Zero Benzene Aromatics Complex Recycle Loop Minimization
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Solution Overview
Problem
Current zero-benzene aromatics complexes face high costs due to large recycle loops in fractionation columns, particularly when the methyl to phenyl ratio is imbalanced, leading to low per-pass conversion of benzene and A9/A10 aromatics, resulting in high recycle rates.
Innovation Solution
Diverting benzene from the trans-alkylation unit to the toluene methylation unit and vice versa to achieve a more balanced operation, allowing benzene and A9/A10 aromatics to be converted efficiently in the trans-alkylation unit, thereby minimizing recycle loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all benzene and A9/A10 aromatics are converted to extinction in the trans-alkylation unit, then zero-benzene aromatics complex is achieved, but very large recycle loops through fractionation columns are required resulting in high costs
Solution Approach 1:
The patent segments the aromatics complex into two distinct units: a trans-alkylation unit for converting benzene and A9/A10 to trans-alkylation products, and a toluene methylation unit for converting toluene and benzene to xylenes. This segmentation allows each unit to operate with optimized feed composition and achieves zero-benzene output without requiring large recycle loops through fractionation columns
Solution Approach 2:
The patent changes the operational parameters by adjusting the feed distribution between units. Specifically, it optimizes the methyl to phenyl ratio fed to the trans-alkylation unit and controls the extent of benzene conversion, allowing high per-pass conversion without requiring extinction-level recycle loops, thereby reducing device complexity while maintaining reliability
2Quantity of substance
If the methyl to phenyl ratio in feed is significantly below 1.5, then benzene and toluene are produced or brought into the complex, but low per-pass conversion of benzene in trans-alkylation unit results in very high benzene recycle
Solution Approach 1:
The patent makes the trans-alkylation unit multi-functional by having it perform both trans-alkylation reactions (converting benzene and A9/A10 to xylenes) and methylation reactions (converting toluene to xylenes). This allows the unit to handle imbalanced feed compositions with low methyl to phenyl ratios efficiently, achieving high per-pass conversion of both benzene and toluene without requiring large recycle loops
Solution Approach 2:
The patent dynamically adjusts the feed distribution and operational parameters based on the incoming feed composition. When methyl to phenyl ratio is below 1.5, the system optimizes the split of feed between units and adjusts conversion levels to maximize per-pass conversion while maintaining flexibility to handle varying feed conditions
3Quantity of substance
If the methyl to phenyl ratio in feed is significantly above 1.5, then extra A9+ materials are produced or brought into the complex, but low per-pass conversion of A9+ in trans-alkylation unit results in very high A9+ recycle
Solution Approach 1:
The patent segments the handling of A9+ materials by directing them preferentially to the toluene methylation unit rather than the trans-alkylation unit. This segmentation allows the trans-alkylation unit to focus on benzene and A9/A10 conversion while the methylation unit handles A9+ conversion, achieving high per-pass conversion of A9+ without requiring large recycle loops
Solution Approach 2:
The patent uses the toluene methylation unit as an intermediary to handle A9+ materials. Instead of requiring the trans-alkylation unit to achieve high conversion of all aromatics including A9+, the system uses the methylation unit as an intermediate step that converts A9+ to xylenes, thereby achieving high overall conversion without large recycle loops
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 reduces the benzene and A9/A10 recycle rates by optimizing the methylation and trans-alkylation unit operations, enhancing per-pass conversion and reducing operational costs.
Implementation Method 1
The trans-alkylation unit converts benzene and A9/A10 aromatics to a trans-alkylation product comprising benzene through A11+ aromatics with toluene and xylenes as the focus
Implementation Method 2
The toluene methylation unit converts toluene and any benzene to a methylation product stream
Data Source
AI summary
The present invention relates to minimizing benzene, toluene, and an A9/A10 recycle loop in a zero benzene aromatics complex. More specifically, the present invention relates to a minimizing benzene, toluene, and an A9/A10 recycle loop in a zero benzene aromatics complex wherein the aromatic feed has a low methyl to phenyl ratio, and where the aromatic feed has a high methyl to phenyl ratio.