Circulating Fluidized Bed Combustor Thermal Storage
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Solution Overview
Problem
Current power generation systems, especially those with CO2 capture and storage (CCS), face challenges in flexibility and economic viability due to high capital costs and inefficiencies in energy storage, particularly when dealing with intermittent renewable energy sources and fossil fuel power plants.
Innovation Solution
A system and method utilizing circulating fluidized bed combustors fired with air or oxygen, integrated with a CaO/CaCO3 chemical loop for CO2 capture, allowing for efficient thermal energy storage by leveraging the high thermal energy content of solids at high temperatures, enabling flexible power output and reducing capital costs through innovative silo and heat exchanger configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thermal energy storage systems are implemented in fossil fuel power plants to enable flexibility, then power output adaptability improves, but system complexity and capital costs increase
Solution Approach 1:
The patent combines the thermal energy storage function with the existing circulating fluidized bed combustor system by integrating hot and cold silos directly into the combustion circuit. The storage silos are positioned to receive hot solids directly from the combustor and return them after cooling, merging storage functionality with the existing combustion and heat exchange processes rather than adding separate standalone storage systems.
Solution Approach 2:
The circulating solids serve multiple functions simultaneously: they act as heat carriers for power generation, as storage medium for thermal energy, and as the working fluid for the fluidized bed process. The same solids circulate through the combustor, heat exchangers, and storage silos, performing combustion, heat transfer, and energy storage functions in sequence without requiring separate media for each function.
2Adaptability or versatility
If fossil fuel power plants operate at low capacity factors to accommodate renewable energy, then renewable energy integration improves, but operational efficiency and economic viability worsen
Solution Approach 1:
The system performs preliminary thermal energy storage during periods of low electricity demand or high renewable generation by storing hot solids in the hot silo. When electricity demand increases or renewable generation decreases, the stored thermal energy is rapidly released by returning hot solids to the combustor, enabling quick response to market conditions without sacrificing base-load operational efficiency.
Solution Approach 2:
The system operates in periodic cycles of charging (storing thermal energy in silos during low-demand periods) and discharging (releasing stored energy during peak-demand periods). The circulating solids are periodically diverted to storage silos and back, creating a rhythmic charge-discharge pattern that matches electricity demand fluctuations while maintaining continuous combustor operation.
3Object-generated harmful factors
If CO2 capture systems with CaO/CaCO3 chemical looping are integrated, then CO2 capture capability improves, but system complexity and capital intensity increase
Solution Approach 1:
The patent merges the CO2 capture chemical looping process with the thermal energy storage system by using the same circulating solids that move between hot and cold silos. The CaO/CaCO3 conversion occurs within the existing combustor and heat exchanger circuit, eliminating the need for separate dedicated CO2 capture equipment and integrating carbonation and calcination reactions into the thermal storage cycle.
Solution Approach 2:
The circulating solids perform triple functions: heat carrier for thermal energy storage, reaction medium for CO2 capture via CaO/CaCO3 conversion, and fluid for maintaining fluidized bed combustion. The same solid particles simultaneously enable thermal storage, carbon dioxide capture, and combustion processes without requiring separate material streams for each function.
4Adaptability or versatility
If thermal energy storage using circulating solids is implemented, then operational flexibility improves, but equipment investment costs increase
Solution Approach 1:
The circulating solids themselves serve as the thermal energy storage medium, eliminating the need for separate storage containers or heat transfer fluids. The system uses its own working material (the circulating bed solids) to perform the storage function, turning an existing operational requirement into a dual-purpose component that reduces overall equipment needs and investment costs.
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 solution provides a cost-effective and flexible energy storage system that enhances power plant efficiency and reduces operational penalties, allowing for stable operation across varying power outputs without the need for frequent shutdowns, thus improving economic viability and environmental performance.
Implementation Method 1
a first fluidized bed heat exchanger, the first fluidized bed heat exchanger receiving the higher temperature solids from the higher temperature silo and discharging lower temperature solids to the circulating fluidized bed combustor
Implementation Method 2
a first cyclone for separating the resulting hot flue gas and the hot solids stream circulating to the circulating fluidized bed combustor
Implementation Method 3
another reactor that captures CO2 with CaO, thereby enhancing the energy storage density in the system by using the enthalpy of the reversible reaction of CO2 with CaO
Implementation Method 4
part of the thermal energy released during periods of maximum power output comes from the carbonation of CaO and in periods of low power output part of the thermal energy released during combustion is used to calcine CaCO3 and store CaO
Implementation Method 5
the first fluidized bed heat exchanger receiving the higher temperature solids from the higher temperature silo and discharging lower temperature solids to the circulating fluidized bed combustor
Data Source
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AI summary
This invention relates to a system and a method for large scale energy storage in power generation systems using circulating fluidized bed combustors wherein the system can be further interconnected with another reactor that captures CO2 with CaO, thereby enhancing the energy storage density in the system by using the enthalpy of the reversible reaction of CO2 with CaO, wherein the system and the method of this invention are characterized by a large flexibility between periods of maximum power output and complementary periods of low power output, wherein at maximum power output, a circulation of solids from a high temperature silo to a low temperature silo is established through the system of the invention and at minimum power output, part of the thermal energy released in the circulating fluidized bed combustor is used to heat up solids from the low temperature silo and store them in the high temperature silo.