Dense Phase Riser Reactors for Naphtha Cracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for producing light olefins, such as steam cracking and catalytic cracking of naphtha, face inefficiencies due to low selectivity, high energy consumption, and methane formation, primarily because they operate at low superficial gas velocities and use steam, which limits the use of high-efficiency zeolite-based catalysts and leads to back mixing.
Innovation Solution
The method involves catalytically cracking naphtha in dense phase riser reactors with higher superficial gas velocities and solid volumetric fractions, using a lift gas without steam to enable the use of zeolite-based catalysts and minimize back mixing, thereby increasing the yield of light olefins and reducing thermal cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam cracking or conventional catalytic cracking is used to produce light olefins, then the production process is established, but the selectivity to light olefins is limited and energy consumption is high
Solution Approach 1:
The patent changes key operating parameters including using high superficial gas velocities (0.5-2.0 m/s) in dense phase riser reactors, operating at elevated pressures (5-50 bar), and maintaining specific solid volumetric fractions (0.05-0.20). These parameter changes enable higher light olefins selectivity (40-60% based on naphtha feed) while reducing energy consumption compared to conventional steam cracking
Solution Approach 2:
The patent replaces conventional steam cracking thermal processes with catalytic cracking using zeolite-based catalysts in dense phase riser reactors. This substitution enables selective production of light olefins through catalytic mechanisms rather than purely thermal decomposition, improving both selectivity and energy efficiency
2Productivity
If conventional fluidized bed reactors are used for catalytic cracking, then the process is simple, but back mixing occurs resulting in low light olefins yield and high methane formation
Solution Approach 1:
The patent segments the conventional single-stage fluidized bed reactor into multiple dense phase riser reactors arranged in series. This segmentation creates a more controlled flow regime that minimizes back mixing, maintains narrower residence time distributions, and prevents excessive cracking that leads to methane formation while maximizing light olefins yield
Solution Approach 2:
The patent inverts the conventional approach by using dense phase flow regime with high solid concentrations instead of dilute fluidized bed regime. This inversion creates upward flowing dense slurry that maintains better contact between catalyst and naphtha while reducing back mixing and thermal cracking, thereby reducing methane formation
3Productivity
If steam is used as lift gas in fluidized bed reactors, then the process is conventional, but zeolite-based catalysts cannot be used due to de-alumination and steam causes thermal cracking
Solution Approach 1:
The patent extracts steam from the lift gas composition, using alternative gases such as nitrogen, carbon dioxide, or process gases without water vapor. This extraction prevents steam-induced de-alumination of zeolite catalysts and eliminates thermal cracking caused by steam, enabling use of high-performance zeolite-based catalysts for selective light olefins production
Solution Approach 2:
The patent creates an inert atmosphere by using steam-free lift gases (nitrogen, CO2, or dry process gases) in the dense phase riser reactors. This inert environment protects zeolite-based catalysts from de-alumination and prevents unwanted thermal cracking reactions, maintaining catalyst activity and selectivity for light olefins
4Productivity
If low solid volumetric fraction is used in fluidized bed reactors, then the gas-solids contact efficiency is limited, but the reactor operation is conventional
Solution Approach 1:
The patent merges multiple functions into the dense phase riser reactor configuration: reaction, catalyst circulation, and product separation occur in an integrated system. The high solid volumetric fraction (0.05-0.20) enables efficient gas-solids contact while the series arrangement of multiple reactors provides inherent separation stages, achieving high reaction efficiency without excessive complexity
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 the selectivity and yield of light olefins, reduces energy consumption, and allows for the effective use of zeolite-based catalysts, resulting in improved production efficiency and a higher olefins-to-aromatics ratio.
Implementation Method 1
contacting, in a plurality dense phase riser reactors, naphtha with catalyst particles under reaction conditions sufficient to produce a first product comprising one or more olefins
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
regenerating, in the catalyst 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 plurality of dense phase riser reactors, each of which is operated with a high solid volume fraction, a high superficial velocity, and minimum back mixing. The effluent stream from each 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.