Nitrogen-Brayton Power Cycle with Recycle Stream
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current power generation systems using natural gas or distillate fuels require multiple cycles and highly purified materials, limiting their efficiency and scalability, particularly in achieving high power outputs without significant capital costs or CO2 capture efficiency.
Innovation Solution
A power production system that utilizes a single working fluid, operates at lower maximum turbine temperatures, and employs near stoichiometric combustion in air to achieve high efficiency, with a compact design and CO2 capture capabilities, using a Brayton cycle with recycle streams to moderate temperatures and reduce NOx production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional NGCC systems are used for power generation, then high power output (450-550 MW) and efficiency (56-60%) are achieved, but the system requires multiple cycles (Brayton + Rankine), highly purified materials, and has high capital cost
Solution Approach 1:
The patent combines the Brayton cycle and Rankine cycle into a single integrated power generation system. The Brayton cycle uses nitrogen as working fluid for high-temperature power generation, while the Rankine cycle uses water/steam for lower-temperature power generation, both operating in parallel within the same system architecture. This merging allows the system to achieve 500+ MW power output with simplified structure compared to conventional separate-cycle systems.
Solution Approach 2:
The nitrogen-based Brayton cycle serves multiple functions: it generates power directly through the turbine, provides heat for the steam generator, and enables CO2 capture through the exhaust stream. The system can operate with various fuel types (natural gas, distillate fuels) and maintains flexibility in operating conditions, making it a universal power generation platform that replaces multiple specialized systems.
2Use of energy by moving object
If conventional NGCC systems are used, then efficiency of 56-60% is achieved, but the system has high capital cost and requires highly purified oxygen sources
Solution Approach 1:
The patent changes the working fluid from conventional air/oxygen-based systems to nitrogen-based Brayton cycle. This parameter change allows the system to achieve comparable thermal efficiency (56-60%) while using ambient air as the oxygen source, eliminating the need for expensive pure oxygen production facilities. The nitrogen inertness also enables simpler materials and construction, reducing capital costs.
Solution Approach 2:
The system uses ambient air as the oxygen source instead of requiring expensive purified oxygen. The nitrogen-based Brayton cycle可以利用 ambient air composition (21% O2, 79% N2), where the nitrogen acts as an inert diluent that simplifies the system. This approach replaces expensive oxygen purification infrastructure with free ambient air, significantly reducing capital costs while maintaining efficiency.
3Loss of substance
If CO2 capture is implemented in conventional NGCC systems, then CO2 can be removed, but the CO2 concentration in exhaust is low (approximately 3%) making capture difficult
Solution Approach 1:
The patent creates a localized high-CO2 concentration environment in the Brayton cycle exhaust stream by using nitrogen as the working fluid. The combustion of hydrocarbon fuels in nitrogen produces exhaust with significantly higher CO2 concentration (potentially 10-20% or more) compared to conventional air-based systems. This local quality enhancement at the exhaust point makes CO2 capture economically viable through conventional separation technologies.
4Productivity
If single train units with coal-fired boilers are used, then power output greater than 1,000 MW is achieved, but net electrical efficiency is limited to about 45%
Solution Approach 1:
The patent segments the power generation process into two independent but integrated cycles: nitrogen-based Brayton cycle for high-temperature power generation and water-based Rankine cycle for lower-temperature power generation. Each cycle operates independently with its own turbine and heat exchangers, allowing optimization of each segment for maximum efficiency. This segmentation enables the system to achieve efficiencies of 56-60% at power outputs of 500+ MW, and potentially 1,000+ MW when scaled, overcoming the efficiency ceiling of conventional single-cycle systems.
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 net electrical generation efficiencies comparable to or exceeding conventional NGCC systems while reducing capital costs and enabling CO2 capture with higher concentrations in the exhaust, allowing for efficient power production up to 500 MW and beyond.
Implementation Method 1
The present systems and methods utilize a nitrogen-based working fluid in a Brayton cycle with combustion of a hydrocarbon or distillate fuel
Implementation Method 2
The compressed air stream is heated in a heat exchanger against a turbine exhaust stream
Implementation Method 3
combustion of a fuel in air... a combustor configured to combust a fuel stream and an air stream
Data Source
AI summary
A method of power production using a high pressure/low pressure ratio Brayton Power cycle with predominantly N2 mixed with CO2 and H2O combustion products as the working fluid is provided. The high pressure can be in the range 80 bar to 500 bar. The pressure ratio can be in the range 1.5 to 10. The natural gas fuel can be burned in a first high pressure combustor with a near stoichiometric quantity of pressurized preheated air and the net combustion gas can be mixed with a heated high pressure recycle N2+CO2+H2O stream which moderates the mixed gas temperature to the value required for the maximum inlet temperature to a first power turbine producing shaft power.