Two-Stage FCC Regenerator Oxygen Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fluid catalytic cracking (FCC) units face challenges in reducing carbon dioxide emissions, particularly due to the burning of catalyst coke in the regenerator, which requires careful oxygen management to balance catalyst regeneration and synthesis gas quality.
Innovation Solution
Implementing a two-stage regeneration process in the FCC unit, where the first stage uses oxygen to consume coke and produce synthesis gas, and the second stage further regenerates the catalyst with controlled oxygen input to maximize synthesis gas quality and minimize carbon dioxide emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen is added to the regenerator to burn coke from catalyst, then catalyst regeneration is improved, but carbon dioxide emissions increase
Solution Approach 1:
The regenerator is divided into multiple zones (first zone with lower oxygen concentration and second zone with higher oxygen concentration) to segment the oxidation process. This allows partial oxidation to produce synthesis gas in the first zone and complete oxidation to remove remaining coke in the second zone, thereby reducing overall CO2 emissions while maintaining catalyst regeneration effectiveness.
Solution Approach 2:
The oxygen concentration parameter is varied spatially within the regenerator - lower concentration in the first zone to favor synthesis gas production and higher concentration in the second zone to ensure complete coke removal. This parameter change optimizes the balance between synthesis gas yield and CO2 emission reduction.
2Reliability
If excess oxygen is used to ensure complete catalyst regeneration, then regeneration completeness is improved, but synthesis gas quality deteriorates due to secondary combustion
Solution Approach 1:
The regenerator is divided into a first zone where partial oxidation occurs with limited oxygen to produce synthesis gas, and a second zone where complete oxidation occurs with sufficient oxygen to remove remaining coke. This segmentation prevents secondary combustion of synthesis gas while ensuring complete regeneration.
Solution Approach 2:
The first zone performs preliminary oxidation to convert a portion of coke to synthesis gas before the catalyst enters the second zone for final regeneration. This preliminary action reduces the coke load before complete oxidation, preventing excessive CO2 generation and maintaining synthesis gas quality.
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 effectively regenerates the catalyst while maximizing synthesis gas output and reducing overall carbon dioxide emissions by optimizing oxygen use and preventing secondary combustion reactions.
Implementation Method 1
regenerating spent catalyst in a fluidized catalytic cracking unit while improving the quality of a synthesis gas... a first stage reaction between a first stage regeneration gas comprising oxygen and spent catalyst from the reactor in the first stage of the regenerator to consume the oxygen in the first stage regeneration gas... The first stage reaction produces a synthesis gas
Implementation Method 2
a second stage reaction between a second stage regeneration gas comprising oxygen and the partially regenerated catalyst in the second stage of the regenerator to regenerate the partially regenerated catalyst
Implementation Method 3
The fluidized catalyst is continuously circulated from the reaction zone to the regeneration zone and then again to the reaction zone. The fluidized catalyst, as well as providing a catalytic function, acts as a vehicle for the transfer of heat from zone to zone.
Implementation Method 4
The cracking reaction deposits coke on the catalyst. Coke is comprised of hydrogen and carbon and can include other materials in trace quantities such as sulfur and metals that enter the process with the starting material. Coke interferes with the catalytic activity of the catalyst by blocking active sites on the catalyst surface
Data Source
AI summary
Systems and methods of improving synthesis gas quality in a fluid catalytic cracking unit are disclosed. In one example, a method comprises reacting a first stage regeneration gas comprising oxygen with spent catalyst from a reactor in a first stage of a regenerator to consume the oxygen in the first stage regeneration gas. This reaction produces a synthesis gas output and partially regenerated catalyst. The method further comprises reacting a second stage regeneration gas comprising oxygen with the partially regenerated catalyst in a second stage of the regenerator to regenerate the partially regenerated catalyst. This reaction produces the first stage regeneration gas for reaction with the spent catalyst in the first stage of the regenerator. Through the first and second stage reactions, the spent catalyst is regenerated and the synthesis gas quality is improved.