Integrated Stabilizer for Two-Stage C7 Isomerization
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Solution Overview
Problem
Hydrocracker-based refineries face challenges in meeting Euro-V gasoline standards for aromatics specifications while maximizing 95 RONC without a heavy naphtha export stream, leading to increased operating costs and reduced profitability.
Innovation Solution
Implementing a process with two C7 isomerization zones, where the first zone is optimized for multi-branched C7 paraffin formation at lower temperatures and the second zone for cyclopentane formation at higher temperatures, eliminating the need for a large recycle stream and enhancing molecular management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single stage C7 isomerization zone with a large recycle stream is used to maximize octane, then the octane of the isomerate is improved, but operating costs increase and on-stream flexibility decreases
Solution Approach 1:
The single stage C7 isomerization zone is divided into two separate isomerization zones with different functions: the first zone converts n-heptane to multi-branched C7 paraffins, while the second zone converts cycloheptanes to methylcyclohexanes. This segmentation allows each zone to be optimized for its specific function, eliminating the need for large recycle streams and reducing operating costs while maintaining high octane production.
2Device complexity
If a single stage C7 isomerization zone is used, then the process is simpler, but on-stream flexibility decreases
Solution Approach 1:
The isomerization process is segmented into two independent zones that can be operated flexibly. The first zone handles n-heptane isomerization while the second zone handles cycloheptane isomerization. This segmentation provides on-stream flexibility by allowing independent operation, maintenance, or optimization of each zone based on feed composition and product requirements.
3Object-generated harmful factors
If C7 is removed from the catalytic reforming zone feed to minimize aromatics production, then aromatics concentration is reduced, but the low blending octanes of C7 components reduce gasoline quality
Solution Approach 1:
The C7 stream undergoes preliminary isomerization treatment in two zones before being blended into the gasoline pool. The first zone converts n-heptane to high-octane multi-branched paraffins, and the second zone converts cycloheptanes to methylcyclohexanes. This preliminary action ensures that when C7 components are blended into gasoline, they contribute high octane values rather than low blending octanes, thus maintaining gasoline quality while minimizing aromatics production.
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 configuration reduces operating and capital costs by 57% and 11%, respectively, increases octane barrels by 4%, and enhances operational flexibility while meeting stringent gasoline specifications.
Implementation Method 1
The first C7 isomerization zone is designed to isomerize C7 paraffins. The product from the first C7 isomerization zone is sent to a deisoheptanizer column
Implementation Method 2
The second C7 isomerization zone is designed to maximize the isomerization of C7 cycloalkanes to higher octane cycloalkanes
Implementation Method 3
a deisoheptanizer (DIHP) column is used to produce an overhead stream, a side cut stream, and a bottom stream
Data Source
AI summary
Improved processes for production of gasoline with 95 RONC including a C5-C6 isomerization zone, two C7 isomerization zones, and a reforming zone are described. The first and second C7 isomerization zones share a common stabilizer which strips off the chlorides and removes the light ends. The capital and operating costs of the processes are reduced through the elimination of one of the stabilizer columns and the associated condenser, receiver, trim cooler, and reboiler. The processes improve the RONC of the C7 isomerization product because unconverted methylcyclohexane is recycled back to the second C7 isomerization zone to be converted into dimethylcyclopentane.