Catalyst Regeneration via Dense Phase Mixing to Reduce NOx
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Solution Overview
Problem
Current catalyst regeneration systems in fluid catalytic crackers produce undesirable byproducts like nitrogen oxides (NOx) during the combustion process, which need to be reduced to meet environmental regulations.
Innovation Solution
A method involving mixing spent catalyst with an oxygen-containing carrier fluid and introducing it to a dense phase catalyst zone within a regenerator, where the carbon deposits are combusted using an oxidant, reducing NOx formation by increasing CO and carbon concentrations, and utilizing a CO oxidation promoter to control combustion temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional combustion process is used to regenerate catalyst, then coke is removed from catalyst surface, but nitrogen oxides (NOx) are generated as undesirable byproducts
Solution Approach 1:
The patent changes the combustion parameters by controlling oxygen concentration, temperature, and residence time in the regenerator. By maintaining lower oxygen concentrations (1-10% O2) and controlling the combustion zone temperature, the process achieves effective coke removal while minimizing NOx formation through parameter optimization
Solution Approach 2:
The patent converts the harmful effect of carbon monoxide (which can lead to incomplete combustion) into a benefit by using it as a reducing agent. The CO generated during combustion reduces NOx to nitrogen gas through the reaction: 2NO + 2CO → N2 + 2CO2, thereby converting a potential harmful byproduct into a mechanism for reducing NOx emissions
2Productivity
If combustion temperature is increased to improve regeneration efficiency, then coke combustion rate increases, but NOx formation increases
Solution Approach 1:
The patent divides the regenerator into distinct zones: a combustion zone where coke is burned at controlled temperatures, and a separate CO oxidation zone where CO is converted to CO2. This segmentation allows each zone to operate at optimized temperatures - the combustion zone maintains lower temperatures to minimize NOx, while the CO oxidation zone operates at higher temperatures to ensure complete combustion and CO conversion
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 significantly reduces NOx concentrations in the flue gas to below 150 ppm, maintaining operational temperature limits and enhancing catalyst regeneration efficiency.
Implementation Method 1
mixing a spent catalyst with a carrier fluid to provide a mixture
Implementation Method 2
combusting at least a portion of the carbon deposited on the catalyst to provide a flue gas, heat, and a regenerated catalyst
Implementation Method 3
utilizing a CO oxidation promoter to control combustion temperatures
Implementation Method 4
introducing the mixture to or above an upper surface of a dense phase catalyst zone disposed within a regenerator
Data Source
AI summary
Systems and methods for regenerating a spent catalyst are provided. The method can include mixing a spent catalyst with a carrier fluid to provide a mixture. The spent catalyst can include carbon deposited on at least a portion thereof. The carrier fluid can include an oxygen containing gas. The mixture can be introduced to or above an upper surface of a dense phase catalyst zone disposed within a regenerator. A gas can be introduced to a lower zone of the dense phase catalyst zone. At least a portion of the carbon deposited on the catalyst can be combusted to provide a flue gas, heat, and a regenerated catalyst.