Baffled Transition Zone for Gas-Solids Separation
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Solution Overview
Problem
In gas-solids reaction systems with multiple risers, there is a challenge in effectively separating gas phase conversion products from catalyst solids, leading to excess reaction and reduced efficiency due to uneven catalyst regeneration and distribution, which results in undesirable products and decreased system performance.
Innovation Solution
A method involving a transition zone with a specific configuration, including a solids inlet, outlet, and displacing gas inlet, where the displacing gas flows counter-currently to the solids flow, facilitating the separation of catalyst particles by controlling the flux, residence time, and density gradient, and using baffles to enhance the stripping efficiency of hydrocarbons from the catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stripping gas is conducted through spent catalyst in a baffled region to separate product vapors, then vapor-catalyst separation is improved, but the system cannot achieve even distribution of regenerated and non-regenerated catalyst in multiple risers
Solution Approach 1:
The system divides the catalyst flow path into multiple separate standpipes (first standpipe for non-regenerated catalyst, second standpipe for regenerated catalyst) with distinct transition zones. Each standpipe has its own displacing gas inlet positioned at specific heights to control catalyst flow and regeneration independently, enabling even distribution of catalyst types to multiple risers while maintaining effective vapor-catalyst separation in each segment.
Solution Approach 2:
A displacing gas (such as steam or nitrogen) is introduced as an intermediary substance in the transition zones to strip product vapors from catalyst particles. The displacing gas flows counter-currently to the catalyst flow, effectively removing adhered vapors without requiring direct contact between catalyst and regenerator, thus enabling controlled catalyst regeneration and distribution.
2Productivity
If catalyst flux through the transition zone is increased to improve productivity, then system throughput is improved, but stripping efficiency of hydrocarbons from catalyst decreases
Solution Approach 1:
The displacing gas inlet is positioned at a specific vertical height above the transition zone inlet, creating a vertical dimension for counter-current flow. This vertical arrangement allows the displacing gas to contact catalyst particles throughout their descent, maintaining effective stripping even at high horizontal catalyst flux rates. The height positioning creates a extended contact path without increasing the horizontal cross-sectional area.
Solution Approach 2:
The displacing gas flows continuously counter-currently to the catalyst flow throughout the transition zone, maintaining constant stripping action. The continuous counter-current flow ensures that fresh displacing gas contacts catalyst particles at all stages of their descent, maintaining high stripping efficiency even when catalyst flux is increased to improve productivity.
3Reliability
If the vertical distance D between displacing gas inlet and solids outlet is increased to improve stripping, then hydrocarbon removal is improved, but the system complexity and footprint increase
Solution Approach 1:
The system optimizes the vertical distance D as a critical parameter, positioning the displacing gas inlet at a specific height (e.g., 0.5 to 2.0 meters above the transition zone inlet) to achieve effective stripping. This parameter optimization balances stripping efficiency with compact design, avoiding excessive vertical height while ensuring sufficient contact time between displacing gas and catalyst particles for effective hydrocarbon removal.
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 method improves the separation of gas phase products from catalyst solids, ensures even distribution of regenerated and non-regenerated catalysts among multiple risers, and maintains high stripping efficiency even at high catalyst fluxes, thereby enhancing the overall reaction system efficiency and reducing coke formation and undesirable product formation.
Implementation Method 1
conducting the solids from the higher density flow through a transition zone at a transition zone solids flux of at least 100 kg/m2s in the presence of a displacing gas flowing counter-currently with respect to average solids flow
Implementation Method 2
the hydrocarbon and/or oxygenated hydrocarbon are displaced from the catalyst particles in the transition zone at a displacing efficiency of at least 50%
Implementation Method 3
the catalyst particles in the transition zone have an average catalyst density gradient of 525 kg/m3
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A gas-solids reaction system is provided for improving product recovery in a multiple reactor reaction system. The solids of the product gas-solids flows from the multiple reactors are separated out in a separation vessel having a baffled transition zone. Additional product vapor is stripped from the solids as the solids pass through the baffled transition zone. The solids are then returned to the multiple reactors.