Dense Phase Riser Reactor for Naphtha Cracking Olefins Yield
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Solution Overview
Problem
Conventional methods for producing light olefins, such as steam cracking and catalytic cracking in fluidized bed reactors, face inefficiencies due to low selectivity, high energy consumption, and methane formation, leading to increased production costs and reduced yield.
Innovation Solution
The use of a dense phase riser reactor for catalytic cracking of naphtha, which allows for higher superficial gas velocities, reduced thermal cracking, and the use of zeolite-based catalysts without steam, minimizing back mixing and enhancing the olefins to aromatics ratio.
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 selectivity of naphtha to light olefins is limited and a large amount of hydrocarbons must be recycled
Solution Approach 1:
The patent changes the fundamental reaction parameters by switching from steam cracking to catalytic cracking using zeolite catalysts. This changes the reaction mechanism and product distribution, achieving higher light olefins yield (40-60% of naphtha feed) while reducing the need for hydrocarbon recycling through the hydrogenation unit.
2Productivity
If conventional fluidized bed reactor is used for catalytic cracking, then naphtha can be cracked, but back mixing occurs and light olefins yield is relatively low
Solution Approach 1:
The patent segments the fluidized bed reactor into two distinct zones: a dense phase reaction zone at the bottom where catalytic cracking occurs with controlled residence time, and a dilute phase separation zone at the top where products are separated from catalyst. This segmentation eliminates back mixing while maintaining catalytic cracking efficiency, achieving higher light olefins yield with narrower residence time distribution.
3Productivity
If conventional fluidized bed reactor is used, then catalytic cracking can be performed, but solid volumetric fraction is low and gas-solids contact efficiency is limited
Solution Approach 1:
The patent employs dynamic control of gas velocity to create different flow regimes in different reactor zones. In the dense phase zone, gas velocity is controlled to maintain high solid volumetric fraction (0.3-0.6) for efficient gas-solids contact. In the dilute phase zone, higher gas velocity facilitates product-catalyst separation. This dynamic approach maximizes reaction efficiency while enabling effective separation.
4Productivity
If zeolite based catalyst is used with steam, then catalytic cracking efficiency is high, but de-alumination occurs reducing catalyst performance
Solution Approach 1:
The patent extracts the harmful steam component from the system by using nitrogen or carbon dioxide as the fluidizing and stripping gas instead of steam. This allows zeolite-based catalysts to maintain high catalytic cracking efficiency for light olefins production without suffering from steam-induced de-alumination, thereby preserving catalyst stability and performance over time.
5Productivity
If thermal cracking occurs during naphtha cracking, then cracking reaction proceeds, but methane formation increases reducing olefins selectivity
Solution Approach 1:
The patent introduces zeolite catalysts as an intermediary that mediates the cracking reaction. Instead of direct thermal cracking that produces excessive methane, the zeolite catalyst provides a controlled catalytic pathway that achieves high cracking rates while selectively producing light olefins (ethylene, propylene, butenes) with minimal methane formation, thereby improving olefins selectivity.
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 yield and selectivity of light olefins, reduces production costs, and improves the efficiency of the process by maintaining high solid volumetric fractions and using zeolite catalysts effectively.
Implementation Method 1
The superficial gas velocity in the dense phase riser reactor is significantly higher than the conventional methods. This can be beneficial for at least providing high solid volumetric fraction in the dense phase riser reactor
Implementation Method 2
flowing a mixture of the first product, the catalyst particles, and unreacted naphtha to a cyclone system disposed in a secondary reactor
Implementation Method 3
contacting, in a dense phase riser reactor, naphtha with catalyst particles under reaction conditions sufficient to produce a first product comprising one or more olefins
Implementation Method 4
catalytic cracking of naphtha in a conventional fluidized bed reactor
Implementation Method 5
regenerating, in the regenerator, the stripped catalyst particles
Data Source
AI summary
Systems and methods for producing light olefins via catalytic cracking of naphtha are disclosed. A naphtha feed stream and lift gas stream are fed into a dense phase riser reactor operated with a high solid volume fraction, a high superficial velocity, minimum back mixing. The effluent stream from the dense phase riser reactor is further separated, in a secondary reactor, to form a gaseous product stream and a catalyst stream. The catalyst stream is stripped to remove the hydrocarbons adsorbed on the catalyst particles. The stripped catalyst is regenerated in a regenerator.