Chemical Looping Combustion Process with Segmented Reaction Zones
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Solution Overview
Problem
Chemical loop combustion processes face inefficiencies in achieving total combustion of solid fuels due to short residence times and high gas velocities, leading to incomplete combustion and significant CO and H2 emissions, requiring post-combustion zones and costly energy for particle separation.
Innovation Solution
The process optimizes contact between oxygen-carrying particles and solid fuels in a dense fluidized bed for gasification, followed by a diluted fluidized bed for complete combustion of gaseous effluents, with a separation zone utilizing a gas flow to efficiently separate unburned particles from metal oxide particles, maximizing energy efficiency and CO2 capture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high gas velocities are used in the reduction reactor operating in a circulating fluidized bed to enhance combustion, then combustion rate is improved, but residence time becomes too short to gasify all solid fuel and achieve total combustion
Solution Approach 1:
The invention divides the combustion process into two distinct reaction zones: a first reduction reactor for gasification and a second combustion reactor for complete combustion. This segmentation allows each zone to be optimized independently - the first reactor can operate at lower velocities for adequate residence time, while the second reactor handles the combustion of gaseous products, thereby resolving the contradiction between high velocity and sufficient residence time.
2Productivity
If the fuel is crushed before entering the reduction reactor to enable more complete and rapid combustion, then combustion efficiency is improved, but the separation of unburnt particles from oxide particles becomes more difficult and requires additional gas supply
Solution Approach 1:
The invention extracts and removes unburnt particles from the circulation loop through a dedicated separation device positioned between the two reactors. This extracted unburnt material is then separately combusted and the products injected into the second reactor. This extraction approach allows coarse fuel particles to be used without compromising combustion efficiency, while avoiding the need for additional gas supply for particle separation.
3Quantity of substance
If significant quantities of metal oxides are used to burn all the fuel, then combustion capacity is improved, but the implementation requires sophisticated separation equipment with two internal compartments
Solution Approach 1:
The invention introduces an intermediary separation device that acts as a mediator between the two reaction zones. This device separates unburnt particles from oxide particles using density differences in a fluidized bed, with unburnt particles being extracted and separately combusted. This intermediary approach simplifies the overall system by avoiding the need for complex two-compartment separation equipment while still enabling efficient use of metal oxides.
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 achieves over 90% CO2 capture rate and minimizes solid charge recycling, ensuring total combustion with reduced energy consumption and improved combustion efficiency, resulting in CO and H2 levels below 1% in the fumes.
Implementation Method 1
a first reaction zone (R1) operating in a dense fluidized bed and making it possible to gasify the solid charge particles in the presence of metal oxide particles
Implementation Method 2
a second combustion or reduction reaction zone (R2) operating in a diluted fluidized bed and allowing the combustion of gaseous effluents from the first reaction zone (R1) in the presence of metal oxide particles
Implementation Method 3
a separation zone (S3) carrying out a separation within a mixture containing gas, unburnt particles, metal oxide particles, said mixture coming from the second reaction zone (R2), and said zone separation comprising an enclosure within which the admission of the mixture of particles to be separated is carried out in a diluted phase in which a gas flows at an imposed speed
Data Source
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AI summary
The subject of the invention is a chemical looping combustion process for combusting a solid feedstock, in which loop an oxygen-carrying material flows, said process comprising at least: bringing the solid feedstock particles into contact with metal-oxide particles in a first reaction zone (R1) operating as a dense-fluidized bed; combusting the exhaust gases obtained from the first reaction zone (R1) in the presence of metal-oxide particles in a second reaction zone (R2); separating from a mixture obtained from the second zone (R2), in a separation zone (S3), the gas, the unburnt particles and the metal-oxide particles; and reoxidizing the metal-oxide particles in an oxidation zone (R4) before returning them to the first zone (R1).