Concentric Downflow Reactor for Light Olefins Yield
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Solution Overview
Problem
Conventional Fluid Catalytic Cracking (FCC) processes face challenges in achieving high yields of light olefins while minimizing undesired products like coke and dry gas, particularly due to limitations in catalyst contact time and reactor configurations, which affect product selectivity and conversion levels.
Innovation Solution
A catalyst system comprising 7-10 wt% ultra-stable Y zeolite, 4-8 wt% shape-selective pentasil zeolite, 2.5-5 wt% bottom-selective material, and 75-88 wt% support material is used in a concentric downflow reactor with short contact time (0.1-1 second) and specific operating conditions (550-650°C, 100-300 hr^-1 WHSV, 1-4 kg/cm^2 g pressure) to maximize light olefins yield (C2-C4) and reduce coke production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional FCC process uses upflow riser configuration with longer contact time, then catalyst and hydrocarbons are adequately contacted for conversion, but catalyst back mixing occurs which limits product selectivity
Solution Approach 1:
The patent inverts the conventional upflow riser configuration by implementing a downflow reactor configuration. This inversion eliminates catalyst back mixing while maintaining adequate contact time for conversion. The downflow configuration allows catalyst and hydrocarbons to flow downward together, preventing the back mixing that occurs in upflow systems, thereby improving product selectivity without sacrificing conversion levels.
Solution Approach 2:
The patent introduces dynamic control of contact time through the downflow configuration, where the residence time of catalyst and hydrocarbons can be precisely controlled by adjusting flow rates and reactor dimensions. This dynamic approach allows optimization of both conversion and selectivity by matching contact time to specific product goals, rather than being constrained by the static back mixing characteristics of upflow systems.
2Stability of the object's composition
If downflow reactor configuration is used to eliminate catalyst back mixing, then product selectivity improves, but uniform catalyst distribution becomes difficult to achieve at scaled-up sizes
Solution Approach 1:
The patent employs a concentric downflow reactor design where an inner reactor is nested within an outer reactor. Both reactors operate in downflow configuration and are interconnected. This nested structure facilitates uniform catalyst distribution by allowing catalyst to flow through multiple pathways and be redistributed between the inner and outer reactors, eliminating distribution problems that occur when scaling up simple downflow configurations.
Solution Approach 2:
The patent divides the downflow reactor into multiple segments (inner reactor and outer reactor) that operate in series and parallel configurations. This segmentation allows the system to maintain the benefits of downflow configuration while managing catalyst distribution through multiple zones. Each segment can be optimized independently, and the interconnected design ensures uniform catalyst distribution across the entire system even at scaled-up sizes.
3Stability of the object's composition
If contact time is reduced to maximize light olefins yield, then selectivity for light olefins improves, but conversion levels may be compromised
Solution Approach 1:
The patent utilizes the downflow configuration to decouple the relationship between contact time and conversion efficiency. By changing the flow direction and reactor hydrodynamics, the system can achieve high conversion levels at shorter contact times compared to conventional upflow systems. This parameter change in flow configuration allows optimization for light olefins selectivity without sacrificing conversion, as the downflow mechanism maintains effective catalyst-hydrocarbon contact throughout the residence time.
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
The process achieves up to 65 wt% light olefins yield with improved selectivity and reduced coke production, enhancing overall product conversion and propylene selectivity in LPG, while maintaining efficient catalyst regeneration and heat balance.
Implementation Method 1
Fluid catalytic cracking (FCC) is one of the most widely used process for the conversion of heavy hydrocarbons into gasoline, light olefins, and other valuable products
Implementation Method 2
The coked catalyst is then regenerated by burning the coke in presence of air to reactivate the catalyst
Implementation Method 3
Hot catalyst particles from the regenerator are contacted with hydrocarbon feedstocks
Implementation Method 4
The FCC process consists of two major sections namely reactor and regenerator. Hot catalyst particles from the regenerator are contacted with hydrocarbon feedstocks
Data Source
AI summary
A process for conversion of hydrocarbon feedstock into lighter olefins of C2 to C4 carbons, the process comprising of cracking the hydrocarbon feedstock in a reactor in the presence of a catalyst. The catalyst for short contact time catalytic cracking process of heavy hydrocarbons having contact time less than 1 second to produce light olefins of C2 to C4 carbon in the range of 40 to 60 wt % on fresh feed basis in a fluidized bed reactor which is concentric downflow reactor in presence of catalyst consisting of ultra-stable Y zeolite in the range of 5-10 wt %, 4 to 8 wt % of pentasil zeolite, 2.5-5 wt % of bottom selective material, 0.5-2 wt % of rare earth and 75-88 wt % of support material.