FCC Catalyst Regeneration With Staged Hot Stripping
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Solution Overview
Problem
Conventional Fluidized Catalytic Cracking (FCC) processes face inefficiencies in stripping catalyst particles, leading to excessive heat production, coke yield loss, and increased emissions of SOx and NOx, due to insufficient stripping and regeneration methods.
Innovation Solution
A two-stage regeneration process integrated with hotter stripping and oxycombustion, where spent catalyst is partially regenerated in the first stage and fully regenerated in the second stage, with a portion of fully regenerated catalyst returned to the riser reactor and stripper vessel for enhanced stripping efficiency, reducing coke load and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional stripping methods are used in FCC processes, then the process is simpler to operate, but insufficient stripping results in excessive heat production and coke yield loss during regeneration
Solution Approach 1:
The invention divides the stripping process into multiple stages with different temperatures. The first stage uses hot regenerated catalyst (500-750°C) to perform initial stripping, while the second stage uses cooler catalyst to complete the stripping process. This segmentation allows efficient hydrocarbon removal while controlling temperature to prevent excessive coke formation and heat loss.
Solution Approach 2:
The invention changes the temperature parameter of the stripping process by using catalyst at different temperatures in different stages. Hot catalyst (500-750°C) is used in the first stage to maximize stripping efficiency, then cooler catalyst is used in the second stage to complete stripping while controlling heat input. This parameter optimization resolves the contradiction between stripping efficiency and heat loss.
2Productivity
If hotter staged stripping is implemented by direct blending hot regenerated catalyst with spent catalyst, then stripping efficiency improves, but the regenerator operation may be interfered with due to temperature changes
Solution Approach 1:
The invention segments the catalyst circulation into separate streams: one stream goes through the hot stripping stage, another through the cool stripping stage, and a third stream bypasses the stripper entirely. This segmentation allows hot catalyst to be used for stripping without disrupting the overall regenerator operation, as the bypass stream maintains stable regenerator conditions.
Solution Approach 2:
The invention uses a bypass stream as an intermediary element that connects the regenerator to the reactor, allowing part of the catalyst to bypass the stripper. This intermediary pathway enables temperature adjustments in the stripping zones without directly affecting regenerator stability, as the bypass catalyst maintains the regenerator's thermal and operational balance.
3Temperature
If oxycombustion mode is used in regenerator, then temperature peaks are avoided, but large-scale equipment and extra energy consumption are required to reprocess and recycle CO2
Solution Approach 1:
The invention changes the oxygen concentration parameter in the regenerator by using oxygen-enriched air (21-30% O2) instead of pure oxygen. This parameter adjustment maintains the benefits of controlled combustion and temperature management while avoiding the need for large-scale CO2 reprocessing equipment, as the lower oxygen concentration naturally produces less CO2 requiring treatment.
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
The process achieves reduced coke load, sulfur, and nitrogen combustion, along with decreased emissions of SOx and NOx, while facilitating higher carbon utility efficiency and integration with coke gasification.
Implementation Method 1
A gaseous fluid injected at the bottom of the chamber is used to fluidize the coked catalyst particles and displace the entrained hydrocarbons located in the interstitial spaces between the particles
Implementation Method 2
It is preferential to use a polar material, such as steam, for this gaseous fluid, as it is more strongly adsorbed by the catalyst particles and thus the hydrocarbons are more readily displaced
Implementation Method 3
the hydrocarbons are more readily displaced
Implementation Method 4
A second portion of the fully regenerated catalyst is provided to the stripper vessel to mix with the spent catalyst for better stripping efficiency
Implementation Method 5
hotter staged stripping methods by direct blending hot regenerated catalyst with FCC spent catalyst in FCC stripper
Implementation Method 6
regenerating the spent catalyst by burning the coke formed thereon
Implementation Method 7
regenerating the spent catalyst in a first regeneration stage to produce a partially regenerated catalyst
Implementation Method 8
Fluidized beds are usually generated by passing a fluid stream, typically a vapor stream, upwardly through a bed of solid particles at a flow rate sufficient to suspend the particles and cause a gas solid mixing within the bed
Data Source
AI summary
A fluid catalytic cracking process includes regenerating a spent catalyst from a stripper vessel in a first regeneration stage to produce a partially regenerated catalyst, regenerating the partially regenerated catalyst in second regeneration stage to produce a fully regenerated catalyst, and providing a first portion of the fully regenerated catalyst to a riser reactor. The process includes generating the spent catalyst with the riser reactor and providing the spent catalyst to a stripper vessel and providing a second portion of the fully regenerated catalyst to the stripper vessel to mix with the spent catalyst for better stripping efficiency and prompting further reactions, resulting in overall reduced coke load, sulfur, and nitrogen to be burned, and providing necessary heat needed for the following coke gasification to produce synthesis gas in the first regeneration stage.