Dual Reactor Cracking Process for Propylene Yield Optimization
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Solution Overview
Problem
Existing FCC processes face challenges in maximizing the yield of propylene and minimizing dry gas formation, particularly in dual reactor systems where optimizing conditions for one reactor can impact the other.
Innovation Solution
A process involving isomerization of a paraffin-rich hydrocarbon feed to create an iso-paraffin-rich stream, which is then cracked in a first reactor riser with a specific catalyst mixture, followed by oligomerization of a dilute ethylene stream and further cracking in a second reactor riser to enhance propylene production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dual reactor system is used to maximize propylene yield, then propylene production is improved, but dry gas formation increases
Solution Approach 1:
The process divides the cracking operation into two separate reactor risers with different catalyst compositions. The first reactor uses a catalyst optimized for propylene production, while the second reactor uses a catalyst optimized for minimizing dry gas. This segmentation allows each reactor to be optimized for its specific function, resolving the contradiction between propylene yield and dry gas formation.
Solution Approach 2:
Different catalyst compositions are applied to different locations (reactors) in the system. The first reactor receives a catalyst with higher cracking activity for propylene production, while the second reactor receives a catalyst with modified properties to suppress dry gas formation. This local differentiation of catalyst quality enables simultaneous optimization of both objectives.
2Productivity
If reactor conditions are optimized for maximizing propylene, then propylene production is improved, but dry gas formation increases
Solution Approach 1:
The process changes the catalyst parameters (composition and properties) rather than operating parameters (temperature, pressure, space velocity) to resolve the contradiction. By selecting catalysts with different intrinsic properties for different reactors, the system achieves both high propylene production and low dry gas formation without compromising operating conditions.
3Device complexity
If a single reactor system is used, then device complexity is reduced, but propylene yield optimization is limited
Solution Approach 1:
The system segments the single reactor into two separate reactor risers, each with its own optimized catalyst. This segmentation enables independent optimization of propylene production in the first reactor while the second reactor handles dry gas minimization, achieving higher overall propylene yield despite increased device complexity.
4Productivity
If additional capital costs are incurred for a dual reactor system, then propylene production is improved, but investment cost increases
Solution Approach 1:
The dual reactor system is designed to perform multiple functions: the first reactor maximizes propylene production while the second reactor simultaneously minimizes dry gas formation and can recycle products back to the first reactor. This multi-functionality justifies the additional capital investment by achieving multiple optimization goals simultaneously.
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 increases propylene yield and minimizes dry gas formation by optimizing the reaction conditions in a dual reactor system, leveraging the selective cracking properties of iso-paraffins and tailored catalyst compositions.
Implementation Method 1
passing a feed stream to an isomerization unit to provide a first hydrocarbon stream rich in iso-paraffins
Implementation Method 2
contacting a first hydrocarbon stream with a first stream of fluid catalyst in a first reactor riser to produce a first mixture of spent catalyst and product gases
Implementation Method 3
a dilute ethylene stream is separated from the first cracked product stream which is oligomerized to produce a second hydrocarbon stream comprising C4+ oligomers
Data Source
AI summary
We have discovered a process for catalytic production of olefins comprising passing a feed stream to an isomerization unit to provide a first hydrocarbon stream rich in iso-paraffins. The first hydrocarbon stream is contacted with a first stream of fluid catalyst in a first reactor riser to produce a first mixture of spent catalyst and product gases. The first mixture of spent catalyst and product gases is separated into a first cracked product stream and a first stream of cool catalyst. A dilute ethylene stream is separated from the first cracked product stream which is oligomerized to produce a second hydrocarbon stream comprising C4+ oligomers. The second hydrocarbon stream is contacted with a second stream of fluid catalyst in a second reactor riser to produce a second mixture of spent catalyst and product gases.