Zero Benzene Aromatics Complex Recycle Loop Minimization
Find Innovative SolutionsGenerate Solutions
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 below or above 1.5, 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 balance methylation and trans-alkylation operations, allowing for efficient conversion of benzene, toluene, and A9/A10 aromatics, minimizing recycle loops by optimizing the flow through benzene and toluene columns and fractionation zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all toluene is converted in toluene methylation unit and all benzene and A9/A10 aromatics are converted in trans-alkylation unit, then zero benzene aromatics production is achieved, but very large recycle loops through fractionation columns are required resulting in high costs
Solution Approach 1:
The patent extracts benzene from the trans-alkylation unit and redirects it to the toluene methylation unit. This separation allows the trans-alkylation unit to focus on converting A9/A10 aromatics while the toluene methylation unit handles both toluene and benzene conversion, eliminating the need for large recycle loops through fractionation columns.
Solution Approach 2:
The toluene methylation unit is made multi-functional by enabling it to convert both toluene and benzene. This universal approach allows one unit to handle multiple conversion tasks, reducing the dependency on large recycle loops and fractionation columns while achieving zero benzene aromatics production.
2Productivity
If methyl to phenyl ratio in feed is significantly below 1.5, then low per-pass conversion of benzene occurs in trans-alkylation unit, but very high benzene recycle is required
Solution Approach 1:
Benzene is extracted from the trans-alkylation unit feed and redirected to the toluene methylation unit. This ensures that benzene is converted in the methylation unit where it can achieve high per-pass conversion regardless of the overall feed's methyl to phenyl ratio, eliminating the need for high benzene recycle rates.
Solution Approach 2:
The patent changes the operational parameters of the toluene methylation unit to accommodate benzene conversion. By adjusting the unit to handle both toluene and benzene with appropriate catalyst and conditions, high per-pass conversion is achieved for both components without requiring high recycle rates.
3Productivity
If methyl to phenyl ratio in feed is significantly above 1.5, then low per-pass conversion of A9+ occurs in trans-alkylation unit, but very high A9+ recycle is required
Solution Approach 1:
Toluene is extracted from the toluene methylation unit feed and redirected to the trans-alkylation unit. This ensures that toluene is available in sufficient quantities in the trans-alkylation unit to react with A9/A10 aromatics, achieving high per-pass conversion of A9+ without requiring high recycle rates.
Solution Approach 2:
The patent adjusts the feed composition to the trans-alkylation unit by adding toluene from the methylation unit. This parameter change ensures the methyl to phenyl ratio in the trans-alkylation unit is optimized for high per-pass conversion of A9/A10 aromatics regardless of the overall feed ratio.
4Productivity
If extra benzene is present in feed (from external feed or integrated with reforming or dehydrocyclodimerization), then efficient and balanced methylation vs. trans-alkylation operations are needed, but current scheme requires very large recycle loops
Solution Approach 1:
The toluene methylation unit is made universal to handle both toluene and benzene conversion. This allows the unit to efficiently process extra benzene from external feeds or integrated units without requiring large recycle loops, as the methylation unit can directly convert the benzene to xylenes.
Solution Approach 2:
Extra benzene is extracted from the overall process feed and directed to the toluene methylation unit for conversion. This prevents the benzene from accumulating and requiring large recycle loops through fractionation columns, while maintaining efficient conversion.
5Productivity
If extra A9/A10 material is present in feed or produced in aromatics complex units, then efficient and balanced methylation vs. trans-alkylation operations are needed, but current scheme requires very large recycle loops
Solution Approach 1:
A9/A10 aromatics are extracted from the overall process and directed to the trans-alkylation unit where they react with toluene (supplied from the methylation unit) to form xylenes. This direct conversion pathway eliminates the need for large recycle loops through fractionation columns.
Solution Approach 2:
The patent optimizes the feed composition to the trans-alkylation unit by controlling the toluene supply from the methylation unit. This ensures the methyl to phenyl ratio is optimized for high per-pass conversion of A9/A10 aromatics, reducing recycle requirements.
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 benzene and A9/A10 recycle rates, enhancing per-pass conversion and operational efficiency, thereby lowering costs and improving the overall process balance in aromatics complexes.
Implementation Method 1
passing an aromatics stream having a high methyl to phenyl ratio to a benzene column to produce a benzene column overhead stream and a benzene column bottoms stream
Implementation Method 2
passing the benzene column bottoms stream to a toluene column which produces a toluene column overhead stream and a toluene column bottoms stream
Implementation Method 3
passing the toluene column bottoms stream to a fractionation zone to produce an overhead stream, a bottoms stream, and a middle boiling fraction
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.