FCC Regenerator NOx Reduction via Oxygen and Temperature Control
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Solution Overview
Problem
The Fluid Catalytic Cracking (FCC) process generates high NOx emissions during catalyst regeneration, which is environmentally undesirable and requires a method to reduce these emissions while ensuring complete coke removal from the catalyst.
Innovation Solution
Implementing an FCC process with reduced excess oxygen levels (≤0.5 mol-%) and a plenum temperature above 730°C (1350°F), along with limiting platinum content and adjusting metal content in the feedstock, such as antimony, nickel, and vanadium, and using NOx-reducing catalysts and ammonia injection to minimize NOx production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If excess oxygen levels are increased to ensure complete coke combustion, then coke removal efficiency is improved, but NOx emissions increase
Solution Approach 1:
The patent applies parameter changes by operating the regenerator at reduced excess oxygen levels (≤0.5 mol-%) and elevated temperatures (≥730°C), fundamentally altering the combustion parameters to suppress NOx formation while maintaining coke removal efficiency through optimized oxygen-catalyst interaction
Solution Approach 2:
The patent converts the potentially harmful effect of limited oxygen into a beneficial outcome by using restricted oxygen availability to suppress thermal NOx formation mechanisms, while the catalyst facilitates complete coke oxidation through alternative pathways that do not produce NOx
2Productivity
If platinum promoter is added to accelerate CO combustion, then CO conversion is improved, but NOx emissions increase
Solution Approach 1:
The patent removes the platinum promoter from the catalyst system, extracting the harmful component that catalyzes NOx formation while retaining the ability to achieve CO conversion through alternative non-platinum catalytic pathways and optimized combustion conditions
3Speed
If regenerator temperature is increased to enhance coke combustion rate, then regeneration speed is improved, but NOx production increases
Solution Approach 1:
The patent changes the temperature parameter to operate at elevated levels (≥730°C) combined with reduced excess oxygen, creating a unique operational window where thermal energy drives coke combustion while oxygen limitation prevents thermal NOx formation mechanisms from activating
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 decreases NOx emissions to below 20 ppmv, achieving lower environmental impact while ensuring effective catalyst regeneration.
Implementation Method 1
Regeneration occurs by oxidation of the carbonaceous deposits to carbon oxides and water
Implementation Method 2
accelerating the combustion of coke and CO to CO2
Implementation Method 3
cracking heavy hydrocarbons into lighter hydrocarbons by bringing the heavy hydrocarbons into contact with a catalyst
Data Source
AI summary
An FCC process producing lower NOx emissions during regeneration by using excess oxygen levels at less than or equal to about 0.5 mol-% and a plenum temperature above about 730° C. (about 1350° F.). The process may further include limiting the Pt content in the catalyst to less than or equal to about 0.5 ppm. NOx emissions, NO to NO2, produced through this process may be equal to or less than 25 ppmv. The process may also include adjusting the metal content of the feedstock for such metals as antimony, nickel, or vanadium. Additional variables for reducing NOx emissions that may be used in conjunction with this process may include increasing the flue gas residence time, injecting NH3 into the flue gas, adding or using NOx-reducing catalysts, increasing stripping of the catalyst, and increasing the catalyst zeolite to matrix ratio.