Hydrocarbon Dehydrogenation Cyclone Separation Before Quenching
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Solution Overview
Problem
Existing dehydrogenation processes face challenges in efficiently separating catalyst particles from conversion effluents while minimizing thermal reactions and catalyst-induced reverse dehydrogenation, leading to reduced product yield and increased energy consumption.
Innovation Solution
A process involving multiple cyclone stages followed by quench towers with specific quench media to separate and recover catalyst particles, including recycling of quench media, effectively isolating dehydrogenated hydrocarbons and coked catalysts, and maintaining catalyst activity through reduction steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of cyclone stages is increased to improve catalyst particle separation, then catalyst recovery is improved, but residence time at high temperatures increases causing further thermal reactions that reduce product yield
Solution Approach 1:
The separation process is divided into multiple sequential cyclone stages, where each stage removes a portion of catalyst particles. This segmentation allows for progressive separation without requiring excessive residence time in any single stage, balancing separation efficiency with product yield preservation.
Solution Approach 2:
Catalyst particles are extracted from the conversion effluent through cyclone separation before the effluent undergoes further thermal processing. By removing catalyst particles early in the process, subsequent thermal reactions are minimized, preserving product yield while achieving adequate separation.
2Reliability
If catalyst particles are not adequately separated from the gaseous product stream, then reverse dehydrogenation occurs during quenching, but increasing separation intensity requires more cyclone stages which increases residence time and reduces yield
Solution Approach 1:
Cyclone separation stages are positioned before the quenching step to remove catalyst particles from the hot effluent. This preliminary action prevents catalyst-induced reverse dehydrogenation during quenching, eliminating the need for intensive post-quench separation while preserving product yield.
Solution Approach 2:
The cyclone separation system acts as an intermediary between the dehydrogenation reactor and the quenching section. It provides a transition zone where catalyst particles are removed from the gas stream, preventing direct contact between catalyst and cooled hydrocarbons that would cause reverse reactions.
3Reliability
If multiple cyclone stages are used to improve separation, then catalyst recovery is enhanced, but the conversion effluent remains at high temperatures longer causing unwanted thermal reactions
Solution Approach 1:
The system dynamically balances separation intensity with temperature management by using a optimized number of cyclone stages. Each stage is designed to remove a specific fraction of catalyst particles while minimizing residence time, allowing the effluent to be cooled promptly after separation to prevent thermal degradation.
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
Enhances catalyst recovery and product yield by reducing thermal reactions and catalyst entrapment, improving selectivity and activity, and optimizing energy usage in the dehydrogenation process.
Implementation Method 1
The conversion effluent is passed through one or more cyclone separators to separate a first stream rich in the coked catalyst particles and lean in the one or more dehydrogenated hydrocarbons and a second stream rich in the one or more dehydrogenated hydrocarbons and containing entrained coked catalyst particles
Implementation Method 2
The second stream is contacted with a first quench medium to produce a cooled second stream. The cooled second stream is contacted with a second quench medium within a quench tower
Implementation Method 3
recovering a gaseous stream that can include the one or more dehydrogenated hydrocarbons, a condensed first quench medium stream, and a slurry stream that can include at least a portion of the second quench medium in a liquid phase and the entrained coked catalyst particles from the quench tower
Data Source
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AI summary
A hydrocarbon can be contacted with dehydrogenation catalyst particles to produce an effluent that can include coked catalyst particles and dehydrogenated hydrocarbon(s). A first stream rich in coked catalyst particles and a second stream rich in dehydrogenated hydrocarbon(s) and containing entrained catalyst particles can be separated from the effluent. The second stream can be contacted with a first quench medium to produce a cooled stream. The cooled stream can be contacted with a second quench medium within a quench tower. A gaseous stream that includes the dehydrogenated hydrocarbon(s), a first quench medium stream, and a slurry stream that includes the second quench medium and the entrained catalyst particles can be separated from the tower. The first quench medium can be recycled. The entrained catalyst particles can be separated from the slurry to provide recovered second quench medium and recovered entrained catalyst particles. The recovered second quench medium can be recycled.