Transport Oxy-combustor Temperature Control via Solids Circulation
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Solution Overview
Problem
Existing oxy-combustion systems for coal-fired electricity generation face challenges such as high energy consumption, reduced operational reliability, and increased costs due to large flue gas recycling, excess oxygen in the CO2 stream, and high calcium-to-sulfur ratios required for sulfur removal, which hinder efficient CO2 capture and sulfur emission control.
Innovation Solution
A transport oxy-combustor design that includes a riser with a primary oxygen feed, a solids fuel stream, and a solids cooler, where the solids circulation rate is significantly higher than the fuel stream, allowing for complete combustion and efficient sulfur capture with lower calcium-to-sulfur ratios, and incorporating a scavenging fuel to remove excess oxygen, operating at elevated pressures to enhance process efficiency and reduce equipment size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If large amounts of flue gas are recycled to control combustor temperature, then combustion temperature control is improved, but energy consumption increases and operational reliability decreases
Solution Approach 1:
The patent introduces an intermediary cooling system using water/steam injection into the combustor to control temperature, replacing the need for large flue gas recycling. This intermediary substance (water) absorbs heat during evaporation and provides efficient temperature control without the energy penalties of recycling large gas volumes.
Solution Approach 2:
The patent changes the thermal parameters by injecting water at controlled rates and locations, transforming the temperature control mechanism from gas recycling to liquid vaporization. This parameter change enables more efficient heat removal with lower energy consumption and improved operational reliability.
2Temperature
If flue gas is recycled in large amounts to control temperature, then temperature regulation is improved, but operational reliability deteriorates
Solution Approach 1:
The water/steam injection system serves as an intermediary temperature control mechanism that is more reliable than flue gas recycling. The liquid injection system has fewer operational constraints and can more reliably maintain temperature control under varying load conditions without the complexity of large gas circulation loops.
3Object-generated harmful factors
If high calcium-to-sulfur ratios are used for sulfur removal, then sulfur capture efficiency is improved, but capital costs and equipment size increase
Solution Approach 1:
The patent changes the chemical parameters of the combustion environment, specifically the oxygen concentration and temperature profile, to optimize sulfur capture efficiency. By controlling these parameters, the system achieves effective sulfur removal with lower calcium-to-sulfur ratios, reducing the size and cost of sulfur capture equipment.
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 transport oxy-combustor achieves efficient combustion with minimal recycled CO2, reduced oxygen levels in the flue gas, and lower sorbent requirements, resulting in improved energy throughput, reduced capital costs, and effective sulfur capture, enabling the production of a high-purity CO2 stream suitable for sequestration.
Implementation Method 1
a solids cooler with an exit cooler solids stream
Implementation Method 2
the fuel is combusted with substantially pure oxygen (O2) in a riser in a substantially complete oxidation
Implementation Method 3
after condensing moisture out of the flue gas
Data Source
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AI summary
A pressurized transport oxy-combustor with different configurations is disclosed. Substantially pure oxygen is fed to the transport oxy-combustor under pressure to combust fossil fuels, generating steam for power generation. The end product is the flue gas containing substantially pure CO2 after moisture condensation. The low excess oxygen necessary to achieve complete combustion in the combustor is scavenged by adding another fuel so that substantially all oxygen fed to the combustor is completely consumed. The capability to operate the transport oxy-combustor as a circulating fluidized bed combustor at very high solids circulation rates makes it unnecessary to use recycled CO2 or flue gas as a means to moderate and control the combustion temperature. The temperature in the combustor is effectively controlled by relatively cooler circulating solids that enter the combustion zone (200). A small amount of CO2 is recycled for aeration and to convey solids fuel to the combustor.