Bottoming Cycle Power System Exhaust Gas Heat Exchanger
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Solution Overview
Problem
Current bottoming cycle power systems face inefficiencies in converting waste heat into usable power and capturing carbon dioxide due to high energy consumption, pressure drops, and interference from water vapor, leading to reduced net-work and increased carbon dioxide emissions.
Innovation Solution
The implementation of a bottoming cycle power system with an exhaust gas heat exchanger and processing system that reduces the specific volume and mass of exhaust gas, utilizing a carbon dioxide capture system with heat of compression to regenerate carbon dioxide, while maintaining exhaust gas temperature for efficient flow and energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If exhaust gas is cooled to reduce specific volume and mass before compression, then the work required by the turbo-compressor is reduced, but the exhaust gas temperature becomes too low for efficient flow and energy recovery
Solution Approach 1:
The cooling process is divided into two distinct stages: first, an exhaust gas heat exchanger performs initial cooling to reduce temperature and specific volume; second, a cooling tower performs further cooling to achieve the target temperature reduction of 100-500°F. This segmentation allows progressive cooling while maintaining adequate temperature for efficient flow.
Solution Approach 2:
The exhaust gas is cooled preliminarily through the heat exchanger before entering the turbo-compressor, reducing its specific volume and mass in advance. This preliminary cooling action decreases the compression work requirement while ensuring the temperature remains sufficient for efficient flow through the system.
2Use of energy by moving object
If water vapor is removed from exhaust gas, then the mass and specific volume are reduced improving compression efficiency, but additional energy is consumed for water removal
Solution Approach 1:
Water vapor is removed from the exhaust gas through condensation, a phase transition from gas to liquid. The cooling processes cause water vapor to condense into liquid water, which is then separated and removed. This phase transition efficiently reduces the mass and specific volume of the exhaust gas, improving compression efficiency while the energy cost is offset by the overall energy recovery from waste heat utilization.
3Power
If exhaust gas pressure is increased to improve power generation, then the work output increases, but the energy consumption for compression increases
Solution Approach 1:
The temperature parameter of the exhaust gas is changed through controlled cooling, reducing it from high temperature to a lower temperature range (100-500°F reduction). This parameter change decreases the specific volume and mass of the exhaust gas, allowing the turbo-compressor to achieve the required pressure increase with reduced energy consumption, thereby maintaining power generation efficiency.
4Power
If the turbo-compressor pulls more vacuum to increase compression ratio, then the power output increases, but the pressure drop across the system increases reducing overall efficiency
Solution Approach 1:
The exhaust gas is preliminarily cooled and its specific volume is reduced before it enters the turbo-compressor. This preliminary action allows the compressor to achieve a higher compression ratio and pull more vacuum without creating excessive pressure drop across the system, because the reduced specific volume means less work is required to achieve the same pressure differential.
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 enhances the efficiency of power generation by reducing the work required by the turbo-compressor, increases net energy production, and minimizes energy consumption for carbon dioxide capture, thereby improving overall system efficiency and reducing emissions.
Implementation Method 1
The exhaust gas heat exchanger has a first flow path that receives a flow of hot exhaust gas from the turbo-expander prior to the exhaust gas being compressed by the turbo-compressor and a second flow path that receives a flow of cooled exhaust gas from the turbo-compressor
Implementation Method 2
The cooling tower is operable to cool the flow of exhaust gas from the exhaust gas heat exchanger
Implementation Method 3
The absorption chiller heat exchanger may be operable to receive the flow of exhaust gas from the exhaust gas heat exchanger and to cool the exhaust gas with a flow of absorption chiller coolant fluid
Implementation Method 4
The dehumidifier system may be operable to remove water from the flow of exhaust gas
Implementation Method 5
Each capture tank includes carbon dioxide absorbent material operable to absorb carbon dioxide from the exhaust gas
Implementation Method 6
A heat of compression from the carbon dioxide compressor is transferable to the capture tank to regenerate the carbon dioxide from the carbon dioxide absorbent material
Data Source
AI summary
A method of generating electrical power includes expanding a flow of exhaust gas from a combustion process as the exhaust gas passes through a turbo-expander disposed on a turbo-crankshaft. The flow of exhaust gas from the turbo-expander is routed through a first flow path of an exhaust gas heat exchanger. The flow of exhaust gas from the first flow path is compressed as the exhaust gas passes through a turbo-compressor disposed on the turbo-crankshaft. The flow of exhaust gas from the turbo-compressor is routed through a second flow path of the exhaust gas heat exchanger. Heat from the first flow path is transferred to the second flow path to cool the exhaust gas in the first flow path and heat the exhaust gas in the second flow path. Electrical power is generated from a generator disposed on the turbo-crankshaft.