CO and CO2 Cryogenic Separation from FCC Partial Burn Flue Gas
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Solution Overview
Problem
Fluid catalytic cracking (FCC) units operating with partial burn regenerators face challenges in treating flue gases containing CO2, CO, and sulfur compounds, leading to high capital and operational expenditures due to the need for extensive flue gas treatment and CO2 capture, which also results in increased NOx generation and solvent degradation.
Innovation Solution
A process involving the separation of CO from CO2 in flue gas streams using cryogenic fractionation, pressure swing adsorption (PSA), or temperature swing adsorption (TSA) processes, combined with dry or wet sorbent injection to reduce sulfur content, and a heat recovery steam generator (HRSG) to optimize energy recovery and reduce contaminant levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wet gas scrubbing technology is used to remove sulfur compounds from flue gas, then sulfur removal efficiency is improved, but capital and operational expenditures increase and solvent degradation occurs
Solution Approach 1:
The patent extracts and removes sulfur compounds from flue gas using dry sorbent injection technology, separating the harmful component before further processing. This extraction approach avoids the complexity of wet scrubbing systems while achieving effective sulfur removal through adsorption on solid sorbent materials.
Solution Approach 2:
The patent employs disposable dry sorbent materials that are injected into the flue gas stream to capture sulfur compounds. These sorbents are consumed in the process and replaced periodically, eliminating the need for complex solvent regeneration systems and reducing both capital and operational expenditures compared to wet scrubbing technology.
2Manufacturing precision
If extensive flue gas treatment and CO2 capture are implemented, then CO2 separation is improved, but capital and operational expenditures increase
Solution Approach 1:
The patent segments the flue gas treatment process into distinct functional stages: sulfur removal using dry sorbent injection, followed by CO2 separation using selective absorption or adsorption technologies. This segmentation allows each stage to be optimized independently, achieving high CO2 separation purity without requiring excessively complex integrated systems.
Solution Approach 2:
The patent introduces intermediary substances such as selective solvents or adsorbent materials that mediate between the flue gas and the separation process. These intermediaries selectively interact with CO2 molecules, enabling efficient separation from other flue gas components while maintaining system simplicity and reducing operational costs.
3Quantity of substance
If partial burn regenerator mode is used to maximize CO yield, then CO production is improved, but NOx generation increases
Solution Approach 1:
The patent converts the harmful NOx generated during partial burn regeneration into a benefit by implementing downstream NOx treatment technologies. The process captures and transforms NOx emissions, either through selective catalytic reduction or other conversion methods, turning this harmful byproduct into useful products or harmless substances, thereby maintaining high CO yield while mitigating NOx environmental impact.
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 reduces capital and operational costs by improving the efficiency of flue gas treatment, minimizing solvent degradation, and decreasing NOx generation, while effectively separating CO2 and CO, thereby enhancing the overall economic and environmental performance of FCC units.
Implementation Method 1
transferred heat from the flue gas stream to a boiler feed water stream in a heat recovery section to form a partially cooled flue gas stream and a steam stream
Implementation Method 2
separating the cooled reactor effluent stream into a CO2 product stream, a CO2 recycle stream, and a CO product stream
Implementation Method 3
separation of CO from CO2 in flue gas streams using cryogenic fractionation
Implementation Method 4
pressure swing adsorption (PSA) processes, combined with dry or wet sorbent injection to reduce sulfur content
Implementation Method 5
temperature swing adsorption (TSA) processes
Implementation Method 6
dry or wet sorbent injection to reduce sulfur content
Data Source
AI summary
Processes for separating CO from CO2 in flue gas streams from partial oxidation regenerator in FCC processes, as well as reducing the sulfur content of the flue gas stream are described. The processes involve separating the cooled reactor effluent stream into a CO2 product stream, the CO2 recycle stream, and a CO product stream. The processes may incorporate either dry sorbent injection (DSI) units or wet gas scrubbing units to remove sulfur compounds. The separation processes can utilize cryogenic fractionation, pressure swing adsorption (PSA) processes including vacuum PSA, and temperature swing adsorption (TSA) processes. The flue gas stream can be used to preheat the CO2 recycle stream.