Flat-Roof Chemical Looping Combustion Reactor Design
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Solution Overview
Problem
The pistoning phenomenon and associated strong pressure fluctuations in fluidized bed reactors during chemical loop combustion (CLC) processes lead to mechanical stress, temperature heterogeneity, and poor gas-particle mixture homogeneity, which negatively impact the efficiency and integrity of the combustion process.
Innovation Solution
A CLC combustion reactor with a specific geometry featuring a lower dense fluidized bed and an upper diluted fluidized bed connected by an intermediate part with a right-angle internal wall, along with secondary and tertiary fluidization gas injection systems, is designed to break up solid agglomerates and control the dense bed level, reducing pressure fluctuations and enhancing mixture homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fluidized bed reactor operates in pistoning or turbulent regime to enhance combustion efficiency, then combustion efficiency is improved, but pressure fluctuations and mechanical stress increase
Solution Approach 1:
The reactor is divided into multiple zones with different fluidization regimes: a lower dense fluidized bed zone for stable operation and an upper dilute fluidized bed zone for enhanced combustion efficiency. This segmentation allows each zone to perform its specific function while preventing pistoning phenomenon from affecting the entire reactor.
Solution Approach 2:
Different regions of the reactor are assigned different fluidization characteristics. The lower chamber operates in dense fluidization regime with lower gas velocities to maintain stability, while the upper chamber operates in dilute fluidization regime with higher gas velocities to enhance combustion efficiency. This local differentiation resolves the contradiction between stability and efficiency.
2Productivity
If gas velocity is increased to achieve dilute fluidized bed regime, then combustion efficiency is improved, but temperature homogeneity deteriorates
Solution Approach 1:
The reactor is divided into a lower dense fluidized bed zone where temperature homogeneity is maintained through intensive mixing, and an upper dilute fluidized bed zone where combustion efficiency is enhanced. The segmented structure allows temperature homogeneity and combustion efficiency to be optimized in their respective zones without compromising each other.
3Duration of action of moving object
If dense fluidized bed is used for solid fuel combustion, then contact time is sufficient, but gas-particle mixture homogeneity deteriorates
Solution Approach 1:
The reactor structure segments the dense fluidized bed zone and dilute fluidized bed zone, allowing solid fuel combustion with sufficient contact time in the lower zone, while the upper zone provides enhanced gas-particle mixing and homogeneity through dilute fluidization and the flat roof structure.
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 configuration effectively limits pressure fluctuations, ensures temperature and mixture homogeneity, and maintains the mechanical integrity of the reactor, optimizing the combustion process by preventing pistoning and turbulence-related issues.
Implementation Method 1
The particles are brought into contact in the reaction zones with either the oxidizing gas or the feedstock, forming fluidized beds
Implementation Method 2
a first oxidation reaction of the active mass in contact with an oxidizing gas, typically air, in at least one oxidation zone
Implementation Method 3
a second reduction reaction of the active mass in contact with the feedstock whose combustion is desired in at least one combustion zone
Implementation Method 4
The CLC process makes it possible to produce energy (steam, electricity, etc.) by recovering the heat released by combustion reactions
Data Source
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AI summary
The present invention concerns a combustion reactor (300) for chemical looping combustion (CLC) configured to operate in a fluidised bed, comprising: a lower chamber (320) forming a first reaction zone for the combustion of a hydrocarbon feedstock in the presence of particles of an oxidation-reduction active mass, comprising a first side wall and being configured to include a dense fluidised bed; an elongate upper chamber (340) with smaller passage cross-section than that of the lower chamber, forming a second reaction zone for the combustion of gaseous effluents originating from the combustion in the lower portion, comprising a second side wall and being configured to include a dilute fluidised bed; an intermediate portion (330) connecting the two chambers, and including an inner wall forming a right angle with the side walls of the two chambers. The invention also relates to the facility and the CLC process incorporating such a reactor (300).