suitable for marine vessels and isolated facilities, with net efficiencies over 40% and reduced equipment size and weight compared to conventional systems.
Implementation Method 1
heating of working fluid in the second cycle by the products of combustion and circulating working fluid in the first cycle through a gas/gas heat exchanger
Implementation Method 2
expanded in turbine 2 to generate electrical power via a generator driven by the turbine
Implementation Method 3
The remaining working fluid is compressed at 5 in two stages
Implementation Method 4
passes through a recuperator (heat exchanger) 3 which transfers heat to CO2 heading back to the combustion chamber
Implementation Method 5
oxycombustion of hydrocarbons, preferably LNG, in a combustion chamber
Data Source
AI summary
Electrical/mechanical power is derived from oxycombustion of hydrocarbons, preferably LNG, in a first of two nested cycles each operating on a Brayton cycle to provide a source of power, without mixing of working fluids between the two cycles. Each cycle employs CO2 as a working fluid, the first cycle operating under low pressure conditions in which CO2 is sub-critical, and the other cycle operating under higher pressure conditions in which CO2 is supercritical. The first cycle serves as a source of heat for the second cycle by gas/gas heat exchange which cools the products of combustion and circulating working fluid in the first cycle and heats working fluid in the second cycle.