FCC Light Olefin Recovery via Segmented Absorption
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Solution Overview
Problem
Traditional FCC gas concentration units face challenges in effectively recovering ethylene due to the loss of valued ethylene material during the purging of ethane, which is necessary to remove undesired ethane from the system.
Innovation Solution
A process involving a hydrocarbon cracking catalyst composition with a large pore molecular sieve and a zeolite with no greater than medium pore size, used in a fluidized reactor to produce a hydrocarbon effluent, which is then separated and processed through absorption zones to recover light olefins efficiently, minimizing ethylene loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethane is purged from the system to remove undesired ethane, then ethane removal is achieved, but valued ethylene material is lost
Solution Approach 1:
The patent segments the absorption process into multiple absorption zones with different solvent conditions. The first absorption zone uses a C4-rich solvent to selectively absorb propylene while leaving ethylene in the gas phase. The second absorption zone then handles ethylene absorption with a different solvent configuration. This segmentation allows selective recovery of different olefins without purging ethylene with ethane.
Solution Approach 2:
Different absorption solvents with specific local qualities are applied in different zones. The first absorption zone uses a C4-rich solvent that has high affinity for propylene but low affinity for ethylene. The second zone uses a different solvent configuration optimized for ethylene. This local quality differentiation enables selective absorption of each olefin type without cross-contamination or co-loss.
2Productivity
If traditional absorption-based FCC gas concentration units are used, then propylene recovery is effective, but ethylene recovery is problematic due to purging requirements
Solution Approach 1:
The absorption system is divided into multiple independent absorption zones, each optimized for recovering a specific light olefin. The first zone recovers propylene using a C4-rich solvent, while the second zone recovers ethylene using a different solvent configuration. This segmentation allows each zone to operate independently with solvent conditions optimized for its target olefin, eliminating the need to purge ethylene to recover propylene.
Solution Approach 2:
The multi-zone absorption system serves multiple functions: it recovers both propylene and ethylene in separate zones, and each zone can be independently optimized for its specific olefin. The system universally handles multiple light olefin recovery tasks that a single traditional absorption zone cannot accomplish without sacrificing ethylene.
3Productivity
If a blended catalyst comprising regenerated catalyst and coked catalyst is used, then light olefin production is increased, but the complexity of catalyst management increases
Solution Approach 1:
The patent merges regenerated catalyst and coked catalyst into a blended catalyst system that is circulated together through the FCC unit. This blending allows the fresh activity of regenerated catalyst to compensate for the deactivation of coked catalyst, maintaining high light olefin production. The catalysts are combined in a common circulation system, simplifying management compared to separate handling while achieving synergistic performance.
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 recovery of light olefins, such as ethylene and propylene, by optimizing the catalyst composition and absorption-based product recovery, reducing the loss of ethylene and improving the efficiency of the FCC process.
Implementation Method 1
Contact of the oil with the fluidized material catalyzes the cracking reaction
Implementation Method 2
The catalyst is transported in a fluid-like manner by transmitting a gas or vapor through the catalyst at sufficient velocity to produce a desired regime of fluid transport
Implementation Method 3
spent catalyst is traditionally transferred to a stripper that removes adsorbed hydrocarbons and gases from catalyst and then to a regenerator for the purpose of removing the coke by oxidation with an oxygen-containing gas
Implementation Method 4
The separator vapor stream is contacted with a first absorption solvent in an absorption zone to remove C3+ hydrocarbons therefrom
Implementation Method 5
C1- materials are stripped from the at least one separator liquid stream in a stripper section
Data Source
AI summary
Processing schemes and arrangements are provided arrangements are provided for the processing a heavy hydrocarbon feedstock via hydrocarbon cracking processing with selected hydrocarbon fractions being obtained via absorption-based product recovery while minimizing or avoiding loss of light olefins via system purging.