Fast Fluidized Bed Reactor Baffles for Light Olefin Yield
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Solution Overview
Problem
Conventional methods for producing light olefins from naphtha, such as steam cracking and catalytic cracking in fluidized bed reactors, suffer from low overall efficiency, high production costs, and reduced yields due to thermal cracking and backmixing, as well as the limitation of using non-zeolite catalysts due to steam usage.
Innovation Solution
A process involving a fast fluidized bed reactor coupled with a riser reactor for catalytic cracking of naphtha, utilizing a high superficial gas velocity and zeolite-based catalysts without steam, which minimizes thermal cracking and backmixing, thereby enhancing the yield of light olefins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam cracking is used to produce light olefins, then light olefins can be produced, but the overall efficiency is low and a large amount of hydrocarbons must be recycled requiring high hydrogen and energy consumption
Solution Approach 1:
The patent changes the fundamental reaction parameters by using catalytic cracking instead of thermal steam cracking, operating at lower temperatures (400-500°C vs. 750-900°C) with catalysts to achieve higher selectivity to light olefins and reduce the need for recycling hydrocarbons
Solution Approach 2:
The patent replaces the thermal cracking mechanism with a catalytic cracking mechanism using zeolite-based catalysts, substituting thermal energy-driven reactions with catalyst-mediated reactions that proceed at lower temperatures with higher selectivity
2Productivity
If catalytic cracking is used in a conventional fluidized bed reactor, then naphtha can be cracked, but back mixing occurs resulting in low light olefin yield and high methane formation
Solution Approach 1:
The patent segments the fluidized bed reactor by introducing internal loop structures and baffle plates that divide the reactor into distinct zones, preventing back mixing by creating unidirectional flow patterns while maintaining catalytic cracking efficiency
Solution Approach 2:
The patent converts the high velocity gas flow that causes back mixing into a beneficial feature by using it to enhance solids circulation and maintain high catalyst activity through continuous regeneration, while the internal loop structure directs this flow to prevent mixing of fresh and spent catalyst
3Stability of the object's composition
If conventional fluidized bed reactors are operated with low superficial gas velocities, then the reactor can operate stably, but the solid volumetric fraction is low and gas-solids contact efficiency is reduced leading to high methane formation
Solution Approach 1:
The patent implements dynamic operation by using high velocity gas flow to continuously circulate catalyst particles through the reactor and regenerator, maintaining high catalyst activity and gas-solids contact efficiency while the internal loop structure provides stability by controlling the circulation pattern
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 increases the selectivity and yield of light olefins, reduces production costs by minimizing hydrogen and energy requirements, and allows for the use of more efficient zeolite-based catalysts, improving overall production efficiency.
Implementation Method 1
contacting, in a fast fluidized bed reactor, naphtha with catalyst particles of a fast-fluidized bed having a superficial gas velocity (SGV) in a range of 1 to 6.5 m/s
Implementation Method 2
flowing effluent of the fast fluidized bed reactor to a riser reactor
Implementation Method 3
catalytically cracking naphtha in a fast fluidized bed that is coupled to a riser reactor to produce olefins
Data Source
AI summary
Systems and methods for producing light olefins wherein a feed stream comprising naphtha is flowed into a reaction unit comprising a fast fluidized bed reactor coupled to and in fluid communication with a riser reactor. The fast fluidized bed reactor comprises baffles therein to minimize backmixing therein to maximize the production of light olefins. The effluent from the fast fluidized bed reactor is further flowed to the riser reactor. The lift gas, which can comprise nitrogen, methane, flue gas, or combinations thereof, is injected in the reaction united via a sparger. Effluent of the riser reactor is separated in a product separation unit to produce a product stream comprising light olefins and spent catalyst. Spent catalyst is further stripped by a stripping gas comprising methane, nitrogen, flue gas, or combinations thereof. Stripped spent catalyst is regenerated to produce regenerated catalyst, which is subsequently flowed to the fast fluidized bed reactor.