Two-Stage C7 Isomerization for High-Octane Gasoline
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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 gasoline production, leading to high operating costs and reduced profitability due to the need for large recycle streams and limited on-stream flexibility.
Innovation Solution
The implementation of a two-stage C7 isomerization zone process, where the first stage is optimized for multi-branched C7 paraffin formation at lower temperatures and the second stage for cyclopentane formation at higher temperatures, eliminating the need for a large recycle stream and enhancing molecular management, thereby improving the overall process efficiency.
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 the 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 optimizes for multi-branched C7 paraffin formation at lower temperatures, while the second zone maximizes cyclopentane formation at higher temperatures. This segmentation eliminates the need for large recycle streams and improves both octane and process flexibility.
Solution Approach 2:
Each isomerization zone is optimized with specific local conditions: the first zone operates at lower temperatures favoring multi-branched C7 paraffins, while the second zone operates at higher temperatures favoring cyclopentanes. This local optimization of conditions in different zones achieves high octane without requiring large recycle streams.
2Object-generated harmful factors
If C7 is removed from the feed to the catalytic reforming zone to minimize aromatics production, then the amount of aromatics produced is reduced, but the 95 RONC gasoline production is limited due to low blending octanes
Solution Approach 1:
The process changes the chemical parameters of C7 hydrocarbons through two-stage isomerization, transforming them from low-octane straight-chain paraffins into high-octane multi-branched paraffins and cyclopentanes. This parameter change allows C7 stream to be blended into 95 RONC gasoline while minimizing aromatics production.
3Manufacturing precision
If a deisoheptanizer column is used to produce overhead and side cut streams to maximize octane, then the octane is improved, but the operating costs and capital costs increase
Solution Approach 1:
The process segments the isomerization function into two zones, eliminating the need for a deisoheptanizer column with its complex overhead and side cut streams. The two-zone configuration achieves the same octane maximization goal with simpler equipment and lower operating costs.
Solution Approach 2:
The deisoheptanizer column, which causes high operating and capital costs, is completely removed from the process. The two-stage isomerization zones directly produce the required high-octane components without needing this intermediate separation step.
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 results in significant savings in operating and capital costs, increased gasoline yield, and enhanced flexibility, achieving higher octane barrels and improved compliance with Euro-V specifications.
Implementation Method 1
The first C7 isomerization zone is designed to isomerize C7 paraffins. The first C7 isomerization zone is optimized to increase the isomerization of C7 paraffins and increase the C5+ retention.
Implementation Method 2
The second C7 isomerization zone is designed to maximize the isomerization of C7 cycloalkanes to higher octane cycloalkanes. The second C7 isomerization zone is optimized to maximize the isomerization of C7 cycloalkanes by operating at higher temperature.
Implementation Method 3
The product from the first C7 isomerization zone is sent to a deisoheptanizer column in order to separate a C7 isoparaffin-containing stream as an overhead and a C7 cycloalkane-containing stream as a bottom stream.
Data Source
AI summary
An integrated process for production of gasoline has been described. The process includes a C5-C6 isomerization zone, two C7 isomerization zones separate by a deisoheptanizer, and a reforming zone. The use of two C7 isomerization zones eliminates the need for the large recycle stream from the deisoheptanizer. The low temperature in first C7 isomerization zone favors the formation of multi-branched C7 paraffins and cyclohexanes and maximizes C5+ yield. The separation between paraffin and cycloalkane in deisoheptanizer becomes easier due to conversion of cycloalkanes to cyclohexanes in the first C7 isomerization zone. Further, the high temperature in second C7 isomerization zone favors the formation of higher octane cyclopentanes over cyclohexanes. An aromatic-containing stream can be introduced to second C7 isomerization zone. The saturation of the aromatics in the second C7 isomerization zone provides heat that increases the reactor outlet temperature in the isomerization reactors to favor cyclopentanes.