Dual-Fluidized Bed Reactor for Cracking Light and Heavy Feedstocks
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Solution Overview
Problem
Existing fluid catalytic cracking (FCC) processes face challenges in efficiently converting lighter hydrocarbon feedstocks due to their difficulty in cracking and the need for optimized contact time and catalyst usage to maximize light olefin production.
Innovation Solution
The implementation of a dual-reactor system comprising a dense fluidized bed reactor for longer contact time and a transport fluidized bed reactor for shorter contact time, allowing for the sequential cracking of lighter and heavier feedstocks with a more active catalyst, thereby enhancing light olefin production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single reactor is used for FCC processing, then the device complexity is low, but the ability to treat multiple feedstock types with different contact times is limited
Solution Approach 1:
The single reactor is segmented into multiple zones with different contact times (first zone with longer contact time for lighter feedstocks, second zone with shorter contact time for heavier feedstocks). This allows different feedstock types to be processed simultaneously in the same reactor while maintaining optimal contact times for each, thereby increasing versatility without adding multiple separate reactors.
Solution Approach 2:
Different zones within the reactor are assigned different local qualities - specifically different contact times and catalyst activity levels. The first zone has longer contact time suitable for lighter feedstocks while the second zone has shorter contact time for heavier feedstocks. This local differentiation enables the system to handle multiple feedstock types effectively.
2Productivity
If lighter feedstocks are cracked with shorter contact time, then the productivity is high, but the conversion efficiency of lighter feedstocks is poor
Solution Approach 1:
The reactor is segmented into zones with different contact times. The first zone provides longer contact time specifically for lighter feedstocks to achieve good conversion efficiency, while the second zone provides shorter contact time for heavier feedstocks to maintain high productivity. This segmentation resolves the contradiction by allowing each feedstock type to receive the contact time it needs.
3Manufacturing precision
If a more active catalyst is used to convert lighter feedstocks, then the conversion efficiency improves, but the catalyst deactivates faster due to coke formation
Solution Approach 1:
The catalyst system is segmented into zones with different activity levels. A more active catalyst is placed in the first zone to achieve high conversion efficiency for lighter feedstocks, while a less active catalyst is used in the second zone for heavier feedstocks. This segmentation allows the more active catalyst to be used where needed without premature deactivation from processing all feedstock types.
4Manufacturing precision
If heavier feedstocks are processed with longer contact time, then the conversion efficiency improves, but the overproduction of dry gas and coke increases
Solution Approach 1:
The reactor is segmented so that heavier feedstocks are processed in the second zone with shorter contact time, which prevents excessive coke formation and dry gas overproduction. The first zone with longer contact time is reserved for lighter feedstocks where it is beneficial. This segmentation eliminates the harmful effects of using long contact time for heavier feedstocks.
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 the production of light olefins by ensuring the catalyst remains active for heavier feedstocks while minimizing coke formation and overproduction of dry gas, thus optimizing the FCC process for a broader range of hydrocarbon feedstocks.
Implementation Method 1
cracking a first hydrocarbon feedstock in the presence of a more active catalyst to produce a first effluent and a catalyst stream
Implementation Method 2
cracking at least one second hydrocarbon feedstock in the presence of the catalyst stream from the dense fluidized bed reactor
Implementation Method 3
device for the fluidized bed catalytic cracking of a hydrocarbon feedstock comprising a dense fluidized bed reactor and a transport fluidized bed reactor
Data Source
AI summary
The present invention relates to a device and to a process for the fluidized bed catalytic cracking of a hydrocarbon feedstock, in which: a first feedstock (2) is cracked in a dense fluidized bed reactor (1) in the presence of a catalyst (3) to produce a first effluent; and at least one second feedstock (10) is cracked in a transport fluidized bed reactor (4) in the presence of the catalyst (3) supplied by the dense fluidized bed reactor (1) to produce a second effluent, the second feedstock (10) being a heavier feedstock than the first feedstock (2).