Olefin Oligomerization for FCC Separation Bottlenecks
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Solution Overview
Problem
The challenge in the field of fluid catalytic cracking (FCC) is the difficulty in separating olefins from paraffins in product streams, particularly those with a wide range of boiling points, which hinders the efficient recycling of olefins to increase propylene production.
Innovation Solution
The proposed solution involves an apparatus with a process fractionation column to separate C3-rich and C5-rich streams, followed by conversion zones that convert olefins to higher molecular weight compounds, allowing for easier separation from unconverted paraffins, and recycling these compounds back to the FCC reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If olefins are recycled to increase propylene production, then propylene yield is improved, but separation of olefins from paraffins becomes more difficult due to concentration of refractory paraffins in the recycle stream
Solution Approach 1:
The patent applies preliminary action by converting olefins to higher molecular weight compounds (oligomers) before the separation step. The conversion zone transforms C4-C7 olefins into heavier oligomeric olefins that can be more easily separated from paraffins in the fractionation column, thus preparing the material in advance to facilitate subsequent separation and recycling operations
Solution Approach 2:
The patent changes the molecular weight parameter of olefins by converting them to higher molecular weight compounds through oligomerization. This parameter change transforms the olefins into a form that is more easily separable from paraffins based on boiling point differences, thereby resolving the separation difficulty while maintaining productivity
2Ease of manufacture
If a significant purge is implemented to handle refractory paraffin concentration, then separation feasibility is improved, but olefin loss increases
Solution Approach 1:
The patent applies discarding and recovering by selectively converting olefins to higher molecular weight compounds that can be separated and recovered in the recycle stream. The fractionation column separates the oligomeric olefins from paraffins, allowing the olefin-derived compounds to be recovered and recycled back to the FCC reactor, thus minimizing olefin loss while maintaining separation feasibility
3Ease of operation
If a large recycle flow rate is used to handle refractory paraffins, then separation operability is improved, but energy consumption increases
Solution Approach 1:
The patent changes the boiling point parameter of olefins by converting them to higher molecular weight compounds. This parameter change creates a larger boiling point difference between the olefin-derived oligomers and paraffins, improving separability in the fractionation column and reducing the need for large recycle flow rates, thereby decreasing energy consumption
4Ease of manufacture
If olefins are converted to higher molecular weight compounds, then ease of separation from paraffins is improved, but process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the conversion and separation process into distinct zones: a conversion zone for oligomerization, a fractionation column for separation, and a recycle system. This segmentation allows each unit to perform its specific function efficiently, with the conversion zone producing separable oligomers and the fractionation column separating them from paraffins, thus improving separation ease while managing process complexity through modular design
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 enables effective separation of olefins from paraffins, facilitating their recycling and enhancing propylene production by converting them into heavier compounds that can be easily distinguished and reused in the FCC process.
Implementation Method 1
a process fractionation column for separating an overhead stream comprising a C3-rich overhead stream from a C5-rich bottoms stream
Implementation Method 2
An aromatic alkylation reactor communicates with a bottoms line of the process fractionation column for alkylating olefins in the C5-rich bottoms stream with aromatics
Implementation Method 3
The oligomerization of olefins over heterogeneous catalyst to heavier olefins for making motor fuels is a known technology
Implementation Method 4
It is also known to alkylate olefins with paraffins over homogeneous acid catalyst to make motor fuels
Implementation Method 5
A product column communicates with the aromatic alkylation reactor for separating alkylaromatics from unreacted compounds from the C5-rich bottoms stream
Implementation Method 6
Fluid catalytic cracking (FCC) is a catalytic hydrocarbon conversion process accomplished by contacting heavier hydrocarbons in a fluidized reaction zone with a catalytic particulate material
Implementation Method 7
A high temperature regeneration with oxygen within a regeneration zone burns coke from the spent catalyst which may have been stripped
Data Source
AI summary
The apparatus converts FCC olefins to heavier compounds. The heavier compounds are more easily separated from the unconverted paraffins. The heavier compounds can be recycled to an FCC unit or delivered to a separate FCC unit. Suitable conversion zones are oligomerization and aromatic alkylation zones.