Multi-Stage Fluidized Catalytic Reactor for Propylene Yield
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Solution Overview
Problem
Existing petroleum hydrocarbon catalytic conversion processes, such as DCC and DCC-PLUS, face challenges in maximizing propylene yield while minimizing by-products like dry gas and coke due to catalyst degradation and inefficient reaction temperature control, leading to reduced selectivity and increased side reactions.
Innovation Solution
A multi-stage fluidized catalytic reaction process that partitions reactions into different regions within the same reactor, employing catalyst replacement and controlled temperature conditions to optimize propylene selectivity, featuring a riser reactor for initial cracking, followed by a turbulent or circulating fluidized bed for secondary cracking, with steam fluidization to manage catalyst activity and reaction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reaction temperature in the fluidized bed region is increased to improve propylene yield through pyrolysis, then the propylene yield increases, but the selectivity of propylene decreases sharply and the yield of dry gas and coke increases
Solution Approach 1:
The reaction system is divided into two independent parallel reactors: a riser reactor for primary catalytic cracking and a fluidized bed reactor for secondary cracking. This segmentation allows each reactor to operate under optimized conditions - the riser at lower temperatures for high selectivity and the fluidized bed at higher temperatures for additional propylene production without compromising overall selectivity
Solution Approach 2:
A gas-solid separator is introduced as an intermediary component between the two reactors to quickly separate catalyst and product gas. This intermediary enables rapid transition from the riser to the fluidized bed, minimizing residence time and preventing unwanted side reactions while maintaining high propylene selectivity
2Productivity
If the residence time of oil gas in the fluidized bed region is extended to allow complete reaction, then the conversion improves, but further side reactions occur affecting propylene selectivity and product distribution
Solution Approach 1:
The system uses high-velocity gas flow and a gas-solid separator to rapidly transport oil gas from the riser through the fluidized bed and into the separator. This 'rushing through' approach minimizes residence time in the fluidized bed to just enough time for secondary cracking, preventing extended exposure that would cause unwanted side reactions while still achieving high conversion
3Device complexity
If a single reactor system is used for both primary and secondary cracking, then the device complexity is reduced, but the selectivity of propylene cannot be optimized due to catalyst degradation and temperature control limitations
Solution Approach 1:
The system employs two separate reactors - a riser reactor for primary cracking with fresh catalyst and a fluidized bed reactor for secondary cracking with circulated catalyst. This segmentation allows independent optimization of each reaction stage, maintaining high propylene selectivity while achieving complete conversion through the coordinated operation of both reactors
Solution Approach 2:
Each reactor operates with different key parameters: the riser uses lower temperature and fresh catalyst for high selectivity primary cracking, while the fluidized bed uses higher temperature and circulated catalyst for secondary cracking. These parameter changes enable each stage to perform its specific function optimally, achieving both high selectivity and complete 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 enhances propylene yield, reduces by-product formation, and improves catalyst efficiency, resulting in increased economic efficiency by maintaining suitable reaction environments for different feedstocks and controlling carbon content in the catalyst.
Implementation Method 1
catalytic cracking reaction takes place in both riser reactor and fluidized bed reactor
Implementation Method 2
steam fluidization to manage catalyst activity and reaction conditions
Implementation Method 3
it need to increase the reaction temperature in order to improve the yield of propylene by pyrolysis
Data Source
AI summary
A petroleum hydrocarbon multi-stage fluid catalytic reaction method and reactor are described. The method implements a sectional multi-stage reaction in one reactor and comprises primary-stage and secondary-stage catalytic cracking reactions of feedstock oil and primary-stage and secondary-stage catalytic cracking reactions of light hydrocarbons and/or cycle oil, which occur in different reaction regions of the reactor. The primary-stage reaction of the light hydrocarbon and/or circulation oil is carried out in an independent reaction region. The reactor comprises a first reaction section, a catalyst splitter, a third reaction section, a second reaction section and a settler.