Closed CO2 Brayton CHP System for Solid-Fuel Combustion
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Solution Overview
Problem
Existing CHP systems face challenges in efficiently utilizing renewable organic waste streams for power generation, particularly in small-scale applications, due to inefficiencies in heat conversion, high capital costs, and the need to capture CO2 from exhaust gases, especially when handling solid organic materials.
Innovation Solution
A combined heat and power system utilizing an oxy-fuel combustion process with a closed CO2 Brayton cycle, where high-purity oxygen is used to oxidize solid organic fuels, generating CO2 as a working fluid for a gas turbine, which reduces the need for separate CO2 capture and enhances thermal efficiency by using CO2 as a denser and more efficient working gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional fossil fuel fired CHP systems are used, then electrical power can be produced, but the systems have high capital costs and produce CO2 emissions requiring capture
Solution Approach 1:
The patent uses oxygen-enriched combustion (oxy-fuel combustion) instead of air combustion to burn fossil fuels. This produces a flue gas stream with high CO2 concentration (70-95%) that can be directly utilized as a working fluid or product, eliminating the need for separate CO2 capture systems while maintaining power generation efficiency
Solution Approach 2:
The patent converts the harmful CO2 emission into a useful resource by using it as a working fluid in a heat exchanger and potentially as a product. The CO2 that would normally be captured and sequestered is instead utilized in industrial processes or returned to the atmosphere as a natural component, transforming an environmental liability into an economic asset
2Power
If gasification of solid organic materials is used for small CHP applications, then power generation is enabled, but the systems become costly and suffer from energy losses
Solution Approach 1:
The patent extracts and removes the gasification step from the traditional solid fuel power generation process. By directly combusting solid fuels in an oxygen-enriched environment, the system eliminates the complex and costly gasification equipment while maintaining the ability to generate power from solid organic materials
Solution Approach 2:
The patent applies oxy-fuel combustion to solid fuels, using oxygen-enriched gas instead of air to achieve complete and efficient combustion. This direct combustion approach simplifies the system architecture while improving energy conversion efficiency and reducing capital costs compared to gasification-based systems
3Device complexity
If ambient air is used in the Brayton cycle, then the system is simple, but the power output is limited due to lower gas density
Solution Approach 1:
The patent uses oxygen-enriched combustion to produce a high-density CO2-based working fluid that replaces ambient air in the Brayton cycle. This increases the mass flow rate and energy density of the working fluid, thereby increasing power output while maintaining relatively simple system architecture
Solution Approach 2:
The patent changes the composition and density parameters of the working fluid from ambient air to oxygen-enriched CO2 mixture. This parameter change increases the specific heat capacity and density of the working fluid, enabling higher power output from the same turbine size without significantly increasing system complexity
4Object-generated harmful factors
If CO2 capture systems are added to traditional CHP systems, then CO2 emissions are reduced, but capital costs increase significantly
Solution Approach 1:
The patent converts the CO2 emission stream from a waste product requiring costly capture and sequestration into a useful working fluid and potential product. By using oxy-fuel combustion, the CO2 is already concentrated and purified, eliminating the need for expensive capture equipment while creating economic value from what would otherwise be a liability
Solution Approach 2:
The patent makes the combustion system multi-functional by simultaneously generating power and producing concentrated CO2 as a usable product or working fluid. This eliminates the need for separate CO2 capture and utilization systems, reducing capital costs while achieving both power generation and CO2 management objectives
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 achieves higher thermal efficiency, reduces capital costs, and produces nearly pure CO2 for secondary uses, while eliminating the need for exhaust gas CO2 capture, offering 60% more power output and lower maintenance costs through controlled temperature management of heat exchangers.
Implementation Method 1
a closed CO2 Brayton cycle, where high-purity oxygen is used to oxidize solid organic fuels, generating CO2 as a working fluid for a gas turbine
Implementation Method 2
heating and pressurizing it through a heat exchanger
Implementation Method 3
an oxy-fuel combustion process with a closed CO2 Brayton cycle, where high-purity oxygen is used to oxidize solid organic fuels
Data Source
AI summary
A combined heat and power (CHP) system and a method of operating is provided. The CHP system includes an oxygen-air separation device. A combustion chamber has an inlet coupled to the oxygen-air separation device. The combustion chamber receives an expanded heated CO2 working gas for combustion of solid fuel and generates a CO2 exhaust gas. The expanded heated CO2 working gas comprising at least a portion of the CO2 exhaust gas. A heat exchanger receives combustion gases and outputs a cooled CO2 working gas. A turbine is provided having a compression section and an expansion section, the compression section configured to receive and compress the cooled CO2 working gas and to direct it to the heat exchanger. The turbine receives a heated CO2 working gas at the expansion section and expands the heated CO2 working gas. In an embodiment, CO2 products may be generated from the system.